| 摘要 |
PURPOSE:To enhance production efficiency by suppressing the loss of a material and the loss of a purge time to a min. degree, by a method wherein a screw is reversely rotated to remove residual resin while involving the same into the next resin material having a different color and, subsequently, the screw is positively rotated to perform the plasticization and injection of the resin material. CONSTITUTION:When a cylinder 2 is almost fully filled with a resin material 10 and a screw 1 is reversely rotated after the retraction of said screw 1, the direction of the transfer force of the resin material 10 is reversed to a rearward direction and molten resin 8 is transferred to the direction of a hopper orifice 6 while contacted with a flight back surface 11''. During this time, the residue of the resin material 10 or a colored powder pigment stayed on the flight back surface 11'' during the previous molding time is involved in the next resin material 10 and removed from the flight back surace 11''. After this reverse rotation is performed for a definite time, the screw 1 is again positively rotated to perform the plasticization and injection molding of a necessary amount and the reverse rotation, the positive rotation and the injection molding are repeated. By this method, the loss of the resin material is minimized and a time for color and material changing can be shortened and production efficiency can be enhanced. |
