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Does anyone know a technique to bend a styrene tube to get a smooth bend (90 degree)? I've tried heating it with a lighter, but it crumples a little in the bend. Also, the heat from the lighter makes it swell a little before I even bend it.

I've tried packing the inside of the tube with copper wiring, but that didn't help either.

why don't you just miter cut the 2 ends and join them together? (green stuffing required if round pipe and not actual square/rectangle tube)

seems like a lot less work than bending the buggers.


also, you can buy 90 degree* styrene pipe elbows from producers like plastruct, that marry into the ID of the tubing your working with already. (and even match the OD)

if you're working with something square/rectangle though, I'd vote miter cut

bending that stuff that much just seems like a major PITA

Pack it with sand...tightly...very tightly. Take an exposed heat source, and gently bend. You will need to play with the distance from the heat to figure out how close and how long. I use an alcohol lamp for my styrene heating of this variety...and it goes fast.

The sand will help spread the heat around the tubing and prevent it from collapsing. Normally it does take a couple minutes to heat the area you want to bend enough without overheating it and causing it to rupture.

It is a different take on an old trick which people used to use for bending custom exhaust pipes.

If the 90 is too tight though (generally a radius of twice the diameter of the tube if I am remebering correctly) you will either need a bending mandrel or a preformed corner like those sold by plastruct.

Thanks, I will try the sand, otherwise the Plastruct elbows you both suggested.

 Sean_OBrien wrote:
Pack it with sand...tightly...very tightly. Take an exposed heat source, and gently bend. You will need to play with the distance from the heat to figure out how close and how long. I use an alcohol lamp for my styrene heating of this variety...and it goes fast.

The sand will help spread the heat around the tubing and prevent it from collapsing. Normally it does take a couple minutes to heat the area you want to bend enough without overheating it and causing it to rupture.

It is a different take on an old trick which people used to use for bending custom exhaust pipes.

If the 90 is too tight though (generally a radius of twice the diameter of the tube if I am remebering correctly) you will either need a bending mandrel or a preformed corner like those sold by plastruct.

Yeah, I've built steel frame chassis for cars using this method. I have no idea how hard it is to do with styrene as I imagine you'd need pretty fine sand seeing as the tube itself is probably quite thin, it doesn't help much if you only have 3 or 4 grains across the thickness of the tube.

But yeah, with steel it still needed a pretty fine touch to do it without buckling the tube, I'd always buy an extra length of steel tube in case the first one got buggered up. Have a stack of crappy roll hoops from all my failures.

I haven't tried it for polystyrene tubes myself, but have you tried dunking it in boiling water? It it below the melting temperature (which is a bit above 100C if I recall), but you might be able to get it soft enough for it to hold a bend. I'm not sure if it'll work for tubes, but I've used near-boiling water to bend polystyrene sprue pieces to angles where they otherwise would have snapped.

You can also use boiling water to reduce the stress in parts you've already bent, but they will tend to bend back (so you can bend it just before breaking, dunk it in boiling water, it'll partially bend back again, so bend it further, dunk it again, etc until you get the angle you want).

Yep, it does have to be fine sand. You can either by specific material (diatemaceous earth and some filter sands) or gather the fine particles from regular sand by sifting it to seperate...I do both and use which ever happens to be closest.

The biggest problem with bending tubing of any type or size is it will want to buckle and fold as opposed to bend...the physics make it so. Sand is a pretty good material in that it supports the shape but still allows you to bend it. Solid core wire works too...but finding the right size can be a bit of a pain. Stranded wire will tend to buckle. Even with solid core wire, it can deform on tight bends.

Mandrel bends allow for the smoothest and most extreme bends...but each mandrel is designed for a specific diameter tubing and a specific radius on the bend. If it is one that I need a lot of, I will turn one on my lathe but most the time that is more effort than what it is worth for just one or two bends.

The spring bending tools they make for metal tubing can work as well...but when you heat the plastic to the required temperature...it leaves an impression of the spring windings.