PREVENTING METHOD FOR FLOW MARKS IN INJECTION MOLDING

PURPOSE:To improve a productive efficiency without the need for providing a flow pin in a mold and uniformize the flow of a resin material by disposing an electromagnet in the mold and performing the injection molding of the resin material in which metallic powder is mixed, while supplying power to the electromagnet. CONSTITUTION:An electromagnet 21 is disposed in a predetermined place in a cavity 12, and a magnetization-proof part 22 is formed around the electromagnet 21. Further, a resin material is composed of metallic powder 23 susceptible to magnetization and resin particles 24, both being mixed together. The resin material cast through a runner 16 passes through a gate 14 and is injected into a space 13 defined by a core 11 and the cavity 12. In this case, when power is supplied to the electromagnet 21 to generate a magnetic field, the resin particles 24 are also apparently attracted to the magnetic field as the metallic powder 23 is attracted to the magnetic field, because the metallic powder 23 susceptible to magnetization is included in the resin material injected, and it appears that the resin material itself is being attracted to the magnetic field. The resin material is thus attracted to the magnetic field, and the concentration of the local flow of the resin material can be eliminated, thus preventing flow marks which may be caused by injection molding from being generated.