PLASTIC INJECTION MOLD, AND PLASTIC INJECTION MOLDING METHOD USING THE MOLD

摘要

PURPOSE: To shorten molding time by a method wherein the value of the surface resistivity of a skin film resistor is set within the range given by the formula in a plastic injection mold, in which a thin film electric resistor is formed on the molding wall surface of a cavity, and it is energized to heat the molding wall surface. ;CONSTITUTION: A thin film electric resistor 10 is formed onto the surface of the surface of a cavity 5 constituted by a fixed type insert 3. The thin film electric resistor 10 is connected in a conical recess 11 provided on the surface extended from a cavity type wall surface to an electric connection bolt 13a having a conical stepped part 12 to power source. The value of the surface resistivity (γ) of the thin film electric resistor 10 is set to the value within the range given by the formula, in which L is the length of the thin film electric resistor lying between electric connecting parts, D is the length of the thin film electric resistor lying in the direction normal to the line connecting between the electric connecting parts of electric wire, Va and Ia are maximum voltage and current applied between the electric connecting parts and Wr is the electric input per unit area of the thin film electric resistor required from the temperature rising speed of the molding wall surface.;COPYRIGHT: (C)1995,JPO