Help on bending styrene tubing

[TazMan2000]

Currently I'm working on a 1/16 scratch/kitbash Y-Wing. I have several diameters of evergreen plastics hollow tubing that I require bent, some with a 1D bend.
The problem is is that I'm routing wire through the tube for lighting and power, so I can't use the solid plastruct pipe bends.
With the small diamter evergreen tubes I can stick in a brass rod, but with the wider tubing, I heat it up with a candle and it starts ovaling the cross-section or melting so that I don't get a smooth bend.
Is it my technique or my tools? There must be an easier way.

TazMan2000

[Lt. Z0mBe]

What about threading some steel or brass rod through first, GENTLY heating the concoction, and bending? It might be worth a shot. In theory, the cross-section should be maintained, and with a bend so slight, you might be able to retrieve the rod.

Or, try solder in the center. Just don't get it hot enough to melt the solder...or do get it hot enough. Maybe that would work. The solder just runs out of the ends leaving you with a hollow tube.

I hope this helps.

Kenny

[Scotaidh]

I thought of something, but it's perhaps a bit labour-intensive. Gently heat the tubing in an oven so it's all heated, not just the bend area, and then induce your bend.

Or you could just use a micro-tubing-bender with either brass or aluminum tubing ... that'd be my choice, because of the better 'to scale" wall thickness. But if you must have plastic tubing, then sheathe the aluminum tubing in the plastic and then bend it, leaving the metal in place. It's more expensive that way, but it'd hold the bend and even allow for realistic 'damage deformation' later ...

[USSARCADIA]

I would suggest trying to heat it with a hair dryer first, that may be enough heat. I used this method with Evergreen styrene rod with success. If heat alone doesn't work, you could use a razor saw to put a relief cut on the "inside" of the bend, heat and bend, then put a touch of glue at the cut. Fill gaps as necessary.

[Stu Pidasso]

Does it have to be styrene? Why not try heat shrink tube, or a straw, or another flexible medium?

[Chacal]

Get the wires inside the pipe beforehand, add other stuff, like thick nylon monofilament until the whole tube is 'packed' with parallel strands. Then gently heat and bend it, leaving the 'filler' inside to keep it from collapsing.

[wraith1701]

Heating styrene with a candle flame sucks. Not only is the heat too intense, you often end up with soot residue on the part. I'm speaking from experience.

I've found that immersing the part in boiling water works better. Not only is the heat more evenly distributed, it isn't as intense, so there's less chance of your part melting. Unfortunately, it is also a pain in the butt. I suggest experimenting with a piece of scrap styrene beforehand, just so you can get an idea of the water temp & time immersed that works best for you.

Good luck!

-Eric

[Stu Pidasso]

Aquarium tubing?

[Chacal]

Labware glass tubing? It bends nicely with a torch and some blowing to keep it from collapsing. Then you paint it.

[Wug]

Hi TazMan2000,

What are the diameters of the tubing you want to bend? For small diameters use copper wire or solder. They're easy to bend and conduct electricity. If you're lighting with florescents or lightsheet, no one will ever touch your model twice.

Mike

[Andrew Gorman]

I'd scrap the idea of using plastic tubing and substitute aluminum or brass. There are plenty of little tubing benders available from Micro Mark, et. al., BUT at 90 degree bend is a hard one to make, The Plastruct piping is easy to use, and you might want to re-engineer your wiring routes.

[DennisH]

For heat bending tubing, the typical thing to do is cap one end of the tube, fill it to the very top with DRY sand (moisture will not do!) and cap the open end. You need a solidly filled tube with no air pockets/voids.

Make a pattern (out of plywood, perhaps) that follows the pipe bend you want to make. For example; You have a 3" PVC pipe and a forming pattern with a 3" trench in the shape you need the pipe to follow. Heat the pipe until it becomes pliable, lay it into the pattern and let it cool. The sand will act as support to (hopefully) keep the softened pipe from warping on the radius. After it's cooled down, cut the caps off and pour the sand out, cut to desired length on eac side beyond the radius.

We made a pair of tradeshow display models of the Club anti-car theft device (one 6 foot tall and the other was 8 or 9 foot tall) using this technique. It's involved, but gets results if done properly.

Although I've never tried it with tubing as small as what I think you'll be using.

My 2 pennies anyway. Maybe it will help?



Dennis

[TazMan2000]

Thanks to everyone. All are excellent answers that I would never have thought of. Its going to be about a 5-6 mm pipe. I really like the idea of putting in relief cuts in the pipe. A bit of filler and sanding and it looks like it was designed that way.
Lighting came as an unfortunate afterthought...or I would have stuck in the wiring beforehand.
I'm going to use the bendable wire inside the pipe idea. Since the brass will act as a wire for the electricity. Then for the larger diameters either Plastruct or some other medium.
The lighting will be LEDs.

[BROCK UPPERCUT]

deleted

[galaxy_jason]

For heat bending tubing, the typical thing to do is cap one end of the tube, fill it to the very top with DRY sand


Dennis

I've used salt before to bend coper tube but not sure if it could be heated.

[MillenniumFalsehood]

It would be *much* simpler to use a brass rod soldered directly to your leads.

[Warped Speedster]

If heat alone doesn't work, you could use a razor saw to put a relief cut on the "inside" of the bend, heat and bend, then put a touch of glue at the cut. Fill gaps as necessary.

Good advice.

"Evergreen" tubing isn't anything like running underground PVC conduit on a construction site for pulling wire in. I've run countless miles of that stuff--bending it with torches and "hotboxes," and using factor sweeps. I've even used the tail pipe of the truck to blow hot exhaust through the pipe to heat the whole length from the inside at one shot, then lay it in a curvy trench like a hot wiggly snake. For big pipe that usually worked better than any PVC bender you could buy at an electrical supply house. But bending thin Evergreen tubing is a whole different deal.

Unless you're just talking about slight radius sweeps you can almost forget about doing any serious heat bending with thin plastic tubing with any accuracy. It'll bend, sure enough, but it usually doesn't look good enough to want to use it on your model. Metal is MUCH better to use for major bends, using the simple tubing benders you find at your average HS.

For plastic, USSARCADIA's idea of "Relief cuts" (I call them pie cuts) is a very good way to get an tight accurate bend in Evergreen tubing. It will maintain the tube's true diameter all the way around the bend. (No colapsed tubes) It takes time, true, but no more than fiddling with heat, boiling water, flames, etc.

USSARCADIA mentioned making the cuts on the inside of the radius, and that works great for wider bends. But you can also make the cuts on the outside of the curve for much tighter radius bends if you need them. And you don't really need to apply any heat to the plastic using this method. As you make the thin slices in the tubing it will become very easy to bend by hand, kinda like a "Slinky." Then, like he said, fill in the cuts (gaps) with CA, or with thin strips of plastic, then CA, and gingerly sand to shape.

For the best looking results, your cuts need to be close together and evenly spaced. This is fairly easy to do using a miter box. And use a round object as a radius guide when making the bend. I've done this "pie cut" method a few times now, even with square tubing, and it works pretty good. Looks "factory."

Also, unless you're careful not to plug up the tube with too much glue, you may want to pull your wires through the bend before you start filling the gaps and gluing it all together.