| KDP crystal which carries excellent electro-optical nonlinear character is irreplaceable in those high-power laser devices. However, as KDP crystal is quite soft and brittle, anisotropy, easily deliquescence and temperature sensitive, and meanwhile with the high precision (≤λ/6PV,≤5nm RMS) and high optical property (the laser induced damage threshold must be no less than15J/cm2) requirement by the technical application, it has been that right international difficult problem to machine KDP crystal, especially for the large scale surface, ultra-precisely for a long timeFor that, the paper suggested a novel process of computer controlled Micro-nano dissolution polishing based on the characters of KDP, especially of it’s easily deliquescence character. The research focuses on the foundamental theory of material removal in the process of Micro-nano dissolution polishing of KDP deeply. To build the removal function of computer controlled Micro-nano dissolution polishing of KDP combining that theory with computer controlled optical surfacing technology which is quite mature in the area of optical surfacing, to optimally solve the dwell time and further efforts to experimentally research. All those have important theoretical guiding significance and practical promoting value to the ultra-precision optical surfacing of medium and large scale KDP crystal.Firstly, a model of material removal of Micro-nano dissolution polishing of KDP was promoted based on the contact theory of two rough surfaces by the combination of the special polishing fluid structure of KDP, the lubrication condition between the two surfaces, the controllability mechanical and the composition of material removal. The executed verifying experiments proved that the biggest deviation is less than20%. On the basis of the material removal model, that typical Preston Equation was revised and that deteriorating phenomenon by traditional polish process to polished surface shape precision was figured out.Secondly, as those machining conditions are quite different between computer controlled Micro-nano dissolution polishing and traditional process, the frictional character on the interface of the new process was experimentally analysed. And the lubrication condition was considered as boundary film lubrication by the typical Stribeck Curve. Moreover, the material removal was mainly caused by the interaction between the mechanical and dissolvent effect, which was confirmed by the experiments of polishing without fluid and with only acohol as fluid. That meant, it’s feasible to construct the removal function based on the revised Preston Equation and the motion mode of polishing tool for computer controlled Micro-nano dissolution polishing of KDP. The practical region of parameters’combination which made the removal function much more homogenetic and steady was obtained by comparing the theoretic computing and large scale experimental results.Finally, a computer controlled Micro-nano dissolution simulation system for KDP was complied based on the non-negative least squares dwell time solving algorithm with minimum residual error as the target function. Those polishing processes were simulated took the three type surface shape errors after SPDT as initial surfaces. With the dwell time and CNC codes generated by the simulation system, the computer controlled Micro-nano dissolution polishing and finishing experiments were carried out to a surface with initial surface shape precision of17.480μm PV,2728.064nm RMS. and initial surface roughness of188.092nm Ra. After certain times iteration, the final surface shape precision had achieved5.989μm PV,546.788nm RMS, and the final surface roughness had reduced to34.885nm Ra. After finishing process, surface roughness had achieved19.204nm Ra. |
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