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Old 20-05-2015, 20:46   #16
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Re: Thermoforming A Curved Acrylic Hatch

The OP's equipment looks like something our company used except it also included a hood that was the size of the table full of heat lamps that had temperature sensors that controlled the heat closely. Compound curved parts were formed with molds under a silicon rubber blanket in a frame as shown in the OP's picture, and regulated vacuum pressure, with closely regulated heat. It was a very expensive piece of equipment that required some learning curve to get it right. Not at all well suited to one off parts, but reasonably effective for doing them in the low thousands.
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Old 07-10-2016, 18:35   #17
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Re: Thermoforming A Curved Acrylic Hatch

Delancy - I need 4 curved ( cast acrylic preferred) windows, 3/8" thick about a 10" R. Too big to fit in a kitchen oven. Prior experience is that if you heat too quickly, you get internal bubbles ( moisture). I could use the old windows as a mold. Possible to do? HOw to heat? All the others are flat.
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Old 08-10-2016, 19:41   #18
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Re: Thermoforming A Curved Acrylic Hatch

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Delancy - I need 4 curved ( cast acrylic preferred) windows, 3/8" thick about a 10" R. Too big to fit in a kitchen oven. Prior experience is that if you heat too quickly, you get internal bubbles ( moisture). I could use the old windows as a mold. Possible to do? HOw to heat? All the others are flat.
Ed
How big are we talking? Window panel size specifically?? I did thermoforming for 10 years, producing literally millions of parts...also R&D, prototyping and tool design...can help with input. We heated ABS, Polycarb, PET, you name it, we would heat polycarb up to 360 in as little time as 2 minutes (using IR, and cal rods, top and bottom heating) but that is the top end of the range, as it begins to really sag if only supported on the outside edges, less so for thicker sheets. The sheets once heated and cooled over a mold will shrink considerably, so make them oversize, I would suggest on the longer straight edge, and not the curve. I could go on but it's late..hit me up if you need and more suggestions...
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Old 08-10-2016, 21:17   #19
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Re: Thermoforming A Curved Acrylic Hatch

My thoughts are 3/8"? Is that the original thickness or are you trying to beef it up? If trying to beef it up I suggest you reconsider and match existing instead. It lasted this long right?

Next is are you sure you can't cold form the curve? Doesn't look compound and cold forming will get you better optical qualities than messing around with thermoforming.

Lastly where? Not sure where you are located by suggest you try to find someone with the equipment required since those are big pieces to try a junkyard oven. Try sign fabricators or people who do Corian fabrications. Most of those guys would be interested in your project just because it's off the wall and might be willing to you out just for fun if you bring them beer.
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Old 10-10-2016, 15:40   #20
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Re: Thermoforming A Curved Acrylic Hatch

If you build a plywood (door skin and some braces) form, for the panels, we hired a local pizza parlor's pizza oven after hours, once, to form dodger panels for our hard dodger, but we had the forms from the original ones. They were able to control the temperature, and we did not get many bubbles in the acrylic. As it flows, gravity will affect it a bit, so finished, some parts will be invisibly thicker than others.

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Old 10-10-2016, 16:55   #21
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Re: Thermoforming A Curved Acrylic Hatch

We make aircraft Windows. We do have a form but it's covered with pool table felt. We hang the sheets in an oven until they soften then drape them over the felt, seeing as how you have the old windows, maybe you could cover them in felt and use them to mold with.


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Old 10-10-2016, 19:41   #22
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Re: Thermoforming A Curved Acrylic Hatch

I didn't know about the felt--that's a great idea. Thanks.

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Old 10-10-2016, 19:48   #23
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Re: Thermoforming A Curved Acrylic Hatch

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Originally Posted by Ann T. Cate View Post
If you build a plywood (door skin and some braces) form, for the panels, we hired a local pizza parlor's pizza oven after hours, once, to form dodger panels for our hard dodger, but we had the forms from the original ones. They were able to control the temperature, and we did not get many bubbles in the acrylic. As it flows, gravity will affect it a bit, so finished, some parts will be invisibly thicker than others.

Ann
Please please do not follow Ann's advice and use a pizzeria oven or the oven at your home. Thermal degradation of acrylic can produce methyl methacrylate, ethyl acrylate, and acrolien. These are POISONS!!!

When I say junkyard oven I do not mean one you would eat from. I thought that was obvious.
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Old 10-10-2016, 20:22   #24
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Re: Thermoforming A Curved Acrylic Hatch

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Originally Posted by Delancey View Post
Please please do not follow Ann's advice and use a pizzeria oven or the oven at your home. Thermal degradation of acrylic can produce methyl methacrylate, ethyl acrylate, and acrolien. These are POISONS!!!

When I say junkyard oven I do not mean one you would eat from. I thought that was obvious.
methinks the comment about controlling the temperature takes care of the concern.
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Old 10-10-2016, 20:38   #25
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Re: Thermoforming A Curved Acrylic Hatch

You pays your money and you takes your choice. - Mark Twain
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