Lexan bending questions

[GAC05]

Not quite sign stuff but I did wrap them with 2080 matte black and did the logos on the outside along with all the police gear.
I made a small vice-mounted brake so I could cold roll these light guards (they keep the LEDs from flashing back off the windshield into the driver's eyes) into shape. Used thin polycarb and everything was tight and flush but after a few weeks with them parked out in the sun the folds started to relax and spring back away from the 90-degree bends. Looked it up, and I guess I am supposed to bake them after folding to set the Lexan.
"When polycarbonate is bent professionally, the sheet is folded into the desired shape when cold and then heated in an oven at a low temperature (maximum 70 degrees)."
That temp seems pretty low and these are wrapped in black, inside a black SUV near the windshield under a tropical sun. When these vehicles sit it gets a good deal warmer than 70 degrees inside.
Would it be worth a try to reset the bends, then hit them with a heater gun to hold the fold (same as post-heating cast vinyl), or give up - scrap these and redo them with some aluminum?

 

[netsol]

70 degrees C is 158 degrees F

you may still reach that temp, in the sun, in guam, but not sure

 

[GAC05]

70 degrees C is 158 degrees F

you may still reach that temp, in the sun, in guam, but not sure

Yeah, I thought it must be C and not F but still seemed low. I think Lexan goes soft right around 150f-160f. I was troubleshooting the wiring under the headliner near the dome light (out in the sun) and I could feel the heat radiating off the roof sheet metal into the interior. It was too hot to touch for more than a second or two. I moved the wiring down tight onto the headliner so there was an air gap between it and the metal. I have 4 of them out on the road and another 3 with gear on order. Maybe time for a reboot.

 

[netsol]

i remember we had a member in spain, who talked about how quickly his epson prints (red & yellow) faded since in mid afternoon his black areas read 180 F in direct sun. (can't remember name, but, he was heavily into engraving & very knowledgeable)

I IMAGINE that 150 degrees C "resets the memory" characteristics of the lexan for want of a better way of explaining it

 

[Johnny Best]

Use the aluminum. Does not have memory problems like poly and acrylic. I am sure it gets hotter than 150 degrees during the day in Guam inside a car.

 

[Notarealsignguy]

I'd go with aluminum or bond some aluminum angle supports on the inside bends of the lexan. If you want a nice looking finished edge, use trimlok on the edges

 

[weyandsign]

Use a torch and heat the lexan as you bend it. (if you can't use aluminum)

 

[JBurton]

+1 for aluminum or aluminum angle in the 90, but that will bow up between fasteners in the heat when the two expand at different rates.

 

[Notarealsignguy]

+1 for aluminum or aluminum angle in the 90, but that will bow up between fasteners in the heat when the two expand at different rates.

Maybe use a flexible adhesive like Lexel or 5200?

 

[JBurton]

Maybe use a flexible adhesive like Lexel or 5200?

They don't truly bond to the poly like a solvent adhesive, and even with an epoxy, you have to rough it up a bit. I'd opt for a sandwich of aluminum bolting through the poly, but at that point why not go all metal?
Is this going to catch minimal wind, to the point you could consider ACM? Or is it on the front of the car?

 

[GAC05]

They don't truly bond to the poly like a solvent adhesive, and even with an epoxy, you have to rough it up a bit. I'd opt for a sandwich of aluminum bolting through the poly, but at that point why not go all metal?
Is this going to catch minimal wind, to the point you could consider ACM? Or is it on the front of the car?

These are inside just in front of the sun visors. That's one of the reasons why I did not consider climate change melting them down into liquid polycarbonate. I figured Lexan would be a little safer installed up near the driver's head over aluminum, if they had to make an emergency stop. Whelen does not make visor lights for 4Runners as they do for standard police vehicles.

 

[JBurton]

These are inside just in front of the sun visors. That's one of the reasons why I did not consider climate change melting them down into liquid polycarbonate.

You mean to say, you thought that putting them in the oven was safer than on top of it? That Guam heat is messing with your head!
But since it's inside, you're probably right to be concerned, maybe instead of folds just make 4 (3?) sides, use some bent .040" aluminum or thin angle to bolt it all together, use some rivnuts in the plastic to keep it from rattling too much as it all vibrates loose. Some Lexel would help, but only for so long. I think it says bake at 350F for up to 90 days before the VOC's really start to get aromatic.

 

[Notarealsignguy]

These are inside just in front of the sun visors. That's one of the reasons why I did not consider climate change melting them down into liquid polycarbonate. I figured Lexan would be a little safer installed up near the driver's head over aluminum, if they had to make an emergency stop. Whelen does not make visor lights for 4Runners as they do for standard police vehicles.

The trimlok will cover the sharp edges. Round off any corners before bending so nothing is pointy. We used to use 040 for hose covers inside of school buses when we put in A/Cs