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.
Highlights
Much research has been made on Abrasive Jet Polishing (AJP) process; there are little attentions been paid to the material removal mechanism
For better understanding the material removal mechanism of AJP process, we introduced Computational Fluid Dynamics (CFD) simulation for jet polishing process
Study of material removal mechanism in AJP process abrasive grains of cerium oxide (CeO2) and other above, we made some experimental research on additives was used in the experiment
Summary
The homogeneously mixed slurry is pumped by a relatively low-pressure pump and guided through a nozzle to form abrasive jet. The jet sprays on the work piece some distance above and finishes polishing process. The stand-off distance and the angle of the work piece with respect to the nozzle can be set by the numerical control machine. Abrasive Jet Polishing (AJP) process was first introduced by Fahnle at al. Horiuchi O made much research on abrasive jet polishing process. Much research has been made on AJP process; there are little attentions been paid to the material removal mechanism. Combined with theoretical analysis and CFD simulation, the material removal mechanism of AJP process is deeply studied in this study. Collisions result in shear stress between abrasive particles and work piece under the actions of impact press P and horizontal velocity V. When the shear stress is big enough, it will remove the material of the work piece directly
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