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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: natalena on May 14, 2021, 09:57:33 AM

Title: Heat Forming Lexan 1/4"
Post by: natalena on May 14, 2021, 09:57:33 AM

Got an idea for a screen project, and can obtain 1/4" Lexan reasonably. Has anyone worked with heat forming sheets over a template? This would be done with heat guns. I'm wondering specifically about heat settings to initially soften the sheet and any "set time/temperature" to ensure the finished sheet doesn't develop a brittleness.
Thanks for any techie feedback!
Cheers

Title: Re: Heat Forming Lexan 1/4"
Post by: bocutter Ed on May 14, 2021, 10:27:45 AM

Heat guns are hard to use. If an area gets too hot it can bubble. Better to place in an oven and slowly bring up to slump temperature.

Title: Re: Heat Forming Lexan 1/4"
Post by: natalena on May 14, 2021, 10:39:26 AM

Thanks Bocutter, I  thought about an oven set up, and will probably take an old fridge, flip it on it's side and use that. Any idea what the temp range is between slump and "shites running everywhere!" ?
I'll have a thermometer inside the fridge to monitor.
Lexan posts 180-190f as working limit,  but doesn't have melt temps.

Title: Re: Heat Forming Lexan 1/4"
Post by: Motorhobo on May 14, 2021, 01:41:57 PM

I looked into it trying to make a windscreen for my sidecar. I did a lot of research and decided against it - there are a lot of ways to screw it up which you probably know if you've googled it.

Is 1/4 inch going to be enough? Once you drill through it for the mounts that's not a lot of strength there.

Title: Re: Heat Forming Lexan 1/4"
Post by: natalena on May 14, 2021, 01:51:53 PM

Good points Hobo. It's still an idea in infancy, so it depends if the concept forms up and is cost effective.  I thought of gluing a reinforced strip where screws apply pressure.
First time playing with Lexan. :)

Title: Re: Heat Forming Lexan 1/4"
Post by: frankenduck on May 14, 2021, 02:28:03 PM

Quote from: Motorhobo on May 14, 2021, 01:41:57 PM

Is 1/4 inch going to be enough? Once you drill through it for the mounts that's not a lot of strength there.

Aeroflow windscreens for the K75S are pretty big and they're only 1/8" thick.

(https://www.aeroflowscreens.com/K75S/Smoke.jpg)

Title: Re: Heat Forming Lexan 1/4"
Post by: daveson on May 14, 2021, 03:16:46 PM

I made a higher, wider windscreen from polycarb, I'm 90% sure it was Lexan branded. I like bocutter's idea better, but I did it the lazy way. I heated it over kitchen hot plates, and bent it 90 degree's over a kitchen bench. Held it there for say 20 seconds, then it was set and sprung back to about 45 degrees. Did it a few times till the angles were the same as the original. If you use an off-cut for testing, that would tell you the temperature at which it bends, and the overheated temperature.

I had no problems drilling the holes, so I'm sure you wont have problems with brittleness.

I'm sure it's strong enough without extra support. When I finished it I couldn't wait to try it so temporarily only drilled four holes. I've been 200km/h with that screen. The other holes are still on the To-do list.

A temperature gun would have been a big help to avoid overheating, which results in white spots on the surface. I got a few white spots, but they can be scraped off, it's on the To-do list.

Title: Re: Heat Forming Lexan 1/4"
Post by: Martin on May 14, 2021, 05:07:49 PM

A bird strike took off my screen and the corner broke off on hitting the road. The break was repaired using slow set super glue and kicker. Unsure of the joint strength it was then reinforced with boat deck tape, which covers the repair.
Regards Martin.

Windscreen Crack 2.jpg (46.73 kB . 768x576 - viewed 354 times)
Windscreen Repair 1.jpg (54.72 kB . 768x576 - viewed 449 times)
Windscreen Repair 2.jpg (37.8 kB . 768x576 - viewed 454 times)
Deck tape 1.png (45.59 kB . 768x576 - viewed 453 times)
Deck tape 2.png (90.05 kB . 768x576 - viewed 447 times)

Title: Re: Heat Forming Lexan 1/4"
Post by: bocutter Ed on May 15, 2021, 11:57:31 AM

Quote from: natalena on May 14, 2021, 10:39:26 AM

Thanks Bocutter, I  thought about an oven set up, and will probably take an old fridge, flip it on it's side and use that. Any idea what the temp range is between slump and "shites running everywhere!" ?
I'll have a thermometer inside the fridge to monitor.
Lexan posts 180-190f as working limit,  but doesn't have melt temps.

IIRC Lexan slump temp is between 150- 170º Celsius (not ºF), just look up poly carbonate slump temp.

I did a bit of bending Lexan® when I was building the rotary blast gates for the dust collector.

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