How to weld all types of plastic

Written by darby stevenson
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How to weld all types of plastic
Plastic welding allows you to repair damaged plastic pieces on your own. (Hemera Technologies/ Images)

Welding plastic brings two parts of plastic together through the application of heat through a welding gun. It is possible to repair plastic cracks, splits and even missing plastic through plastic welding. Welding plastic makes use of the same principles as welding metal. Only exactly similar types of plastic can be welded together. Welding plastic in the simplest terms is melting the edges of plastic in order to join them together.

Skill level:

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Things you need

  • Foil Tape
  • Plastic Welder
  • Plastic Welding Rod
  • Grinder

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  1. 1

    Identify what type of plastic you have. This is essential, because you will need a different plastic welding rod for each type of plastic. The type should be labelled on the plastic. If the label shows a triangle surrounding a 3, a circle surrounding a V or the letters, PVC, use a high density polythene welding rod. If the label shows a triangle surrounding a 4, a circle surrounding the letters LDPE or the letters, PE, use a vinyl or polyvinyl chloride welding rod. If the label shows a triangle surrounding a 5, a circle surrounding the letters PP or the letters PP, use a low density polythene welding rod. If the label shows a triangle surrounding a 6, a circle surrounding the letters PS or the letters PS, use a polypropylene welding rod. If the label shows a triangle surrounding a 7, or the letters, GTX, NORYL or RIM, use a polystyrene welding rod.

  2. 2

    Use warm soapy water to clean the damaged area on the plastic.

  3. 3

    Use rough 80 grit sandpaper to round off the edges of the damaged area. If the plastic is thick enough, use a grinder to grind a V-shaped edge where the two pieces will join. Use foil tape to join the damaged parts together.

  4. 4

    Preheat the plastic welding gun for 15 minutes. Warm up the area for repair as much as possible using the heat from the welding gun. Do not touch the plastic as you could melt it. Run the tip of the welding gun over the area where the two damaged parts are joined together.

  5. 5

    Place the plastic welding rod into the preheated tube on the welding gun.

  6. 6

    Feed the rod in a steady motion, by moving the applicator tip along the joint. The welding rod will melt out over the plastic parts. Let this partially cool. Remove the welding rod from the welding gun.

  7. 7

    Smooth over the welded area in a circular motion in order to join the molten weld into the original material. At this stage you are not adding any more plastic to the weld, just smoothing over the weld that is already there.

  8. 8

    Repeat Steps 4 through 6 on the reverse side of the repair if desired.

  9. 9

    Smooth out the weld by sanding with 150 grit sandpaper. Repeat with a smaller grit paper for more smoothness if desired.

Tips and warnings

  • If the plastic cannot be melted, it cannot be welded and will need an adhesive to be repaired. In case both sides must be welded, leave a thin space between the two pieces. This will allow the welding material from the rod to join in the centre.

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