length of the pass. The latter should not be more than 10% greater than the length of rod used.
Correct handling of the welding gun is of utmost importance. Fanning motion of the round tip for hand
welding should be continuous and at the correct distance from the work, for proper heating of rod and
base material. The travel of the welder across the weld bed should be fast and with a decisive motion,
with no hesitancy once the weld has been started.
WELDING GASES
In hot-gas welding of polyethylene and other readily oxidizable plastics, an inert gas such as nitrogen is
used as the heat-transfer medium. The water-pumped grade of nitrogen is recommended. Compressed
air is completely satisfactory for carrying heat to PVC.
PLASTIC WELDING ROD
The simplest type of plastic welding rod or filler rod is a strip cut from a sheet of the plastic to be welded.
The most common type of welding rod furnished commercially is extruded round rod available in various
standard diameters. It is available in lengths of approximately 60 inches. It is also available in triangular or
oval shapes, for specific applications. The welding rod should be of a size to permit a minimum number of
passes for any material thickness. An overlap of the beveled edges by the welding rod is essential to
produce a good weld.
The welding rod should be cut to a length to suit the actual welding requirements. A few inches extra
length for final trim should be allowed.
Flexible welding rod is usually coiled, and cut to requirements.
HEATED-TOOL WELDING
Heated- tool welding is a evolution from the art of heat -sealing thin plastic film. It consists of
the use of a heated tool or fixture to bring the plastic to the fusion temperature.
Heat is applied directly to the surface of both plastic pieces to be joined. The plastic is kept in contact with