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?

Light Heat and patience

How do I know when to stop heating?

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

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.

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"

Ouch! That thick is hard to bend large pieces via heat properly.

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.

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.

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.

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.

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.

Dr. Joe J.

but making a shooter hood, should not require any sharp bends, only a gentle curve, right?

If I’m mistaken, maybe someone should post a drawing of what it is they want help figuring out how to build?

In the past we have used multiple mounting points along the arc of the hood as @Sarakiro was suggesting. As long as you use thin enough material, the Lexan should just flex along the curve (no heat necessary).

Last year we riveted the Lexan (~1/8") down to five rods of VEXpro’s ThunderHex which formed an arc around the flywheel.

In 2012 we bent tabs along either side of 1/16" Lexan and riveted the tabs onto several mounting points.

Last year’s approach gave us slightly more rigidity in the hood but but approaches worked out great. Because shooter radii will be smaller this year I would purchase 1/16" Lexan to be on the safer side.

2016: http://i.imgur.com/AxbqX2n.jpg?1
2012: http://i.imgur.com/GlQIJxh.jpg

Hope this helps.

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Everything you ever wanted to know about working with Polycarbonate from the people that make lexan:

We experimented this year with heating to low temp forming temps in an benchtop oven (before you need to bake it for 24hrs+) and forming in a mould. Worked nicely, but you don’t get a lot of time of plasticity to form it correctly.

I’d recommend this as well. We also used Churro to create this profile and zip-tied the lexan to that this year. Simple yet effective.

We have heat bent 1/4" in the past. We use a heat gun to heat it up and then bend it either on a table or by hand with gloves. Always wear gloves and safety glasses while bending polycarb. The heat gun is very very very hot.