| 摘要 |
PURPOSE:To obtain a blown film die, the adjustment work of which is unnecessary, by a method wherein a mandrel and an outer mold are fitted to each other by shrinking. CONSTITUTION:The inner diameter of a recessed part 16 is slightly expanded by heating an outer mold 14 with heaters 19. A mandrel 1 is inserted in an inner hole 15 from below so as to fit the projecting part 4 of the mandrel to the recessed part 16. When the heating of the outer mold 14 is stopped to restore the inner diameter of the recessed part 16, the recessed part 16 and the projecting part 4 are brought under the slightly-tight-fitted state. A blown film die 20 is assembled by screwing respective set bolts 13 to the internal threads 18 of the outer mold 14. As a result, a resin lead-in passage 17 aligns to the central part of a branch groove 6 and a runner 21 is formed between the tapered surface 3a of the trunk 3 of the mandrel 1 and the tapered surface 15c of the inner hole 15 of the outer mold 14 so as to form an annular slit 22. Consequently, the adjustment work against ununiform thickness becomes unnecessary. |
