Pneumatic thermoforming of plastic products involves additional heating of local areas with radiant heating source

摘要

A sheet or film(3) of thermoplastic material is clamped in a tool(1), heated and thermoformed using either positive or negative pressure. In selected areas(T) the plastic is additionally subjected to radiation(15) which increases the temperature before and/or during the thermoforming stage to control local stretching of the film or sheet. Radiation is provided by a laser beam(15), preferably a pulsed infra-red laser beam and more particularly a carbon dioxide laser(16). The beam is directed onto specified areas(T) of the plastic sheet(3) by a fast acting optical beam diverting system(19). Following container forming the beam may be employed to form a consolidated edge(B) to the container. Sensors(22) measure the sheet properties, in particular temperature and thickness, in the specific areas. An independent claim is included for the process equipment which includes a radiant heater(14) for localized heating of the film or sheet.