Faster surface finishing with shape adaptive grinding plus ceria

Abstract

Shape adaptive grinding (SAG) is a well-established approach to obtain optical smooth quality on hard ceramic and metallic surfaces. However, the process has been limited to low material removal rate (MRR) when already smooth surfaces are processed using SAG pads. In this work, shape adaptive grinding plus ceria (SAG+) is put forward as an effective approach to increase the MRR, whereby ceria is used as polishing slurry and enables softening of glass/glass-ceramic surfaces through chemical reaction and enhances subsequent material removal through mechanical action of the SAG pad. A macroscopic material removal model is established for SAG+ process on BK7 glass where the effect of ceria on the surface hardness correlates well with the material removal rate. Experiments were performed on BK7 glass with different grades of resin bonded diamond SAG tools to benchmark performance against the standard SAG process. It was observed that the material removal rate increased by 3.5–10 times for SAG+ when all other conditions remain the same. It was also determined that removal rate increases most drastically when the abrasive grit of SAG pad and ceria slurry are of comparable size. Lapped Zerodur™ samples were also processed to check the applicability in pre-polishing of rough glass-ceramic surfaces. A reduction of almost 50 % could be obtained in processing time when using the SAG+ process.