Optimal Design And Experimental Study Of Fixed Abrasive Pad Based On Three-dimensional Abrasive Trajectory

Lapping and polishing is widely used for manufacturing sapphire,silicon carbide and other hard and brittle materials,which is an important technology to achieve ultra-precision processing of these materials.Fixed abrasive pad has been widely used in lapping process due to its unique advantages such as high processing efficiency,better process controllability,lower production cost and environmental protection.As pad patterns,abrasive parameters and machining parameters are the key factors affecting the machining performance of fixed abrasive pads,many previous studies on these factors were carried out in order to realize high efficiency and high precision machining besides green environmental protection considerations.Aim at many problems in the processing of flattening of the hard and brittle materials surface and the inadequacies of existing research results at present,this paper is carried out the research on the processing of sapphire wafer grinding with fixed abrasive pad.A threedimensional trajectory model of abrasive particles was established to study the influence of abrasive parameters,pad pattern and processing parameters on the material removal of the workpiece,and the material removal characteristics based on the model of threedimensional trajectory of abrasive particles were systematically analyzed.Based on the characteristics of three-dimensional trajectory,an optimal design method of the fixed abrasive pad was proposed,the preparation and experimental study of the pad under different abrasive parameters were also carried out.The main contents and conclusions of this paper are as follows:(1)Based on the abrasive parameters of actual pad characteristics,a digital model of the distribution of abrasive particles on the surface of pad is established.By analyzing and calculating the statistical law of abrasive distribution,abrasive size and abrasive concentration,the spatial distribution characteristics of abrasive particles on the pad was obtained.(2)According to the spatial distribution characteristics of abrasive particles,a threedimensional trajectory model of abrasive was established.The evaluation indexes such as average removal thickness,non-uniformity of material removal distribution,surface roughness and material removal rate are proposed.Compare the features of the twodimensional trajectory and the three-dimensional trajectory,and verify the correctness of the three-dimensional trajectory model;(3)Based on the three-dimensional trajectory characteristics of abrasive particles,fixed abrasive pad optimization design method is proposed.Carry out the research on the change law of the pad processing performance under the factors of pad pattern,abrasive parameters and processing parameters.The study found that under the processing conditions that the helix angle of the sunflower seed structure pad is 137.508°,the pressure is 7 kg,the speed ratio is 1.1,and the abrasive particle mass fraction is 40 wt%,lower surface roughness and higher material removal can be obtained.Among them,the surface quality of the workpiece processed by the 40 μm pad is better than that of the 30 μm pad;(4)The pad optimized design based on three-dimensional trajectory model is formed by resin curing.Pellets were arranged by 3D printing mold and fixed by UV curing technology.Sunflower resin fixed abrasive pad with concentration of abrasive particles is40 wt% and abrasive size is 30 μm and 40 μm were prepared.(5)The processing performance of two kinds pad with abrasive size is 30 μm and 40μm was studied experimentally.The results show that: compared with 30 μm fixed abrasive pad,when the 40 μm pad is used for processing,there are fewer scratches on the surface of the workpiece,but more abrasive particles fall off on the surface of the pad.When the rotational speed ratio was 1.1,the material removal rate is 300 nm/min,which is increased by 7.1%.However,when the workpiece surface roughness is 215 nm,it decreases by 10.4%.The maximum crack depth is about 24 μm,and the minimum crack depth is 16 μm,which is 37% and 33% lower than that of the 30 μm pad,respectively.