|
8.1 Raw Glass |
8.1.1 Strip Glass Strips
are made by drawing glass out of a continuous flow furnace. Strips
are rectangular in shape, have slightly rippled fire-polished
surfaces, (unworked) and are flame cut to required lengths. The
corners are radiused. Strips are coarse or fine annealed. This is
the least expensive form of supply. |
| 8.1.2 Slab Glass Slabs
are blocks or rectangles of raw glass that have been ground on all
sides and then polished on two opposite sides for inspection.
Generally, slabs are fine annealed. |
| Thickness 15 ~ 40mm
Width and Length 50 ~200mm |
|
8.2 Pressings (Reheat Pressings (RP))
Reheat or hand pressings (RP) are blanks formed by
manually pressing softened glass. We urge the customer to specify
the following: |
1 ) Diameter (including
grinding stock) |
2 ) Center Thickness (including
grinding stock) |
3 ) Radii of
curvature |
4 ) Glass quality (striae,
bubble, etc.) |
>5 )
Bevel |
6 ) First processing
side |
|
Dimensional tolerances are given in Table 1. |
|
Pressing large
blanks over 300mm in diameter or of an excessive thickness is
difficult. Such large blanks are gravity molded. Blanks made by this
method are generally supplied plano-plano. However, we can produce
large plano-convex or plano-concave moldings. |
|
Table1 |
| Diameter |
Thickness |
Diameter |
| Φ18mm |
±0.5mm |
±0.10mm |
| Φ18~30 |
±0.4 |
±0.15 |
| Φ30~50 |
±0.4 |
±0.20 |
| Φ50~100 |
±0.3 |
±0.30 |
| Φ100~150 |
±0.3 |
±0.40 |
| >Φ150 |
±0.4 |
±0.50 | |
|
8.3 Saw cut
Centerless Ground Cylindrical Blanks |
These blanks are cut from a precisely ground rod
formed on a centerless grinding machine.
This process is very
useful for making lenses that: |
|
1 ) Are small in diameter but quite thick. |
2
) Are small in diameter with shallow radii. |
3
) Are such that the precise blank dimension can eliminate lens
centering operations. |
4
) Can utilize precision spot blocks. |
|
Diameter range of these blanks is 3 mm to 20 mm and
the dimensional tolerances are given |
Table 2 |
| Product Size |
Thickness |
Diameter |
|
Φ3~20mm |
>±0.15mm |
±0.015mm |
|
|
8.4 Cut Blanks, Polished Blanks and the
other |
Cut discs, cut
rectangles, and cut prisms are blanks that are cut or core drilled
from annealed strips or slabs. These forms are generally specified
when delivery is urgent and quantities are small. |
