ALBERT

Description: Die design is one of the key technologies for hot stamping technology, and the quality of the forming part is influenced by the structure design of the cooling system parameters. Cooling pipe size, distance between cooling pipes, and depth from cooling pipe to die surface are the most important structure parameters, and the final microstructure and property of the forming parts are influenced directly by these structural parameters. In this article, the simplified model of hot stamping die was established, and the hot stamping die cooling structural parameters were analyzed by heat transfer theory. The mathematical model of the structure parameters was set up and verified by simulation and experiment. It was shown that the mathematical model of the hot stamping die cooling structural parameters met the cooling requirements; the hot stamping parts achieved the need of the martensite structure.

Description: A common approach to the construction of surface-covering impact paths for computer-controlled manufacturing systems is to take a finite family of quasi-parallel offset curves of a seed curve on the workpiece surface. A possibility to get such curves is to consider the distance function of the seed curve in order to take the isolines of a finite sequence of increasing values. Besides several advantages, distance functions suffer from two problems which have an influence on the usefulness of the resulting curves: locations with discontinuous derivatives and local extrema. Optimization-based approaches for contour-parallel and direction-parallel offset curves, respectively, are presented to reduce these difficulties. For the contour-parallel case, the curvature, the mutual distance, and the topology of the isolines are optimized over a finite-dimensional family of scalar functions derived from the distance function of the contour. In the direction-parallel case, objectives including the number, the normal, and the geodesic curvature of isolines are optimized over the distance functions of a finite-dimensional family of seed curves. Algorithms to solve these optimization problems on triangular meshes are proposed and employed to demonstrate the usefulness of the methods.

Description: The biocompatibility of an implant material depends on the bulk physical properties as well as on the surface properties. Titanium alloy Ti6Al4V is a very popular biological implant material for its bulk physical properties resembling those of natural bone. It is possible to modify the surface properties of Ti6Al4V by laser irradiation. In the current study, using continuous wave fibre laser, grooves of different depths and widths have been created by varying laser power and scan speed. Laser frequency and duty cycle were varied to alter the inside surface topographies of the microgrooves. The surface wettability and the protein adsorption on the surface were found to be dependent on the microtexture parameters. To understand the effect of this type of texturing on the cell behaviour, MG63 cells have been cultured on the sample surfaces, and the result was studied after 3 and 5 days of cell culture. Surface features dimensionally closer to the cell dimensions are able to positively affect the viability and spreading of MG63 cells, as seen from this study.

Description: Preventive evaluation of costs is strategic for the whole manufacturing industry and especially for companies whose manufacturing technology is based on expensive machinery, tools and fixtures, such as injection moulding of aluminium. Preventive evaluation of production costs and time is even more relevant for the mould producer, in order to quickly prepare commercial offers with an acceptable degree of accuracy. In this paper, the application of a parametric approach for the evaluation of the labour content in the production of mould for injection moulding of aluminium automotive components is presented. The approach is based on simple geometrical features of the part to be produced derived from their 3D model using the basic tools of CAD systems. The data acquired from a specialized mould production company was analysed by factor analysis in order to determine the structure of the labour content and then parametric modelling was applied. The results evidenced an acceptable degree of accuracy of the estimate combined with an exceptional ease of application.

Description: The results of mathematical simulation have been carried out for the pattern of working medium motion providing the technological process of finishing–grinding treatment in an oscillating reservoir. With use of physics laws, it is ascertained and grounded that the flow of granules at the plane wall of reservoir is travelling oppositely to the source of vibrations, whereas the granules are drifting on the cycloid–trochoid trajectories from the wall of reservoir, where the looped displacement is maximal, to the center of reservoir in which the shift of granules is reduced to minimum because of damping and dissipation effect. The received theoretical regulations have a fundamental nature and can be used at the account of technological parameters of designed vibration machines.

Description: To be much closer to the cutting process and the actual cutting phenomenon, a new tool-chip friction model proposed in this paper takes account of the thickness of the material transfer layer of the chip which is ignored by most existing friction models. The material transfer layer, in which the chip material nearly stagnates on the tool rake face during machining, is located between the tool-chip contacting interface and the cutting interface in the secondary shear zone. Furthermore, the proposed model also contains the sticking, the transition, and the sliding friction regions along the tool-chip contacting surface and comprehensively depicts every region’s physical performance during dry machining. The global and the local friction characteristics between the tool and the chip are described based on coupled thermomechanical analytical method. Numerical results solved by the proposed model are compared with the existing experimental and simulated data in available literature. The results show that the proposed model was in good agreement with the experiments. The model provides an analytical method to predict friction characteristics conveniently and efficiently on the tool rake face during dry machining.

Description: This paper develops an optimization model to investigate the lengths of the optimal burn-in and warranty period, so that the mean of total product servicing cost is minimised. It is assumed that the cost of a minimal repair to a component at age t is a continuous non-decreasing function of t . Moreover, we model the customer dissatisfaction with product failures after the warranty within the product useful lifetime by introducing a post-warranty failure penalty cost to the manufacturer. The properties of the optimal burn-in time and optimal warranty policy are also analysed. Finally, under different product lifetime distributions, numerical examples and sensitivity analysis with respects to the values of the model parameters are provided.

Description: Fringe projection is a versatile method for mapping the surface topography. In this paper, it is used to measure the deformation of steel plates under static penetration. Here, the surface shape changes continuously. Therefore, it is important to minimize the registration time. To achieve this, we apply a method of fringe location with subpixel accuracy that requires only a single exposure for each registration. This is in contrast to phase shifting techniques that require at least three separate exposures.

Description: Since the use of feature-based computer-aided systems became common in production, feature recognition has been a primary method to obtain features that contain specific engineering significance. In feature recognition, engineering significance is extracted from low-level elements and encapsulated into features to facilitate the various engineering tasks including process planning, manufacture and inspection. Due to the various classifications of features and their versatile application areas, there have been many different feature recognition approaches. These feature recognition methods are typically based on the part design models from computer-aided design systems. In this research, a new feature recognition method from computer numerical control (CNC) part programs for milling components is proposed. This approach uses feature recognition algorithms to integrate CNC part programs through the analysis of tool changes, spindle speeds, feed rates, raw material, tool geometry and tool paths to identify the manufacturing process plan. It has a major influence with the ability to extract process knowledge from the shop floor and represent it into a manufacturing feature-level data. This paper focuses on the recognition of 2½D features, but it can be extended to more complex features. Case studies are used to validate the use of the proposed method on typical milling features. Two sample parts are used to illustrate the efficacy and efficiency of the method. In addition, the proposed method is compared against traditional feature recognition techniques, and issues particular to feature recognition from part programs are discussed.

Description: Springback is the most common defect in sheet metal forming, especially for the advanced high-strength steel (AHSS) parts. The compensation method is an effective way to overcome this defect by modifying the die-face. A new geometrical springback compensation algorithm based on the advanced displacement adjustment (DA) method is proposed in this paper for automobile AHSS parts. The die-face is reconstructed by the non-uniform rational B-spline surface with the advantage of UV curves; furthermore, the continuity and topology of the die-face are also studied. The high-quality geometry compensation die-face obtained from this algorithm can be directly applied to actual machining. To reduce the time and cost of the die manufacturing, this algorithm is seamlessly integrated into the CATIA platform. A new compensation user-defined feature is created, which can meet the need for iterative compensation and parametric association. At the end of this paper, two engineering examples of AHSS parts verify the feasibility and validity of this algorithm and system.

Description: Friction stir welding (FSW) of non-linear joints receives an increasing interest from several industrial sectors like automotive, urban transport and aerospace. A force-controlled robot is particularly suitable for welding complex geometries in lightweight alloys. However, complex geometries including three-dimensional joints, non-constant thicknesses and heat sinks such as clamps cause varying heat dissipation in the welded product. This will lead to changes in the process temperature and hence an unstable FSW process with varying mechanical properties. Furthermore, overheating can lead to a meltdown, causing the tool to sink down into the workpiece. This paper describes a temperature controller that modifies the spindle speed to maintain a constant welding temperature. A newly developed temperature measurement method is used which is able to measure the average tool temperature without the need for thermocouples inside the tool. The method is used to control both the plunging and welding operation. The developments presented here are applied to a robotic FSW system and can be directly implemented in a production setting.

Description: A product manufacturing process starts from parts processing, then assembles parts into components, and forms the product finally. To obtain an expected product quality, the quality characteristics in the part level, component level, and product level must be controlled, and the deviations between their actual and target values are required to keep in specified tolerances. All these tolerances form a product tolerance system, and the quality characteristics of product levels contain the geometric and the non-geometric parameters, which are interrelated and form a complex system. General tolerance is the total amount the actual parameters are permitted to vary, which not only include the geometric parameters in machining, but also includes physical, chemical, electrical, and other parameters. What most concerns the product users is whether product quality characteristics meet their requirements, rather than a component quality characteristic or part quality characteristic, and the product quality characteristics are generally not only geometric quantities but also include many non-geometric quantities. The product tolerance system optimization design from part level to product level cannot be achieved, as it includes geometric and non-geometric quantities. In this paper, a product tolerance system model is developed on the basis of determining the quality characteristics of product levels, and the information of the product levels quality characteristics is excavated from data recorded in the product testing process using data mining methods through the support vector nonlinear regression relational model between parts quality characteristics deviations and product quality characteristics deviations. Then, the product manufacturing cost model is set up, which includes the machining dimensional tolerances and non-geometric tolerances, and the product tolerance system optimization model is developed by minimizing the product manufacturing costs as the objective function and the quality characteristics tolerances of product levels as constraint conditions. Finally, a micro-motor product is used as an example to optimize its tolerance system, and its manufacturing costs are decreased by 13.14 %. The results show that the developed method is effective and provides a new way for the product tolerance system optimization.

Description: In this investigation, the nanoscale removal of the multilayer metal film structure from the surface of glass hard disk platters is carried out by an electrochemical reaction. The electrolytic process used is assisted by the application of ultrasonic vibration at very high frequency which effectively enhances the speed and efficiency of metal layer removal. The results also show that higher concentrations of electrolyte and higher temperature also increase the rate of metal layer removal. A high electrolyte flow rate accompanied by high energy ultrasonics results in a high etching rate. The closer the anode is to the surface of the workpiece (platter) and the smaller the gap between the two electrodes, the higher is the etching rate. Further enhancement of etching rate can be achieved by using a smaller anode and cathode as well as by using electrodes with smaller edge radii. A high rotational speed of the anode and cathode module also enhances metal removal because it speeds up the flow of electrolyte across the surface of the workpiece to remove dregs and heat. A high current flow increases the rate of etching and allows a higher workpiece feed rate with a resultant increase in speed and overall efficiency. An optimal combination of processing parameters (electrical conditions, electrolyte flow and control, dregs removal, etc.) allows clean and complete removal of the multilayered nano metal film microstructure from the glass hard disk platters. The basic technology for the micro-electrochemical removal of the nano metal film from glass hard disk surfaces has been established. In addition, the results set a benchmark for the extension of basic laboratory equipment, as well as the implementation and commercial application of the method by industry.

Description: Cutting performance and failure mechanisms of the ceramic cutting tools such as TTW7, BW3, TWTN3, and SG4 in continuous machining hardened Cr12MoV mold steel were investigated. There were no microburrs on the finished surface when hardened Cr12MoV mold steel was machined by these tools with coolant. In order to obtain the optimal cutting parameters, the orthogonal tests were employed in this investigation. The optimal cutting parameters were depth of cut a p  = 0.3 mm, feed rate f  = 0.1 mm/rev, and cutting speed v  = 60 m/min. The wear resistance was BW3 〉 SG4 〉 TTW7 〉 TWTN3 when these tools continuously machined the workpiece under the optimal cutting condition. The main wear mechanisms were adhesive wear and abrasive wear.

Description: Ti–6Al–4V is widely used in the aerospace, automobile, and biomedical fields, but is a difficult-to-machine material. Electrical discharge machining (EDM) is regarded as one of the most effective approaches to machining Ti–6Al–4V alloy, since it is a non-contact electro-thermal machining method, and it is independent from the mechanical properties of the processed material. This paper aims to combine grey relational analysis and Taguchi methods to solve the problem of EDM parameters optimization. From the viewpoint of health and environment, tap water as working fluid has good working environment, since it does not release harmful gas. The process parameters include discharge current, gap voltage, lifting height, negative polarity and pulse duty factor. The electrode wear ratio (EWR), material removal rate (MRR) and surface roughness (SR) as objective parameters are chosen to evaluate the whole machining effects. Experiments were carried out based on Taguchi L 9 orthogonal array and grey relational analysis, and then verified the results through a confirmation experiment. Compared the machining parameters A 1 B 1 C 3 D 2 with A 1 B 2 C 2 D 2 , MRR increased from 1.28 mm 3 /min to 2.38 mm 3 /min, EWR decreased from 0.14 to 0.10 mm 3 /min and SR decreased from Ra 2.37 μm to Ra 1.93 μm. The process parameters sequenced in order of relative importance are: the ratio of pulse width to pulse interval, discharge current, lifting height and gap voltage. The results showed that using tap water machining Ti–6Al–4V material can obtain high MRR, decrease the machining cost and have no harmful to the operators and the environment.

Description: This paper presents a meta-heuristic method for a resource-constrained project scheduling problem. In this problem, the activities are given with multiple executive modes and there are minimum as well as maximum time lags between different activities. The objective here is to determine a mode and a start (or finish) time, for each activity such that total tardiness/earliness cost of activities could be minimized. The meta-heuristic approach was developed, as a two-phased genetic algorithm. The process of solving the proposed problem includes two stages (phases). In the first stage, through applying a genetic algorithm, the main problem is simplified so that each activity has only one executive mode. In the second phase, through developing another genetic algorithm, the best answer to the problem is achieved. Finally, the computational results obtained from the solution algorithms of this research were compared with the results existing in the Project Scheduling Problem Library (PSPLIB). These algorithms were provided in the MATLAB programming language. The findings show that our algorithm improved some of the best recorded solutions in the PSPLIB.

Description: Heavy-duty milling processes find productivity limitations due to chatter vibrations related to the dynamic flexibility of the machine tool structure. In high-speed machining, the critical dynamic properties and the resultant process stability are highly dependent on the tool or tool holder and not on the machined part, the machining position or the feed direction. The latter factors have, however, a significant impact on stability of heavy-duty operations, which makes the current stability models unsuitable for the stability prediction of this kind of operations. The present study proposes a standard stability model with specific improvements focused on heavy-duty operations, considering the whole workspace and feed directions. This model is used as the basis for the development of a universal process planning and tool selection methodology. Finally, the proposed method is experimentally verified in two practical cases, where a typical steel roughing operation is successfully optimised for two different machines. The usefulness of the developed methodology is demonstrated.

Description: We consider a multistage processing system, which includes both identical (parallel) machines that can process the same set of operations and different machines that can process only different operation sets. A release time r i is given for each job J i to be processed. For such a processing system, we minimize the makespan, i.e., problem IJ | r i | C max $IJ|r_i|C_{\max }$ is considered. The problem IJ | r i | C max $IJ|r_i|C_{\max }$ is an extension of the classical job-shop problem J | r i | C max $J|r_i|C_{\max }$ for the case when parallel (or identical) machines are also given. Both problems J | r i | C max $J|r_i|C_{\max }$ and IJ | r i | C max $IJ|r_i|C_{\max }$ are strongly NP-hard. A mixed graph model used for solving the problem J | r i | C max $J|r_i|C_{\max }$ is generalized for the problem IJ | r i | C max $IJ|r_i|C_{\max }$ . Using the mixed graph model, we developed a fast heuristic algorithm for solving the problem IJ | r i | C max $IJ|r_i|C_{\max }$ . Computational experiments were conducted to evaluate the performance of the algorithm on the 22 benchmark instances and on the 40 new randomly generated instances of the problem IJ | | C max $IJ||C_{\max }$ . For the small and moderate instances, the exact values of the objective function were compared with those calculated by the proposed heuristic algorithm. The average relative error was not greater than 2 . 4 % $2.4~\%$ for all instances with available optimal schedules. Computational results showed that the developed algorithm runs faster than some other heuristics being tested, and the schedules constructed by the developed algorithm have smaller makespans.

Description: High injury and fatality rates prevalent in all types of construction in the USA may be addressed by combining safety initiatives with process improvement through Lean. This study evaluated the impact on worker safety when Kaizen (a Lean tool) was used at a modular homebuilder. Twelve students who had completed a safety course and four safety experts rated the probability and severity of hazards (as determined by a job safety analysis, or JSA) present in three workstations; base-framing, sheet rock hanging, and painting. These ratings were provided after viewing a series of photographs taken before and after a Kaizen event performed at each workstation. The rating tool showed high reliability for all safety experts' ratings but only for students' ratings from the sheet rock hanging station. Students' and experts' ratings showed a significant reduction in risk in the base-framing station after the Kaizen, and student's ratings showed significantly reduced risk in the sheet-rock hanging station. Kaizen has the potential to improve safety in modular homebuilding and possibly, other manufacturing and construction activities.

Description: An investigation was reported on the cutting temperature in milling Ti6Al4V by applying semi-artificial thermocouple. ANOVA was conducted on the experimental results, and regression models were obtained. Analysis results showed that the tool temperature and workpiece temperature performed a similar rising trend with the increase of cutting parameters, including cutting speed, feed rate, radial feed, and axial feed. And their influence degrees decreased successively. The cutting force with different cutting parameters was also measured, and the relationship between cutting temperature and cutting force was discussed. It was found that cutting temperature and cutting force obtained in the experiment had the same fluctuation feature. Therefore, the cutting force and cutting temperature could complement each other for monitoring and analysis of the cutting process.

Description: This paper investigates how changes in chatter amplitude and frequency depend on process damping effect in dynamic turning process. For this purpose, the two degrees of freedom (TDOF) cutting system was modeled, and for an orthogonal turning system, the process damping model with a new simple approach was developed. To further explore the nature of the TDOF cutting model, a numerical simulation of the process was developed by this model. This simulation was able to overcome some of the weaknesses of the analytical model. The equations of motion for this cutting system were written as linear and nonlinear in the τ -decomposition form. The variation in the process damping ratios for different work materials was simply obtained by solving the nonlinear differential equations. A series of orthogonal chatter stability tests were performed for the identification of dynamic cutting force coefficients, using AISI-1040, Al-7075, and Al-6061 work materials, at a constant spindle speed. Finally, the experimental results were analyzed and compared with the simulation model, and it was observed that the results obtained through the experiments comply with the simulation model results.

Description: This paper focuses on the mechanism of high-speed grinding to achieve quality and efficiency for ceramics. The criterion of the brittle–ductile removal transition of ceramics is calculated and analyzed. The effects of the wheel velocity on the specific grinding forces, energy, and specific material removal rates were investigated. The influence of the wheel velocity on the surface integrity was studied in the terms of surface roughness by a 3D optical profilometer, scanning electron microscopy, respectively. The ductile removal mechanism of brittle material was validated experimentally. High quality and efficiency of grinding for SiC can been attained with high-speed grinding due to the understanding of the characteristics and mechanism for ductile grinding of brittle materials with high-speed grinding. Furthermore, based on the high-performance grinding mechanism, reasonable definitions on high-speed grinding are proposed.

Description: In order to realize the size measurement of large forgings in thermal state, an online measurement method based on line laser scanning is proposed in the paper. The measurement system mainly consists of a line laser projector and a charge-coupled device (CCD) camera. The laser projector is driven by the stepper motor for scanning the forgings continuously, while real-time images are captured by the CCD to provide the information for further feature extraction. First of all, particle swarm optimization algorithm is utilized to reduce the optical distortion error between actual and ideal images as a kind of optimization method. Secondly, the preprocessing is carried out to improve the image quality of the hot parts, and further two-dimensional image information of the forgings is obtained by means of center extraction. Thirdly, the size of forgings is calculated through processing the data acquired by continuous scanning the forgings and the real-time shotting. Finally, the measurement of forgings on overall outside size is achieved. The method proposed in the paper is viable according to the experiment results.

Description: The present work is meant to show the effective capability of optimizing an unbalanced Paired-Cell Overlapping Loops of Cards with Authorization (POLCA)-controlled production system by means of a heuristic algorithm. This objective is suggested by the fact that one of the most significant issues when using card-driven production control systems is represented by the optimized setting of the large number of cards within the control loops. This is particularly true in the case of unbalanced systems, where the number of cards may vary significantly among the different loops. Little law is usually adopted in literature to infer this number from historical data, but the obtained number is usually far from the optimum. Indeed, in real-world applications, the systems to be controlled are designed to process units with very different routings, each with different probability to occur. In all these situations, they result particularly difficult to set correctly. To this aim, in the present work a Genetic Algorithm is used. The objective is that of finding the correct number of cards and to reduce the overall Total Throughput Time and the average Work In Process. The proposed approach may provide a valid support tool to overcome these limitations, making the most of POLCA capabilities in many manufacturing configurations.

Description: This paper presents the design philosophy of an ultra-precision fly cutting machine tool from the machining material properties and the processing requirements points of view. Three configurations of the machine tool are proposed and compared from the aspect of the proposed design philosophy. The design philosophy has been applied to guide the development of the key machine components as well as an experimental prototype. In order to improve the dynamic performances of the machine tool, the influence of the main components on the tool–workpiece structural loop is analyzed, and the weak structural component is optimized. Preliminary machining trials have been carried out. The test results make a further proof and validate that the design philosophy proposed in this article can assure the high performance of the developed ultra-precision fly cutting machine tool for producing large diameter optics.

Description: A distributed coevolutionary algorithm is proposed to solve the multiobjective hybrid flowshop scheduling problems to minimize the maximum completion time and total tardiness of jobs. The framework of the distributed coevolutionary algorithm consists of a global agent and multiple local agents. The global agent and local agents evolve independently and cooperate by interchanging a selected solution list. Unlike the cooperative coevolutionary algorithms in the literature, the proposed algorithm does not decompose the scheduling problem and executes evolutionary operations based on the whole solution of the problem in all the agents. SPEA2 is the core components in the local agents. Path relinking is applied in order to implement the evolutionary computation among non-dominated solutions in the global agent. We analyzed the time complexity of the proposed algorithm. To evaluate the performance against the benchmark of multiobjective evolutionary algorithms, it is tested on a large number of computational instances. The computational experiments show the proposed distributed coevolutionary algorithm can obtain better solution quality than other algorithms within given computational time.

Description: Fabrication of microparts has become increasingly important with an advancement of product miniaturization in various fields. Microgrooves are used as one of the key microfeatures in many microproducts like microthermal devices, microheat exchangers, microreactors, micropumps, and micromechanical systems. Electrochemical micromachining (EMM) can be effectively utilized for the fabrication of microgrooves because of its important benefits like reusability of the tool, no stress, burr-free surfaces, and ability to cut the material irrespective of the hardness. This paper presents the influence of EMM parameters like applied voltage, pulse frequency, duty ratio, tool feed rate, and electrolyte concentration on the machining accuracy, i.e., width overcut, depth overcut, and material removal rate during fabrication of a 500 μm-deep microgroove in stainless steel. An in situ-fabricated tungsten microtool of 110 μm diameter was used to generate a microgroove using the developed EMM setup. A high-quality microgroove with 55 μm width overcut and 10-μm depth overcut with an aspect ratio of 2.31 was fabricated using the optimum setting of machining parameters.

Description: Grind hardening process utilizes the heat generated in the grinding area for the surface heat treatment of the workpiece. The workpiece surface is heated above the austenitizing temperature by using large values of depth of cut and low workpiece feed speeds. However, such process parameter combinations result in high process forces that inhibit the broad application of grind hardening to smaller grinding machines. In the present paper, modelling and predicting of the process forces as a function of the process parameters are presented. The theoretical predictions present good agreement with experimental results. The results of the study can be used for the prediction of the grind hardening process forces and, therefore, optimize the process parameters so as to be used with every size grinding machine.

Description: Aimed at microplastic parts molding, we use a novel method of micro-ultrasonic powder molding (micro-UPM) on polypropylene (PP) microplastic parts and investigate the experimental process in detail. Firstly, the experimental results show that the temperature is maximum on the top outer edges of plastic parts and minimum on the bottom center. Then, the effects of experimental process parameters on plastic flashes are studied. The results show that under the same pressure, the flash thickness gradually thins with increased ultrasonic time. The ultrasonic time for the flashes to be automatically separated from the matrix of microplastic parts is obviously shortens with increased pressure. Finally, the tests on thermal properties, morphology, and mechanical properties of microplastic parts are also conducted. The results show that the melting point and crystallinity of microplastic parts produced by micro-UPM are higher than those of raw materials. The organizational structure shows no obvious “skin–core” structure, and its crystal form is α crystal form, which is the most common type of polypropylene. With increased ultrasonic time, the tensile strength and elongation at break of samples both have a trend of rise followed by drop before and after annealing. An ultrasonic time that is too long can lead to the degradation of materials.

Description: Functional micro surfaces have been recognized for their vital roles in a wide range of advanced applications. The fabrication of surface structures at the microlevel can be used to influence tribological, optical, and many other surface characteristics. To take advantage of the benefits of functional surfaces, industry and researchers have begun focusing on finding more sustainable and efficient manufacturing processes. The inclined micro ball end milling technique has become a fast and efficient method for creating micropatterned surfaces. With the right adjustments, the spindle speed and feed rate can be set so that the flutes of the cutter create periodic dimpled patterns onto a workpiece surface. This micromachining technique is an ideal method for fabricating dimpled surfaces, especially for metallic alloys such as dies and molds. Developing surface pattern algorithms for generating different dimple geometries can promote a sustainable future for a variety of novel products and lead to accurate manufacturing of surface characteristics. Accurate modeling of cutting forces is important in order to generate desired surface patterns without causing tool breakage and excessive tool deflection. In this study, a mechanistic force model for inclined ball end milling has been proposed and verified for generating micro-dimpled surface. The micro-dimple machining technique is also applied to microinjection molds to create polymeric components with micropatterns. Frictional aspects of both dimpled and inverted dimple surfaces have been investigated. The results indicate that micro-dimple machining combined with microinjection molding is a viable method of producing polymeric components with functional surfaces for advanced technological applications.

Description: High-strength wear-resisting aluminum bronze alloy is a difficult-to-machine material. Dry cutting tests were conducted on high-strength wear-resisting aluminum bronze alloy with YW1 cemented carbide tool and YBC251 coated cemented carbide tool. The wear mechanisms of the two tools were characterized with a scanning electron microscope (SEM) and an energy-dispersive spectrometer (EDS) to compare their machining performances. And on that basis, the influences of cutting parameters, including cutting speed, feed rate, and cutting depth, on the tool life of the YBC251 coated cemented carbide tool and surface roughness of the workpiece were analyzed with a 3-D super-depth-of-field instrument and a surface profile measuring instrument, respectively. The results showed that the machining performance of the YBC251 coated cemented carbide tool was better than that of the YW1 cemented carbide tool. Among all the cutting parameters, it was found that feed rate had a stronger effect on tool life and surface roughness than cutting speed and cutting depth.

Description: Predicting the fragmentation process during rock cutting poses significant technical challenges. In this respect, previous research related to rock cutting using various numerical methods was reviewed in detail. A method for simulating the fragmentation process during the mechanical cutting of rock was then introduced using the explicit finite element code LS-DYNA. In the numerical simulations, the base rock material properties were defined using a damage constitutive model. This model simulates the separation of rock chips from the base rock material and the subsequent breakage of the chips into multiple fragments. In the simulations, a rigid steel cutting tool was translated at various sliding velocities (1, 4, 10, 50, and 100 mm/s) against a stationary rock material. For a given sliding velocity, simulations were conducted for various cutting depths (1, 2, 3, and 4 mm). The variation of stresses and the amount of chip formation at different depths of cut and velocities were analyzed. The simulations indicated that the cutting forces and chip morphology were significantly influenced by sliding velocities and cutting depths. Overall, the results indicate that the explicit finite element method was a powerful tool for simulating rock cutting and the chip fragmentation processes, as it was able to predict chip separation behavior from the base rock at different depths of cut accurately.

Description: Cold formed semi-finished products face an increasing demand from industry as they can be manufactured to dimensional precision and high surface quality. Products from cold formed bar, on the other hand, may contain inhomogeneous distributions of mechanical properties and residual stresses which arise from the elastic response of the material to an inhomogeneous distribution of elastic–plastic strains. These material properties may cause distortion in further manufacturing operations, and consequently, precision of components then could be reestablished at higher costs only. X-ray diffraction residual stress analysis, for example, is misleading if only slices or cross sections of a bar or a component are considered and residual stress fields and their variations are neglected. Automotive products generally are cut from drawn bars, and local differences in microstructure, mechanical properties and residual stress states are increasing the danger of dimensional changes out of a specified range. Cold-drawn bars were manufactured with different drawing angles and uncoated and TiCN-coated dies. Surface and subsurface properties were investigated along the length and around the periphery of drawn bars. Differences in material states, those affected by the contact zone and those related to the elastic–plastic deformation of the drawing process, were observed. The variation of surface residual stresses of up to a factor of 2 can be correlated with locally different friction coefficients and slip stick effects. As subsurface material states (residual stresses and strain hardening) do not show a significant variation around the periphery and along the length of bars, the effects of geometry variations of hot rolled bar, the effect of a not perfectly concentric bar at the die entrance and/or the level of pre-straightening ahead of drawing are assumed to be of minor importance, compared to the high level of plastic strain involved in cold drawing. The local properties identified here will lead to a higher degree of dimensional scatter of individual automotive components cut from these long cold-drawn bars.

Description: It is usually difficult to obtain good images for machine vision inspection in a manufacturing process. In practice, to obtain product characteristics, image enhancement methods are usually selected by trial-and-error or by experience. Therefore, image enhancement methods play a key role in image pre-processing. In this paper, we propose singular value decomposition (SVD) to extract the feature of images to automatically build image enhancement procedures. First, we completed image clustering according to the feature by using SVD. Next, the structural similarity index was used to select the optimal image enhancement method. To verify the procedures, 45 images from literature and local companies were used in the experimental analysis. For contrast value, the statistical analysis showed that the automatic enhancement result has no significant difference with the literature. The average entropy of the image relative to previous research increased to 17.54 %. The study results implied that the system could effectively improve the image quality and not over enhancement to produce noise.

Description: Self-pierce riveting has a future in the sheet metal assembly process in automotive industry. This paper aims to analyze the variation of auto-body aluminum alloy sheet metal assembly in self-pierce riveting and obtain the method of assembly variation analysis. With the help of the method of influence coefficients and the research of the assembly progress of auto-body aluminum alloy sheet metal in self-pierce riveting, a model which can reflect the effects of part variation, riveting tool variation, and fixture variation on assembly quality is established. The feasibility of assembly variation analysis is also verified by some practical cases. Finally, the orthogonal experiment has been carried out to analyze the effects of some variation sources on the variation of assembly in self-pierce riveting.

Description: A fast tool feeding mechanism with 2 degrees of freedom was proposed in this paper. The mechanism was directly driven and could compensate for changes in the cutting angle caused by contour adjustments. A turning system with constant cutting angle and speed were designed with the mechanism, which had many advantages including adjustable cutting angle, improving machined surface quality, reducing tool wear, extending the service life of tool, and so on. A model of the variable angle compensation movement of noncircular cross section part turning and its control algorithms was discussed according to the principle of inverse kinematics. With the machining of a convex oval piston taken as an example, a real convex oval piston model with a maximum ovality of 10 mm was processed through the fast tool feeding mechanism. Experiment results verified the design concept and control strategy of the mechanism.

Description: Stability prediction is important to avoid chatter and improve production efficiency in cutting process. Many methods including analytical, experimental, and numerical ones have been proposed. In this work, a stability criteria method using argument principle is proposed for a general dynamical systems. The method needs only to evaluate the characteristic function on a straight segment on the imaginary axis and the argument on the boundary of a bounded half circular region. The method is applied to three milling models in cutting process. Examples which show the evaluation of stability criteria proposed in the paper is simple and valid compared with full-discretization method.

Description: For laser surface hardening (LSH) of large-sized workpieces, a wide and uniform hardened layer of a single track is pursued. In this study, two kinds of shaped laser beams were used in LSH of 42CrMo cast steel to obtain the required hardened layer. One is a stripy spot with uniform-intensity array spots and the other a stripy spot with intensity blowup in the edge of the whole array spots. As a comparison, a Gaussian laser beam was also adopted. A three-dimensional finite element model was used to simulate the thermal history of specific points by the latter shaped beam and the Gaussian laser beam. The surface morphology, microstructure, microhardness, and uniformity of hardened layers were studied. The results showed that a wider and more uniform hardened layer could be obtained using the latter shaped beam at relative higher scanning velocities and laser power. The thermal history of a material has an important effect on the microstructure and microhardness finally formed. Due to the high peak temperature and heating rate caused by the latter shaped beam, a higher value of microhardness in the transformation hardened zone was found.

Description: Micro-electrical discharge machining (EDM) has been identified as a micromachining process for the fabrication of components of size down to the micrometer level. This process is derived from EDM, and the principles of both the processes are similar; yet, due to significant scaling down of the micro-EDM process, lots of modifications in circuit design, electrode diameter, stress developed, and energy levels are needed. The specific analysis and modification of micro-EDM process are required to understand these capability and limitations. Therefore, a numerical model based on finite volume method has been developed to solve the micro-EDM model equations and thereby predict the effect of spark ratio (spark on time/spark off time) on the temperature distribution in the material. Moreover, the results of the analysis are successfully tested against published ones.

Description: Flexible automated assembly is an emerging need in several industries. In the case of a very wide set of models and a total medium/low derived production volume, the proper assembly system to use is a single cell with high flexibility capabilities. An innovative concept in flexible automated assembly has recently been introduced [ 28 , 29 ]: the fully flexible assembly system (F-FAS). The F-FAS relies on a single-station robotized assembly system, where a unique fully flexible feeder is responsible for the delivery of the parts needed for assembly, guaranteeing a higher level of flexibility than the traditional automated FAS. The mixed-model sequencing (MMS) problem is typically related to the assembly line system. The aim of this paper is to introduce a new class of MMS problem: the single-station mixed-model sequencing problem that arises when the parts to assemble are randomly presented on the working plane, as in the F-FAS. The authors first define the MMS in such a single-station assembly system and then propose different sequencing algorithms in order to solve it. The authors first define the problem and then propose different sequencing algorithms. With the aim of finding the best sequencing approach to use in such an assembly system, the algorithms are compared through ad hoc developed benchmarking tests, using a dedicated software application that simulates the real behavior of the work cell.

Description: Confronted with high variety and low volume market demands, many companies, especially the Japanese electronics manufacturing companies, have reconfigured their conveyor assembly lines and adopted seru production systems. Seru production system is a new type of work-cell-based manufacturing system. A lot of successful practices and experience show that seru production system can gain considerable flexibility of job shop and high efficiency of conveyor assembly line. In implementing seru production, the multi-skilled worker is the most important precondition, and some issues about multi-skilled workers are central and foremost. In this paper, we investigate the training and assignment problem of workers when a conveyor assembly line is entirely reconfigured into several serus . We formulate a mathematical model with double objectives which aim to minimize the total training cost and to balance the total processing times among multi-skilled workers in each seru . To obtain the satisfied task-to-worker training plan and worker-to- seru assignment plan, a three-stage heuristic algorithm with nine steps is developed to solve this mathematical model. Then, several computational cases are taken and computed by MATLAB programming. The computation and analysis results validate the performances of the proposed mathematical model and heuristic algorithm.

Description: In order to obtain a three-dimensional curved steel tube, a bending method is presented based on geometric curvatures with a scanning path planning decomposed into a two-dimensional model and restructured into a three-dimensional model, sequentially. In the decomposition and restructuring, tube plane bending is simplified into two-dimension curve project, while 3D tube bending is equivalent to two 2D space curves’ projects. In 2D bending, the plane deals with modeling idea based on the extreme points and inflection points of two-dimension curve. The main idea performs narrowing of scanning path near extreme point area, but widening scanning path near inflection point. In 3D bending, the forming surface is decomposed into two planar curves by projecting on two vertical planes. Respective scanning path planning and process parameters are thus acquired. By combining the data in the two-dimension planes, the three-dimension scanning path plane was obtained. Finally, an experimental verification is carried out to bend straight tubes into a two-dimension sinusoidal and a three-dimension helical tube/coil-shaped. The results show that the scanning path planning proposed in this paper is effective and feasible.

Description: One of the important design elements for a good production system is material handling. In cases where it is not well-designed, it can be the bottleneck in the system. Moreover, it can cause a lot of wastes such as waiting time, idle time, and excessive transportation and cost. In this study, material handling in lean-based production environments is taken into account. Depending on the lean structure of the production systems such as being pull-based, smooth, and repetitive, delivering the materials to the stations periodically becomes important. At this point, milk-run trains are highly used in real applications since they enable the handling of required amount of materials on a planned basis. With this study, it is aimed to develop a specific model for milk-run trains which travel periodically in the production environment on a predefined route in equal cycle times with the aim of minimizing work-in-process and transportation costs. Since the milk-run trains having equal cycle times start their tours at the same time intervals, it becomes simple to manage them. For this reason, they are used in lean production systems where level scheduling is performed. The developed model is based on mixed-integer linear programming, and since it is difficult to find the optimum solution due to the combinatorial structure of the problem, a novel heuristic approach is developed. A numerical example is provided so as to show the applicability of the mathematical model and the heuristic approach.

Description: Mixed elastohydrodynamic lubrication (mixed EHL) model has been successfully used to study phenomena in chemical mechanical polishing (CMP) process. However, in various mixed EHL simulation frameworks, a polishing pad's deformation cannot correctly be described by adopted models for pad deformation such as elastic half-space model and Winkler elastic foundation model. Thus, a more accurate model for pad deformation is needed, since this is the prerequisite for an accurate prediction of contact pressure and material removal rate, which is critical for improvement of polishing quality. In this paper, a layered elastic theory, which is frequently used to calculate flexible pavement response to truck loading, is introduced into the mixed EHL model. It is found that this theory has a similar accuracy to the traditional 3D finite element method for calculating the pad deformation. However, its computational cost is much lower, which is especially important for accurate and efficient simulation of mechanical behavior and material removal rate (MRR) in CMP. In order to highlight benefits of the proposed theory, simulations are carried out based on three different pad deformation models with the mixed EHL model. The pad deformation behavior is found to have a significant influence on the final simulation results, especially the MRR prediction. By comparing the different simulation models, the proposed layer elastic theory is found to be an optimal model for describing the polishing pad deformation behavior in CMP and can provide accurate simulation results on contact pressure distribution and the material removal rate.

Description: This paper combines plasticity and circle grid analysis to investigate the deformation mechanics and failure in hole-flanging produced by single point incremental forming (SPIF). The approach is based on circle grid analysis and allows tracing strains and stresses along the deformation history of material to compare their maximum achievable values against necking and fracture limits in the principal strain and stress spaces. The overall methodology draws from the independent characterization of necking and fracture limits by means of sheet metal formability tests to the appraisal of strain loading paths in hole-flanging with blanks having different pre-cut hole diameters. The work is supported by experimentation in aluminium AA1050-H111 and the overall investigation widens previous research in the field by presenting the first set of experimental data covering the history of material strains, stresses and their corresponding formability limits.

Description: Many efforts in the past have been made to find more efficient methods for assembly sequence planning in machining area. While few researches reported in other area such as block assembly in shipbuilding industry. In general, a ship hull is built with hundreds of different blocks, most of which are complicated in structure and different from each other in assembly planning. Additionally, there may be a large number of feasible assembly sequences for any block. A better sequence can help to reduce the cost and time of the manufacture. Therefore, it is necessary to seek out the optimal sequence from all feasible ones. Currently, the assembly sequences are determined manually by some process engineers. Consequently, it is becoming a time-consuming task and cannot make the assembly plan consistent to improve productivity. In this paper, a methodology-integrated case-based reasoning and constraints-based reasoning is proposed to improve the assembly planning for complicated products. Besides, genetic algorithm is designed to evaluate and select the optimal sequence automatically from the reference ones. The validity of the method is tested using real blocks, and the results show that it can facilitate the optimal assembly sequences generation.

Description: In this paper, the effects and the optimization of cutting parameters on surface roughness (Ra) and material removal rate (MRR) in the wire electrical discharge machining (WEDM) of high hardness tool steel YG15 are analyzed. In the WEDM process, the key process parameters, such as pulse-on time, pulse-off time, power, cutting feed rate, wire tension, wire speed, and water pressure, are optimized. Experimental data were initially collected based on the Taguchi method of experimental design, which are $L_{18}\left (2^1\times 3^5\right )$ and $L_{18}\left (2^1\times 3^4\right )$ Taguchi standard orthogonal array on rough and finish cutting experiments, respectively. The level of importance of the cutting parameters on the Ra and MRR was determined on both finish and rough cutting by using statistical analyses; average gap voltage is discussed in order to balance cutting efficiency and stability on both finish and rough cutting. In addition, comparative analysis of finish and rough cutting is drawn to analyze the difference between rough cutting and finish cutting. Then, regression models and signal-to-noise ratio are used to obtain the optimum cutting parameter combination. Finally, the results present the optimized MRR and Ra of the rough and finish process, respectively, and confirm the efficiency and abilities of the model.

Description: During the classical manufacturing process of conical thread surfaces with lathe center displacement, the worm shaft is driven with the help of the driving pin through the lathe fork. As a result of the shifting of the worm shaft by half cone angle, the path curve of the driving pin will be an ellipse path instead of a circle on the perpendicular plane to axis. The peripheral speed of the spindle is constant, but due to the ellipse path, the radius is constantly changing as a function of time. That is why the angular velocity and the angular rotation are also changing, and these cause pitch fluctuation during the manufacturing process of conical worms. During the manufacturing process, we have examined pitch errors which are caused by angular velocity fluctuation and we have also determined the geometrical shaping of the driving pin by which errors of the pitch can be eliminated.

Description: Superplastic forming of titanium alloys is used for producing structural components, since it is an effective way to manufacture complex-shaped parts in a one-step operation. An optimized sheet-forming process has been designed incorporating a non-isothermal heating system to establish a fast forming process. This work sought to expand the advantages of the technology to the forming of Ti-6Al-4V alloy at 800 °C and shorter cycle time. The minimum thicknesses area was found at the outward corners, showing a maximum percent thinning of 54 %. In addition to stress variations, the cracks resulting from hot drawing and the oxidation on the sheet surface are the other reasons leading to thickness reduction. From the oxidization behavior of Ti-6Al-4V alloy, it was revealed that the decrease in forming temperature from 900 to 800 °C significantly reduced the formation rate of oxide film on the sheet surface. The study also showed that the main microstructure evolution of Ti-6Al-4V alloy under these conditions was recrystallization.

Description: In this research work, an experimental evaluation was conducted to explore the fretting fatigue life of multilayer Cr–CrN-coated AL7075-T6 alloy specimens with higher adhesion strength to substrate as the coating adhesion strength is one of the most critical issues in magnetron sputtering technique. Physical vapor deposition (PVD) magnetron sputtering technique was used for coating purpose, and a fuzzy rule-based system was established to investigate how to achieve higher adhesion of Cr–CrN coating on AL7075-T6 with respect to changes in input process parameters, direct current power, nitrogen flow rate, and temperature. Close assent was obtained between the experimental results and fuzzy model predicted values. Experimental result analysis was performed with Pareto–ANOVA variance as an alternative analysis. The fretting fatigue lives of coated AL7075-T6 alloy were improved 70 % and 22 % at high and low cyclic fatigue, respectively, compared with uncoated specimens.

Description: This article reviews the existing work in self-healing and self-repairing technologies, including work in software engineering, materials, mechanics, electronics, MEMS, self-reconfigurable robotics, and others. It suggests a terminology and taxonomy for self-healing and self-repair, and discusses the various related types of other self-* properties. The mechanisms and methods leading to self-healing are reviewed, and common elements across disciplines are identified.

Description: Turning is a widely used machining process, but the process complexity and uncertainty lead to empirical modelling techniques being preferred over physics-based models for predicting the process performance. The literature reveals that empirical methods such as artificial neural networks (ANN), support vector regression (SVR), regression analysis and fuzzy logic have been extensively applied in the modelling of turning process. The present work introduces genetic programming (GP) for the modelling of turning, but it is observed that the optimal models selected from the GP population based on training and validation errors do not perform well on testing data (unseen samples). Selecting the best GP model from the population of models is therefore a vital step. In view of this, the classification-driven model selection approach of GP (C-GP) is proposed in this paper. In this methodology, potential classification techniques such as Bayes multinomial, partitioning and regression trees, classification and regression trees and decision trees are integrated with GP to predict the class (best or bad) of the GP models. The model that is classified as the “best” by the most number of classification techniques is selected, and its performance is compared to those from ANN and SVR. It is found that the C-GP model has accuracy on par with ANN and gives satisfactory performance on testing data.

Description: In experiments, it is usually difficult to accurately determine simulation input parameters such as heat source parameters, material properties at high temperature, etc. The uncertainty of such input parameters is responsible for the large error of thermal simulation for weld-based additive manufacturing. In this paper, a new approach is presented to calibrate uncertain input parameters. The approach is based on the solution of the inverse heat conduction problem of small-scale five-layer deposition and the application of the infrared (IR) imaging technique. The calibration of heat source parameters involves a multivariate optimization search using the pattern search method, whereas the calibration of the combined radiation and convection model includes a number of one-dimensional searches using the Fibonacci search method. Based on an in-depth analysis of IR images, thermal characteristics such as mean layer temperature and cooling rate are selected as the comparison results and included in cost functions. Lastly, the validity of the approach is demonstrated by a simulation case of 15-layer deposition with calibrated input parameters. The comparison between the simulated and experimental results verifies the improved prediction accuracy.

Description: The loading path is crucial to the quality of forming parts in the process of tube hydroforming, and thus the design and optimization of loading path is an important issue for tube hydroforming. Wrinkling is a catastrophic defect for thin-walled tube hydroforming. In order to avoid wrinkling, an adaptive simulation approach integrated with a fuzzy control algorithm is used to optimize the loading path of hydroforming a T-shaped tube. The tubular material used is stainless steel and has an outer diameter of 103 mm and the wall thickness of 1.5 mm. The controlled variables are the axial feeding, the counterpunch displacement, and the internal pressure. A code is developed to make the optimization automatically, which works together with LS-DYNA. Six evaluation functions are adopted for identifying geometrical shape and quality of T-shape. Failure indicators obtained from the simulation results are used as the input of the fuzzy control, and then process parameters are adjusted according to the expert experiences in the fuzzy controller. In this way, a reasonable loading path for producing a sound T-shape is obtained, and also a T-shaped product is successfully hydroformed by experiment. The result shows that the fuzzy control algorithm can provide an adequately reliable loading path for hydroforming T-shaped tubes.

Description: In this paper, polyamide 6 single layer laser sintering process was investigated. A moving volumetric heat source model that involves the energy function morphology was simulated, and the temperature field distribution of a single layer of polyamide 6 powder was investigated using the finite element method, with different scan space and preheating temperature. The sintering processes were conducted on several batch of single layer with original thickness of 0.5 mm, which consists of 80 mesh polyamide 6 powders. Then the percentage of porosity was calculated and tensile stress of was tested. The results indicate that the scanning space strongly affect the percentage of porosity. For example, the percentage of porosity reaches 45.1 % when the scanning space increases from 0.25 to 0.45 mm. The results also indicate that the preheating and holding temperature strongly affect the mechanical properties. For example, the max tensile test stress increased from 2.04 to 4.10 MPa when the temperature rises from 50 to 150 °C, while the percentage of porosity shows very limited shift, reducing by only 9.54 %.

Description: Manufacturing capability sharing and circulation are the most important aims in cloud manufacturing (CMfg). In order to realize the above target, the issue of how to realize the formal description of manufacturing capability need to be solved. In this paper, a modeling and description method of multidimensional information for manufacturing capability in CMfg system is studied. Firstly, the concept and current research related to manufacturing capability are summarized. Then a multidimensional information model of manufacturing capability is established. Based on the model, a description method of manufacturing capability is proposed, and the related key technologies, e.g., fuzzy information description and dynamic behavior description, are systematically analyzed. Finally, the effectiveness of the proposed method is validated by a case study.

Description: One of the major manufacturing processes to produce components from flat sheets is forming. The automotive industry is one of the highest markets for stamped parts and is, thus, a major driving force for the development of new materials and technologies. In recent decades, there is increasing competition and growing demand for light weight, high-performance, and crashworthiness structures in the automotive vehicle forced steel industry, automakers, and the scientific community to focus more on efficient manufacturing. In recent decades, the increasing competition and growing demand for steel structures in automobiles was observed, especially for advanced high-strength steel (AHSS) parts. Thus, a better understanding of the formability of these materials is necessary to reduce costs and optimize the process. In order to better understand the mechanical behavior of AHSS, many authors have been researching the fracture aspects related to the stamping conditions. The main aim of this study was to analyze the type of fracture in DP600 steel when subjected to different stress/strain states (uniaxial and biaxial stress and plane strain) imposed by deep drawing and stretching. The experimentations led to a detailed understanding of the influence of stress/strain state in the mechanism of fracture, particularly, under plane strain—which showed quasi-cleavage regions surrounded by dimples. In addition, the microstructural analysis confirmed that the DP600 steel can show ductile fractures with some aspects of brittle behavior, depending of which stress/strain state was used for deformation. As a result, the DP600 forming limit curve related to micromechanisms of fracture generated by uniaxial and biaxial tensile stress and plane strain was presented.

Description: Automated manufacturing processes such as automotive tandem press lines include time dependent complex control functions. All motions and critical interactions between moving parts must be synchronised to avoid collisions and reach high production rate. It is even for a skilled operator hard to optimise these processes on-line. Therefore, a hardware-in-the-loop simulation including real industrial control systems and its control code establish an essential tool for optimisation. Additionally, an efficient optimisation algorithm is required to reach a useful simulation-based optimisation method. This paper proposes a new optimisation algorithm starting with the Lipschitzian algorithm DIRECT as global search and then switches over to the Nelder–Mead simplex algorithm for local convergence. During the switch over, the new algorithm determines all local candidates of the set of points evaluated by DIRECT and starts multiple Nelder–Mead local searches in each of these. An optimisation study for an automotive press line shows that the proposed algorithm combines the benefits of the Lipschitzian and the simplex algorithms in an efficient way. The importance of multiple local searches from all local candidates found is also shown in the study. Based on the same number of function evaluations, it is also shown that this algorithm reaches improved press line performances compared to the stochastic differential evolution algorithm.

Description: Adiabatic shear localization fracture (ASLF), which is a catastrophic fracture of the adiabatic shear band (ASB), will occur inevitably with the further increase of cutting speed. High-speed machining experiment of hardened AISI 1045 steel (HRC 45) is carried out by using a PCBN cutter with rake angle −10° at various cutting speeds up to 1,400 m/min and various feeds from 0.2 to 0.4 mm/r. Chip morphology (including discontinuously serrated chip and isolated segments), crack propagation, and blue brittleness effect in isolated segments formation are observed microscopically. Energy convergence in ASB with cutting conditions is calculated. Considering the effect of shear wave on the formation of ASB in high-speed machining, the ASLF theory under triaxial stress state is proposed and compared with the experimental results. The influences of shear band properties and loading conditions on ASLF are also discussed. The energy saturation limit of the shear band can be reasonably estimated by using the ASLF theory, which lays a theoretical and experimental foundation for further prediction study of isolated segments formation in high-speed machining.

Description: This study reports the fabrication of LZ91 magnesium alloy screws using warm heading and thread-rolling processes. The proposed method consists of a two-stage warm heading process. This study presents an analysis of the material flow pattern of the billet inside the die by using finite element analyses. This study also presents the effects of upper die velocity, temperatures, and friction factors on the heading loads and product quality. This paper also investigates the effects of the friction factor on the effective stress, effective strain, and tooth height in a thread-rolling process. Finally, warm heading and thread-rolling experiments were conducted using a self-designed die set and a MoS 2 lubricant. This study presents a comparison of the experimental values with the simulation results to verify the validity of the finite element models and the proposed warm heading procedures.

Description: In the current metal-forming industries, productivity, product quality, and production cost are three overriding issues. Product quality, however, is the most critical issue and the designed forming process must be able to produce the quality parts with desirable geometries and without defects. In micro- and meso-forming processes, the formation mechanism of flow-induced defects has not yet been fully investigated. In this paper, the flow-induced defects in meso-forming of a designed part are investigated and the defect formation mechanisms are explored and revealed via the finite element simulation of the entire process. To develop a defect-free forming process, a feature-based method for defect-free process design is proposed to identify the best forming sequence/process for defect-free deformation. By employing the proposed method, two meso-forming processes, viz., four steps extrusion and backward extrusion, are proposed to fabricate the designed part without folding defects. The applicability of the meso-forming processes for defect avoidance is verified by numerical simulation and physical experiment. The experiments also corroborate the findings of finite element simulations. On the other hand, the proposed feature-based method is further verified by the effectiveness of the generated two meso-forming processes for their efficiency in forming of the meso-scaled part without the flow-induced defects.

Description: Five-axis machining is more widely used in manufacturing of freeform surfaces. However, in five-axis machining of freeform surfaces, incomplete information exchange between computer numerical control (CNC) and computer-aided design/computer-aided manufacturing (CAM) results in many limitations need to be rectified. In the paper, a new structure of CNC based on STEP-NC standard is proposed, where tool path planning, tool offset, and inverse kinematics are transferred from CAM to CNC. In order to guarantee good openness, open platform and standard interface are applied in the development. Technology of module collaboration and design of data flow are studied. A five-axis real-time interpolator for non-uniform rational B-spline surfaces machining is realized. Based on these technologies, a five-axis CNC is developed in the manner of software realization, which consists of interpreter, task coordinator, axis group, softPLC, etc. The software CNC system has been applied on a tilt-rotary type five-axis machine tool, where the milling experiment has been performed successfully.

Description: A solid trimming method is proposed to determine cutter–workpiece engagement (CWE) maps, which are essential to investigate cutting forces, machining errors, and chatter stability in multi-axis milling. In this method, CWE maps, defined as the instantaneous contact area from the cutting flutes’ entrance to exit, are extracted by trimming the removal volume (RV) with the feasible contact surfaces. Compared to the traditional Boolean operation approach, the trimming method extracts CWE maps without the requirement of abundant surface/surface intersection operations. Moreover, instead of using the union solid model associated with all cutter locations, RV is calculated for the first time by introducing the existing concept of analytical tool swept volume, which is previously limited to tool path planning. Verification tests show that the proposed method has the advantages of high accuracy and efficiency.

Description: One of the industrial applications of computer vision is the automated detection and characterisation of surface defects. Some types of surface, such as those that are highly reflective or transparent, require the implementation of custom-made systems for automated inspections. The purpose of this article is to present a machine vision system, with an easily configurable hardware–software structure, for surface quality inspection of transparent parts. This structure permits that different products and part models may be inspected by the system. Its hardware is composed of image-capturing devices and mechanisms for manipulating and holding the part to be inspected. One such mechanism is the lighting system, which has been specifically developed to allow real-time quality control of this type of surfaces. As regards software design, a component-based approach has been adopted in order to increase reusage of the code and decrease the time required for configuring any type of part and adapting it for inspection. To test the efficiency and robustness of the industrial setup, a series of tests using a transparent industrial part, specifically, a commercial model of headlamp lens, have been assessed.

Description: Part II of the present study is a comparative study of high-speed machining of Ti-6Al-4V and Inconel 718, focusing on a comparison between the effects of dynamic tool edge wear on cutting vibrations. This paper describes in detail how cutting vibrations were measured and how vibration signals were processed using a wavelet packet transform technique. A total of 60 high-speed machining experiments were performed, covering a range of cutting speed and feed rate conditions. The experimental results show that tool edge wear has a complex effect on the cutting vibrations. The vibration amplitudes in high-speed machining of Ti-6Al-4V can be higher or lower than those in high-speed machining of Inconel 718, depending on the particular cutting speed and feed rate employed. Analysis of variance reveals that both the cutting speed and the feed rate always play a statistically significant role in affecting the vibration amplitudes in all three directions, i.e., the cutting speed direction, the feed rate direction, and the depth of cut direction. It is also revealed that in high-speed machining of Ti-6Al-4V, four significant wavelet packets (W30, W32, W33, and W36) exist, depending on the particular cutting conditions employed. In high-speed machining of Inconel 718, two significant wavelet packets (W32 and W33) exist, regardless of the cutting conditions employed. The significant wavelet packets identified in part II of the present study can be used as features to detect and monitor tool edge wear in high-speed machining.

Description: FGH95 is one kind of powder metallurgy (PM) superalloy which has excellent mechanical properties at high temperature. It has been developed for turbine disc applications to improve aeroengine efficiency under higher operating temperatures. However, this kind of superalloy is very difficult to machine because of its poor thermal diffusivity and work-hardening properties during the machining process. The machining process can lead to damage of the machined surface and subsurface. Thus, the purpose of this paper was to investigate damage of the machined surface and subsurface in hard machining of FGH95 PM superalloy. Orthogonal milling experiments using coated carbide inserts were carried out on a CNC machining center. The machined surface was observed and recorded using an optical microscope, white light interferometer, and scanning electron microscope. Machined surface defects were recorded and analyzed. The effects of cutting speed on machined surface roughness, white layer thickness, plastic deformation, and microhardness were investigated. The research results show that better surface roughness can be generated at higher cutting speeds, while several defects appeared on the FGH95 machined surface. White layer thickness and machined surface microhardness increase with the cutting speed. Also, plastic shear strain in the machined surface layer increases with cutting speed. The depth of plastic deformation decreases with the increase of cutting speed. These investigation results are essential for the evaluation of PM superalloy surface integrity and are significant for the prediction of PM superalloy service life.

Description: Electrochemical machining (ECM) is well-established in certain areas, such as the aerospace, defence, and medical industries for machining complex parts. ECM is an effective way to produce compression blades. However, with advances in the development of aero engines, the accuracy of blades becomes higher and their shapes have also become more complex. Thus, considerable attention has been devoted to improving the machining accuracy of blades by ECM. In blades machined by ECM, the angle between the cathode feeding directions and the normal of the anode profile greatly affects the accuracy of the ECM process, and it is determined by the angle combination of the anode installation and the cathodes feeding direction. It is very important to determine the best angle combinations that could minimise the angle between the cathode feeding directions and the normal of the anode profile. The present paper focuses on the optimization method of the angle combinations of the cathode feeding directions and anode installation. A theoretical model describing the optimization method of the cathode feeding directions and position of the anode was developed, and the experimental investigations were conducted in order to evaluate the rationality of the optimization method. The results show that with the optimized combination of the cathode feeding directions and position of the anode, the maximum angle between the cathodes feeding directions and the normal of the anode profile is minimised and the inter-electrode gap between the cathode and anode is more uniform. Thus, the machining accuracy could be clearly improved and the maximum errors of the convex part and concave part were only 0.054 and 0.047 mm, respectively.

Description: As a strongly NP-hard problem, the hybrid flow-shop problem with multiprocessor tasks (HFSPMT) has gained increasing attention due to its academic significance and application value. In this paper, an effective algorithm based on the shuffled frog leaping algorithm (SFLA) is proposed for solving the HFSPMT. First, three decoding methods are used together to decode a solution to a better schedule. Especially, the forward scheduling decoding method is employed, aiming at narrowing the idle time between consecutive operations in the processor as well as increasing the flexibility in selecting processors to schedule the following operations. Second, a bilevel crossover is designed to make each individual share the good “meme” within each memeplex and exchange the good “meme” between different memeplexes. Third, multiple local search operators are used in an effective way by employing the meta-Lamarckian learning strategy to enhance the local exploitation ability. Meanwhile, the use of crossover and local search together in the SFLA can enrich the memetic search behavior and balance the exploration and exploitation abilities. In addition, the effect of parameter setting of the algorithm is investigated based on the Taguchi method of design of experiment, and suitable values are suggested for the parameters. Extensive testing results based on two types of well-known benchmarks are provided. And the effectiveness of the proposed algorithm is demonstrated by the comparisons with some existing algorithms.

Description: The use of composite parts, especially in aeronautics, is increasing at an exponential rate. However, machining of this material is complicated due to different phenomena such as delamination, burned resin, and cutting edge failure. The aim of the present study is to introduce a new method for optimizing cutting conditions, using a correlation between vibration and machining defects. Down milling of a carbon/epoxy composite material with a single polycrystalline diamond insert was performed. To minimize the number of experiments, a central composite design with 20 combinations was studied, using parameters such as cutting speed, depth of cut, and feed rate. Vibration levels were measured for each cutting condition. Results obtained from the analysis of variance confirm that the mathematical models used in this study could adequately describe the performance indicators. A vibration criterion was defined to describe the regions with and without defects of the machining. This technique validated through testing should help the operator to choose the optimal cutting conditions.

Description: Sheet metal parts are widely used in various industry branches. The flat pattern development of sheet metal components is a prerequisite for sheet metal fabrication. The conventional graphic solution or the analytical method carried out manually is laborious, time-consuming, and lacks accuracy. The feature-based flattening could help to achieve the objective of automatic pattern generation; however, it is only suitable for bend formable sheet metal components composed of flat and simple curved surface. Inspired by its wide applications in cloth and shoemaking industries, the energy-based flattening for mesh surface is then introduced into the flat pattern derivation of sheet metal parts in this paper. A simplified energy model is proposed as our physical model. An innovative energy relaxation process based on variable step size is introduced to promote efficiency. Some key issues like seed triangle selection and overlap correction are also concerned. For those complex surfaces, a hierarchy flattening methodology is proposed to release the flattened distortions. A comparison between the energy method and the classic as-rigid-as-possible mesh parameterization is made to show the effectiveness of our method. The numerical experimental results show that the energy-based flattening method is a practical, intelligent, and automatic approach for flat pattern generation of sheet metal components.

Description: The capabilities of additive manufacturing technologies to fabricate multi-material structures have been investigated in many studies. However, only a few of the technologies have been used to fabricate products for direct application. The full development of the capability will enable the fabrication of innovative engineering structures consisting of function-specific material members that cannot be realized using conventional methods. In this work, a methodology for fabricating dual-material engineering structures using ultrasonic additive manufacturing (UAM) was developed. An example structure consisting of members designed to carry tension and compression loads were fabricated using composite materials and Al 3003 matrix material respectively. MetPreg®/Al 3003 and Ti/Al 3003 composite materials were respectively used as tension members in two different structure samples. Single-material copies of the dual-material structures were fabricated using Al 3003 for load-carrying capability comparison. The results of the load tests carried out shows that the dual-material structures could withstand much higher loads than similar structures entirely made of the matrix Al 3003 material. This is an indication that UAM can be effectively used to fabricate multi-material engineering structures.

Description: A method is described in this paper for measuring the spindle rotation error and a technique for separating the eccentric error caused by setup error of the master cylinder. The system consists of two non-contact capacitance sensors used to measure the radial displacement of the rotating master cylinder and an LMS Test.Lab used to collect the measurement data. LMS Test.Lab offers a complete engineering solution for rotating machinery. Based on our experimental research, it indicates that this system can be used to measuring the spindle rotary error at different speeds. It is also verified the feasibility of the error separation methods developed in this paper.

Description: This paper investigates a products and vehicles scheduling problem in a two-stage supply chain environment, where jobs first need to be processed on the serial batching machines of multiple manufacturers distributed in various geographic zones and then transported by vehicles to a customer for further processing. The size and processing time of jobs are varying with the difference of types, and each batch takes a setup time before being processed. The problem of minimizing the makespan is formalized as a mixed integer programming model and proved to be NP-hard. In addition, the structural properties and lower bound of the problem are analyzed and inferred. Then a modified gravitational search algorithm (MGSA) is proposed to solve the problem. In the developed MGSA, several improvement strategies and the batching mechanism DP-H are introduced. The effectiveness and efficiency of the proposed MGSA are demonstrated and compared with a particle swarm optimization (PSO) algorithm and a genetic algorithm (GA). Besides, the error ratios between the lower bound and the best found solutions are reported. The experimental results indicate that the proposed MGSA is more robust and outperforms PSO and GA on the studied two-stage supply chain scheduling problem.

Description: Supply chain network design is one of the most important issues in designing supply chains because of its effect on performance and efficiency of the logistics network. Customer service improvements and environmental requirements have forced most companies to take into account the reverse flows in designing their supply chain networks. This paper employs an interactive fuzzy multi-objective linear programming (IFMOLP) method to solve fuzzy bi-objective reverse logistics network design problems. This method attempts to minimize the total cost and total delivery time of the system simultaneously. The presented method provides decision makers with an interactive framework that facilitates the process of decision making in a fuzzy environment. Moreover, this framework enables the decision makers to interactively change fuzzy data in order to reach the most satisfactory solutions. A genetic-based heuristic algorithm is presented to solve the model for larger cases. A case study in a bread-producing factory is presented to show the feasibility of the proposed approach.

Description: In this paper, the ultrasonic vibration-assisted grinding is studied, and a new method is provided to solve the problem of matching the machine tool system and the ultrasonic system. By establishing the matching model, this problem is theoretically solved optimally. Moreover, the abrasive grain motion equations, the removal rate model, and grinding force prediction model are presented. Then the grinding force and the processing quality in system matching are researched by numerical simulation. When ultrasonic system parameters exceed the critical value, the surface scallop height of workpiece becomes lower with single-grain track and intergranular track overlapping. The grinding force decreases as the spindle speed, vibration amplitude, and vibration frequency increase. And the grinding force increases as the grinding depth and feed rate increase. Thus, the surface morphology of the workpiece and the change trends of the grinding force can be predicted through the system matching model. As a result, the best ultrasonic equipment can be decided accordingly to cooperate with the machine tool for grinding.

Description: Lot streaming means breaking a lot into sublots, where sublots may be transferred to a number of machines for the operations. Here, the multi-job lot streaming problem in a multistage hybrid flow shop having identical parallel machines at stages with work-in-process (WIP) jobs, work shifts constraint, and sequence-dependent setup times is studied. The aim is to minimize the sum of weighted completion times of jobs in each shift in order to furnish a better machine utilization for the following shifts. Our model in meeting the job demands appropriates job scheduling on machines for processing, the sequence of operations on allocated machines, the size of the sublots in the work shifts, the work completion times in all the shifts, and the jobs in each stage as the WIP jobs. To solve the problem, a genetic algorithm (GA) and simulated annealing (SA) are proposed to compute the best scheduling for the hybrid flow shop problem. Numerical illustrations demonstrate the applicability of the proposed model and the effectiveness of the GA.

Description: The increasing demand for high-performance and quality polymer composite materials has led to international research effort on pursuing advanced tooling design and new processing technologies to satisfy the highly specialized requirements of composite components used in the aerospace industry. This paper reports the problems in the fabrication of advanced composite materials identified through literature survey, and an investigation carried out by the authors about the composite manufacturing status in China’s aerospace industry. Current tooling design technologies use tooling materials which cannot match the thermal expansion coefficient of composite parts, and hardly consider the calibration of tooling surface. Current autoclave curing technologies cannot ensure high accuracy of large composite materials because of the wide range of temperature gradients and long curing cycles. It has been identified that microwave curing has the potential to solve those problems. The proposed technologies for the manufacturing of fiber-reinforced polymer composite materials include the design of tooling using anisotropy composite materials with characteristics for compensating part deformation during forming process, and vacuum-pressure microwave curing technology. Those technologies are mainly for ensuring the high accuracy of anisotropic composite parts in aerospace applications with large size (both in length and thickness) and complex shapes. Experiments have been carried out in this on-going research project and the results have been verified with engineering applications in one of the project collaborating companies.

Description: Thread cutting is a form of cutting process, and during the process, energy is transferred into the workpiece by the tool that generates the surface layer of the threaded part. Cutting conditions are heavier in thread cutting than cylindrical side cutting operations, and energy consumption is more important at the thread root during thread cutting. Total cutting energy is mainly affected by cutting forces and cutting velocity. Variation of cutting forces, chip thickness ratios, and shear angles in thread machining were investigated. Effects of the thread height and tool wear on the chip compression ratio were determined experimentally. Main cutting forces at the thread root were calculated by using Zorev’s force calculation approach to evaluate the cutting power and specific cutting energy during thread cutting process. Fatigue strengths of threaded specimens produced by machining were evaluated depending on the cutting power and specific cutting energy at the thread root. It is observed from the experimental results that when specific cutting energy is increased, fatigue strengths of the threaded specimens are also increased significantly, while cutting velocity and chip thickness are kept constant in the specified range.

Description: Recent research has indicated that the use of multi-radius femoral heads can be advantageous in terms of the articulating zone lubrication and tribological performance for metal-on-metal (MoM) hip implants. The emergence of this multi-radius femoral head is a new challenge in manufacturing research because conventional machining technologies are not normally agile enough to realize high-accuracy machining of the new design of femoral heads. This paper attempts to demonstrate the manufacture of a multi-radius femoral head from a typical single radius femoral head using a bonnet polishing method. The sample used in this investigation is an 18-mm radius cobalt chrome (CoCr) alloy, the most common material for MoM hip prostheses. The paper outlines the process of producing a target of 19-mm radius zone in the articulating region. Post polishing measurement of the radius of the articulating zone showed the radius to be between 18.98 and 19.017 mm. Additionally, the peak-to-valley (PV) value of the spherical error map was reduced from 103 to 1.36 μm and root mean square (RMS) was from 29.65 to 0.318 μm. The machined surface roughness obtained through the process was Sa = 16.1 nm which is well within the recommendation of ISO7206-2:2011 standard for metal hip joint prosthesis value of 50 nm. The experimental result confirms that bonnet polishing is a potentially viable choice to finish the new design multi-radius femoral heads systems.

Description: The challenge in the milling of freeform surfaces lies in the enhancement of surface quality as well as the reduction of production time and cost. Freeform surface milling processes have been analysed and contrasted, to identify and quantify the decisive factors that significantly influence the productivity and the workpiece quality. The focus has been on monitoring, simulating and quantifying error sources which affect the manufacturing accuracy. The error sources have been separately examined and modelled so as to assign their proportional impact on product quality. The impact of the interpolation method on the tool path accuracy has been analysed, the dynamic behaviour has been simulated, and the CNC process data and the process forces have been monitored. The monitored and measured data have been synchronized in the time domain for each experimental freeform surface milling process and used as input for geometric machining simulations. To evaluate the virtual machining approach, the quality of the virtual products obtained has been compared to the quality of the real products. Furthermore, the proportion of each considered error source could be related to the deviations measured in particular regions of the machined surface.

Description: This paper presents for the first time the concept of measurement assisted assembly (MAA) and outlines the research priorities of the realisation of this concept in the industry. MAA denotes a paradigm shift in assembly for high value and complex products and encompasses the development and use of novel metrology processes for the holistic integration and capability enhancement of key assembly and ancillary processes. A complete framework for MAA is detailed showing how this can facilitate a step change in assembly process capability and efficiency for large and complex products, such as airframes, where traditional assembly processes exhibit the requirement for rectification and rework, use inflexible tooling and are largely manual, resulting in cost and cycle time pressures. The concept of MAA encompasses a range of innovative measurement-assisted processes which enable rapid part-to-part assembly, increased use of flexible automation, traceable quality assurance and control, reduced structure weight and improved levels of precision across the dimensional scales. A full scale industrial trial of MAA technologies has been carried out on an experimental aircraft wing demonstrating the viability of the approach while studies within 140 smaller companies have highlighted the need for better adoption of existing process capability and quality control standards. The identified research priorities for MAA include the development of both frameless and tooling embedded automated metrology networks. Other research priorities relate to the development of integrated dimensional variation management, thermal compensation algorithms as well as measurement planning and inspection of algorithms linking design to measurement and process planning.

Description: The single-layer superabrasive wheels are made by joining all abrasive grains onto the wheel hub through electroplating or brazing processes. Recently, the attention has risen to acquire a better grinding quality through more stringent grain size control. It is found that any small deviation in the grain dimensional distribution will result in considerable difference in the grinding quality. Therefore, the understanding on correlation between the grain dimensional deviations with the wheel performances will be critical, and the primary step is to establish the correlation between the critical wheel design parameters with the wheel topographical features. In this paper, the ‘through-the-process’ grinding wheel model is developed for single-layer electroplated cubic boron nitride (CBN) wheels by simulating each wheel fabrication procedure, numerically. The efficacy of the wheel model is verified by comparing simulation results with the experimental measurement data in terms of the static grain count and grain protrusion height distribution, and further analysis of the intrinsic relationship between the grain dimensional distribution and the wheel surface topographical properties is carried out so as to provide the quantitative basis for grinding wheel quality control and optimal abrasive product design.

Description: Remanufacturing is the only way for sustainable development of mechanical equipment manufacturing. For remanufacturing blanks containing cracks, the primary task is the prevention of crack propagation to ensure effectiveness of the manufacturing processes to follow. When pulsed current passes through a specimen, due to the existence of crack, the temperature around the crack tips rises sharply and may even climb above the fusion point of the material, which causes the crack tip to become blunt. In this work, with compressor rotor blade material FV520B as a specimen, the distributions of current density, temperature field, and stress field are calculated at the instant of discharge based on the thermo-electro-structure coupled theory. The crack arrest experiment is performed on high pulsed current discharge device of type HCPD-I. By making comparisons of morphology, microstructure, and size of fusion zone and heat-affected zone (HAZ) around the crack tip before and after energizing, the relationships between the sizes of fusion zone and the HAZ and the discharge energy and the current path are derived. The obvious partition and refined grains around the crack tip are prominent because of violent temperature change. The experimental and simulation results are found in fine agreement. The high current pulsed discharge can be used effectively to prevent a crack to further expand and show substantial potentials for application in remanufacturing domain.

Description: Parts backorder reduction has become increasingly important in supply chain management. When it is difficult or time consuming to acquire parts, the operational availability of a system is reduced. This study describes a technique that helps planners proactively identify potential problem spare parts to better manage spare parts acquisition in military weapon systems. The paper reports on the results of fuzzy induced linguistic ordered weighted averaging for group decision support evaluation of backorder risk triggers to ensure that equipment is available and fully operational when needed. Risk factors were identified, the impact importance and probability metric performance ratings were determined via induced linguistic ordered weighted averaging, and a risk mitigation strategy was used to identify and predict supply chain backorder risk triggers (SCBORT). L-Project is an illustrative example that utilizes Petri nets and Pareto charts to present the evaluation hierarchy of supply chain risk. Cluster analysis is utilized to determine that there are five triggers of engineering, obsolescence, demand, NSN unique sustainment, and cataloging in light of the five SCBORT probability performance metric dimensions of quality, cost, lead time, service level, and information availability. There are also four aggregated SCBORT impact clusters of market sensitiveness, process integration, information drivers, and flexibility. Supply chain risk is presented as a probability/impact matrix.

Description: Ti-6Al-4V is widely used in industry because of its high strength-to-weight ratio at elevated temperatures, its excellent resistance to fracture and corrosion, and biological properties. However, Ti-6Al-4V is classified as hard-to-cut material because of its high chemical reactivity with most tool materials and its low thermal conductivity that causes high temperature on the tool face. Consequently, prediction of the tool temperature distribution has great significance in predicting tool wear pattern. In this research, finite element method (FEM) is employed to conduct numerical investigation of the effects of cutting conditions (cutting speed, feed rate, and axial depth of cut) in corner up milling on temperature of the tool rake face. The tool material used is general carbide, and the behavior of the workpiece Ti-6Al-4V is described by using Johnson-Cook plastic model. Because of the computational expense, a separate heat transfer model is built to analyze the heat transfer process after the tooth disengages the workpiece and before it engages the workpiece again to predict change of temperature distribution during this cooling process while subjected to different cooling schemes. This research provides helpful guidance for selecting optimal cutting conditions and tool cooling strategies in up milling Ti-6Al-4V alloy.

Description: In micro-ultrasonic machining (MUSM), a major part of the material is removed by the impact of abrasive particles. In the early stage of machining, abrasive particles are distributed uniformly in the machining area. However, as the process goes on, abrasive particles will be driven out of the machining area owing to the ultrasonic vibration of the micro-tool or work-piece and the rotation of the micro-tool in the fluid. As a result, the machining precision and machining efficiency will be reduced. In this paper, we propose a new method called electrophoretically assisted micro-ultrasonic machining (EPAMUSM) in which an electric field is used to prevent the abrasive particles from being driven out of the machining area. Experiments on EPAMUSM are conducted using a self-developed micro-USM system with micro-tool vibration, in which the control system of the micro-USM machine tool controls the machining force in a constant range. First, experiments comparing micro-ultrasonic machining with and without electrophoretic assistance are conducted. It is found that, with the appropriate processing parameters, EPAMUSM can improve machining accuracy and machining efficiency. Then, experiments with an orthogonal design are performed to reveal the main effects of the process parameters (abrasive particle size, spindle speed, DC voltage, force, ultrasonic power, mass fraction, and feed rate) on the material removal rate, and the optimal processing parameters are derived from the results.

Description: Fused deposition modelling (FDM) is an additive manufacturing technique deployed to fabricate the functional components leading to shorter product development times with less human intervention. Typical characteristics such as surface roughness, mechanical strength and dimensional accuracy are found to influence the wear strength of FDM fabricated components. It would be useful to determine an explicit numerical model to describe the correlation between various output process parameters and input parameters. In this paper, we have proposed an improved approach of multi-gene genetic programming (Im-MGGP) to formulate the functional relationship between wear strength and input process variables of the FDM process. It was found that the improved approach performs better than MGGP, SVR and ANN models and is able to generalise wear strength of the FDM prototype satisfactorily. Further, sensitivity and parametric analysis is conducted to study the influence of each input variable on the wear strength of the FDM fabricated components. It was found that the input parameter, air gap, has the maximum influence on the wear strength of the FDM fabricated component.

Description: Assembly modeling and simulation are two important activities in product development. The former makes an assembly model by specifying mating constraints between parts. The latter visually simulates the process of forming an assembly model through sequencing and finding paths of parts. In practice applications, the sequence of assembling parts in assembly modeling cannot be directly utilized to facilitate path finding and sequencing in assembly simulation, and specifying mating constraints in assembly modeling and finding/sequencing paths of parts in assembly simulation are usually accomplished manually, which are tedious and error-prone. One responsible reason is that when creating part models, designers know how they will interact with each other, but this information is not stored in part models. To alleviate the problems, this paper introduced the concept of assembly feature pair (AFP) and proposed a framework method to integrate assembly modeling and simulation. An AFP consists of form feature pairs on two parts together with assembly behaviors. Correspondingly, the mating constraints between parts and the information of assembly process can be captured to facilitate assembly modeling and assembly simulation. Based on AFP, the framework method can integrate assembly modeling and simulation from three aspects: (1) AFPs will be embedded into part models at part modeling stage, storing designers’ knowledge of how parts will interact with each other, (2) the laborious work of applying mating constraints between parts in assembly modeling will be replaced by instantiating the embedded AFP in part models, and the instantiation sequence of AFPs will be directly used in assembly simulation, and (3) the manual work of planning and sequencing paths of parts in assembly simulation will also be replaced by instantiating the embedded AFP in part models based on the randomized motion planning theory. To demonstrate the theoretical framework, an implementation sample was presented.

Description: A numerical study of the laser welding process is presented. The numerical model is based on a combination of the enthalpy method and the finite difference techniques applied to the heat equation that can bypass the manual enforcement of the jump condition at the phase-separating surfaces. Minimal application of the “life and death of elements techniques” is required in order for the dynamics of the keyhole to be captured. This analysis results in the construction of the flowchart of a time-stepping algorithm, suitable for any software platform or computer language.

Description: This research considers an open shop scheduling problem with preventive maintenance. A specific level of reliability is assumed and a mathematical model is presented to schedule both production and maintenance tasks, simultaneously. Three different and conflicting objective functions containing machine availability, make-span, and total tardiness and earliness have been optimized in the proposed model. When there are more than two machines in the open shop problem, it is classified in the category of NP-hard problems. Consequently, classical approaches cannot reach to an optimal solution in a reasonable time. Thus, two well-known algorithms for multi-objective problems containing non-dominated sorting genetic algorithm-II (NSGA-II) and multi-objective particle swarm optimization (MOPSO) are developed to find the best near-optimal solutions. The surface response methodology (RSM) is applied to tune parameters of the developed algorithms. Then, the reliabilities of the presented algorithms are illustrated based on three evaluation metrics comprising the number of Pareto solutions, spacing, and diversity. Furthermore, the superiority of the proposed algorithms is shown through benchmarking approach. The algorithms may be used in other open shop problems because they are able to find the best and reliable near-optimal solutions in a reasonable processing time.

Description: In this paper, we simultaneously consider the scheduling and tool loading problems in flexible manufacturing systems. There are various jobs that must be processed on a number of parallel computer numerical control machines. The processing of each job requires a set of machine tools. However, the number of tool copies available in the system is limited due to economic restrictions. The problem, therefore, is to schedule the jobs and the required tools in such a way that the makespan is minimized. We present a time-indexed mathematical model of the problem. A heuristic approach based on the mathematical model is also developed and the computational results are presented. The goal of this study is to develop a new approach for simultaneously scheduling the jobs and loading the tools in flexible manufacturing systems and benefit from the advantages of time-indexed modelling.

Description: In today’s studies, it is observed that spur gears can be manufactured by vertical-spindle CNC milling machines unlike conventional manufacturing methods. To this end, two different approaches have been developed, which are vertical and axial manufacturing methods. In this study, concave-convex gear wheels are the first time correctly manufactured by using the vertical cutting method. The manufacture time of these gears are determined. This time is compared with spur gear manufacturing time which they manufactured by conventional machines. When these gears are manufactured, the parametric equations of involute curve are formed in order to create the 3D model required for manufacturing concave-convex gear wheels. 3D model is created based on these equations and the manufacturing program is written. The manufacturing times are calculated by manufacturing these gears based on various parameters such as the module, number of teeth, tooth width, depth of cut, and cutting angle of the gear. The size of the manufactured gears has been identified. Then, the measured values were found to be consistent with the calculated values. It is detected that the manufacturing times increase along with the increase of module values as well as increasing number of teeth and cutting angle.

Description: Multiple parts process planning (MPPP) is a hard optimization problem that requires the rigor and intensity of metaheuristic-based algorithms such as simulated annealing and genetic algorithms. In this paper, a solution method for this problem is developed based on genetic algorithms. Genetic algorithms solve problems by exploring a given search space. To do this, a landscape over which the search traverses is constructed based on a number of algorithm choices. Key algorithm choices include (a) type of chromosome representation, which affects the efficiency of an algorithm, and (b) type and form of genetic operators, which affect the effectiveness of an algorithm. More specifically, the suitability of a variable-length chromosome (VLC) representation for encoding a solution to a MPPP problem is investigated. The effectiveness and efficiency of implementing the VLC algorithm is analyzed and compared with: (a) the commonly used fixed-length chromosome representation, (b) a variant of the simulated annealing algorithm, and (c) a knowledge-informed simulated annealing algorithm. The scalability of the algorithms is analyzed and their effectiveness demonstrated by experimental results based on four problem sizes. Obtained results show that, although there are variances in performances, all algorithms investigated are capable of obtaining good solutions. In addition, variances were observed for different aspects of the MPPP problem. The results indicate that the VLC algorithm is effective in solving MPPP problems that consider multiple aspects in the search for optimal process planning solutions.

Description: In mechanical lapping, diamond exhibits a highly anisotropic tribological behavior. The dependency of wear rate on crystal orientation has long been noticed by diamond polishers. However, in the diamond manufacturing, the surface quality is another side in need of attention. In this paper, the relationship between surface morphology and crystallographic orientation under a certain lapping condition was examined. It is found that a fine surface can still be obtained at the directions that deviate a lot from the “soft” directions (near 〈001〉 crystal direction for {110} surface). But, with respect to the “hard” directions (near 〈110〉 crystal direction for {110} surface), a bad surface finish with a fracture appears. This result comes down to two aspects. First, on {110} surface, as the lapping direction from the 〈001〉 (soft direction) approaches 〈110〉 (hard direction) the phase change of diamond carbon atoms gets more difficult, which causes the depth of the amorphization layer becomes thinner. Second, the energy required by diamond amorphization is lower than that by surface fracture around the soft direction, while near the hard direction, the contrary is the case. Our work provides a further understanding of the diamond tribological properties.

Description: Hybrid laser gas metal arc (GMA) welding can provide higher productivity than either autogenous laser welding or GMA welding alone. In order to further enhance the welding efficiency of the hybrid laser arc welding process, a novel triple-heat-source welding system entitled hybrid laser double GMA welding was proposed in this study. This hybrid welding system was established based on a double GMA welding and laser welding system. During the hybrid welding process, two consumable electrodes kept alternative arcing at relatively low welding current while they changed to arc synchronically at relatively high welding current. This research is mainly focused on the mechanism of the alternative arcing phenomena and the influences of wire feed speed and laser beam on the arc alternating process. It was found that the arcing period decreased with the increase of wire feed speed which was positively correlated with the welding current. The arcing period also decreased with the introduction of the laser beam into the arc welding system. The arcing period can be decreased as short as possible until it was equal to the pulse period of the welding power source. Based on the analysis of the driving forces acting within the molten weld pool, it can be inferred that the hybrid laser double GMA welding process could be in favor of homogeneous alloying elements distribution and weld metal microstructure.

Description: In the process of curved surface polishing and buffing, the tools have to be compressed on the workpiece and moved to wear the surface, so the normal force and tangential feed movements should be provided and controlled synchronously. It is a typical kind of compliant control, which would most likely be done under the hybrid motion/force control policy. Although its related theory is already almost perfect, this method could seldom be used in the process of curved surface polishing and buffing, if ever, for it is always not easy to orthogonalize force control space from movement control space. In this paper, a force control subsystem is developed and fixed on a computer numerical control (CNC) lathe to control the normal force independently, and the normal force control space is orthogonalized from the feed movement control space by geometry defining for aspheric surface polishing. Furthermore, the orthogonalization in the domain of time is taken to make the force control not to interpolate with the displacement control of the feed movements. Experiments in controlling and polishing the normal force show that the hybrid motion/force control policy could be used in the process of aspheric surface polishing and buffing by keeping the normal force control and feed movement control independently in both domains of space and time.

Description: Electroplating and electrochemical corrosion testing techniques are commonly used manufacturing processes for corrosion prevention and corrosion characterisation. However, the influence of electroplated coating thickness on corrosion has not received adequate attention. In this work, the effect of coating thickness on corrosion behaviour of electroplated zinc coating on copper substrate is studied. Inductively coupled plasma mass spectroscopy (ICPMS) coupled with potentiodynamic and potentiostatic polarisation measurements showed that enhanced corrosion resistance can be achieved by reducing the thickness of the zinc coating during electroplating. The increased resistance to corrosion with reduction in coating thickness is attributed to electromigration phenomenon, which is not often considered in electroplating work, but nonetheless can have significant consequences not only with regard to performance of electroplated materials but also during electrochemical analysis of corrosion.

Description: This study introduces a novel cross-generation automation transportation system (ATS) model to implement production manufacturing systems in the thin-film-transistor liquid-crystal-display (TFT-LCD) industry. The proposed cross-generation ATS model describes the construction of each generation system to implement production requirements and follow a fixed cycle. The extent to which automation associated with technological upgrading can led to the full implementation of automated production has become increasingly important in production manufacturing strategy. Implementation of ATS has evolved from an early traditional thinking model to a human-oriented production process, i.e., a fully automated system that integrates planning with thinking. Therefore, this study focuses on cross-generational data collected from company operations to examine the feasibility of implementing cross-generation ATS in the production manufacturing system patterns of the conventionally used thinking model.

Description: Electrochemical micromachining (μECM) is a non-conventional machining process based on the phenomenon of electrolysis. μECM became an attractive area of research due to the fact that this process does not create any defective layer after machining and that there is a growing demand for better surface integrity on different micro applications including microfluidics systems, stress-free drilled holes in automotive and aerospace manufacturing with complex shapes, etc. This work presents the design of a next generation μECM machine for the automotive, aerospace, medical and metrology sectors. It has three axes of motion ( X , Y , Z ) and a spindle allowing the tool-electrode to rotate during machining. The linear slides for each axis use air bearings with linear DC brushless motors and 2-nm resolution encoders for ultra precise motion. The control system is based on the Power PMAC motion controller from Delta Tau. The electrolyte tank is located at the rear of the machine and allows the electrolyte to be changed quickly. This machine features two process control algorithms: fuzzy logic control and adaptive feed rate. A self-developed pulse generator has been mounted and interfaced with the machine and a wire ECM grinding device has been added. The pulse generator has the possibility to reverse the pulse polarity for on-line tool fabrication.

Description: The electromagnetic sheet forming process for aluminum alloy sheets was studied experimentally and numerically with a rectangular helical coil actuator. The widely used planar spiral coils are associated with a low magnetic pressure at their center that imposes limitations on the shapes of sheet products. In order to generate a relatively uniform magnetic pressure, a rectangular helical coil is introduced with parallel wires covering the working area uniformly. Two approaches were used for the analysis. In the analytical modeling approach, the analytical expression for the magnetic pressure was obtained, assuming that the wires are equivalent to a current sheet. In the numerical modeling approach, a loosely coupled scheme was introduced to solve the electromagnetic and mechanical problems. The Maxwell equations were first solved for estimation of the magnetic pressure exerted on the workpiece ignoring any workpiece deformations. The magnetic pressure variation was then used as a boundary condition in the mechanical calculation for estimation of the deformation of the workpiece. For validation of the developed numerical model, a rectangular helical coil actuator was designed and tested to form a half ellipsoid with aluminum alloy sheets. The measured and predicted shapes of the half ellipsoid were compared. The effects of the coil design parameters for increasing the magnetic pressure are also discussed.