Plastic Welding Instructions

Written by c.l. rease
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Plastic Welding Instructions
Plastic welders use forced hot air to weld thermoplastics. (heissluftpistole - heat gun image by Cornelia Pithart from

Thermoplastics have found their way into many of the products you use every day. Some thermoplastics are used for plumbing and others are used to construct vehicle parts. When a thermoplastic part breaks, you need to use heat to fix the repair. Plastic welding goes beyond making repairs. Fabricating tanks and vehicle parts also require welding to join parts and seal seams. The most important factor in plastic welding is heat. If the heat is too low, the weld will fail and if the heat is too hot, the plastic will burn.

Skill level:

Things you need

  • Plastic part
  • Plastic identification guide
  • Plastic welder with speed tip
  • Stout knife
  • Die-grinder with bevelling tip
  • Plastic filler rod
  • Side-cutting pliers

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  1. 1

    Look for a three-digit identification code stamped on the plastic part. To weld plastic, you need to know the welding temperature of the plastic you are welding.

  2. 2

    Look up the identification code you found on the plastic part in the plastic identification guide, if you don't recognise it. In the plastic identification guide, you will find a welding temperature as well as a secondary means of identifying the type of plastic you are welding.

  3. 3

    Set the temperature dial of the plastic welder to the temperature specified by the plastic identification guide, then plug in and turn on the welder. Set the plastic welder aside and allow it to heat up.

  4. 4

    Run the stout knife over the edges of the plastic part that you need to weld. You need to make a bevel that is at least 50 per cent of the depth of the plastic part. If you are repairing a plastic part, you will need to use a die-grinder with a bevelling tip to create a bevel along the entire repair area.

  5. 5

    Place the heated speed tip of the plastic welder on the surface of the plastic part. When the surface of the plastic part begins to melt, feed the plastic filler rod into the filler rod opening of the speed tip.

  6. 6

    Push the plastic filler rod toward the surface of the plastic part.

  7. 7

    Pull the plastic welder across the weld area as you continue to apply downward pressure on the plastic filler rod. Watch the area where the plastic filler rod meets the plastic part. There should be a small puddle of melted plastic flowing in front of the filler rod. This signifies that you have the proper heat setting and you are pulling the plastic welder at the proper speed. If the surface of the plastic begins to burn, pull the plastic welder at a faster pace to spread the heat faster.

  8. 8

    Cut the plastic filler rod slightly above the speed tip with the side-cutting pliers when you are nearing the end of the weld joint. Continue pulling the welder until the end of the plastic filler rod is welded to the surface of the plastic part.

  9. 9

    Turn off the plastic welder and allow it and the weld joint to cool to room temperature before handling the welded plastic part and putting away the welder.

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