modern tooling machines for mold making generally feature multiaxial CNC controls and highly accurate positioning systems. the result is higher accuracy and greater efficiency against rejects. Nowadays, heat-treated workpieces may be finished to final strength, up to 2000MPa, by milling. Various operations, e.g. cavity sinking by EDM, can by replaced by complete milling operations and the process chain thus shortened. Furthermore, the thermal damage to the outer zone that would otherwise result from erosion does not occur. hard milling can be used both with conventional cutting-tool material, such as hard metals, and with cubic boron nitride(CBN). For plastic injection molds. Hard metals or coated hard metals should prove to be optimum cutting-tool materials. Machining frees existing residual stresses which can cause distortion either immediately or during later heat treatment. It is advisable, therefore, to relieve stresses by annealing after roughing. Any occurring distortion can be compensated by ensuing finishing, which usually does not generate any further stresses.
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