Finishing Guide

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.

P3 Lacquer YP


Unfinished sample on top.P3 Lacquer vs Non Finished SLA 7870

Polished sample, left.P3 Lacquer CRDM

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.

SLA 7870 C3 vs No Finish