Optimization of the continuity of the aspherical production processes in asphericon s.r.o based on subsurface damage and microroughness analysis

In the paper is presented an analysis and optimization of the standardized sub-apertural grinding process used in the serial production in asphericon s.r.o. The monitored parameter was the depth of subsurface damage and surface microroughness. Tested were five grinding processes, which were automatically generated by the internal system, for five different diamond grit sizes (D151, D91, D64, D30, and D15). For evaluation of the depth of the defected layer was used modified wedge polishing method which is suitable for analysis of the rotationally symmetrical sub-apertural grinding processes [1]. For identifying the presence of the subsurface damage two methods were used. Defect detection using an optical microscope, as the broadly used and reliable method, and detection by standard ISO control to get the comparison with the method used in common serial production. The microroughness was measured using a white-light microscope concerning the used grinding tool and the amount of removed material. Within the experiment was found as the most effective two-step process uses D91 for rough grinding and D30 for fine grinding. D91 provides a very good removal characteristic with final subsurface damage of 44 µm which is possible to grind out using the D30 tool in two steps with final subsurface damage 22 µm in a total processing time of 137 minutes. This grinding process is timewise in best balance with 80 minutes long polishing process and therefore minimize the production cost. Result microroughness around 2 nm Sq in the fully polished zone is already limited by the polishing process. Using a finer grinding tool is not bringing improvement in the surface microroughness just shortening polishing time due to lower subsurface damage