Optimizing the cutting processes of mold dies to improve the optical characteristics of Fresnel screens

An experimental study of precision cutting of molding dies using single cry stal diamond cutting tools for large Fresnel screens (size: T3x921x714 mm(3 ), Fresnel angle: 0.004-55.0 degrees), for improving the optical characteri stics of the screens is described. The conclusions are as follows : (1)A bu rr is generated at the shoulder of the grooves during cutting, which causes compressed chip material to accumulate and laterally compress both sidewal ls of the grooves; (2) the burr generation is suppressed by increase of the rake angle of the diamond cutters, decrease of the down feed rate, and red uction of stock removal; (3) generation of a color corn on the Fresnel scre en is caused by light escaping through non-lens surfaces; this is avoided b y making the non-lens surfaces semi-transparent where the surface roughness is around 1 mu m R-max. Using the above-mentioned information to improve t he cutting process, desirable optical characteristics were achieved for Fre snel screens used in projection TVs.