High strength hot plate pressure butt welding of plastics profiles - by pinching molten flash after welding with blunt blades and forming upset material back on either side of the weld

摘要

Plastics profiles are first welded by thrusting together the heated ends with free displacement of material to form flash. After a time delay, but before the flash solidifies, blunt knife-like blades are forced together, close to the outer surface of the profiles, leaving a small gap (m) for the flash, and forcing back the `upset' material either side of the weld flush with the original surface contour. This operation is completed during the time in which the material viscosity in the centre of the weld is less than that towards the inner surface,, so that the latter part supports the material displaced by the blades. The inner, unseen, surface is undistrubed. ADVANTAGE - Improves compaction of weld material. Increases weld strength but with min. finishing. Improves weld appearance and avoids sink marks