bending plastic pipe

[BillT]

I am interested in using a heat gun (or some other heating device) to bend some PVC pipe (schedule 40).

Any suggestions on doing this?

[BallAquatics]

When I bend rigid tubing I always insert a spring inside to prevent the tubing from collapsing on its self at the point of the bend.  With thousands of fittings available for PVC, what are you making that you need a special bend?

http://www.pexsupply.com/PVC-Schedule-40-Fittings-14952000

Dennis

[Mugwump]

I was going to ask the same thing, Dennis....any angle you want can be achieved with elbows,etc..
Are you looking for a curved piece??

[BillT]

When I bend rigid tubing I always insert a spring inside to prevent the tubing from collapsing on its self at the point of the bend.  With thousands of fittings available for PVC, what are you making that you need a special bend?

1) With small vinyl tubing (like stiff airline tubing and a bit larger) I am making tubes to penetrate the tank lids I am making and direct the water toward the front of the tank. This is fairly easy and mostly now done.


2) I am making a handheld feeding device to sell to labs. I have made several versions of this and for prototyping purposes have heat glued one of those soap holding handles from a sink sponge dish washing thing on to the top of the small food bin. This is a picture of an earlier prototype, with the soap holder handle as a food bin.



This works well, holds food for about 1,000 tanks, but will not cut it for a real lab product (looks junky, kind of fragile).
Among solutions I am thinking about are using a schd 40 PVC pipe (clear) to replace this. This IO if this size of the pipe conveniently matches the OD of another part it joins with (its a bit of an unusual size).
I have tried a 45˚ angle but it takes too much space. I am thinking the opening at about 45˚ from the main axis of the pipe, area of just above this opening ballooned out a bit where it is angled. Seems like glass blowing more than a normal production method.

Another possible approach would be to collapse the end of the pipe shut (getting a nice low profile which is good) and then cut a hole in one of the flattened sides. This may be easiest.

Alternatively, I am thinking of 3D printing the shape which has both pluses and minuses.


3) Generally you should be able to customize shapes to your exact needs. This could include usual pipe paths, but also standard things like sweeps in small pipe sizes. I have used flex pipe for this in the past but it is floppy and does not retain its shape. Hot tub pipes seem to be bent this way, but I think they use thinner wall pipe (this would mess up my IO/OD match however).

[Frank The Plumber]

I have never seen PVC tubing that has been radiused on site. I have seen fitments made that are used on Whirl pool tubs etc. I am not certain that those are PVC proper, they may be another form of plastics base tubing. I think if I wanted info on this I would contact the group that promotes awareness and manufacturing technology resources for the plastics industry. I think a hot fluid bend is made, I think the tubing is filled with a high temp liquid and softened and shaped with the liquid within providing resistance to kinking. This is the issue I have had when trying to bend PVC.    http://plasticpipe.org/

[Mugwump]

Would you be able to fill the tube with sand, ends capped, and then heat and bend??...

[BillT]

Interesting ideas! Thanks!

I am hoping to talk to a guy with a plastic shop today also. They have a plastic heating oven, maybe some other stuff.

[BillT]

I think a hot fluid bend is made, I think the tubing is filled with a high temp liquid and softened and shaped with the liquid within providing resistance to kinking.

OK, been thinking about this.
Is water used or would boiling be a problem?

[Mugwump]

I think a hot fluid bend is made, I think the tubing is filled with a high temp liquid and softened and shaped with the liquid within providing resistance to kinking.

OK, been thinking about this.
Is water used or would boiling be a problem?

I think this is done as an injection molding process...not separate

[LizStreithorst]

I know nothing, but I've read that you fill them with sand.

[Frank The Plumber]

Unfortunately the sand does not really work that well.I have tried using sand within stainless steel tubing to bend compound curves into relatively thin walled tubing. The tubing displaced the sand and the tubing wrinkled which was not acceptable. Trying to wet the sand within the tubing was slightly better but still not resulting in a curve that was acceptable visually. Still too much wrinkle. The biggest problem in heating PVC has bee the ability to get the tube to a uniform heat without causing a burn on an area. Then trying to heat all parts of the tube evenly to perform the bending without causing a collapse of the areas either under or over heated. I'm not sure if PVC may be steam heated and bent in the same fashion as wood might be, I'm also not sure that it would recover and reharden without issues. You would need to support the core and I'm not sure of the best way to do that either. You do have me curious now though.

[Mugwump]

Just wondering, did you get the pvc shaped? if so, how's the prototype coming along?

[BillT]

The spring inside the tube works well with fairly large diameter vinyl tubes like for airlift tubes or filter siphons.
I work by the sink with the water running.
I heat up a section of tubing with my heat gun with the spring already inside tube, bend it as desired, wiggle the spring a bit to loosen it, and hose it off in the water to cool it.

For my feeder:
I don't have a spring large enough to try this in a 1" pipe.
Now I'm thinking of a thinner walled tube, heat it up, crush one end closed, cut a hole of the desired size in one side using one of the following methods: a variable diameter hole cutter, a programmed mill, a laser cutter.
This will let me have a lighter tube (ergonomically good) and not be restricted to a particular size or product. I was thinking of using 1" pvc but I now i can use lighter materials.

Otherwise; I am getting the plastic for the rest of the feeder cut by a machinist (using a computer controlled mill) for some prototypes, then it will be revisions if necessary and make and assemble a bunch.

A large feed holder (the pipe thing) would be a option for larger labs (for feeding a few thousand tanks without refilling).

With respect to heating the pvc,
Some local plastic shops use ovens to heat whole objects up.
I was thinking of using my heat gun to heat one end and checking temperature with my IR thermometer. That should give some reproducibility.
Have not tried that yet because I am now searching for a tube of another possible material, but I'll probably try it out when I settle on what I want to use. Might have a different melting point etc.

[Mugwump]

Sounds like a fun project....keep us posted, this is interesting