| Sapphire is an excellent optical window material because of its admirable mechanical and optical properties.Due to the features of high hardness,mechanical strength and thermal shock resistance,sapphire is a kind of typical brittle hard material which is difficult to machine.In order to meet the application requirement for sapphire dome,it is necessary and urgent to solve the problem of improving the machining efficiency for widely use of the sapphire dome.In this thesis,single crystal sapphire dome was taken as research object.Three types of diamond tools were used to milling-grinding,lapping and polishing single crystal sapphire dome.The basic theory and experimental research were carried out around the three processing steps that laid the groundwork for efficient processing of sapphire dome.The main research contents of the thesis are as follows:1.The kinematics and dynamics of the main moving parts of the sapphire dome processing equipment were studied.The kinematic model based on the D-H method and the Lagrangian multi-body dynamics model were established.Moreover,a suitable sapphire dome processing equipment were designed.The comprehensive evaluation method based on fuzzy mathematics was used to judge the health of the equipment.2.The cutting force and roughness model of brazing diamond tool milling-grinding sapphire dome were established.The relationship between the process parameters and milling-grinding force and roughness were discussed.Furthermore,the parameters choose intersection were got.The characteristics of sapphire surface after processing and the removal mechanism of brazed diamond tool milling sapphire dome were studied.Based on the above analysis,the application mechanism of high efficiency molding sapphire dome was obtained.A textured diamond tool suitable for precision machining of sapphire has been fabricated.3.A method of lapping sapphire dome based on textured diamond consolidation tool was proposed.The diamond film growth model of polishing tools was established.Moreover,the diamond thick film,the turriform micro-diamond film,the prismatic micro-diamond film and the spherical nano-diamond film were prepared.The tribological characteristics,the wear mechanism of diamond thick film and three types of thin film against sapphire were studied respectively.The results showed that CVD films with different textures show different tribological properties.The diamond film grows layer by layer and the size was controllable.4.The abrasive trajectory of polishing track was studied.Based on the large span structure theory,the distribution model of the polishing track was established to guide the selection of process parameters.Specifically,after processing,the surface quality of sapphire dome was Ra 0.25-0.6μm,the material removal rate was up to 38.7μm/min.The data proves to be a high efficiency way of polishing.Further,the influence of the processing parameters on the surface quality of the workpiece was analyzed.Polishing process based on the solidified diamond film tool with high surface accuracy and quality was obtained.5.The preparation method of diamond magnetic honing was discussed.The sputtering model of the magnetic abrasive was established and the state of the magnetic abrasive was controlled during the lapping process.Meantime,the effects of different process parameters on the surface quality of the dome were researched.The results showed that material removal rate of sapphire can be as high as 2.21μm/min and the surface roughness Ra can be about 10 nm. |
