Showing papers in "Journal of Manufacturing Science and Engineering-transactions of The Asme in 2005"

Three-Component Receptance Coupling Substructure Analysis for Tool Point Dynamics Prediction

Abstract: In this paper we present the second generation receptance coupling substructure analysis (RCSA) method, which is used to predict the tool point response for high-speed machining applications. This method divides the spindle-holder-tool assembly into three substructures: the spindle-holder base; the extended holder; and the tool. The tool and extended holder receptances are modeled, while the spindle-holder base subassembly receptances are measured using a “standard” test holder and finite difference calculations. To predict the tool point dynamics, RCSA is used to couple the three substructures. Experimental validation is provided.

Degradation Assessment and Fault Modes Classification Using Logistic Regression

Abstract: Real-time health monitoring of industrial components and systems that can detect, classify and predict impending faults is critical to reducing operating and maintenance cost. This paper presents a logistic regression based prognostic method for on-line performance degradation assessment and failure modes classification. System condition is evaluated by processing the information gathered from controllers or sensors mounted at different points in the system, and maintenance is performed only when the failure/ malfunction prognosis indicates instead of periodic maintenance inspections. The wavelet packet decomposition technique is used to extract features from non-stationary signals (such as current, vibrations), wavelet package energies are used as features and Fisher's criteria is used to select critical features. Selected features are input into logistic regression (LR) models to assess machine performance and identify possible failure modes. The maximum likelihood method is used to determine parameters of LR models. The effectiveness and feasibility of this methodology have been illustrated by applying the method to a real elevator door system.

Ductile Regime Nanomachining of Single-Crystal Silicon Carbide

Abstract: We have demonstrated the ability to perform a ductile material removal operation, via single-point diamond turning, on single-crystal silicon carbide (6H). To our knowledge, this is the first reported work on the ductile machining of single-crystal silicon carbide (SiC). SiC experiences a ductile-to-brittle transition similar to other nominally brittle materials such as silicon, germanium, and silicon nitride. It is believed that the ductility of SiC during machining is due to the formation of a high-pressure phase at the cutting edge, which encompasses the chip formation zone and its associated material volume. This high-pressure phase transformation mechanism is similar to that found with other semiconductors and ceramics, leading to a plastic response rather than brittle fracture at small size scales.

Simultaneous Stability and Surface Location Error Predictions in Milling

Abstract: Optimizing the milling process requires a priori knowledge of many process variables. However the ability to include both milling stability and accuracy information is limited because current methods do not provide simultaneous milling stability and accuracy predictions. The method described within this paper, called Temporal Finite Element Analysis (TFEA), provides an approach for simultaneous prediction of milling stability and surface location error. This paper details the application of this approach to a multiple mode system in two orthogonal directions. The TFEA method forms an approximate analytical solution by dividing the time in the cut into a finite number of elements. The approximate solution is then matched with the exact solution for free vibration to obtain a discrete linear map. The formulated dynamic map is then used to determine stability, steady-state surface location error, and to reconstruct the time series for a stable cutting process. Solution convergence is evaluated by simply increasing the number of elements and through comparisons with numerical integration. Analytical predictions are compared to several different milling experiments. An interesting period two behavior, which was originally believed to be a flip bifurcation, was observed during experiment. However, evidence is presented to show this behavior can be attributed to runout in the cutter teeth.

Modeling of a Single Resistance Capacitance Pulse Discharge in Micro-Electro Discharge Machining

Abstract: Micro-EDM (electro discharge machining) is a derived form of EDM process especially evolved for micro-machining. The use of resistance capacitance pulse generator, an advanced controller for machining in smaller interelectrode gaps and with lower discharge energies than in EDM, makes the material removal characteristics of a single discharge in micro-EDM different from that of the EDM. A comprehensive model predicting the material removal in a single discharge in micro-EDM is conceptualized. The model incorporates various phenomena in the prebreakdown period. It considers plasma as a time-variable source of energy to the cathode and anode to evaluate material removal at the electrodes. The plasma temperature and radius of the crater at the cathode (workpiece) predicted using the model were found to agree well with the experimental data in the literature.

Quintic Spline Interpolation With Minimal Feed Fluctuation

Abstract: This paper presents a parameterization and an interpolation method for quintic splines, which result in a smooth and consistent feed rate profile. The discrepancy between the spline parameter and the actual arc length leads to undesirable feed fluctuations and discontinuity, which elicit themselves as high frequency acceleration and jerk harmonics, causing unwanted structural vibrations and excessive tracking error. Two different approaches are presented that alleviate this problem. The first approach is based on modifying the spline tool path so that it is optimally parameterized with respect to its arc length, which allows it to be accurately interpolated in real-time with minimal complexity. The second approach is based on scheduling the spline parameter to accurately yield the desired arc displacement (hence feed rate), either by approximation of the relationship between the arc length and the spline parameter with a feed correction polynomial, or by solving the spline parameter iteratively in real-time at each interpolation step. This approach is particularly suited for predetermined spline tool paths, which are not arc-length parameterized and cannot be modified. The proposed methods have been compared to approximately arc-length C 3 quintic spline parameterization (Wang, F.-C., Wright, P. K., Barsky, B. A., and Yang, D. C. H., 1999, Approximately Arc-Length Parameterized C 3 Quintic Interpolator)' Splines, ASME J. Mech. Des, 121, No. 3., pp. 430-439) and first-and second-order Taylor series interpolation techniques (Huang, J.-T., and Yang, D. C. H., 1992, Precision Command Generation for Computer Controlled Machines, Precision Machining: Technology and Machine Development and Improvement, ASME-PED 58, pp. 89-104; Lin, R.-S. 2000, Real-Time Surface Interpolator for 3-D Parametric Surface Machining on 3-Axis Machine Tools, Intl. J. Mach. Tools Manuf., 40, No.10, pp. 1513-1526) in terms of feed rate consistency, computational efficiency, and experimental contouring accuracy.

Modeling of Cutting Forces Under Hard Turning Conditions Considering Tool Wear Effect

Abstract: Quantitative understanding of cutting forces under hard turning conditions is important for thermal modeling, tool life estimation, chatter prediction, and tool condition monitoring purposes. Although significant research has been documented on the modeling of forces in the turning operation in general, turning of hardened materials involves several distinctive process conditions, including negative tool rake angle, large tool nose radius, and rapid tool wear. These process conditions warrant specific treatment in the analysis of cutting forces. This paper first addresses these issues by formulating an oblique chip formation force model through the extension of a two-dimensional (2D) mechanistic force model while considering the effect of tool geometry complexities. The coefficients of the mechanistic force model are estimated by applying a genetic algorithm in overcoming the lack of explicit normal equations. Then the forces occurring due to flank wear are modeled by extending a 2D worn tool force modeling approach into a three-dimensional analysis to accommodate the effect of low feed rate, small depth of cut, and relatively large tool nose radius in hard turning. The total cutting forces are the linear summation of forces due to chip formation and forces due to flank wear. The model-predicted forces match well with experimental results in the turning of hardened 52100 bearing steel under practical cutting conditions (low feed rate, small depth of cut, and gentle cutting speed) using cubic boron nitride (CBN) tools under the progressive tool flank wear conditions.

Numerical Prediction of Static Form Errors in Peripheral Milling of Thin-Walled Workpieces With Irregular Meshes

Abstract: The finite element formulation is studied in this paper to predict static form errors in the peripheral milling of complex thin-walled workpieces. Key issues such as cutter modeling, finite element discretization of cutting forces, tool-workpiece coupling and variation of the workpiece 's rigidity in milling are investigated. To be able to predict static form errors on the machined surface of complex form, considerable improvements are made on the proper modeling of the material removal in milling and the iterative calculations of tool-workpiece deflections. A general simulation approach is developed based on 3D irregular finite element meshes. By using illustrative examples, rigid and flexible models are compared with existing ones to show the validity of the approach.

3D Ball-End Milling Force Model Using Instantaneous Cutting Force Coefficients

Abstract: Application of a ball-end milling process model to a CAD/CAM or CAPP system requires a generalized methodology to determine the cutting force coefficients for different cutting conditions. In this paper, we propose a mechanistic cutting force model for 3D ball-end milling using instantaneous cutting force coefficients that are independent of the cutting conditions. The uncut chip thickness model for three-dimensional machining considers cutter deflection and runout. An in-depth analysis of the characteristics of these cutting force coefficients, which can be determined from only a few test cuts, is provided. For more accurate cutting force predictions, the size effect is also modeled using the cutter edge length of the ball-end mill and is incorporated into the cutting force model. This method of estimating the 3D ball-end milling force coefficients has been tested experimentally for various cutting conditions.

A Unique Methodology for Chatter Stability Mapping in Simultaneous Machining

Abstract: A novel analytical tool is presented to assess the stability of simultaneous machining (SM) dynamics, which is also known as parallel machining. In SM, multiple cutting tools, which are driven by multiple spindles at different speeds, operate on the same workpiece. Its superior machining efficiency is the main reason for using SM compared with the traditional single tool machining (STM). When SM is optimized in the sense of maximizing the rate of metal removal constrained with the machined surface quality, typical chatter instability phenomenon appears. Chatter instability for single tool machining (STM) is broadly studied in the literature. When formulated for SM, however, the problem becomes notoriously more complex. There is practically no literature on the SM chatter, except a few ad hoc and inconclusive reports. This study presents a unique treatment, which declares the complete stability picture of SM chatter within the mathematical framework of multiple time-delay systems (MTDS). What resides at the core of this development is our own paradigm, which is called the cluster treatment of characteristic roots (CTCR). This procedure determines the regions of stability completely in the domain of the spindle speeds for varying chip thickness. The new methodology opens the research to some interesting directions. They, in essence, aim towards duplicating the well-known stability lobes concept of STM for simultaneous machining, which is clearly a nontrivial task.

Study on Edge Chipping in Rotary Ultrasonic Machining of Ceramics: An Integration of Designed Experiments and Finite Element Method Analysis

Abstract: Rotary ultrasonic machining (RUM) is a relatively low cost and environmentally benign process for machining of advanced ceramics. Much effort has been made to theoretically and experimentally investigate material removal rate, surface roughness, and tool wear in RUM. However, there is no report on systematic study of edge chipping in RUM drilling of ceramics. This paper presents the results of a study on edge chipping in RUM drilling of advanced ceramics. The study is conducted by an integrated approach, combining designed experiments and FEM (finite element method) analysis. The designed experiments will reveal the main effects as well as interaction effects of process variables (spindle speed, ultrasonic power, feedrate, and grit size) on cutting force and chipping thickness. FEM simulations will provide the stress and strain distributions in the workpiece while being drilled by RUM. Furthermore, the relationship between chipping thickness and cutting force obtained from the FEM simulations will be compared with that obtained from the designed experiments.

Analysis of the Cutting Force Components and Friction in High Speed Machining

Abstract: An original experimental device is used to reproduce conditions of orthogonal cutting for a wide range of cutting speeds (from 15 to about 100 m/s) (Sutter et al.). Improvement of the initial device (Sutter et al.) makes it possible to record both values of normal and tangential forces in orthogonal cutting. An analysis of the tool-chip friction is then possible for a large range of cutting speeds. The evolution of cutting force components as well as the evolution of the friction coefficient are presented and analyzed. In addition, the process of chip formation during high speed machining is illustrated by photographic recording with a high speed camera.

Sensor Placement for Effective Diagnosis of Multiple Faults in Fixturing of Compliant Parts

Abstract: This paper presents a new sensor placement methodology for effective fault diagnosis in an N-2-1 locating scheme used in compliant sheet metal assembly processes. The proposed approach is based on the effective independence (EfI) sensor placement method. The EfI method is a computational algorithm that starts with all feasible sensor locations and reaches the desired number of locations, by progressively eliminating those having the least contributions to the linearly independent manifestation of the fixture faults. The least squares method was adopted to identify fixture faults from measurement data. An automotive panel part was considered to illustrate the suggested methodology. The sensors placed by the EfI method enable the effective identification of multiple fixture faults even in the presence of moderate measurement noise.

Modeling of Workpiece Location Error Due to Fixture Geometric Error and Fixture-Workpiece Compliance

Abstract: Several fixture-related error sources contribute to workpiece location error in a machining system. Inaccurate part placement in the fixture relative to the cutting tool, for example, can negatively affect the quality of the part. In this paper the following major sources of error are considered: fixture geometric error and elastic deformation of the fixture and workpiece due to fixturing forces. The workpiece location error is predicted by modeling the process of part loading (given fixture geometric variations) and clamping (given deformations at the contact points) in a machining fixture. Linear elastic models for the fixture elements, contact mechanics models for the contact regions, and flexibility influence coefficients to capture the bulk elasticity of the workpiece have been used to model the compliance of the entire fixture-workpiece system. The deformations at the contact points are obtained by solving a constrained optimization model. The effect of geometric errors and compliance on workpiece location error is examined using part response points as a measure of quality. Experimental validation is also provided for several fixture-workpiece variable levels using a 3-2-1 machining fixture.

Optimal Module Selection for Preliminary Design of Reconfigurable Machine Tools

Abstract: Presented in this paper is a feature-based method for selecting an optimal (minimum yet sufficient) set of modules necessary to form a reconfigurable machine tool for producing a part family. This method consists of two parts. In the first part, a feature-module database is created to form a selection space, where the machinable geometric features identified in STEP are defined as functional requirements (FR's) and the structural component modules derived from the conventional machine tools as design parameters (DP's). An inner FR-to-DP mapping mechanism within the database is based on the Membership Grade Matrix, which defines metrics to quantify the degree of association between a FR and a DP Within the confines of the selection space built upon this FR-DP database, the second part of the method involves a two-step procedure for module selection. The first step is to select the modules from this space to construct all the required individual configurations of the reconfigurable machine tool. The second step is to maximize the number of common modules among the originally selected modules through re-selection. A case study on designing a reconfigurable machine tool dedicated to a given family of die molds is conducted and discussed.

Optimal Tool Orientation for Five-Axis Tool-End Machining by Swept Envelope Approach

Abstract: This paper presents a swept envelope approach to determining the optimal tool orientation for five-axis tool-end machining. The swept profile of the cutter is determined based on the tool motion. By analyzing the swept profile against the part geometry, four types of machining errors (local gouge, side gauge, rear gouge, and global collision) are identified. The tool orientation is then corrected to avoid such errors. The cutter's swept envelope is further constructed by integrating the intermediate swept profiles, and can be applied to NC simulation and verification. This paper analyzes the properties of the swept profile of a general cutter in five-axis tool-end machining. The relation of the swept profile, the part geometry, the tool motion, and the machining errors is developed. Therefore, the error sources can be detected early and prevented during tool path planning. The analytical results indicate that the optimal tool orientation occurs when the curvature of the cutter's swept profile matches with the curvature of the local part surface. In addition, the optimal cutting direction generally follows the minimum curvature direction. Computer illustrations and example demonstrations are shown in this paper. The results reveal the developed method can accurately determine the optimal tool orientation and efficiently avoid machining errors for five-axis tool-end machining.

A comparative study of single-phase AC and multiphase DC resistance spot welding

Abstract: This paper presents a comparative study of the AC and MFDC resistance spot welding process. Both experiments and finite element simulation were conducted to compare the weld size and energy consumption. The experiments were performed on two identical spot welding machines, one with a single phase ac and the other with a mid-frequency DC weld control. The machines were instrumented such that both the primary and secondary voltage and current signals could be collected for energy calculation. The finite element simulation model was developed to understand the underlying mechanisms of the difference between the ac and MFDC processes. The effect of the current waveform was investigated by using the actual process measurements as an input to the simulation model. It is shown that the MFDC process generally produces larger welds than the AC process with the same root-mean-square welding current. However, this difference is more prominent when the welding current is relatively low. Overall, the AC welding process consumes more energy to make a same sized weld than the MFDC process. The larger the welding current is used, the less efficient the AC welding process will become. The differences between the two welding processes are caused by the contact resistance behavior and the electrical inductance in the AC welding process.

Assembly Fixture Fault Diagnosis Using Designated Component Analysis

Abstract: A new approach to fixture fault diagnosis, designated component analysis (DCA), is proposed for automotive body assembly systems using multivariate statistical analysis. Instead of estimating the fault patterns solely from the process data as in principal component analysis (PCA), DCA defines a set of mutually orthogonal vectors identified from known product/process knowledge to represent fault patterns, estimates their significance from data, and analyzes the correlation among the designated components. Hence, the sheet metal dimensional variation is mathematically decomposed into a series of mutually orthogonal rigid body motions with known patterns. Remaining deflections can be estimated by PCA after rigid body motions have been removed from the data. As a result, the designated components, along with their correlations, facilitate the diagnosis of multiple fixture faults that exist simultaneously and isolate deflections from other variation components. An application example is used to illustrate DCA's effectiveness and potentials.

A Metric-Based Approach to Two-Dimensional (2D) Tool-Path Optimization for High-Speed Machining

Abstract: Conventional tool-path generation strategies are readily available to generate geometrically feasible trajectories. Such approaches seldom take into consideration physical process concerns or dynamic system limitations. In the present work, an approach for improving a geometrically feasible tool-path trajectory based on quantifiable process metrics is developed. Two specific measures of toolpath quality are incorporated into the iterative improvement algorithm: instantaneous path curvature and instantaneous cutter engagement. These metrics are motivated by a desire to minimize acceleration requirements and maintain a stable steady-state cutting process during high-speed machining. The algorithm has been implemented for two-dimensional contiguous end-milling operations with flat end-mills, and case studies are presented to illustrate the approach.

Formability Analysis of Tailor-Welded Blanks of Different Thickness Ratios

Abstract: This paper presents a formability analysis of tailor-welded blanks (TWBs) made of cold rolled steel sheets with varying thicknesses. Steel sheets ranging between 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, and 1.0 mm in thickness were used to produce TWBs of different thickness combinations. The primary objective of this paper is to characterize the effects of thickness ratios on the forming limit diagram (FLD) for a particular type of TWB. The TWBs chosen for the investigation are designed with the weld line located in the center of the specimens perpendicular to the principal strain direction. Nd:YAG laser butt-welding was used to prepare different tailor-made blank specimens for uniaxial tensile tests and Swift tests. The experimental results of the uniaxial tensile test clearly revealed that there were no significant differences between the tensile strengths of TWBs and those of the base metals. After the Swift tests, the formability of TWBs was analyzed in terms of two measures: The forming limit diagram and minimum major strain. The experimental findings indicated that the higher the thickness ratio, the lower the level of the forming limit curve (FLC) and the lower the formability of the TWBs. The findings also show an inverse proportional relationship between thickness ratios and minimum major strains. TWBs with a thickness ratio of close to I were found to have a minimum major strain closer to those of base metals. The effects of different thickness ratios on TWBs were further analyzed with a finite element code in a computer-aided engineering package, PAM-STAMP, while the failure criteria of the TWBs in the finite element analysis were addressed by the FLCs which were obtained from the experiments. However, the weld of the TWB in the simulation was simply treated as a thickness step, whereas its heat affected zones were sometimes disregarded, so that the effects of the thickness ratio could be significantly disclosed without the presence of weld zones. The results of the simulation should certainly assist to clarify and explain the effects of different thickness ratios on TWBs.

A Scratch Intersection Model of Material Removal During Chemical Mechanical Planarization (CMP)

Abstract: A scratch intersection based material removal mechanism for CMP processes is proposed in this paper The experimentally observed deformation pattern by SEM and the trends of the measured force profiles (Che et al., 2003) reveal that, for an isolated shallow scratch, the material is mainly plowed sideway along the track of the abrasive particle with no net material removal. However, it is observed that material is detached close to the intersection zone of two scratches. Motivated by this observation, it is speculated that the deformation mechanism changes from ploughing mode to shear-segmentation mode as the abrasive particle approaches the intersection of two scratches under small indentation depth for ductile metals. The proposed mechanistic material removal rate (MRR) model yields Preston constant similar to those observed experimentally for CMP processes. The proposed model also reveals that the nature of the slurry-pad interaction mechanism, and its associated force partitioning mechanism, is important for determining the variation of MRR with particle size and concentration. It is observed that under relatively soft pads, small particles and low particle concentration, the pad undergoes local deformation, yielding an increased MRR with increasing particle size and concentration. At the other extreme, the intact walls of the surface cells and the connecting cell walls between the surface pores deform globally, resembling a beam or a plate, and a decreasing trend in MRR is observed with increasing particle size and concentration. The predicted MRR trends are compared to existing experimental observations.

A Chisel Edge Model for Arbitrary Drill Point Geometry

Abstract: An oblique cutting model is developed to predict the thrust and torque created by the chisel edge of a drill with an arbitrary point geometry. The chisel edge geometry is modeled using a mathematical representation of the flank grinding parameters and the flute geometry. The varying cutting angles at the chisel edge are determined and used to calculate the force contribution of each element using a mechanistic modeling approach. The model is validated for three commercial point geometries-the conical, helical and Racon® drill points. Model simulations match experimental data well for the geometries tested and show a marked improvement over the orthogonal cutting model.

Multi-operational machining processes modeling for sequential root cause identification and measurement reduction

Abstract: Variation propagation modeling has been proved to be an effective way for variation reduction and design synthesis in multi-operational manufacturing processes. However, previously developed approaches for machining processes did not directly model the process physics regarding how fixture, and datum, and machine tool errors generate the same pattern on part features. Consequently, it is difficult to distinguish error sources at each operation. This paper formulates the variation propagation model using the proposed equivalent fixture error concept. With this concept, datum error and machine tool error are transformed to equivalent fixture locator errors at each operation. As a result, error sources can be grouped and root cause identification can be conducted in a sequential manner The case studies demonstrate the model validity through a real cutting experiment and model advantage in measurement reduction for root cause identification.

Machining of Hard-Brittle Materials by a Single Point Tool Under External Hydrostatic Pressure

Abstract: This paper reports on the development of a machining device which is capable of carrying out precision machining experiments under external hydrostatic pressure. Machining trials were conducted on hard-brittle materials such as soda glass, quartz glass, silicon and quartz wafers using the newly developed machining device under the externally applied hydrostatic pressures of zero and 400 MPa. The machined traces were analyzed by laser microscope. From the trace profiles, crack ratio and area of cross section of the trace were estimated. The applied hydrostatic pressure enhanced the critical cross sectional area and reduced the cracks and chippings of all the tested materials. Effects of hydrostatic pressure on the machining characteristics of the crystalline and glassy materials are discussed in detail. The mechanism behind the enhancement of ductile-brittle transition by the externally applied hydrostatic pressure is also elucidated by a theoretical model.

Dynamics of Initial Penetration in Drilling: Part 1—Mechanistic Model for Dynamic Forces

Abstract: This two-part paper is aimed at developing a theoretical and numerical simulation basis for initial penetration phenomena that profoundly influence hole tolerances and shape. In Part I, dynamic force models are developed followed by models of the drill's dynamic behavior in Part 2. Next, these models are combined and used to predict initial penetration behavior and hole shape. A comparison of simulated and experimental results concludes Part 2. In this part, by considering the effects of drill grinding errors and drill deflections, dynamic cutting chip thickness models are developed which, in combination with workpiece surface inclination effects, allow the formulation of expressions for the dynamic chip thickness and cutting chip cross-sectional area. By using these quantities to replace their static counterparts, static drilling force models are extended to facilitate the prediction of dynamic cutting forces. Separate thrust, torque, and radial force models for the major cutting edges, secondary cutting edge, and for the indentation zone are formulated. The effects of drill installation errors on the radial cutting forces acting on the chisel edge and the major cutting edges are also included.

Optimization of Surface Grinding Operations Using Particle Swarm Optimization Technique

Abstract: The development of comprehensive grinding process models and computer-aided manufacturing provides a basis for realizing grinding parameter optimization. The variables affecting the economics of machining operations are numerous and include machine tool capacity, required workpiece geometry, cutting conditions such as speed, feed, and depth of cut, and many others. Approximate determination of the cutting conditions not only increases the production cost, but also diminishes the product quality. in this paper a new evolutionary computation technique, particle swarm optimization, is developed to optimize the grinding process parameters such as wheel speed, workpiece speed, depth of dressing, and lead of dressing, simultaneously subjected to a comprehensive set of process constraints, with an objective of minimizing the production cost and maximizing the production rate per workpiece, besides obtaining the finest possible surface finish. Optimal values of the machining conditions obtained by particle swarm optimization are compared with the results of genetic algorithm and quadratic programming techniques.

Development of a Six-Degree-of-Freedom Geometric Error Measurement System for a Meso-Scale Machine Tool

Abstract: This paper presents the development of a six-degree-of-freedom (DOF) geometric error measurement (6GEM) system that can be applied to the simultaneous measurement of six geometric error components of the moving axes of a mesa-scale machine tool (mMT). The system consists of a laser module constructed by a cube beam splitter and a pigtailed laser diode, three two-dimensional position sensitive detectors (PSDs), and an additional cube beam splitter. The loser module moving with the positioning system of the developed mMT testhed generates two perpendicular laser beams, one of which is further divided into two laser beams at the second cube beam splitter. These three laser beams are detected by the three PSDs, and the full pose of the laser module is then calculated simultaneously by forward and inverse kinematic computations. The calculated full pose of the laser module is translated into six-DOF geometric errors of the mMT testbed. A series of experiments are performed to demonstrate the effectiveness and accuracy of the proposed 6GEM system. The experimental results show that the measurement accuracy of the 6GEM system was better than ±0.6 μm for transiational error components and ±0.6 arcsec for angular error components.

General Framework of Optimal Tool Trajectory Planning for Free-Form Surfaces in Surface Manufacturing

Abstract: Surface manufacturing is a process of adding material to or removing material from the surfaces of a part. Spray painting, spray forming, rapid tooling, spray coating, and polishing are some of the typical applications of surface manufacturing, where industrial robots are usually used. Tool planning for industrial robots in surface manufacturing is a challenging research topic. Typical teaching methods are not affordable any more because products are subject to a shorter product life, frequent design changes, small lot sizes, and small in-process inventory restrictions. An automatic tool trajectory planning process is hence desirable for tool trajectory planning of industrial robots. Based on the computer-aided design model of a part, the tool model, task constraints, and optimization criteria, a general framework of optimal tool trajectory planning in surface manufacturing is developed. Optimal tool trajectories are generated by approximately solving a multiobjective optimization problem. To test if the generated trajectory satisfies the given constraints, a trajectory verification model is developed. Simulations are performed to determine if the given constraints are satisfied. Simulation results show that the optimal tool trajectory planning framework can be applied to generate trajectories for a variety of applications in surface manufacturing. This general framework can also be extended to other applications such as dimensional inspection and demining.

Analysis of Force Shape Characteristics and Detection of Depth-of-Cut Variations in End Milling

Abstract: This paper proposes an analytical approach to detect depth-of-cut variations based on the cutting-force shape characteristics in end milling. Cutting forces of a single-flute end mill are analyzed and classified into three types according to their shape characteristics. Cutting forces of a multiple-flute end mill are then classified by considering both the cutting types of the corresponding single-flute end mill and the degree of overlap of successive flutes in the cut. Force indices are extracted from the cutting forces and depth-of-cut variations are detected based on the changes of the force shape characteristics via the force indices in an end-milling process. The detection methodology is validated through cutting experiments.

Microscale Mechanical Behavior of the Subsurface by Finishing Processes

Abstract: Hard turning, grinding, and honing are common finishing processes in today 's production. The machined subsurface undergoes severe deformation and possible microstructure changes in a small scale subsurface layer (<20 μm). Mechanical behavior of this shallow layer is critical for component performance such as fatigue and wear. Due to the small size of this region, mechanical behavior of this shallow layer is hard to measure using traditional material testing. With the nanoindentation method, mechanical behavior (nanohardness and modulus) at the microscale in subsurface was measured for AISI 52100 and AISI 1070 steel components machined by hard turning, grinding, and honing. The test results show that white layer increases nanohardness but decreases modulus of a turned surface. Nanohardness and modulus of the ground surface are slightly smaller than the honed one in the subsurface. However, grinding produces higher nanohardness and modulus in near-surface (< 10 μm) than honing, while honing produces more uniform hardness and modulus in the near-surface and subsurface, and would improve component performance. Nanohardness and modulus of the machined near-surface are strongly influenced by strain hardening, residual stress, size-effect, and microstructure changes.