New Repair Technologies
Most plastics in todays automobiles are thermoplastics, once heated they can be softened and in this state they can be reshaped after being damaged. Most importantly they can be welded without loss of component strength.
Virtually every automobile today has a variety of plastics in the shape of body panels, headlamps, indicators, grills, bumpers, interior trim panels and mouldings.
The damaged area is prepared by bringing together the broken edges evenly, running a soldering iron with a ' v ' shape tip along the break creating a deep melted groove along the two edges, top and bottom.
This has two advantages, fusing together the edges of the break and creating a deep groove for the plastic rod to be welded in both sides.
A point to make here is the soldering iron must have the right wattage, about 20-30 watts, different size tips are handy too.
Welding rods come in many different plastics, shapes and sizes. The most common shape we use has a V shape with a raised head, this fits snugly into the groove we have prepared making sure of course to pick the right rod for the job. ie the right kind of plastic.
In some cases we have to do a match test to make sure the rod we are using is the same kind of plastic as the bumper we are going to weld.
The welding gun is basically a hot air gun controlled electronically, the hot air is forced out the nozzle at a certain temperature heating the groove in the bumper and the plastic rod which is passed through the guide at the same time, as can be seen in the photo on the left.
The two welding rods in the inset don't show the detail very well but the one on the left (inset) has the round head which will be used for this repair and the one on the right is a square rod.
The welded area can then be prepared for painting by smoothing, using files, carving chisels, and sanding.
The same factory two pot paints are always used for refinishing, and in some cases where the plastic component is not painted in their original form, modern two pot paint
applications can be used to make an invisible repair.
I have found this particular type of welding gun to be very good after trialling many makes and models. It is called a 'Leister'
The hot air flow is controlled electronically, which means I can weld the most delicate of jobs by altering the temperature from a high down to zero.
It is also a very well balanced gun.