| 摘要 |
PURPOSE:To uniformize surface magnetic flux density, by filling the inside of a molding tool with a mixture by deaerating and melting the same in a state of negative pressure of more than a specific value, in a method for injection molding of a plastic magnet roll. CONSTITUTION:The inside of a molding tool is filled with a mixture by deaerating and melting the same in a state of negative pressure of more than 500mmHg, in a method for injection molding of a plastic magnet roll, wherein the mixture having thermoplastic resin and magnetic powder for its main ingredients is charged to the inside of the molding tool by heating and melting the mixture. In other words, a hopper 5 is closed up tightly after charging of the raw material mixture within the hopper 5, the whole of a system of the hopper 5 and an injection cylinder 1 is made into a state of negative pressure by opening a value 8 and involvement of air or gas in the injection cylinder 1 in the molten mixture is prevented. With this construction, a value of surface magnetic flux density of a plastic magnet roll becomes uniform and linear properties of magnetic force is improved with a leap. |
