To help define the finishing level for a part, CRDM works to a finishing specification system. This ensures that the work is charged for correctly and gives the best value for the customer.
All finishing specifications are made up of 2 parts:
- “A” Surface Finish – visual or important face, typically the outside of a part
- “B” Surface Finish – unseen face of part, usually the inside
The finish grade must be defined for both the “A” and “B” surfaces of a part as below:
| “A” Surface | “B” Surface | Definition |
| C | 3 | Support removed and grit blasted. Support should be removed as thoroughly and neatly as possible without resorting to using wet & dry. There will be evidence of support structure on SLA parts in the form of pimples and stair stepping. |
| B | 2 | Support removed, surfaces sanded with wet & dry, grit blasted. Traces of support are not visible, stair stepping can be visible. |
| A | 1 | As above with additional sanding and grit blasting to produce a smooth surface. Traces of support and stair stepping are not visible. |
| P | P | As above with additional finishing, e.g. painting, polishing, medium spark. Details to be specified and agreed with customer. |
Here are three examples to show the difference between a non-finished SLA sample stick of 7870 material and a polished surface.
Polished sample is on the left, below.
Unfinished sample on top.
Polished sample, left.
The photo below shows the difference of finishes between a non finished part (left) and a C3 part which is lightly bead blasted. C3 will give a smoother, frosted finish. Both parts are made from SLA 7870. There is no difference in price for either finish.
