Wednesday, June 25, 2008

Plastic Welding for Fun and Savings

Sometimes a hobby can be more than just fun. It can be a great way to save money.

Plastic welding is that type of hobby. I started welding plastic about 10 years ago. Over the years, I have used plastic welders to build and repair enclosures, mounting brackets, car parts, kids toys, and many other items. It is fun and the results are useful.

There are two basic types of plastic welders; hot air and airless. I started with an airless Mini-Weld by Urethane Supply Company. It is similar to a soldering iron but with a temperature control and tips designed for the job. Since then, I have added three hot air type welders. The Mini-Weld is still the one I use most of the time. It is the "goto" tool for repairs and quick jobs.

The project for today was to repair torn out mounting holes in a plastic guard for a mini-van. The guard also provides mounting for the bumper cover. With the holes torn the cover was flexing.

This is what the holes looked like:

The torn diameter is almost 1" the hole should be 1/4". There were four holes like this in the guard.

This is how I repaired the guard;

1. Identify the type of plastic. The repair technique will vary depending on the type of plastic involved. Most plastics have identifiers stamped on them. This is the stamp on the guard:

It is Thermoplastic Olefin, TPO, which can be repaired with FiberFlex welding rod.

If you are not sure of the type of plastic, Urethane Supply Co. has a page that can help here.

2. Gather the need materials. For this job, I will use the Mini-Weld, FiberFlex Rod, and Stainless Reinforcing Mesh.

3. Clean the part. I use Dawn Ultra to remove heavy dirt and grease. Then rinse with plenty of warm water. Next I clean with a plastic cleaner and follow by wiping with alcohol to get the last traces of oil. Then, sand the area of the repair with 80 grit sandpaper to give the repair something to grab.

4. Put reinforcing mesh on the back side of the repair.

Notice that I put the mesh along the sides of the cavity as well. That is because this part will get stressed as the guard drags on the steep driveways we have here. I want it to have the extra strength.

5. Melt the mesh into the plastic, then cover with FiberFlex.

6. Fill hole on outside with FiberFlex overlapping the hole by at least 1/4".

7. Smooth and let repair cool. Then drill hole for bolt.

Repairing all four torn out holes in this guard, took about 45 minutes and used about $4.00 of supplies. Quite a saving.

For more information on Plastic Welding and Plastic Welders check out Urethane Supply Company. They have a very informative web site with a lot of pages on specific repairs. They also have a PDF, The Book of Plastic Repair, that is packed with how to information.

An extra benefit of plastic welding is the recycling of plastic materials. The items that you repair save landfill space. And, you will find yourself saving scraps of plastic from other items to use as fill material. Unlike metal welding where you have to have special rod to use for filler, with plastic you can use any scraps of the same material as filler. I often use the cut off ends of nylon wire ties as filler. Plastic welding is an Earth friendly hobby.


Joe said...

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Rip Linton said...

Glad it gave you some useful information.

Dave Hale said...

Any comments on air vs. airless?

Rip Linton said...

Hi Dave, I use both.

For most repairs, I use an airless unit from Urethane Supply Company.

When building something or needing to weld more than a few inches, I use air.

I also use two different types of hot air welders:

I have a unit from Harbor Freight that works great for things like running a corner bead or a splice. I like it because it is small and easy to carry. The negative thing about it, is that it relies on a source of compressed air.

I also use a heat gun style unit, from Malcom, that provides greater heat over a larger area. This is perfect for large patches or thicker materials.

I hope that helps.