Partial-Ductile Grinding and Reduced Polishing for Ophthalmic Glass Molds

Abstract

Plastic lenses are manufactured by the classical replication technique where two glass molds are assembled in a jacket and liquid plastic is injected into it. The glass molds are fabricated conventionally by fracture mode grinding, followed by lapping, and Finally polishing. This paper presents an alternative fabrication process using partial-ductile grinding, followed by a short polishing in an industrial polishing machine. The partial-ductile surfaces were generated on a laboratory ultra-precision machine using Fine grit resinoid-bond diamond wheel and they were compared to the glass molds prepared by industry. The results showed that (i) as much as 100% ductile streaks (fully ductile grinding) can be obtained in the ultra-precision ground surface and (ii) a net saving of 55 seconds polishing time if only 60% of ductile streaks on the glass mold surface was used prior to polishing.