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Thread: Shaping tinted plastics for windows

  1. #1

    Shaping tinted plastics for windows

    Any recommendations for how to heat-curve tinted plexiglass for custom curved door windows and headlight covers? I've heard about heating the plexiglass to a certain temperature (?) and pressing it between two molded halves lined with felt, and then there is vacuum forming. The plexiglass will be 3/16 - 1/4 inch thick, so any suggestions to help me out with the best method and maybe some heating specs would be greatly appreciated. Here's the car in question


    Thanks in advance.

    Ken

  2. #2
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    Re: Shaping tinted plastics for windows

    Are any of the shapes compound curves? If so you will have to vacumn mold them. Heat the plexi or poly to 350 degrees
    for 12-15 minutes and put into mold. The heat gun method does not work for anything you want to look threw. if the entire peice is not heated evenly it will be very distorted. All peice will have to be cut big, shaped, trimed and them polished. Be very careful when pulling the plastic from the oven. wear gloves that are heavy. and don't touch any of the area that will be used. if you need any help figuring this procces out please let me know.

    David
    Just smart enough to be very Dangerous

  3. #3

    Re: Shaping tinted plastics for windows

    I once saw a system for the 917 replicas. The guy had 2 piece wooden forms that he would heat the plexi over soft enough to sandwich them in between, creating his windows.
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  4. #4
    Moderator FunnyWheels's Avatar
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    Re: Shaping tinted plastics for windows

    Ken:

    I have done this several times with a heat gun. Use Lexan 1/8 to 3/16 or so. Heat it up as up mount it in place then as it cools the shape will stay. This Mirage had plenty of curves on the back and side glass.

    It has to be hot as a mofo if you get my drift. Use gloves!

    Dave

    If you're not confused, you're not paying attention.

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    Re: Shaping tinted plastics for windows

    Dave: How well could you see threw your rear window? Was is wavey or distorted at all? The heat gun method usually
    makes it look like an ocean without heating it all completely and putting it in a mold. I've used the heatgun method before with small peices that you didn't have to look threw. My brother in law works at LP Areo in PA and builds the government windows for the military, I went into his work one day to see how they are formed. Pretty cool setup they have there. The poly looks like jello when its pulled from the oven and after 20-30 seconds of cooling its holding shape. they also build
    windscreens for the porsche team, GT40's and some old british cars.

    David
    Just smart enough to be very Dangerous

  6. #6
    Moderator FunnyWheels's Avatar
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    Re: Shaping tinted plastics for windows

    Hi David:

    I just heated and formed as I went. I could see through the Lexan just fine. It was a compound curve too. (Wider at the top like a funnel). The hot Florida sun helped too, I used smoked Lexan. Nothing fancy.

    Dave
    If you're not confused, you're not paying attention.

  7. #7

    Re: Shaping tinted plastics for windows

    Thanks for the tips. The tops of the door "glass" curve to match the roof line and the front headlight covers bend around the side, so there isn't too much complexity to it, but it's too much to just glue down and let it take the stress. I'm working on designing an oven big enough for the pieces, and was leaning towards the sandwiching between two molds approach, so I didn't have to make up a vac-forming table.

    So around 350 is what it should be heated to? I'm glad you said that because I probably wouldn't have gone over 250 if I was just to guess. I've never had to polish plexiglass before. Do you just treat it like a paint job... using ultrafine grit sandpaper and then buffing with rubbing compound and polishing compounds? Is it ok to use an electric buffer, or will that cause too much heat and melt it?

  8. #8
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    Re: Shaping tinted plastics for windows

    350 is the temp used in the big ovens, which may be a bit warm compared to a smaller one due to the size. I would use a few test peices to zero in the exact temp. But it should be very close to this. 12-15 minutes is all it should take to get it to a plyable state. You want it just soft enough to move very freely but not stick to anything. Remember after the peice is pulled you only have that 15-20 second window of work time, have eveything ready so all you have to do is lay it over the mold. Lay the material down centered with enough overlaping that is won't be short anywhere. put the top mold over and clamp in place. polycarbinate and lexan are both very user freindly. After trimming the peice if it needs to be wet sanded do it with 800-1100-1500 in the three steps. And finish off with your buffing wheel, Use a plastic polish VERY lightly, Like you said it will get hot fast if you apply too much pressure. Plastic can't be worked like paint can. You'll have to get the feel for it but it'll turn out awesome!. Good luck.. if I can help any more let me know.

    David
    Just smart enough to be very Dangerous

  9. #9

    Re: Shaping tinted plastics for windows

    Thanks so much for the tips. It's going to be a while before I'll be able to test anything, but I'll definitely be popping up pictures when I find a covered space big enough to start this baby. Your help is always much appreciated.

    Ken

  10. #10
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    Re: Shaping tinted plastics for windows

    You're very welcome Ken.. Best of luck to you. Post pics when you get that far.

    David
    Just smart enough to be very Dangerous

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