Abrasive Jet Polishing and its Applications in Surface Finishing

Abstract

Problem statement: Single Point Diamond Turning (SPDT) is highly deterministic and versatile in producing various forms of precise optics. A typical example is the production of large off-axis aspheric mirrors and various infrared mirrors and mandrels. However, the fine periodical turning marks left in the surface critically limit its performance and they are difficult to be avoided for traditional polishing methods. Approach: This study introduced abrasive jet polishing to remove the periodical turning marks. Firstly the principle of abrasive jet polishing technique was described. Then combined with theoretical study, Computational Fluid Dynamics (CFD) simulation and process experiments, the mechanism of the material removal in abrasive jet polishing was analyzed. It was concluded that the wall shear stress of micro-abrasives is the main cause of material removal in this process. Based on this, abrasive jet polishing experiment was carried out on plane copper sample and the surface of Arrayed Waveguide Grating (AWG) which were machined after SPDT. Results: After polishing the periodical ripples on copper sample left by SPDT were removed completely and the Ra value of the sample decreases from 11nm to 3nm. In addition, the burrs and pits on the surface of AWG Mould after SPDT are removed successfully with this technique, which solves an intractable problem in manufacture area. Conclusion: In this experiment it was found that abrasive jet polishing technique has its inimitable advantages in removing the periodical turning marks and finishing the AWG mould and it will have a broad prospect of applications in modern precision manufacture area.