Using heat to 'shape' plastic?

bluegoatwoods

bluegoatwoods

Active Member
I'm considering using one of those hand-held heat guns to try to form plastic sheets into fenders and, perhaps, other body panels for future bike builds.

I'm talking about one of those heat guns that looks something like a hair dryer. 1500 Watts and temps of 500-1000 deg F. (I'm a bit surprised that you can get such temps. But that's what the specs say.)

For plastic material I guess I'd use the cheap totes or bins that you can get at a dollar store.

I'm wondering if anyone has experience with this and can advise about pros and cons. I can make a few guesses. Heating the plastic to about five hundred deg certainly ought to soften it up enough to shape it. I suppose, though, that it might be tricky to fix it into place without burning my hands. But I can try welding gloves. Or make up some sort of jig to hold the piece.

I guess I'll have to be careful not to melt the plastic.

Maybe one down-side would be that while the heat ought to do the trick in theory, I might find that it's still a slow and careful process. Perhaps not worth the time when fenders can be bought for about twenty five bucks or so.

Has anyone tried this? Any advice? Thanks.
 
It can be done with small pieces and limited area. Larger sections will be difficult because the heat is concentrated and the plastic cools quickly. You'll need a way to heat a large piece uniformly, as in an oven or under heat lamps and a form to get the shape you want. I think you'll find hand forming (free forming) will not give you the results you expect especially with compound curves such as fenders and shrouds.

Not saying it can't be done but the process sounds easier than it actually is.

Good luck, Blue and show us what you come up with if you try it. As you said, buying a ready made fender will probably be cheaper and less trouble.

Tom
 
"It can be done with small pieces and limited area. Larger sections will be difficult because the heat is concentrated and the plastic cools quickly. You'll need a way to heat a large piece uniformly, as in an oven or under heat lamps and a form to get the shape you want. I think you'll find hand forming (free forming) will not give you the results you expect especially with compound curves such as fenders and shrouds."
--2door

As a matter of fact I was imagining something along the lines of what you've described above, Tom. It's probably not going to be worth it.

On the other hand, though, Harbor Freight is offering a heat gun for $8.99 So it might be worth trying.

But......you know.......I might be able to use a fender as a form. And I might be able to get that whole thing into the oven in the kitchen.

I suppose I'll have to get my wife out of the house before I try any such thing. But I've found that I can distract her when need be.
 
LOL, I wouldn't want to be around if that plastic melts and runs all over the inside of her oven. :)

Tom
 
2door said:
LOL, I wouldn't want to be around if that plastic melts and runs all over the inside of her oven. :)

Tom
Click to expand...

Just gotta be careful with your temps and not get caught by the significant other! Girlfriend wasn't happy when she saw my fred head in the dishwasher!
 
In my limited experience, I'd say Tom's advice is right on. Polypropylene has a melting point of around 340°F but becomes pliable much lower than that, easily within the range of a heat gun. When trying to bend larger pieces, expansion and contraction from the uneven heating do not produce a pretty result.
 
wret said:
In my limited experience, I'd say Tom's advice is right on. Polypropylene has a melting point of around 340°F but becomes pliable much lower than that, easily within the range of a heat gun. When trying to bend larger pieces, expansion and contraction from the uneven heating do not produce a pretty result.
Click to expand...

Yeah.....that makes sense.

If it's possible to do it at all, then I'll bet it takes near-infinite patience.

Probably so time consuming, to get a good result, that it's not worth it. It's a shame.
 
Back when we were doing BMX one of the kids got some white plastic sheet material from TAP plastics that we used to make front number plates. It was very easy to shape using a regular heat gun. I remember shaping a few plates that snapped securely on to the handlebars without requiring anything else like zip ties or Velcro to hold them on
 
Polypropylene and high density polyethylene have no surprises provided you do simple curves, except that if you are going to use the cycle in low temperatures, you need to select a polypropylene with an additive to stop it being brittle in the cold.

ABS, acrylic sheet,polycarbonate and pvc are hygroscopic, that means they take in water from the atmosphere, and unless dried in a cabinet at around 70C for a couple of days with air flowing round it, you can get nasty scabby bubbles erupting from it when it is heated.
 
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Another thing to watch out for is fingerprints, or rough marks from gloves melted into it.

My brother used to make bmx numberplates, too. They looked professionally done, and all he used was the stove top.
 
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