| 摘要 |
PURPOSE:To obtain an injection molded product having a good and smooth surface, no stratified peeling and excellent physical properties, by setting a volume of a cavity at a specified magnifications of the final volume of the molding, injection molding at a lower speed than a specified speed until a specified injection stroke and at a higher speed thereafter, opening the cavity and finally pressing the molding. CONSTITUTION:The volume of the cavity of a mold is set at 0.8 to 1.5 times of a required volume of injection before injection molding. The 1st injection speed is set below 50000sec<-1> of the shearing speed at the cavity gate. The stroke at the 1st injection speed is larger than 1/5 and smaller than 3/4 of the whole stroke. The 2nd injection speed is larger than the 1st one. The volume of the cavity becomes from 0.8 to 1.5 times to 1.2 to 2.0 times of the required volume after or during injection by the injection pressure or a pressure from the outside. Compression is carried out at the compression stage to the injection volume and the molten ultra-high molecular weight polyethylene is thereby brought to an one body by re-adhesion in molten state and the voids contained inside is completely removed. |
