The system I use has a rod heater. It is a metal frame with a 1/2" x 1/2" depression running down the center. That holds a heating rod, (element). When it gets a dull red hot it is time to put on the acrylic.

The way I time the heating is when the very edge just starts to deform from a square cut, (I use only cell cast acrylic so that starts at about 400*F), it is ready to bend. If you try to bend it and it resists too much, immediately straighten it out and put it back in the heating position for a little bit.

The bending jig is just a slot between two boards. You have to calculate the exact distance to end up with the right bend. Trigonometry. The placement of the plastic on the heater determines just where the bend ends up. You must leave it in the jig till it cools quite a bit, a fan helps a lot. If you take it out a little too early it will unbend a little by itself. Then lots of luck trying to reheat it and rebend it, nearly impossible.

As far as a large radius, never done that. You get a fairly small radius, about the thickness of the acrylic. For a formed bend I would assume that a from is used and the plastic is heated by hand for small quantities with a heat gun.

For large industrial quantities the plastic goes through an oven and then into a forming unit that has a mold and pressure and is usually chilled by water running through the mold.

Oops, more info than asked for again.

Philadelphia, PA (Really Bensalem)

Harvey's Sub Page When you finally understand it completely... it changes.

Harvey,

I like it when people give more information than was originally asked for. When I'm learning something new I don't always know what to ask, or another approach is sometimes better.

You mentioned 400°F for cast acrylic. Is the temperature for extruded acrylic different?

It sounds like: don't heat it enough its hard to bend, heat it too much it'll slump if not supported.

Has anyone on this forum tried using a form? Are there materials to use, or to avoid? (don't want sticking) How do you shape it without distorting the surface finish? Can you cool it with water without disturbing the finish? What am I not asking?

Overheating will sometimes cause bubbles to form inside the acrylic as well as slump. It should be hot enough to just bend without using a lot of force, but a little force should be necessary, it should not just fold too easily, needs a few, (3-5?) pounds of force for about one foot of fold. If you have to go past about 20 pounds per foot, it is not hot enough.

Cell cast acrylic needs the highest temp, continuous cast needs lower temps, extruded needs the lowest. I have seen some extruded that would melt easily in boiling water. If you are using extruded, dip a piece of scrap in boiling water for a bit and then try to bend it. That will give you a good idea on how much temp you will need. I am told that an IR heat gun will not read properly on a shiny surface, but believe that anything stuck on the plastic will leave a mark after reaching folding temperature, so that will not help.

The main difference in the acrylics is the composition. The cell cast is made with mainly polymers with just enough monomer to cover and hold it together. Continuous cast uses more monomer to be able to cast in that method. Extruded has a lot of monomer in order to be forced out of a slot in that manor. Monomer melts at a very low temperature.

Philadelphia, PA (Really Bensalem)

Harvey's Sub Page When you finally understand it completely... it changes.