Increasing use is being made of EDM techniques to apply finishes to molding surfaces instead of using photochemical] etching. This is a relatively new departure that has come about in an attempt to reduce the time and cost associated with the photo-etching process.
Electrodes are becoming available from specialist suppliers in a limited number of patterns and textures for this purpose. There is much debate at the moment about which process gives the better result, but EDM is gaining in popularity and will probably become a major rival of photo-etching in the future.
This procedure involves firing small beads of plastic and other materials in a high- velocity air stream at the surface of the area to be textured. The results vary from a quite coarse sand-blast steel effect to a very fine almost polished finish. Plastic bead blasting is beginning to be used to impart a ‘grip free’ surface to EDM fine sparked finishes to assist in part removal from the cavity
This process consists of directing high-velocity liquids, with or without any particles being present. Again, as a specialist process this is not usually undertaken by the mold manufacturer. Vapor blasting is not new but it can be useful in imparting a very fine matt finish to surfaces and is sometimes preferred to EDM finishes. It can be used successfully to disguise poor molding defects such as sinking and flow lines.