Dong Hui Wen

Theoretical Analysis and Uniformity of Trajectories in Lapping Process

A new trajectory and uniformity was studied for single lapping process, kinematic theory analysis trajectories of the workpiece under the mode driven by swing motion. According to the theoretical analysis on lapping trajectory and simulated results, uniformity during swing driven lapping process is better than tranditional lapping process, angle rotation ratio between lapping plate and swing plate has great effect on lapping uniformity, when rotation speed of lapping plate is three times to that of swing plate, best uniformity could be gotten during lapping process.

An Investigation to Semi-Fixed Abrasives Plate Characteristics

The most typical example of hard and brittle material is advanced ceramics, for its ultra-precision machining difficulty and wide applications, now it becomes a focus of attention. Semi-fixed abrasive plate (SFAP) is newly developed for preventing larger particles from doing workpiece surface damage in machining advanced ceramics, for larger particles from grain size dispersion or from outside of processing area could bring uneven load distribution on processing region of advanced ceramics. In this paper, Shearing strength, surface hardness and Young’s modulus as characteristics of SFAP are investigated. They were influenced by Grain size and abrasive weight ratio are analyzed and discussed, as well as the qualitative estimation of these influences on the characteristics of SFAP are deduced.

Study on the Abrasive Effecting Factors of the Removal Rate during Dual-Lapping Sapphire Wafer

Dual-lapping was a process to planarize the surface of the sapphire wafer, the nature of surface&subsurface damage and the surface uniformity was depended on the material removal mode and materials removal ratio. Material removal mode was studied in this paper, and the model of material removal was set up too. The SEM was used to scan the processed sapphire surface and the different removal style (two body and three body) were discovered. This research provided valuable insights into the material removal ratio and the dependence of lapping-induced damage on dual-lapping conditions, the asymmetry of abrasive granularity brought on the different materials removal mode and the surface asymmetry. The model was set up to qualitative analysis the material removal ratio in dual-lapping of sapphire, obtain the reasonable MMR and optimize the surface quality and the planarization result.

Parameters Optimization on the Lapping Process of 9Cr18 with Taguchi Method

9Cr18 is a type of martensite stainless steel. It has high hardness, chemical stability, fine anticorrosion, wearable and quench stability. It has been used in different areas with high-anticorrosion and high polishing surface as mirror. So it requires for the high level surface quality after lapping and polishing. In this paper, the surface quality (surface roughness and flatness) of 9Cr18 is discussed with lapping parameters which include velocity, load and time distribution of two lapping steps(rough lapping and Ultra-precision lapping). In order to optimize those parameters, an optimization experiment for lapping 9Cr18 with Al2O3 was designed by Taguchi method. Finally, the optimum condition of each factor can be determined that speed: 80rpm, load:3.0kPa, and time distribution: rough lapping time=15min, Ultra-precision lapping time＝45min are the optimum conditions for both Ra and Wt.

Investigation on Affecting Factors of Vibration in Milling Harden Steel Assembled with Different Hardness

The milling vibration affects machined surface quality and the size of the error, and has an important impact on the machining accuracy. This paper studies the different cutting parameters on cutting conditions on milling vibration during ball end milling Cr12MoV hardened steel assembled with different hardness steels, and use LMS. Test. Lab software to analyze the vibration signal on the condition of different spindle speed milling direction, axial depth of cut, and the vibration signal of transitional zone and the non-transitional zone are compared, providing the basis for a reasonable choice of milling parameters.

Experimental Study on the Precision Lapping of Sapphire Substrate

Experimental research on the surface quality parameters such as roughness and removal rate in the precision lapping of sapphire was promoted in this paper, effects of processing parameters as load, speed of rotation, grain size and density on sapphire surface quality was studied by experiments. Results showed that lapping load and rotate speed were the most important factors on the removal rate, grain size played a key role in the removal rate and roughness under the same conditions, profile tolerance of surface shape depends on the flatness.

Experimental Investigation on the Dynamic Cutting Forces in Internal Broaching

Cutting forces generated in broaching have a direct influence on the generation of heat, tool wear or failure, quality of machined surface and accuracy of the work piece. In this paper not only a cutting forces test scheme has been proposed but also a cutting forces measurement equipment has been designed with PCB 740B02 dynamical strain sensor and LMS SCADA III test system, respectively. Dynamical strain sensor was pasted on the cylinder type sensitive elements with which table and workpiece was connected. Experimental investigation on the dynamic cutting forces in the broaching direction of a hydraulic broaching machine had been carried out. Cutting forces measurement tests on Q235 steel workpiece material during broaching had been performed. Broaching in a variety of velocities, namely, 3.3m/min, 5m/min and 8m/min and in a variety of cutting depth, namely, 0.03mm, 0.04mm, 0.05mm and 0.07mm, were investigated. Output signal was analyzed both in time and frequency domains and the key characteristics of the cutting forces signal was obtained. Correlation between the frequency of broaching forces and the broaching velocity was also studied.

Statistical Analysis on Lapping Parameters for Sapphire Wafer

Effect of lapping speed, plate material and crystal orientation on material removal rate and surface roughness were investigated by experiments and Taguchi Methods. Experimental results show both materials remove rate and surface roughness could be finished by using sythetic copper lapping plate with w3.5 cubic boron nitride abrasive than that for thin plate. Materials removal rate and surface roughness have no much difference for different crystal orientation as A-plane, C-plane and M-plane with experimental parameter conditions, lapping speed would be recommonded to not over 40rpm.

Study on the Mechanical Properties of Sapphire by Numerical Simulation and Nanoindentation Technology

This paper presents a finite element (FE) modeling of the nanoindentation test of sapphire, in which the finite element method was employed to study the mechanical characteristic of sapphire under the nanoindentation process. The results demonstrated that the nanoindentation FE models were able to simulate the indentation loading-unloading curves of the sapphire. The load and unload displacement curves of the simulation and experiment results can match with each other well, and then the properties used in the simulation should be the actual properties of the sapphire. The Mises stress field distribution of the sapphire sample was calculated to reveal the alteration from elastic region to plastic region, which are useful for indentifying the ductile to brittle change in the sapphire abrasive process.

Research and Simulation on the Wear Uniformity of Lapping Plate

Lapping plate wear is of great influence on shape precision of workpiece. Investigation on the wear uniformity of uncertain eccentricity plane lapping was carried out in this research. The relative velocity function of the plate to the workpiece is obtained through kinematic analyses in the mode of uncertain eccentricity plane lapping, and material removal rate (MRR) function and wear uniformity function were deduced based on Preston equation. Effects of the ratio and eccentricities on the wear uniformity are discussed in detail through MATLAB simulation. Theoretical analysis and simulation results show that the ratio k1 of workpiece revolution speed to lapping plate is the key to decide whether the lapping plate is lapped uniformly. Theoretically, when k1<0, the greater |k1| is, the better the lapped uniformly of lapping plate can be. The ratio k2 of workpiece rotation speed to lapping plate has great influence on the lapped uniformly when k1 approximate 1, and k2 has little influence on the lapped uniformly when k1<0 or k1>1, Besides, a bit bigger eccentricity e1 is propitious to the lapping uniformly of the lapping plate, and bigger eccentricity e2 are also helpful to lapping uniformly of the lapping plate. And the conclusion could be extended to single-side plane lapping and double-side plane lapping process.