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Unread 01-16-2017, 08:17 PM
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How to bend lexan for a hood?

The title says most of it. We want to bend a piece of lexan to create a hood for a shooter. We don't have access to a brake. How can we curve this piece safely?
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Unread 01-16-2017, 08:28 PM
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Re: How to bend lexan for a hood?

Light Heat and patience
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Unread 01-16-2017, 08:29 PM
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Re: How to bend lexan for a hood?

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Light Heat and patience
How do I know when to stop heating?
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Unread 01-16-2017, 08:32 PM
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Re: How to bend lexan for a hood?

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Originally Posted by ollien View Post
The title says most of it. We want to bend a piece of lexan to create a hood for a shooter. We don't have access to a brake. How can we curve this piece safely?
Depending on your thickness, you can try a heat gun and a piece of angle metal to use as a straight edge (in both dimensions). I would advise holding the bending part with something other than your fingers, for obvious reasons.

This was the second result for Googling "how to bend lexan": https://www.youtube.com/watch?v=6ik-wqRNFSE
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Unread 01-16-2017, 08:34 PM
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Re: How to bend lexan for a hood?

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Originally Posted by ollien View Post
How do I know when to stop heating?
If you want a sharp bend, when it easily flexes(I highly recommend a heat strip for this kind of bend). If you want a gradual bend, the only advice I can give is to buy extra polycarb and practice. Maybe some kind of radiant heater. Maybe thermoform/vacuform it.
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Unread 01-16-2017, 08:47 PM
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Re: How to bend lexan for a hood?

how thick is the material? We usually use polycarbonate that is a tad thinner than 1/8" thick. It will bend (and spring back) easily for things like that. If it's supported with an aluminum frame, then it will mostly hold it's shape.

If something looks kind of difficult to make the way you have planned, maybe you could figure out a different way to build it?
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Unread 01-16-2017, 08:59 PM
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Re: How to bend lexan for a hood?

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Originally Posted by MrForbes View Post
how thick is the material? We usually use polycarbonate that is a tad thinner than 1/8" thick. It will bend (and spring back) easily for things like that. If it's supported with an aluminum frame, then it will mostly hold it's shape.

If something looks kind of difficult to make the way you have planned, maybe you could figure out a different way to build it?
I'd have to check when I get back to the lab tomorrow, but if memory serves me right, it's 3/16"
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Unread 01-16-2017, 09:00 PM
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Re: How to bend lexan for a hood?

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Originally Posted by ollien View Post
I'd have to check when I get back to the lab tomorrow, but if memory serves me right, it's 3/16"
Ouch! That thick is hard to bend large pieces via heat properly.
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Unread 01-16-2017, 09:14 PM
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Re: How to bend lexan for a hood?

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Ouch! That thick is hard to bend large pieces via heat properly.
What thickness would you recommend? 1/8?
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Unread 01-16-2017, 09:28 PM
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Re: How to bend lexan for a hood?

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Originally Posted by ollien View Post
What thickness would you recommend? 1/8?
We had a lot of success with 1/8" last year. A lot of our robot, including the bellypan were polycarb. We mostly just used a vise and heat gun (be careful so it doesn't start bubbling). A continuous curve might be a little trickier than a one-place bend, though.
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Unread 01-16-2017, 09:47 PM
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Re: How to bend lexan for a hood?

We either cut several pieces with that profile and then bolt them together (with our without spacers in between) or create the profile with sheetmetal and spacers then line it with a thin piece of lexan that is zip-tied to the spacers.
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Unread 01-16-2017, 09:53 PM
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Re: How to bend lexan for a hood?

If you're just using it for a shooter I can't imagine you need too large a radius. It should be pretty easy to find something with a similar curve (pvc, lunacy wheels, etc) in your build space that you could mold the lexan around after heating it. This will be a lot easier than using a vise, and provide a clean curve.
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Unread 01-16-2017, 09:54 PM
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Re: How to bend lexan for a hood?

Quote:
Originally Posted by ollien View Post
The title says most of it. We want to bend a piece of lexan to create a hood for a shooter. We don't have access to a brake. How can we curve this piece safely?
Depends on thickness- the easiest way to get a gradual curve will be to make three mount points along whatever your chosen radius is by which you can use to attach the 'hood' to. (This works best with material up to about 1/16th of an inch.)

Alternatively, you can use a heat gun and apply heat evenly. you can use a similar form mentioned above, or round it by rolling it over a wooden dowel to the desired curve. if the material starts to bubble, you know you have overcooked it.

Hope that helps.
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Unread 01-16-2017, 09:59 PM
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Re: How to bend lexan for a hood?

I've been involved with building several robots that used polycarbonate for various things, over the past dozen years...I think I've used heat to form it, once, in that time. Just seems like a bit of unnecessary work?
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Unread 01-17-2017, 09:13 AM
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Re: How to bend lexan for a hood?

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Originally Posted by MrForbes View Post
I've been involved with building several robots that used polycarbonate for various things, over the past dozen years...I think I've used heat to form it, once, in that time. Just seems like a bit of unnecessary work?
I am with MrForbes.

Polycarb in thicknesses of 1/16 th or so are very easy to bend on a brake without heat at all.

I have seen some splitting with 1/8th but that is still servicable for most applications.

I don't think heat will hurt in most cases but I don't think it is necessary.

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