ALBERT

Description: In an attempt to find a solution similar to the FDM 3D printers which would allow cost-effective and reliable additive manufacturing of metal components, this paper proposes a three-axis WAAM system capable of reliably printing small, near-net-shape metal objects. The system consists of gas metal arc (GMA) process equipment, a three-axis CNC positioning system, the interpass temperature control and forced cooling of the base plate and the deposit. The main challenge addressed is the minimisation of shape distortions caused by excessive heat accumulation when printing small objects. The interpass temperature control uses an IR pyrometer to remotely measure the last deposited layer and a control system to keep the interpass temperature below the predefined value by stopping the deposition after each layer in order to allow the deposit to cool. This results in a stable and more repeatable shape of the deposit, even when the heat transfer conditions are changing during the build-up process. The combination of adaptive interlayer dwell time and forced cooling significantly improves system productivity. Open-source NC control and path generation software is used, which enables fast and easy creation of the control code. Different control methods are evaluated through the printing of simple walls, and the printing accuracy is evaluated by printing small shell objects. As the results show, the interpass temperature control allows small objects to be printed at near-net shape with a deviation of 2%, which means that successful printing of 3D shapes can be achieved without trial and error approach.

Description: To prevent an overheating of the workpiece material and to increase the productivity in hot aluminum extrusion, the application of extrusion dies with conformal cooling channels manufactured additively by selective laser melting is known. Since, to date, the additive manufacturing processes are often accompanied with higher manufacturing time and costs in comparison to conventional subtractive methods, a new concept for a hybrid extrusion die is presented. Here, the large volume but geometrically simple die part, the die bridge, is manufactured conventionally by subtractive methods, and the smaller part with geometrical complexity, the tip of the mandrel, is built-up on it additively by laser melting. A further novelty of the developed die is the isolated feeding of the coolant up to the target area, close to die bearings, where the cooling shall be localized. Numerical and experimental investigations revealed that the profile’s exit temperature can be reduced locally and controlled which leads only to a moderate increase of the extrusion force. The experimental results show that the hybrid tools withstand the high mechanical and thermal loads which occur during hot aluminum extrusion.

Description: Machine tools have an impact on the environment due to their energy consumption. New strategies with focus on the reduction of the energy consumed by manufacturing processes have received significant attention owing to the rise of the electricity costs. This paper presents an experimental study related to the optimization of cutting parameters in turning of AISI 1018 steel. The aim of the study was to minimize the quantity of electrical energy required by the machine tool in order to perform the cutting operation. The material removal rate was set to a constant value in all the experimental trials so as to analyze the effect that the cutting parameters have on the energy consumed. Robust Design was used to determine the effects of the depth of cut, feed rate, and cutting speed on the energy required by the machine tool, considering two sources of noise in the experimental trials. The results of this work show that the techniques covered by the concept of Robust Design can be used to minimize the energy consumed and variation of the machining process.

Description: We propose a model for the statistical design of a variable sample size chi-squared control chart (VSS χ 2 control chart) for monitoring linear profiles. Performance measures of the proposed adaptive control chart are obtained through a Markov chain approach. Through a numerical example, which consists of a calibration application in a production process of semiconductors, the proposed chart is compared to the fixed parameter chi-squared control chart (FP χ 2 chart) to monitor the intercept and slope of the linear profile. From this example, it is possible to assess the potential benefits provided by the proposed chart. Also, considering simultaneous shifts in the intercept, the slope, and the standard deviation, a sensitivity analysis of the proposed chart for monitoring linear profiles is presented.

Description: The present investigation analyses the force and torque developing during friction stir spot welding (FSSW) of thermoplastic sheets varying the main process parameters. In addition, measurements of the tool temperature and those of the material close to the welding region were carried out to better understand the variation of the forces during FSSW and quality of the joints. Experimental tests involving an instrumented drilling machine were performed on polycarbonate sheets. The study involved the variation of dwell time, tool plunge rate and rotational speed. Mechanical characterization and dimensional analysis of the joints were performed in order to assess the influence of the process parameters on the joint quality under considered processing conditions. According to the achieved results, using low values of the plunging speed has beneficial effects on both the process (reduction in the force and torque) and the mechanical behaviour of the joints. Increasing the tool rotational speed results in reduced processing forces and higher material mixing and temperature. The dwell time has a negligible effect on developing forces while it highly influences the material temperature, dimension of the welded region and consequently the mechanical behaviour of the joint.

Description: This research studies the cellular manufacturing system (CMS) controlled by kanban mechanism which defective items are produced in any production run of each product and rework is carried out to transform them into serviceable items. We consider and compare two different policies for rework where in the first policy rework is completed within the same production cycle and in the second policy rework done after N production cycles. Recently Aghajani et al. (2012) explain policy 2 and proposed a mixed-integer nonlinear programming (MINLP) model for this policy. In order to minimize total cost, MINLP model was developed for policy 1 to find simultaneously the optimal number of kanban, batch size, and number of batches. The cost function includes the cost of setup, holding, and transportation. Due to the high combinatorial structure of the problem, particle swarm optimization (PSO), and simulated annealing (SA) algorithms as meta-heuristic methods are proposed to solve the problem and numerical experiments are conducted to demonstrate the efficiency of the proposed algorithms. It is shown that both PSO and SA result are in a near optimal solution but the PSO algorithm gives a better performance than the SA method. Also, sensitivity analysis is carried out to study the effect of defective rate, holding cost, and setup cost variations on the total system cost is discussed the performance of these policies in different conditions.

Description: Tool condition monitoring has found its importance to meet the requirement of quality production in industries. Machined surface is directly affected by the extent of tool wear. Hence, by analyzing the machined surface, the information about the cutting tool condition can be obtained. This paper presents a novel technique for multi-classification of tool wear states using a kernel-based support vector machine (SVM) technique applied on the features extracted from the gray-level co-occurrence matrix (GLCM) of machined surface images. The tool conditions are classified into sharp, semi-dull, and dull tool states by using Gaussian and polynomial kernels. The proposed method is found to be cost-effective and reliable for online tool wear classification.

Description: This study proposes a high-precision compensation system using an on-machine noncontact measuring system to improve the manufacturing accuracy and efficiency of large-diameter aspheric mirrors by reducing profile errors arising from tool setting errors and machine positioning errors. By measuring a standard hemisphere, the assembly tilt angle of the measurement sensor can be calibrated. The grinding wheel setting offset can be calculated by comparing the measured profile and the ideal profile, and the profile error caused by wheel offset can be reduced by adjusting the grinding origin coordinate. According to the normal unit vector and residual error in the Z direction of the measuring points, the normal residual errors corresponding to the grinding points could be generated as well as the compensation grinding numerical control (NC) program. An 800-mm-diameter K9 mirror was ground to verify the proposed compensation grinding method. The profile error was reduced from 65 to 35 μm during the semi-finish grinding stage. By using the compensation grinding path, the profile accuracy was improved from 35 to 8 μm in the fine grinding stage. The proposed compensation method effectively improves the profile accuracy and manufacturing efficiency for grinding large-diameter aspheric mirrors.

Description: In this paper, we will perform a comparison between two approaches of dimensional synthesis of parallel robots. The first one concerns the single-objective optimization approach; in this case, the dimensional synthesis is expressed by taking into account only one performance criterion but enables to get a final solution if it exists. The second one concerns the multi-objective optimization approach; it enables to simultaneously take into account several performance criteria. However, this approach appears to provide a set of solutions instead of a single expected final solution which should directly enable to carry out the structural synthesis. In fact, the search of a single final solution is postponed to a further step where the designers have to impose and/or restrict certain parameters. And we will establish if it is really necessary to make a multi-objective optimization approach or if a single-objective is sufficient to reach the objectives set in the specifications (user requirements). A discussion is proposed concerning the arising questions related to each approach and leading to the optimal dimensional synthesis. The PAR2 robot with two degree-of-freedom is used to exemplify the analysis and the comparison of the two approaches. The proposed comparison can be applied to any classes of parallel robots.

Description: In order to generate efficient tool path with given precision requirements, scallop height should be kept under a given limit, while the tool path should be as short as possible to reduce machining time. Traditional methods generate CC curves one by one, which makes the final tool path far from being globally optimal. This paper presents an optimal tool path generation model for a ball-end tool which strives to globally optimize a tool path with various objectives and constraints. Two scalar functions are constructed over the part surface to represent the path intervals and the feedrate (with directions). Using the finite element method (FEM), the tool path length minimization model and the machining time minimization model are solved numerically. The proposed method is also suitable for tool path generation on mesh surfaces. Simulation results show that the generated tool path can be direction parallel or contour parallel with different boundary conditions. Compared to most of the conventional tool path generation methods, the proposed method is able to generate more effective tool paths due to the global optimization strategy.

Description: Ultrasonic-assisted grinding, a promising processing technique for machining hard and brittle materials, is already quite extensively employed in manufacturing industries. However, the material removal mechanism in ultrasonic-assisted grinding is not yet fully understood, which hinders its further application. This study investigates the material removal process in ultrasonic-assisted scratching (UAS) of SiC ceramics using both simulation and experiment method, in order to detail the material removal mechanism in ultrasonic-assisted grinding. A conventional scratching (CS) test was also carried out, but without ultrasonic vibration for comparison. The simulated workpiece is modeled by smooth particle hydrodynamic (SPH) particles. Results show the following: (1) the SPH method is suitable to investigate the material removal mechanism during ultrasonic-assisted grinding of hard and brittle materials. (2) The profile of scratching trace in ultrasonic vibration (UV) is a sinusoidal path. UV vibrating in the direction vertical to the workpiece results in material removed in either a continuous or a discontinuous mode. UV vibrating in the direction parallel to the workpiece expands the cutting area. (3) The groove depth in UAS is much bigger than that in CS. (4) UV results in the impact of the abrasive grain on the workpiece, causing the deformation field to spread from the impact site and leading to deeper scratching depths and larger radial and lateral cracks.

Description: With the emergence of new materials, personalized requirements for product performance, and new application background in polymer material industry, a new manufacturing mode is supposed to be studied. Based on cloud computing (CC) and big data techniques, a specific cloud manufacturing (CMfg) mode of polymer material industry has been proposed, which is different from that of continuous industries and that of discrete industries. The critical technologies of CMfg, including forecasting and demand management, storage and transportation management, advanced process control, manufacturing execution system, enterprise resource planning, etc., have been discussed. Besides the service composition optimal-selection (SCOS) algorithm for flexible manufacturing and the flexible polymer manufacturing system (FPMS), a typical product mode of CMfg is studied. Finally as a case, computer-aided process planning for blending material (CAPP-BM) was explored and a kind of fast searching algorithm for blending material crafts was proposed. The algorithm was applied to search target craft in more than 60,000 sections of the standard processes, production data, and environmental data, and finished its search within 10 min.

Description: In this paper, an inverse heat conduction method is applied to estimate the amount of the energy ( F c ) transferred to the workpiece during electric discharge machining (EDM) process. Embedded thermocouples which were connected to a four channel data logger were utilized to measure the temperature of a specific location on a rectangular workpiece during the EDM process. After temperature measurements were done, the 2-D heat conduction model of the workpiece and the Levenberg-Marquardt (LM) scheme were used to determine the energy transferred to the workpiece. This inverse procedure facilitates the determination of the heat energy at discharge-workpiece interface in EDM processes, which yet is a challenge for existing numerical models. The obtained results showed that the energy transferred to the workpiece varies with the discharge current and pulse duration from 5 % up to 45 %, which shows that the value of F c is a function of discharge current and pulse duration and that the fixed value of energy assumed in majority of the previous researches is not in accordance with real EDM conditions. Furthermore, the effects of machining parameters such as discharge current and pulse duration on F c were studied. It was evident that the F c has a direct but non-linear relationship with both discharge current and pulse duration, while discharge current has a higher impact on F c .

Description: Thermal errors are major contributor to dimensional errors of a part during precision machining. Error compensation is an effective method to reduce thermal errors. Accurate modeling of thermal errors is a prerequisite for thermal error compensation. In this paper, five key temperature points of a computer numerical control (CNC) machine tool were selected based on grey relational analysis method (GRAM). One thermal error model based on the five key temperature points was proposed using artificial fish swarm and ant colony algorithm-based back-propagation neural network (AFSACA-BPN). AFS is applied to generate initial pheromone value of ACA, which improves the computational efficiency of BPNs and prediction accuracy of thermal error modeling. One thermal error real-time compensation system was developed based on the proposed model. An experiment was carried out to verify the performance of the compensation system. Experiment results show that the diameter error of the workpiece reduced from 23 to 10 μm after compensation.

Description: Experimental and viscoplastic finite element analysis (FEA) of thermo-mechanical plastic deformation in nonisothermal warm deep drawing is studied using SS304. A nonisothermal deep drawing tool is used in a servo-motor-controlled press. Drawability window of SS304 under elevated temperatures (25–225 °C) and low to high strain rates (drawing speeds of 2.5, 25, and 50 mm/s) were determined. A viscoplastic thermal material model is adopted for nonwork softening material behaviors, as seen in low-temperature forming of SS304, and found to be easily applicable and quite satisfactory. Tensile and equi-biaxial bulge tests were conducted for more accurate flow stress data to be used in FEA. Measured punch load–stroke and cup’s curvilinear thickness (rolling/transverse) curves were successfully compared with predictions from the nonisothermal FE model of the warm deep drawing.

Description: In this article, the effect of cooling media on the residual stresses (RS) induced by a solid-state welding process is scrutinized through measuring and comparing RS caused by friction stir welding (FSW) underwater and in open air using the non-destructive ultrasonic method for aluminum AA7075-T6. Underwater FSW as a solid-state welding method can extend the application of solid-state welding techniques in marine industry. Results reveal that the longitudinal and transverse RS reduce under the water compared to open air. This reduction in the longitudinal RS is the maximum within the nugget zone (about 17 %). Meanwhile, such reduction for the transverse RS reaches 70 % within the heat-affected zone. In addition, under both air and water, the longitudinal RS is several times greater than the transverse RS and is in tensile and compressive states inside and outside the nugget zone, respectively.

Description: Machining-induced residual stress is important for the part performance. In the literature, various predictive models have been proposed for residual stress in one-pass machining without considering the multi-pass aspect. This study describes the regeneration of residual stress in multi-pass machining with thermo-mechanical loadings, in the full elasto-plastic state, captured using the Neumann-Duhamel principle. The residual stress is then analysed satisfying elastic-plastic relaxation in-between layers and at the boundaries. Large experimental data in milling of AA2121-T3 agreed well with model predictions, thus supporting the consideration of initial stress functions, materials cyclic plasticity and compatibility to allow for residual stress prediction in multi-pass machining.

Description: Different calibration strategies based on network measurements have been studied to improve the accuracy of a laser tracker having the beam source in the rotating head, thus allows us to determine if nominal distances are needed. Moreover, the minimum gauge needed to ensure a calibration valid result is characterised. First, the laser tracker calibration performance, using only network measurements without any nominal data known, has been studied. Different strategies have then been carried out, using reflector gauges as nominal data in the calibration procedure to determine the more suitable gauge in terms of accuracy and efficiency. The reflectors have been measured from different positions of the laser tracker. The gauge reflectors have been measured too with a coordinate measuring machine for obtaining the nominal data. The objective function to be minimised in the identification parameter procedure has been developed for every strategy for the distance criterion (distances between every pair of reflectors must be constant regardless of the laser tracker position from which they are measured). Then, two criteria, distance criterion and coordinate criterion (the reflector positions measured by the laser tracker are expressed in the same reference system and are then compared), have been used to evaluate the calibration performance. The analysis developed shows the improvement accuracy of every strategy studied.

Description: Crystallographic texture considerably affects the formability of crystalline materials. In this paper, the effects of BCC ideal rolling fibers—including α ,

Description: In the processing of large and ultra-large forgings, the heated billets need to be properly placed on the lower forging die as quickly as possible before the plastic forming, or else the cooling of billets incurs enormous risks to the operation. This paper presents a novel methodology for examining the positioning status of billets on a forging die based on multi-body dynamics simulation and design of experiment (DOE). Using this method, the position and posture of a billet can be theoretically predicted after falling into the cavity of lower die from a manipulator with varying initial states. The method can also clarify the initial geometrical position parameters of the billet that should be strictly controlled in the operation of the manipulator above the lower die. Furthermore, finite element method (FEM) simulation can be used to analyze plastic deformations of the billets on the lower die surface with varying states, to attain in-depth understanding of the influence of the geometric states of billets in forming processes. A case study of forging with Al 7050 indicates that the method can provide a valuable reference for the rapid positioning of billets on the lower die.

Description: The ANSYS software is used to establish the electromagnetic-structural coupling model and predict the electromagnetic sheet forming process. In comparison with experimental result, the maximum simulation error, about 4.5 %, occurs at the sheet center. Then, the simulation method is used to analyze the effect of discharge voltage on thickness distribution. The results indicated that the location of the maximum thickness reduction transfers from sheet center to the region near the sheet center (A region) and then to the region corresponding to the die corner (B region) with the voltage increases, which also cause the first principle strain changed. In addition, lager magnetic force and the material at sheet flange restrained to flow are the two reasons for the thickness reduction at B region. While the direction of material flows changed by inertial effect is the reason for thickness reduction at A region.

Description: In this paper, the formability of two-layer (aluminum-st12 steel) sheets in the deep drawing process was investigated through numerical simulations and experiments. The purpose of this research was to obtain more formability in deep drawing process. The limit drawing ratio (LDR) was obtained in deep drawing of two-layer metallic sheets, with aluminum inner layer which was in contact with the punch and steel outer layer which was in contact with the die. Finite element simulations were performed to study the effect of parameters such as the thickness of each layer, value of die arc radius, friction coefficient between blank and punch, friction coefficient between blank and die, and lay up on the LDR. Experiments were conducted to verify the finite element simulations. The results indicated that the LDR was dependent on the mentioned parameters, so the LDR and as a result the two-layer metallic sheet formability could be increased by improvement of these parameters in deep drawing process.

Description: This study aims to investigate two peel demolding schemes through numerical simulations and experimental studies in order to improve the yield rate of the automated system for demolding of the polydimethylsiloxane (PDMS) micropillars with aspect ratio of 6. Numerical models based on the explicit dynamic finite element analysis by using LS-DYNA are developed to identify an optimal demolding scheme which can minimize the maximum stress of microstructures during demolding. A scale-up modeling approach is proposed to increase the numerical time-step for microscale problems in order to reduce the computational time. The experimental tests are also carried out which agree with the findings from numerical simulations. From this study, the roller-based demolding system is identified as the optimal approach in our analysis cases which can minimize the distortion and collapse of micropillars. The yield rate of the roller-based demolding system in our experimental study can be up to 99 %.

Description: The size effect in cutting process that the specific cutting energy increases rapidly and nonlinearly as the undeformed chip thickness (UCT) decrease is discussed. To facilitate the discussion, the specific cutting energy is analyzed by separating the cutting mechanism into two parts: shearing and extrusion. The size effect of materials such as dislocation starvation was introduced to explain the increase of specific cutting energy. In conventional cutting, shearing dominates the size effect. And as the UCT reduces, the effect of tool radius is not ignorable, and extrusion participates more in describing the size effect. When the UCT is on the nanometric scale, extrusion dominates the cutting process. Besides that, the cutting energy was further separated into surface generation energy, material disorder energy, and heat generation energy. Each of them was discussed individually. The results show that the size effect of materials plays a major role in the change of specific cutting energy. And the other aspects like surface generation and material disorder also determine the size effect in cutting process.

Description: Based on the crack mechanism of hot forming, the causes of cracks occurring during the hot forming of complex structural parts were investigated in this study. High temperature flow stress model of ultrahigh strength steel (UHSS) BR1500HS was established using the true stress–strain curves of BR1500HS in high-temperature tensile. A finite element model (FEM) was built to investigate the causes of defects in hot forming, particularly the necking occurring at the end parts in plan stress status. Then, hot forming process and structure optimizing methods were proposed. According to the results of numerical simulation, it can be concluded that the indirect hot forming process can avoid forming defects and optimize preforming drawing height to 24.5 mm. Through changing the end size of blank to control the metal flow, crack occurring at the end of parts can be solved, since the material in two-way tensile stress state can flow compensation in one direction and therefore reduce the flow resistance. The experimental results are in good agreement with numerical simulation results, which indicates that the proposed method can avoid defects and meet the design requirements.

Description: The deforming zone in the die determined by the cross-sectional shape of the final product plays a key role in the extrusion process affecting the extrusion pressure and product quality. Therefore, prediction of the optimal profile of the deforming region is the main objective for an effective extrusion process. In this study, using the analogy between the conventional plasticity theorem and electrostatics, the notion of equi-potential lines (EPLs) was applied to accurate representation and 3D design of the deforming region in the extrusion process of a complex section. To implement the analogy in the extrusion, the initial and final shapes were considered, and two different potentials were assigned between the inlet and outlet surfaces. Then, the EPLs were drawn that show the minimum work path between the entry and exit sections. The drawn EPLs were connected to build up a 3D-profile for the deforming region in the extrusion process. In addition, the EPLs were used in accurate representation of the deforming region using high-order polynomial curves. The effectiveness of the proposed method was examined using a complex section (U-shaped) from the literature. Then, the extrusion pressure for different profiles in the deforming region was analyzed numerically and experimentally. Moreover, the obtained polynomial curves were used in the upper bound (UB) solution for prediction of the extrusion pressure. There were reasonable agreements between the analytical, numerical, and experimental results. An acceptable reduction in the extrusion pressure for 3D modelling of the deforming region with the EPLs was reported. It was shown that the EPLs could be used for accurate representation of the deforming region in the extrusion of complex sections.

Description: In this study, induction brazing was performed on diamond grits coated with amorphous NiCrBSi alloy (1.6-μm thick) deposited by physical vapor deposition (PVD). The brazing alloy exhibited better wetting toward the coated diamond grits than toward the uncoated diamond grits during induction brazing. The fine chromium-carbon compounds were evenly distributed between the brazed diamond grits with coating and the brazing alloy. However, the bulky chromium-carbon compounds were unevenly distributed between the brazed uncoated diamond grits and the brazing alloy. Cylindrical grinding of casting aluminum ZL102 plate with thickness of 15 mm was also performed using the brazed diamond burs fabricated with the coated diamond grits and uncoated diamond grits, respectively. The falloff percentage of brazed coated diamond grits was lower than that of brazed uncoated diamond grits. Accordingly, the temperature of processing arc area of the brazed diamond bur fabricated with the coated diamond grits was lower than that of the brazed diamond bur fabricated with the uncoated diamond grits, and its rate of removal of material was higher than that of the brazed diamond bur fabricated with the uncoated diamond grits.

Description: When machining titanium alloys at cutting speeds higher than 60 m/min using cemented carbide cutting tools, the tool wears out rapidly. With the ever-increasing use of titanium alloys, it is essential to address this issue of rapid tool wear in order to reduce manufacturing costs. Therefore, the intention of this study was to investigate all possible tool wear mechanisms involved when using uncoated carbide cutting tools to machine Ti6Al4V titanium alloy at a cutting speed of 150 m/min under dry cutting conditions. Adhesion, diffusion, attrition, and abrasion were found to be the mechanisms associated with the cratering of the rake surface of the cutting tool. The plastic deformation of the cutting edge was also noticed which resulted in weakening of the rake surface and clear evidence has been presented. Based on this evidence, the process of the formation of the crater wear has been described in detail.

Description: Temperature and material flow behavior during friction spot welding of Alclad 7B04-T74 aluminum alloy were studied by both numerical simulation and welding experiment. The Alclad 7B04-T74 aluminum alloy sequentially experienced solid solution treatment at 465 °C, low temperature artificial aging at 120 °C, and high temperature artificial aging at 180 °C. During welding, the material which flowed into the sleeve cavity suffered from higher temperature, and the peak temperature in the stir zone was higher than the incipient melting temperature of the base material. Accordingly, the eutectic films along the grain boundaries can be observed in the stir zone after welding. The peak temperatures in the thermo-mechanically affected zone and the heat affected zone were lower than the solution temperature and higher than the artificial aging temperature of the base material. In the sleeve retreating stage of the welding process, the material in the sleeve cavity flowed downward out of the sleeve cavity, and then it flowed laterally and upward to fill the gap left by the retreating sleeve. Such a material flow path resulted in the “U-shaped” morphology of the bonding ligament, the upward curving of the hook, and the upward distortion of the grains in the thermo-mechanically affected zone.

Description: In order to reduce the adverse effects on environment and avoid health problems caused by the excessively used cutting fluids, a green machining technology, minimum quantity lubrication (MQL), is drawing more and more attention. The cryogenic minimum quantity lubrication (CMQL) technique which combines the advantages of cryogenic air and MQL can improve cooling and lubricating performances during machining H13 steel. Internal cooling cutters have been widely employed to feed the cutting medium to the cutting zone directly. In this research work, cutting forces and tool wear were analyzed during side milling H13 steel with three kinds of internal cooling milling cutters under CMQL condition. The experimental results showed that the milling cutter with double straight channel (DSC) performed best in extending tool life and reducing cutting forces. In the perspective of economy and environmental protection, internal cooling cutter with DSC is recommended in cutting of H13 steel under CMQL condition.

Description: Considering the traditional power amplifier has the disadvantage of poor reliability and flexibility, a three-level pulse-width modulation (PWM) power amplifier which is based on a novel field-programmable logic gate array (FPGA) algorithm and hardware solution is proposed. The power amplifier can provide various signals flexibly and realize rapid response of the magnetic suspension spindle in micro-electrical discharge machining (EDM). In this paper, the principle of three-level PWM amplifier with half bridge and full bridge power circuit is introduced. According to different functions, the amplifier is divided into four function modules which include PWM signal generator module, voltage signal convert module, bootstrap drive module, and power bridge module. PWM signal generator module is also divided into four sub-modules in term of a new FPGA algorithm. Voltage signals are converted by high-speed photo coupler HCPL-2630. IR2110S chips are applied to drive the half bridge and full bridge power circuits. According to Kirchhoff voltage law, when the period of PWM signals is 50 μs and the duty cycles are larger than 0.76 and 0.665, the average current of half bridge and full bridge are more than 3 and 4 A; however, the ripple of the half bridge and full bridge are still less than 0.25 and 0.2 A, this advantage is suitable for the control system of magnetic suspension spindle. Test results of the average current and ripple are close to theoretical value. The axial response frequency of the spindle can reach 125 Hz, using this power amplifier and the magnetic suspension spindle, micro EDM can be achieved in Z axis with 1.2 mm stroke.

Description: This paper presents an improved methodology for evaluating the position and orientation errors of airfoil sections of a manufactured aero-engine blade. The existing method estimates these errors by finding rigid-body transformations with translational and rotational parameters altogether to best match the inspection data points onto the design airfoil profiles. Such transformations lead to unreliable evaluation results due to combining the position and orientation errors with each other. This paper proposes to decouple the position and orientation errors in their evaluation in order to avoid the combining effect. To isolate the position error from the orientation error, an important location tolerance evaluation feature, the centroid of a manufactured airfoil section, must be correctly identified from the sectional inspection data points. Identifying the centroid location directly from discrete data points is subject to an error caused by biased area calculations on the pressure and suction sides of an airfoil. This work proposes to reconstruct a valid airfoil profile from the inspection data points for each airfoil section to overcome the area bias problem and to maintain consistency in identifying the centroid. With the centroid of each inspected airfoil section identified, the position error and the orientation error can then be evaluated in sequence. A series of case studies has been performed to demonstrate the effectiveness of the proposed methodology and how it is able to prevent wrongful rejection/acceptance of geometrically acceptable/unacceptable blades as well as incorrect modification of the related manufacturing processes.

Description: A three-dimensional (3D) micromechanical finite element (FE) model of machining of fiber-reinforced polymer (FRP) composites was developed in the paper. The FE modeling considers the three phases of a composite, in which the interphase between the fiber and matrix can realize interfacial debonding to represent the failure of composites and allow heat transfer. The machined surface observations and surface roughness measurements of carbon fiber-reinforced polymer (CFRP) composites at different fiber orientations were done firstly, and then, the model predictions of the machining responses, such as cutting force, temperature, and surface roughness, at different fiber orientations were compared with various experimental data for model validation. It is indicated that the three-phase micromechanical model is capable of precisely predicting machining responses and describing the failure modes of fiber shearing or bending related with fiber orientations in the chip formation process. To investigate the complex coupling influences of multiple machining parameters on the key responses of CFRP composites, the single-factor analyses of each machining parameter were first carried out, and then, the multi-factorial analysis of multiple machining parameters was performed based on the orthogonal design of experiment and the analysis of variance (ANOVA) to quantitatively compare the influences of these key machining parameters on the cutting force and surface roughness. It was found that the fiber orientation angle, depth of cut, and cutting speed prove to be the important factors affecting the cutting force and surface roughness and that the coupling effects of these machining parameters all are relatively negligible in the machining of CFRP composites.

Description: Assembly system complexity, especially welding system complexity introduced by auto-body product personalization is regarded as a major contributor of uncertainty in the system planning and designing. The welding system complexity is defined based on information entropy theory, the station-level integrated complexity model, and system-level complexity flow model are established to obtain the complexity source of welding system. Complexity source sensitivity indices are proposed to indentify key station and key equipment that contribute most to the complexity. Based on the application of auto-body side welding line case, the result indicates that the proposed complexity model and key complexity source identifying and diagnosing process can be used as the decision support tool of auto-body welding system.

Description: Single point incremental forming (SPIF) is a relatively new manufacturing process that has been recently used to form medical grade titanium sheets for implant devices. However, one limitation of the SPIF process may be characterized by dimensional inaccuracies of the final part as compared with the original designed part model. Elimination of these inaccuracies is critical to forming medical implants to meet required tolerances. Prior work on accuracy characterization has shown that feature behavior is important in predicting accuracy. In this study, a set of basic geometric shapes consisting of ruled and freeform features were formed using SPIF to characterize the dimensional inaccuracies of grade 1 titanium sheet parts. Response surface functions using multivariate adaptive regression splines (MARS) are then generated to model the deviations at individual vertices of the STL model of the part as a function of geometric shape parameters such as curvature, depth, distance to feature borders, wall angle, etc. The generated response functions are further used to predict dimensional deviations in a specific clinical implant case where the curvatures in the part lie between that of ruled features and freeform features. It is shown that a mixed-MARS response surface model using a weighted average of the ruled and freeform surface models can be used for such a case to improve the mean prediction accuracy within ±0.5 mm. The predicted deviations show a reasonable match with the actual formed shape for the implant case and are used to generate optimized tool paths for minimized shape and dimensional inaccuracy. Further, an implant part is then made using the accuracy characterization functions for improved accuracy. The results show an improvement in shape and dimensional accuracy of incrementally formed titanium medical implants.

Description: In electrical discharge machining (EDM) process, one of the most important aspects is the surface quality of the workpiece. When a uniform and thick recast layer is achieved with characteristics of low roughness, high hardness, and the absence of pores and micro-cracks, it acts as a kind of coating. Such surface is required by mold-making industry, where the molds are subjected to chemical and abrasive wear, and the surface needs to present high resistance against corrosion and abrasive forces. The use of powder particles suspended in the dielectric is a way to provide such improvement and, at the same time, avoiding the need for subsequent polishing. This work investigated the influence of silicon and manganese powders with fine particle sizes, using two different concentrations, suspended in the dielectric when EDM machining AISI H13 tool steel. It evaluated the surface roughness, hardness, and the chemical composition and micro-structure of the recast layer; using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) techniques. The best results were obtained for silicon powder; presenting the surface roughness improved about five times, when compared to the conventional EDM process, as well as a thick and uniform recast layer without micro-cracks and pores. The silicon and the manganese powders also promoted an increase of the recast layer hardness of about 40 % when compared to the conventional EDM process.

Description: It has been proven that error compensation is a key technique to improve machining accuracy. However, existing iteration and recursive compensation algorithm is difficult to realize. Hence, a simple and rapid compensation method is considerably necessary for engineering application. In this paper, a novel compensation strategy just by algebraic operation was first proposed for machining accuracy improvement. Error motion transformation was introduced to build the position-independent geometric error (PIGE) model according to homogeneous transformation matrix (HTM). Then, the analytical numerical control (NC) code expression with error compensation was derived and used for NC code generation. In addition, the presented method is appropriate for post-processing of non-orthogonal machine tool. At last, simulation and cutting experiment were demonstrated to verify the feasibility and effectiveness of the proposed method. Taking hemisphere surface as the test object, the simulation results showed that the effects of PIGEs could be eliminated by the proposed method. The experiment results with compensation indicated that the machining accuracy improved to about 14 % compared with those without compensation.

Description: The study aims to obtain the effect of forming parameters on multi-stage cold forging with 20MnTiB steel by performing a series of physical simulation and then verified by producing experiment of high-strength bolt. Physical simulation was performed through Gleeble 3500 compression tests; the mainly forming parameters such as strain rate (10 0 ∼10 1 ), deformation degree (20∼80 %), and number of stages were discussed. The results showed that the strain rate has little effect on the microstructure and the mechanical property. However, the number of stages and the deformation degree have an appreciable effect on the sample microstructure, of which the pearlite grain is fined and ferrite grain is elongated as fiber. The adiabatic thermal temperature rises from 20 to 142 °C with a 60 % deformation degree at a strain rate of 10 s −1 . Finally, the deformation properties of bolts can compare with the physical simulation results.

Description: In this paper, a visual, data-driven operational level lean maturity model is developed. The model can be used to assess level of lean maturity and to compare it to performance results in different axes of manufacturing cells in order to evaluate lean effectiveness. As demonstrated in this paper, to measure effectiveness of lean manufacturing, both inputs (tools and processes) and outputs (performance) are measured separately and analyzed together. A case study is carried out for gathering data, analysis, and explanatory study of results. Qualitative and quantitative data on lean capability and performance of two manufacturing cells is collected using historical data and audit. A scoring system based on the major and minor non-conformances is suggested to quantify the indicators of leanness. Minimum of fuzzy membership values is selected to calculate overall performance. Then, the results of leanness are compared with performance to highlight the gaps of lean effectiveness. Results of the study show that the developed model can be used to measure both leanness and lean effectiveness through assessment of lean performance. The model can be applied by practitioners as a framework to design and develop a company-specific lean maturity model.

Description: The wall thickness of hollow turbine blade has emerged as a significant cause of blade retirement. The precision of the final wall thickness of blade is mainly inherited from its corresponding wax pattern. The layout scheme of ceramic locators has a great influence on the wall thickness of wax pattern. A good layout of ceramic locators can significantly reduce the wall thickness shifting. To address this issue, a stable locator layout is needed to reduce the error transferring. The main purpose of this study is to find an optimal localization scheme for ceramic core. Firstly, the mathematical model of ceramic core localization was built based on the fixture design theory. Then, the optimal algorithm of locator layout design was studied. The D-optimality criterion has been chosen as optimal design criterion. Finally, two demonstration cases were presented. A localization scheme for real ceramic core was achieved and verified by using Monte-Carlo method. Moreover, the localization scheme was validated through experiments. Both simulation and experimental results indicated that the optimal localization can significantly reduce the input error.

Description: Inaccuracies in conventional tolerance characterization methods, which are based on worst-case and root-square-error methods, as well as inefficiencies in Monte Carlo computational methods of statistical tolerance analysis, require an accurate and efficient method of statistical analysis of geometric tolerances. Here, we describe a unified error distribution model for various types of geometric tolerance to obtain the distribution of the deviations in different directions. The displacement distributions of planes, straight lines, and points are analyzed based on distributions within tolerance zones. The distribution of the displacements of clearance fits is then determined according to the precedence of the assembly constraints. We consider the accumulated assembly variations and displacement distributions, and an analytical model is constructed to calculate the distribution of the deviations of the control points and the process capability index to validate the functional requirements. The efficiency of the method is shown by applying it to the assembly of a single-rod piston cylinder. The results are compared with other statistical methods of tolerance analysis. We find an improvement of approximately 20 % in tolerance analysis, and the process capability index of the assembly procedure was reduced by 10 %.

Description: This paper aims to reveal the material removal mechanisms of the elliptical vibration cutting (EVC) and present the predicted model of orthogonal cutting force. Further study of mechanism will be helpful to explain the phenomena that EVC can reduce the cutting force, lower cutting temperature, and improve the surface integrity. In each overlapping EVC cycle, almost all the parameters are time-varying, of which two important factors are focused: (i) transient thickness of cut and (ii) transient shear angle. The analysis model simplified the complex process of the EVC as conventional cutting (CC) which considering two transient variables. This paper presents a non-equidistant shear zone model to predict the shear angle, tool–chip friction angle, and shear stress in CC under the same conditions of the EVC. Then, the transient thickness of cut and transient shear angle are investigated. Thus, an analytical model of the force in EVC is proposed. The model is available to predict the cutting force of the EVC accurately without any experimental parameters in CC. In addition, experimental results available in the literature are conducted for comparison, which are in well agreement with the analysis model.

Description: With pervasive applications of new information technology, a larger number of manufacturing big data is generated. This paper considers the unrelated parallel scheduling problem within the background of “big data and cloud technology for manufacturing.” Traditional unrelated parallel problem has been extensively investigated, and the main objective has been to improve production efficiency. With regard to the environmental concern, there has been limited literature. Therefore, this paper considers an unrelated parallel machine scheduling problem with the objective of minimization to the total tardiness and energy consumption where the energy consumption on each machine is also unrelated parallel. First, we give a mathematical model of this problem. Second, ten heuristic algorithms are, respectively, proposed based on the priority rules, the energy consumption, and the combinational rules due to the complexity of this problem. Finally, in order to test the performance of these ten algorithms, computational experiments are designed. In the computational experiments, lots of instances are generated, and the computational results indicate that the algorithms based on the combinational rules outperform the ones based on the priority rules and energy consumption, with respect to the unrelated parallel scheduling problem proposed in this paper.

Description: Increasing use of the nitinol (NiTi), the nickel titanium alloy is primarily due to the fact that the medical fraternity is looking more toward less invasive medical procedures. Microengineering features such as microslots, grooves, and profiles of size 0.5 mm and below are required in the NiTi alloy-based medical components, but the material offers tremendous manufacturing difficulty due to its superior mechanical properties. High-speed micro machining was viewed as a possible way to process the NiTi-based medical components without compromising the productivity and quality of the machined surface textures. A study was undertaken to characterize the high-speed micromachining process for the NiTi alloy. More specifically, the optimization of the machining process parameters with the objective of reducing the milling forces and burr formation was focused upon. The study unveiled that the understanding the tool-work interface behavior is critically important for maximizing the machining performance of the NiTi alloy. Machining behavior characterized in terms of low cutting forces and reduced burr size was achieved at 15 m/min of cutting speed when the NiTi alloy undergoes a transition from B2 phase to B19 phase.

Description: Rapid prototyping fabricates physical prototypes from three-dimensional designing models using the additive process with layers. Aims at reducing the inevitable volumetric error induced in phrase of model slicing which impacts the shape accuracy of fabricated entity, a fast determining scheme of optimal slicing orientation for least volumetric error is proposed. The work analyses the staircase effect between two consecutive layers, then infers a direct computing formula of volume deviation of a whole model. Introduces the term of area weighted normal to express the significant effect of facet area on volumetric error and converts the optimal orientation determining problem to the least absolute deviation linear regression issue. Employs prominent components analysis on weighted normal set to obtain an approximate orientation efficiently, then optimizes the solution through few searchings in neighboring orientation space. The validity and efficiency of the algorithm are evaluated on several examples. Results demonstrate that proposed algorithm consumes less than 32 % of computation load and adaptively obtains the optimal slicing orientation.

Description: Defects diagnosis and condition surveillance of production and manufacturing rotating machinery in a plant is very important for guaranteeing production efficiency and plant safety. Condition surveillance for gear and bearing defects diagnosis for all rotating machines is a serious job because they cause accidents and consequently great production losses. For gear and bearing faults, and early detection especially in the gearboxes, researchers in the conditional maintenance and vibratory analysis used different methods and techniques in signal processing, among those and in full rise, demodulation by wavelets multiresolution analysis (WMRA) and high-frequency resonance technique (HFRT), based on the Hilbert transform, which allows filtering and the demodulation at the same time. In this paper, we propose to make a precise diagnosis for gears and bearings combined faults detection and identification in a laboratory test rig which simulate a rotating machine like in the manufacturing processes using WMRA and HFRT techniques. First of all, we applied WMRA method on simulated signals of gear or bearing defects or the combination of them, then we applied it on real signals measured on a test rig of the LMS laboratory in the University of Guelma.

Description: In this paper, we propose a new fuzzy group multi-criteria decision making method and apply it to determine the critical path in a project network. The criteria used here are time (expected duration), cost, risk, and quality of the project activities that are considered critical in project management. As each criterion has its independent level of importance in the critical path selection, the weights of the project criteria are also considered in the analysis. Considering that the information in terms of various project activities and criteria weights are often incomplete and/or uncertain in real-world situations, the essential information in terms of the criteria and project activities are obtained using triangular fuzzy numbers and/or linguistic variables that are mapped to triangular fuzzy numbers, wherever appropriate. The proposed method involves fuzzy evaluation based on the fuzzy information of the possible project paths on each criterion leading to the strength and weakness index scores of the project paths. We define a measure of criticality termed as the total performance score of each project path obtained using its strength and weakness index scores. The path that has the highest measure of criticality is selected as the critical path. A numerical illustration is provided to demonstrate working of the proposed methodology. Further, a case study from manufacturing engineering industry is also presented to better justify the applicability and potentials of the proposed methodology. A comparison with closely related fuzzy multi-criteria decision methods for the critical path selection is done to analyze the performance of the proposed methodology.

Description: A chemical mechanical grinding (CMG) wheel was developed for planarization of silicon wafers, which consists of magnesium oxide (MgO) abrasives and calcium carbonate (CaCO 3 ) additives, mixed with 25 % weight percentage of magnesium chloride (MgCl 2 ) solution. It was shown that chemical reactions occurred during the grinding process, which formed a softened layer on the top of silicon substrate. The reactants could be much more easily removed by mechanical abrasion than the removal of Si phase itself. The newly developed wheel was able to produce a similar surface integrity to that obtained from chemical mechanical polishing (CMP), i.e., the CMG achieved a surface roughness of 0.5 nm in R a and a subsurface damage layer of 13 nm thick. The CMG process developed thus has great potential for back grinding or thinning of silicon wafers in order to replace CMP.

Description: The topography of fixed abrasive grinding pad has a significant effect on the process of grinding analysis. A new numerical modeling technique has been proposed to generate the grinding pad topography with spherical grains in this paper. The simulation result was given by software. Five fixed abrasive grinding pads with different grain sizes were measured by using a confocal scanning laser microscope. Comparing the results of simulation and the experiment, it can be concluded that the simulated profile of the grinding pad is corresponding well with that of the actual pad.

Description: Underwater friction stir welding is an alternative method to improve the mechanical properties of the weldments by controlling the temperature level. Owing to the limitation of temperature measurement in practice, the finite element modeling is the best tool to investigate the process. It is still not clearly known as to what extent the temperature field of joint is influenced by operational parameters in underwater friction stir welding. In this paper, finite element modeling of friction stir welding in the air and underwater were performed for Al6061-T6 alloys to control the thermal cycles. In addition to cooling effect, the influence of welding speed and rotational speed on the maximum temperature in workpiece was investigated. For this purpose, three-dimensional modeling has been done with ANSYS. The model results were then examined by experimental data, and a reasonable agreement was observed. It is found that due to water cooling effect, heat is dissipated in faster rate which leads to low peak temperature in underwater welding compared to normal welding in air, while such relationship was not seen in high welding speeds. The reason is that at high welding speeds, workpiece temperature decreases, and region of boiling water in underwater welding is reduced. This causes that heat will be dissipated from workpiece surface in faster rate. Tool rotational speed has significant effect on thermal cycles than welding speed. Moreover, in normal friction stir welding, the peak temperature diminishes with respect to welding speed in faster manner in comparison with welding in underwater.

Description: Laser drilling has swiftly become an economical and well-regulated substitute to conventional hole drilling methods such as wire EDM, punching, broaching, or other prevalent destructive processes, because of cleanliness, accurate results, precise holes, fast material removal rate, and possibility to make holes. Prompt expansion of laser technology in current years gave us facility to regulate laser input factors such as lamp current, pulse frequency, air pressure, and pulse width. The dimensional accuracy and quality of holes are very important for some specific applications of holes. Circularity of drilled hole at entry and exit, and taper are very important attributes which influence the quality of a drilled hole in laser drilling. For this reason, the experimentation based on central composite design is carried out on austenitic stainless steel for examining the effect of laser parameters, i.e., lamp current, pulse frequency, gas pressure, and pulse width, on the quality of drilled holes. A total of 31 experiments were carried out. Later, the models were predicted for output responses using response surface methodology and then tested for adequacy. It is found that the response surface methodology (RSM) predicted models are in close agreement with the experimental values. Hence, the models may be further used for optimization of process parameters using evolutionary algorithms.

Description: In this paper, a contribution to the determination of reliable cutting parameters is presented, which is minimizing the expected machining cost and maximizing the expected production rate, with taking into account the uncertainties of uncontrollable factors. The concept of failure probability of stochastic production limitations is integrated into constrained and unconstrained formulations of multi-objective optimization problems. New probabilistic version of the nondominated sorting genetic algorithm P-NSGA-II, which incorporates the Monte Carlo simulations for accurate assessment of cumulative distribution functions, was developed and applied in two numerical examples based on similar and anterior work. In the first case, it is a question of the search space that is completely ‘closed’ by high natural variability related to the multi-pass roughing operation: in this case, the failure risk of technological limitations are considered as objectives to minimize with economic objectives. The second case is related to deformed search space due to the uncertainties specific to finishing operation; therefore, the economic objectives are minimized under imposed maximum probabilities of failure. In both situations, the efficiency and robustness of optimal solutions generated by the P-NSGA-II algorithm are analysed, discussed and compared with sequence of unconstrained minimization technique (SUMT) method.

Description: Process capability indices have been widely used in industries to assess the performance of the manufacturing processes. Various different multivariate capability indices have been introduced. In this paper, a new multivariate capability vector is proposed under the assumption of multivariate normality, to assess the production capability of the processes that involve multiple product quality characteristics. Also, we investigate the relation between this index and process centering, as well as the relation between this index and the lower and upper bounds of percentage of non-conforming items manufactured. Two real manufacturing data set are used to demonstrate the effectiveness of the proposed index.

Description: In this study, classical and vortex tube cooling methods are compared in the pocket machining of AA5083-H36 alloy with uncoated cemented carbide cutting tool. The effects of cutting speed, feed rate, axial/radial depth of cut and nose radius and their two-way interactions on the surface roughness, and the optimization of surface roughness are investigated via Taguchi method. The experiments conducted based on Taguchi’s L16 orthogonal array (OA) are assessed with analysis of variance (ANOVA) and signal to noise (S/N) ratio. As a result, in both cooling methods, it is obtained that roughness correlates negatively with cutting speed and radial depth of cut and positively with feed rate and axial depth of cut. While in the cooling with vortex tube, lower average R a values are observed in the experiments with the nose radius of 0.8 mm, in the classical cooling almost no change is obtained. Lastly, optimum roughnesses for the classical and vortex tube cooling are obtained as 0.164 and 0.188 μm, respectively.

Description: The demands placed on automation of cell production processes for IT products are becoming increasingly sophisticated. Dual-arm robots are drawing particular attention as a process solution because they offer flexibility and can work in a similar manner to a human operator. In this paper, we propose an automation system for cellular phone packing processes that uses two dual-arm robots. The applied robots are designed with specifications that meet the requirements of the cellular phone packing tasks. In addition, a robotic cell production system is proposed that applies a task allocation method to perform an efficient packing job for cellular phones. In particular, each task is assigned with the intention of reducing the takt time , which is the time taken to finish a single product in the production line and to avoid collisions between the two robots. Finally, we implement some of our results in a demonstration of a packing job that involves filling five unit boxes with seven kinds of accessories.

Description: Laser forming experiments were conducted on AISI 304 stainless steel flat sheet to study the effects of process parameters and for developing an empirical model of bending angle, which could be useful to produce a class of developable surfaces from it using multiple parallel laser scans. Central composite design of experiments was used to perform the experiments, input–output relationships were established, and optimization of laser forming process under temperature gradient mechanism was carried out using a response surface methodology based on the experimental data. Laser power, scan speed, spot diameter, scan position, and number of scans were taken as input variables, and bending angle was considered as the output. The performance of the developed model was validated through a set of experimental data. The optimum process parameters for obtaining the maximum bending angle were determined, and those were verified through the real experiments. The effect of work-piece geometry on bending angle and that of multiple laser irradiations on bending rate were also investigated. Bending angle was found to be influenced by the work-piece geometry. Bending angle increased with the number of laser scans, but the bending rate decreased. Metallurgical changes at the laser irradiated zones of the laser formed samples, that is, micro-structures and micro-hardness were also studied using scanning electron microscope and Vickers’ micro-hardness tester, respectively. Microstructures were found to be refined and micro-hardness of the bent zone got improved due to the laser forming.

Description: Carbon emission has become a recent global concern for green manufacturing. Production is one of the main sources of carbon emission. As the design of a product determines over 70 % of its life cycle costs, with extensive impacts on the environment, it is important to decrease the product carbon footprint in the product design stage. As the activity data is directly related to the mass of the product, the lightweight of product is a valid approach to low-carbon footprint. However, the existing lightweight design method primarily takes structure or material into consideration without the consideration of environmental factors. The product lightweight design under the low-carbon footprint constraint is proposed in this paper, which serves low-carbon footprint as an important benchmarking for product performance. This paper then presents a general lightweight design for product low-carbon footprint through structural optimization. The design of a cold heading machine is used to demonstrate the proposed methodology.

Description: Titanium alloys are widely utilized in aerospace, automotive, biomedical and chemical engineering, etc., thanks to their excellent combination of high-specific strength, fracture, corrosion resistance characteristics, etc. However, titanium alloys are difficult-to-machine materials. Tool wear is one of the bottlenecks restricting their machining efficiency. A systematic study on the relationships among tool wear, chip morphology, and cutting vibration is inadequate. In this study, chip morphology and cutting vibration characteristics under different tool wear stages are examined using optical microscope, SEM, and vibration test system. The mechanism of tool wear in end milling titanium alloy is also investigated. Results indicate that with the progression of tool wear, the chip segment degree becomes more and more serious. The mechanism for this phenomenon is probed. Tool wear progression enlarges the cutting vibration which causes the friction force on tool/chip interfaces to increase, and this aggravates chip edge wear accordingly. On the contrary, the increase of chip segment degree induces the progression of cutting vibration and tool wear. Therefore, the aim of the present research is to investigate the sophisticated relationship. This will benefit for improving cutting efficiency and guaranteeing machining quality in end milling titanium alloy.

Description: Magnetic pulse cladding (MPC), a new technology, is proposed in this study to fabricate often utilized bi-metal tubing in engineering applications with an outer tubular component consisting of structurally strong material and an inner tubular layer of corrosion-resistant material. The MPC process includes an innovative feature that allows the outer and inner tubes to electromagnetically bond together by a sequential expansion process to form a mechanical bond between the tubes at the interface. The MPC process was experimentally arranged to produce an Al/Fe bi-metal tube with an outer carbon steel tube and an internal aluminum tube. A mechanical test was then applied to characterize bonding strength of the Al/Fe bi-metal tube. Significant process parameters including discharging voltage, radial gap, and feeding length were identified based on bonding strength influence. Overall feasibility was demonstrated for the MPC process in electromagnetic expansion pattern in the production of bi-metal tubing.

Description: Effective approach of collecting, transmitting, and handling complete product manufacturing information during machining process is necessary for realizing high efficiency manufacturing. In this paper, the architecture and implementation of closed-loop machining system (CLMS) is discussed and the method of realizing machining process control is introduced. An integrated information flow is built based on object-oriented description method to transfer complete product manufacturing information in CLMS. The functional and informational model of CLMS is established by using integration definition method. Online and real-time machining process control is implemented on an open STEP-NC controller which is collecting and analyzing information of machining process condition and inspection results during machining process. The software kernel of CNC controller implemented on a computer platform integrates with machine tool, sensors, and probe for real-time data collecting and online inspection. Finally, test parts are machined and inspected to verify the proposed machining process control method and open STEP-NC controller.

Description: An advantage of electron beam melting (EBM) additive manufacturing technology is the ability to process high-melting temperature, refractory, and/or reactive materials. This research focused on the processing of high-purity niobium precursor powder using EBM technology primarily for the freeform design and fabrication of next-generation superconducting radiofrequency (SRF) cavities. SRF accelerating cavities have been used in particle accelerators for over 35 years and are used in today’s leading applications in high-energy and nuclear physics. Procedures were developed and employed in this research to successfully fabricate high-density niobium parts (〉99 % relative density) with a thermal conductivity of ~50 W/m-K that were evaluated mechanically (140 ± 14 MPa yield strength and 225 ± 11 MPa ultimate tensile strength) and compared to wrought reactor-grade niobium (135 ± 17 MPa yield strength and 205 ± 17 MPa ultimate tensile strength). Re-engineered SRF cavities were successfully fabricated whose complex design was intended to overcome nonuniform Lorentz forces during operation. The fabrication of niobium using EBM suggests that similar procedures from this research can be applied to successfully fabricate other refractory materials such as niobium alloys as well as highly conductive materials such as copper.

Description: This paper outlines an Internet of Things (IoT)-based collaborative framework which provides a foundation for cyber physical interactions and collaborations for advanced manufacturing domains. A general framework for collaborative manufacturing is proposed followed by a discussion of such an IoT-based framework for the domain of micro devices assembly. The design of this collaborative framework is discussed in the context of cloud computing as well as the emerging Next Internet which is the focus of recent initiatives in the USA, EU, and other countries. The data/information exchange between the various software and physical components is modeled using the engineering Enterprise Modeling Language (eEML), which provides a structured foundation for designing and developing this IoT-based collaborative framework. The key cyber physical components and modules are described followed by a discussion of the implementation of this framework.

Description: The longevity of hard alloy indexable cutting inserts used to cut metal parts is significantly related to their proper geometric design. Such a relationship is outstanding in an intermittent cutting scenario. One solution is to use a strengthened cutting insert with a negative chamfered edge. This method has proven to be effective in avoiding chipping and brittle fractures. However, it does have other effects, like a larger cutting force and a higher cutting heat. In the present research, a set of intermittent cutting experiments were conducted through combinations of two grades of hard alloy indexable inserts and multiple geometric parameters of cutting edges. A three-dimensional dynamometer and a high-speed camera were used to monitor and collect data on the impact and cutting force during the process. A study over the strengthening mechanism of the negative chamfer to the cutting insert was conducted using statistical analysis, which revealed the influence of those geometric parameters of cutting edges on the insert’s lifetime. Further, it gave a quantified relationship between the negative chamfer parameter and the feed. This conclusion serves as both data and technical support for the design enhancement of hard alloy indexable inserts.

Description: Orthogonal turn-milling is a novel machining process with the advantages of better surface quality, improved process stability, and higher machining efficiency compared to conventional turning. Chip formation in the turn-milling process plays a significant role in cutting force, tool life, and chatter stability. This paper presents an experimental study on the 3D chip morphology properties during orthogonal turn-milling of Al6061-T6. The effects of cutting parameters on turn-milling chip length and thickness were examined and discussed. The multi-surfaces (including free surface, back surface, and cross-section surface) of turn-milling chip were characterized to understand the mechanism of chip morphology formation. The mixed continuous-and-segmented chips in a single cut and its slipping properties were observed, and the shear band of serrated chip and its ductile fracture property were analyzed. The microhardness variation of turn-milling chip was investigated under different machining parameters. The shear band as well as the profile surface of chip shows increased hardness. This experimental study presents the insight in evaluating the cutting mechanism of turn-milling process and provides guidance for choosing optimum cutting conditions.

Description: High-accuracy contouring error estimation is the premise of effective contouring error control. However, two key factors make it complex to estimate contouring error for multi-axis machines with rotary axes: the nonlinear kinematics and the synchronization requirement of the tool tip position and tool orientation. This paper proposes a generalized online estimation algorithm of multi-axis contouring errors for CNC machine tools with rotary axes. The nearest reference tool pose to the actual one is searched at first, and then the corresponding contouring error components on each axis are estimated by using linear ratio estimation, where the tool tip position and tool orientation are naturally synchronized to one same pose on the desired trajectory. The advantage of the proposed contouring error estimation algorithm is that only the interpolated reference poses and drive commands are needed in the calculation, which increases the generality of the algorithm to different trajectory types and machine topologies. On the other hand, the calculation load is reduced when compared with existing iterative multi-axis contouring error estimation approaches. Simulation results on both five- and four-axis machines show that the proposed contouring error estimation algorithm can estimate axis components of contouring errors with high accuracy. Experiment results on an in-house developed five-axis experiment platform verify the effectiveness of the proposed algorithm.

Description: Heat flux changes in grind-hardening process resulting in uneven distribution of grind-hardening layer depth, making it more difficult to produce a hardened layer in the grinding cutting-in and cutting-out area, leading to uneven distribution of the hardening layer depth in grinding stable region. This paper firstly studied the grinding force. Secondly, grinding distortion is analyzed by thermal–mechanical coupling numerical analysis. The grinding distortion makes the actual grinding depth deeper. According to the distortion, the actual cutting depth can be concluded. The actual cutting depth affects the variation of grinding force. Thirdly, the relationship among grinding force, grinding distortion, and the distribution of the hardening layer depth is presented in the paper. At last, variable grinding cutting depth to control grinding force is put forward to improve the uniformity of the distribution of the hardening layer and is verified by experiment.

Description: Fused deposition modeling (FDM) is one of the most popular additive manufacturing technologies for fabricating prototypes with complex geometry and different materials. However, current commercial FDM machines have the limitations in process reliability and product quality. In order to overcome these limitations and increase the levels of machine intelligence and automation, machine conditions need to be monitored more closely as in closed-loop control systems. In this study, a new method for in situ monitoring of FDM machine conditions is proposed, where acoustic emission (AE) technique is applied. The proposed method allows for the identification of both normal and abnormal states of the machine conditions. The time-domain features of AE hits are used as the indicators. Support vector machines with the radial basis function kernel are applied for state identification. Experimental results show that this new method can potentially serve as a non-intrusive diagnostic and prognostic tool for FDM machine maintenance and process control.

Description: In practical applications of multivariate sliding window (SW) control charts, a considerable amount of difficulty lies in selecting parameters related to the window size and to the disposal of past observations. Although widely used for pattern recognition problems, to the best of the authors’ knowledge, there have been no comparative analyses of the efficiencies of multivariate SW schemes and more traditional and easy-to-apply control charts, such as Hotelling’s T 2 and the multivariate exponentially weighted moving average (MEWMA) control charts. The present work applies a transformed statistic called confidence control chart (CCC), which standardizes all the control charts in the 0–01 interval to improve visualization, and comparisons are made in terms of the average run length (ARL). Therefore, the purpose of this paper is to present a simulation study to compare the inertial effect of estimating the actual mean vector through the SW and the MEWMA schemes. Three types of SW schemes were tested, including uniform, linear, and exponential weights. In addition to providing equivalences between the smoothing parameter of the MEWMA method and the window sizes for the bivariate case, the results show that multivariate SW schemes suffer from the inertial effect more than MEWMA charts. In this sense, the user is encouraged to apply both control charts to avoid detection delay.

Description: This article presents the work on wear-resistance coatings (WRC), formed on the working surfaces of HSS tools, in order to increase their efficiency. The wear-resistant complex includes nitride layer, which increases the plastic strength of the HSS tool cutting wedge and cutting tool wear resistance, as well as a three-layer nano-structured composite coating that increases tool life. The equipment for the processes of ion nitriding in the gas plasma and the formation of nano-structured multi-layer composite coatings in the filtered metal-gas plasma cathode vacuum arc discharge has been developed. Particular attention was paid to the regularities in the formation of the nitride layer and optimization of its parameters and structure, together with the study of the properties and structure of functional coating layers, depending on the parameters of the deposition process. The parameters of the combined cathodic vacuum arc processing (CCVAP), provides minimum intensity of tool wear during the cutting tests. Sample of coated tools were used to conduct a certification of the developed WRC. This allowed determining the optimal parameters WRC that provided the maximum increase in tool life for a variety of cutting conditions. The outcomes are compared with uncoated HSS tool and standard commercial coatings.

Description: Joining of multimaterials is a major issue for several industrial applications where the combination of individual material properties increases component performance. The objective of this experimental study is to assess the laser weldability of NiTi to Ti-6Al-4V. Dissimilar welds were performed on 1-mm-thick plates with a high-power fiber laser with different heat inputs to control the cooling rate. Fracture was always observed in the weld metal in a solidification cracking phenomena. Scanning electron microscopy with EDS was performed to analyze the fracture surfaces. Solidification cracking was observed in the fusion zone associated to Ti 2 Ni formation in two distinct fracture morphologies: brittle transgranular cracking in the Ti 2 Ni regions and dimple intergranular failure along the solidification dendrites. Thus, autogeneous welding of these two materials is difficult due to intermetallics formation and filler materials or interlayers are needed to prevent the formation of brittle intermetallics.

Description: Reconfigurable manufacturing machines are designed to allow manufacturers to readily adapt to changing circumstances. This adds a new dimension to the process-planning problem, as the machine structure is not constant. A comprehensive set of reconfiguration management assessment tools and methods must be introduced to assist in developing the most appropriate process change strategies for a given set of circumstances based on the machine structures, control capabilities, and the skill levels and availability of shop personnel. Therefore, the goal of this research is to develop methods to assess the machine configuration/reconfiguration compatibility characteristics for alternative process strategies. The methods must be adaptable to suit a variety of environments and present results that are readily understood by all actors. Systematic, matrix-based techniques for assessing product and process complexity are introduced as well as a methodology to assess the suitability for CNC machine tool configurations with respect to a process plan, which considers the candidate machines’ physical and functional characteristics to determine its suitability. The resulting candidate machines are subsequently assessed to consider the process transition complexity issues utilizing an extension of a manufacturing complexity analysis framework used to evaluate product and process complexity. Case studies are presented to illustrate the merits of the proposed methodology.

Description: The present article offers a modified method of friction stir process combined with ultrasonic vibrations in order to reinforce polyamide 6 (PA 6) using multi-walled carbon nanotubes (MWCNT). For this purpose, ultrasonic-assisted friction stir process and simple friction stir process were performed to distribute the MWCNT particles among the PA 6. Field emission type of scanning electron microscopy, X-ray diffraction, Vickers’ micro-hardness, and visual inspection were used to evaluate and compare properties of the fabricated nano-composites. According to the findings, increase of traverse speed leads to increase of the stir intensified by the energy imposed by ultrasonic vibrations during ultrasonic-assisted friction stir process (UAFSP). On the other hand, energy imposed by ultrasonic vibrations accelerates nano-composite fabrication process without affecting dispersion, homogeneity, and hardness. In other words, nano-composite could be fabricated by higher traverse speed without reduction of stirring during UAFSP.

Description: Diamond-coated wire (DCW) sawing of Si solar ingots generates swarf which is analyzed using micro-Raman spectroscopy. Two types of Si swarf are found. Particulate swarf is crystalline and shows residual compressive stress. Fibrillar swarf is amorphous and shows residual tensile stress. The origin of particulate, crystalline swarf is attributed to brittle machining, while the origin of fibrillar, amorphous swarf is attributed to ductile machining. Finite element modeling suggests that brittle machining resulting in particulate, crystalline swarf generation is initiated by sharp diamond microparticles. On the other hand, ductile machining resulting in fibrillar, amorphous swarf generation is caused by blunt diamond microparticles. Over the course of sawing, the ratio of crystalline/amorphous phase in swarf decreases, quantifying the average loss in sharpness of diamond microparticles. Thus, micro-Raman spectroscopy can be an effective analytical tool for quantifying and monitoring DCW sawing processes for Si solar ingots.

Description: In this paper, a feedforward proportional-integral (PI) controller is developed to effectively control and tune the laser cladding melt pool geometry in real time. Width setpoint is included in the computer numerically controlled (CNC) programming, making possible its instantaneous change in relation to the position and time, as opposed to conventional controllers that do not have real-time information about these variables. The new concept of variable setpoint at different positions applied to laser cladding represents a great improvement in its use for changeable geometry applications such as blade fabrication. Several experiments are performed to characterize the behaviour of the system, revealing some key factors from monitoring system and image processing crucial for the controller. Laser power is selected as the input control variable, and the clad width is chosen as the output. The width of the melt pool is obtained based on measurements of CMOS camera images and an in-house image processing software algorithm. Closed-loop parameters are identified from the experimental data and Matlab simulations. The architecture of the controller consists on a conventional PI feedback loop and a feedforward module that shows low overshoot and fast response times. Instantaneous connections between laser, CNC, and PC systems allow for knowing the relationship among the exact position and real and setpoint melt pool values. The performance of the controller is verified in the fabrication of cladded parts with variable widths and in real time.

Description: Carbon fiber reinforced plastic (CFRP) offers excellent mechanical properties, such as high strength, light weight, which makes it widely used in aerospace, transportation, machineries, and industrial applications. However, because of its anisotropic mechanical properties, high hardness, high strength, and poor thermal conductivity, the traditional processing methods are gradually unable to meet the processing needs. Except delamination, glitches, and tearing during processing, there are also other defects, like severe tool wear, larger cutting force, and higher cutting temperature, which make the tool life shortened. The machinability of CFRP materials using conventional machining (CM) techniques has seen a limited improvement over the years. Rotary ultrasonic machining (RUM) is an advanced machining process, which has shown to have specific advantages especially in the machining of CFRP. Many experimental investigations on cutting force in RUM of CFRP have been reported. However, in the literature, there are no reports on the development of a cutting force model for flat surface rotary ultrasonic machining, i.e., rotary ultrasonic face grinding (RUFG). In order to reveal the mechanism of grinding force reduction in RUFG of CFRP, based on material properties of CFRP, the brittle fracture theory approach was adopted and a cutting force model was developed for CFRP in RUFG process. The experiments were carried out and found the affect of the input variables for the cutting force in RUFG. The results were analyzed and discussed. The trends of predicted effects of input variables on cutting force agree well with the trends determined experimentally. Compared with the experimental results, the developed cutting force model was regarded as reasonable.

Description: Hot stamping technology of high strength steel creates new possibilities for vehicle manufacturers in promoting safety and fuel efficiency. The proportion of hot stamping parts in vehicles increases each year, and there are already hundreds of different types of hot stamping lines throughout the world. However, few studies regarding modeling of hot stamping process procedure have been reported, nor have there been studies regarding cooperative scheduling of manufacturing units (including heating units, transferring units, and forming units), or the relationship between productivity and energy consumption. With the shortening of the vehicle life cycle, auto parts manufacturing must be flexible for multiple types and small batches to meet the challenges of the market. In this paper, a model of the hot stamping process procedure based on finite state machine is established, then the model is adapted for the procedure control of a hot stamping line, consisting of multi-chamber furnaces, linear conveying robots, and a mechanical servo press. The cooperative scheduling of various manufacturing units, especially the method which matches multiple heating chambers with a single forming die, is focused on. Finally, a hot stamping line with multi-chamber furnaces is designed and implemented, and the analysis of its production sequence, energy consumption, and delivery cycles is performed. The results show that with the new modeling method of hot stamping process based on finite state machine, the new developed hot stamping line is capable of multiple production objectives and flexible configuration in accordance with production and delivery periods. This active configuration aids in extending equipment life and reduce energy consumption. The modeling method expands production models for hot stamping, from the mass production model to multiple types and small batches production model.

Description: In wire and arc additive manufacture (WAAM), the twist of wire during a robot’s movement can result in the sudden changes of the wire-feeding position and thus cause deposition defects and dimensional errors. In the worst case, it may cause wire jamming and damage of the wire-feeding system. Therefore, online monitoring and correction of the wire deflection are very important for WAAM. In this paper, a vision-based measuring method is proposed for detecting the deviations of the wire-feeding position of a plasma welding-based WAAM process. It uses adaptive threshold and Hough transform to extract the wire edges, judges and merges the coincident lines, and applies Radon transform to measure the wire deflection. Software to automatically detect the wire deviation was developed based on the proposed method. The method and the software were verified with experiments.

Description: Chatter is considered as one of the most important causes of instability in the precision grinding process. Suffering from the influence of nonlinearity and changed machining condition, regenerative chatter signal is nonlinear and non-stationary in nature, which makes the linear representations and stationary assumed methods not appropriate. Wavelet bicoherence is considered as an effective method for these nonlinear signals analysis. However, current wavelet bicoherence is often estimated by integrating over the finite time interval. This procedure may result to the loss of the time information; hence, it is not appropriate for chatter signal that cannot be assumed to be stationary. In this paper, an instantaneous nonlinearity indicator-based method is proposed for regenerative chatter identification in grinding by using the servomotor current signal. Firstly, the nonlinearity of servomotor current affected by regenerative chatter is discussed. After that, a non-stationary wavelet bicoherence is proposed for the quadratic nonlinear coupling detection of these nonlinear and non-stationary signals. On this basis, an instantaneous nonlinearity indicator is further established for regenerative chatter identification. The effectiveness of the proposed method is verified by simulations and experiments, and the results show that, compared with the commonly used wavelet bicoherence and continuous wavelet transform, this method can not only describe the non-stationary chatter signal in time-frequency domain but also extract the true nonlinear coupling component resulted from regenerative chatter.