| abstract |
Parts are formed from metal powder by mixing the powder with a plastic medium comprising an organic binder dissolved in a solvent in which it is soluble at room temperature but in which it is substantially less soluble at a higher temperature such that the plastic binder becomes viscous at that temperature. Binder modifiers may be incorporated to promote mold release and promote healing of interfaces within the molded part and prevent the formation of drying cracks. The plastic mixture is injected under pressure into a closed die preheated to the above mentioned higher temperature, whereby the rejection of solvent and increase in viscosity of the plastic medium produces a compact sufficiently self-supporting to hold its molded shape and be ejected from the die. The compact is then dried to evaporate the remaining solvent, thus leaving interconnecting pores in the compact for the escape of gases resulting from subsequent burning out of the binder during the sintering operation. |