| 摘要 |
PROBLEM TO BE SOLVED: To form a pipe having a correct inside diameter size by forming a blind-shaped hole part at the end of a mandrel. SOLUTION: A mandrel 4 has a straight part 7 and a base end boss part 8, on its end face 4a is formed a blind-shaped hole part 5 with a circular cross section, and the hole part 5 decreased the temperature of the end part of the mandrel 4 by heat conduction from the extruder side. By the formation of the hole part 5, the heat capacity of the end part of the mandrel 4 is reduced so that heat is apt to be lost by the flow of a resin to decrease the temperature of the end part of the mandrel 4. As a result, the temperature of the inside surface of a molded pipe P is decreased sufficiently so that the resin is prevented from being caught up inside when it passes through the mandrel 4, enabling the formation of the pipe P having a correct inside diameter size. |
