Papers by Keyword: Lapping

Abstract: The deformation and removal mechanism of a multilayered thin film structure involved in nanoscratching and diamond lapping processes were investigated. The results obtained from the two processes were compared, in terms of deformation characteristics and surface finish. It was found that both nanoscratching and lapping demonstrated similar characteristics. This work provides insight into the deformation and removal of a thin film multilayered structure under mechanical loading, and thus the outcome is of value for developing the efficient machining process for such structures.

Abstract: The practice shows that complex lapping motion trajectory can decrease the adverse effects caused by the lapping direction which has a great influence on the lapping of the natural single crystalline diamond cutting tool. For example, addition of a reciprocating motion can get better lapping performance and surface roughness. On some kinds of natural diamond cutting tool lapping machines a further improvement is made by designing an additional planetary spindle to provide planetary motion to the main shaft, which offers a more complex motion trajectory. With an increase in degrees of freedom of the lapping machine, it becomes difficult for technicians to master a good suit of motion process parameters. This paper proposes a set of methods to plan the lapping trajectory with respect to the machine that can perform complex lapping motion. Firstly, the proposed method designed a statistical parameter which is the variance of the direction angle distribution for the lapping velocity and its calculation method to evaluate the complexity of the trajectory. And then the multi-body kinematics model was established by using Simulink tool box in Matlab software for the purpose of model kinematics simulation and outputting data for calculation of the statistical parameter above. Finally, the genetic algorithm was used to find the best motion parameters of every shaft under certain restrictions. The advantage of the set of lapping trajectory planning method presented in this paper is that it combines the powerful multi-body simulation and signal processing ability of Simulink tool box and the characteristics of the genetic algorithm in almost no limitation on awaiting optimization function and suitable for complicated problems. So the method provides not only a way for planning complex diamond lapping trajectory but also a general approach to solve the problem on machine motion process parameters optimization.

Abstract: Anisotropic materials are used in various fields because of their superior mechanical properties such as high specific strength. However, the surface generation mechanism in loose abrasive machining such as multi-wire sawing of anisotropic materials has many unknown characteristics. This study mainly aims to clarify the sliced surface generation mechanism in multi-wire sawing of glass fiber reinforced plastics (GFRP). Therefore, the slicing experiments and the wet lapping experiments are carried out in this study. In this paper, we describe the fundamental slicing characteristics of GFRP and the influence that the orientation angle of reinforcement fibers has on the newly generated surface of GFRP. We find that high-precision machining of GFRP is possible using a multi-wire saw. The slicing rate and thickness variation are not dependent on the orientation angle. However, sliced surface roughness depends on the orientation angle, and it tends to decrease when the orientation angle increases. In addition, sliced surface generation and polished surface generation involve similar mechanisms and produce very similar surface characteristics.

Abstract: In general, aerostatic bearings are flat bearings and the stringent manufacturing tolerances in geometric dimensions and profile will make the bearing ideal for obtaining high stiffness during measurement. Aerostatic Spherical Bearing (ASB) on the contrary is a special bearing which provides a frictionless pivot and allows three degrees of rotational freedom. Methods involved in manufacturing and realizing a highly stiff ASB is discussed in this paper. ASB components viz. Stator and Rotor of hemi-spherical in geometry are the critical components to be machined, which are used in Mass properties and Dynamic Balancing Measurement machine (MaPDBM). MaPDBM is used to measure mass, center of gravity, moments of inertia and static & dynamic unbalance of spacecraft. An air film of 25-50 μm thickness separates the stator and rotor during measurement, thus forming an aerostatic bearing. Precise Machining, Thermal treatments to ensure crash-proof design, Special processes like lapping for profile correction, Geometrical and profile measurements during different stages in the sequence for controlling the bearing parameters using Coordinate Measurement Machine (CMM) are the challenges involved in the machining and realization of the ASB components and the same is discussed in this paper.

Abstract: This study examines the feasibility of using high-porosity and conductive bamboo charcoal in electrophoretic deposition (EPD)-assisted polishing of silicon wafers and explored the influence of various parameters on surface roughness. EPD-assisted polishing with bamboo charcoal offers an alternative to the lapping process prior to CMP. According to the results, the best parameter combination obtained under the current experimental setting is machining time, 12 min; rotational speed of platen, 75 rpm; and voltage, 6V. EPD indeed contributes to more effective and efficient polishing, with better surface quality attained within a shorter machining time.

Abstract: In view of the machining difficult problem of hyperboloid, a new method is presented that high speed lapping hyperboloid parts using the bended lapping tool, and the principle of high speed lapping by the bending method is discussed. The mathematical model of bended lapping tool has been established using mechanics and higher mathematics, and the expression of width function of lapping tool is deduced. Analysis of the calculating example indicated that this method is possible to design the needed lapping tool. The bending experiment of lapping tool has confirmed the feasibility using this method, the biggest error of face shape was 1.0038μm, the face shape precision can satisfy the majority part request.

Abstract: Lapping the parabolic work-piece with the lapping tool in bending method is a new technology, which has some good characters such as low cost, scope broad, easy operation, and high precision. The lapping tool is formed by the means of bending and forming with solid abrasives on it in the experiment. The experiment shows that parabolic workpiece can be lapped using this method. The experimental result indicates that the work-piece face shape precision is high with the lapping tool, the maximal error is 0.0881mm and the minimal error is-0.0011mm, and lapping efficiency is high and the cost is low.

Abstract: This paper analyzes the existing problems of acting lapping pressure in lapping internal holes of main cylinder of brake-pump with solid abrasives, proposes a new type of solid abrasives supporting method, namely, three supportting points acting lapping pressure method. The method improves pressure distribution between solid abrasives and the surface of the machined workpiece,which is favorable to increase cylindricity of machined hole.Through actual machining process, new method is demonstrated increasing cylindricity accuracy of machined holes of main cylinder significantly.

Abstract: The path distribution can directly affect the machined workpiece surface quality in lapping and polishing, such as planeness, roughness, etc. In present paper, the influence of rotate speed ratio (RSR) and abrasive position on path distribution was analyzed with a single fixed abrasive. The results show that the RSR and abrasive position has heavy influence on the path distribution. The path distribution with decimal RSR is more intensive and complicate than that with integer RSR, especially complex decimal RSR, and it can be also affected by the abrasive radial and circumferential position, but the shape of path is not changed with different abrasive circumferential position which only affects the initial phase angle of path.

Abstract: The rolling element is the most important component of rolling bearings. Its geometric accuracy and consistency affect greatly the performance and working life of bearings. In this paper, a standard Taguchi L9(34) orthogonal array(oa) is designed to analyse how abrasive size, rotating speed of plates, deflection angle of carrier holes and other factors impacting on precision of cylindrical roller process and achieved the optimized parameters combination by adopting evaluation of Signal-to-Noise ratio and ANOVA analysis(analysis of variance). Under the optimized lapping condition, the roundness,pand s can reach , and respectively.