| Metal aluminium mirror has good reflectivity in a wide spectral range,and has the characteristics of easy purchase,good processing performance and light weight.Therefore,it is possible to use metal aluminium as mirror material.The surface of metal mirror machined by single point diamond is prone to produce turning "lines",which affect the image quality.The "lines" after turning can be effectively removed by particle lapping method.With high imaging quality,powder lapping of aluminium mirror is an effective way to achieve high precision,so it is necessary to study the large-size metal mirror with powder lapping.In general,the mirror with a diameter greater than 200 mm is called a large-size mirror.This paper introduces the influence of various technological parameters in lapping and polishing large-size metal mirror on the surface quality of metal mirror.The material and abrasive types of metal mirror were selected.The influence of abrasive particle size on the surface quality of metal mirror is studied by controlling variable method.In the process of lapping,the abrasive particle size changes from large to small,which can not only improve the lapping efficiency,but also obtain good surface quality.The influence of pressure and velocity on the surface quality of large-size aluminium mirror was determined by single factor method.The material removal rate in the lapping process was discussed,and the lapping mechanism of different kinds of lapping fluids in the process of granular lapping was analyzed.Effective abrasives in the lapping process of large size metal mirror are selected by normal distribution.The material removal rate of single effective abrasive is calculated in the whole lapping process.The removal of oxide film on the surface of large-size aluminium mirror was carried out by changing the type of lapping fluid.The lapping and polishing experiments of metal mirrors were carried out with acid,alkaline and oily lapping fluids with different PH values.Testing the experimental results with energy dispersive spectrometer,the effect of removing oxide film on the surface of aluminium mirror is characterized by oxygen content on the surface of metal mirror.The removal rate of oxygen on metal surface in acidic environment is related to the strength of acidity.The stronger the acidity,the better the effect of deoxidation.In alkaline environment,the stronger the alkalinity,the better the deoxidation effect.Removal ability of oxide film: oily environment is better than acidic environment,acidic environment is better than alkaline environment,and the brightness of metal mirror surface also shows the same relationship.The removal of oxide film in the experimental process can obviously improve the lapping efficiency of metal mirror.During the experiment,the problem of white spot caused by ultrasonic cleaning of aluminium mirror was studied.The mechanism of ultrasonic cleaning technology was studied,and the effects of ultrasonic frequency and cleaning liquid properties on the cleaning effect of aluminium mirror were analyzed.The results show that high frequency ultrasound is suitable for cleaning aluminium mirror,low frequency aluminium is prone to white spot,low temperature of cleaning solution is beneficial to cleaning of aluminium mirror,cleaning liquid with low surface tension is suitable for cleaning aluminium mirror. |
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