Does anyone have any experience with thermal forming plastic

[jabber35]

Does anyone have any experience with thermal forming sheets of polycarbonate (Lexan)?

[Ageless]

Yes. How do you want to form it?

[jabber35]

Dave... (actually, is it okay to call you Dave?) Have you seen my build pictures that I shared when I introduced myself the other day? It is the "trolley top" (I call it the "dorsal fin") that I have framed up in wood.

[Ageless]

Dave is fine; my ex calls me worse

Seen the trolley top; unless you want a really tight radius; polycarb has quite a lot of flex

[jabber35]

????

[Ageless]

I take it you want to cover the entire top of the dorsal with poly? The rear section is a sliht enuf bend that the poly should naturally flex without heat-forming. The front radius should be all you need then?

The trick with this is pre-heating. Poly absorbs a tiny bit of water and that is why it will bubble if you heat it. So pre-heat and hold at 225. You should have a male and female mold so that it can be clamped and held while cooling. Forming temp will be 350 - 375 degrees.

[schaney]

Jabber35, for a one-off like your tolley top it would be a lot more cost effective to have it hot-air welded. Build forms, heating system, vacuum table, etc will will add up into big bucks.

Is the idea to have it clear?

[jabber35]

"Smoked" polycarbonate...and I really want the radiused corners and smoothness. I appreciate the help and advice y'all!

[Ageless]

Yep, doing the entire top would reqiure vacuum-forming; not gonna be cheap.

[steve smoot]

"Smoked" polycarbonate...

Well, no sir, I have done a lot of things, but never done that....

I did go to the doctor this Monday and they says "well, your sinus cavities are a mess. Have you ever tried Neti Pot?" I says "no, but I tried Columbian a couple times"....

I'm sorry, really the devil made me say that....just overlook me....please....I promise to be better.

[schaney]

As already noted, to get nice radiused corners, the trolley like bubble and other stiffening features in the roof portion you're looking at vacuum forming over a male form.

Another consideration is a single wall plastic roof of this nature will get a lot of condensation in cooler weather. All the better skylights are double like a dual pane window to avoid condensation.

[jabber35]

steve smoot...WTH? have another drink you wildman!

[doug hodder]

I'd think it would bend just fine for you without any forming. It comes on a coil so it'll bend easily, just secure it well, heat would be an advantage to help reduce the stress that the curve would be under continually though. Polycarb can be put in a brake and bent. We did it at the sign shop quite often. Obviously the thinner the easier. That was with the official 3M poly Lexan. I don't know about the abilities of other manufacturers. However, If you want an entire top with the trolley portion molded in...yup, you're going to have to heat form that. Doug

[rrawlings]

Vacuum forming of polycarb is a trick business. I have a littel experience with this. I have a 48" x 28" vacuum former and can say from experience that to successfully form lexan or other polycarb materials it must be preheated to force any absorbed moisture out of the material or you will have a terrible fogging effect to the finished product. The expense of your male mold which if you want optical grade results will be very high. As was suggested by another builder, use a metal brake and bend it to the shapes you need. I am thinking of doing custom blow molded lexan windows for my Alto WW.