| 摘要 |
PURPOSE:To guarantee the strict curvature radius and bending angle and increase the manufacturing efficiency by pressure molding a heated plastic straight tube by means of a mold having the curvature radius smaller than the given curvature radius and the bending angle larger than the given bending angle, cooling the same to the temperature in the middle up to the normal temperature and releasing, and then carrying out final pressure molding in a mold having the curvature radius and bending angle equal to the given ones. CONSTITUTION:The curvature radius R1 of a molding channel of a mold 1 for intermediate molding is smaller than the given curvature radius R of a product bending tube A, and the bending angle theta1 is larger than the given bending angle theta, and R1theta1= Rtheta. The curvature radius R2 and the bending angle theta2 of the molding channel of a mold 2 for final molding are equal to R and theta. First, a plastic straight tube filled with a filler such as sand is heated and set in the mold 1 for intermediate molding and cooled, and then the plastic tube P1 is released. Bending is restored to the original substantially at the same time with releasing, and the curvature radius R' and bending angle theta' of the plastic tube P' is R')R1 and theta'(theta1. The tube is set in the mold 2 for final molding, pressure molded and cooled, and R2 and theta2 of a molded plastic tube P2 is set equal to the final R and theta. |
