Kieth’s Experience In Welding Plastic

10 Aug

© Copyright 2007 AgMedia Inc.

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How I learned about plastic welding

Figure out how to do satisfactory plastic repairs on the farm was a hit and miss process – until the author came across the right tools for the job


Like most people who fix things, I first tried fixing plastics with crazy glues. This was about 25 years ago, and plastic repairs were in early infancy.

Then, in the early 1980s, I had to fix some plastic bumper cover parts on a car I was rebuilding after a front-end collision. Now I was introduced into some very neat epoxy compounds available from auto body supply stores. These epoxy mixtures will bond and gap fill. Finishing is easy. The body shop world has many interesting products, but their needs are a bit different from fixing cracked sprayer tanks.

Then, about 1988, my farming friend Bob called for advice on repairing a 200-gallon plastic water tank that had blown across the yard and cracked badly after hitting a tree. This type of repair was beyond anything I ever imagined doing. But Bob was insistent, so I agreed we would give it a try.

I started with a visit to the small factory that made the tank. The shop foreman there agreed that this was a repairable tank, and that the repairs were “easy.” What he meant was that they were easy for him. Anyway, for $5 he sold me a shopping bag full of small chunks of the same plastic from the floor of the trimming shop, plus a small bag of what he said was resin.

According to this guy, all you did was heat the cracked area with a small propane torch, sprinkle on the resin powder and melt in some of the scrap pieces of plastic.

That seemed easy and it actually worked. But what a messy job! We kept heating, pouring in resin and adding plastic. We fixed a small crack with success, although it looked pretty messy. However, when we got to the big cracks, we learned that large areas of hot plastic start to sag from their own weight.

Luckily, we were welding close to the manhole and could reach in with a wood board to hold the plastic in place till it cooled. Eventually, we had a successful but none too neat repair that held water for years after.

Now my interest was high. Weeks later, at a huge U.S. farm show, I found a guy selling hot air guns and welding rods for welding plastic. This looked okay, given my limited success with the propane torch and scraps. He demonstrated how the narrow jet of hot air only heated the welding zone, along with the plastic welding rod that he fed into the welding zone.

I was ready to buy but didn’t like the price of the hot air gun. Moreover, the unlabelled selection of coloured welding rods didn’t seem right to me. He didn’t have a very good system for telling which coloured rod to use for a particular job. His suggestion to try different rods until you found one that worked didn’t seem too reliable to me.

Eventually, I bought a box of his many-coloured welding rods and a hot air gun. It was money poorly spent for me, as I never did a satisfactory repair.

Finally, about 1990, a reader called to tell me about North West Polymers (NWP) in Saskatoon. Here I met NWP’s director, Robert Decloedt, who had developed both the welding wires and the welding gun that were becoming the tool of choice for auto body repairs. After a factory tour and some serious training, I was sold.

I also involved my friend Bob (from the tank repair job) and we launched a series of building and repair projects. Bob was able to build a set of grey and black water-holding tanks for a large RV bus he was converting. After that, we were totally sold on the NWP process. We also learned how and where to buy large sheets of plastics.

About that time, I found the Canadian Plastics Industry Association in Ontario. It supplied me with lots of information, including the Plastics Identification Kit, which you can read about on the Better Farming website.

Now I have the NWP welder with the welding wires, plus a system for identifying plastics and selecting the correct welding wire. When you read my articles about repairing plastic things, this welder is usually my tool of choice. But always remember that selecting these tools is just like any other tool choice. You must pick the right tool for the job.

North West Polymers has several sizes of welding guns. The secret is to have the right heat for the job. A small 35-watt gun may not have the heat needed for welding the thick base of a water tank. And the adjustable heat-range feature of a top quality welder lets you set the weld temperature just right for flowing in the welding wire for proper fusion.

(image not part of original article)

I want all the tools I buy and write about to have a good use on a farm. The first picture accompanying this article shows the welder and one roll of thin plastic wire, as given to me by a local farmer who bought them at a local farm supply store.

(image not part of original article)

The idea was right, but the gun is only 35-watts and without variable temperature control. The roll of plastic wire was not identified. It should work on thin plastics but wouldn’t do this farmer’s thick polyethylene sprayer water tank. He tried and gave up.

The second picture shows the latest NWP welder, with the variable temperature control in the handle. The kit includes welding rods and wires, all labelled by type of plastic. BF

Keith Berglind is a licensed heavy-duty mechanic.


Just How Good Plastic Welding Can Get!

(image not part of original article)


Posted by on August 10, 2007 in Fabrication, General Knowledge, Recreation


2 responses to “Kieth’s Experience In Welding Plastic

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