Jon's Place

Monday, April 9, 2007

CNC Milling

So, for the past week I've been working with my new CNC milling machine (its not really mine - it really belongs to the Brain Engineering Lab*, but its in my basement...)

Getting it set up was interesting, but after a few issues and a bunch of help from my brother Dave (who also has a CNC Sherline mill), I was able to get it running. I gave myself a crash course in G-code (the language the milling machine understands), and decided the free tools out there pretty much suck. For what I am going to be doing the most, which is drilling and cutting out flat panels, there is a very specific set of steps to follow:

  1. clamp down a blank panel
  2. "punch" the holes using a center-drill
  3. drill the holes
  4. mill out any interior pockets
  5. mill the outline
I found what I typically do is set up the panel I am cutting on top of a piece of 3/4" pine. If I take a #4-40 tapping drill and re-drill a couple of the holes in the middle, I can use a couple #4-40 machine screws to hold the "center" of the part down while I am cutting out the outline (between steps 4 and 5 above).

I found a macro on CNC Zone that runs in Rhino, and produces g-code from line segments (although it doesn't really do all that great a job). It produces the g-code instructions I need (plus a lot of extraneous instructions), so I wrote a little GUI in Squeak that imports a "drill file" and a "mill file" produced by the Rhino macro. This allows me to set a couple parameters, and produce a nice g-code file with comments and the pre-drill stage and so on.

Anyways, I'm having a blast with this CNC stuff, and have started work on building BrainBot's new chest compartment.

*The BrainBot project is directed and funded by the Brain Engineering Lab and Neukom Institute


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