Matt Groh

Computer-Controlled Machining

Here's a recap of making something big with a ShopBot machine. This machine is huge. I used a 4' by 9' piece of plywood, and there was still plenty of room on the cutting surface of the machine. Since it's mid-October and way before Christmas, I thought it would be cool to do something impractical for the moment that could be really fun in a couple months: build a Christmas tree. I downloaded an initial design on GrabCad, and I edited it in Rhino to make sure the width of the slots match the thickness of the board, which is about .45 inches. Then, I added an extra slot and a star. Because what's a Christmas tree without a star or angel on top.

The machine is quite dangerous--it spins a quarter inch thick mill head at 10,000 RPM (at least that's what I set it at) to cut through the material on the sacrificial layer. So, every step along the way, I double checked with John or Tom to confirm that things looked okay. And the machine is quite loud. Here's yours truly, Monsieur Six Eyes, with some ear muffs

Here's a break down of the steps

  • Make sure everything is turned off.
  • Place plywood on sacrificial layer. Fortunately, someone else already placed the sacrificial layer on the machine, so I did not have to do that. The idea behind the sacrificial layer is if the machine cuts to deep then the sacrificial layer gets cut up rather than another part of the machine.
  • Screw down the plywood to make sure it's perfectly flat. Redoing milling for electronic circuit boards is really boring and annoying, so I wanted to make sure everything is done right the first time. Likewise, if stuff isn't flat, things get dangerous.
  • Screw the mill head into the machine
  • Attach the spray guard around the mill head
  • Upload the files to VCarve Pro
  • Connect all the lines and set up the traces
  • Turn the machne on
  • Zero the X,Y coordinates at the edge of the board
  • Zero the Z coordinate with the metal device
  • Test the traces out in the air
  • Turn the dust collector on
  • Run it!

Here's what it looks like while running

And some stills, mid-machining and post-machining

When you cut out pockets, which I did to make designs on the tree, you create a lot of dust. So, last but not least is cleaning up with a vacuum.

Et voila! Ho ho ho. Check here if you want to know if it's Christmas.