Evolution of roughness parameters along polishing tests of previously ground surfaces
In polishing tests, precise determination of polishing time needed is difficult, since representation of 
surface roughness against polishing time leads to an asymptotic curve. In the present work, results of 
the polishing tests of previously ground surfaces are presented. Different roughness parameters were 
considered. Grinding wheels of 100 and 150 Norton grain size respectively were used. Cutting speed 
was 25 m s-1 and depth of cut was 0.02 mm. Two different feeds were considered: 9 m min-1 and 15 m 
min-1. A polishing test was performed by means of corundum polishing pads of grain size 2500. 
Results show that, the higher the initial grain size of the grinding wheel, the higher initial roughness is 
as expected. Amplitude roughness parameters such as Ra and Rq decrease with polishing time. 
Regarding material percentage parameters, Rk and Rpk decrease more sharply than amplitude 
roughness parameters in the first 20 s of the polishing test, and afterwards decrease slightly. Rvk 
decreases more slowly than amplitude roughness parameters along the polishing test. 
Keywords: grinding, polishing, roughness parameters
Semi-Ductile Grinding and Polishing of Ophthalmic Aspherics and Spherics*
Abstract Ductile grinding yields surfaces whose precision is far beyond that expected of ophthalmic requirements. This process requires machine tools and cutting tools that are manufactured to sub micron tolerances and which require clean rooms, thus making its cost prohibitive. While fracture mode grinding, followed by lapping and polishing have been successful, this paper presents results of semi-ductile grinding that is followed by reduced polishing time without an intervening lapping operation. Using conventional CNC machining centres and/or dedicated machines, silicon, germanium and glass were ground by metal bonded and/or diamond bonded diamond wheels followed by conventional polishing techniques.
Rapid post-polishing of diamond-turned optics
Abstract A simple technique for post-polishing single-point, diamond-turned optics is described. Synthetic fabric-faced laps are used. Surface finish converges to a limiting value set by process parameters. Lap construction and diamond grit size affects both convergence rate and ultimate finish.