Manufacturing structured tool inserts for precision glass moulding with a combination of diamond grinding and abrasive polishing

摘要

This paper presents the successful introduction of a novel process chain for manufacturing structured tool inserts for precision glass moulding operations, Fig 12. The manufacture of a mould insert with cylindrical lens array geometry by precision diamond profile grinding and abrasive profile polishing is shown. Metal bonded fine grained diamond grinding wheels can efficiently be used for precision profile grinding of filigree structured mould inserts in highest form accuracy. The resulting surface quality in the range of 40 nm R_a depends on the grit size and on the grindjng kinematics. Wire electro discharge machining can successfully be used for trueing and dressing of the grinding wheels. By abrasive profile polishing the roughness of the cylindrical grooves can be improved to optical quality. The results from experiments with tungsten carbide show a significant improvement comparing to the pre-ground surface quality. Therefore, this polishing process is applicable in optical mould making to increase the quality of replicated structured glass lenses. Precision glass moulding can directly replicate filigree micro structures in high form accuracy and surface quality in glass parts. Thus, the whole process chain is capable to efficiently produce optical glass parts in serial or mass production.