摘要:
A tubular article with a closed end is formed from a thermoformable polymer material, e.g. a high molecular weight saturated linear polyester such as polyethylene terephthalate, by forcing a punch (21) through the plane of a pre-heated and clamped sheet (13) of the polymer, centrally within an annular die (10) so as to draw the sheet into tubular form without exerting compressive stresses on the sheet between the punch and die, the punch being maintained at a temperature below the glass transition temperature of the polymer, e.g. by passing cooling fluid through internal passages (16), and being moved at a speed of at least 1/2 meter per second to effect the drawing. The punch head (21) may be convex or concave to produce a shaped closed end on the article, e.g. for making a pressure-resistant container, and the punch may co-operate with a shaped movable anvil (201) at the end or at an intermediate point in its stroke. Replaceable annular spacers (24) can be used to adjust the point in the punch stroke at which it co-operates with the anvil.