Pendulum Welding

Pendulum welding, as shown in the picture below, is one of the most popular forms of hot air welding. As with all plastic welding, weld joint preparation is critical. The joint must be clean and properly shaped for the configuration of the weld. We recommend that all non-PVC thermoplastics to be welded be scraped to remove extraneous debris and surface oxidation. The welding rod is held at the correct angle to the joint groove (90° angle for PVC and 45° for most other plastics). The hot air from the hot air tool is directed at the joint groove and the welding rod in a back and forth action to provide even heating to the joint surface and to a lesser extent to the welding rod. Even, steady pressure (about 2kg of 4½ lbs.) must be applied to the welding rod to ensure a good penetration. Good plastic welding practice requires three elements; proper temperature setting (specific to each thermoplastic, see table), consistent welding speed and even pressure on the welding rod. Using these three elements correctly will result in a slightly foam wash like appearance on the both edges of the weld which should result in good weld penetration and strength. The wash should not be brown or black as this indicates overheating.

Pendulum Hot Air Welding for PVC


Speed Welding

The use of speed welding tips on our hot air tools increases the both the concentration of hot air and the amount of profile welding material that can be deposited in one pass. Generally, welding with this method results in welding speeds up to 15 times faster than pendulum welding. The welding process itself, as shown below, is the same as the pendulum method with the exception that the speed welding nozzle is used to guide the rod onto the welding joint.

Plastics Recognition

Take a small sliver or shaving of the material to be welded and light it with a flame, observe and smell the smoke.