| Ceramic materials,therewith the excellent hardness,abrasion performance and corrosion resistance,are more and more widely applied to manufacture precision cutting tools,precision ball bearings,micro transmission parts,inertial guidance parts and so on,especially in the field of high end military industry and aerospace industry.Mainly including precision micro drilling heads,micro milling tools,micro gears,micro screw leads,micro rotators,and other columnar parts.Because of the hardness feature of ceramic materials,they are difficult to machining,high time cost,low rate of final products and low accuracy.Especially the fine machining of columnar or helical parts,is always the great challenge of traditional manufacturing industry.Be aimed at the actual demands and manufacturing difficulties of ceramic columnar transmission parts,this thesis propose the study on columnar ceramic material micromachining by picosecond laser.First of all,the aluminum nitride ceramic is chosen as sample material,study on the elimination of aluminum nitride ceramic material processed by picosecond laser.Through the research on flat sample,the appropriate laser wavelength and threshold of laser energy were found.By the way of simple variable method tests,the relationship of laser power,process paths,focus position,scan speed and repetition were found,and also the relationship of eliminate rate,surface quality and process parameters.Based on these relationships,the laser elimination mathematical model was setup.Base on the demands of ceramic columnar transmission parts machining,a sample chuck equipped with rotation axis,applied to machine columnar materials,is designed by computer aided design software.The control of rotation axis is programmable.The clamping of sample is easy to adjust.The chuck is fitting for different size of samples.According to the picosecond laser machining platform,the sample chuck is integrated.The picosecond laser machining platform is extended from plane processing to stereo processing.Combination of mathematical model and rotation sample chuck,for the different structure of columnar parts,the machining jobs are programmed with different process paths,laser parameters,process sequences.Finally the real columnar transmission parts with practical value are processed on columnar ceramic samples.In this research,the 1064 nm wavelength picosecond laser is chosen.The micro gear,micro helical gear,are processed on 3 mm diameter columnar ceramic samples.The machining accuracy can achieve 10 μm,the eccentricity is less than 50 μm.When using laser output power 5 W,the machining efficiency can achieve 0.64 μm/s,the processing time of 3 mm diameter gear sample is about 8 minutes.The surface roughness can achieve 2 μm.This machining method has the practical application value on aerospace industry and military industry.Due to the independence of elimination mathematical model and machining method,for the different materials,the methods can be easily extended with appropriate parameters.The picosecond laser can be used on the elimination of other ceramic materials,even all the other materials which can eliminate by laser.The great expansibility provide the research foundation of columnar transmission parts laser micromachining. |
PDF Full Text Request