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Femtosecond laser processing is a non-thermal process with less heat effect on a target material and is applied to dielectric and difficult-to-machine materials, such as titanium alloy and diamond. Femtosecond laser processing has been used for 3-dimensional shape generation in recent years, and increasing accuracy and productivity are required for such generation by femtosecond lasers. However, a 2.5-dimensional computer-aided manufacturing (CAM) system, which is mainly used in femtosecond laser processing, does not satisfy the requirement for complicated 3-dimensional shape generation. Therefore, there is a need for the development of a 3-dimensional CAM system for high-precision and productive 3-dimensional processing. Furthermore, for the 3-dimensional CAM system, quantitative identification of a 3-dimensional removal shape through ablation is necessary. This study proposes the development of a simulation method to accurately predict the 3-dimensional removal shape through femtosecond laser processing, including the piecewise approximation of the ablation rate and absorptance correction. At the same time, a similar 3-dimensional shape as that found through the experimental results was obtained during the simulation by considering the mechanical errors of the laser processing machine in the simulation model. Furthermore, an on-machine measurement system was developed to efficiently identify the ablation parameters.

One advantage of a femtosecond laser is that it enables the processing of materials that are otherwise difficult to process via conventional methods such as cutting, grinding, electric discharge machining, etc. However, it is difficult to predict a three dimensional shape processed by the laser. To achieve required three-dimensional shapes using femtosecond lasers with high accuracy and efficiency, it is essential to develop a computer-aided manufacturing (CAM) system that generates processing data (NC data). In this paper, a simulation method is proposed for femtosecond laser processing, which is the basis for the development of a CAM system. A binderless nano-polycrystalline diamond is used as the workpiece material to test the proposed method. Based on a comparison with the experimental results, it is confirmed that the processing shape could be simulated at a high accuracy for fixed-point irradiation as well as scanning irradiation.

Ablation processing using a femtosecond laser has the advantage of processing materials that are impossible to machine by conventional methods. However, it is difficult to predict the three-dimensional removal shape owing to a femtosecond laser irradiation and the current processing method, repeating through trial and error, is inefficient and expensive. For this reason, for processing materials to desired shapes using a femtosecond laser, development of a simulation system and a CAM (Computer-Aided Manufacturing) system are indispensable. In this paper, a simulation method for processing materials using a femtosecond laser is proposed and conducted to nano-polycrystalline diamond (NPD). It is confirmed that the proposed method can precisely simulate the femtosecond laser processing for three-dimensional shape generation. Therefore, the proposed method enables to predict the removal shape identified as the virtual tool shape for calculating a tool path on a CAM system. In addition, an automation process method including an on-machine real-time measurement system of the proposed method is described.

Repairing, remanufacturing, and refurbishing high value metal components are crucial to move towards a more sustainable economy. Nowadays, repairing operations on high value parts, such as dies, are generally performed using time-consuming manual approaches that rely on the operator’s expertise. The research idea of this paper is to develop a retrofit kit to provide additive capabilities to an existing milling machine, allowing automatic repairing of components thanks to a fast switch between additive and machining operations without a relevant economic investment such the acquisition of a brand-new machine: the final cost of the solution is lower than 10% with respect to the mean cost of a 5-axis milling machine. The additive technology used in this work is Wire Arc Additive Manufacturing (WAAM) that is characterized by a higher deposition rate and a simpler and cost-effective equipment with respect to other techniques (e.g., laser cladding). The design of the system is illustrated in the paper together with the analysis of the results achieved repairing a test case: a die casting mold made of AISI H13 tool steel.

Proton exchange membrane fuel cells have benefits over heat engines and batteries as an energy system for transportation, stationary power, and portable electronics. Before fuel cells can replace current energy systems, their manufacturing cost to performance ratio must be improved. The bipolar plate is a fuel cell component that contributes significantly to fuel cell manufacturing costs and is a key driver of performance. Metallic bipolar plates, with characteristic flow dimensions below the standard 1 mm, were fabricated using direct machining. Hydrogen/air fuel cells constructed of these plates were tested to ensure performance gains, using interdigitated flow operation and automobile-representative channel lengths. Finite Element Modelling (FEM) was used to investigate the manufacture of bipolar plates using low cost sheet metal stamping. Multiple bipolar plate alloys were compared based on their stampability, and die design parameters needed to stamp submillimeter channels were determined. Springback analysis was performed, and the effect of springback on fuel cell stack stresses was investigated.

With the ever increasing demands for higher and higher accuracy on modern CNC equipment, the manufacturing processes for machining and assembling the structural components are an increasingly important factor in establishing a geometrically correct machine tool. Specifically, flatness, perpendicularity, parallelism, and straightness of interfacing surfaces determine whether the machine tool's basic accuracy. Exhibiting less geometric error allows other errors such as thermal growth, ballscrew pitch error, and control error to be isolated and more easily corrected. The geometric errors are predominately a factor of the machine tool machining and assembly process. Multiple orientations during fixturing in both assembly and machining result in significant distortions to the final assembled product. These are a result of cutting forces, fixturing deformations, gravity deformations, and bolt force deformation. By analyzing each process in detail using virtual simulation techniques, a high-fidelity model of the corresponding error at each manufacturing step can be achieved that is not physically measurable due to constraints of measurement equipment. Using simulated data as offset data in the machining process as well as in the jig and fixture design ensures a geometrically accurate final product.

Using EDM technology in conjunction with traditional MEMS fabrication techniques offers great advantages in the creation of freeform features silicon wafers. The ability to mass produce features, however, is often limited by high electrode wear rates due to poor EDMing stability based on silicon's material properties. By investigating the use of novel diamond-based electrode materials, high productivity and low wear rates can be achieved simultaneously. First, the feasibility of applying diamond-based electrodes is presented through the rough EDMing of 200 hemispherical features. Second a two-step EDM roughing and finishing process is applied in order to achieve high quality and axisymmetric hemispherical features. Using only an EDM roughing process, 200 hemispherical features were successfully fabricated in 80 minutes with virtually zero electrode end wear. The two-step EDM roughing and finishing process resulted in the fabrication of 15 highly axisymmetric hemispherical features with only 15 microns of total electrode end wear. A case study is presented in the fabrication of hemispherical shell structures, where the EDMed hemispherical features are used as a mold for MEMS device fabrication.

For productive manufacturing of an accurate small-scale wine-glass gyroscope, a hybrid fabrication process consisting of either electric discharge machining, chemical etching, or micro-mechanical milling have been proposed. A comparison of silicon cavity fabrication processes has been conducted in terms of productivity, quality and geometrical accuracy, aiming at the use of the cavity as a mold for creating a thin wall diamond hemisphere, which is the main component of a wine-glass gyroscope. The results have shown that the EDM process, combined with chemical etching, can yield the highest productivity but with limited shape accuracy. The use of mechanical micro-milling, while less productive than EDM and etching, produces a superior quality and geometric accuracy.

To improve efficiency and cost performance of cast iron machine tool component fabrication, an alternative process must be developed in order to replace the grinding process, which often causes a bottleneck in production. As an alternative manufacturing approach, this research applies cubic boron nitride (CBN) hard milling operations to eliminate the grinding process in order to improve the overall manufacturing process. A variety of hardened cast iron materials with Al and Mg additives and CBN tool types were prepared and tested based on a design of experimentation (DOE) to observe their effect on surface quality and tool life. Al and Mg were added to raw cast iron to achieve generation of oxide layers at the cutting edge during milling to protect the tool from wear. By executing the DOE, the optimal cutting conditions for achieving the best surface quality were introduced. Also, additional machinability tests were conducted with the optimal conditions in order to evaluate tool wear characteristics and surface quality of the machined workpieces. Based on the observation of the used tool by electron probe micro-analyzer (EPMA), a protective oxide layer of additives was observed at the cutting edge. Hardened cast iron with Al and Mg additives is found to show preferable wear and surface quality characteristics.

To increase fabrication efficiency for poly-crystalline diamond (PCD) microtools, wire EDM technology was applied and optimized by using a design of experimentation. For roughing, the productivity must be maximized while for finishing, the surface roughness must be minimized to achieve the best overall quality. Using three different grades of PCD, experimental results show a significant increase in productivity with no significant decrease in microtool quality, which was confirmed by hexagonal end-mill fabrication using both non-optimized and optimized conditions.

A milling operation is inherently an intermittent material removal process where cutter engagement and disengagement is repeated until the end of the material removal process. During the process, the cutter receives multiple impacts and mechanical and thermal vibrations which eventually damage the cutting edge. The optimum rigidity and damping of the spindle motor for the least tool damage highly depends on the cutter and workpiece material properties and the cutting application. This paper introduces the concept of flexible rotational rigidity control using a high performance Permanent Magnet Synchronous Motor (PMSM) which is used as a direct spindle drive. With the PMSM spindle, the spindle rotational characteristics can be adjusted for optimizing the cutting process in order to prevent tools from unwanted premature damage. Simulation models of the spindle motor drive system are presented, which show that a very stiff spindle can be realized by fully utilizing the potential capability of the PMSM and a spindle with the same dynamic properties of a conventionally used induction motor can be realized with a single PMSM spindle. The system prototype and feasibility studies are also presented in this paper. The experimental results show that the PMSM spindle characteristics behave differently depending on the controller setting, and the spindle motor drive system rotational characteristics greatly affect the cutting process, which confirms the importance of the flexible motor control concept.

A study has been performed to understand the mechanism for generating a high quality surface on fine grain tungsten carbide dies and molds for miniature products by PCD micro end-milling operations. In order to find the best milling conditions, systematic experimental procedures have been introduced. The procedures include the preparation of various diameter single edge end-mills made of PCD (poly-crystalline diamond), sequential variation of machining conditions, and the precise setting of various instruments to observe the dynamic behavior during the machining process. By following the proposed procedures, optimum conditions for achieving the best machined surface quality have successfully been obtained.

A 3D model of the maximum rotating envelope of a milling cutter with tool holder is required for Computer Aided Manufacturing (CAM) process design and machining simulation. The user may define the 3D model of the whole tool assembly in the tool library of CAM software. However, it is not convenient and reliable. Considering these problems, a new method based on single view 3D reconstruction algorithm has been proposed in previous research work, which is able to quickly reconstruct the 3D model of a cutter with tool holder while they are installed onto the spindle. As the extension of this work, this paper focuses on the recent progresses in order to improve the automation, accuracy, efficiency and reliability of tool modeling system. First, an improved flexible on-machine camera calibration procedure is proposed. The accurate motion of machine tool axis is used to calibrate the camera on machine tool instead of a physical calibration board. The whole procedure of calibration can be conducted automatically by running NC code. Therefore, the automation of vision system can be guaranteed. Second, the contour extraction module is improved by using a method of silhouette image composition. This method is applied to solve the problem of translucent and fuzzy cutter profile induced by motion blur. Third, the new algorithm for contour partitioning and classification are proposed, which is more reliable and robust. The reliability and accuracy of the vision system can be guaranteed. Finally, the vision system with an 8 mm lens and 1 mm extensions has been tested on different type of machine tool with smaller cutters. The average measurement accuracy is about 35 microns verified by comparison with a commercial tool setting system.

This paper describes a characterization method of disturbance force in a linear drive system supported by high-precision rolling guideways. Disturbance force is divided into the friction component and other disturbance force. Experimental characterization method to analyze effect of global position, effect of micro-position and effect of table velocity is suggested. With stop-dwell-go and reversal motions, characterization experiment and analysis are conducted on a positioning system consists of a linear motor and rolling guideways. Firstly, global disturbance force depends on global position and stick and slip friction components are characterized. Secondly, stick friction force is separated from stick and slip friction force in the micro-region. Thirdly, influence of the velocity is analyzed. Finally, a modified single bristle model, which describes friction characteristics in the micro-regime, is shown to simulate the measured disturbance force.

In order to develop highly stable machining processes in heavy duty milling applications, a study on the development of a high torque–high power spindle system has been conducted. The study includes the design of a new permanent magnet synchronous motor, drive system and spindle system with the designed motor, prototype of the spindle system with the designed motor and experimental evaluation of the entire system by conducting heavy duty milling of a titanium alloy. The results of the experiments show that the spindle has a high rotational rigidity under heavy duty intermittent cutting processes.

Collision detection by machining simulation requires the 3D models of rotating cutters. However, the 3D models of a cutter and holder are not always available. In this paper, a new method is proposed to design an automatic vision-based 3D modeling system, which is able to quickly reconstruct the 3D model of a cutter and holder when they are installed onto the spindle. Only a single camera is mounted on the machine tool to capture the image of the rotating cutter and holder. By viewing the rotating cutter and holder as an object of surface of revolution, the contour of the imaged cutter and holder can be used to reconstruct the 3D model as a stack of circular cross-sections. Then the complete generating function of the cutter and holder can be recovered from the cross-sections. Finally, the 3D model of the cutter is built by rotating the generating function around the spindle axis. The effectiveness and accuracy of the proposed method are verified by experiments on-machine using 12 kinds of cutters and holders, which can satisfy the requirement of collision detection.

Parametric interpolation has been widely used in CNC machining because of its advantages over the traditional linear or circular interpolation. Many researchers focused on this field and have made great progress in the specific one, NURBS curve interpolation. These works greatly improved the CNC machining with constant feedrate, confined chord error and limited acceleration/deceleration. However, during CNC machining process, mechanical shocks to machine tool caused by the undesired acceleration/deceleration profile will dramatically deteriorate the surface accuracy and quality of the machined parts. This is, in most occasions, very harmful to machine tools. In this paper, an accurate adaptive NURBS curve interpolator is proposed with consideration of acceleration-deceleration control. The proposed design effectively reduces the machining shocks by constraining the machine tool jerk dynamically. Meanwhile, the constant feedrate is maintained during most time of machining process, and thus high accuracy is achieved while the feedrate profile is greatly smoothed. In order to deal with the sudden change of the acceleration/deceleration around the corner with large curvature, a real-time flexible acceleration/deceleration control scheme is introduced to adjust the feedrate correspondingly. Case study has been taken to verify the feasibility and advantages of the proposed design.

In order to meet the increasing demand for high-quality miniature parts made of a wide variety of materials, the electronics, biomedical and optical industries are moving towards micro/nano-machining. Currently, mechanical micromachining can only be performed under very low feed rates and small depth of cut, which makes it very difficult to reach reasonable productivity. To cope with the low-productivity problem for micro/nano-machining of high-precision molds or miniature parts, a highly accurate and productive machining center has been designed and developed in this paper. The developed machine tool is equipped with counter balance axes, and each axis is driven at its center of gravity to achieve high acceleration/deceleration without causing any vibration. This paper describes the theoretical and practical background of the design of the machine tool and its control and measurement system. Then, experiments are carried out to evaluate the machining performance of this designed machine tool.

In order to create a higher torque spindle system for productive milling operations, rotational speed stability against the torque disturbance has been studied with respect to the spindle mechanical design parameters, actuator types and spindle control algorithms. The study showed a remarkable difference in the spindle rotational speed stability against torque disturbance between a spindle system equipped with an induction servo motor and a permanent magnet synchronous servo motor. The results of this study have been obtained by theoretical analysis, numerical simulation and physical experiments, and the experimental study showed that the hybrid actuation spindle achieves longer tool life.

Time-optimal trajectory planning for mechanical systems has been widely studied thus far because of its effectiveness to reduce the time required for many industrial tasks. However, in general, because the time-optimal trajectory is generated based on ideal dynamics of controlled systems, it may be difficult to implement the obtained trajectory to actual systems with vibration mode that is neglected in the trajectory generation. In other words, high-speed motion based on the time-optimal trajectory may cause the vibration of the real system. Hence, in this paper, we propose to employ the contouring control developed by the authors, which enables to reduce controller gain magnitudes while contouring performance are maintained. First, this paper presents a method of generating the time-optimal trajectory for machine tool feed drives. The presented method considers viscous friction that is significant in high-speed motion of mechanical systems and has an advantage that the number of variables required for the optimization is reduced compared to the conventional method. Next, the contouring controller is applied to implement the time-optimal trajectory to an actual machine tool system. The effectiveness of the proposed method and the contouring controller is demonstrated by comparative experiments with the conventional method.

Micro/nano milling tools are usually made of ultra hard materials. Wire EDM (electrical discharge machining) may be the best choice to fabricate these tools conveniently and efficiently. For micro/nano milling tools with complicated three-dimensional (3D) geometries, manually programming method is not applicable. The CAM (computer-aided manufacturing) systems existing in the market don't take the special WEDM (Wire EDM) processes for micro/nano milling tools into consideration. In order to generate the NC programs automatically for the multi-axis WEDM machine to fabricate micro/nano milling tools, a computer assistant system, also called the CAM system, is developed in this paper. The CAM system takes the special WEDM processes into consideration for the fabrication of micro/nano milling tools. First, based on the interfaces and the databases of the CAM system, geometries of micro/nano milling tools, machining conditions for different portions of the tools, WEDM machine tool specifications and controller ...

A compact multi-purpose spindle for multi-tasking machine tools has been developed such that it can provide high power and torque for lower speed ranges while it rotates at high speeds for light duty machining. The innovative design based on the dual direct drive concept has been adopted such that the size of the spindle can stay the same as a conventional spindle of its class. For optimizing the design process, a method based on the complete virtual approach using 3D solid models has been studied and developed. Machining performance has been verified through a physical prototype.

Micro/nano milling applications are needed due to the miniaturization tendency of components used in medical devices and aerospace equipments. Accordingly, micro end mills are needed. However, there are no special purpose machine tools designed for the fabrication of such tools made of ultra hard materials and with complicated three-dimensional geometries. In this paper, a six-axis wire electrical discharge machine (WEDM) designed for the fabrication of micro end mills is developed. Direct drive linear motors and rotary motors are used for linear and rotary axes respectively to realize direct drive instead of ball screws or gearboxes. A special cooling system for all motors makes the thermal effect minimum on the mechanical structures. After the introduction of the developed WEDM, its kinematics model is built. The error analysis for the key axis directly supporting the wire is introduced and the corresponding results are used to guide the mechanical design of the six-axis WEDM and to compensate for position errors during machining. Based on these techniques, high machining accuracy is achieved. Finally, the fabrications of a cutter with complicated geometry and a cutter made of ultra hard material are successfully demonstrated on the developed machine tool.

There have been many researches on the contouring control for machine tool feed drive systems. To the best of authors' knowledge, its effectiveness has been shown only by comparative experiments with industrial non-contouring (independent axial) controllers that are previously set up, or non-contouring controllers along with the contour error compensator such as the cross-coupling controller. Because the control performance largely depends on controller gains, such comparison remains some ambiguities to show the effectiveness of contouring control. In other words, a similar control performance may be achieved if the non-contouring controller gains are appropriately assigned. This paper discusses the effectiveness of contouring controller in both analytical and experimental manners. A basic formulation of a coordinate transformation based contouring controller and its effectiveness are shown. Because there exists an inherent contour error in the coordinate transformation approach, a method to reduce the inherent contour error is presented to enhance the effectiveness of contouring controller. The contouring controller is concluded to be effective, in that it provides a comparative performance to the non-contouring controller with less control input variance. This property seems to be useful for not damaging machine tool systems, and for saving required control energy.

A non-uniform, rational B-spline (NURBS) interpolator has great advantages for free-form surface machining compared to the conventional linear/circular interpolator. However, the existing NURBS interpolators can only handle the NURBS trajectory given in a customized NURBS G code. Also, it is limited to three-axis applications. In this paper, a NURBS pre-interpolator with three function options is proposed for a computer numerical control (CNC) system so that the NURBS interpolator can be thoroughly applied for five-axis machining. The first function is called the NURBS converter function, which is used to convert a series of linear/circular segments exactly into a NURBS curve. The second function is the NURBS smoother function, by which, a series of linear segments are fitted to a NURBS curve. The third option provides two kinds of NURBS G codes definition, by which, the NURBS trajectory with five axes can be represented directly. Upon using the three options of the NURBS pre-interpolator, a unified NURBS curve can be obtained for further interpolation. Two actual machining cases are conducted to evaluate the feasibility of the proposed pre-interpolator.

The paper describes a three dimensional vision-based modeling system, which can efficiently and accurately construct solid models of a machining environment including the workpiece setup with jigs and fixtures on the machine table. The unique methods of the object recognition with various key technologies have been developed based on the simultaneous real and virtual stereo image processing. Since the constructed model accurately matches with the real setup, real time NC program verifications can be performed for 100% collision-free machining simulation. The prototyped system has been successfully verified by implementation on several real machining systems.

This paper introduces the intelligent sequence design system of multi-stage cold extrusion. It discusses the method to build the part feature modeling and to realize feasibility checking, process planning and evaluation, process parameter optimization and sequence optimal selection, mainly focuses on the feature modeling and system implementation strategy. According to the given input data, the system can generate the forgeable geometry and the basic sequence design and evaluates the sequences, depending on the initial billet size and material or the evaluation knowledge in the knowledge base. An example proves the proposed theory and method.

Finish milling with a ball-end mill is a key process in manufacturing high-precision and complex workpieces such as dies and moulds. Due to the complexity of the milling process, it is difficult to observe experimentally the surface microcharacteristics such as the surface topography and roughness of machined workpieces real-time during machining. This necessitates simulation of the process. In this area, the existing related simulation researches focus mainly on scallop heights; few have presented a whole picture of the microcharacteristics of milled surfaces. A comprehensive simulation system has been developed for predicting the surface topographic features and roughness formed in the milling process, and the effect of machining parameters was studied. This paper focuses on the modelling method and theory adopted in the simulation system. The method to improve the calculation accuracy is discussed in detail. The approach to incorporate the effects of the cutting tool run-out and wear is also presented. Experiments are also carried out to verify the simulation results.

Recent strong demand for production of ultra-precision components drives the need for 5-axis super-precision machines. A design study of such a 5-axis super-precision machine, which is capable of nanometer-level precision cutting, has been conducted by searching innovative solutions to the three major problems: friction, thermal deformation, and positioning accuracy. The final design implemented the following: stiff aerostatic guideways for near frictionless motion while structural rigidity was maintained, thermally stable structures made of alumina ceramics, and smooth control of linear motor based actuation system by employing high resolution and highly responsive linear encoders and linear power amplifiers. The designed machine has been built to verify the targeted performance. Various shapes that require nanometer- accuracy have been created using the machine. The results have consistently indicated stable nanometer-level accuracy. Targeted design performance has been successfully demonstrated.

Finish milling with a ball end mill is a key process in manufacturing high-precision and complex workpieces, such as dies and molds. Because of the complexity of the milling process, it is difficult to evaluate the microcharacteristics of machined surfaces real time, which necessitates the simulation of the process. In this area, the existing related simulation researches mainly focus on scallop height evaluation, but few have presented a whole picture of the microcharacteristics of milled surfaces. This paper develops a comprehensive simulation system based on a Z-map model for predicting surface topographic features and roughness formed in the finish milling process and studies the effect of machining parameters. The adoption of the discretization concept of the tool’s cutting motion makes it possible to dynamically track the cutting tool-workpiece interaction with the tool movement and to describe the cutting edges-workpiece discrete cutting interaction more realistically and, therefore, the microcharacteristics of the machined surfaces more accurately. Also, the effects of the cutting tool run-out and wear are incorporated into the developed model through modifying the tool center motion and the cutting-edge shape, respectively. As a fundamental study, the tool-swept envelope has been simulated. The developed simulation system is applied to thoroughly study the surface features formed by the 2.5-axis finish milling process. The application for general three-axis machining is discussed. Additionally, this paper studies the effect of the tool inclination, which is the most common characteristic in 3+2- or five-axis milling processes, on the machined surface features. Experiments are carried out to study the milling process and to verify the simulation results. The difference between the simulated and experimental results is discussed, and the reason behind the difference is explored.

For high performance machining, it is essential to minimize the vibration of a machine tool, which is incurred due to the instantaneous acceleration/deceleration. To minimize this vibration, it is fundamentally ideal to apply the driving force at the most shock-insensitive position of the moving structure: the center of gravity. Aiming at developing unparalleled high-performance machine tool systems, the effectiveness of the Drive at the Center of Gravity (DCG) principle on vibration reduction has been studied thoroughly by analytical and experimental approaches. Based on the results obtained, a new design of the high-performance machine tools has been discussed with a special focus on the installation of DCG mechanism without sacrificing any advantages already obtained in the recent basic design rules. The paper also describes the comparative study between a machine tool based on the DCG principle and the one with a conventional driving configuration. The results obtained have shown a distinctive performance difference in machining stability.

The paper presents a surface-based approach for geometric feature recognition for the purpose of automating the process planning of freeform surface machining. The proposed approach consists of the following four steps for recognition of the geometric features: conversion and preprocessing of the surface geometry data, subdivision of NURBS surface, reconstruction of surface orientation areas, and recognition of geometric features. The proposed scheme assumes that the input geometry data form is based on an IGES CAD model and the surface model can be represented in the form of trimmed NURBS surfaces. The connectivity relations of the product surfaces are analyzed and each surface is subdivided into orientation regions based on the surface normal vector over a certain point density grid, and then all the connected regions with the same orientation type are grouped into surface orientation areas. After that, the geometric feature will be recognized through the analysis of area connectivity and relationship. The paper describes the developed algorithms on surface orientation region subdivision, surface orientation area reconstruction, and geometric feature recognition. The verified feasibility study of the developed method is also presented.

Based on Z-map method, in this paper the development of a geometric model for the linear motor equipped EDM die-sinking process is described. Firstly discussed are the advantages and benefits of the introduction of the linear motor into EDM die-sinker. The current model has been employed to calculate the minimum gap distance for sparks to occur and to analyze the possibility of spark generation between the workpiece and electrode surfaces. Also calculated is the crater formed by a single spark. The final machined surface topography is predicted. The influence of peak current and discharge duration on the average surface roughness is simulated. The experiment has been conducted to study the effects of machining conditions as well as to verify the effectiveness of the developed geometric model.

To meet the accuracy requirements, coordinate measuring machines (CMMs) are generally operated with low acceleration-deceleration profiles to minimize residual vibration. This results in low efficiency and may cause a bottleneck in the production line. In the authors' previous study, two control configurations utilizing the input-shaping technique and feedforward controller were proposed to reduce residual vibrations in single-axis and multiple-axis types of motion. This paper focuses on the evaluation of the proposed methods by implementation on a physical CMM. The dynamics of the machine were identified via experiment. The controller design techniques were presented to give the appreciation of the design steps. The evaluations were done by experiment. It was found that the proposed controller implementation methods reduce the residual vibrations by 68 percent for single-axis motion and 88 percent for multiple-axis motion. The methods allow the use of a higher acceleration profile, which results in higher productivity.

This paper presents an in-process inspection-oriented autonomously generative CMM (Coordinate Measuring Machine) part programming methodology with a simplified part programming process to decrease the time and skill for CMM part programming. The proposed method differs from the CAD-based CMM programming approach. Using this new method, machining features in a complex part can be efficiently inspected after any stage of machining operations or after machining these features. The concept of the proposed CMM part programming approach and its implementation are described in this paper. The results obtained from the feasibility study show the developed CMM part programming system can autonomously generate an inspection plan for a work-in-progress part model generated from NC programs to realize the in-process measurement.

This paper deals with the enhancement of tracking accuracy of multi-axis feed drive systems. Feed drive systems with perpendicularly configured two axes are utilized in most of machine tool systems. Although orthogonal errors to desired trajectories are important in machining, tracking errors with respect to each feed drive axis are only considered in most of conventional control systems. In order to improve the machining accuracy, controllers that can directly reduce the contour errors are required especially in high speed machining. A new design of contour tracking controller based on a complete coordinate transformation is proposed in this paper. A variable structure controller is also designed for achieving the performance robustness with respect to plant modeling errors. The effectiveness of the proposed methods is demonstrated by simulation results.

In order to increase the accurate finishing productivity of pearlitic cast iron, face milling by CBN (Cubic Boron Nitride) cutting tools was studied. The main focus of the study is the machinability investigation of pearlitic cast iron with CBN cutting tools by studying the relationships among machining conditions such as feed rate, cutting speed as well as CBN cutting tool type, tool wear, workpiece surface quality, cutting forces, and cutting temperature. In addition, an emphasis is put on the effect of Al additive in pearlitic cast iron on its machinability and tool wear characteristics. High-speed milling experiments with CBN cutting tools were conducted on a vertical machining center under different machining conditions. The results obtained provide a useful understanding of milling performance by CBN cutting tools.

Computer-aided process planning (CAPP) is becoming increasingly crucial to today's computer-integrated manufacturing (CIM) and rapid production. To automate the process planning, feature-based operation planning systems have been suggested and studied extensively. In such a system, given a machining feature, the operator requires practical machining operation data for the feature. In this research, a system of reverse engineering is proposed to extract machining features and their associated machining operation data. Furthermore, a machining know-how database containing the extracted data is created for future operation planning. Since successful NC programs contain the machining know-how of skilled workers, the system is aimed at extracting the machining know-how data from the NC programs through reverse engineering. The extraction of the machining features and feature topologies has been addressed previously. The present paper deals with the extraction of machining operation data, including operation se...

Open Control Systems are the key enabler for the realization of modular and re-configurable manufacturing systems. The large number of special purpose machines and the high level of automation have led to an increasing importance of open control systems based on vendor neutral standards. This paper gives an overview on the past, present and future of Open Controller Architecture. After reflecting on the different criteria, categories and characteristics of open controllers in general, the CNC products in the market are evaluated and an overview on the world-wide research activities in Europe, North America and Japan is given. Subsequently the efforts to harmonize the different results are described in order to establish a common world-wide standard in the future. Due to the “mix-and-match” nature of open controllers concentrated attention must be paid to testing mechanisms in the form of conformance and interoperability tests.

An open servo control system for an intelligent CNC machine tool system has been proposed and developed. The developed system is equipped with real-time access window, through which user custom application software can monitor or modify any parameters and variables of servo system in a real time manner as a parallel session while the standard servo control is being performed. The developed system has been implemented in a CNC vertical machining center for feasibility study by integrating the software model reference adaptive control as custom application. The experimental results have successfully demonstrated the effectiveness of the open servo system.

The machining feature is a high-level product geometric representation and macro description of the product geometry. It is vital to machining operation planning and integration of CAD and CAM systems. In the feature-based operation planning, given a feature, the operator needs its associated machining operation data. Since successful NC programs contain machining know-how of skilled workers associated with the machining features, this paper studies the recognition of machining features in milling from the NC programs through reverse engineering, for reuse of the know-how in operation planning. First, the concepts of the machining element, machining feature and feature topology are presented, and the classification and representation of the features are performed from the machining point of view. Then algorithms for recognizing the machining features and feature topologies by analyzing NC programs are developed based on progressive Z-maps. Finally, a prototype is developed to extract the machining features and their associated operation data, and the machining know-how database is generated accordingly. The recognition of a variety of machining features and topologies, as well as their associated machining operations, is demonstrated through an example part from NIST parts repository. By using the generated machining know-how database, the machining operation planning will be automated by its counterpart system—the machining operation planner.

To automate machining process planning, the acquisition and representation of machining knowledge or know-how in a reusable way is needed. The machining know-how is implied in NC programs made by experienced workers. In this paper, the methodology and system for extracting machining know-how in milling operations have been developed. With the system, machining features, operations and their associated cutting conditions (depth of cut, feed rate and spindle speed, etc.) and machining method can be extracted by analysing NC programs in conjunction with the tools used and workpiece blank model. The milling know-how is represented as a collection of these extracted data that can be used in future machining operations. To verify the system, actual NC programs for milling have been analysed and the milling know-how has been extracted successfully.

In-process measurement of volumetric accuracy is an effective method to enhance the machine tool motion accuracy for quality machining operations. This paper describes a new three dimensional linear encoder system for measuring the on-axis volumetric accuracy of machine motion. The proposed system consists of three cross-grid grated scales with three sensor-heads, each of which includes six opto-electronic sensing elements. The system uses a noncontact scanning principle to detect six degree-of-freedom motion errors. These represent three linear and three angular displacements along a moving axis. The evaluation tests on the prototype system have successfully demonstrated the feasibility of the proposed technology.

The paper deals with the autonomous programming technology for the high speed coordinate measuring machine (CMM). In order to provide the breakthrough technology to enhance the operability of CMMs to be used for in-line measurement of mechanical parts, a new autonomous programming method which automatically generates a CMM program from the CNC program used for machining of the part is proposed. The developed technology can provide new functionality such as efficient work-in-progress measurement capability without using the CAD product model based approach.

Dynamic allocation of manufacturing activity on a global scale is a trend in today's manufacturing business. The paper describes the philosophical approach necessary to succeed in global scale manufacturing. The importance of the manufacturing business in conjunction with the promotion of society is emphasised from the historical and effects points of view. Today's problems caused by concentrated off-market manufacturing are pointed out and shift to in-market manufacturing, including the dynamic allocation of production technologies and human resources in the market, is explained as a solution. Two types of objective approach for implementing in-market manufacturing in a multi-culture environment on a global basis are proposed and the advantages and disadvantages are discussed.

The use of a self-propelled mobile robot working in close proximity to a support vehicle for purposes of power, materials, etc. would be extremely valuable for highway maintenance and construction operations. This paper discusses the development of such a uniqe mobile robot system and emphasizes the robot's control system. The wheeled mobile robot is differentially steered and tethered to a support vehicle via a mechanical linkage which has position tracking capability. This mobile robot system has been termed the tethered mobile robot (TMR), and such an approach has the potential for use in a wide variety of highway maintenance operations. An optimal control system applicable to many highway maintenance operations is designed and implemented through the utilization of recently developed servo control technology. Experimental results presented show significant promise for the TMR system.

The paper deals with the new controller for the high performance CNC machine tools. The controller proposed is referred to as “TRUE-CNC.” “TRUE” means Transparent, Transportable and Transplantable, Revivable, User-reconfigurable, and Evolving. TRUE-CNC allows the operator to achieve the maximum productivity and highest possible quality of the machined parts in a given environment with autonomous capturing of the machining operation proficiency. The TRUE-CNC controller provides intelligent functions for less-skilled operator to run the high performance machine tools as if a skilled operator does. The concept and design aspects of the system architecture and the algorithms for functions developed for the TRUE-CNC are described in the paper.

In this paper we describe a new design of a fluid-driven microactuator which comprises a planar piston, a four-way control valve, and a mechanical feedback system that controls the output in accordance with an input displacement. Merits of this design are expected in terms of output density, scalability, and feedback ability realized with no electronic devices. Fabrication processes of the microactuator include bulk micromachining of two sheets of silicon substrate and their assembly by electro static bonding to glass plates. The output characteristics were measured while compressed air was supplied. Generated output force showed an almost linear relation ship to supplied pressure and to valve displacement. However, the magnitude was asymmetric in terms of driven directions, which resulted from geometrical configuration essentially introduced by an anisotropic etching of the silicon substrate The position of the output shaft was sufficiently controlled with a designec magnification factor multiplied to the input displacement in both static and dynamic senses.

Ceramic coatings have a considerable potential to be used as thermal barriers and improve corrosion and wear resistance of metallic materials at high temperatures. In particular, BN ceramics are excellent candidates for thermal barrier materials because they have superior corrosion and abrasion resistance, low thermal conductivity and high temperature stability. In general, above 1,273 K ceramics have better strength, creep oxidation resistance than metals or superalloys. It is well known that ceramic coatings are difficult to apply on metal substrates due to the different atomic bonding between ceramic and metals. To provide the expected protection, ceramic coating of metals must provide good interfacial bonding, suitable adherence and interface stability. These may be achieved by different processing approaches such as: diffusion bonding under pressure application, thermal spray or mechanical bonding. An alternative method may be sinter-bonding using P/M techniques such as hot isostatic pressing (HIP) when simultaneous sintering of ceramic powders and bonding onto the metal substrate can take place. The purpose of this present work is to verify the potential of the plasma assisted sintering (PAS) process to develop a good diffusion bonding between a BN ceramic layer and the metal substrate while sintering the ceramic layer. In contrast tomore » HIP techniques, sintering and coating in PAS can be completed in a very short time (minutes as compared to hours) concurrent with an observed (not yet demonstrated) capability of particle surface cleaning by removing surface oxides or trapped gases.« less

This paper deals with the discrete error analysis of material error calculation in Dynamic Machining Simulator (DMS). DMS can simulate the material removal per tool revolution in a real-time fashion when the tool moves along the path defined by a CNC program. Based on calculated removal rate, the feed rate is optimized so that the loading to the tool can be maintained at the permissive maximum value. In this simulation technique, the accuracy of the material removal calculation which is to be performed in a discrete manner, is very important to achieve the reliable control. In this study, the algorithm for error analysis is developed and optimum values of simulation parameters are determined for three typical end mill operation.