bluuebunny/crossref_metadata_2025 huggingface dataset:
Indices for Comparative Waste Assessment in Environmentally-Conscious Manufacturing
Authors: Sheng P. , Hertwich E.
Published: February 2008

With the expansion of pollution-prevention initiatives in the government sector, development of certification and eco-labeling mechanisms in foreign trade, and the emergence of “green” market drivers for consumer demand, industry is under increasing pressure to evaluate the “life-cycle” waste streams which emanate from their products and manufacturing processes. While much research has been devoted to the study of “system-level” design-for-environment (i.e. design for disassembly, serviceability, modularity), little attention has been given to the influence of planning and design decisions at the unit manufacturing process level, which has a significant impact on waste streams through material, catalyst, parameter and feature selection decisions. One of the most pressing issues in environmentally-conscious manufacturing is the ability to compare the environmental impacts of dissimilar waste streams to formulate the above decisions. This paper presents an overview of the hierarchical levels of comparative waste assessment which links process-level emissions to immediate, site-wide, and eco-system impacts. Significant issues to be addressed are: (1) the aggregation of data collection required for each level of decision-making, (2) the range of environmental effects needed to be analyzed at each level, (3) the uncertainty present at different levels of data aggregation, (4) the influence of site-specific (fate and transport) factors, and (5) the transformation of environmental information into metrics usable in detailed design and planning of products and processes. Case studies in the fabrication of metal parts and printed circuit boards are presented.
Accuracy and Time in Surface Measurement, Part 2: Optimal Sampling Sequence
Authors: Liang R. , Woo T. C. , Hsieh C-C.
Published: February 2008

While commonly practiced, the uniform and random distribution of sample points are shown to be far from optimal. This part of the paper presents a sequence for measurement and demonstrates by simulation that, for the same level of accuracy, a nearly quadratic reduction in the number of sample points can be achieved.
Constrained Cutting Rate-Tool Life Characteristic Curve, Part 1: Theory and General Case
Authors: Hough C. L. , Chang Y.
Published: February 2008

The concept of a cutting rate-tool life (R-T) characteristic curve is extended to the general machining economics problem (MEP) with a quadratic-logarithmic tool life and constraint equations. The R-T characteristic curve presents the general loci of optima, which is useful in selecting optimal parameters for multiple machining conditions. The necessary and sufficient conditions for the global optimum of the unconstrained MEP are presented. These conditions are equivalently applied to the concept of the constrained R-T characteristic curve. In terms of quadratic geometric programming the objective function and constraints of the general MEP are called as quadratic posylognomials (QPL). The QPL problems are classified as convex and nonconvex and the convexity is determined by the second order terms of the tool life model. Nonlinear programming and an exhaustive method are demonstrated to determine the R-T characteristic curve for three cases of posynomial, convex QPL, and non-convex QPL problems.
Using Wear Curves to Predict the Cost of Changes in Cutting Conditions
Authors: Chick S. , Mendel M. B.
Published: February 2008

A recently-proposed probability model for cutting tool lifetimes based on tool wear curves is presented. Optimal tool replacement strategies and cutting conditions are calculated using this wear-based model. The model’s use of wear curves permits extrapolation of cost calculations to cutting conditions for which little statistical data has been collected, assuming data is available for other cutting conditions which have the same failure mechanism. This is particularly important during process design changes, when data is expensive to obtain or limited in quantity. Analysis indicates that an important factor in tool replacement is run-in wear.
An Experimental Study of High Speed Orthogonal Cutting
Authors: Sutter G. , Molinari A. , Faure L. , Klepaczko J. R. , Dudzinski D.
Published: February 2008

A new high speed machining experiment is designed to obtain orthogonal cutting in a wide range of cutting speeds from 7 m/s to 100 m/s. Quasi-stationary cutting conditions are obtained. The measurement of the longitudinal cutting force reveals the existence of an optimal cutting speed for which the energy consumption is minimum. The genuine tool-workpiece material interaction can be analyzed with that experimental device.
Numerical Dynamic Analysis of Moving GTA Weld Pool
Authors: Cao Z. N. , Zhang Y. M. , Kovacevic R.
Published: February 2008

A three dimensional model with a moving heat source is developed to describe heat transfer and fluid flow in transient weld pools. Full penetration and free top and bottom surfaces are incorporated in the model in order to simulate the welding process more practically. The influence of plate thickness and welding current on the dynamics of weld pools is analyzed using calculated data. It is shown that when the workpiece is nearly penetrated, the depth of weld pool increases quickly. Also, the elevation of the top surface decreases quickly once the full penetration status is established.
Deformation Characteristics of Aluminum-Clad Stainless Steel Sheet Under Uniaxial Tension
Authors: Mori T. , Kurimoto S.
Published: February 2008

Clad sheets are now widely used in a wide variety of industrial practices, however, determination of deformation characteristics are difficult. In this research, the unique deformation characteristics and properties of aluminum-clad stainless steel sheets produced by hot rolling process are discussed. The tensile test and characteristics of necking appearing on the clad sheet and the separate materials composing the clad sheet are examined. The results of the experiments for the stress-strain curves of the separate materials compared well with the estimated values. The stress-strain relationship of the separate materials can thus be determined from the tensile test of clad sheet.
Analysis of End Milling Surface Error Considering Tool Compliance
Authors: Liang S. Y. , Zheng Li
Published: February 2008

An analytical model of surface height error in end milling due to the elastic compliance of cutting tool is presented. Based on the relationship of local cutting forces and chip thickness, the shear loading and bending moment on tool cross section are presented in terms of cutter angular position. The tool deflection responding to the bending moment is then established including the consideration of workpiece and machine tool structural deflection. The expression for surface error is derived as a closed-form function of the machining parameters, cutting configuration, material characteristics, and machine receptance.
Controlled-Depth Milling of Isogrid Structures With AWJs
Authors: Hashish M.
Published: February 2008

An experimental investigation was conducted to determine the feasibility of using abrasive-waterjets (AWJs) for controlled-depth milling of aluminum and titanium isogrid parts used in aerospace and aircraft structures. The effects of a wide range of milling parameters were studied. It was found that the traverse rate is the most critical parameter that affects the uniformity of the milled surfaces. Traverse rates on the order of several meters per second were found necessary to control the milling depth accuracy to within 0.025 mm. The problem of dynamically controlling the AWJ process parameters was negated by using a maskant material over the workpiece. The mask was AWJ-cut with the required pattern to be milled. The general topography of the milled surface was found to be more dependent on process kinematic parameters than AWJ process parameters, while surface morphology was found to be highly dependent on abrasive parameters. Milling to thin skins of 0.5 mm was demonstrated.
Closed-Die Forging of Gear-Like Elements
Authors: El-Domiaty A. , Shabara M. , Al-Ansary M.
Published: February 2008

Closed die forging of spur gears is investigated using the slab method and the upper bound technique. The tooth regions are approximated by prismatic rectangular sections. The velocity field comprising three unit deformation regions is used. A constant frictional stress between workpiece and forging die is assumed. The average punch pressure normalized by the flow stress of the gear material is determined theoretically and compared with experimental results. The experimental work is carried out on a commercial pure aluminum (Al 1100) at room temperature. The forging process is carried out using one die geometry without using any additional blocker (preform) dies. The theoretical predictions of forging pressures using slab and upper bound methods agree fairly well with the experimental results.
Analysis of Blade Forces and Wear in Diamond Stone Cutting
Authors: Webb S. W. , Jackson W. E.
Published: February 2008

The realtime evaluation of normal, tangential and perpendicular cutting forces and spindle vibration provides a simple measure of blade friction, wear performance, diamond-bond wear rate differences, blade stiffness and machine support. These observations can be used to evaluate and diagnose problems in diamond sawing that might inhibit use of high-grade diamond crystals.
An Efficient Way of Calculating Temperatures in the Strip Rolling Process
Authors: Chang Der-Form
Published: February 2008

The two-dimensional heat transfer between the strip and rolls in strip rolling is modeled by one-dimensional heat conduction equations adopting Lagrangian coordinate systems on the contact surfaces. Finite difference formulations are used in the rolling direction and analytical solutions are applied normal to this direction, making computation more efficient. Heat transfer in the sticking region is considered. The influence of real area of contact on heat transfer is also taken into account, resulting in a method capable of modeling the strip rolling process operated in any of several different lubrication regimes. This method provides good temperature predictions.
Milling Process Simulation—A Generic Solid Modeller Based Paradigm
Authors: Mounayri H. El , Spence A. D. , Elbestawi M. A.
Published: February 2008

A generic solid modeller based milling process simulation system is developed for 3-axis milling of complex parts. Parts are described using a boundary representation solid model, and cutting edges are fitted with cubic Be´zier curves. For every completed tool path (i.e., one NC block), the tool swept volume is generated and intersected with the part, yielding the corresponding removed material volume. The tool cutting edges are then intersected with that volume to produce the tool-part immersion geometry. The mechanistic milling process model produces an accurate simulation of cutting forces, torque and power. Modelling of tool and tool holder dynamics is included. The system is based on a generic procedure for extracting geometric data required to accurately simulate milling of complex parts. Any tool shape can be represented, and extension to 4- and 5-axis machining is straightforward. Related processes such as turning and drilling can be modelled in a similar way. The capability of the system is demonstrated experimentally for ball end milling.
An Improved Numerical Modeling for Resistance Spot Welding Process and Its Experimental Verification
Authors: Gupta O. P. , De Amitava
Published: February 2008

A numerical model of resistance spot welding with spherical tip electrode is developed to incorporate the electro-thermal aspect as well as thermo-elasto-plastic behaviour inherent in this process. The electro-thermal aspect includes the Joule’s resistive heating along the contact surfaces and within the sheet-electrode system due to nonuniform current density distribution in the sheet-electrode. The elasto-plastic deformation of the sheet-electrode interface at higher temperature is included in the thermo-mechanical analysis. The interdependence of those two analyses has been taken care of The model is used to simulate the spot welding in low-carbon steel sheets of 1 mm and 2 mm thickness and HSLA steel sheet of 1 mm thickness. The results are compared with experimental data obtained as a part of this work and also with literature data. The comparison has shown a good agreement in all the cases. The results are later used to draw the thermal cycle curves at different location along the faying surface.
Angle Domain Analytical Model for End Milling Forces
Authors: Zheng Li , Liang Steven Y. , Melkote Shreyes N.
Published: February 2008

This paper presents the development of an explicit expression of cutting force wave forms in end milling with helical multi-flute cutters. From the relationship of elemental cutting forces and chip load, the net cutting forces are analytically formulated based on the integration of elemental cutting forces in the feed, cross feed, and axial directions. This formulation leads to a solution of force waveforms as algebraic functions of tool geometry, machining parameters, cutting configuration, and work piece material properties. The closed-form nature of the resulting model facilitates force estimation and process optimization without resorting to numerical iterations. The theoretical error of prediction due to the truncation of higher frequency terms is analyzed. It provides a guideline for choosing the model size for given error tolerance. It also offers an understanding of upper bound of prediction error for a known number of approximating terms used in the model. In the paper end milling experimental results were examined over a range of conditions to verify the analytical model in the context of waveform, power spectrum, and model size effect.
Acoustic Emission Characteristics of Abrasive Flow Machining
Authors: Williams R. E.
Published: February 2008

Abrasive Flow Machining (AFM) is a nontraditional finishing process that deburrs and polishes by forcing an abrasive-laden viscoelastic polymer across the workpiece surface. Current applications include improvement in air and fluid flow for cylinder heads, intake manifold runners and injector nozzles. Present manufacturing methods include a series of flow test and AFM operations which require significant material handling and operator adjustment. An effective on-line monitoring and adaptive control system for AFM is needed. This paper reports on the development of an acoustic emission (AE) based monitoring strategy and the AE characteristics of abrasive flow machining. Initial results showed AE to be a viable sensing method for determining the performance characteristics of AFM for simple extrusion passage geometries in a selected part design. The root mean square (RMS) voltage of the AE signal was mainly determined by the metal removal and related AFM process parameters. Frequency decomposition of the AE signals revealed distinct frequency bands which have been related to the different material removal modes in AFM and to the workpiece material. Research was also performed on the application of AFM to finish orifices of varying sizes. Extremely high correlations were found between the AE signal and both the orifice diameter and the volumetric flow rate. Work is continuing with the equipment manufacturer and key industrial users to apply the monitoring strategy as part of a prototype Flow Control AFM.
Thermal and Design Sensitivity Analyses for Cooling System of Injection Mold, Part 2: Design Sensitivity Analysis
Authors: Park S. J. , Kwon T. H.
Published: February 2008

DSA will ultimately play an important role in the design optimization process. Part 2 of this paper presents an efficient and accurate methodology for the DSA of the cooling stage of the injection molding process. The DSA program developed in the present study utilizes the implicit differentiation of the boundary integral equations and the B.C.s presented in Part I with respect to all DVs to yield the sensitivity equations. In this DSA, we have considered various DVs as follows: (i) (DVs related to processing conditions) inlet coolant bulk temperature and inlet coolant volumetric flow rate of each cooling channel inlet, and (ii) (DVs related to mold cooling system design) radius and location of each cooling channel. Two sample problems are solved to demonstrate the accuracy and efficiency of the present DSA formulation and to discuss the characteristics of each DV.
Incremental Formulation for the Prediction of Flow Stress and Microstructural Change in Hot Forming
Authors: Yanagimoto J. , Karhausen K. , Brand A. J. , Kopp R.
Published: February 2008

In metal forming, the workpieces are formed to the desired shapes or profiles. Especially in hot forming, the microstructure of workpiece changes during plastic deformation. Modern forming technologies allow to control the shape and the microstructure of formed product in a wide range and will gain increasing importance in future in the field of metal forming. In order to develop this forming technology which may be called “macroscopic microscopic materials processing”, theoretical predictions of plastic deformation as well as microstructural changes are indispensable. A new mathematical formulation to predict flow stress and microstructural change in hot forming will be presented in this paper. This model is based on an incremental formulation taking the dislocation density as a representative variable.
Chatter in the Strip Rolling Process, Part 1: Dynamic Model of Rolling
Authors: Yun I-S. , Wilson W. R. D. , Ehmann K. F.
Published: February 2008

This paper presents the development of a new dynamic model of the rolling process which provides estimates of the variations in exit gage, strip speed and tension at entry and exit, rolling force and rolling torque in response to variations in roll separation as well as the rate of change of the roll spacing. This two-dimensional dynamic model employs the Tresca friction factor approach instead of Amontons-Coulomb friction law.
A Fiber Optic Sensor for Surface Roughness Measurement
Authors: Bradley C. , Bohlmann J. , Kurada S.
Published: February 2008

A fiber optical interferometer system is described for non-contact measurement of surface topography. The system employs a fiber optic guide and lens arrangement that forms an interferometric cavity between the lens front face and the test surface. Changes in the surface topography are manifested as phase changes between the light reflected from the surface and the front face of the lens. An electronic control and data acquisition system converts the phase change into a voltage signal proportional to surface height. The system is calibrated and compared with stylus surface profile measurements performed on a standard set of machined surface samples. Comparison of the amplitude parameter, Ra, shows differences of between 17 percent and 34 percent across the set of samples, whereas, two spatial parameters, frequency and peak count, consistently compare within 1 percent to 12 percent throughout the Ra range: 0.42 μm ≤ Ra ≤ 2.89 μm.
Finishing of Silicon Nitride Balls for High-Speed Bearing Applications
Authors: Raghunandan M. , Komanduri R.
Published: February 2008

A batch of 12, HIP’ed silicon nitride (Si3N4) balls (NBD 200 from CERBEC) of 13.4 mm nominal diameter were finished by magnetic float polishing (MFP) process. These balls contained a large rim of material (about 200 μm thick × 5 mm wide) around the periphery at the parting line originating from the HIP’ing process. The finishing process consisted of three stages–1. semi-finishing using a 17 μm B4C abrasive at 4000 rpm spindle speed to remove the rim on the Si3N4 balls, 2. intermediate finishing using a 17 μm B4C abrasive at 2000 rpm spindle speed to reduce the diameter and the sphericity, and, 3. final finishing stage using a 3 μm SiC abrasive, followed by 1 μm SiC and 1–5 μm Cr2O3. The balls were finished to a final diameter of 12.7 mm with an average sphericity of 1.3 μm (0.5–2.0 μm) and an average surface finish, Ra, of 24.6 nm (16.6–39.8 nm). The total time for finishing was about 21 hours. This, however, included an intermediate stage of finishing with Cr2O3 in order to address some problems experienced earlier in attempting to obtain good finish. As this stage is not required under normal circumstances, some 4-1/2 hours of polishing time can be saved resulting in total polishing time of about 16-1/2 hours. This time should be compared to some 4–6 weeks required for conventional grinding and lapping of ceramic balls. The technology is easy to implement in the manufacturing shop floor requiring very little capital investment.
Dynamics of Spindle-Bearing Systems at High Speeds Including Cutting Load Effects
Authors: Jorgensen Bert R. , Shin Yung C.
Published: February 2008

Increased use of high speed machining creates the need to predict spindle-bearing performance at high speeds. Previous spindle-bearing models simplify either spindle or bearing dynamics to the extent of prohibiting a detailed analysis of a spindle with high speed motion. At high speeds, centrifugal loading in the bearing causes stiffness softening, creating a change in natural frequency. Therefore, spindle modeling requires a comprehensive representation of the dynamics of shafts with complex geometry rotating at high speeds and supported by non-linear bearings. This paper presents a coupled system of spindle and bearing dynamic models with numerical solution. Spindle dynamics are modeled using the influence coefficient method of discrete lumped masses, based on Timoshenko beam theory. Both linear and rotational bearing stiffness are included in the spindle model through solution of the angular-contact bearing model. The parameters of cutting loads, tool mass, and rotational speed are analyzed, and all are shown to affect the natural frequency. The computer model is both rapid and robust, and shows excellent agreement with experimental analysis.
Experimental Investigation of the Influence of Machining Condition on the Contact Sliding Behavior of Metals
Authors: Kim Dae-Eun , Hwang Dong-Hwan
Published: February 2008

In many instances machined parts experience sliding motion while in contact with a counter surface. The performance of the contacting parts depends on their friction and wear characteristics. In this work the effects of the machining condition on the tribological performance of steel, brass, and duralumin are investigated. For steel, it is shown that the friction coefficient value remains about the same whereas the rate of wear varies as the cutting condition is altered. The friction coefficients for brass and duralumin were lower than that of steel and their tribological properties seem to be less sensitive to the machining condition. In conclusion, it is emphasized that the machining condition directly influences the surface integrity which in turn affects the tribological performance of the machined parts, and therefore, the machining condition for parts that experience contact sliding motion should be optimized for best tribological performance in addition to dimensional accuracy and surface roughness.
Open Architecture Controllers for Machine Tools, Part 1: Design Principles
Authors: Schofield S. , Wright P.
Published: February 2008

In Part 1 of this two-part paper, we review the development of open architecture controllers for machine tools. General design principles are described, followed by specific hardware and, software recommendations. These specific recommendations are then used for the construction of an open architecture device, MOSAIC-PM, (Machine tool Open System Advanced Intelligent Controller for Precision Machining). The machine has now been used in a wide variety of experiments to demonstrate open architecture control. These experiments include sensor based machining, rapid prototyping and manufacturing over the Internet. In Part 1, a specific application on feature based precision machining with on-machine acceptance is described. A more specific implementation of a quintic spline interpolation method is described in Part 2.
Open Architecture Controllers for Machine Tools, Part 2: A Real Time Quintic Spline Interpolator
Authors: Wang Fu-Chung , Wright P. K.
Published: February 2008

In Part 2 of this two-part paper, we describe a new quintic spline interpolator for real time trajectory generation during free form curve machining on the Open Architecture machine tool platform described in Part I. The research provides new capabilities for advanced CAD/CAM systems. Complicated curves and shapes designed in a CAD system are usually represented by a set of discrete data points. Subsequently, for manufacturing by a CAM system, these data points need to be converted into tool paths for machining. Therefore, the paper presents a new interpolation method that interpolates the designated data points with a quintic spline curve for real-time tool path generation. The resultant curve, generated by the proposed interpolation method, is nearly arc-length parametrized and has C3 continuity. The near arc-length parametrization property makes the real time generation of the reference commands of the cutting tool path easier. The C3 continuity guarantees the smooth motion of continuous speed, acceleration and even jerk during the machining. The combined properties of this new interpolation method enable a new quintic spline interpolator to be developed for real time tool path generation.
Adaptive Optimization of Face Milling Operations Using Neural Networks
Authors: Ko Tae Jo , Cho Dong Woo
Published: February 2008

In intelligent machine tools, a computer based control system, which can adapt the machining parameters in an optimal fashion based on sensor measurements of the machining process, should be incorporated. In this paper, the method for adaptive optimization of the cutting conditions in a face milling operation for maximizing the material removal rate is proposed. The optimization procedure described uses an exterior penalty function method in conjunction with a multilayered neural network. Two neural networks are introduced: one for estimating tool wear length, and the other for mapping input and output relations from the experimental data during cutting. The adaptive optimization of the cutting conditions is then implemented using the tool wear information and predicted process output. The results are demonstrated with respect to each level of machining such as rough, fine, and finish cutting.
A General Formulation for Hydroforming of Arbitrarily-Shaped Boxes and Its Application to Hydroforming of an Elliptic-Circular Box
Authors: Noh T. S. , Yang D. Y.
Published: February 2008

A general kinematically admissible velocity field is suggested for the upper-bound solution of hydroforming of arbitrarily-shaped boxes. The suggested formulation is then applied to hydroforming of an elliptic-circular box. From the proposed velocity field, the fluid pressure vs. punch stroke relationship to render uniform thickness and the deformed configuration are determined by minimizing the total power consumption with respect to some chosen parameters. Experiments are carried out in the hydroforming press according to the computed pressure vs. punch stroke curve. The assumption of uniform wall thickness is confirmed by measuring the thickness variation. The effects of various process parameters including blank size, work-hardening exponent and frictional coefficient on the pressure curve are analyzed and discussed. It is thus shown that the proposed method of analysis in the present study can be effectively used for hydroforming of arbitrarily shaped boxes.
A Solidification Front Monitor for Metal Casting
Authors: Hytros M. M. , Chun J.-H. , Lanza R. C. , Saka N.
Published: February 2008

A feasibility study was performed to assess computed tomography (CT) as a method of detecting the position of the solidification front during metal casting. Since the liquid and solid phases of metals differ in density by 4 to 12 percent, CT has the ability to differentiate the two phases. The motivation for this work is the development of a real-time solidification sensor for the continuous casting of metals. A first-generation CT system for reconstructing two-dimensional images of solidifying tin was developed. The performance of the CT system was evaluated by reconstructing images of objects of known geometries. For the solidification experiment, CT scans were conducted on an actively heated and cooled crucible filled with pure tin. The tin existed in both liquid and solid phases, with the solidification front position tracked by thermocouples. The image of the two-phase tin experiment had poor contrast resolution, but a quantitative analysis of the image does indicate an approximate 7 percent difference between the liquid and the solid portions of the melt. However, the size of the liquid phase was not as large as that determined by thermocouple measurements. This is a result of temperature fluctuations in the melt during data acquisition, as well as the relatively low spatial resolution. Future work to improve system performance will include using a linear accelerator (linac) as the radiation source.
A Robust Pretravel Model for Touch Trigger Probes in Coordinate Metrology
Authors: Shen Y. , Springer M. E.
Published: February 2008

This paper describes a pretravel model for vertically-oriented touch trigger probes with straight styli widely used on coordinate measuring machines (CMMs). Advances in machine accuracy and tighter part tolerances leave probe error as one of the major error sources in dimensional measurement processes. Pretravel accounts for the majority of touch trigger probe errors and is caused by bending deflection of the probe stylus shaft. A trigger force model was first derived and used to model the probing force at the trigger instant. Experimental probing force data were used to validate the trigger force model. The trigger force model was then used to model the bending deflection of the stylus shaft at the trigger instant. Experimental x-y-z coordinate data were used to validate the pretravel model. It is shown that 24 points of equatorial data measured in the probe calibration process can be used to accurately identify the only model parameter. Also, 12 points of equatorial data provides reasonably good results. Model predicted pretravels associated with 1561 probe approach directions were compared with experimental pretravels (range: 16 μm, when using a 50 mm stylus) and the standard deviation of prediction errors can be reduced to around 0.6 μm.
Reducing Cutting Force Induced Bore Cylindricity Errors by Learning Control and Variable Depth of Cut Machining
Authors: Hanson R. D. , Tsao Tsu-Chin
Published: February 2008

In this paper, a method for on-line compensation of cylindricity errors in machined bores is formulated and demonstrated. The cylindricity errors addressed are those caused by the elastic deformation of the bore wall due to forces applied to the workpiece both during and after the machining process. Compensation is achieved using a piezoelectric boring bar servo capable of varying the depth of cut rapidly for on-line compensation at acceptable industrial machining speeds. Control of the boring bar servo consists of both learning and repetitive control. Learning control is used to determine the cutting tool reference trajectory required to achieve compensation, and repetitive servo control is used to accurately track the reference trajectory. The stability and convergence of the error dynamics of the learning control system are analyzed using a model for the flexure-induced machining errors. Experimental results demonstrate that the proposed method can significantly improve bore cylindricity in machined components.
Modelling, Identification and Control of Thermal Deformation of Machine Tool Structures, Part 1: Concept of Generalized Modelling
Authors: Fraser S. , Attia M. H. , Osman M. O. M.
Published: February 2008

With the increasing demand for improved machining accuracy in recent years, the problem of thermal deformation of machine tool structures is becoming more critical than ever. In spite of the effort for improving the thermal deformation characteristics of machine tools at the design stage, there are always some residual errors that have to be compensated for during machining. The design of a generic multi-axis control system requires the development of two models to estimate the transient thermal load and to estimate the thermal deformation of the structure in real-time. To satisfy the stringent accuracy and stability requirements of these two models, a new concept of “generalized modelling” is introduced. It combines mathematical modelling with empirical calibration, and is based on the existence of a mathematical similarity between the real process and a simplified model, referred to as the fundamental generalized problem FGP. To obtain an analytical description of the heat transfer and thermal deformation processes in machine tool structures, an analytical solution of the FGP, which consists of an infinite plate with a central ring heat source, is derived using Hankel transformation. Computer-simulated test cases are presented to demonstrate the use of generalized modelling for predicting the transient thermal response in a complex machine tool structure. It was also shown how the generalized model can accurately extrapolate limited measurement data to predict the entire temperature field. The results confirmed that the generalized model can reproduce the accuracy of the finite-element solution, but two orders of magnitude faster.
Modelling, Identification and Control of Thermal Deformation of Machine Tool Structures, Part 2: Generalized Transfer Functions
Authors: Fraser S. , Attia M. H. , Osman M. O. M.
Published: February 2008

With the ever increasing demand for higher machining accuracy at lower cost, thermal deformation of machine tool structures has to be minimized at the design stage, and compensated for during operation. To compensate for this type of error, two real-time process models are required to identify the magnitude of the transient thermal load and to estimate the relative thermal displacement between the tool and the work piece. Special considerations should be given to the solution of the first ill-posed inverse heat conduction model IHCP. In this paper, the concept of generalized modelling is extended to the thermal deformation problem. The results of this analysis is used to develop expressions for the generalized transfer functions of the thermal, and thermal deformation response of the machine tool structure. These transfer functions are the basic building blocks for real-time solution of the IHCP and then the deformation problem. The latter acts as a feed-back signal to the control system. Finite element simulation of the temperature field and the thermal deformation of a machine tool structure confirmed that the generalized transfer function approach can reproduce the accuracy of the finite element model but two orders of magnitude faster.
The Kinematic Synthesis of Toggle Clamps
Authors: Tso Pei-Lum
Published: February 2008

The toggle clamp is one of the most common forms of clamps used throughout industry. They are commercially available in different types and models satisfying almost all ordinary fixture clamping requirements. Based on the theorem of implicit function system existence and the concept of solution plane, computers have been employed to generate planar four-bar mechanisms for three position function generation problem at the toggle positions. A quadratic equation which defines the locus can be plotted in the plane of solutions which have toggle at first, second, or third positions. Additionally this approach offers control over the mechanical advantage at clamping position, and defect free solutions. A vertical acting toggle clamp has been worked for illustrative purposes. This methodology has also been applied to generate slider-crank at toggle position for push-pull type toggle clamps.
Tool Wear in Milling Hardened Die Steel
Authors: Nelson S. , Schueller J. K. , Tlusty J.
Published: February 2008

Tool wear is an important limiting factor in machining hardened steel. Plane milling of H13 hot work tool steel (42–46 HRC) was conducted on a three-axis machine to obtain flank wear data with the objective of finding operating parameters providing extended tool life. Microgram carbide and PCBN tipped carbide round inserts in an off-center ball nose end mill with a single cutting edge were considered. Tool life was longer for the micrograin carbide inserts when cutting speeds were near 150 m/min. The PCBN grades performed best at the highest speed tested. A limited radial and axial depth of cut with a larger maximum chip thickness provided the best tool life over the parameters tested.
Basic LOgical Bulk Shapes (BLOBs) for Finite Element Hexahedral Mesh Generation to Support Virtual Prototyping
Authors: Liu S.-S. , Gadh R.
Published: February 2008

Manufacturability analysis of product design reduces the downstream problems of manufacturing. Such design approaches are referred to as Virtual Prototyping when performed on the computer. In the present research, Virtual Prototyping is facilitated by the use of an automated method of determining the finite element meshes needed to perform finite element analyses. Finite element analysis requires a finite element mesh of the product model as input. This mesh (an approximation of an object’s geometry and topology, composed in terms of a given individual unit, e.g., a tetrahedron, or a hexahedron), can be generated using a variety of methods. The research presented here offers an approach for automatic mesh generation that addresses some of the limitations in the mesh-generation technologies currently available. This article presents an approach for automatically generating hexahedral meshes from solid models. The mesh generating method presented in this paper involves four major steps. First, objects called Basic LOgical Bulk shapes (BLOBs) are determined from the solid model of a given part. Second, these BLOBs are used to decompose the solid model into its various sub-volumes. Third, a multiple-block structure (MBS), which is a group of hexahedral objects, is constructed to approximate the solid model. Finally, transfinite mapping is employed to project the faces of the MBS onto the surfaces of a model to generate the finite element meshes.
Accuracy Analysis of Point Laser Triangulation Probes Using Simulation
Authors: Smith K. B. , Zheng Y. F.
Published: February 2008

Point Laser Triangulation (PLT) probes are relatively new noncontact probes being integrated with Coordinate Measuring Machines (CMMs). Two prominent advantages of PLT probes are fast measuring speeds (typically 100 to 1000 times faster than touch probes) and no contact force is required to take measurements making soft or fragile objects measurable. These advantages have motivated the integration of PLT probes onto CMM. However, because the PLT probe is an electro-optics device, many factors related to optics affect its operation, such as sensor-to-surface orientation and surface reflectivity. To study and better understand these error sources, PLT probe models are needed to simulate observed measurement errors. This article presents a new PLT probe model, which simulates observed measurement errors and shows the effects of placement and orientation of internal components. This PLT probe model is a combination of internal component models developed using geometrical optics. The model successfully simulates measurement errors from specular reflection observed experimentally with real PLT probes. The model also allows the parameters of internal components to be studied.
Thermal Stress Development During Vacuum Arc Remelting and Permanent Mold Casting of Ingots
Authors: Alam M. K. , Semiatin S. L. , Ali Z.
Published: February 2008

The development of thermal stresses in ingots during the vacuum arc remelting (VAR) as well as specialized permanent mold casting (PMC) process was modeled via numerical solution of the two-dimensional, nonsteady-state heat conduction and stress equilibrium equations. The numerical analysis was carried out in conjunction with experimental studies of the mechanical properties and microstructure of a cracked VAR titanium aluminide ingot. Numerical solutions were obtained for different values of ingot diameter, crucible-ingot interface heat transfer coefficients, and lengths of the melted-and-resolidified ingot. For both VAR and PMC, model predictions revealed that the maximum tensile thermal stresses are developed at the bottom of the ingot; the magnitude of such stresses increases with ingot diameter and the magnitude of the interface heat transfer coefficients. The microstructural analysis of a cracked ingot indicated that the thermal cracking occurred in the temperature range where the alloy has very little ductility. The predicted development of large tensile stresses correlates well with observations of thermal cracking during VAR of near-gamma titanium aluminide alloy ingots. By contrast, the predicted thermal stresses developed during PMC are lower, thus suggesting an attractive alternative to VAR to obtain sound, crack-free ingots.
Multi-Category Classification of Tool Conditions Using Wavelet Packets and ART2 Network
Authors: Niu Y. M. , Wong Y. S. , Hong G. S. , Liu T. I.
Published: February 2008

This paper proposes a new approach for multi-category identification of turning tool conditions. It uses the time-frequency feature information of the AE signal obtained from best-basis wavelet packet analysis. By applying the philosophy of divide-and-conquer and a local wavelet packet extraction technique, acoustic emission (AE) signals from turning process have been separated into transient and continuous components. The transient and continuous AE components are used respectively for transient tool conditions and tool wear identification. For transient tool condition identification, a 16-element feature vector derived from the frequency band value of wavelet packet coefficients in the time-frequency phase plane is used to identify tool fracture, chipping and chip breakage through an ART2 network. To identify tool wear status, spectral and statistical analysis techniques have been employed to extract three primary features: the frequency band power at 300 kHz–600 kHz, the skew and kurtosis. The mean and standard deviation within a moving window of the primary features are then computed to give three secondary features. The six features form the inputs to an ART2 neural network to identify fresh and worn state of the tool. Cutting experimental results have shown that this approach is highly successful in identifying both the transient and progressive tool wear states over a wide range of turning conditions.
Sensor Optimization for Fault Diagnosis in Single Fixture Systems: A Methodology
Authors: Khan A. , Ceglarek D. , Shi J. , Ni J. , Woo T. C.
Published: February 2008

Fixture fault diagnosis is a critical component of currently evolving techniques aimed at manufacturing variation reduction. The impact of sensor location on the effectiveness of fault-type discrimination in such diagnostic procedures is significant. This paper proposes a methodology for achieving optimal fault-type discrimination through an optimized configuration of defined “sensor locales.” The optimization is presented in the context of autobody fixturing—a predominant cause of process variability in automobile assembly. The evaluation criterion for optimization is an improvement in the ability to provide consistency of best match, in a pattern recognition sense, of any fixture error to a classified, anticipated error set. The proposed analytical methodology is novel in addressing optimization by incorporating fixture design specifications in sensor locale planning—constituting a Design for Fault Detectability approach. Examples of the locale planning for a single fixture sensor layout and an application to an industrial fixture configuration are presented to illustrate the proposed methodology.
Neural Adaptive Control for Positioning Fabric on a Frictional Surface
Authors: Shenoy S. M. , Rahn C. D.
Published: February 2008

This research focuses on real-time position control for draping fabric sliding on a high friction surface. Although fabrics are usually positioned on smooth surfaces with fixed fabric guides to simplify automated handling, a high friction work surface holds the fabric in place after positioning, allowing accurate assembly of multiple fabric parts without specialized jigs or fixtures. A neural adaptive controller with feedforward friction compensation provides asymptotic tracking for a spring mass model with friction. A test stand and an optical sensor are designed to facilitate real time position measurement and control. The neural adaptive controller demonstrates good position tracking and robustness to fabric property variations relative to open loop or PID control.
Non-Free Cutting and Its Degree of Freedom Confinement
Authors: Shi H. , Wang X. , Lu Tao
Published: February 2008

Plunge-turning processes of round-edged cutters is analyzed and its cutting force modeled in the light of a general theory of non-free cutting developed by the authors. In this study the whole cutting tool is treated as a combination of a series of Elementary Cutting Tools (ECTs). Due to the non-linearity of chip-ejection interference among all the ECTs the total cutting force of the whole cutter, however, cannot be calculated by simply superposing the incremental cutting forces generated by all the ECTs. A Non-Linear Synthesis Method (NLSM) is therefore suggested for modeling this non-free cutting force. The main feature of the method is that the chip-ejection interference is under consideration and modeled on the basis of the Principle of Minimum Energy (PME). Good agreement between the predicted and measured main cutting forces is identified. Furthermore, a Coefficient of Non-Free Cutting (CNFC) is applied to quantitatively indicate the strength of chip-ejection interference among the ECTs and the degree of freedom confinement of the cutting process.
Fixed-Load Electrolytic Dressing With Bronze Bonded Grinding Wheels
Authors: Bifano T. , Krishnamoorthy R. , Fawcett H. , Welch E.
Published: February 2008

In electrolytic in-process dressing (ELID), a metal-bonded grinding wheel is dressed as a result of anodic dissolution. In this paper we describe experiments to evaluate the potential for ELID on bronze wheels in fixed-load grinding applications. A constant-force grinding apparatus was used to determine appropriate ELID conditions for a 10–20 μm bronze bonded diamond grinding wheel used to machine silicon carbide. A practical implementation of ELID was demonstrated using a low speed bronze bonded diamond wafering saw. Optimum ELID current was determine for different workpiece materials, and the wear rate of the saw blade using ELID was found to be of the same order as the wear rate of the saw blade using intermittent dressing with a porous ceramic stick. Some of the important factors controlling the rate of dressing by ELID (rate of film growth, rate of film wear and rate of diamond wear) and their combined effects are discussed. Successful use of ELID on bronzebonded wheels in other applications will be facilitated by understanding these phenomena, developing a general process model based on them and being able to predict useful ELID parameters.