Utilization of Secondary Jet in Cavitation Peening and Cavitation Abrasive Jet Polishing

The cavitation peening (CP) and cavitation abrasive jet polishing (CAJP) processes employ a cavitating jet to harden the surface or remove surface irregularities. However, a zero incidence angle between the jet and the surface limits the efficiency of these two processes. This limitation can be improved by introducing a secondary jet. The secondary jet interacts with the main jet, carrying bubbles to the proximity of the workpiece surface and aligning the disordered bubble collapse events. Through characterizing the treated surface of AL6061 in terms of the hardness distribution and surface roughness, it was found out that the secondary jet can increase the hardening intensity by 10%, whereas the material removal rate within a localized region increased by 66%. In addition, employing multiple secondary jets can create a patched pattern of hardness distribution. Another finding is that the hardening effect of the cavitation increases with the processing time at first and is then saturated.

Constrained Abrasive Jet Polishing with a Tangentially Aligned Nozzle Shroud

In order to improve surface polishing quality and efficiency for hard and brittle components, a novel nozzle with specifically designed shroud was proposed for an abrasive jet polishing process. The removal mechanism of the abrasive jet under such a nozzle was investigated by simulating the jet flow in the interaction area of the nozzle shroud and workpiece. The simulation results show that the speed of the abrasive jet increases greatly by the shroud and the direction of the jet is aligned near parallel to the workpiece surface to minimize impact damage to workpiece surface. The constrained abrasive jet polishing (CAJP) experiments were conducted on the quartz glass component, a typical hard and brittle material, showing that the material removal mainly relied on the shearing and scratching of the workpiece surface rather than the mechanical shock impacts, which is consistent with the simulation findings.

Application of taguchi method to investigation of optimal abrasive jet polishing parameters

The surface finish of N-BK7 optical glass is improved by abrasive jet polishing (AJP) process. Taguchi’s method is employed to investigate optimal AJP parameters. The important parameters that influence the N-BK7 surface finish are determined by Analysis of variance (ANOVA). The optimal parameters are found based on Taguchi’s experimental results and signal noise ratio (S/N). These optimal parameters are: polishing time of 45 min, pump pressure of 5 kgf/cm2, standoff distance of 12 mm, abrasive grain type of Al2O3, abrasive grain concentration of 20 %, and impact angle of 40°. The surface finish (Ra) of the N-BK7 is improved significantly from 0.350 µm to 0.018 µm.

Material Removal and Application by Chemical Impact Reaction in Nano-Abrasive Jet Polishing

Material removed by mechanical process inevitably causes surface or subsurface damage containing cracks, plastic scratch, residual stress or dislocations. In nano-abrasive jet polishing (NAJP) the material is removed by chemical impact reaction. The chemical impact reaction is validated by contrast experiment with traditional lap polishing process in which the material is mainly removed through mechanical process. Experiment results show the dependence of the abrasive particles on the choice of materials. Even if the abrasive particle and the workpiece are composed of similar components, the machining properties are remarkably different due to slight differences in their physical properties or crystallography etc. Plastic scratches on the sample which was polished by the traditional mechanical process are completely removed by NAJP process, and the surface root-square-mean roughness has decreased from 1.403nm to 0.611nm. The NAJP process will become a promising method for ultra precision machining method for ultrasmooth optical surface.

The Investigation of Abrasive Jet Polishing on the Linear Micro-Channels Surface of SKD61 Mold Steel

This study examined the performance of abrasive jet polishing (AJP) on SKD61 mold surfaces using wax-coated SiC abrasives fabricated by gas atomization and the comparison of surface quality achieved by revealing significant surface roughness reduced with wax-coated abrasives. The wax coating of SiC abrasives smooth the sharp surfaces of abrasive powders and provides a cushioning buffer. These two features contribute and improve the direct impact of heavy peening, thus preventing surface hardening, superficial embedment or deep scratches. Furthermore, compound additives including water wax and water were added to the wax-coated #3000 SiC abrasives at a mix proportion of 500: 1000: 1500 (water wax: wax-coated SiC: water) for polishing micro-channels surfaces. The experimental results show that the compound additives provide addition cushioning effect facilitate the sliding and grinding of abrasives, resulting in fine polishing and good surface quality. The reflection properties of both linear and curved micro-channels were much enhanced by AJP using wax-coated #3000 SiC abrasives with the compound additives.