Design And Development Of Ultra-precision Polishing Machine

With the development of science and technology,the demand for large-size planar components has been growing in recent years.Large-size(> 300 mm)planar components,such as silicon wafers,KDP crystals and sapphire windows,are widely used in modern optics,semiconductor industry,aerospace and astronautics manufacturing,etc.Large-sized planar components belongs to the typical hard-to-machine materials due to its distinct properties such large diameter and low thickness,which required to have high geometric accuracy,surface/subsurface quality and high processing effectively in the process of manufacturing.At present,chemical mechanical polishing(CMP)is the most effective method to acquire the high roughness and surface accuracy.However,the existing equipment has many problems as insufficient process control accuracy,poor processing consistency,high requirements for workers' proficiency and low processing efficiency,which make it difficult to meet the requirements of ultra-precision machining of large-scale planar components.Thus,this has become an important factor hindering the development of ultra-precision machining.In order to acquire the high surface accuracy and quality of large-size planar components in the process of CMP,this paper analysis the main factors affecting the machining quality and establishes the model of controlling geometric error of machine tool.At the same time,this paper develops and designs the ultra-precision polishing machine and tests its performances.The main research work and conclusions are as follows:(1)In this paper,the main influence factors of processing quality in polishing process for surface accuracy and quality were analyzed.The functions of spindle turning precision control,platen surface measurement,platen conditioner and platen temperature control of machine were put forward.The basic structure form,work flow and main parameters of the machine are determined.(2)In this paper,the platen conditioner unit model was established based on the theory of multi-body,which could determine the main error elements affecting the shape precision of platen surface.The main factors affecting the surface shape error are analyzed,which provides a basis for the design and assembly of machine tool motion unit.(3)The objective of this paper is to design the main functional units from functionality and reliability of machine tools.The rotary unit of polishing platen adopts the structure of hydrostatic bearing and torque direct drive motor.In order to ensure the consistency of platen temperature during the process of polishing,the internal-water-cooling platen is used in the platen temperature control unit.The system of polishing platen shape finishing and the platen surface measurement were used to realize the targeted renovation of turning tool for the specific surface of platen.Finally,the statics and model analysis of key structure components are completed in this paper.The results show that the maximum deformation of the polishing platen and the lathe bed are 0.81 ?m and 9.18 ?m under static load,and the maximum stress are 5.465 Mpa and 0.081 Mpa,which meets the design requirements of stability and reliability of machine tools.(4)In order to reach the machining precision of the polishing platen surface,accuracy measurement and adjustment of the machine tool platen finishing unit was completed in this paper.In the ultra-precision polishing machine of independent design and development,the experiment were carried out on the KDP crystal substrates with the size of 100 x 100 mm.In this experiment,the polishing platen planeness is 0.028 mm and the spindle rotary speed fluctuation is 0.36% during the processing.The average surface roughness of the characteristic points of the crystal converges from 245.22 nm to 26.59 nm rapidly.The experiment results show that the ultra-precision polishing machine of independent design and development can meet the processing requirements of large-sized planar components.