usually for standard pattern on surface we just specify, the moldtech code and supply them with the cad surface without needing to model the pattern on the surface (ex: leather pattern)
but how do you usually specify a custom pattern?
do you give them 2 CAD file? the custom pattern cad and the product cad?
If you are trying to do a custom mold tech texture you have a few options - depending on who your vendor is (IE Mold tech is a universal spec, but many tooling suppliers do not use Mold Tech themselves for texturing):
-Model the geometry into the CAD and then specify the texture that goes on top using a standard MT finish. (Most difficult, but will achieve exactly what you want. May not be possible for certain geometry)
-Work directly with Mold Tech to specify a new custom texture. There are fees and travel expenses associated with this as you need to work in house to understand how they will apply the texture (hand masking, chemical etching, media blasting, etc)
-Laser Engraving - This is a new process and only some vendors will be capable of it - but they can specify the texture by laser etching the tool with data from a CAD file or 2D graphic. This might be your best bet but you’ll need to find a vendor who can do it. Also, you’ll need to make sure that depending on your part, the texture can properly warp around corners or transitions the way you want.