Abstract: A displacement-injection molding system utilizes a plasticizing vessel with cylindrical heat transfer cores extending into the cavity of the plasticizing vessel to efficiently heat polymer granules to their injection temperature and a variable volume mold utilizing back pressure to maintain the injected polymer under pressure. A plunger for ejecting polymer from the plasticizing vessel incorporates openings for receiving the cylindrical cores. The plasticizing vessel is preferably sized to receive at least two shot sizes of polymer material to permit continuous heating of the granules of plastic material between shots as additional granules are added to replace the ejected material.

Abstract: A displacement-injection molding system utilizes a plasticizing vessel with cylindrical heat transfer cores extending into the cavity of the plasticizing vessel to efficiently heat polymer granules to their injection temperature and a variable volume mold utilizing back pressure to maintain the injected polymer under pressure. A plunger for ejecting polymer from the plasticizing vessel incorporates openings for receiving the cylindrical cores. The plasticizing vessel is preferably sized to receive at least two shot sizes of polymer material to permit continuous heating of the granules of plastic material between shots as additional granules are added to replace the ejected 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.

Abstract: A mold for uniformly heating working material to form a workpiece using a microwave oven. Uniform heating of a workpiece of variable thickness may be obtainied in a microwave oven with a uniform electric field in its cavity if the mold material is selected to have a dielectric constant and a thermosensitivity equal to that of the working material. The thermosensitivity of a material is its dissipation factor divided by the product of its density and specific heat. Uniform heating of a uniformly thick workpiece can be obtained in a conventional microwave by selecting the mold material to have a relative thermosensitivity equal to that of the working material. The relative thermosensitivity of a material is its dissipation factor divided by the product of its dielectric constant, density, and specific heat.

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: A mold for uniform heating and molding of work material to form a workpiece of variable thickness using a microwave oven includes upper and lower mold members and a sidewall mold member. Metal inserts, with irregular inner surfaces defining a mold cavity, are positioned adjacent opposed planar surfaces of the upper and lower mold members. The mold members are formed from material selected to have an effective thermosensitivity equal to that of the work material. The effective thermosensitivity of work material is its dissipation factor divided by the product of its dielectric constant, density and specific heat multiplied by the fraction of the mass of work material divided by the total mass of work material and metal inserts.

Abstract: An RF heating apparatus and method utilizing a mold positioned between a pair of electrodes across which an RF field may be applied to heat working material in a cavity of the mold. The material used to form the mold is selected such that its dielectric constant and parameter of thermosensitivity to an RF field are equivalent the dielectric constant and parameter of thermosensitivity to an RF field of the working material to achieve relatively uniform heating of said working material to a selected temperature. The parameter of thermosensitivity to an RF field of a material generally comprises its power factor divided by the product of its density and specific heat, tan &dgr;/c&rgr;.