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102 Posts
Discussion Starter · #1 ·
On the Halloween Forum, I said I'd post my results with that Harbor Freight plastic welder http://www.harborfreight.com/cpi/cta...emnumber=41592 and the addition of a voltage regulator. I think some folks here might also be interested, so here it is.

I used a Staco variable autotransformer model 3PN1010B 0-140 Volt 10 Amp 1.4 Kva.
I'm sure there are much cheaper regulators with the same capabilities, I got this one for free.

I also had to swap out the pressure regulator to one that could control the pressure better and lower than the Chinese no-name POS that came with it.
I used a Norgren # R07-200-RGKA pressure regulator, this will reg below 1 psi, again, this was free.

I'm only moderately satisfied with the results, but I do believe practice will make me better and I'll eventually get decent welds.

I did most of my testing between 30 and 75 percent voltage and at less than 1/2 psi.
By lowering the heater temp I could lower the air flow and keep from blasting the plastic away from the join.
I achieved various results, but with any welding there is some art to the science, and I didn't expect to find the perfect settings.

I tried welding a Mr Thrifty, and had a hard time keeping from scorching the surface at first. I finally ended up with a serviceable weld that needed to be painted and required a fair amount of prep work. I had to have a pretty good fit because I couldn't get a "molten puddle" of plastic. I had to use a lot of filler to get the pieces to adhere.
I then tried welding a Bart. Much better results. I could achieve a sticky semi-molten surface without scorching, fairly easily. I could press an ill-fitting joint together and have it stick without having to do a lot of prep fitting.

The Mr Thrifty was the same plastic that Buckys are made of, Marilyn told me she thinks it's polypropylene.
The Bart is obviously a different type of plastic. It's much smoother and glossy looking.

I did not try welding PVC! I just didn't have any lying around.

The conclusion I arrive at is that it's a viable process, although I don't think it's any faster than epoxy, in the long run it will be cheaper.
I think as far as strength goes, epoxy is probably a better bet. But, the Bart welds seem strong enough to more than support their own weight.

I was hoping to find a cheaper alternative to epoxy, I don't think this is it.

102 Posts
Discussion Starter · #9 ·
Thanks for fixing that link Lilly!

What I'm hoping to achieve is that ever elusive "invisible" support. I like completely free-standing "in the round" type props.
That's why I put far too much time, effort, and money, into everything I make!

Revenent, if you look up the prices of the components I added/switched, you'll find I'm getting pretty close to "pro prices"!
But, as I said, I got 'em for free.

I've been working 12.5 hours a day since Jan 1st, (only 8 on Sat. woo-hoo! Sun. is laundry, groceries and catching up on some sleep.), so I'm not getting a lot of time to do the things I want. An update may be a while in coming.

I can weld steel, and I did notice an improvement in the short time I spent on the plastic. I'm certain a decent plastic weld can be done.
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