Shape Of Workpiece Research Articles

Active Compliant Motion Control for Grinding Robot

A grinding robot system is presented in this paper. Active compliant motion control is applied to keep contacting between grinding tool and work pieces and auto surface tracking algorithm was developed to trace the outline of work-pieces. For real implementation of the system, the shape of work pieces are informed through barcode and the piece's dimension is measured with a laser distance sensor. Experimental results with the implemented system are also presented and discussions for further works are followed.

D26 マルチワイヤソーによって切断される工作物の形状と加工溝内部のスラリー挙動の関係(OS-7 研削・砥粒加工(1))

D26 マルチワイヤソーによって切断される工作物の形状と加工溝内部のスラリー挙動の関係(OS-7 研削・砥粒加工(1))

Accurate Estimation Method of Intersection Coordinate between View Lines and Curved Surface Using Graphics Hardware

This paper deals with a new calculation algorithm of Z-map representation with graphics hardware to perform geometric simulation of NC machining process. Graphics hardware (GPU) is a device designed to render 3D computer graphics. In previous studies, it is proposed that shape of machined workpiece is estimated by referring depth information on rendered image by GPU. However, such depth information usually contains calculation error that cannot be corrected, because GPU cannot deal with curved surface directly and requires approximation to a polyhedron. In this paper, a new geometric calculation method based on GPU functions is proposed in order to estimate accurate depth information from rendering process. In the proposed method, pixel shader in GPU estimates a distance between the curved surface and the approximated polyhedron in modeling coordinate system and corrects the depth information on frame buffers.

B06 円筒面のボールエンドミル加工に関する研究 : 加工誤差に及ぼす被削材形状の影響(OS-6 切削加工(1))

Ball end milling is widely used in the manufacturing process of sculptured surface. In order to achieve high productivity and high accuracy with low costs, it is necessary to know the cutting properties before manufacturing. This research makes an effort on finding out the influence of shape of workpiece on machining error in ball end milling of cylindrical surface. At first, the machining errors in ball end milling of convex and concave cylindrical surfaces are analyzed theoretically, respectively. Secondly, the experiments are carried out to verify the theoretical results. At last, the appropriate cutting conditions are discussed basing on the calculated and measured values.

Alternate methods for sampling in coordinate metrology

A variety of inspection equipment exists in industry to capture the points on a surface that will envisage manufacturing form errors. Manufacturing inspection faces a problem of finding optimal methods to capture an evenly spread distribution of points on the surface. Sampling does not yield complete information about a surface. Each material removal process leaves a unique pattern on the surface of the workpiece, which has to be taken into consideration while developing the sampling strategy. For instance, round patterns left by face milling at low feeds on flat surfaces, and spiral patterns left during surface milling and turning operations on surfaces of revolution. Two new methods have been developed to improve sampling using the coordinate measuring machine (CMM) for inspection of flat and revolved surfaces. These are the Spiral, and Hamspi sampling methods. The Spiral method focuses on the centre of the area and uses the Archimedean spiral. Hamspi is a method that combines both the Spiral and randomized Hammersley to measure points in the middle as well as the outer zone of the workpiece. Mathematical comparisons of these methods have been made to establish feasibility. An experiment was performed to determine the accuracy of these models using two dependent variables: inspection time and minimum zone. The minimum zone was (statistically) significantly affected by only two factors: sample size and workpiece shape. The sampling time was however affected by sample size, workpiece shape, and the interaction between them. This study observed that the beginning and ending cutting zones of spherical surfaces were the most significant regions to verify. It was found that the Spiral and Hamspi methods had similar point distributions as the Hammersley method while placing more emphasis on the origin of the workpiece.

Analysis and design optimization of deep drawing process: Part II: Optimization

In part I of the present work [H. Sattari, R. Ganesan, R. Sedaghati, Analysis and design optimization of deep drawing process. Part 1: Three dimensional finite element and sensitivity analysis, J. Mater. Process. Technol., submitted for publication], a finite element formulation based on a combined Total and Updated Lagrangian approach (TUL) has been developed to calculate the sensitivities in the large elasto-plastic strains in sheet metal forming parts obtained by deep drawing. The present part II deals with the use of multiplicative decomposition of the TUL to improve the efficiency in the analysis and optimum design of blank contours of complicated parts. The TUL exploits the knowledge of the 3D shape of the final workpiece. An iterative scheme is developed to find the original position of each material point in the initial flat blank after which it is possible to estimate the strains and stresses in the final workpiece. The von Mises plasticity is adopted regarding the constitutive equations. In the present work, several developments have been presented: (1) the bending effects are taken into account using shell elements without increasing the number of degrees of freedom per node. (2) Appropriate improvements of resolution algorithms such as the introduction of a relaxation coefficient, a damping factor and a good initial solution are realized. (3) Shape optimization of blank contours is performed using a numerical procedure based on the coupling of the TUL and the sequential quadratic programming method (SQP). The numerical results obtained using the Lagrangian approaches for the benchmark test are compared with existing experimental and numerical results. The optimization procedure is applied to shape optimization of a square blank which is used to produce a cup in deep drawing process. The objective function is defined to minimize the thickness variations.

High Speed Lapping Ellipsoid by Means of a Lapping Tool Bending Method

This paper discusses a new lapping ellipsoid method, which combines high-speed lapping technology with solid abrasives and lapping tool bending method. In this method, a bending moment is acted on lapping tool with solid abrasives, which makes it bend to form a shape on its working surface, which is the same as generant of workpiece shape. This kind tool is used in forming lapping on a high speed lapping machine. With the development of science and technology, the requirements for optics systems become higher and higher, e.g. good quality of imaging, little loss light energy, small size and light weight etc. It is difficult to reach above requirements by using traditional sphere lens/mirrors in optics systems. Aspheric optics elements can be used to solve these problems. In optics systems, by using aspheric optics elements, the number of optics elements can be reduced, the system structure can be simplified, the weight and size of the system can be reduced, light energy loss can be reduced too, imaging errors can be avoided and imaging quality can be improved. Ellipsoid is a kind of surface being used widely within all kinds of aspheric surfaces. The main purpose of this paper is to introduce a method of lapping this kind of surface at high speed.

3축 그라인딩 로봇을 이용한 자동 경로 생성 및 능동 컴플라이언스 힘 제어

In this paper, an auto path generation and an active compliance grinding control using 3-axis farce sensor are presented. These control algorithms enable the grinding robot to follow unknown path of various workpiece shape pattern. The robot is able to go grinding along unknown paths by position controller managing tangential direction angle and cutting speed, with only information about the start position and the end position. Magnitude and direction of normal force are calculated using force data that go through low pass filter. Moreover, normal and tangential directions are separated for force control and velocity control, respectively.

Modeling of the Semi-Solid Material Behavior and Analysis of Micro-/Mesoscale Feature Forming

One of the major challenges in simulation of semi-solid forming is characterizing the complex behavior of a material that consists of both solid and liquid phases. In this study, a material model for an A356 alloy in a semi-solid state has been developed for high solid fractions (>0.6) and implemented into a finite element simulation tool to investigate the micro-/mesoscale feature formation during the forming process. Compared to previous stress models, which are limited to expressing the stress dependency on only the strain rate and the temperature (or the solid fraction), the proposed stress model adds the capability of describing the semi-solid material behavior in terms of strain and structural evolution. The proposed stress model was able to explain the strain-softening behavior of the semi-solid material. Furthermore, a simulation model that includes the yield function, the flow rule, and the stress model has been developed and utilized to investigate the effects of various process parameters, including analysis type (isothermal vs nonisothermal), punch velocity, initial solid fraction, and workpiece shape (“flat” versus “tall”) on the micro-/mesofeature formation process.

An Experimental Investigation on Semi-Solid Forming of Micro/Meso-Scale Features

The potentials of semi-solid forming technology have generated much interest regarding its application in micromanufacturing. This study investigates the feasibility of using semi-solid forming technology to produce parts with micro/meso features. An experimental setup has been developed to study the effects of die/punch temperature, initial solid fraction, punch speed, and workpiece shape on the semi-solid forming process. A part has been produced for a microreactor application and has been analyzed with an optical measurement system for feature formation. The results indicated complex interaction among the process parameters and the material flow, which affected the final pin formation. The punch temperature and velocity had a significant effect on the overall die filling. The initial workpiece shape and solidification of the semi-solid material during forming influenced the micro/meso-feature formation sequence, affecting the final pin formation. Furthermore, grain deformation and distribution of the formed parts were investigated. The grains became larger due to induction heating and the forming process. Severely distorted grains were observed at the corner regions of the pins and the punch-workpiece interface.

The Application of FEM Technology on the Deformation Analysis of the Aero Thin-Walled Frame Shape Workpiece

Many thin-walled structure components widely used in aero industries not only have complex structure and large size, but also need high machining accuracy. However, because of their poor rigidity, it is easy to bring machining deformation caused by the existence of the initial residual stresses, the fixing stresses, cutting forces and cutting heat. The difficulty in ensuring their machining accuracy becomes a big problem, so that how to effectively predict and control the machining deformation has become an important subject in the development and production of our national defense weapons. This paper established a 3-D Finite element model with consideration of milling forces, clamping forces and initial residual stress field. By using this model, machining deformation of thin-walled frame shape workpieces has been computed. The simulated results are compared with experimental data, and the correctness of the simulation is verified. The study is helpful to the prediction and the control of machining deformation for thin-walled parts.

Two-Dimensional Tool Design for Two-Dimensional Equilibrium Electrochemical Machining Die-Sinking Using a Numerical Method

Electrochemical machining (ECM) can be defined as controlled electrolytic anodic erosion. ECM can machine hard alloys and metals with tools of softer metals, without affecting either workpiece microstructure or surface properties. There is no tool wear owing to a lack of tool/workpiece contact. The ECM medium between the tool and workpiece is electrically conductive, causing the finished workpiece geometry to vary from the tool and not to become a direct inverse of the tool shape. The characteristics of the workpiece material can also affect shape transfer, increasing the difficulty of designing and simulating ECM tools. At present, ECM tool design in industry is a trial-and-error process that can be prohibitively time-consuming. Automated design and simulation procedures are, therefore, desirable. This paper describes a computational approach to ECM tool design for two-dimensional cases based on the solution of a set of ordinary differential equations in a basis function format that are based on the electric field during the ECM process. This method has a number of advantages. It allows for the use of geometric representations of the tool and workpiece, such as B-Splines and Bèzier curves. This enables easy integration with most current computer-aided design software. It is also possible more easily to design and simulate tools for non-ideal machining conditions, where parameters such as electrolyte conductivity vary with the ECM cell. Above all, this method can design tools directly for the ECM process, given a particular workpiece shape without iterative methods. Computational trials have been carried out and compared with the results of an experimentally validated model. These showed that the method was effective for tool design under ideal machining conditions and was easier to use for non-ideal condition modelling.

DEVELOPMENT OF SIMULATION SYSTEM ON WEDM FIRST CUT

In order to understand the mechanism of WEDM (Wire electrical discharge machining) and find out the influence of machining parameters on the accuracy, a simulation system for WEDM is developed., which can accurately reproduce the discharge phenomena of WEDM machining on computer through searching for the discharge location, removing the workpiece and analyzing wire vibration. To verify the feasibility of the simulation system, the simulation results are compared with the experimental results. In order to obtain the 3D data of the discharge gap and workpiece shape from the experimental results, a new measurement is proposed. By comparing the simulation results and experimental results, it is found that the simulation method is feasible. The results show that the machined shape obtained from the simulation is almost consistent with the machined shape obtained from the experiments when the wire tension and servo voltage are adjusted; whether the machined shape along machining direction is convex feature or concave feature depends on the relative value between the explosive force and electrostatic force.

123 ボールエンドミルによる多軸制御切削加工における被削物除去状態の幾何的解析(OS-1 切削加工)

This study deals with geometric analysis of workpiece removal in multi axis control machining with ball end mill. In order to predict both surface roughness and accuracy of workpiece shape in finish machining process, it is required to apply a new estimation method which can cope with quite small feed rate in cutting conditions. So, in this study, we introduce the developed removal model of workpiece, which is designed to consider influences of cutting edge roundness. And, we analyze both removal depth on each cutter mark and cutting error on workpiece shape, for a case of ball end mill with a throwaway chip. From results, we can find that distribution of removal depth on cutter mark is strongly influenced by tool posture and shape error caused by tool deflection is often bigger than height of cusps.

120 球面のボールエンドミル加工における加工誤差に関する研究(OS-1 切削加工)

Ball end mills are widely used in machining of parts with sculptured surfaces. The properties required for ball end milling are high productivity, high machining accuracy and integrity of machined surface. In this study the machining error theory is applied to the analysis of spherical surfaces. The workpiece shape is concave and convex. The work material used is plain carbon steel. Cutting tool is a cobalt enriched high-speed steel (Co-HSS) ball end mill. The machining errors are examined for various cutting conditions and cutting modes. The machining error in down cut is lager than that in up cut. It is seen that the influence of cross-feed on machining error is largest in the cutting mode of down cross-feed and down cut. The machining error in concave workpiece is lager than that in convex workpiece. But in down cross-feed., the machinging errors in both shapes are almost same.

CIRCULAR ARC FORMING IN TUBE EXPANSION FORMING

A mechanical model considering sliding friction between the tube and die is proposed to explore the plastic deformation behavior of the tubes during a expansion process in a square cross-sectional die. That the radius of the circular arc with the minimum limit value is firstly proved, and the calcula-tional formulas are given, based on researching on the no friction slipping model. The minimum radius of the circular arc which is defined can decide the workpiece's shape and forming pressure. At last, experiments of tube expansion in a square die using a self-designed apparatus are also conducted. The experimentation results are between no friction slipping model and friction slipping model. The correctness of no friction slipping model and friction slipping model is also verified by contrast with experiments and calculation results.

Study on Computer-Aided Process Planning of Mold Part Machining

In this paper, an algorithm for projecting the machining remained area in a prior machining to the cutter location surface for the next machining is proposed. This projection is useful for automating some process planning task of mold machining, such as the determination of the milling region in the following machining operations. In our proposed algorithm, the milling simulation and the inverse offsetting of the result shape of the simulation is required. Most milling simulation programs use discrete Z-map models for representing the workpiece shape. In this paper, an algorithm for inverse offsetting the Z-map model is discussed. Our algorithm computes dense zig-zag curves covering the Z-map model, then it generates the swept volume of the inversed cutter moving along the curves to obtain their Minkowski sum shape. Proposed algorithm is implemented and an experimental process planning assistance program using this technology is demonstrated.

Adaptive Table-Motion Control of a Surface Grinding Machine Using an AE Sensor

Improvement in grinding efficiency is very important to economically produce precision parts. This paper proposes a new table-motion control system for reducing non-machining time in the surface-grinding process and describes the results of performance tests of the system. The table-motion is adaptively controlled so that the table stroke is shifted along a workpiece shape. That is, an AE signal is emitted from the contact zone between a grinding wheel and a workpiece and is diminished when the wheel leaves the workpiece. When the signal level becomes less than a preset trigger level, a command is sent to a table controller to reverse the table-motion. By using the proposed system, unnecessary table over-travel is successfully eliminated and total machining time is reduced by 22 to 38 percent.

Reliability-based preform shape design in forging

A reliability-based optimization method is developed for preform shape design in forging. Forging is a plastic deformation process that transforms a simple shape of workpiece into a predetermined complex shape through a number of intermediate shapes by the application of compressive forces. Traditionally, these intermediate shapes are designed in a deterministic manufacturing domain. In reality, there exist various uncertainties in the forging environment, such as variations in process conditions, billet/die temperatures, and material properties. Randomness in these parameters could lead to variations in product quality and often induce heavy manufacturing losses. In this research, a robust preform design methodology is developed in which various randomnesses in parameters are quantified and incorporated through reliability analysis and uncertainty quantification techniques. The stochastic response surface approach is used to reduce computation time by establishing a relationship between the process performance and shape and random parameters. Finally, reliability-based optimization is utilized for preform shape design of an engine component to improve the product quality and robustness. Copyright © 2005 John Wiley & Sons, Ltd.

ED machining of WC–Co

The composite of tungsten carbide–cobalt (WC–Co) is a very important material used in carbide dies, cutting tools and components under erosion. The machining of this material is very difficult because of its very high hardness. Among conventional methods, this material can be machined with pendulum grinding method when special and expensive discs were used. However, the material removal rate is very low and other limitations in machining parameters and workpiece shapes are imposed. Among non-traditional methods, electro discharge machining (EDM) is considered as the best candidate for machining this material. However, the process is unstable especially when die sinking machines are used. This is due to generating open circuit, short circuit and arcing pulses. This paper analyses the instability of EDM process when machining WC–Co composite and introduces the ways to control it.