APPARATUS AND METHODS FOR TWIN SHEET THERMOFORMING

摘要

A method of twin sheet thermoforming is provided in which the seam (1) between sheets (7, 8) is trimmed from the finished part by a shearing action between cooperating edges of the mould halves (3, 4). In the preferred from of the invention one mould half (4) is provided with a moveable pinch-off region (13) which retracts under pressure from the other mould half (3) to leave an edge of the mould half (4) adjacent the mould cavity which cooperates with an edge of the mould cavity of the other mould half (3) to provide the shearing action. The moveable pinch-off region may be a pinch-off member (13) supported in an annular channel (14) by a pre-compressed spring (15). The invention allows significant plastic displacement of the material in the seam region for weld reinforcement along with trimming of the seam from the formed part within the mould in a one step process.