Shopbot and Tormak

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Techniques

Speeds and Feeds

WIkipedia has a good page on speeds and feeds. In particular, you can get the cutting speeds for many materials using a high speed steel cutter. http://en.wikipedia.org/wiki/Speeds_and_feeds  Missing from the Wikipedia table is Wood. The Cutting Speed for a soft wood, such as pine, is 1000 feet per minute.

There is a recommended speeds and feeds calculator at  http://www.custompartnet.com/calculator ... d-and-feed  The calculator needs Feed per Tooth. We were told to use the following values:
  • Aluminum: 1/100th the bit diameter
  • Wood: 1/50th the bit diameter
  • Foam: 0.1
Plunge speed should be about 1/3 the feed rate.

Problems when cutting

If your wood part smokes, then either increase the feed rate or slow the spindle RPM.

If you hear screeching, they you are feeding to fast - or too slow. Try slowing the feedrate first. If that doesn't work, then increase the feed rate a bit.

Supplies

Bits

The more flutes a bit has, the more heat it generates. Typical flutes for materials:
  • Plastic: 2
  • Wood: 1 or 2
  • Aluminum: 2
  • Steel: 4
Dan-Mar Tools is a good source of bits
907 American Street, San Carlos, CA 94070
Phone:(650) 591-2651

For cutting pink foam, Matthew had a four inch long bit that was about 0.5 inch in diameter. The flutes were almost like a rasp on it. He said it would just rip thought the foam at very high speed. Great for a roughing pass.

Materials

Pink Foam

I bought 4x8 sheets of two-inch thick pink foam insulation at Home Depot. Not every HD carried it. The sheets where scored half way through every 18 inches. This material cut extremely well. I sprayed the finished piece with shellack. For a more spooky effect I sprayed it with gray paint and the material started to dissolve away a bit.