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How to Weld Plastic

Kanika Khara Oct 6, 2018
Plastic welding is the process of welding or joining two pieces of plastic together, by using a plastic filler rod and a welder specifically designed for plastic. Read on to know more.
Plastic welding technique is almost similar to spot welding, but only differs by the fact that in this, heat is supplied through convection of the pincher tips, in place of electrical conduction. The two plastic pieces are brought together with heated tips pinch them, which causes them to melt and join.
A jet of hot air is produced during welding which melts the parts to be joined along with the plastic filler rod. As the rod melts, it is forced into the joint and fused to the parts.
The first thing to be considered while welding is to identify the type of plastic so that you can accordingly choose an appropriate filler rod. A plastic or thermoplastic filler rod is of a constant cross-sectional are that is used to combine two pieces of plastic together.
It is commonly used for welding and may have a circular or triangular cross section. An important feature of the plastic filler rod is its porosity. A rod with high porosity will cause air bubbles while welding, which decreases the quality of the welding. Hence, the rods used should ideally have zero porosity.

Plastic Welding

Before starting, make sure that the work area is clean and ventilated. Be careful while using the mini-weld plastic welder, as it is very hot and can cause burns or can even start a fire. Set the welder to preheat and keep it in the stand. Clean the part that you want to weld, which can be done by using water and soap.
Place the pieces together and use aluminum tape to hold them in position. If the pieces are painted, then it is required to sand away the paint from the area you are working on. Make a V-groove at the spot you are welding with the help of a grinder. Melt the rod by placing the welder tip on the surface of the plastic.
Draw the welder towards yourself in order to see the welding rod fill the V-groove as you make the pass. Before the melted rod cools down, take the hot welding tip to the same point, and thoroughly melt the rod and the base material together. Maintain the heat till you have a good blend between the rod and the base material.
If required, wire mesh can also be heated into the repair area for additional support, but make sure that it is covered with plastic. Be careful while welding thin plastic, as it can melt a hole in the base material. Once done with the front side, repeat the same procedure for the back side also.
After the part has cooled, you can grind the weld down. Initially, use a coarse sandpaper and then a finer one. Once you are done, do not forget to turn off the welder, place it in its holder, and allow it cool down.
Plastic welding is a technique used for manufacturing various products, like chemical tanks, water tanks, heat exchangers, and plumbing fittings. It not only saves money, but if done safely, it can be fun too.