Using the electric plastic welder

Press, 14 May 1981, Page 13

Using the electric plastic welder

With the ever-increasing use of plastics in car bodies (up to 38 per cent in some), the use of electric plastic welders has become more important in repair shops, and even by the home handyman.

The Seelye plastic welder is proving itself particularly popular because of its ease of use and because it has been found less costly than car replacement parts. It will weld all types of car body plastics (grilles, fender skirts, fan shrouds, instrument surrounds) and can also be used to weld motorcycle and lawnmower plastic parts. Welding plastic is very much like welding metal. Yet, there is a definite knack, or feel, that must be learned.

Whether using the tacking tip. round tip or high-speed welding tip, you will need to practise. Most people get the •‘feel” of proper plastic welding in a . few hours. All welding tips should be screwed into the welder with pliers; tips should not be over-tightened but should fit snugly. The Seelye tack welding tip is an invaluable aid in the welding of plastic automotive parts. Tacking allows you to check for proper match and alignment of all pieces to be welded.

It also serves to hold damaged sections together during actual welding and is ideal for use in preparing long cracks. Tack welds can easily be broken apart without damage and can be retacked if necessary. In tack welding, draw the point of the tip firmly along the joint to be welded, pressing evenly on both sections. The point of the tip will fuse a thin line along the joint at the root gap to form a small hinge and help insure a uniform weld later. Tack welding should be done along the entire length of the joint.

1. Typical damage caused to a front tender skirt in a collision. The material is polypropylene.

2. Use a knife to channel out a groove in broken polypropylene in preparation for tack welding.

3. Use a power hand-grinder to channel out a groove, a faster alternative to using a knife. This is especially good where cracked edges remain in alignment under pressure.

4. Use a hand-power grinder and puli apart the edges of the crack to ensure a proper tacking channel. This is the preferred method.

a. Use a tacking tip to achieve a “hinge bond” between two edges. It may sometimes be necessary to clamp parts together to achieve the best tacking results.

6. Weld using a high-speed tip since the crack is relatively straight and long. 7. Use a round tip for welding cracks that are •• short and have sharp turns. p 8. The finished, welded polypropylene fender skirt using both round and high speed tips. The time taken, including knife or power grinder preparation, was about 30 minutes. 9. The reverse side of the previously welded fender skirt. Use a power brush or sander to remove the undercoating and clean up for cosmetic purposes. 10. Speed tip welding on the reverse side of the fender skirt after making a channel with a knife or hand grinder. 11. To finish, sand off excess rod, and paint with flat black paint or undercoating. Use steps 9, 10 and 11 when necessary. _______