Copying Guerrilla guide to cnc-mold-casting
Following are planning notes and a build-log for Mike Lutz's attempt to copy the processes laid out in the Guerrilla guide to CNC machining, mold making, and resin casting
Contents
What got this started
Mid october 2012 the Guerrilla guide to CNC machining, mold making, and resin casting became the top link on ycombinator's Hacker News. Mike stumbled upon it there and posted a note to the LVL1 list about it.
That lead to the discovery that the club had an offline Zenbot_1216_CNC, and through large amount of work (of which, much of the work was done by Chris Pettus), the Zenbot was brought online.
Having gone through the zenbot setup process, and feeling as though that gave him some idea of the depth of "rabbit hole" that the Guerrilla guide was presented, Mike decided to continue to copy the steps in the guide and see how far he can get.
The phases
The Guerrilla guide bounces back-and-forth between six primary skills: Building up a CNC, Designing 3d parts (gears) in CAD software, Making G-code with a CAM package, Milling a high spec model from a CNC, Making a Silicone mold, polyurethane casting from the silicon mold.
FYI, a nice guide to all of the options available for the various software needs is at: http://www.probotix.com/cnc_software/
Building up a CNC
The CNC being used for this adventure is a Zenbot 1216 and all of it's details can be found on it's equipment page.
The Zenbot 1216 isn't one of the CNCs that is listed on the Guerrilla guide. While all indications are that it should be able to operate on the order of 1/1000th of an inch, we have yet to do any cuts that would illustrate that resolution, nor is it completely clear what resolution the Guerrilla guide is advocating.
with 1/8th steps (our machines finest mode (driver limited?)) there are 1112 "1/8th steps" per inch. With a modern Zenbot 1216 it looks like the stepper have been improved, they would be 2224 "1/8th steps" per inch, and can now also drive at "1/10th step" (for 2780 per inch).
The closest CNC on the Gurrilla guide (by price and size) is the fireball V90. This claiming to be able to do 1/8 and 1/16 steps, with "1/8 steps" giving 8000 steps per inch (or 1/16th giving 16000 steps per inch (wow!)) (... strangely they say that is the "X and Y" resolution, it kinda looks like Z might be even higher spec then X and Y but I can't clearly find that.
The Guerrilla guy says he bought a Roland MDX-15 (so presumibly that is the level of machine needed to make the type of parts he shows in his guide). Its kinda hard to understand the specs for his machine, it says it can do .000984 in/step software, and/or .000246 in/step mechanically. I don't know if high res happens if you enable fractional steps, or if thats as fine as it goes with the fractional steps.
If thats as find as it goes, then his machine gets down to 1016 steps per inch (seems like that might be underselling his (twice as expensive) machine, but if its true, then maybe we are in good shape with our CNC. (... note, at the start of the article he talks about 0.001 mm resolution in all axes, that would be on the order of 25,000 steps per inch)
Making 3d designs in CAD software
The first big problem is picking which CAD software. I'm trying to find free mac software, that makes things much harder. And, there are now weird option like the HTML5 3dtin.com HTML5 package.
