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mpmurray · Newbie Joined: 24 Nov 2005 Posts: 11

I'm trying to figure out how to cut my 3/8" thick abs plastic after it's vacu formed. It's tough stuff! Considering an electric tool (e.g. rotozip).

Does anybody have experience or ideas for thick plastic?

Thanks!

jegner · Posted: Sun Nov 26, 2006 4:11 pm Post subject:

Bandsaw is what I use for the thicker PETG plastics.

mpmurray · Newbie Joined: 24 Nov 2005 Posts: 11

I thought about a bandsaw, but I need to make a horizontal cut, whereas a bandsaw blade is vertical. My mold is bowl-shaped. So I need to go around the perimeter with a horizontally-oriented cut. Otherwise there will be a flange coming out at the circumference of the bowl (albeit thin).

Thanks, any other ideas appreciated.

jegner · Posted: Tue Nov 28, 2006 10:41 am Post subject:

Hmmm. Hows about a scroll saw, or a dremel with a cut off blade?

drcrash · Posted: Tue Nov 28, 2006 12:03 pm Post subject:

Some people use hot wire cutters. (I have a couple of hot wire cutters lying around somewhere; I should try that.)

thebluecanary · Posted: Fri Dec 08, 2006 8:35 am Post subject:

jegner · Posted: Fri Dec 08, 2006 9:10 am Post subject:

Hot wire cutters are basically used for cutting foam. Styrafoam, and others. Drafting uses these to visually illustrate 3D objects, and sculpting prototypes from dense foam cut with hot wire is great. Think of an electrified coping saw. You can make these with a sodering Iron and a coat hanger.

drcrash · Posted: Fri Dec 08, 2006 5:29 pm Post subject: hot wire cutters

Just to clarify, a hot wire cutter is a cutter that uses a hot wire to cut. (Not something that cuts wire and is hot.)

They're easy to make.

You just need

1. a piece of thin resistance wire, like nichrome (but some people use guitar high e strings or thin stainless steel wire)

2. A bow of some sort, which can just be a C shaped thing plus a spring or something to keep the wire taut, and

3. a low-voltage power source

You stretch the nichrome or whatever taut across the C-shaped thing, and wire it to the low-voltage power. The current through the wire heats it up, and it will slice through styrofoam or (more slowly) other plastics.

A better one will have variable power. One way to do that is with a dimmer switch and a step-down transformer. (Which you can get for a couple bucks at a thrift shop.) You wire the dimmer to AC, and then wire the wall-outlet-voltage side of the transformer to the output of the dimmer. Then you wire the resistance wire to the low-voltage side of the transformer. When you vary the voltage through the dimmer, it will vary the (lower) voltage across the hot wire, scaled down by the transformer.

There are lots of articles about how to build small and large hot wire cutters out there on the internet, especially on model-building sites. (People use them for cutting wing cores out of blocks of styrofoam.)

I think I got my little one at a craft store, where it was sold for cutting floral foam or something. (Then I found a transformer and wired it with that so I didn't need batteries.)

If you have the wire at the right heat, and move it through styrofoam at the right rate, it vaporizes the styrofoam without ever actually touching it, and you can make incredibly smooth and straight cuts through lots of foam. If you use a guide on either end of your foam block, you can get some sweet simply-curved surfaces out of it, and some compound curves. (RC modelers use templates for the ends of wings with different airfoils and angles of attack, to get wings that gradually transition from one size/shape/angle to another across the length of the wing.)

Don't breathe the fumes, though. The gases in some foams' bubbles are not good to breathe, and vaporizing the plastic may release other stuff that's not good to breathe. Use in a well-ventilated area.

drcrash