| 摘要 |
PURPOSE:To restrain the occurrence of distortion particularly in the vicinity of the side portion by cooling, while heating, both sides of the plastic sheet delivered from an extrusion forming mold or a heat treatment machine provided next to the extrusion forming mold, and thus by making cooling uniform both the sides and central portion thereof. CONSTITUTION:A forming process of a plastic sheet is such that molten plastic is extruded from an extrusion machine 1 and then extruded into a sheet form by a mold connected to an outlet of the extrusion machine 1, and further an extruded sheet formed item P is pulled up by a pulling up machine 3. The pulled up sheet formed item P is subsequently heated by a heat treatment machine 4, and the heated sheet formed item P is not immediately placed in a room temperature atmosphere, but gradually cooled as being subjected to heat insulation, to then be sent to a side heater 6. In this manner, cooling in its both side and central portion is made uniform. The side heater 6 is a heater of the type that uses radiant heat, e.g. a far infrared radiation heater. Thereafter, the sheet formed item P is cut into formed items P' with an appropriate length by means of a cutter 7. |
