| 摘要 |
PURPOSE:To assure the quality of molded products by forming a part of a screw with a material having low thermal conductivity in a molding machine equipped with an extruder comprising a barrel and a screw which is accommodated in the barrel and driven to rotate. CONSTITUTION:A screw 22A for use in molding a low density polyethylene tube comprises a screw mainbody 221 and a torpedo part 222 as a measuring part. The screw mainbody 221 is made of carbon steel for mechanical structure, while the torpedo part 222 is of ceramic. The ceramic torpedo part 222 is fixed with screws at the head of a cooling hole 22a which is formed in the screw mainbody 221. The seramic adopted in the torpedo part 222 has a value of thermal conductivity about 1/18 as compared with that of carbon steel for mechanical structure. As a result, the torpedo part 222 is hardly affected by cooling, preventing the deterioration of resin due to retention caused by the decrease in flowability by cooling. |
