Study On The Development Of A Novel Precision Lapping Machine With High Efficiency

Low elastic modulus materials for nanoindentation test require ultra-smooth and damage-free surface,while the high precision in forming and low defects in quality plane lapping are essential for obtaining ultra-smooth and damage-free surfaces,which is also an important development trend in the field of lapping.Therefore,it is of great theoretical and scientific significance to study how to improve the uniformity of workpiece's surface and to obtain low-damage surface while ensuring the high efficiency of abrasive lapping.In order to obtain ultra-smooth and low-damage surface efficiently and steadily,a new lapping method,which was driven by irrational speed ratio and sandwich mechanical lapping,was developed.On the basis of this method,the driving mechanism of irrational speed ratio and a new lapping fine-tuning fixture were developed,and the relative comparative experiments were carried out by using the driving mechanism and grinding fixture.The main research work includes:(1)The mathematical models of abrasive disc wear and grinding trajectory were established.The effects of grinding speed ratio on abrasive disc wear,abrasive trajectory shape,trajectory curvature and material removal rate were simulated and analyzed by MATLAB software.The results show that the disc wear and the uniformity of grinding trajectory under irrational rotational speed ratio is better than those under rational rotational speed ratio,and the material removal is more uniform,and the rotational speed ratio has a great influence on the change of trajectory curvature.At the same time,an irrational speed ratio driving mechanism was designed,and the drive motor was selected.The meshing bevel gears and the rotating shaft were designed and checked.The speed ratio between the lapping disc and the workpiece disc was realized.(2)The evolution law of free abrasive particles from direct contact to quasi-contact andnon-contact state in sandwich mechanical lapping was analyzed.The lapping finite element model was established by ANSYS Workbench.Then the stress of workpiece samples and substitutes under load was simulated.The results show that the equivalent stress on the surface of the workpiece sample is directly proportional to the elastic modulus of the substitute,inversely proportional to the Poisson's ratio of the substitute and the area ratio of the substitute to the workpiece sample.According to the requirement of different lapping stages on the grain size,two new grinding fine-tuning fixtures were designed independently,so that the height difference between workpiece samples and substitutes can reach the predetermined precision level.(3)By using low elastic modulus materials such as polycarbonate(3GPa),quartz glass(72GPa),electrolyti copper(108GPa),and monocrystalline silicon(187GPa)as sample,the irrational speed ratio drive mechanism and the rational speed ratio drive mechanism were installed on the YR610 X single-side grinder to do the comparative test.At the same time,machining quality of the fine tuning fixture and sandwich mechanical lapping was contrasted with traditional mechanical lapping.The surface roughness,flatness and material removal rate of the low elastic modulus specimens were tested by Metallurgical microscope,Form TALYSURF I60 and weighing method.The results show that the surface roughness,planeness,total thickness variation,bow,warp and material removal rate of the low elastic modulus specimens are improved under irrational speed ratio driving mode.The surface roughness of the low elastic modulus materials is better,the surface morphology is better,and the damage is smaller.By means of simulation,mechanical design,comparative test and sample characterization,the feasibility of irrational speed ratio drive and sandwich structured mechanical lapping method and the reliability of the developed irrational speed ratio drive mechanism and grinding fine-tuning fixture are verified.