Bending Lexan/Plexi - Updated

[crokett]

I need to fashion a clip to hook a webcam to the top of a laptop screen. My idea is just a simple hook that clips over the top edge. The back would be bent at an angle such that it applied a bit of tension to keep the clip in place. I would just make the clip wide enough to attach doubleside tape so the webcam will stick to it.

I played around with bending the lexan tonight. No pics - my wife left the camera at my folks' house. I used a piece of 1/2" copper pipe as a form to get the radius to bend around. Despite the warnings in this thread, my heat gun on high blistered it pretty quickly (more on this later). Don't try to bend too soon else it will fold and not curve around the form. This crinkles the edges. You also have to keep the work against the form to get it to follow the curve. To cool it I didn't do anything other than hold it to the shape I wanted and wait a few minutes.

As for the blistering, I was looking at the first piece I did that blistered and decided I liked the effect. Plus I want to paint it and I think paint will grab to it better than smooth lexan so I formed the 2nd piece then blistered it.

[cabinetman]

You could do it that way. Or use a heat gun or a propane torch, which would give you more directional heat. Don't apply direct flame. You should heat it slowly and not get it hot enough to blister. You have to have a method to hold it and form it. It will start to get a little elasticky when it starts to get close to forming temperature. When it gets to the stage that it gets flexible, it has to be held in the new shape until it cools.

Thicknesses up to 1/4" bend fairly easy especially if you can heat both sides (even alternatively).

If you re-heat it after it cools, it will try to get back to the original shape.
.

[Popeye]

Put it in the oven on a cookie sheet with foil for about 3 minutes and then bend it around a form. I did this on two marble towers that had clear tubing. make it over size. It can be reheated if the first time doesn't do the trick. Don't wrap it in foil, this is to protect your butt from the wife unit. Pat

[LCHIEN]

I would think the electric burner would be too large and soften the whole piece. You should use a heat gun like suggested earlier thats more directional and can be used to heat just along the edge where you want to bend it.

[crokett]

I have a heat gun but did not think it would get hot enough. I will try that. Not sure I need a form as this will be a one-off. I will find a radiused edge to bend around though.

[radhak]

David,
Could you please record and post a step-by-step for this?

I can see myself doing this for the same (webcam over a screen) and some other similar purposes. I am hoping to gain inspiration from your pictures and experience.

thanks.

[crokett]

I can do that. It won't happen till later next week though at the earliest. Flying to Dallas this Thursday for an overnight then flying out again early next week.

[Stytooner]

I use a heat gun to bend polycarbonate dust ports and it works very nice. You should have no trouble as long as you don't let it get too hot and cook it. As was mentioned, it will blister very fast once up to temp. It should start to bend just over 400 degrees F. 500 will bubble it. I always use a damp cloth to pat it with when it's where I want it. That cools it quick and it will better retain it's shape if you do cool it quick.

[Bigbit]

Crokett - What you need to do is get the material to a temperature above its glass transition temperature (Tg or softening point) but below its melting point, and then form and then cool it back below Tg. These temperatures are different for Polycarbonate (Lexan) and Plexiglas (PMMA or Acrylic). The exact temperatures are a function of the specific polymer formulation, but rough numbers would be:

Polycarbonate (Lexan): Tg = 300F, MP = 500F
PMMA (Plexiglas): Tg = 210F, MP = 420 - 450F

And Cabinetman is correct about its wanting to go back to its original shape; if you heat it long enough and hot enough it will shrink in both directions as it relieves the stresses put onto the polymer molecules when it was originally extruded. Try to use the minimum amount of heat to soften it and cool it ASAP after attaining the desired shape.