Papers by Keyword: Material Removal Model

Abstract: This paper aims to quantify the effects of the machining condition on the surface topography in electrical discharge machining (EDM), including pulse current, pulse duration and so on. Firstly, the heat source of a single electrical pulse is defined by Gauss distribution, and the thermal effects of machining parameters on the workpiece material erosion are simulated by Finite Element Method (FEM) package ANSYS. Then, the crater size of a single pulse is numerically simulated based on the thermal model of a single pulse discharge. Furthermore, the superposition of multiply craters created by continuous pulse discharges in a random distribution is calculated by MATLAB software program, so that the evolution of the surface topography can be obtained with the combination of FEM simulation and topology calculation. In this way, the surface roughness is quantitatively calculated from the specified EDM parameters.

Abstract: This study introduces rotary ultrasonic face milling (RUFM) process into flat surface machining of K9 glass. The effective cutting velocity, and cutting length of single diamond particle were presented in RUFM. The model of material removal for RUFM was developed through examining indentation fracture mechanics theory and material removal characteristics of brittle materials, and analyzing kinematics properties of diamond grits in RUFM. With a view of comparative researches, the cutting force of RUFM and diamond milling of K9 glass are compared. The experimental results tell that the relationship between the cutting depth (dc) and the ultrasonic amplitude (A) of the cutter has remarkable effects on cutting force, which was also discussed in the kinematic characteristics analysis section. The results also show that RUFM process can significantly reduce cutting force and the effects of process variable changes on cutting force in RUFM are weaker as dc is smaller than A. However, the reduction trends of the cutting forces in RUFM are very small and even increased in some process conditions, as dc is larger than A. It suggests that the cutting depth should be smaller than the ultrasonic amplitude of the cutter with RUFM process to obtain better processing performance.

Abstract: This paper reviews three methods used to evaluate the uniformity in the lapping process. The first one evaluates the uniformity in lapping process according to studying the uniformity of lapping trajectory. The second one, compared with the measurement pattern based on polar coordinate, explains the advantages of Cartesian -based coordinate pattern in evaluating the lapping uniformity. The last one develops a model to calculate material removal in the lapping process and indicates the uniformity by calculating the material removal. These methods evaluate the uniformity in lapping process from different views, respectively, but each method still has various drawbacks. Therefore, further researches must be carried out to improve the system used to evaluate the uniformity in the lapping process.

Abstract: Ultrasonic- magnetorheological combined finishing (UMC) is a new technique for the ultraprecision machining of aspheric surfaces, especially for high quality workpieces with small curvature radius concave surfaces. According to the characteristics of UMC finishing, material removal model has been developed. Several types of tool path planning algorithm have been discussed. Two kinds of polyline dwell time algorithm are presented. Polyline Dwell time algorithm based on two-dimensional discrete convolution is a new dwell time algorithm, and the dwell time on the endpoints which compose the tool path can be solved by the algorithm directly. Every polyline dwell time is the mean value of dwell time of two endpoints, therefore, the polyline dwell time of every type of tool path can be solved efficiently by the algorithm. The simulation of two dwell time algorithms has been conducted with same removal function and original error distribution, and the pv convergence rate is improved from 0.939 to 0.973 by using new algorithm. Figure error PV values reduced to 29.4 nm from 1.67μm after UMC finishing. The efficiency of the polyline dwell algorithm is proved by computer simulation and experimental results.

Abstract: In this paper, based on the octree partition, bounding boxes and triangulated surface model, we developed a new virtual material removal method for machining of 3D complex surfaces. In this method a new tri-prism space partition algorithm based on octree and triangulated surface model is applied to partition the 3D complex surfaces. Traditional triangular-faced algorithm is used in 3-axis machining simulation, which is computationally expensive and memory demanding. In contrast, this paper presents a virtual material removal model using the dynamic tri-prism space decomposition algorithm (i) to represent 3D complex objects, (ii) to reduce the computation complexity, and (iii) to accelerate the model updating procedures in a graphic simulation process. Based on mathematical model of virtual material removal, the 3D model of virtual CNC machining process was developed.

Abstract: The material removal mechanisms of sapphire substrate in double-side lapping process were studied. The concepts of brittle vs. ductile machining and two-body vs. three-body abrasion were used to classify the processing mechanisms. The material removal models of double-side lapping process in different mechanisms were analyzed and researched. The experiment showed that the material removal model can describe double-side lapping process of sapphire qualitatively.

Abstract: The fluid magnetic abrasives (FMA) are a new type of precision finishing abrasives, which can be used to finish the work-pieces with intricate or complex shape to a quite low surface roughness value. As a key parameter, the material removal rate has a great impact on the finishing capabilities and the final surface roughness. In order to get a better understand of FMA removal mechanism, the numerical analyses was used to simulate the shearing stress field and velocity distribution. The experimental results are discussed as well in this paper.

Abstract: A new plate polishing technique with an instantaneous tiny-grinding wheel cluster based on the magnetorheological (MR) effect is presented in this paper, and some experiments were conducted to prove its effectiveness and applicability. Under certain experimental condition, the material removal rate was improved by a factor of 20.84% as compared with the conventional polishing methods with dissociative abrasive particles, while the surface roughness of the workpiece was not obviously increased. Furthermore, the composite of the MR fluid was optimized to obtain the best polishing performance. On the basis of the experimental results, the material removal model of the new plate polishing technique was presented.

Abstract: The realistic dynamic image of virtual milling process is important in the field of virtual manufacturing technology. However, it is difficult to realize virtual 3-D workpiece model removing process. Material removal algorithm model based on an adaptive dynamic quadtrees algorithm is proposed in this paper. Based on mathematical model of virtual material removal, the 3D model of virtual CNC milling process was developed. The real-time simulation of material removal process was realized in the virtual reality environment.