With this the heated tool or hot plate method, the surfaces to be fused are heated by holding them against a hot metal surface (232 to 371°C); then the parts are brought into contact and allowed to harden under slight pressure (5 to 15 psi). Electric strip heaters, soldering irons, hot plates, and resistance blades are common methods of providing heat. Heated platens are generally employed to create a molten or plasticized region. Thus, this form of welding is often called "hot-plate welding".
One production technique involves butting flat plastic sheets on a table next to an electrical resistance heated blade that runs the length of the sheet (Figure 1). Once the plastic adjacent to the blade begins to soften, the blade is raised, and the sheets are pressed together and held under pressure while they cool. The heated metal surfaces are usually coated with a high temperature release coating such as polytetrafluoroethylene to discourage sticking to the molten plastic.Heated tool welding can be used for structural plastic parts, and heat sealing can be used for plastic films.