Polishing-grinding - an innovation for manufacturing of high precision optics

ELID-grinding (ELID = Electrolytic-In-Process-Dressing) is mainly used for reproductive components as moulds or single items and prototypes. In this field, several iterating grinding passes with depths of cut of a few micrometers are acceptable. It is hardly found in industrial series. ELID-grinding is mainly used for reproductive components as moulds or single items and prototypes. In this field, several iterating grinding passes with depths of cut of a few micrometers are acceptable. The voltage generated between anode and cathode electrolytically decomposes the grinding fluid, generating hydroxyl ions. These ions OH- are then attracted to the positive charged component (grinding wheel), being processed and resulting in the formation of a stable oxidized layer there. The ELID-process is using a pulsed current. The duty ratio can be varied between 0% (no ELID) and 100% (continuous current). The higher the duty ratio the 'stronger' the electrochemical wear and oxide layer buildup at the grinding wheel. A thicker oxide layer implies a high rate of loose abrasives bound within the soft surface layer which cause. ELID-Grinding offers a new approach for the grinding technology. It allows the stable employment of grinding wheels with very small grit sizes below 7 micron in diameter. However, material removal mechanism are more diversified than in any other conventional grinding process. It is a combination of many mechanism which can be found in grinding as well as in polishing processes. Within this paper two major mechanically based removal mechanism have been discussed. Still under investigation is the chemically induced influence of ELID on the material removal process. The ELID technology has shown an impact on steel, metal carbides and ceramics. The highest influence however could be seen on optical glass. Future work will focus in particular on the polishing behavior - mechanically and tribochemically - of the formed oxide layer within the ELID-process.