Hot Forming Polycarbonate windows

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Hot Forming Polycarbonate windows

Postby UK-Corlett » Tue Sep 19, 2017 7:52 am

Hi All

Thanks to all who contributed to my first post on this subject and guided my decisions.

The main feature of my 'Short Wife Standy' Tear Drop design is its wrap around front window. I am hopeful that the window will be an extension of the side windows and look like just one black line wrapping round line side to side.

Image

The design is a mix of styles from other builds but a little unique and so copying other people has not been an option. See my other posts on light weight ply/foam composite construction.

This could be a lengthy description but instead I will keep it punchy and assume if anyone is interested they will ask. Yes there are 25.4mm in an inch.

Polycarbonate v Acrylic = More resistant to impact.
Thickness = 3mm is on the thick side of what I was recommended I am just not brave enough to go thin.
Technique = Drape moulding. Essentially at temperature it should just droop over what ever it is resting on.
Temperature recommended = 155C Actual 150C to 165C measured mid oven.
De-gassing recommended =125C for 4hrs Actual 100C for 6hrs
Cycle time (mins) - 15 to temperature; 15 to 20 at temp; 10 to cool to 100C door closed, 10 to 70C before lifting out; re-tool and load oven 15. Say 1hr 15min per run.

I took a pattern off the window. 6x3mm thick 40mm wide strips of plywood clamped and PVA glued.
From this I set in a sheet of 1mm Ally and built wooden supports to keep its shape. I used Glass tape a Oven Flue Sealer (max temp 300C)

Image

I built an oven walled with rock wool

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Heaters were parts for fan assisted ovens and temperature controller was of the bulb type.
Heaters were 2kW 230V rating and wired in series for 1.25kW
(Later I took one out which raised the power to 2.5kW but left both fans running.

Image

1. Test runs I encountered the following problems
To hot – bubbles formed in the material – Solution de-gas as suggested by the manufacture
Cold lip curl – The sheet would curl up at the ends which could have been cold and in the middle which could again be to cold.

Image

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2. Tests runs
I Decided to use a top clamp to hold down the curl edges.
This gave rise to marks under the clamps, solved by loosening the clamps a little.

Image

This image shows the clamp in place, the red object is a meat thermometer, cool down took longer that I thought.
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Here the bent ploycarbonate is fully con-formal to the tool.
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I now own a stock of windows for all eventualities. One set will be covered with tinted film and fitted to the TD.

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If I had my life to live again.
1. More heaters to even out the temp across the oven.
2. Line the oven to remove all the fibres of rock wool.
3. Do in a clean room and not my garage.
4. Run cooler and longer and out-gass for longer and cooler.

Clive

See also build journal http://www.tnttt.com/viewtopic.php?f=50&t=63510
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Re: Hot Forming Polycarbonate windows

Postby aggie79 » Tue Sep 19, 2017 8:13 am

Fantastic solution Clive! Well done. And thank you for the detailed descriptions and pictures. :applause:
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Re: Hot Forming Polycarbonate windows

Postby working on it » Tue Sep 19, 2017 11:19 am

  • Your polycarbonate-heating oven surely worked better than what I used to bend and form a 3/4" sheet once. Clever and resourceful. I, on the other hand, may be regarded as a shade-tree mechanic, and my methods are often cruder.
  • I once owned a '86 Chevy S-10 Extended-cab pickup (for 18+ years, before it got T-boned). I had very little room for tools in the small Delta box in the bed, and none inside the cab, so when I started carrying two 100+lb boxes of tools with me (I was always needing them when working on automotive projects at various locations, for friends and family), I had to leave them in the bed of the truck. I also found that the 200+ lbs of extra weight on the tail end of the truck enhanced traction, especially in wet or snow, so I made a locking cover for my boxes, that covered and secured them in place. The cover was made from polycarbonate sheet, because I liked the durability of it, since I had experience cutting, forming it into shapes, and drilling/bolting it to other materials (I used it for covers, guides, safety devices on the various machines I used at work, in a newspaper production facility).
  • My polycarbonate supply at work was only 1/4" thick, seldom thicker, so I bought my 3/4" material at a supplier near home. It was expensive, even back in '92, when I built it I constructed a bending brake from 2x4's I had at my Dad's house (I lived in an apartment at the time, after a divorce, thus needing to secure my tools), and used a hand-held Bernzo-matic torch to bend it into the shape I wanted. I used the torch a bit too closely to the wooden brake and polycarbonate, charring the wood, and causing bubbles in the polycarbonate, but it looked pretty good. The material was formed into a sloped wing-shape, to cover the toolboxes, allow wind and water to flow under and over the wing (and waterproof Contico toolboxes), with holes drilled to use hood pins with polycarbonate spacers (from scrap pieces at work), to hold the cover to the bed floor, and on the bed sides. I cut additional angles so the cover would taper up from the narrow bed, to the wider bed sides, and rest on spacers there. I also drilled a hole on the left side of the tailgate so I could put a hood pin there.
  • I used matching padlocks on the four pins holding down the cover, and a separate trailer coupler lock on the tailgate. I painted the inside surface with the same metallic charcoal grey as my truck body, as contrast with my black bed box (inside bed mount, not one visible over the rails), and the black bedliner. I also applied a large red Chevrolet decal on the underside of the cover, before painting it, so it was strikingly well-done, especially for a first attempt. Later on, I used the other half cover temporarily while repainting the first, and quit using them after I started driving larger pickups daily, with the old S-!0 being driven for a while by my second wife. The cover(s) were used from '92-'03, and got thrown away after the truck was totalled in '04.
  • While it served me well, protecting my tools (with the added benefits of better traction and 1 mpg gas savings), it didn't have the seamless look a properly formed (with a forming oven) plastic should have, and despite that, it drew many favorable comments as a great idea, but mediocre execution. Polycarbonate is so pricey now, that I would use steel or aluminum as my medium, instead, but I used what I had been using weekly/daily to repair items at work. Perhaps, now that I've built a TTT entirely from plywood, I might use it to do the same thing...now to find a good S-10 ....
  • similar S-10, but mine was dark grey.jpg
    similar S-10, but mine was dark grey.jpg (79.4 KiB) Viewed 478 times
    my S-10 was grey, and I wish I still had it
  • S-10 polycarbonate tool box cover.jpg
    S-10 polycarbonate tool box cover.jpg (99.91 KiB) Viewed 478 times
    crude shadetree mechanic-made polycarbonate toolbox cover
  • 2013 HHRv,"squareback/simple" TTT, semi-offroad? 4x8, 2000+ lbs travel weight
  • featuring:
    • 3500 lb Dexter axle,
    • 27x8.5-14LT tires,
    • LED lighting,
    • A/C & heat,Optima AGM battery,
    • extended-run 2500w generator,
    • Coleman dual-fuel stove & lantern
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Re: Hot Forming Polycarbonate windows

Postby UK-Corlett » Wed Sep 20, 2017 3:34 am

Thanks for your support aggie. A lot had to go write so it was a bit stressful.

Hi 'Working on it'
The material was not cheap a single sheet of Polycarbonate Clear 3050 x 2050 x 3mm Cut into 6 strips 2030mm x 445mm was including Tax £147.96p But free delivery.
Manufactured by www.nudec.com A dutch company I think "NUDEC-PC" They had a good how-to technical guide.
I could have bought less but it would have been more per sq meter so a full sheet was the way to go and gave me enough for test material ans well as the making spare windows.
The spare windows will of coarse be wrapped up and put in the loft for the day a brick hits the TD.

Clive
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Re: Hot Forming Polycarbonate windows

Postby working on it » Wed Sep 20, 2017 9:25 am

UK-Corlett wrote:Thanks for your support aggie. A lot had to go write so it was a bit stressful.

Hi 'Working on it'
The material was not cheap a single sheet of Polycarbonate Clear 3050 x 2050 x 3mm Cut into 6 strips 2030mm x 445mm was including Tax £147.96p But free delivery.
Manufactured by http://www.nudec.com A dutch company I think "NUDEC-PC" They had a good how-to technical guide.
I could have bought less but it would have been more per sq meter so a full sheet was the way to go and gave me enough for test material ans well as the making spare windows.
The spare windows will of coarse be wrapped up and put in the loft for the day a brick hits the TD.

Clive
That's the whole point behind using polycarbonate...it should resist the brick, and survive, unlike glass (or in regards to my "cover", better than thin sheet aluminum or steel). The type/brand of polycarbonate I used back then is lost in the fog of time, now, but I'm sure a 4x8 sheet of 3/4" thick polycarbonate of any type would be in the several hundred dollar range. I obtained a sample piece of some Makrolon a few years back, about a 1/4" thick, to make a model of a Wiley window. Free. My model didn't work as I wanted, so I didn't order the full-size piece of MR-10 Lexan (with Margard coating) that I wanted (w/ dark grey tint), priced at about $750 for a 3/8" thick sheet (4' x 8') to cut out two 24"x 18" Wiley windows, and spares, with some left for portholes for insetting into the doors (my trailer uses 3/4" solid plywood doors, cut into the walls, without any viewports). I really wish my woodworking had been good enough to make the Wiley windows, but my model wasn't very good. The full-scale windows with MR-10 would've been nice, if expensive, if only....I ended up using 18"x 15" awning windows from Grant at Lil' Bear.
  • 2013 HHRv,"squareback/simple" TTT, semi-offroad? 4x8, 2000+ lbs travel weight
  • featuring:
    • 3500 lb Dexter axle,
    • 27x8.5-14LT tires,
    • LED lighting,
    • A/C & heat,Optima AGM battery,
    • extended-run 2500w generator,
    • Coleman dual-fuel stove & lantern
  • 147697148333125895
  • 148599148106
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Re: Hot Forming Polycarbonate windows

Postby UK-Corlett » Mon Oct 02, 2017 9:15 am

I have now fitted the windows

149681

151321

I made the windows a little long and so the final operation was to cut them to length. Do to my inaccurate fitting of the window bezel it also allowed me to cut the ends off square to fit the wonky uprights.

There was a little relaxation of the bent sheet. I made them a little less curved as I thought it would be better wrapping on than the ends touching and the middle pushing off. But I needn't of bothered as 2 weeks in my bedroom and they relaxed a little.

Not difficulty bonding them in only the usual difficulty of making it neat.

I have a man lined up who will put tint film on the windows. I have done this myself and know how easy it is to make a pigs ear of it.

I hope this gives confidence to others wanting bent windows. As new shapes are possible.

Clive
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Re: Hot Forming Polycarbonate windows

Postby aggie79 » Tue Oct 03, 2017 8:52 am

:thumbsup: :applause: :thumbsup:
Tom (& Linda)
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