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BASIC RULES FOR WELDING PLASTICS:
The majority of plastics used are thermoplastics which, as a rule, are suitable for plastic repair without any difficulties. The following basic rules should be observed.
1. Identifying Plastic: Check whether the plastic part to be welded has a plastic identification code. If the code is missing or unrecognizable, easily conducted tests can be helpful:
Floating test in water. Take a small piece of plastic from the part to be repaired and test if this floats on the water surface (PP-EPDM, HD-PE, PP) or sinks (PVC-U, PVC-P, ABS, PC).
Surface condition. The surface of plastics can be differentiated from horn-like (PVC-U, PVC-P) to waxy (PP-EPDM, HD-PE).
Adhesion test with welding rod. Heat up the welding rod, which is marked with the material identification code, and the plastic part by applying hot air. Press the welding rod onto the plastic part by applying hot air. Press the welding rod onto the plastic part to be welded. If the cooled down rod stays firmly in place or can only be pulled off with difficulty, both plastic materials are the same. Welding rods made of PP-EPDM, HD-PE or PP can be stringy when pulled off.
2. Four basic rules for plastic welding:
Weld like with like material. Only materials which are the same can be welded, i.e. PP with PP. A weld of PP with PVC or other plastics is not possible.
Correct temperature. The plastic must be heated up until it is plasticized (doughy). The function program will help you to choose the right temperature matched to the material.
Even pressure. When welding with rods, the pressure is applied by pressing on the welding rod. For overlap welding of films and tarpaulins, the necessary pressure is applied with the help of the pressure roller.
Constant welding speed. To achieve a good weld, an even working speed should be maintained. When welding plastics with hot air tools, three variables are critical to achieve a good weld.
TEMPERATURE, PRESSURE, TIME
Temperature is the set welding temperature for the plastic that you are welding. It is crucial to be able to adjust the temperature on the tool according to the plastic and to maintain the set temperature throughout the welding process. With the Leister high wattage tools, you have the ability to fine tune the temperature through the electronically controlled potentiometer and maintain the temperature precisely.
Pressure is very important. Without it you cannot get plastics to join together. Pressure is applied by pushing down on the welding rod while welding or, if butt welding, on the two edges that are being overlap welded together. Leister manufactures precise speed welding tips that help the welder apply equal pressure throughout the welding process.
Time is critical because if you move too fast or too slow, the quality of the weld will be compromised. |
