ALBERT

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.

Description: The machining process of plastic injection mold components is complex and continuously changing, and traditional practices rely on the experience and technique of professionals. In order to avoid the impact on business operations and losses, the geometric information of computer-aided design (CAD) systems should be converted into the manufacturing system required for computer-aided process planning (CAPP) and computer-aided manufacturing (CAM) systems through the integration of automatic feature recognition and group technology, thereby eliminating manual planning and shortening the planned lead time to realize CAD/CAPP/CAM integration and application. As part design is feature-based, each processing step can be regarded as a feature. This study applied hybrid recognition technology integrating the graph-based approach, rule-based approach, and hint-based approach to analyze and identify injection mold component shape features. Then, it established classification coding for data description according to the injection mold components before searching for the corresponding manufacturing processes in the database using the group technology. The case proved that the CAPP in this study could reduce about 90 % of the working time needed. It could accelerate the component planning process and integrate with the mold manufacturing scheduling to realize automated design and manufacturing.

Description: To develop an effective nondestructive evaluation method for the welding quality of the resistance spot welding, the electrode displacement signal during the resistance spot welding process is monitored, and the acquisition data of the signal are innovatively presented as the radar chart format. Some geometric features of the radar charts are extracted to reflect the welding quality. The decision tree classification technique is adopted to build a classifier and to provide a visible and intuitive diagnostic procedure for welding quality assessment. Test results of the decision tree classifier show that it is feasible and reliable to evaluate weld quality based on the graphics features of the radar chart. The features and the weld quality are closely related, and their extraction avoids complex algorithm. Meanwhile, when there are small samples, the decision tree classifier can identify good or bad weld accurately and rapidly, even though the weld is from an abnormal welding process, such as expulsion, current shunting, greasy surface, and small edge distance condition.

Description: An experimental investigation on laser transmission welding of polycarbonate is presented in this paper. Instead of concentrating on the well-known effects of process parameters, the present study focuses on the sensitivity analysis of process parameters to identify the critical parameters and to assess their relative impact on the variation in output quality. Curvilinear regression models are developed using the independently controllable design variables like laser power (W), welding speed (mm/s), standoff distance (mm), and clamp pressure (MPa). Selected weld quality characteristics, namely the weld strength (N/mm), which is calculated based on failure load per unit length and weld width (mm), are used to set the objective functions. Parametric sensitivity analyses are performed using the developed models. It is observed from the results of sensitivity analysis that the weld strength is more sensitive to welding speed (sensitivity of 8.4 N/mm per unit welding speed) and laser power (sensitivity of 3.08 N/mm per unit laser power), whereas weld width is more sensitive to welding speed (sensitivity of 0.37 mm per unit welding speed) and standoff distance (sensitivity of 0.11 mm per unit standoff distance), respectively. These are the critical parameters for the respective quality characteristics, and a small variation of these parameters causes relatively higher deviation in weld quality.

Description: Biocompatible nano oxide ceramics (TiO 2 , Al 2 O 3 , ZrO 2 and hydroxyapatite) were added for reinforcement of the biocompatible polymer (polyetherketone, polycaprolactone) matrix during a selective laser sintering (SLS) process of the porous tissue engineering scaffolds. The optimal regime comparison for laser sintering on CO 2 and Nd +3 :YAG lasers, strain estimation and an influence of post thermal annealing on mechanical characteristics were carried out. Results of a microstructural evaluation of the polymer-reinforced ceramic composites were conducted using the optical and scanning electron microscopy equipped with the energy-dispersive X-ray microanalysis and evaluated with results of the X-ray analysis. The observations showed that after the successful laser sintering, the increase of the nano ceramic particle sizes could be achieved by one to two orders. The study confirms the medical perspectives of the SLS-fabricated 3D porous composites.

Description: 3D rolling is a novel forming process for manufacturing 3D surface parts by employing a pair of forming rolls as a forming tool. By controlling the nonuniform distribution of roll gap of the forming rolls, residual stress of the sheet metal makes the sheet metal bend in the transverse and longitudinal directions simultaneously. As the roll adjusting radius is much larger than the target transverse curvature radius of the forming surface, the forming roll could rotate around its axis easily, which is suitable for producing 3D surface parts including the wide sheet metal with relatively small transversal curvature radius. In this paper, different roll adjusting radii are investigated for 3D surface parts, and the 3D rolling process has been improved to increase the length of effectively forming region of the forming parts and improve the utilization rate of sheet metal. Finite element analysis models are established; spherical and saddle surfaces are simulated. The corresponding experimental results are obtained. The dimensional accuracy of the forming part is measured, and the differences of the forming processes are analyzed by comparing the simulated results. The comparison and analysis of the forming results show the feasibility of the improved method of 3D rolling process for 3D surface parts.

Description: In this paper, a novel double-sided gas metal arc welding procedure was developed to weld 50 mm thick, low-alloy high-tensile steel. The good weld joint without visible flaws can be obtained. The microstructure and mechanical properties were investigated in detail. The results show that the base metal metallographic microstructure mainly consists of tempering lath martensite and a small amount of granular bainite. The fusion zone is mainly composed of acicular ferrite and lath martensite while the microstructure of the welded bead is composed of acicular ferrite and a small amount of granular bainite. The average hardness value of the welded bead (384.9 HV) is higher than the base metal (282.2 HV), but lower than the heat-affected zone. The average tensile strength of the welded specimens (862.73 MPa) reaches 98.04 % of the base metal (880 MPa). No crack produced when the samples have been bended to 180° and the welding joints all have better plastic property. The impact absorbing energies in FL + 2 mm and FL + 5 mm are higher than those in WC and FL. The fracture modes of WC and FL are cleavage fracture and those of FL + 2 mm and FL + 5 mm are ductile fracture. Consequently, the double-sided GMAW is a high-efficiency welding method without back chipping which has certain advantages and possibility in welding thick plates.

Description: The high temperature and grinding force in grind hardening induce workpiece distortion that increases the magnitude of grinding to make the workpiece concave. The workpiece distortion also affects the grinding force, grinding heat flux, and grind-hardening depth distribution. The paper uses FE thermo-mechanical coupling model to simulate the thermal distortion in plane grind-hardening. Workpiece distortion, stress, and strain at different moments are calculated out and analyzed for different workpiece sizes. The calculated workpiece distortion is verified through the measured workpiece contour and the hardening layer distribution by experiment.

Description: In order to solve the problem of low measurement efficiency of volumetric errors and predict the volumetric errors of CNC machine tools online, a new volumetric error modeling method based on information fusion technology is proposed in this paper, which was used for the volumetric error prediction of a two turntable five-axis machine tool. In order to fulfill the volumetric error modeling, the displacement variables, temperature variables, and cutting force variables were determined firstly, then the determined variables and the volumetric errors were measured and analyzed, and a volumetric error model was presented based on the determined variables. In order to optimize the parameters of the presented model, grey correlation analysis method is used for the second time prediction of the volumetric errors. Finally, the performance of the model was tested by an experiment. The result shows that the approximation ability of the model is very well, and the residual error is smaller than 2 μm. Comparing with conditional modeling methods, this method can be used in different types of machine tools with different operating conditions by regulating the weight matrix, and the robustness of the fusion model is improved.

Description: Electric arc cutting process parameters play a very significant role in determining the cutting effect. Sensitivity analysis can be utilized to identify the process parameters exerting the most influence on the cutting effect and to know the parameters that must be most carefully controlled. Experiment data analysis and finite element method are both introduced to carry out sensitivity analysis based on the response surface methodology. Changeable process parameters such as workpiece thickness, cutting current, and electrode diameter are used as design variables. Cutting hole geometry in experiment part is considered as the response, while the response for PDS is the simulation temperature value by finite element method. The results of two methods both show that a change in process parameters affects the cutting characteristics. The arc cutting process is most sensitive to the cutting current, less sensitive to electrode diameter, and least sensitive to workpiece thickness. It also reveals that experiment data analysis obtains the detail numerical results, and PDS gives an intuitive analysis result without much trial and error.

Description: Investment casting (IC) is traditionally used to produce high accuracy products, but the products gaining variable cross section, multidimensional, and unconstrained/constrained features make it hard to determine the tooling dimensions. Every individual stage in the investment casting process (ICP) also poses a potential and uncertain threat on the final part dimensions. In this article, a variable cross section, multidimensional and unconstrained/constrained part for IC, is designed and constructed. The dimensions of wax pattern and final casting part are measured by three-dimensional (3-D) laser scanning, and the inner cavity dimensions of the ceramic shell are measured by industrial computerized tomography (ICT). The dimensional changes and the change of shrinkage along with the dimensions in different processes are analyzed. Finally, the exponential relationship between shrinkage and dimension in the whole ICP is concluded, and the mechanisms of the dimensional changes are discussed. The conclusions can be used to guide the dimensional design of the die and the reworking of the wax pattern to reduce the trial-and-error procedures.

Description: Silicon nitride is a non-oxide ceramic that represents strong characteristics in high strength, abrasion resistance, corrosion resistance, and thermal shock resistance at high temperatures and that has been widely used in the industry. However, it also exhibits high levels of hardness and brittleness, and machining of silicon nitride is usually implemented using a diamond grinding process. This presents difficulties in machining due to increased machining cost and time, and a machining method to reduce these is needed. Current studies on an alternative approach to the problem have been focused on laser-assisted machining (LAM) methods that facilitate machining by softening a workpiece using a laser heat source. The advantages of a LAM process are decreases in tool wear and cutting force and reductions in catastrophic tool failures and the occurrence of chatter. In this study, a high-power diode laser (HPDL) is used as a heat source for machining of silicon nitride. Machining experiments were carried out using cubic boron nitride (CBN) tools. The proper laser power for the experiment was determined through thermal analysis. A back-and-forth laser-path preheating method was newly proposed to obtain sufficient temperature for softening the silicon nitride. Machining experiments were performed using back-and-forth method and insulation material for protecting heat. The machining of silicon nitride was performed successfully by a laser-assisted milling (LAMill) process using a CBN ball end-mill tool, which is stable at high temperatures. In the machining with applying three times of a back-and-forth laser-path preheating process, tool breakage and gas marks were not occurred at the 170 W for processing a depth of cut of 0.15 mm. It is expected that the results of machining experiments can be used to process the various shape of silicon nitride material.

Description: A computation model based on inverse receptance coupling method is presented in this paper aiming for obtaining the joint interface’s stiffness and damping properties using frequency response functions measured on assembled structures only. In the model, it is emphasized that the joint stiffness and damping should be modeled with frequency dependency. The model’s validity is checked both through finite element (FE) simulation and experimental analyses. In the FE simulation example, the computation model gives more accurate results with noise-free data. In the experimental example, where noise in the data is unavoidable, the computation model is explored further for its applicability in the real industrial environment. Results from applications of the computational model show that it is even capable of obtaining the joint interface stiffness and damping values over the structure’s resonance frequency. A viable process of predicting behaviors of workpiece with receptance coupling method through identifying the joint interface properties is presented in the end of the paper. The applicability of this computation model and the factors that influence the accuracy of the model are discussed in the end of the paper.

Description: Wire electrical discharge turning (WEDT) process is one of the emerging non-traditional machining processes for manufacture of micro- and axi-symmetric components. In WEDT process, material is removed by successive sparks that form craters. The material removal by crater formation is associated with energy supplied in the gap referred as discharge energy. This energy must be controlled for effective machining. In this paper, a model is proposed for predicting the crater diameter based on anode erosion. Finite element method (FEM) is used to simulate the crater for different plasma flushing efficiency. Effect of discharge energy developed in the gap, physio-thermal properties of the material are considered for modeling. The erosion energy required to form a crater is also evaluated using anode erosion model. The proposed models are validated by conducting WEDT experiments on high-tensile steel [AISI 4340]. The crater morphology is investigated by using images obtained from scanning electron microscope (SEM) and energy-dispersive X-ray analysis. The crater diameter predicted by anode erosion and FEM models are compared with diameter obtained from SEM micrograph. The results obtained from the proposed models are well in agreement with the experimental results. The anode erosion model predicts the crater diameter and erosion energy with an average absolute error of 5.65 and 17.86 %, respectively. By estimating the energy required to erode a material and by setting appropriate process settings, the discharge energy can be effectively utilized for material removal.

Description: In this paper, a method is proposed to generate scanning paths to be used in automated abrasive waterjet polishing of free-form surfaces. This method is able to produce trajectories with constant offset distance between curves on surfaces with holes and complex boundaries without reconfiguration of their triangular mesh model. For this, the particular requirements of this polishing technique to be kept along the path are investigated. Next, a reference curve is obtained and using geodesic distances in specific directions, the adjacent offset curves are found. Finally, if needed, the main trajectory is divided into a set of continuous sub-trajectories. By defining two indices, the effect of the shape of the surface and the configuration of the generated path on the uniformity of the distribution of the waterjet is evaluated. Through several examples, it is shown that the method can effectively generate scanning paths adapted to the requirements of this technique.

Description: This paper shows the study of the heating phase of the quenching procedure of dies in steel ALVAR 14 (DIN 56 NiCrMoV7) for the extrusion of aluminum. The heat treatment was executed in BMI vacuum hardening furnaces (model B84T) at the company F. Ramada, Aços e Indústrias, S.A. The die had the shape of a massive disk and its heating was studied experimentally, by measuring and recording the relevant temperatures along the time using thermocouples, and was also studied analytically and numerically using the ABAQUS software. The experimental average convective heat transfer coefficient between the gas and the disk was found to be 10 W/(m 2  K), with the convective heating representing 22 % of the total energy supplied to the disk. The coefficients of heat transfer by radiation found at the initial and final stages of the heating process ranged between 3 and 64 W/(m 2  K), respectively, and were determined using the lumped system analysis in conjunction with experimental data. By acting essentially upon the apparent emissivity of the disks, it was possible to fit the numerically simulated heating curve of the disk to the experiments. The maximum value of the global heat transfer coefficient to the disk was fairly low, 64 W/(m 2  K), resulting on Biot numbers below 0.1, and thus allowing the use of lumped system analysis. These Biot numbers also indicate that the temperature gradients inside the dies are smaller than expected, enabling the use of higher heating rates that reduces the total time and costs of the quenching treatment.

Description: This paper reports a study and analysis of non-even wire tension in high-speed wire electrical discharge machining (HSWEDM). This problem has been a challenge since HSWEDM was invented. The tensions of the wire electrode at both ends of a wire-winding cylinder become inconsistent when the wire electrode continues discharging for a certain period. Studies have suggested that the amount of dielectric fluid added into the discharging gap differs depending on the positive and negative moving directions of the electrode. The resistances experienced by the electrode differ because of the discharging explosion. Meanwhile, the elongations of the electrode differ according to positive and negative moving directions. Therefore, tensions are inconsistent, and non-even wire tension occurs. Factors that affect non-even wire tension are studied, and a new mode of variable wire speed reciprocating WEDM is designed. Experiments show that the machining effects in the new mode are better than those in the traditional mode under the same cutting conditions. Processing accuracy, surface quality, and cutting speed are increased. Moreover, the service life of the electrode is extended three times or more with the new mode compared with that in the traditional mode.

Description: The chemical action, which is generally determined by acid or alkaline regulator in the slurry, plays an important role in fixed abrasive chemical mechanical polishing (CMP). Experiments were conducted to explore the influence of acid slurries on surface quality and material removal in fixed abrasive CMP of LBO (LiB 3 O 5 ) crystal with soft and brittle, difficult-machining properties. Four organic acid regulators with pH 4.0 (acetic acid, lactic acid, citric acid, and oxalic acid) were screened by the polishing experiments. Further, pH value of the regulator was optimized to the most suitable chemical environment fit for polishing of LBO crystal using three indexes, i.e., material removal rate (MRR), surface topography, and surface roughness. The results indicated that citric acid leads to more robust polishing performance with surface roughness Sa (surface roughness average) 0.52 nm lower than the others. Additionally, MRR decreases with increasing pH value. Surface roughness initially decreases with increasing pH value, then it mutates to the maximum 9.37 nm after reach the minimum. The abrasive-free acid slurry with citric acid at pH 5.0 is effective for fixed abrasive CMP of LBO crystal, obtaining a MRR of 366 nm/min and fine surface quality with surface roughness Sa 0.32 nm with rather slight surface damage.

Description: Uncertainty in the cost and process parameters is very common in practice. In this paper, we develop a scenario-based robust economic and economic-statistical design of exponentially weighted moving average control chart to account for economic and statistical criteria as well as the uncertainty. For this purpose, we use Lorenzen and Vance cost function for economic and economic-statistical design of an exponentially weighted moving average control chart in the real applications. Absolute robustness criterion which minimizes the worst-case scenario and also robust deviation which minimizes the deviation from the optimal solutions are applied to explore the robust approach for robust design of the exponentially weighted moving average control chart. The optimization models are solved by using the genetic algorithm. The performance of the proposed methods is illustrated through two numerical examples. Finally, the application of the proposed methods is illustrated in a real manufacturing case in the tile production industry.

Description: In the plastic injection molding (PIM), the optimization of the process parameters is a complex task. The objective of this study is to propose an intelligent approach for efficiently optimizing PIM parameters when multiple objectives are involved, where different objectives, such as minimizing part weight, flash, or volumetric shrinkage, present trade-off behaviors. Multiple objective functions reflecting the product quality are constructed for the optimization model of PIM parameters. The proposed approach integrates Taguchi’s parameter design method, back-propagation neural network (BPNN), grey correlation analysis (GCA), particle swarm optimization (PSO) and multiobjective particle swarm optimization (MOPSO) to locate the Pareto optimal solution for multiobjective optimization problem. PSO and GCA are applied to optimize the network structure of BPNN to establish multiobjective mathematical model (PSO-GCANN) that finely maps the relationship between the input process parameters and output multiresponse. MOPSO is used to fine-tune the Pareto optimal solutions while the approximate PSO-GCANN is utilized to efficiently compute the fitness of every individual during the evolution of MOPSO. The illustrative application and comparison of results show that the proposed methodology outperforms the existing methods and can help mold designers to efficiently and effectively identify optimal process parameters.

Description: The use of carbon fiber reinforced polymer (CFRP) composites becomes more attractive today in various industrial sectors such as aerospace, naval, and automotive. This is due to their high mechanical properties (strength, stiffness, light weight, etc.) and corrosion resistance. Machining processes such as trimming or drilling are frequently used to achieve dimensional tolerance and assembly requirements. However, a damage process involving matrix cracking, fiber fracture, and interlaminar delamination often occurs when machining these materials. In the current work, a numerical analysis has been used to identify the most significant machining factors and their interaction on the induced damage and cutting force. The orthogonal Design of Experiments (DoE) L 27 (3 13 ) of Taguchi has been applied to investigate the effect of the fiber orientation, the tool rake angle, the depth of cut, and the tool edge radius. The induced damage can strongly affect the surface roughness (surface quality of the workpieces) and considerably limits the use of these materials in many industrial applications. First of all, a coupled elastoplastic damage behavior law was adopted to simulate the permanent deformations caused by plasticity and to predict the degradation of mechanical properties due to the initiation of damage and its progression inside the composite structure. Satisfactory numerical results have been found and a good correlation has been obtained compared to experimental trends. The results reveal that the interaction between some factors could be neglected and the obtained responses are greatly influenced by the fiber orientation and the depth of cut rather than the tool rake angle and the tool edge radius.

Description: Titanium alloy is a difficult-to-cut material, widely used due to its excellent material and mechanical properties. In this paper, the cutting mechanisms of titanium alloy Ti6Al4V under up-milling and down-milling with different cutting conditions have been theoretically and experimentally discussed. The milling processes were simulated by an orthogonal cutting finite element model. And a series of milling experiments were carried out to verify the simulated results. Significantly, it elaborates the prominent differences of cutting mechanisms of titanium alloy between up-milling and down-milling.

Description: Experimental investigation and finite element simulation of face milling AISI H13 steel with CBN tool were conducted in order to acquire thorough understanding of the chip temperature and its effects on chip morphology, cutting forces, and surface roughness. Cutting speeds adopted in the tests and simulations were in the range of 800 to 1,600 m/min. Axial depth of cut and material removal rate were set to be invariable for each cutting speed. The cutting parameter zones where relatively high chip temperature (zone “ H ”), long helix chip (zone “ L ”), lower resultant cutting force (zone “ R ”), and lower surface roughness (zone “ S ”) arose were distinguished. The analysis results showed that the higher chip temperature in zone “ H ” led to higher ductility of the chip, resulting in the formation of long helix chip instead of short washer-shaped chip. The thermal softening effects induced by higher chip temperature in zone “ H ” led to lower cutting force and more stable cutting process which was beneficial for the better surface finish. Relatively high chip temperature, relatively low resultant cutting force, and relatively low surface roughness arose at the same time in cutting parameter zone “ R ”.

Description: This paper presents a self-evaluation method for sub-micrometer accuracy measurement of the cutting edge contour of a micro diamond tool with a force sensor-integrated fast tool servo (FS-FTS) on an ultra-precision lathe without using any accurate reference artifacts and additional surface form measuring instruments. At first, a series of grooves is cut side by side along the Z -direction over the outer surface of a cylindrical artifact mounted on the lathe spindle by the micro tool of the FS-FTS, which is mounted on the X -directional cross-slide ( X -slide) of the lathe, to form a number of sharp line structures. The FS-FTS is then switched to a force feedback control mode for the cutting edge of the micro tool to scan across the line structures as a measuring stylus by moving the artifact with the Z -directional carriage slide ( Z -slide) of the spindle. During the scanning, the contact force between the micro tool and the line structures is maintained constant by controlling the X -directional displacement of the cutting tool with the FS-FTS so that the tool cutting edge contour can be obtained from the tool scan trace profile provided by the linear encoder of the Z -slide and the displacement sensor of the FS-FTS. Measurement experiments of a micro tool with a nominal nose radius of 120 μm are carried out to demonstrate the feasibility of the proposed method.

Description: Ultraprecision optical elements have found an increasing utilization in various fields for their superior performance so do the manufacturing technologies for optics. With the aim to optimize the conformal polishing (CP) process using continuous precession (Con-P), a theoretical and experimental investigation is presented. Firstly, this study introduced the merits of Con-P and the encountered problem when it is used in CP. By analyzing the removal function and dynamic polishing process, it was shown that the bad performance on CP of Con-P is coursed by the incompatibility of rotation speed of A -axis (RSA) and feeding speed (FS) of bonnet tool. Then, in order to obtain the optimal ranges of RSA and FS to improve the performance on CP, comparative simulations of Con-P were implemented and analyzed. It is shown that the ability for CP is changing with a newly proposed conformal factor f , f  =  n 1 (RSA)/ vfx (FS), in addition, only when f reaches a certain threshold ( f  〉 20), Con-P has good performance on CP. On the other hand, it was also indicated that the material removal is only affected by the FS of bonnet tool. Finally, polishing experiments were conducted to validate the simulated optimization. It is revealed that the experimental results are basically consistent with the simulations, which proves the reliability of the optimization process by using conformal factor f .

Description: The structural performance of arc spraying rapid tooling (ASRT) directly affects its application in prototype automobile manufacturing. The ASRT is made up of several kinds of materials, which increases the difficulty of structural analysis. In this paper, the properties of arc-sprayed coating and its influence on ASRT were analyzed by tensile test, and the stiffness model of ASRT was established to optimize the structure design. Furthermore, a failure evaluation criterion was adopted to analyze the feasibility and reliability of ASRT. Therefore, a new hybrid structure of ASRT was proposed to reduce the difficulty of its fabrication process. The research results demonstrate that the performance of ASRT can be improved by proper structure design, and it is also proved that ASRT is easy to be fabricated at low cost and can meet the requirements for prototype automobile.

Description: Quartz, being hard and brittle, is difficult to machine. Although good machining effects of quartz have been achieved by wire electrochemical discharge machining (WECDM), the surface quality of microslits obtained needs to be enhanced and higher machining precision is desired. To attain improvement in quartz machining, this study performs WECDM under titrated electrolyte flow with the addition of silicon carbide (SiC) powder. On the one hand, titrated electrolyte can facilitate rapid replenishment of the electrolyte, which contributes to maintain the stability of the insulating gas film, thus ensuring frequent and steady electrical discharge for better machining precision. On the other hand, the SiC powder added can help polish the finished workpiece for surface quality enhancement. Experiments are conducted to determine the appropriate machining parameters and to explore the processing mechanisms involved. Comparison in terms of machining precision and surface quality is made for WECDM conducted with and without additives. Experimental results show that better surface roughness and precision of microslits can be obtained with brass wire electrodes of 150 μm diameter and SiC powder of 11 μm at 5 wt%. The addition of abrasive SiC powder helped decrease surface roughness from 1.13 to 0.22 μm, an improvement in surface quality by 80 %. Moreover, the mean slit width was also reduced from 200 to 185 μm. Hence, WECDM of quartz glass under titrated electrolyte with SiC powder added to the electrolyte can indeed enhance surface quality and precision of the microslit. Moreover, not only does such approach use less electrolyte, but also it incurs lower cost and less pollution, making it cost effective and environmental friendly.

Description: The purpose of the fixture layout design is to ensure the fixture positioning accuracy, which affects the resultant geometric variation of the positioned workpiece directly. The N –2–1 locating principle is widely applied in the fixture design for deformable sheet metal workpiece, not only for locating the workpiece, but also for restraining the excessive workpiece deformation. This paper proposes an approach to optimizing fixture layout for the sheet metal workpiece based on the 4–2–1 locating scheme. Firstly, three fixture locating points on the primary datum surface are optimized with genetic algorithm based on the rigid model considering the robustness and the geometry stability. Then based on finite element analysis, a back propagation neural network model is built to predict the deformation of the sheet metal workpiece under different fixture layouts and different fixture locator errors, and a genetic algorithm is used to find the optimal position of the fourth fixture locator based on the neural network prediction model. Finally, a case study is given to verify the proposed approach.

Description: Micro-grooving, as a form of surface texturing, has a wide array of industrial applications. However, conventional methods of micro-grooving are plagued by numerous problems including large burrs, big cutting forces, and poor machining quality. In this paper, ultrasonic elliptical vibration cutting is used to assist micro-groove turning on cylindrical surfaces. The elliptical locus during the cutting process is generated by a newly designed 2D resonant ultrasonic vibrator. The objective of this paper is to predict turning behavior such as the cutting forces in the ultrasonic elliptical vibration-assisted micro-groove turning process. A simplified cutting force analysis model which considers the geometry of the micro-groove features is established by analyzing the cross-sectional area of the cut and the elliptical vibration locus in the ultrasonic elliptical vibration-assisted micro-groove turning process. The removed chip volumes per vibration cycle are calculated by integrating the cross-sectional area of the cut in the elliptical vibration locus direction. In this process, the volume of the material ahead of the tool is proposed as an indicator to analyze and model the cutting forces. The cutting forces are determined by combining the chip geometry with the tool, and the removed chip volumes per vibration cycle are used to predict the behavior of cutting force in different machining conditions. The influence of vibration conditions and machining conditions on the removed chip volumes per vibration cycle are analyzed, and a series of micro-groove cutting experiments under different machining conditions are performed to verify the effect by comparing with the variation trend of measured cutting forces in the ultrasonic elliptical vibration-assisted micro-groove turning process. Results show the effectiveness of the indicator of the removed chip volumes per vibration cycle for cutting force in elliptical vibration-assisted micro-groove turning process.

Description: This paper presents a different web-based virtual turn-milling system, which aims to address the common problems of existed systems. The system has not only economical value, such as shortening product cycle from design to market, but also scientific interest, like proposing a new trajectory planning method. In other words, it helps sellers and buyers better understand products and enables planners and machinists to make decision or verify CNC codes much more accurate and faster. This system is made up of three levels, which is client browser, server, and database, and every level is divided into several specified functions. Among all the functions, turn-milling simulation function is the most crucial part. To enhance the system’s features, many sub-function modules are also adopted in simulation functions. Through these modules, the system implements material removal function, tool trajectory planning function, numerical control (NC) code inputting and compiling function, and so on. To realize these functions, the whole machining system is developed by using the network superiority of Java language and Virtual Reality Modeling Language (VRML) technology interaction, which will also lead to smaller data volume. Owing to the transportability of Java language and VRML technology as well as the good understandability of the system, this web-based virtual turn-milling system is also suitable to the dynamic demonstration and machining simulation of other NC machine tools. Some future research directions are given to perfect the system in the end.

Description: Aluminium alloys are increasingly used by the automotive, aerospace and military sector. The most often used workpiece materials are the so-called Al–Si and Al–Mg–Si alloys, of which, the most widespread are aluminium alloys reinforced with silicon because of their numerous advantageous mechanical and chemical properties. In case of different types of workpiece materials made ready by cutting, surface roughness ( R a , R z ) as a criterion is as important as geometric sizes and tolerance or the mechanical features of the material, e.g. tensile strength and hardness. The expected functional and friction features are not defined properly by average roughness ( R a ) or surface height ( R z ). The expected functional behaviour can be described much better by skewness ( R s k ) and kurtosis ( R k u ) as statistical parameters of surface roughness. In this article, two types of aluminium alloys were cut with diamond tools using different edge geometries and edge materials. The statistical parameters of the surface roughness produced were analysed in order to find connections between these parameters and the circumstances of the cutting process, including edge geometry, tool material, workpiece material, and cutting parameters. The results show that surfaces with good tribological properties can be reached by a well-designed turning process.

Description: Compound closed-loop mechanism methodology is proposed to model the wheel loader front-end kinematics for simulating the mechanism motion in a dynamic environment. For the numerical modeling purpose, the mechanism is considered as consisting of three vector loops connected by the joint angles or displacements. Each vector loop is formulated as time-dependent ordinary differential equations (ODEs). The simulations cover the numerical solutions of the forward and reverse kinematics differential equations. The consistency error check approach is employed to validate the simulation. A case study is presented to demonstrate the reverse kinematics simulation of the compound mechanism model in Simulink environment, which includes the user-defined program, numerical solution, and error analysis. The displacement-time variations of two driving cylinders are obtained with the inputs of the lift and rotation bucket accelerations. The simulation is validated with the numerical analysis of the error results. This research provides a significant method to simulate the wheel loader motion for wide-ranging engineering application.

Description: Systematic numerical investigation is performed to study the effects of different case studies on butt welding of dissimilar thicknesses plates which is a normal type of welding geometry in shipyards. To start with, the numerical study of thermo-mechanical analysis is verified by experimental test results reported in this paper. In the experiment, two stainless steel plates with 2.5 and 4 mm thicknesses are welded with single-pass butt welding with GMAW. The numerical investigation is conducted with eight different case studies, belonging to three different groups to evaluate the effects of each case on the structural response. These eight cases are grouped according to the heat input position, welding parameters, and different ratios between thicknesses. It is concluded from the results that the changing ratio between thicknesses has a significant effect on the structural response.

Description: Incremental forming process is a method for rapid prototyping and low-volume production. Recent ideas have been introduced as “incremental sheet metal punching.” In this study, a new analytical modeling of the process with respect to the forming mechanism and slip line field has been presented. The analysis sheet formation in this process can be divided into two stages: penetration and curve making. At the penetration stage, both approaches of the upper bound method and slip line field were used to calculate the pressure and velocity of the punch. At the second stage, the estimated slip line field was assumed for curve making. This leads to making a suitable prediction with good accordance. Furthermore, the effects of some parameters such as punch diameter and depth on the punch pressure have been evaluated.

Description: The study in this paper focuses on surface morphology and crack formation of 7050-T7451 aluminum alloy in high-speed milling, from 3000 to 5000 m/min. The surface roughness of machined workpiece was investigated with optical profiler; minimum R a and R q value were obtained at the cutting speed of 5000 m/min. Defects such as smeared material, metal debris, and feed marks on workpiece surface were observed with scanning electron microscope. One kind of edge-oxidized feed mark was found on surface. Width of it was measured and two hypotheses were introduced to interpret this phenomenon. Based on the hypothesis, the workpiece surface was determined to be formed at cut-off process. Two kinds of microcracks were observed on Al 7 Cu 2 Fe and Mg 2 Si phase. Those cracks showed different orientations, and this was helpful for interpreting the formation of microcracks in high-speed machining. The heat imposed to surface was connected with cracks on different phases. The results provided a complete view of surface morphology generation and microcrack-formation mechanism in high-speed cutting process. The two aspects of this research were helpful for controlling the integrity of surface and prolong service life of workpiece.

Description: Micro-milling is widely accepted as the most promising approach to repair the micro-defects on the KH 2 PO 4 (KDP) surface. In order to get excellent surface quality of workpiece, the ductile cutting of KDP crystal should be achieved. Compared to plastic materials (e.g., metals), the ductile cutting of KDP crystal is more sensitive to the geometrical parameters of tools and cutting parameters, as a result of the soft brittle properties of KDP crystal. In this work, the variable regularity of peak to valley (P-V) value of cutting force on cutting parameters was obtained through simulations, which was matched well with the results obtained from the single-factor experiments using the self-designed micro polycrystalline diamond (PCD) ball end mill. Meanwhile, the ductile cutting parameters of KDP crystal were also obtained through the single-factor experiments. Then, the orthogonal experiments were explored which reveal that the axial depth of cut and the feed speed had maximal and minimal influences on the roughness value R a , respectively. Moreover, the optimal cutting parameters which are the spindle speed (7 × 10 4  r/min), axial depth of cut (0.5 μm), and feed speed (30 mm/min) were also gained. At last, the optimal cutting parameters obtained above which were used in the repairing experiments were proved to be good cutting parameters because the good surface quality of repairing outlines was achieved; meanwhile, the repairing performance of self-developed micro PCD ball end mill was also verified.

Description: This paper presents a method to reduce the fluctuation of machining strip width by modifying tool position. When the machining strip width varies rapidly within a tool path, the fluctuation of cutting force brings negative influence on the workpiece and cutter. Furthermore, as the tool path interval is always defined conservatively to avoid undercut, the machined strips of adjacent tool paths have unnecessary amount of overlap. Rapid changing machining strip width usually creates too much overlap at some location, which causes repeated cutting. A method is proposed to modify tool position and reduce the fluctuation of machining strip width. Besides, tilt angle smoothness along the tool path is also taken into account. The computation result of a blade surface verified the validity of the proposed method.

Description: In order to improve the accuracy of productivity calculation and prediction, this paper aims to establish a mathematical model, which takes multi-factor revision into account, to evaluate the personnel operational capacity (POC) of aircraft assembly lines. Firstly, the assembly operation is divided into assembly operating elements (AOEs), which is based on the features of aircraft assembling and is for the provision of statistical units. Secondly, effective man-hour (EMH) is adopted as a yardstick to measure the POC. Then, considering the technical characteristics and environmental constraints of the real assembly line, detailed quantitative descriptions about the chosen key factors, namely assembling accuracy, learning effect, and assembling intensity, are provided, and these quantitative descriptions are used for the revision of the EMH in order to guarantee a higher precision. After that, several critical parameters such as the cycle time, tact time, and output of an assembly line can be solved out, from which the POC can be analyzed and reflected. Finally, this method has been successfully applied to a practical case, and the result justifies its advantage as well as feasibility.

Description: In this work, two brazed diamond wheels fabricated by brazing in vacuum were used to grind alumina at different grinding speeds. During the process, the horizontal and vertical grinding forces were measured by a force measurement device. The grinding forces, specific grinding energy, and friction in grinding of alumina at low and at high speeds were investigated. The results show that the friction coefficient decreases with the increase of the grinding speed and also relates to the grinding mode. A nearly proportional relationship between grinding power per unit width ( P m ) and the rate of plowed surface area generated per unit time per unit width ( S w ) reveals the effects of friction in grinding and most of the grinding energy is expended by friction. The surface energy per unit area generated by plowing friction ( J s ) for high-speed grinding is found to be lower than for low-speed grinding.

Description: This paper presents an investigation of nonplanar tool-workpiece interactions in free-form milling using a ball-end cutting tool, a technique that is widely applied in the manufacturing of dies and molds. The influence of the cutting speed on the cutting forces, surface quality of the workpiece, and chip formation was evaluated by considering the specific alterations of the contact between tool-surface along the cutting time. A trigonometric equation was developed for identifying the tool-workpiece contact along the toolpath and the point where the tool tip leaves the contact with the workpiece. The experimental validation was carried out in a machining center using a carbide ball-end cutting tool and a workpiece of AISI P20 steel. The experimental results demonstrated the negative effect of the engagement of the tool tip into the cut on machining performance. The length of this engagement depends on the tool and workpiece curvature radii and stock material. When the tool tip center is in the cut region, the material is removed by shearing together with plastic deformation. Such conditions increase the cutting force and surface roughness and lead to an unstable machining process, what was also confirmed by the chips collected.

Description: In the literature, multiple dependent state variable sampling plans are available that does not constitute the process loss and hence are unable to distinguish among the product that falls within or outside specification limits. In this manuscript, the multiple dependent state variable sampling plans with process loss consideration are proposed. The designed parameters of the proposed plan are found by satisfying the vendor and buyer risks at various acceptable quality level and limiting quality level. The advantages of the proposed plan are discussed compared with the existing plans using the process loss function (Yen and Chang Commun Stat: Simul Comput 38:1579–1591, 2009 ) and Aslam et al. (Commun Stat-Theor Method 41:3633–3647, 2012 ). A real industrial example is included to illustrate the proposed plan.

Description: Robot selection is a challenging process for most industrial production purposes. The variability of characteristics and the capabilities of robotic mechanisms, which determine their specialization in specific tasks, render the selection procedure even more complicated. Various methodologies and, by extension, different perspectives have been introduced in order to address the selection problem using several decision-making tools. In the current article, an integrated comparative analysis of a representative sample of methodologies, which have been implemented for two real-world problems, is presented. Additionally, a generator of random example cases in conjunction with correlation (Spearman’s rank correlation coefficients) and visual (dendrograms and bar graphs) tools has been used in order to detect similarities and differences between the selection methods as well as to evaluate qualitatively their overall behavior.

Description: Laser cutting of thick-section circular mild-steel blanks of 10 mm thickness is examined. Thermal and stress fields developed in the cutting zone are predicted using finite element method and the simulation conditions are selected in line with the experimental parameters. An experiment is carried out to assess the geometric features of the cut surfaces. The morphology of the cut sections are examined using optical and scanning electron microscopes and energy dispersive spectroscopy is carried out for elemental composition of the cut surface. It is found that laser cutting of thick steel blanks results in substantial conduction loss from the cutting zone, which results in high-temperature gradients and large stress levels in the cutting section. The cut edge features such as local dross attachment, striation patterns, and microcrack formation in the cut section are also examined.

Description: The coronary stent fabrication requires a high-precision profile cut. Fibre lasers present a solution to accomplish these requirements. This paper presents an experimental study of fibre laser cutting of 316L stainless steel thin sheets. The effect of peak pulse power, pulse frequency and cutting speed on the cutting quality for fixed gas type and gas pressure was investigated. A mathematical model based on energy balances for the dross dimensions was formulated. The dross height and the dross diameter were analysed and compared with the experimental results. This allows adjustment of the process parameters to reduce the dimensions of the dross deposited at the bottom of the workpiece during laser cutting of thin sheets.

Description: Electro-discharge machining process has found widespread applications in the industry over the last few decades. With growing trends towards miniaturization of machined parts, developments in the area of microelectromechanical systems, and the requirements for microfeatures in difficult to cut materials, micro-EDM has become an important and cost-effective manufacturing process because of its noncontact machining capability using microsized tools. This paper involves understanding of the effects of basic machining parameters on dimensional accuracy of the microholes by measuring top and bottom radial overcuts and taper angle and electrode depletion during micro-electro-discharge machining of aluminium (Al 1100) with tungsten electrode of diameter 300 μm. The microelectrodes have been cut using a foil electrode and shaped using a WEDG system. The experimentation has been designed using Taguchi methodology with gap voltage, capacitance, and pulse ON time as electrical parameters and thickness and electrode rotation as non-electrical parameters. Results obtained have been critically discussed.

Description: Rapidly prototyping a polymer microfluidic device is a growing interest in the application fields of the disease detection, drug synthesis, and the environmental monitoring because of the benefits of the miniaturized platforms. Micromilling is one of the micromachining methods and it has been commonly used to manufacture polymer microfluidic devices. The advantages of using micromilling for polymer microfluidic devices include faster fabrication process, lower cost, easier user interface, and being capable of fabricating complicated structures, which make micromilling a perfect candidate in rapid prototyping polymer microfluidic devices for research idea testing and validation. This aim of this study is to understand the influence of each micromilling parameter to the surface quality, followed by the factor analysis to determine the optimal cutting conditions. The parameters included spindle speed, feed rate, depth of cut, and the selection of coolant (compressed air/oil coolant), and the milled surface quality was measured by a stylus profilemeter. Polymethyl methacrylate (PMMA) is the mainstream substrate material in the microfluidics due to its excellent optical property and popularity and is used as the target substrate. The experiment results showed that using the compressed air as a coolant can deliver a better surface quality than the oil coolant, and the smallest roughness achieved was 0.13 μm with the spindle speed of 20,000 rpm, feed rate of 300 mm/min, and the depth of cut of 10 μm. Factor analysis revealed that the depth of cut has the largest impact while the spindle speed has the minimized impact to the surface quality of a micromilled PMMA substrate. To further confirm the optimal cutting conditions, another 12 reservoirs were micromilled with the optimal cutting conditions and the average roughness is 0.17 μm with a stand deviation of 0.08 μm.

Description: This paper presents a study of friction stir welding of aluminium and copper using experimental work and theoretical modelling. The 5083-H116 aluminium alloy and pure copper were successfully friction-stir-welded by offsetting the pin to the aluminium side and controlling the FSW parameters. A theoretical analysis is presented along with key findings. The process temperatures are predicted analytically using the inverse heat transfer method and correlated with experimental measurements. The temperature distribution in the immediate surroundings of the weld zone is investigated together with the microstructures and mechanical properties of the joint. This was supported by a finite element analysis using COMSOL Multiphysics. In this study, two rotational speeds were used and a range of offsets was applied to the pin. The microstructure analysis of the joints was undertaken. This revealed some particles of Cu inclusion in the nugget zone. The energy dispersive spectroscopy showed a higher diffusion rate of aluminium towards the interface while copper maintained a straight base line.

Description: This paper proposes a product of exponential (POE) model to integrate the geometric errors of multi-axis machine tools. Firstly, three twists are established to represent the six basic error components of each axis in an original way according to the geometric definition of the errors and twists. The three twists represent the basic errors in x, y, and z directions, respectively. One error POE model is established to integrate the three twists. This error POE formula is homogeneous and can express the geometric meaning of the basic errors, which is precise enough to improve the accuracy of the geometric error model. Secondly, squareness errors are taken into account using POE method to make the POE model of geometric errors more systematic. Two methods are proposed to obtain the POE models of squareness errors according to their geometric properties: The first method bases on the geometric definition of errors to obtain the twists directly; the other method uses the adjoint matrix through coordinate system transformation. Moreover, the topological structure of the machine tools is introduced into the POE method to make the POE model more reasonable and accurate. It can organize the obtained 14 twists and eight POE models of the three-axis machine tools. According to the order of these POE models multiplications, the integrated POE model of geometric errors is established. Finally, the experiments have been conducted on an MV-5A three-axis vertical machining center to verify the model. The results show that the integrated POE model is effective and precise enough. The error field of machine tool is obtained according to the error model, which is significant for the error prediction and compensation.

Description: This paper investigates the errors generated during the fabrication stage for producing complex anatomical replicas derived from computed tomography coupled with the 3D additive manufacturing methods. Based on this research work, it is shown that patient-specific model based on computed tomography data can be converted into computer numerically controlled G-code. It is shown that 3D extrusion-based additive manufacturing technology is accurate to ±3 % equating to ±200 μm surface deviations due to plastic shrinkage and distortion formed during the process. Polylactic acid plastic extrusion through a 200-μm bore nozzle has resulted in a model being produced with an R a roughness of 35.5 μm. An evaluation on the errors generated during the fabrication process has been used to accurately produce an adult female mandible. Internal nerve channels and complex external bone geometry has been produced within the model. It is shown that using this process results in bone complexity and accuracy required for producing low-cost surgical grades models which is in comparison with traditional selective laser sintering manufacturing techniques. The surface accuracies suggest that the reproduction of anatomically complex representative structures by 3D plastic extrusion additive manufacturing which can be used for pre-surgical planning.

Description: The development of sustainability assessment for machining process is considered as one of the crucial strategies to realize sustainable design and manufacturing, while existing methods focusing on environmental assessment have limits due to neglect economic and social impacts. This paper proposes an assessment approach for evaluating sustainability performance of machining process with respect to a consistent set of environmental, economic, and social criteria in order to select a machining strategy from sustainable manufacturing viewpoint. Sustainability assessment criteria are identified to compare different machining parameter alternatives; cutting noise, especially, is defined as an important criterion of social impact, and energy, lubricant oil, and cutting fluids consumption are identified as criteria of environmental impact. Additionally, the weights of criteria are determined using entropy weight approach with the advantage of objective evaluation by exploiting the useful information of data to a maximum extent. Furthermore, sustainability performance of machining process is calculated based on extension theory through utilizing correlation function between evaluated matter-element and classical field matter-element. Face milling test conducted on CNC vertical machining center not only illustrates validity of the proposed method for assisting the engineers or designers to define sustainability performance of machining process, but also proves the relationship between cutting parameters and cutting noise.

Description: This research demonstrates the use of submerged friction stir welding under liquid nitrogen as an alternative and improved method for creating fine-grained welds, and hence, to alleviate formation of intermetallic phases. Magnesium alloy and aluminum alloy were joined by friction stir welding in two environments, namely air and liquid nitrogen, with 400 rpm rotation and 50 mm/min travel speed. The temperature profile, microstructure, scanning electron microscope energy dispersive X-ray spectroscopy analysis and hardness were evaluated. In the stir zone of air-welded specimen, formation of brittle intermetallic compounds causes the weld to crack. These phases were formed because of constitutional liquation. The stir zone of under liquid nitrogen-welded specimen showed that formation of intermetallic compounds is suppressed significantly because of lower heat input.

Description: Hobbing process is one of the machining methods in manufacturing spur gears. In machining processes, selecting a suitable lubricant is one of the significant factors in enhancing machining productivity and improving the characteristics of manufactured workpieces. This study has used the nanolubricant including alumina nanoparticles dispersed in mineral-based oil 25W-50 in hobbing process. Then, hobbing process using the lubricant including both nanoparticles, and none has been done utilizing with the similar hob tools. Two spur gears with DIN1.7131 material have been manufactured using each of two lubricants. Then, the hob tool wear and surface roughness values of manufactured spur gears were investigated. Comparing the results show that using lubricant including alumina nanoparticles in hobbing process causes an expressive decrease in the hob tool crater and flank wear. Also, arithmetic surface roughness value in spur gears manufactured with nanolubricant has decreased.

Description: Focusing on a low price segment is usually not an option for production companies in high-wage countries. In order to stay competitive, companies have to match individual products with prices close to those of mass products. A proven instrument in reducing costs in manufacturing processes is modularization. In the die casting industry, many manufacturers already have company specific methods of modularization in their construction departments. The dies are strongly influenced by the style of the design engineers. A holistic design methodology is not yet established. To improve this current situation, a methodology for the layout of modular dies has been developed. The methodology consists of three main phases where the focus is narrowed down from company via die to component perspective. This methodology will assist the design engineers throughout the development of new dies, helping to choose an appropriate set of modules based on technical as well as economic criteria.

Description: For the purpose of generating 2D curve offsets used in 2.5D machining, four new methods based on morphological operations on different mathematical entities are presented in this paper. All of the methods, which lend themselves for parallel processing, exploit the idea that the boundaries formed by a circular structuring element whose center sweeps across the points on a generator/base curve comprise the entire offsets of the progenitor. The first approach, which is a carry-over from image processing, makes good use of morphological operations on binary images to produce 2D offsets via contour tracing algorithms. The second method, which is to rectify the high memory cost associated with the former technique, utilizes morphological operations on (boundary data) sets. The implementation of this basic technique is illustrated by two Matlab functions given in the paper. Despite its simplicity, the time complexity of this paradigm is found to be high. Consequently, the third method, which is evolved from the preceding one, reduces the time complexity significantly with the utilization of a geometric range search method. This technique, which has a considerable margin for improvement, is found to be suitable to be used as a part of the real-time motion command generator for CNC applications. Unlike the previous schemes, the final approach uses polygon operations to generate such curves. The run-time of this technique is highly governed by the complexity of the polygon overlay algorithm selected. The paper analyzes the complexity of each technique. Finally, the presented methods are evaluated (in terms of run-time and geometric accuracy) via two test cases where most CAD/CAM packages fail to yield acceptable results.

Description: Thermal error is one of primary reasons affecting the cutting accuracy of a machine tool. Especially, high-speed spindle’s thermal error restricts the improvement of high-precision machine tool accuracy. In this paper, the traditional back propagation (BP) neural network modeling principle is firstly analyzed. Then, considering the BP network, which is simple and adaptive but converges slowly and is easy to reach local minima, a genetic algorithm (GA) is introduced to optimize BP network’s initial weights and thresholds. Lastly, the network is trained using combined GA and BP technologies with practical thermal error sample data. In experiments of thermal error prediction of the high-speed spindle in a machine tool, the average compensation rate is increased from 89.03 % of BP model to 93.155 % of GABP model. Therefore, GABP model shows its effectiveness in quickly solving the global minimum searching problem.

Description: As the industrial environment becomes more competitive, supply chain management (SCM) has attained growing attention from practical and academic societies as a crucial discipline. Among the involved decisions in the field of SCM, integrated inventory management is addressed in this paper. In this regards, this paper proposes an integrated inventory management model within a multi-item, multi-echelon supply chain (SC). The considered SC comprises multiple agents in upper layers supplying those of lower layer to enhance flexibility of the SC. Furthermore, three inventory models are developed with respect to different layers of SC in an integrated manner, seeking to optimize total cost of the whole SC. Due to nonlinear structure of the proposed model; high level of computational complexity is resulted. To cope with the complexity of proposed model, a differential evolution algorithm is adopted. Conducted numerical results indicate validity of the developed algorithm.

Description: Laser drilling is a thermal process with relatively low energy efficiency since the material removal mechanism is mostly based either on melting or on vaporization. Aiming at the investigation of the laser drilling efficiency, a theoretical both analytical and numerical study of evaporation pulsed laser drilling is presented. The analysis is based on a linear approximation of the temperature profile and separates the process into three phases, those of the heating, the melting and the vaporization. Based on these models, the energy efficiency and its dependence on the process parameters have been investigated and selection of relevant process variable guidelines, towards improving energy efficiency, are given. Moreover, the physical mechanisms responsible for most of the energy losses are analysed and classified according to their importance.

Description: In this paper, a new procedure is developed to monitor a two-stage process with a second stage Poisson quality characteristic. In the proposed method, log and square root link functions are first combined to introduce a new link function that establishes a relationship between the Poisson variable of the second stage and the quality characteristic of the first stage. Then, the standardized residual statistic, which is independent of the quality characteristic in the previous stage and follows approximately standardized normal distribution, is computed based on the proposed link function. Then, Shewhart and exponentially weighted moving average (EWMA) cause-selecting charts are utilized to monitor standardized residuals. Finally, two examples and a case study with a Poisson response variable are investigated, and the performance of the charts is evaluated by using average run length ( ARL ) criterion in comparison with the best literature method.

Description: This paper focuses on a proper framework that uses the requirements and concepts of lean manufacturing for a specific application to projects of aerospace manufacturing processes aiming production automation. The main goal of this guideline is to provide information, for engineers who work on the development processes, about the automation benefits that can be achieved when using this proposed guidance method of analysis presented herein. A case study is presented to validate this method’s effectiveness.

Description: In order to obtain accurate tube hydroforming (THF) simulation results, one of the important inputs in the finite element model (FEM) of the process is the mechanical response of the material during THF. Generally, the mechanical response is defined by the stress–strain behavior that can be determined from tensile testing of the specimens extracted either from the sheet used for roll forming of the tubes or directly from the tubes. More recently, free expansion testing has been used to characterize the mechanical response of the material for hydroforming applications. The free expansion test can emulate process conditions similar to those found during THF, and as such, can be used to obtain reliable and accurate information on the mechanical response/properties of the tubular material. The aim of this research is to present an approach for evaluating the stress–strain behavior of different materials using a 3D deformation measurement system in conjunction with an analytical model. Here, to characterize the mechanical response of the materials, free expansion and tensile testing were used for austenitic stainless steel types 321 (SS 321) and 304L (SS 304L), INCONEL® alloy 718 (IN 718), and aluminum alloy 6061 in the annealed “0” temper condition (AA 6061-0). The mechanical response of each material, measured through free expansion testing of tubular forms, was compared to the respective stress–strain behavior determined from the uniaxial tensile test using ASTM E8 geometry specimens extracted from the tubes. For each material studied in this work, the two flow stress behaviors were distinct, indicating that the test method can have a noticeable effect on the mechanical response. Finite element analysis (FEA) of the free expansion of each material was also utilized to simulate the THF process with the flow stress curves obtained experimentally; the predicted expansion and burst pressure results were close to the experimental data indicating that the approach developed and described in this work has merit for characterizing the mechanical response of aerospace alloys for hydroforming applications.

Description: The carbide drill is an important hole-machining tool. Modern processing solutions set higher requirements for the accuracy and efficiency of carbide drill manufacturing. This paper presents a detailed study of mathematical models of the spiral groove, conical flank, and cutter clearance and proposes three practical and reliable grinding methods using only one standard straight wheel. The spiral groove is ground by controlling three crucial structure parameters: the spiral angle, core diameter, and rake angle. The conical flank is ground by controlling the relief angle, chisel edge angle, and apex angle. The cutter clearance is ground by controlling the ridge width and clearance depth. With these schemes, the wheel position parameters can be computed conveniently and quickly using computer programming, overcoming the low calculation accuracy of empirical formulae and thereby enhancing the efficiency. Using the wheel position parameters, the NC codes applicable to five-axis CNC grinders can be obtained. Furthermore, the reliability of the proposed grinding methods can be verified through CAD simulation and practical manufacture on a five-axis CNC grinder.

Description: The multi-point tool positioning algorithms produce much larger machining strip width than the single-point algorithms and apparently reduce the actual machining time. This paper presents a tool positioning algorithm for multi-point machining of sculptured surface, which is excellent at dealing with both of concave and convex surfaces. The proposed method is based on the middle-point error control (MPEC) method, which means the connection point between cutter and surface corresponds to the middle point of error distribution curve. Usually, only one cut contact (CC) point can be obtained with this method. Thus, the proposed method improved the MPEC method for achieving two CC points. At first, the shape of error distribution curve is investigated, and its asymmetry is evaluated. Secondly, the error distribution curve becomes symmetrical after the cutter is rotated with a roll angle, and the cutter is separated with surface at the same time. Finally, the minimum tilt angle is found, and two CC points are obtained without gouging. Machining experiment is conducted to verify the proposed method, and the result reveals that the machining strip width is increased apparently and the tool position is almost unchanged after the adjustment with proposed method. Simulation, measurement, and analysis are also given in the part of the experiment.

Description: Recent research is recognizing that multiple criteria analysis should take account of the concepts of uncertainty and risk. In some cases, precise determination of the exact value of alternatives and weights of criteria is difficult. Consequently, to deal with these potential problems, their values are regarded as fuzzy and intervals. This paper proposes an interval-valued fuzzy multiple criteria complex proportional assessment (IVF-COPRAS) method that can reflect both a subjective judgment and objective information in real-life situations. In this method, the performance rating values versus selected criteria as well as the weights of conflicting criteria are linguistic variables represented by interval-valued triangular fuzzy numbers. Moreover, performances of alternatives against subjective criteria are described via linguistic variables and then transformed into interval-valued triangular fuzzy numbers. Finally, an application example for the robot selection problem is given in this paper to show this decision-making steps and the effectiveness of the proposed method in manufacturing companies.

Description: In machining large complex parts with critical stock allowance, even small deviations in the blank parts or slight inadequacy in the fixturing may result in local shortage of material (i.e., insufficient stock allowance). This paper presents an optimal localization algorithm that aligns the measured points from a blank part with the nominal model to assure the weakest allowance area with as much material to be cut as possible. Instead of exploiting extra constraints to force the allowance at each point larger than a specific value, which is a popular strategy for allowance assurance in the previous localization algorithms, we formulate the blank localization problem as an unconstrained max-min problem. To deal with the unsmoothness exhibiting in the max-min objective function, a method based on the entropy optimization principle is adopted to convert the non-differential objective function to an unconstrained differential one, which can be efficiently solved using the conventional Quasi-Newton algorithms. The unconstrained optimization result finally gives rise to localization with the maximum allowance margin. For the blank parts that the material shortage is inevitable, the method can still efficiently achieve reasonable localization results, which confine the material shortage to a least extent. The proposed method is easy to be implemented and works well for both sparse sample points and dense-scanned points. Case studies included justify the superiority of the proposed scheme over the existing non-linear constrained optimization solutions.

Description: Unlike the normal vacuum chamber that a workpiece is put inside, a new vacuum chamber was designed to put on the welding zone of a workpiece, which has no size limit with this chamber, so that a large and thick plate could be welded with laser under low pressure. In this new vacuum chamber, a local subatmospheric pressure on the welding zone was achieved with side draught by a vacuum pump. A series of spot welding experiments were performed with fiber laser under subatmospheric pressure, normal atmospheric pressure with and without shielding gas side-blowing, respectively. The feature of weld surfaces and cross-section profiles for above different conditions were compared. A high-speed camera was applied to observe the behavior of plasma plume. The results indicated that the deeper welding penetration and narrower weld bead width could be obtained under subatmospheric pressure. The characteristics of spot weld bead under local subatmospheric pressure were quite different from the one under normal atmospheric pressure with shielding gas side-blowing method. The plasma plume was suppressed more effectively by local subatmospheric pressure than that by shielding gas side-blowing. Additional experiments of continuous laser welding under local subatmospheric pressure were tried and sound welds could be obtained.

Description: The low vibration of air spindle is a very important thing to achieve nanometer accuracies in the products of machined parts in nano-machining. Compared to the common air pockets with constant depth used in air cells of ultra-precision machines, this paper studied some special air pockets including five variable depth modes: flat, conical, pyramidical, spherical with two sphere radii. Considering rotational speed as well as these parameters, 18 experiments have been committed using a lathe machine. From experiment results, the air spindle with air pockets of pyramidical depth at a low rotational speed has minimum vibrations.

Description: Sustainable machining as a critical part in sustainable manufacturing has been valued by manufacturing enterprises of all sizes. The traditional short-term financial considerations are substituted by longer-term sustainable strategies to ensure the competitiveness, and ultimately, the survival of the company. Energy-efficient machining system, which promotes sustainable machining, is the focus of this paper. The energy-efficient machining system requires a comprehensive understanding as well as optimisation of energy consumption. Literature in this field is carefully reviewed and summarised. Energy consumption models, which are regarded as the core of the energy-efficient machining systems, are grouped into four categories, i.e. theoretical, empirical, discrete event-based, and hybrid models. Then, energy optimisation methodologies and strategies are discussed for energy-efficient process planning and production scheduling. The applications such as tool condition monitoring can employ energy information as useful input. Research inspired by energy-efficient machining studies is briefly introduced. The main elements of an individual energy-efficient machining system are then summarised. Discussions, research suggestions, and future directions are given at the end.

Description: Thermal error, especially the one caused by the thermal expansion of spindle in axial direction, seriously impacts the accuracy of the precision machine tool. Thermal error compensation based on the thermal error model with high accuracy and robustness is an effective and economic way to reduce the impact and enhance the accuracy. Generally, thermal error models are built only on temperatures at some points in the spindle system. However, the thermal error is also closely related to other working parameters. Through the theoretical analysis, the simulation, and the experimental testing in this paper, it is found out that thermal error is determined by multiple variables, such as the temperature, the spindle rotation speed, the historical spindle temperature, the historical thermal error, and the time lag between the present and previous times. In order to examine the performance of thermal error models based on multiple variables, two common methods are used for modeling—the multiple regression method and the back propagation network. The data for modeling are collected from experiments conducted on the spindle of a precision machine tool under various working conditions. The modeling results demonstrate that models established based on the multiple variables have better accuracy and robustness. It also turns out that data filtering before modeling can further improve the performance of the models. Therefore, models based on multiple variables with good accuracy and robustness can be very useful for the further thermal error compensation. In addition, by taking relative importance analysis of multiple variables based on standardized regression coefficients, the influence of each variable to the thermal error is revealed. The ranking of coefficients can also be used as a new criterion for the optimal temperature variable selection in the future research.

Description: The way workstations are located in a tandem automated-guided vehicle (AGV) systems affect the total lateness of the system. So far, almost all studies have focused on either minimizing the total flow or minimizing the total AGV transitions in each zone. This study presented a novel approach to locate the workstations in a tandem AGV zones by developing a new mixed-integer programming (MIP) formulation. The objective is to minimize total waiting time of all workstations which is equivalent to minimizing the total lateness of each zone. Lateness is defined as the total idle time of a workstation waiting to be supplied by an AGV. The proposed MIP formulation is very competitive and has the capability to solve instances of up to 25 workstations to optimality in a reasonable amount of time.

Description: In this study, orthogonal cutting of SiCp/Al composites with a polycrystal diamond tool has been carried out. The influences of cutting velocity, cutting depth, and tool rake angle on the cutting force and edge defects near the exit of orthogonal cutting were analyzed in detail. The research results show that the influence of the cutting depth on cutting force is most obvious, and there is a close relationship between the cutting force and the size of edge defects. At the same time, the fractographs indicated that the brittle fracture mode corresponds to the dominant failure mode during machining of SiCp/Al composites with higher volume fraction and larger SiC particle. Therefore, in the precision and super-precision manufacturing of SiCp/Al composites, with a proper tool rake angle, adopting higher cutting velocity and lower cutting depth not only can reduce the cutting force effectively but also can ensure cutting edge quality.

Description: This study investigated the influences of dielectric characteristics, namely, electrical conductivity, oxidability, and viscosity on the electrical discharge machining (EDM) of titanium alloy. A new kind of compound dielectric with optimal processing effect was developed based on the identified effects. Comparative experiments on titanium alloy EDM in compound dielectric, distilled water, and kerosene were performed to analyze the difference in material removal rate (MRR), relative electrode wear ratio (REWR), and surface roughness (SR). The experimental results revealed that titanium alloy EDM in compound dielectric achieved the highest MRR, a lower REWR than that in kerosene, and better SR and fewer micro-cracks than that in distilled water.

Description: This paper introduces the composite tool electrodes made of electrical conductive powder-filled polyester resin matrix material, providing promise for the electrical discharge machining (EDM) process. The dendrite-shaped copper powder, graphite powder, and their mixture were used as conductive fillers. Six different types of composite electrodes, namely, plain copper-polyester, pressed copper-polyester, furnaced copper-polyester, plain copper-graphite-polyester, pressed copper-graphite-polyester, and furnaced copper-graphite-polyester were prepared. It is found experimentally that increasing v f improved workpiece material removal rate, tool wear rate, relative wear, and electrical conductivity of electrodes. The pressed copper-polyester electrodes were found to be promising in the ED finishing of workpieces at low machining current settings. The practical applicability of the proposed composite electrodes in the industry was also illustrated.

Description: A theoretical model based on slab method is proposed to analyze asymmetrical rolling of bonded two-layer sheets where the ingoing sheet is forced to horizontally enter the roll gap. Separate equilibrium equations as well as yield relations are derived for each layer by considering different stress fields for the two layers of any slab within the roll gap. A large angle of bite is considered in the governing equations as the experimental data used for verifying the results belong to the rolling conditions where small bite angle assumption is not reasonable. The curvature of the sheet at exit from the roll gap is estimated by studying variations of the normal and the shear strains within the whole roll gap. A very good agreement is shown to exist between the rolling force as well as the outgoing curvature predicted by the present model and the available analytical and experimental results reported by other investigators. By studying the outgoing curvature at different conditions, some practical suggestions to minimize the strip curvature at exit from the roll gap are proposed.

Description: In this paper, dry machining experiment of Ti-6Al-4 V was carried out to investigate the machining performance of a grooved tool in terms of its wear mechanisms and the effects of cutting parameters (cutting speed, feed rate, and cutting depth) on tool life and surface roughness of the machined workpiece. The results showed that chip-groove configuration substantially improved the machining performance of cutting tool. The main wear mechanisms of the grooved tool were adhesive wear, stripping wear, crater wear, and dissolution-diffusion wear. The resistance to chipping was enhanced due to the decrease of contact pressure of tool-chip interface. And the resistance to plastic deformation of tool nose was weakened at the cutting speed of more than 60 m/min. The appropriate cutting speed and feed rate were less than 70 m/min and 0.10 mm/r, respectively. With cutting speed increasing, the surface roughness of machined workpiece decreased. A high feed rate helped the formation of higher surface roughness except 0.21 mm/r. When cutting depth increased, tool nose curvature and phase transformation of workpiece material had great impact on surface roughness.

Description: In this paper, a more general version of the flow shop scheduling problem with the objective of minimizing the total flow time is investigated. In order to get closer to the actual conditions of the problem, some realistic assumptions including non-permutation scheduling, learning effect, multiple availability constraints, and release times are considered. It is assumed that the real processing time of each job on a machine depends on the position of that job in the sequence, and after processing a specified number of jobs at each machine, an unavailability period is occurring because of maintenance activities. Moreover, it is supposed that each job may not be ready for processing at time zero and may have a release time. According to these assumptions, a new mixed integer linear programming (MILP) model is proposed to formulate the problem. Due to the high complexity of the problem, a heuristic method and a simulated annealing algorithm are presented to find the nearly optimal solutions for medium- and large-sized problems. To obtain better and more robust solutions, the Taguchi method is used in order to calibrate the simulated annealing algorithm parameters. Finally, the computational results are provided for evaluating the performance and effectiveness of the proposed solution methods.

Description: The weldability of titanium and nickel using micro spot brazing technology was successfully investigated. Brazing was performed using a 4-kA welding current, 2-V voltage, 60-N load, and a 25–50-ms welding time. An alloy filler metal, specifically a 0.1-mm thick foil with a composition of 71Ag-28Cu-1Mg, was sandwiched between Ti and Ni. The three electrode copper tip shapes that were investigated in this study were circular-, rectangular-, and ring-shaped tips. The weldability of the joint was evaluated in terms of the fracture load, weld size, shear strength, and micro hardness. A high joint strength was obtained in the case of the 71Ag-28Cu-1Mg filler when a rectangular electrode tip face was used.

Description: The paper reports on the modeling and respective experimental validation for the formation of the machined subsurface layer in turning with nose-radiused and round tools. An experimental work on the mechanisms of work-hardening of the machined surface and related wear of the cutting tools was conducted for high-speed turning of aged Inconel 718 with whisker-reinforced alumina tools. The model shows that multiple deformations of the machined surface occur when machining with small feeds and tools with large nose radius, thus changing the mechanics of surface formation. Experimental results confirm the localized increase in subsurface hardness in the vicinity of the tool tip. The variation in the degree of work-hardening and the extent of the area affected by it fully agree with the predictions of the model. The model also shows that a significant part of the cutting tool may cut through the extra work-hardened material. Tool wear tests show that the local increase in workpiece hardness results in a localized increase in the wear rate of the cutting tools.

Description: This article addresses the problem of contact-state (CS) monitoring for peg-in-hole force-controlled robotic assembly tasks. In order to perform such a monitoring target, the wrench (Cartesian forces and torques) and pose (Cartesian position and orientation) signals of the manipulated object are firstly captured for different CS’s of the object (peg) with respect to the environment including the hole. The captured signals are employed in building a model (a recognizer) for each CS, and in the framework of pattern classification, the CS monitoring would be addressed. It will be shown that the captured signals are nonstationary, i.e., they have non-normal distribution that would result in performance degradation if using the available monitoring approaches. In this article, the concept of the Gaussian mixtures models (GMM) is used in building the likelihood of each signal and the expectation maximization (EM) algorithm is employed in finding the GMM parameters. The use of the GMM would accommodate the signals nonstationary behavior and the EM algorithm would guarantee the estimation of the optimal parameters set of the GMM for each signal, and hence the modeling accuracy would be significantly enhanced. In order to see the performance of the suggested CS monitoring scheme, we installed a test stand that is composed of a KUKA lightweight robot (LWR) doing peg-in-hole tasks. Two experiments are considered; in the first experiment, we use the EM-GMM in monitoring a typical peg-in-hole robotic assembly process, and in the second experiment, we consider the robotic assembly of camshaft caps assembly of an automotive powertrain and use the EM-GMM in monitoring its CS’s. For both experiments, the excellent monitoring performance will be shown. Furthermore, we compare the performance of the EM-GMM with that obtained when using available CS monitoring approaches. Classification success rate (CSR) and computational time will be considered as comparison indices, and the EM-GMM will be shown to have a superior CSR performance with reduced a computational time.

Description: Although Ti-6Al-4V titanium can be quickly and easily formed by electric hot incremental forming, the material property is the key factor for industrial application. In the current work, mechanical properties of Ti-6Al-4V sheet in one-sided electric hot incremental forming, such as microstructure, hardness, and tensile strength, were investigated. The results show that the current is obviously the most important factor to elevate temperature, so a higher feed rate can be adopted if the current is increased. In order to keep a constant processing temperature, an online temperature detector and current feedback system should be adopted. After observation and analysis of the microstructure of forming workpieces, the electric hot incremental forming is an integrated process, which involves plastic hardening and annealing. The temperature of the tool–workpiece contact side reached the β-transus one, α phase disappeared, and the basket weave structure was formed because of the fast air-cool. A composite organization with superior property which includes elongated α phase grains and basket weave structure can be acquired by one-sided electric hot incremental forming. If a uniform metal structure is obtained, special heat treatment must be adopted. Micro-hardness analysis shows that electric hot incremental forming is an enhanced processing. In order to improve the tensile strength, the oxidation of sheet must be prevented and inert gas protection should be adopted in future research.

Description: Whilst powder injection moulding (PIM) of metal or ceramic parts is a favourable technique for producing complex geometries, there are still limitations concerning undercuts, closed cavities or mobile connections. In this paper, a sinter-joining technique of stainless steel parts is presented using the example of a microcheck valve. The valve was produced by an automatic assembly of two powder injection-moulded housing parts and an incorporation of a ceramic ball during the assembly step. The subsequent sintering process allowed fusing single particles and densifying the check valve. To evaluate the quality of the joining step, the contact area was investigated microscopically, and internal pressure tests were performed. The results revealed that a dense contact area can be achieved by using suitable sintering parameters which in turn leads to internal pressure values higher than 700 bar.

Description: This paper introduces balanced location–allocation design problem to tackle a real-world health-care application. The problem involves strategic decisions on locating a predefined number of facilities and allocating a set of customers to the facilities such that minimizes total travel, operating and congestion costs in an uncertain environment. To face more appropriately with the uncertainties, a comprehensive model which takes into account all sources of uncertainty is proposed. Moreover, in order to have a balanced use of installed capacities and/or reduce delays in servicing, congestion-related costs are defined as a power-law function of the trespassed facility’s operating capacity. The developed model is extremely hard to solve because of its inherently high combinatorial nature combined with the uncertainties and the nonlinearities associated to the congestion. Therefore, a new search mechanism based on variable neighborhood search is put forward. This algorithm employs both random and mathematical programming techniques to generate a set of initial solutions. On the other hand, to examine the quality of each move, a linear model which is scenario decomposable is extracted. The validation of the model is studied on an existing application, and the algorithm’s performance is tested on a wide range of instances taken from literature.

Description: Lean is a well-approved strategy to enhance quality, improve productivity, and reduce cost via eliminating all non-value-added activities. The absence of a standard model for implementing lean and the strong need for a “road map” or “systematic approach” that set the priorities of enterprise’s perspectives for improvement are essential for enterprise success. A lean radar score (LRS) alone is not enough to define the perspective priorities for improvement to achieve the leanness condition. Other elements have to be considered in order to have the optimum route of implementing lean, including cost, benefits, time of completion, technological capabilities, administrative constraints, and the degree of involved risk. Based on that, an integrated model of lean assessment and analytical hierarchy process (AHP) is proposed to define the route of lean implementation based on the perspective priorities for improvement. The proposed path is dynamic and can vary according to the situation of the enterprise. Consistency test is used to ensure that the experts’ judgment in assigning weights within the AHP model does not contain contradiction, and sensitivity analysis is used to verify the robustness of decision regarding the optimum route for lean implementation.

Description: This paper considers a three-echelon integrated production inventory model consisting of a central warehouse and a manufacturer including two independent departments as processing and assembly stages. To assemble the finished product, materials are carried to the assembly stage through two different flow channels. One group requires preprocessing in the processing stage, and the other one directly arrives from an outside supplier. Storing inventories either in a warehouse (as finished products) or in the stages (as work-in-process) and shipping them between the stages incur inventory costs that must be balanced to achieve minimum joint total cost. The central warehouse faces stochastic demand, which is assumed to be a generally distributed demand. It is controlled by continuous review ( R , Q ) policy. Additionally, warehouse ordering cost can be reduced through further investment. To analyze, we formulate a nonlinear cost function to aggregate all the costs. After, a simulated annealing algorithm has been suggested to solve the problem. Numerical experiments are presented to evaluate the performance and effectiveness of the proposed algorithm. Also, we use the branch and bound technique and a nonlinear optimization technique—generalized reduced gradient—for solving this problem. The experimental results show a fine performance of the proposed algorithm in comparison with two other methods.

Description: Supply chains usually deal with processing of returned products so that part of the customer demands can be met using the remanufactured products. Therefore, to have an effective inventory management system, it is necessary to consider the effects of the returned products on inventory policy of all involved parties in a supply chain. In this paper, a two-echelon inventory model is developed for a single reusable product in which the return rates explicitly depend on demand streams. The remanufacturing process transforms a returned product to a serviceable one. We extend the basic inventory model incorporating both manufacturing and remanufacturing processes using a continuous review inventory policy. We apply a dynamic programming approach for solving our extended model. To show the applicability of the model, a numerical example is presented. Sensitivity analysis results of the model are consistent with the expected behaviors of our developed model.

Description: Electrochemical machining (ECM) provides an economical and effective way for machining heat-resistant, high-strength materials into complex shapes that are difficult to machine using conventional methods. It has been applied in several industries, especially aerospace, to manufacture blisk. The electrolyte flow field is a critical factor in ECM process stability and precision. To improve the process stability and the efficiency of blisk cascade passages, ECM with a radial feeding electrode, a rational electrolyte flow mode for electrochemical machining called “Π shape flow mode”, is discussed in the paper. Three flow field models are described separately in this report: traditional lateral flow mode, positive flow mode and Π-shaped flow mode, and the electrolyte velocity and pressure distribution vectors for each flow mode are calculated by means of a finite element fluid analysis method. The simulation results show that the electrolyte flow is more uniform with the Π-shaped flow mode. The deformation of the cathode, which is caused by the pressure difference, is also analysed in this report. The cascade passage ECM with a radial feeding electrode was experimentally tested out to evaluate the rationality of the flow field, and the fluctuation of current during the process was less than 1 %, which means that the process that uses the Π-shaped flow mode is stable. The feeding velocity of the cathode with the Π-shaped flow mode is approximately 70 % higher than that with the other two flow modes, and the incidences of short circuiting are obviously decreased. The surface roughness of the blisk hub is only 0.15 μm, and the machining error of the hub is less than 0.1 mm. The results demonstrate that using the Π-shaped flow mode can enhance the quality, stability and efficiency of blisk cascade passage ECM.