How to heat bend large 4" radius on 2x2' polycarbonate box corners? 1/16" thick

[aluminumwelder]

I want to wrap a piece of 1/16th white polycarbonate around this box
we will also apply a piece of 1/16th white polycarbonate to the front and back flat surfaces and use a trim router to make it look nice.

I have used double sided tape to hold down the plastic to the aluminum frame, however it tends to create a lot of tension and I need to use rivets on the ends to keep the plastic from sprining back to it's original flat shape.

I have made sharp bends in poly using strip heaters that tap plastic sells, but they are for sharp 90 degree bends.

this is a photo kiosk and the corners are 4" radius about 6.25" long so very gradual.

What is the best method to heat set the corners so there is no tension?

I was thinking of putting a sheet of insulation on top to keep the heat in and then using a ceramic heater or hot air gun?

I could of course make a huge 6.25" wide heating strip and do one corner at a time, but then alignment of each bends needs to be perfect. it would be easier to heat set while on frame!

View attachment 102565

 

[Chriswagner92]

what if you secure the poly to a place on the frame that isnt going to be seen and then just heat it with a heat gun while you bend it around the rest of the frame and glue it. Or you do the same with flat self tapping screws and just paint them white afterwards.

 

[SignProPlus-Alex]

Hmm. How do you going to service that machine if it brakes? Looks like it slides out to the side. if that is the case put all flat sides first with removable access panels. than you need to make round corner jig and use heat gun to make 4 corner pieces separate.

 

[rjssigns]

Does it have to be polycarb? What about sheet metal? A competent shop could fab that easily. You could also put shallow cuts in ACM to get it around the corners.

 

[player]

Make a heat strip out of bricks and old barbeque starters...

 

[aluminumwelder]

"what if you secure the poly to a place on the frame that isnt going to be seen and then just heat it with a heat gun while you bend it around the rest of the frame"

Because you'd have to heat a 14x6.25" perfectly evenly for the bend to look nice. Can you really do that with a heat gun. Years ago I tried and got bubbles in some areas. But maybe my technique is bad? have you actually accomplished this? I'm thinking some sort of central heat source that slowly and evenly cooks up the inside would be best?

"if that is the case put all flat sides first with removable access panels. than you need to make round corner jig"
No thanks I do not want 8 seams around the corners, I want it to look smooth and clean.I will make my own access door.

"Make a heat strip out of bricks and old barbeque starters..."
If you are just going to make stupid comments why bother posting?
"Does it have to be polycarb? What about sheet metal?"

The top and front need to be polycarbonate so that the photographic flash light goes through, while I could cut these holes in sheet metal
I'd rather just have it all be the same material. If I can't get it to work I will probably go with aluminum sheet metal around .093 thickness.

 

[GB2]

If it has to be translucent, I would try Acrylic before Polycarbonate, I think it may conform easier but I'm not sure. If you over bend the radius a slight bit then it should relieve the pressure to return toward flat. A series of shallow slits on the radius is worth a try. You might try making a bending jig by getting a metal pipe with a slightly smaller radius and then heating it from the inside with a torch as you try to form the material around it.

If you can go with a material that isn't translucent then PVC bends very easily and should conform with no problem, or even Styrene will work well and they shouldn't even look that much different around the sides with Acrylic on the front.

 

[Chriswagner92]

The only way other than a heat gun and gradually bend that i can think of is use an oven at low temp to get it even, similar to vacuum forming, only not... if that makes sense. I remember seeing an ad for something similar to this on craigslist and thought of how to do it right but I couldn't figure it out. at least not with the tools that i have available

 

[aluminumwelder]

this unit will be transported a lot, acrylic would crack within a month.

I'm going to try some hot oil on fiberglass cloth and see if that works. to spot thermobend it.

did some research and found that bubbles are caused by water vapor
makrolon the company recommends that the plastic be dried in an over for 4 yes, FOUR freaking hours at 250F
maybe I can coil it and put it in an oven becuase I dont' own a big enough oven for a 4' long sheet of this stuff.

I live in the very humid south, that would explain my past failures as well.

 

[aluminumwelder]

heated up some transmission oil and it stunk like crazy, after 7 to 10 minutes on the stove it got up to 350F and dipped the plastic in and it bent, but there is no way I will be stinking up my place again like that. Maybe I'll just blow $100-200 on some strip heating elements

 

[sardocs]

It was a while ago ( 15+ yrs) we bent some polycarbonate and acrylic using sand we heated in an oven. I think we laid some construction paper on the plastic then poured the hot sand on the area we needed curved and bent it around some 4" pipe.

 

[signfab]

I don't think that heating and bending one corner at a time will produce a good fit around your frame.
Ideally you would heat the whole sheet in an oven 'till it's floppy then wrap it around a mould that is the same shape as your frame. The problem is finding an oven large enough, maybe make friends with your local acrylic fabricator.