Assembly Precision Analysis And Process Improvement For Large Opto-mechanical Unit

As a large high-power solid-state laser device, SG-III contains 192 beams, which is made up of a number of large optical components with high precision. Because of the direct impact on shooting accuracy, optical machine components need be assembled with high accuracy requirements, which is a great technical challenge. Take reflecting mirror unit with sub-micron precision for example, in order to accurately describe formation mechanism of assembly error, structural deformation mechanism and assembly geometric tolerance stack-up is studied and the analysis method of assembly accuracy and stability is presented.Firstly, for the surface accuracy of the optical element, structural deformation of optical elements with assembly preload is analyzed by finite element method, an orthogonal square Zernike basis set is generated form standard circular Zernike polynomials by Schmidt orthogonalization. Then the surface accuracy is analyzed using Zernike polynomials with primary finite element data. Furthermore, taking some random factors into account, there is a random distribution within a wide range for real fastening forces even under same tightening torque. So Monte Carlo simulation method is proposed to predicate the impact of the uncertain fastening forces on the reflector's surface deformation. Additionally, the force limitation is also obtained to control the surface deformation, which can be used to guide practical reflector precise assembly.Then, geometric error propagation model is established, geometric assembly precision analysis model is established by 3DCS using full-size three-dimensional model of the mirror assembly. The result shows the mounting angle error of mirror far exceeds the performance requirements, so precision alignment is needed. Off-line calibration system is established to achieve optical alignment, by adjusting the three anchor points of the z displacement position. reflecting mirror unit through off-line calibration meets performance requirements. The stability is analyzed by transient dynamic analysis, modal analysis, random vibration analysis. The stability with existing assembly conditions meets the requirements.Finally, based on the above analysis, improvement of the assembly process is proposed. From three aspects: material of shim, control precision of screws and mounting structure, the assembly process is improved.