direct pressing blanks of optical glass
direct-press blanks are directly dropped and pressed from melted glass.
tolerances of outer diameters and thicknesses for dp are shown in table 15.
table 15
external diameter of molded blank | direct pressing blank | |
external diatolerance | thickness tolerance | |
＜12 | ±0.10 | ±0.20 |
12~40 | ±0.15 | ±0.20 |
41~60 | ±0.20 | ±0.20 |
61~90 | ±0.30 | ±0.30 |
91~150 | ±0.40 | ±0.40 |
＞150 | ±0.50 | ±0.50 |