Forming huge plastic sheets.

Jens Schuetz

Jens Schuetz

Joined
Jun 24, 2013
Messages
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Hi, im currently working on building a cuirass, which is basically one armor plate on the torso front and another one in the back joined by straps.
Sounds like a cool WIP and I'd have done it but at the moment it's more QIP (question in progress) or maybe even FIP (failure in progress)

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To form the armor I made a cast out of plaster of Paris and filled it with concrete. The concrete I smoothened with plaster of Paris.
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Now I want to heat 0.16x24x48 ABS plastic (after drying it) and put it over the shape and let it be sucked down by a 2x4 feet vacuum forming table.

The problem is I can't fit that big of plastic into our oven.

What do you advice?

Could a heating lamp or 2 heat it evenly enough or would one part melt why the other is still solid?
Could I build a big box (wood+ aluminumfoil) around the vacuum forming table with the lamps up high, maybe add a fan and hope it distributes more evenly?

Should I forget about the vacuum and attack it with a heating gun starting from the most elevated part of the shape?

Maybe cut the sheet into smaller sheets 2x1.5 feet and shape them one by one? Would putting soft plastic on an already shaped cold plastic join both them strongly enough?

Thank you for your help and of course open to any suggestions based on real experience or simple brainstorming and out of the box thinking.

Thank you for your help with this.
:-)
 
I don't believe joining abs with heat will work. I think MEK will work, but I've not tried it. I'm not visualizing how you would need a 2'x4' piece for a breast plate. Regardless, I think if I was going to try this, I would rig up a piece of sheet metal a bit larger than your sheet. You could then suspend this a good bit over a heat source maybe a large bed of coals. You wouldn't need more then one layer of charcoal spread over an area the size of your "griddle". The whole idea is to get the coals nice and even, and get the metal plate at a temperature that can be held consistently. The thicker the metal plate, the easier this will be to accomplish. Between 300°- 350°f. An infrared thermometer would be a must. I'm starting to sound like JT with the complexity, but I'm attacking the problem from where I have experience- primitive cooking. Handling a sheet of that size will be difficult no matter how you decide to heat it.
 
kdogmcg said:
I don't believe joining abs with heat will work. I think MEK will work, but I've not tried it. I'm not visualizing how you would need a 2'x4' piece for a breast plate. Regardless, I think if I was going to try this, I would rig up a piece of sheet metal a bit larger than your sheet. You could then suspend this a good bit over a heat source maybe a large bed of coals. You wouldn't need more then one layer of charcoal spread over an area the size of your "griddle". The whole idea is to get the coals nice and even, and get the metal plate at a temperature that can be held consistently. The thicker the metal plate, the easier this will be to accomplish. Between 300°- 350°f. An infrared thermometer would be a must. I'm starting to sound like JT with the complexity, but I'm attacking the problem from where I have experience- primitive cooking. Handling a sheet of that size will be difficult no matter how you decide to heat it.
Click to expand...
Thank you! I don't need 2x4 but I need more than the oven size and the sheets came in 2x4. I can cut them down a bit (2x3 leaving a few inches room at the side). Also like your metal sheet idea since that metal will probably distribute the heat more evenly.
What do you think of having the metal on top of the ABS and then heating it. This way whatever ABS will reach the right temperature will start to sag through and thus not get overheated.
Thanks again!
 
I would set up a battery of IR heat lamps. Any fine fitting in the curves can be done by moving a lamp closer in that area. Use gloved hands to form the plastic.

Many years back a friend and I formed a sheet of acrylic into a shaped dome by making a negative mold and placing the hot sheet over it. We tossed a canvas tarp over the hot plastic, and dumped several bags of sand on it. The sand pushed the acrylic down into the mold and held it tight as the acrylic cooled. The canvas left a textured surface that looked pretty good. We didn't have the big vacuum bags that are around today to do that sort of thing.
 
I was thinking of a solid sheet for the griddle. The it lamps would be better I think , but I assume you don't have them. If you have help, multiple heat guns may work.
 
Oh. I think you mean sag down into your mold I think it will cool before it hit bottom. If you can lay it over the mold with multiple heat guns, you could forgo the metal plate altogether.
 
Fwiw, the only way to join ABS is welding, either heat or chemical.
Heatwelding a much better method for joining sheets, with advantage that areas can be built up by filling in. Just like metalworking.
 
I'll go with the lamps then. The clamping fixtures and bulbs are surprisingly cheap.
Will make a little frame and hang them from there. I'll start with 4x 300 Watt and will experiment with the distance.
Will also get an IR thermometer!
:-)
Thank you!

Lieblad I also saw friction welding which seems very clean and only needs one hand. I'd have trouble coordinating two, one with a rod and the other with the heat source. I'm a Klotz.
 
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