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The work described in this paper concerns a novel method for directly forming curved profiles/sections from billets in one extrusion operation using two opposing punches. Its mechanics are based on internal differential material flow, and it has been given the acronym, differential velocity sideways extrusion (DVSE). A tool set enabling sideways extrusion to be performed using opposing punches moving with different velocities was used for a series of experiments in which punch velocity ratio and extrusion ratio were process parameters. Plasticine was used as a model work-piece material and a series of compression tests were undertaken, to determine its constitutive properties and gain an estimate of work-piece die friction for use in process simulation. Curvature of extrudate can be controlled and varied using a difference between the velocities of the two punches, defined by velocity ratio. Greater curvature is achieved with lower velocity ratio. Curvature is also dependent on extrusion ratio, an increase in which increases curvature, although curvature is less sensitive to it than to velocity ratio. The extent of work-piece flow velocity gradient across the die exit orifice, which causes curvature, has been identified. Severe plastic deformation of the extrudate occurs in a way similar to channel angular extrusion (CAE), thus a greatly promoted effective strain level is achieved, though it is not always uniform across a section. The inner bending region of an extrudate experiences maximum localised effective strain, which decreases with decrease in curvature. To the authors' knowledge this is the first publication in which extrudate curvature is deliberately induced using opposing punches with differential velocities. Although only fixed velocity ratio values have been used in the work described in this paper the ability to change during operation exists and the process has the potential for the production of a profile with different curvature along its length. [ABSTRACT FROM AUTHOR]

Microstructure features directly reflect mechanical responses during material deformation and can influence the surface integrity of machined components, which is of great interest to both academic communities and industries. This paper summarizes the state of the art in modeling approaches for the effect of the microstructures and its evolution during metal-cutting processes. The aim of this paper is to analyze the advantages and drawbacks of current methods to improve modeling work and direct future orientations. First, dominant numerical modeling approaches for metal-cutting processes are reviewed. The finite element method (FEM) and mesh-free methods widely applied in professional research are discussed. Following this, approaches to modeling the effect of microstructures and their evolution are reviewed for two major categories—homogeneous field distribution and heterogeneous characteristics. Both the advantages and disadvantages of these two categories are analyzed and discussed in detail. Experimental techniques based on advanced characterization approaches to the validation of pertinent models are also discussed. Finally, a brief summary is presented and an outlook for future work is delineated. [Display omitted] • Numerical modeling approaches with the consideration of microstructure features towards metal cutting are reviewed. • Modeling through treating microstructures as homogeneous characteristics and pertinent validation techniques are reviewed. • Modeling of heterogeneous microstructure evolution in metal-cutting and pertinent characterization techniques are reviewed. • Future orientations of modeling the effect of the microstructure and its evolution in metal-cutting are recommended. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a novel microscale laser dynamic flexible forming (μLDFF) technique on plastic forming of thin metal sheets. This process utilizes flexible rubber material as a soft punch, under the pressure generated by laser-induced shock wave, to act on the thin metal sheet. This novel technique has many new features and the forming mechanism is complex, as well as it takes place in the scale of nanoseconds, which is too short to monitor the deformation behaviors during the process. In order to reduce the experiment times and cost, this paper firstly investigates the feasibility of the process numerically using finite element software ANSYS/LSDYNA, and some key process parameters, such as hardness and thickness of soft punch, thickness of thin metal sheet, aspect ratio of rigid die, as well as laser pulse energy are detailed studied to obtain reasonable parameters. Then a series of experiments based on these reasonable parameters are conducted, and good experimental results are obtained, which verifies the feasibility of the use of simulation to guide the experiment. The results of both numerical simulations and experiments show that the use of combination of soft punch and thin metal sheet can increase the deformation depth in comparison to focusing the beam directly onto thin metal sheet, which is due to the impedance mismatch at the soft punch–thin metal sheet interface. [Copyright &y& Elsevier]

Abstract: This paper addresses the development of a new methodology predicting residual stresses induced in finish turning of a AISI304L stainless steel. A hybrid approach combining experimental results and a numerical model is applied. The model simulates the residual stresses generation by applying equivalent thermo-mechanical loadings onto the machined surface without modeling the chip removal process, which enables rapid calculation. The shape and the intensity of equivalent thermo-mechanical loadings are identified through experimental measurements. Friction tests enable to model the thermal and mechanical loadings along the tool–workmaterial interface. Orthogonal cutting tests provide thermal and mechanical loadings below the primary and third shear zone. This model has already been presented in several papers, but only in a 2D configuration. The objective of this paper is to transfer this hybrid approach into a 3D configuration, which is closer to a concrete longitudinal turning operation. Based on this new model, the paper aims at investigating the interactions between each revolution. It is shown that around five revolutions are necessary to reach a steady state. Finally numerical results are compared with experimental measurements obtained by X-Ray diffraction. It is shown that residual stresses cannot be considered as homogeneous over the surface due to tool''s feed. Additionally, the X-Ray beam is much too large to be able to quantify this heterogeneity. Based on average numerical values coherent with average values obtained by X-Ray diffraction, it is shown that the numerical model provides consistent results compared to experimental measurements for a large range of cutting speed and feed. [Copyright &y& Elsevier]

Abstract: When designing CNC machine tools it is important to consider the dynamics of the control, the electrical components and the mechanical structure of the machine simultaneously. This paper describes the structure and implementation of a concept for real-time simulation of such machine tools using a water jet cutting machine as an application. The concept includes a real control system, simulation models of the dynamics of the machine and a virtual reality model for visualisation. The real-time capability of the concept, including the simulation of electrical and rather detailed mechanical component models is proofed. The validation process indicates good agreement between simulation and measurement, but suggests further studies on servo motor, connection and flexibility modelling. However, already from the initial simulation results presented in this paper it can be concluded that the influence of structural flexibility on manufacturing accuracy is of importance at desired feeding rates and accelerations. The fully automated implementation developed in this work is a promising base for dealing with this trade-off between productivity and accuracy of the manufacturing process through multidisciplinary optimisation. [Copyright &y& Elsevier]

Singularities in five-axis machining are a series of deadly positions, which may cause unstable axis movements and deteriorate the performance of machine tools. This paper presents an optimization strategy to locally deform the tool path so that singularities of five-axis machine tools can be avoided. To achieve this purpose, a new concept of “forbidden circle”, which is the projection of the three dimensional “singular cone” associated with tool orientations in a two dimensional space named P-plane, is established for the first time to transform the complicated three dimensional problem into a two dimensional problem. Based on this idea, the projected points in P-plane are interpolated as B-spline first, and then, the B-spline control points are locally optimized by taking the “forbidden circle” as the geometrical constraint to keep the B-spline from crossing it. Especially, in the optimization procedure, the constraints are linearized with the changes of B-spline control points to change the whole optimization problem as a typical positive definite quadratic programming problem, which can achieve one and only global optimal solution. By doing so, singularity is avoided, and at the same time, the machining errors caused by tool path deformation can be minimized. Simulation and experimental results verify the effectiveness of the singularity avoidance method. [ABSTRACT FROM AUTHOR]

Tool tip frequency response function (FRF) is essential for chatter stability diagram in machining. But new modal tests are required for different tool-holder-spindle assemblies. To avoid these tests, receptance coupling substructure analysis (RCSA) method has been developed. Previous research proved that the full receptance matrix, which contains rotational and moment contributes, influences the RCSA accuracy. By improving the accuracy and efficiency in acquiring the full receptance matrix, this paper presents a new RCSA methodology to predict the tool tip dynamics when a new tool is selected. To identify the contact dynamics between the tool and tool holder, one required receptance matrix is experimentally measured with a reference tool attached on the machine. Comparing to the classical RCSA technique, an enhanced approach is proposed to better estimate the receptance matrix. Only one impact positon is required in the experiment. The enhanced approach introduces two compensation strategies to process the measuring data from impact test. Each compensation strategy can be chosen to improve the estimation accuracy. The measured receptances, together with the finite element models of the reference tool and the new tool, are used to predict the unknown tool tip FRF. Both numerical simulation and practical experiment are conducted to validate the proposed methodology. The results show that the proposed method is preferred when multiple modes should be considered. [ABSTRACT FROM AUTHOR]

This paper proposes a streamlined method to model, analyze and assess the overall performance of small mobile machines that can move along large parts to perform the required machining operations, conventionally called portable machines. The method is based on virtualization techniques and combines a process-force mechanistic model and a reduced machine stiffness model synthesized from virtual and experimental reduced models of subsystems. The model is used to assess and improve the performance of portable machines by examining the time-domain response of the tool center point in representative operations, rather than limiting the study to the frequency domain. A practical application to a particular portable machine is presented and used to conduct the presentation of the work. With the results of the analysis, the accuracy of the use of the portable machines is studied. The procedure also proves to be a useful tool to optimize the machine design to fit particular applications. The method has been experimentally evaluated in a conventional three axis milling machine to ensure the accuracy of the simulations. [ABSTRACT FROM AUTHOR]

This paper proposes an efficient actual inverse kinematics method to compensate the geometric errors of five-axis machine tools. The analytical expressions of corrected numerical control (NC) code are derived according to the invertibility, associative law of multiplication, and block calculation of homogenous transformation matrix (HTM). No additional analysis and models are needed for the compensated expressions, appropriate conversion with the geometric error model based on HTM is sufficient. It is simple, convenient and universal for geometric error compensation. The corrected NC code can be obtained through algebraic operation, without time-consuming iteration, differential, or pseudo-inverse algorithm. Then compensation accuracy and efficiency of the method are simulated. And the results indicate higher efficiency compared to existing method. At last, the method is verified by cutting experiment on a five-axis machine tool. Both simulation and experiment results can validate the feasibility of the method. The proposed method significantly improves the computation efficiency and is considered more suitable for real-time compensation. [ABSTRACT FROM AUTHOR]

Five-axis position independent geometric errors (PIGEs), which are caused by imperfect assembly of machine tools, need to be identified and compensated in order to improve the accuracy of machined parts. In traditional PIGEs identification model based on differential motion matrices (DMM), PIGEs elements are defined in the local frames attached to the previous axis, which is inconvenient to do redundance analysis. In order to fully but un-redundantly identify five-axis PIGEs, this paper proposes a new PIGEs identification model based on DMM in the global coordinate frame. The transfer matrix which realizes the transformation of PIGEs between global and local definitions is derived at first. Then the Jacobian function of the tool center motion errors related to PIGEs defined in the global frame is calculated and adopted for PIGEs identification with the least-square algorithm. For the proposed PIGEs identification model in the global frame, the minimum set of PIGEs can be easily found to make sure full but un-redundant identification, by properly setting up the machine tool coordinate frame using the method of ISO 230-1:2012. The proposed new Jacobian function and PIGEs identification model in the global frame are verified through simulation and experiments with ball-bar tests. [ABSTRACT FROM AUTHOR]

Backlash is one of the most commonly encountered nonlinear phenomena in feed drives, which degrades the contouring accuracy of machine tools. The full-closed loop could suppress the adverse effects of backlash significantly. However, a transient backlash error (TBE) remains. Unfortunately, the mechanism of the TBE is completely different from that of the conventional backlash error. The purpose of this paper is to reveal the mechanism of the TBE. First, for the demonstration of the TBE, a general model is derived from an industrial feed drive with the closed loop control. Subsequently, the model is simplified further. Based on the simplified model, the mechanism is described and clarified in detail, and furthermore, the analytical formulations of TBEs are derived for the cases of straight line and circle, respectively. Finally, several simulations and experiments are given to validate the proposed models and formulations. [ABSTRACT FROM AUTHOR]

Abstract: Micro end milling is an important process in the manufacture of micro and meso scale products and has an advantage of creating more complex geometry in a wider variety of materials in comparison with other micro-machining methods. In this paper, a new methodology for predicting the cutting coefficients considering the edge radius and material strengthening effects is presented. Further a mechanistic model is developed to predict the cutting forces in micro end milling operation taking into account overlapping tooth engagements. The mechanistic model, derived from basics considering material property and principles of metal cutting, is valid for a wider range of cutting parameters. The model is validated with the results from micro slot end-milling of mild steel carried out on the basis of full factorial design. On comparing the amplitudes of cutting forces, it is seen that mechanistic model predicts the transverse force with an average absolute error of 12.29%, while a higher prediction error of 19.49% is obtained for feed force. Additionally the mechanistic model is able to predict the variations in the cutting forces with rotation of the cutter and average absolute deviations of 13% and 11% are obtained for feed and transverse forces, respectively. [Copyright &y& Elsevier]

Abstract: The helical-wedge rolling (HWR) process is a new metal forming technique for producing spherical parts of various dimensions. In this paper, the overall details of the HWR process are described and the important process parameters that control the HWR process are systematically discussed. A new experimental method, developed under laboratory conditions, showed that the HWR process can produce spherical steel parts (balls) with high manufacturing quality. Numerical simulations of the HWR process were carried out using a commercially available FEM software (Simufact) to show the stress, strain, and temperature distributions in the rolled balls. In addition, the variation of forces and rolling moments during the process are analyzed. Based on the experimental and numerical investigations, the HWR technique has been found to be a viable process for enhancing the quality and productivity of formed spherical products. [Copyright &y& Elsevier]

Abstract: Cross-coupled control (CCC) is a well-known approach for directly reducing contour errors on contouring systems instead of the indirect approach of reducing axial following errors. An improvement of this approach, the variable-gain CCC, extends its applicability from just the linear contour to any contour defined by a continuously differentiable function. In this paper, the basic concept underlying CCC is used to develop a generalized CCC (GCCC) approach which can be applied for any free-form contour, including those defined only by a series of (x,y) coordinates similar to the reference inputs to CNC machines. Both computer simulation and actual experimental implementation of GCCC on a small two-axis CNC machine using four contours showed that it can effectively reduce the contour errors resulting from mismatched machine dynamics. For the linear, circular and parabolic contours that CCC can also be applied to, GCCC achieved the same level of contour error reduction. In addition experiments showed that GCCC also achieved similar levels of contour error reductions for free-form contours and for corner tracking. Without the need for a knowledge of the functions of the contours, GCCC is thus most suitable for application to CNC machines in which the contours that are to be generated are defined by a series of reference input axial positions. [Copyright &y& Elsevier]

Abstract: The model-based Taylor series expansion error compensation (TSEEC) method has been shown to be capable of eliminating contour errors in biaxial CNC machines. However, it has been developed for only linear and circular contours. In this paper, an extension of TSEEC, a generalized TSEEC or GTSEEC, is proposed which is capable of compensating for the contour errors of arbitrary two-dimensional contours. A new real-time algorithm is used to estimate the contour error so that GTSEEC can be applied even in cases where the function of the contour is unknown. Simulation results using linear, circular and parabolic contours are presented which show that, with perfect knowledge of the axial dynamics, GTSEEC can perfectly eliminate the contour errors for any contour, even when there is significant mismatch in the axes'' dynamics. Experiments on a small two-axis computer-controlled machine indicate the effectiveness and better performance of GTSEEC in reducing contour errors for free-form contour following tasks when compared with two other leading approaches, the zero phase error tracking control (ZPETC) and cross-coupled control (CCC). [Copyright &y& Elsevier]

Abstract: Micro scale laser bulge forming is a high strain rate micro-forming technique, which employs the shock wave pressure induced by a laser pulse to deform thin metals to 3D configurations. The process holds promise for fast setup, well-controlled, high efficiency and precision of fabrication of complex miniaturized devices. In this paper, micro scale laser bulge forming of pure copper was investigated using both numerical and experimental methods. A finite element model was proposed to simulate the dynamic deformation of the shocked material, and the simulation results were validated by experiments. With the verified model, the deformation mechanism of the transient forming process was characterized through the evolution of equivalent plastic strain rate and the distributions of strains and residual stresses. In addition, the effects of laser energy, die diameter and sample thickness on the forming behavior of copper foils were studied. The experimental and numerical simulation results show that with an increase of sample thickness, the deformation depth decreases, while it becomes larger as the enhancement of laser energy. The shock forming process is not very sensitive to the diameter of the die, indicating that it is feasible for micro products in a wide dimension range. [ABSTRACT FROM AUTHOR]

Abstract: The material properties for the analytical and numerical simulation in sheet metal processes, especially in tube hydroforming process, are generally obtained from the uniaxial tensile test of raw sheet material. However, the validation of the formability and reliability of the numerical simulation for the tube hydroforming process arises from the fact that the material characteristics of tubes are different from those of the raw sheet materials. In order to determine the most suitable material property of the tubular material for the evaluation of forming limit on the THF process, the uniaxial tensile test for the specimens of the raw sheet metal and the roll-formed tube and the free bulge test for the roll-formed tubular material are carried out in this paper. The forming limit curves are also derived using plastic instability based on three kinds of necking criteria, which are Hill’s local necking criterion for sheet and Swift’s diffuse necking criteria for sheet and tube, to describe and explain the forming limits for the roll-formed tubular material in the THF process. In order to acquire the informative data on the forming limit curves in the THF process, the loading condition of the free bulge test is controlled. The proper band from nearly necking initiation to nearly bursting initiation has been defined for the roll-formed tubular material in the THF process. It can be concluded that the flow stress of the tubular material should be determined from the actual free bulge test to find the practically valuable forming limit curve for the THF process. [Copyright &y& Elsevier]

Abstract: Rake angle and its distribution on the cutting edge of a twist drill are of vital importance to its performance. This paper presents a practical method to determine the cutting edge and rake angles. Firstly, 3D coordinates of the points on the cutting edge are inspected by using 2D measurement apparatus. Secondly, the flute profile is deduced from the data measured, and the rake angles are evaluated by numerical computation. Conventionally, rake angle calculation is based on a series of plane definitions and laborious work in plane projection is inevitable. To facilitate the process, a vector based procedure is presented. As an example, cutting edge of a standard drill is measured by using tool microscope and image-based instrument. In each case, the normal rake angle distribution is determined. Numerical results exhibit that average error and mean square error of the latter deviated from the former are 0.95o and 0.33o, respectively. It verifies the validity of the proposed procedure and the measurement device. [Copyright &y& Elsevier]

Abstract: A novel process technology for micro punching of thin sheet metals is presented in this paper. The laser induced shock waves act as the micro punch. The forming speed can be controlled by adjusting the laser energy. Micro holes of 250μm in diameter were successfully punched on sheet metal of 10μm in thickness by single pulse, and good edge quality was obtained. The micro die-opening is produced by electrical discharge machining (EDM) using the copper electrode of φ=220μm. In the experiment, a sacrificial coating is used to generate high-pressure plasma under a laser pulse, so no signs of melting, burning, or ablation were observed on the workpiece. The novel process of micro scale laser high speed punching is also numerically studied. In addition, this method can be used to fabricate noncircular micro holes on thin sheet metals with noncircular micro die-openings. With further development, laser high speed punching may become an important micro punching technology, which is characterized by non-contact, low cost, and high efficiency. [Copyright &y& Elsevier]

Abstract: Axis orientation stability of aerostatic bearing spindles has great influence on machining precision of ultra-precision fly cutting machines used for processing ultra-precision optical components of large diameter. Mid-spatial frequency errors (amplitude<0.1μm, wavelength about 100nm) always existed on the machined surfaces along feeding direction. Generally, the waviness errors on processed surfaces will impact the performance of workpiece used as optical components greatly, and the tilting motions of spindles were believed to be the main source which produced the waviness errors. In this paper, to study the tilting motions of spindles, the Euler dynamic equations of angular displacements of spindles were proposed, and analytic solutions of the equations were also presented. At the same time, the 3D surface profile simulations of workpieces based on analytic solutions of Euler equations were achieved. The simulation results have been verified by lots of experiments on an ultra-precision fly cutting machine. At last, the inertia tensor criterion which can decrease the waviness errors of machining surface was represented, and it can be applied to instruct the structure design of aerostatic bearing spindles. [Copyright &y& Elsevier]

Abstract: Ultraprecision machines with small footprints or micro-machines are highly desirable for micro-manufacturing high-precision micro-mechanical components. However, the development of the machines is still at the nascent stage by working on an individual machine basis and hence lacks generic scientific approach and design guidelines. Using computer models to predict the dynamic performance of ultraprecision machine tools can help manufacturers substantially reduce the lead time and cost of developing new machines. Furthermore, the machine dynamic performance depends not only upon the mechanical structure and components but also the control system and electronic drives. This paper proposed a holistic integrated dynamic design and modelling approach, which supports analysis and optimization of the overall machine dynamic performance at the early design stage. Based on the proposed approach the modelling and simulation process on a novel 5-axis bench-top ultraprecision micro-milling machine tool – UltraMill – is presented. The modelling and simulation cover the dynamics of the machine structure, moving components, control system and the machining process, and are used to predict the overall machine performance of two typical configurations. Preliminary machining trials have been carried out and provided the evidence of the approach being helpful to assure the machine performing right at the first setup. [Copyright &y& Elsevier]

Abstract: Prediction of cutting forces and machined surface error in peripheral milling of curved geometries is non-trivial due to varying workpiece curvature along tool path. The complexity in this case, arises due to continuously changing process geometry as workpiece curvature varies along tool path. In the presence of cutter runout, the situation is further complicated owing to changing radii of cutting points. The present work attempts to model process geometry in machining of curved geometries and in the presence of cutter runout. A mathematical model computing process geometry parameters which include cutter/workpiece engagements and instantaneous uncut chip thickness in the presence of cutter runout is presented. The developed model is more realistic as it accounts for interaction of cutting tooth trajectory with that of preceding teeth trajectories in computing process geometry. Computer simulation studies carried for this purpose has shown that it is essential to account for teeth trajectory interactions for accurate prediction of process geometry parameters. This aspect is further confirmed with machining experiments, which were conducted to validate this aspect. From the outcomes of present work, it is clearly seen that the computation of process geometry during machining of curved geometries and in presence of cutter runout is not straightforward and requires a systematic approach as presented in this paper. [Copyright &y& Elsevier]

Abstract: This paper investigates chatter vibration occurring in drills for deep hole machining. A model is developed that considers process damping occurring due to the interference between the drilling flank surface and the workpiece surface. Furthermore, the gyroscopic effect due to the rotation of the tool is included. Borders of stability, which indicate critical radial widths of cut (RWOC) at each spindle speed, are obtained analytically from the eigenvalues of a frequency domain equation. Results at this stage show good agreement with the experimental data. In addition, a numerical method is used to simulate the tool path at different RWOC and spindle speeds. Numerical simulation agreed with analytical results. The hole form produced by the tool tip is investigated at different speeds and RWOC with respect to borders of stability. These investigations show that spindle speed selection is an important manner in industrial practice. That is, even below borders of stability, where chatter does not occur, spindle speed selection affects roundness, concentricity, and surface roughness of the hole. [Copyright &y& Elsevier]

Abstract: Among the scientific problems in drilling, determining thrust forces for any drill geometry and any workmaterial remains an issue. This question is especially critical in the context of the self-vibratory drilling (SVD) technology, since thrust force governs the trajectory of cutting lips. In order to predict the dynamical behaviour of the self-vibratory drilling head (SVDH), a numerical simulator has been developed in the laboratory. In order to predict the relevant behaviour of the SVD operations, a good accuracy of the thrust force model is highly necessary. The aim of the paper is to propose an experimental methodology to identify a thrust force model for one pair “drill–workmaterial” depending on the uncut chip thickness. This methodology proposes to divide cutting edges into several parts in order to define the local contribution of this part to the macroscopic thrust force. Local models are identified during the penetration of the drill. From a limited number of experiments with various feeds, it becomes possible to identify all the coefficients of an accurate thrust force model. [Copyright &y& Elsevier]

Abstract: This paper presents generalized process simulation and optimization strategies to predict and improve the performance of three-axis milling operations. Cutter-part engagement conditions are extracted from a solid modeling system, which can handle free form part surfaces found in dies and molds. The cutting force distribution along the engaged cutting edge-part surface is evaluated based on the laws of mechanics of milling. By integrating the distributed force along the cutting edge, total forces, torque and power are either predicted analytically using closed-form solutions, or numerically if the cutting tool shape is discontinuous. Simulation results are then used in a constraint-based optimization scheme to maximize the material removal rate (MRR) by calculating acceptable feedrate levels. The proposed virtual milling system is demonstrated experimentally in milling a stamping die with free form surfaces. [Copyright &y& Elsevier]

Abstract: Ultra-precision freeform surfaces are complex surfaces that possess non-rotational symmetry. Currently, there is a lack of definitive international standards and techniques for the characterization of form accuracy and surface quality of ultra-precision freeform surfaces. This paper presents an integrated form characterization method (IFCM) to measure the form accuracy of ultra-precision freeform surfaces. The IFCM is developed based on the five-point pre-fixture, dual cubic B-spline and an iterative precision adjustment algorithm with coordinate transfer. To verify the capability of the proposed method, a series of computer simulation and measurement experiments were undertaken. The results indicate that the IFCM can realize the precise alignment of measured and normal surfaces with accuracy in nanometer range which provides adequate base for good form characterization of ultra-precision freeform surfaces with form accuracy down to below sub-micrometer range. [Copyright &y& Elsevier]

Abstract: Ultrasonic vibration cutting as a cutting process has been widely used in the precision machining of difficult-to-cut materials due to an enhanced cutting stability and increased productivity. The authors'' previous researches have shown that chatter vibration prediction is made possible by the suggested cutting model. This paper is an attempt to determine cutting parameters based on regenerative chatter prediction in order to facilitate the machining objectives of high accuracy, high efficiency and low cost in ultrasonic vibration cutting. The machinability of SCM440 steel, called typical hardened steel, is investigated theoretically and experimentally. The cutting model is developed by introducing an experimental cutting database of SCM440 steel. The simulation and experimental results show that the workpiece material parameter has a direct influence on the occurrence of regenerative chatter. In order to achieve the chatter-suppressing dynamics in hard ultrasonic vibration cutting, a stability diagram is predicted based on the simulated work displacement for tool geometry changing. The stability diagram indicates that the regions of the chatter-suppressing dynamics expand with increasing tool rake angle and decreasing tool clearance angle. It is also found from the predictive results that regenerative chatter can be suppressed by a change of tool geometry. The determined tool geometry with the aid of the computer simulation is demonstrated through actual data of ultrasonic vibration cutting. By the use of the designed tool geometry, a good experimental result is achieved. [Copyright &y& Elsevier]

Abstract: This paper is in two parts describing the kinematic simulation of the grinding process. The first part is concerned with the generation of the grinding wheel surface. A numerical procedure for effectively generating the grinding wheel topography is suggested. The procedure is based on the transformation of a random field. The sufficient condition for the transformation is discussed, and two transformations satisfying the condition are introduced. Numerical examples are used to illustrate the viability of the approach. It will be shown that the generated and measured grinding wheel topography share the same probabilistic characteristics. [Copyright &y& Elsevier]

Abstract: The telescoping magnetic double ball bar (DBB) is widely used to assess the motion and link errors of machine tools through circular tests. Despite a careful setup, some slight eccentricity of the balls relative to the circular trajectory often remains. Removing the eccentricity from the DBB results is essential due to its effects on the estimated trajectory. However, if the centering is not performed with great care, a fictitious ovalization effect may appear in the processed data. The source of the fictitious ovalization is discussed in this paper and a method is proposed to quantify the eccentricity and adequately process the data so that the fictitious ovalization is avoided. The results obtained by applying the proposed method both in simulation and in practice demonstrate its effectiveness. [Copyright &y& Elsevier]

A surface in generation machining is obtained as an envelope of a series of cutter surfaces formed during kinematic motion between workblank and cutter. Extensive work has been carried out to obtain the generated surface using coordinate transformation and differential geometry approach. In this paper, CAD approach is used to simulate generation machining process. For this purpose, the cutter and workblank are taken as solid models and simulation is performed using Boolean operation to remove unwanted material in an incremental manner, maintaining the kinematic relationship. A computer program in C is developed to generate relevant script file, which is then executed in a solid modeling package to simulate generation machining. This approach is demonstrated by taking simple cases of helical groove machining with disc-type and pencil-type cutters and a complex case of worm gear machining. Solution to reverse problem of arriving at cutter geometry from given work surface is also obtained by this approach. Use of the CAD approach in identifying the contact lines has also been reported, taking helical gear pair as an example. [Copyright &y& Elsevier]

Sheet hydroforming has many virtues and has gained increasing interest in industries recently. In this paper, hydromechanical deep drawing (HDD) with uniform pressure onto the blank is proposed and investigated in detail both primarily in experiments and simulation. Final cups with drawing ratios of 2.46 and 3.11 were, respectively, obtained using Al–Mg–Si alloy (Al6016-T4) and soft aluminum (Al1050-H0) that have the strong anisotropic properties. The influence of process parameters on the sheet deformation was studied and the typical failure types including fracture and wrinkling were discussed. Finally, FEM was used to analyze the forming process, and the results from the FEM simulations were in good agreement with those from the experiments. [Copyright &y& Elsevier]

Laser shock punching is a recently developed technique, which is very efficient for punching microholes in thin metal sheets. However, processing large areas with laser shock punching is difficult because the processing area is limited by the size of the laser spot. Moreover, as the duration of the laser-induced shock pressure is considerably less than that of the explosive used, the thickness of the punchable metal sheet is in the order of a few tenths of the punch diameter. In this paper, we report an efficient approach that enables micropunching over a large area of a metal sheet in a single step. This micropunching method uses an underwater shock wave generated by the explosion of a plastic explosive charge. This approach is successfully used to punch circular holes over a large area of a 0.1-mm thick A1100 sheet, forming multiple holes with a diameter of 300 μm each. The pressure profiles of the underwater shock waves measured using piezo film gauges are used to analyze the micropunching process using ANSYS Autodyn software. The punching process is numerically simulated, and it is observed that the simulation and experimental results are in good agreement. The proposed approach can be applied to high-strength materials and thick sheets that are difficult to process using laser-induced shock waves. • Micropunching method using explosives for punching a wide range of metal sheets. • The new method can be applied to high-strength materials and thick sheets. • The punching area can be increased by changing the shape of the explosive. • The shock pressure and duration can be used to control punching conditions. • The shape of the hole edge depends on the shock pressure. [ABSTRACT FROM AUTHOR]