| 摘要 |
PURPOSE: To enable manufacture of a die element which is shaped in approximation to an accurate die gap necessary for a desired distribution of the wall thickness of a product to be formed by blow and inflation, on the basis of a method for shaping which can be preestimated, by computing a die gap width as a function of positions around the die gap from the desired distribution of the wall thickness in the sectional shapes of given molds. CONSTITUTION: The distribution of the wall thickness T1 of a parison formed by blow and inflation in molds having given sectional shapes is computed from the sectional shapes of the given molds 1 and 2 and the parison extruded with a prescribed wall thickness. This computation is only based on the assumption that the parison has a minimum surface area in regard to a given volume possible to have in the molds 1 and 2 and also on geometric considerations. From this computed distribution of the wall thickness, subsequently, a bias from a desired distribution of the wall thickness as a function of the position of each wall part on the parison, on a die accordingly, is computed. Then, at least one of die elements is shaped so that the parison extruded from the die shaped in this way may have such a wall thickness as approximated at a given azimuthal position to the desired distribution of the wall thickness in the molds after the blow-inflation forming. |
