| 摘要 |
PURPOSE:To easily prevent ununiform thickness from developing in an extrudate with simple constitution by a method wherein a die is made possible to control by shifting in the radial direction of a die port. CONSTITUTION:A first annular gap 16 is formed between a mold main body 4 and the fore part of a mandrel 9. In addition, a die port 21, which connects to the inner port 5 of the mold main body 4, in a die 20 provided on the front end side of the mold main body 4. The front end of the mandrel 9 locates in the die port 21. A second annular gap 22, which connects to the first annular gap 16, is formed between the mandrel 9 and the die 20. Material to be formed, which is pushed in the first annular gap 16 by an extruder main body 1, is forced in the second annular gap 22 so as to be formed into a circular pipe at the second annular gap 22 in order to be extruded outside a mold 2 in such a manner as to cover a core material by passing through the second annular gap 22. In this case, by shifting the die 20 for controlling, ununiform thickness can be prevented from developing in the circular pipe P. |
