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Successful and efficient hybrid manufacturing consisting of Directed Energy Deposition (DED) followed by milling as a postprocess requires that material deposited during the DED step be geometrically consistent and slightly larger than the desired final, machined dimensions. DED clad width is directly correlated to meltpool energy, while powder fluence directly correlated to DED clad cross-sectional area. Due to heat accumulation into the DED part during deposition, meltpool energy does not remain constant without modification of DED process parameters over the deposition cycle. Meltpool energy is typically managed by decreasing the laser power to reduce the energy fluence into the meltpool – though this technique limits DED productivity. If the working distance and laser optics within the deposition head are static, energy fluence reduction can also be achieved by increasing deposition head feedrate. Modifying powder mass flowrate through the deposition nozzle to maintain powder fluence into the meltpool allows for both the clad geometry to be maintained while also increasing the productivity of the DED process. Numerical simulation of the heat flow in a DED thin wall part was used to derive laser energy fluence values to maintain a constant meltpool energy. Derived values were tested using both the laser power and feedrate to moderate energy fluence into the meltpool. Results are compared to a thin wall deposited without meltpool energy control. Clad geometry variation and cycle time are both shown to reduce when using a feedrate-based meltpool energy control method as compared to laser power-based meltpool energy control or no meltpool energy control, increasing the geometric accuracy for postprocess machining and productivity.

The directed energy deposition (DED) process enables the production of near net shape parts in the starting form of either powder or wire melted by a focused energy source, such as laser. The target geometry is then built layer by layer. In theory, engineering components with complex shapes can be fabricated with a single setup using a hybrid CNC machine tool, which has capabilities of both DED and traditional subtractive machining processes. However, the issue of inaccurate DED deposited geometry and insufficient material deposition results in the repetition of the hybrid process to achieve the goal geometric dimension. This paper presents a generalized strategy for different materials that plan DED toolpath for the planar geometric feature to achieve its required final geometric dimension by using only a single hybrid manufacturing cycle based on simulated results and validate the strategy experimentally by using a hybrid CNC machine.

Sapphire capillaries manufactured with high efficiency and precision are needed for use in laser–plasma accelerators. A hybrid manufacturing process combining femtosecond laser machining and diamond tool micromilling was applied. By using a femtosecond laser mounted on a 5-axis machine, a capillary with a groove width of 630 µm and length of 90 mm was fabricated on a sapphire plate within 5 h. The surface roughness of the bottom of the cylinder groove was finished to 7.1 nm in Sa by milling with a polycrystalline diamond end mill.

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.

Ultra-precision machining of single crystalline sapphire was performed using a polycrystalline diamond (PCD) micro-milling tool. Examination of the machining characteristics indicates that a high-quality surface with a nanometre-scale surface roughness can be obtained when the removed chips are thin enough to achieve ductile-mode machining. Although a high-quality surface was successfully machined, the surface roughness gradually deteriorated and the actual depth of the machined groove became shallower as the machining distance increased because of the build-up of material adhering to the surface of the tool. To retain the milling capabilities of the PCD tool, an electrochemical-assisted surface reconditioning process has been proposed. The reconditioning technique was found to be effective in removing the surface contaminant without causing damage to the edges of the tool.

Since binder-less polycrystalline diamond (BLPCD) has no macro cleavage planes and highest hardness, it is desirable material for micro milling tools. However, fabricating micro tools made of BLPCD by conventional method such as grinding is very time consuming due to its extremely high hardness. This paper describes the successful results obtained in our recent study on productive machining of BLPCD using femtosecond-pulsed laser (FSPL). The ablation effect of BLPCD by FSPL has been studied by conducting a series of experiments. Also, the predictability of ablation effect of FSPL when machining BLPCD has been evaluated by introducing numerical analysis model.

A study was performed to investigate the effects of the application of an atmospheric-pressure plasma jet during polycrystalline diamond (PCD) micro- end-milling. A comparison was made between SiC surfaces after milling, with and without the application of the plasma jet. The plasma jet was found to allow the formation of a high-quality surface with an average roughness ( R a ) of 0.73 nm. The proposed plasma jet is highly effective in improving both the chip formation process, by imparting hydrophilicity to the tool and workpiece surfaces, and removing surface contamination at the tool edge during machining.

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.

In machine tools, the difference between the position of the tool center point and that of position detectors of the control system leads to a dynamic mechanical error, which is obtained as the difference between the feedback-controlled table position and the position of the tool relative to the table (tool–table relative position). In this paper, analysis methods are proposed to roughly determine the component of the mechanical system that causes the dynamic mechanical error. Two methods, a two-encoders method and a four-accelerators method, for investigating the influence of the mechanical component on the dynamic mechanical error are proposed. In both methods, the frequency response function between the feedback-controlled table position and the tool–table relative position is evaluated. By the proposed methods, the dynamic mechanical error of a high-precision machining center in the X and Y directions is analyzed for frequencies up to 200 Hz. It was found that the entire frequency range could be divided into three distinct subranges depending on how the component of the mechanical system influences the dynamic mechanical error at different frequencies. The analysis results indicated that in the low-frequency range, the dynamic response of the driven component plays a dominant role in influencing the dynamic mechanical error. Then, the dynamic mechanical error of the experimental machine was measured for small circular motions. The dynamic mechanical error occurred at the micrometer level. The dynamic mechanical error can be estimated from the frequency response function measured by the proposed method.

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.

The demand for micromachining methods for single crystal silicon has been steadily increasing. Micro tools made from polycrystalline diamond (PCD) have considerable promise in this regard. However, it has been a concern that contamination of the PCD tool surface can give rise to an increase in frictional resistance during machining, leading to degradation of the surface integrity of the workpiece. In this study, the feasibility of surface reconditioning using a specific electrochemical technique was investigated. The technique was found to be effective in removing surface contamination without causing any damage to the tool edges.

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.

One of the biggest challenges for mechanical micro/nano milling is the design and fabrication of high precision and high efficiency micro milling tools. Commercially available micro milling tools are either too expensive (around several hundred US dollars) or simply made from downsizing of macro milling tools, which is sometimes not appropriate for the specific micro/nano milling requirements. So the design and fabrication of custom micro milling tools are necessary. In this paper, a micro straight edge endmill (SEE) is designed. Static and dynamic FEM analyses have been done for the SEEs with different rake angles trying to identify their stiffness and natural frequencies. By wire electrical discharge machining (WEDM), the SEEs made of polycrystalline diamond (PCD) with three different rake angles have been fabricated. The evaluation milling on tungsten carbide (WC) and silicon wafer have processed on a nano milling center. Experimental results show the SEEs have a good ability to simultaneously micro/nano milling of both the side and bottom surfaces with submicron surface roughness, and the SEE has high accuracy for large aspect ratio thin wall machining. The milling experiments on silicon wafer have successfully demonstrated that ductile mode machining was achieved and the coolant played an important role in silicon wafer milling.

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.

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.

There are strong needs for productive/quality machining strategies of notoriously “difficult-to-machine” aerospace materials. The current means of machining these materials is dominated by mechanical cutting methods, which are costly due to high tooling costs, poor surface quality and limitations in the workpiece features and operations that can be machined. The newest EDM technology may be able to circumvent problems encountered in mechanical machining methods. In this paper, the EDM technology has been used to machine titanium alloy Ti–6Al–4V to investigate the effect of Ti–6Al–4V's thermal and electrical properties on the EDM productivity. In the study, temperature measurements have been made for Ti–6Al–4V workpieces with various duty factors to clarify the essential causes of difficulty in machining titanium alloys and observe the optimal duty factor in terms of productivity and quality.

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.

NC program processing plays a vital role in CNC machining. Existing CNC systems support only CNC builder-specific NC program input and this limits the potential application of many NC programs that have the same functions with different formats. In order to manage the variety of NC programs available, a universal NC program processor was developed that can accept and process any kind of NC program. This processor consists of two main components: the first is an NC dictionary, which is generated by an NC specification dictionary generator from the corresponding NC specification, and the second is an interpreting engine, which checks the different input NC programs and generates canonical machining functions in terms of the NC specification dictionary and the canonical machining function library. Finally, a prototype system is built to evaluate the proposed design followed by a successful case study.

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.

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.

This paper develops a comprehensive interpolation scheme for non-uniform rational B-spline (NURBS) curves, which does not only simultaneously meet the requirements of both constant feedrate and chord accuracy, but also real-time integrates machining dynamics in the interpolation stage. Although the existing work in this regard has realized the importance to simultaneously consider chord error and machining dynamics, none has really incorporated these in one complete interpolation scheme. In this paper, machining dynamics is considered for three aspects: sharp corners or feedrate sensitive corners on the curves, components with high frequencies or frequencies matching machine natural ones and high jerks. A look-ahead module was developed for detecting and adaptively adjusting the feedrate at the sharp corners. By Fast Fourier Transform (FFT) analysis with a moving window in the interpolation stage identified were some special frequency components such as those containing high frequencies or with frequencies matching machine natural ones. Then, the notch filtering or time spacing method was used to eliminate these components. To more completely reduce feedrate and acceleration fluctuations, the jerk-limited algorithm was also developed. Finally, the interpolated feedrate was further smoothened with B-spline fitting method and the NURBS curves were re-interpolated with the smoothened feedrate. During the interpolation, the chord error was repeatedly checked and confined in the prescribed tolerance. Two NURBS curves were used as examples to test the feasibility of the developed interpolation scheme.

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.

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.

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...

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.

This article deals with high efficiency and high accuracy fine boring in a monocrystalline silicon ingot by electrical discharge machining (EDM). In manufacturing process of integrated circuits, a plasma-etching process is used for removing oxidation films. This process has recently been examined for use of monocrystalline silicon as the electrode to minimize the contamination. However, it is difficult to machine silicon accurately by the conventional diamond drilling method, because the material removal is due to brittle fracture. The machining force in the EDM process is very small compared with that in conventional machining, therefore, the possibility of high efficiency and high accuracy boring holes in silicon ingot by EDM is experimentally investigated. The removal rate of monocrystalline silicon by EDM is much higher than that of steel, while the electrode wear is extremely small. The improvement method leads to a better hole without chipping at the exit of hole or sticking of the insulator on the wall of hole. Furthermore, it is proved that even a high aspect ratio of about 200 boring is possible.

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.

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.

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.

The paper deals with a study on technologies to enhance the manufacturing productivity of a product consisting of sculptured surfaces. A process planning system coupled with real time machining is proposed such that the productive machining plan and tool motion can automatically be generated once available resources and machining know-how are given for the metal cutting-EDM mixed environment. The system proposed consists of geometry feature recognition, cutting mode and tool selection, real time tool path generation with adaptive feedrate generation using concurrent real time machining simulation. The system was prototyped to verify the feasibility. Successful results were obtained.

This paper presents an investigation of micro electrical discharge machining (µEDM) as a viable method for micromachining 3D shapes in silicon. The approach integrates a two-step µEDM process with standard silicon microfabrication techniques to create smooth and axisymmetric 3D hemispherical structures with eccentricity, e ∼ 0.11 and a radius variation < 2%. Through the selection of ultrahard polycrystalline diamond as the µEDM electrode, the low tool wear allows for high throughput machining of 200 wells in silicon within a short total processing time of 80 min. Feasibility of the approach is demonstrated in the fabrication of millimeter scale hemispherical shell structures using the machined silicon features as a mold.

The paper deals with a new method for the productive machining of molds and dies which have an artistic geometry characterized by sculptured surfaces. The method developed is referred to as a “Real Time Model Reference Adaptive Control” which autonomously adjusts the optimal feedrate such that the material removal should always be maximized with respect to the capability of a given tool and a given geometry of a workpiece by using a real time simulation of a software-based cutting process model. The practical feasibility of the proposed scheme has been verified through experiments performed on the prototyped system.

High-current pulsed electron beams (HCPEB) irradiation is a new potential method to polish hard steels and alloys. After HCPEB machining, the performance of machined surface, such as corrosion resistance and micro-structure, has been greatly improved. Because of its good performance, HCPEB irradiation is playing more and more important roles in polishing hard steels and alloys. However, it is not clear about the energy density of HCPEB under different beam conditions. In this study, experiments have been conducted to investigate the formation of HCPEB and its energy density. Then, effects of argon gas pressure and the applied voltage to solenoid coil on the formation of HCPEB are analyzed. Finally, a mathematical model is developed to describe the relationship between five dominant beam parameters with the energy density of HCPEB, which has a good accuracy in comparison to the experimental results.

Precision machine tools require in-process measurement of volumetric accuracy for machining and calibration. This paper describes the development and evaluation of the mounting of a previously presented volumetric linear encoder for measuring the onaxis volumetric motion accuracy. The encoder is based on three cross-grid gratings as measurement bodies and a sensor-head consisting of six optical sensing elements. In order to implement this device for machine tool testing, mounting flexures were used as mounting link. This allows repeatable measurements under varying environmental conditions.

NURBS interpolator has great advantages for machining complex part comparing to the simple linear and circular interpolator, such as reducing program size, smoothing tool motion and improving machining surface quality. However, the existing NURBS interpolators only deal with the case in which the NURBS trajectory is given in a customized NURBS G code. In addition, they are limited to three translation axes, which mean no rotation axes were considered so far. In this paper, a unified NURBS interpolator was developed to treat three kinds of situations so that NURBS interpolator can be thoroughly applied into five-axes machining. In first case, a NURBS curve converter was built to convert a series of linear and circular segments exactly to a NURBS trajectory. In second case, a series of linear and circular segments were fitted to a NURBS trajectory, which obtains the optimal smoothness instead of exactly representing. In third case, two kinds of NURBS G codes were proposed to represent NURBS trajectory directly, which includes both three translation axes and two rotation axes. Upon these three kinds of input NURBS trajectory, only one NURBS interpolator is designed, in which, most factors that influence the five-axes CNC machining performance are considered. Also, a three-steps NURBS interpolation algorithm was implemented inside the proposed interpolator. Two actual five-axes machining examples were used to evaluate the performance of the proposed interpolator.Copyright © 2005 by ASME

This paper presents an on-machine modeling system that tries to bridge the gap between the design and the machining. This system is able to build a comprehensive solid model of the CNC machining workspace after the workpiece and fixtures have been installed onto the working table. This solid model can be used for simulation to enhance its credibility. For this purpose, one prototype of a 3D visual modeling system is proposed and designed. In order to accurately calibrate CCD cameras upon the absolute coordinate frame of the machining center, a practical calibration method is presented at first. To segment the target part and extract its 2D features on the captured images, the techniques of Image Decomposition and a modified Standard Hough Transform (SHT) are designed. Using these 2D features, the 3D visual stereovision system, powered by a designed feature matching engine, is capable of obtaining the 3D features of the target part. Furthermore, the part has been identified by the object recognition technology. This recognition includes part recognition and pose recognition. In the part recognition, the part is recognized and an initial pose transform is obtained. Using this initial pose transform, the pose optimization method, named as Dual Iterative Closest Lines (DICL), is designed to locate the optimum position and orientation of the solid model of the recognized part. Finally, this modeling system is tested on a machining center. The experimental result indicates the innovation and feasibility of the proposed modeling system.