Are vacuum castings painted or pigmented?
PU vacuum castings are typically used where small batch runs are required and frequently cross the line between prototype and production parts. As such their colour is extremely important and parts are usually supplied to a RAL or Pantone colour code.
Most vendors now pigment the resin and will usually supply a ‘first off’ for approval before running the batch. In extreme cases where a truly exact colour match or a metallic or fluorescent tone is required it may be necessary to resort to painting. (Issues such as texture are incorporated into the tooling, which is usually cast from a finished RP pattern.) Whether this is an issue to worry about is really a function of the application. Clearly if there are wearing surfaces or areas where components are likely to fret, then self colouring becomes a ‘must have’.
Flexible parts can be pigmented across a wide range of colours, but are more constrained than ‘hard’ PU’s due to the resin base colour. There are some clear resins available, however not in all hardnesses, so specific evaluation is required.
If you intend to paint PU parts yourself then it is necessary to ensure any traces of silicone have been removed, otherwise you will have adhesion issues!
For an example of PU vacuum casting, see our case study.