Best way to bend plexiglass for VMC tool carousel cover ?
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  1. #1
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    Default Best way to bend plexiglass for VMC tool carousel cover ?

    Not a great photo below since it only shows about half the opening but hopefully you get the idea. Originally this had a tinted plexiglass cover but previous owner lost it. I suppose I could use thin enough material to simply bend it in place but would be nice to have it 3/16" and permanently formed into that curve. If I draw a template of the curve can most "glass" houses bend to match ?

    img_1282.jpg

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    I would use a polycarbonate (lexan) that can be bent and formed just like metal sheet.

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    I would use polycarbonate instead of plexiglass. Make a curved surface matching the radius of the drum, wood or similar. Laminate the surface with Formica or equal for a smooth surface. Lay a sheet of Lexan on the the form. Fasten the center of the sheet to drum on the edges. Now, warm the sheet in the middle until it is soft enough to bend on its own. Rotate the form and continue to heat the sheet until it lays smoothly on the form. Do the same for the other side. Do not overheat as the sheet will blister and bubble.

    Practice on the small sheet to get the "feel"

    Tom

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    Plexi forms easy at about 300 degrees F.

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    +1 on the lightly warmed plexi. Heat gun on low or even an electric blanket type heating element until it's pliable.

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    ^^^^These dudes got it right.^^^^ Heat and form. A heat gun, torch, or some heating elements in the correct area, then bend to form. Just like most other materials, go a little bit more than what you need, it'll come back.

    The best thing I've learned with this stuff is to cool it with water when it's where you want it.

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    Yes^^
    Lexan, not plexiglass. Remove protective covering, heat to 300 in oven, or with industrial heat gun, wrap around a form of some sort, and let cool. Sharp angles can be bent in an apron brake to 90 degrees without breakage. If you don't have an oven to fit it, cut the strip longer than it needs to be, bend 90 degree legs on each end, and clamp around something slightly smaller than you need, and heat carefully with the heat gun. Cut off excess. Viola!

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    Keep the heat moving too. If you keep the gun in one spot too long it will burn (bubbles up) before it bends. We make a number of plexi guards for machinery with right angle bends and used to do it with a heat gun, but then bought a bender (essentially a sheet metal table with a long heating element running down the middle (https://www.professionalplastics.com...UaAo9rEALw_wcB). But for a gradual bend, a heat gun is still the way to go. Keep a little pressure on the piece until you feel it 'give' and then take the heat off.

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    Our local plastic fab shop has a hot box for this sort of deal.
    The sheet is placed over a form in the oven and just heated till it settles right over .
    Last edited by Trboatworks; 03-23-2019 at 06:16 AM.

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    I spent a huge amount of time in the first year of my apprenticeship making guarding for machinery, plexiglass is easily bent using heat, the more even the heat is the better, a piece as big as that would be tricky with a heat gun (still possible) your best bet is to use an oven of some kind, put the plastic in with something underneath, when it bends over the thing take it out and lay it over a wooden form of the curve, use grease proof paper in the oven and over the form to prevent impression marks and a wet rag to cool it when it's in the shape you want

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    Default Best way to bend plexiglass for VMC tool carousel cover ?

    Never mind


    Sent from my iPhone using Tapatalk Pro

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    Several comments above say 'lexan' not 'plexy' but don't say why. Its because Plexiglass is brittle and easily broken (very sharp edges too!) while Lexan is nearly unbreakable. Much safer!

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    Quote Originally Posted by Red James View Post
    Several comments above say 'lexan' not 'plexy' but don't say why. Its because Plexiglass is brittle and easily broken (very sharp edges too!) while Lexan is nearly unbreakable. Much safer!
    Good point, makrolon is also an option (I think they're both just different brands of shatterproof polycarbonate), again it can be formed in the same way

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    Nice link to line bending. The high end of line bending is with a British company called CR Clark. Home - C R Clarke & Co C R Clarke & Co

    Hermes is another cost effective line bending machine-- I picked up one on ebay. This method is also called Hot-Wire bending.

    The oven forming method is called Drape Forming. Motorcycle windshields come to mind for this process.

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    Quote Originally Posted by Red James View Post
    Several comments above say 'lexan' not 'plexy' but don't say why. Its because Plexiglass is brittle and easily broken (very sharp edges too!) while Lexan is nearly unbreakable. Much safer!
    Yes, but....how about the exposure to hydrocarbons & coolant mixes ?

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    Quote Originally Posted by digger doug View Post
    Yes, but....how about the exposure to hydrocarbons & coolant mixes ?
    Quick googling would say that polycarbonate has better chemical resistance for most chemicals than acrylic.

    Biggest weakness is that it scratches easily and its not same level of optical quality as acrylic.
    (Hard coated polycarbonate improves the scratching issue a lot.)

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    Quote Originally Posted by digger doug View Post
    Yes, but....how about the exposure to hydrocarbons & coolant mixes ?
    I've used it for coolant screens on machines and never had a problem

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    While polycarbonate is sensitive to hydrocarbons as are most amorphous thermoplastics (most, not all), the key to their success is eliminating internal stresses and stress risers. By warming pc and allowing it to move of its own, the stresses as would come from cold forming are minimized. Also, around holes, edges, notches and such, the edges should be smooth and free of nicks. Drill a hole then gently flame polish the edges.

    Tom

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    Quote Originally Posted by TDegenhart View Post
    While polycarbonate is sensitive to hydrocarbons as are most amorphous thermoplastics (most, not all), the key to their success is eliminating internal stresses and stress risers. By warming pc and allowing it to move of its own, the stresses as would come from cold forming are minimized. Also, around holes, edges, notches and such, the edges should be smooth and free of nicks. Drill a hole then gently flame polish the edges.

    Tom
    I just stick the sheet in the folder and have at it, machine guards (over here at least) are polycarbonate, acrylic aka Perspex shows up but only rarely, torch and heat guns usually result in blistering before the stuff gets hot enough to bend
    A strip heater is an easy little project great for bits and pieces ( I got fed up with making guards, the safety department went insane over the last 10 years in work, I swear there were guards on the guards, someone even suggested guards on the toilet roll dispensers, they took the suggestion seriously, mad
    I digress, I bent up some 6mm polycarbonate on my folder yesterday, looks very professional (more professional than roofing bolts and angle iron!
    Mark

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    Quote Originally Posted by boslab View Post
    I just stick the sheet in the folder and have at it, machine guards (over here at least) are polycarbonate, acrylic aka Perspex shows up but only rarely, torch and heat guns usually result in blistering before the stuff gets hot enough to bend
    A strip heater is an easy little project great for bits and pieces ( I got fed up with making guards, the safety department went insane over the last 10 years in work, I swear there were guards on the guards, someone even suggested guards on the toilet roll dispensers, they took the suggestion seriously, mad
    I digress, I bent up some 6mm polycarbonate on my folder yesterday, looks very professional (more professional than roofing bolts and angle iron!
    Mark
    yeah... Guards on guards LOL, sounds familiar, it's when you get told to redesign the guarding on a machine that's been run for 40 years without a single accident, just because it might be possible for someone to reach the cutters if they ram there hand through the mesh xD

    If you get blistering when you heat polycarbonate it's because your heat isn't quite even and you get hot spots before the rest is warm enough to bend. I will admit it's a bit of a fine art to drape form larger sheets and takes a lot of practice on scrap - there's a narrow line between the point where it becomes easily flexible and the point where it starts to blister. If the piece is small enough to get inside an electric fan oven (just a normal kitchen one) that keeps the heat nice and even and works great

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