|
Posted by SteveB on April 9, 2008, 1:09 am
Please log in for more thread options
> The 122F temp is where the PVC starts to soften or deflect ie lose it's
> structural strength. Fully melted processing temp is 310F to 390F
> depending on exact composition. The temp the OP needs to soften the tube
> enough to form the tube and take a set is in the 200 to 250 degree range.
> Much hotter than you can handle with bare hands or even thin gloves.
>
> I'd agree that a good form and slow heating once you get close it a good
> idea. You can set the final shape by plunging into cold water but it will
> have a good deal of memory and spring back.
>
> Al Patrick wrote:
>> I *think* that melts not much above 122 degrees F. Once it starts
>> softening it will "melt" pretty quickly and get very floppy. You'll need
>> gloves and it wouldn't hurt to have a "form" approximately like the shape
>> you want it to finish in. Once it start getting hot you may want to heat
>> it very gently and start pressing it into the shape you want.
>>
>> Not sure on melting point of PVC but the 2008 NEC won't allow it to be
>> used in ambient air above 122 F and the wire which may be rated above
>> that temp has to be derated (load wise) to 122F.
>>
>> Let us know how it works.
>>
>> ========
>>
>> RoyJ wrote:
>>> A heat gun will work fine. For that size tube, just aim the heat gun
>>> through the tube, maybe swapping ends every couple of minutes to get
>>> even heating. The typical 1500 watt heat gun will warm the tube up to
>>> the proper temp in a few minutes.
>>>
>>> I might use something a bit fancier than a flat board. It seems that for
>>> any tube, once you get past a certain point it will start inverting in
>>> the center, forms a figure 8 rather than an oval. The exact point it
>>> does that depends on the wall thickness to diameter ratio and the
>>> material.
>>>
>>> lostfrom68jay@googlemail.com wrote:
>>>> I want to make an oval shape from a 28" length of 2.1" OD, .050" wall,
>>>> grey PVC drainpipe, flattening it to about half it's original
>>>> diameter. It's too big for the oven, and I don't know anyone in the
>>>> pizza business (let alone someone cool enough to let me contaminate
>>>> their pizzas with dioxin!) so I'm wondering if I could do this with a
>>>> heat gun and weighted boards. Any tips, or means I haven't thought of?
>>>> Robobass
We used a propane weed burner to heat some 2" electrical PVC and make bends.
It works great, but it's tricky. For the ovals you want to do, I can see it
would be very difficult to keep it pliable, yet avoid collapse.
Steve
|
|
Posted by Bruce L. Bergman on April 9, 2008, 4:26 pm
Please log in for more thread options
On Tue, 8 Apr 2008 21:09:37 -0800, "SteveB"
>We used a propane weed burner to heat some 2" electrical PVC and make bends.
>It works great, but it's tricky. For the ovals you want to do, I can see it
>would be very difficult to keep it pliable, yet avoid collapse.
If it collapses to a Figure-8, the save would be to armor up like a
gladiator (full face helmet and goggles underneath, heavy jacket, two
pairs of pants, etc) just in case, plug the ends of the pipe and apply
MODEST air pressure (like 5 to 10 PSI), and heat it again just enough
for the dents to pop out.
--<< Bruce >>--
|
|
Posted by charlie on April 9, 2008, 4:46 pm
Please log in for more thread options
> On Tue, 8 Apr 2008 21:09:37 -0800, "SteveB"
>
>>We used a propane weed burner to heat some 2" electrical PVC and make
>>bends.
>>It works great, but it's tricky. For the ovals you want to do, I can see
>>it
>>would be very difficult to keep it pliable, yet avoid collapse.
>
> If it collapses to a Figure-8, the save would be to armor up like a
> gladiator (full face helmet and goggles underneath, heavy jacket, two
> pairs of pants, etc) just in case, plug the ends of the pipe and apply
> MODEST air pressure (like 5 to 10 PSI), and heat it again just enough
> for the dents to pop out.
>
> --<< Bruce >>--
fill it with sand before attempting to flatten it.
|
|
Posted by Bruce L. Bergman on April 10, 2008, 2:01 am
Please log in for more thread options On Wed, 9 Apr 2008 13:46:56 -0700, "charlie"
>> On Tue, 8 Apr 2008 21:09:37 -0800, "SteveB"
>>>We used a propane weed burner to heat some 2" electrical PVC and make
>>>bends.
>>>It works great, but it's tricky. For the ovals you want to do, I can see
>>>it
>>>would be very difficult to keep it pliable, yet avoid collapse.
>>
>> If it collapses to a Figure-8, the save would be to armor up like a
>> gladiator (full face helmet and goggles underneath, heavy jacket, two
>> pairs of pants, etc) just in case, plug the ends of the pipe and apply
>> MODEST air pressure (like 5 to 10 PSI), and heat it again just enough
>> for the dents to pop out.
>
>fill it with sand before attempting to flatten it.
I thought about that one too. Good in theory, sand packing works
great for bending steel pipe and tubing without collapse, but sand
will not work very well for heat bending plastics.
The sand will have a lot of unwanted thermal mass - it will suck up
a lot of the heat from the inside of the plastic, and as the outer
layers of the pipe come up to bending temperature the inner layers
will be chilled as the sand sucks up the heat. And by the time the
inside (and the sand) is finally warm enough and ready to bend, the
outside is either soupy and losing it's basic shape, or on fire.
And once you get the bend in and cool off the outside with a cold
water hose, the heat from the sand is going to keep radiating back out
from inside. If you try dumping the sand you'll have to handle the
pipe to get it to flow out - and you'll mess up your nice neat bends.
Air doesn't have nearly the thermal mass as sand, and can be chilled
down far easier But you do have to be prepared to control the
pressure inside the pipe being bent - too much will cause a bulge
and/or a rupture of the pipe.
And cold PVC pipe under high pressure can shatter when ruptured and
will do a nice impression of a Chicago Pineapple, so you keep the
pressures low and wear eye and face protection.
Too little air pressure in the pipe (as in a partial vacuum) from
chilling, and you'll suck that pipe flatter than a soda straw on a
thick milkshake.
--<< Bruce >>--
|
|
Posted by nick hull on April 10, 2008, 6:46 am
Please log in for more thread options
> The sand will have a lot of unwanted thermal mass - it will suck up
> a lot of the heat from the inside of the plastic, and as the outer
> layers of the pipe come up to bending temperature the inner layers
> will be chilled as the sand sucks up the heat. And by the time the
> inside (and the sand) is finally warm enough and ready to bend, the
> outside is either soupy and losing it's basic shape, or on fire.
Heat the sand before you put it in ;)
Free men own guns - www(dot)geocities(dot)com/CapitolHill/5357/
|
| Similar Threads | Posted | | flattening a bolt | July 10, 2006, 1:10 pm |
| flattening a bolt | July 10, 2006, 1:10 pm |
| OT: (a little) Flattening a griddle | March 20, 2006, 10:16 am |
| Flattening silver wire | September 21, 2007, 12:35 am |
| Re: Flattening 1/4" Steel Plate? | March 7, 2006, 9:47 pm |
| Report back on: "Flattening 1/4" Steel Plate?" | April 16, 2006, 5:03 pm |
| PIPE TERMS | July 27, 2006, 3:06 pm |
| anyone have an old little pipe vise? | September 17, 2006, 5:46 pm |
| Coloring PVC pipe? | October 2, 2006, 3:47 pm |
| Turning pipe | June 21, 2007, 8:11 pm |
|
|
Yahoo! 
Google 
Windows Live 
del.icio.us 
digg 
Netscape 
XML Sitemap
> structural strength. Fully melted processing temp is 310F to 390F
> depending on exact composition. The temp the OP needs to soften the tube
> enough to form the tube and take a set is in the 200 to 250 degree range.
> Much hotter than you can handle with bare hands or even thin gloves.
>
> I'd agree that a good form and slow heating once you get close it a good
> idea. You can set the final shape by plunging into cold water but it will
> have a good deal of memory and spring back.
>
> Al Patrick wrote: