Friday, December 30, 2011

Foam cutting table overview and possible redesign

A couple of years ago I posted a video on my YouTube channel of a foam cutting table I built for some terrain projects. The design is pretty simple and there is nothing hidden in it. You could probably build one from just the pictures but I figure any help I can give with the details may help if you want to build your own. It will also give me a chance to give some suggestions on making it better.

The parts list:

  • 1/2 inch wide aluminum bar stock
  • wood battens, I used some scraps of 1x2 but anything up to 2x4 will work. The small stuff is just easier to work with.
  • laminate topped wooden board, mine is a counter top off cut. An old laminate shelf at least 12 inches deep would also work.
  • wood screws
  • eyelet screws and bolts
  • bolt, wing nut and washer long enough to go through your choice of wood battens
  • 22 gauge wire
  • toggle switch, I used a paddle with an LED "on" light
  • 12v 1.3a power supply
  • nichrome wire, got this from Woodland Scenic. You can also used some types of guitar or piano wire. You just may need a beefier power supply

The design:
If you have ever seen a scroll saw the design will look familiar. You are building the same thing just replacing the saw blade with a piece of wire. The second difference is in the tilting mechanism. In a scroll saw the base tilts to allow for angled cuts. For the foam cutter version it is easier to tile the wire than the base so the arm is designed to pivot giving the same effect. Lastly the base size is larger. This makes it easier to get the piece flat against the table for better cuts or working with large pieces of foam. The arm the wire attaches to is made of aluminum. This material was chosen because it is easy to work with and springy. This last feature simplifies the design by not requiring any extra pieces or springs to keep tension on the wire.

The electronics:
To keep things simple the power supply is one of those generic "wall wart" dc power supplies. The one I used is a 1.3amp 12 volt unit. Mine came form an old answering machine or something like it. I never throw these things out because they always can be used for other purposes. If you don't have they can be found all over the web or at Radio Shack. Really though if you are going to buy one check eBay for tattoo power supplies. They are under $20 and work great. They also have variable output voltage so you can adjust the wire temperature and in some cases foot pedal on/off switches. This is really nice because it allows for hand free operation.

The wiring is a basic circuit. It is a simple on/off circuit. The diagram below has a couple of optional features. First the pilot light. This can be bought as an assembly, part of the switch as I did or even built manually. The second is the push button/foot switch. If you went with a tattoo power supply this wiring is already built into the power supply. Otherwise you will have to make the switch yourself. I am not going into that here because I don't want to turn this into an circuits 101 course.

The improvements:
The basic table I built has a few issues. It works great for freehand cuts but for precise cuts I need to add a rip fence like the one on a table saw. Make the arm height shorter, maybe 3 or 3.5 inches. This allows for less flex in the wire and gives a cleaner cut. Finally add a stop the arm pivot at 90 and 45 degrees. Getting square or repeatable cuts is a problem without this. The final thing is moving to a thicker gauge wire. This again pulls some of the flex out of the wire giving better cuts.

That is it. Get to building.

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