Blemishes from Tooling
A successful MIM part design allows for locating the parting line, ejector pin marks, witness lines, and gate in non-critical areas. Often the gate is located on a parting line, so these two blemishes go hand-in-hand. Parting lines can be placed along component edges to reduce visibility. Sometimes features within the mold set are inserted to allow changes, replacement, interchangeability, and servicing. These inserted components will leave witness lines where they blend into the parent part surface.
Early in the design process, the designer needs to consider placement of these blemishes in areas where they will not detract from the function or aesthetics. Alternatively, the gate can be removed by grinding or polishing after molding, but prior to de-binding and sintering, since the material is easily removed then.