Abstract: A displacement-injection molding system utilizes heating transfer elements extending into the cavity of a plasticizing vessel to decrease the time required to heat polymer granules to their injection temperature and a variable volume mold utilizing back pressure to maintain molten polymer injected into the mold under pressure to prevent the formation of voids or pores in the molded product. The heat transfer elements include cylindrical cores having electric heaters mounted therein. The ejection mechanism for ejecting molten polymer from the plasticizing vessel comprises a plunger having openings for receiving the cylindrical cores and passing thereacross.

Abstract: A mold for relatively uniform heating and molding of a work material to form a workpiece using a microwave oven, includes upper and lower mold members and a sidewall mold member. The mold members are formed from materials selected to have an approximately equal effective thermosensitivity. The effective thermosensitivity of work material is its dissipation factor divided by the product of its dielectric constant, density and specific heat. The effective thermosensitivity of the material of mold layer of each mold member is its dissipation factor divided by the product of its dielectric constant, density, and specific heat and multiplied by the fraction of the mass of its mold layer divided by the total mass of this mold member. A metal sleeve is formed on an inner surface of the sidewall mold member with microwave absorbing material formed on the outside thereof and inner surfaces of the end mold members may also be coated with metal or other highly thermally conductive and wear resistant material.

Abstract: Injection molding machine utilizes microwave heating. A microwave oven adapted to receive a microwave absorbent plasticizing vessel is utilized with or incorporated into an injection molding system to form a plasticizing unit for heating polymer granules to an injection temperature and injection of the melt into the cavity of the injection mold. The polymer granules may be preheated by conventional heating systems to a temperature at which the granules become microwave absorbent before heating to the injection temperature in the microwave oven. The injection molding machine also contains a hydraulic actuator for injection of the melt. The ceramic materials forming the plasticizing vessel are selected to provide equal heating rates of mold members and relatively uniform heating of polymer to desired injection temperature.