(i.e. So, how good is it?)
Now that it is all done, and I used it for a while, I can objectively measure the performance of my CNC. In short, it does everything I need it to do.
It is plenty fast: faster than any tool cutters can chip-load. Backlash is reasonably small (0.003" max), and with the help of Mach3, it is effectively zero. I do not even think about it. Accuracy? The ball screws are specified at 0.002" per foot. My external DROs measured it at ~0.0008 over the whole travel. This is 1/5 of a thousandth of inch on a 6" piece. I even screw mapped it, so now it is better than 0.0001" over the whole travel. Good enough!
Here is a movie of my first test run. The unit was half finished, and just able to run. I quickly set up the motors and the other settings. Everything moved as it should. So far so good. Then I used a wizard to crate code for a circular pocket. The idea, was to see if it will be a true circle. With trembeling hands I pressed START button, and relinquished full control to my PC. The spindle turned on, and the tool moved. With no hesitation it sunk into the Aluminum piece, and started its dance. It was amazing to watch the machine work. It took me a while to remember my camera (that is why you only see a brief sequence at the end). Note: this was my first ever CNC run of any kind. I’ve never even seen one before.
The test piece was perfectly circular. I was totally amazed how accurate it was. My digital caliper, accurately mirrored the settings I entered into the wizard – in all three axis. Then, it was just the matter of finishing it. I will never forget the feeling I had at that moment. So many hours of calculations, verifications and building have come together, and yielded a positive outcome. Not one thing was wrong. So, to the impatient out there: Take my advice, and think things through – and all will be OK.
The pendant is definitively a must. MPGs, are great - once you have them tuned to your desires.
Mach3, although it went through many revisions is working great! Thanks Art.
You do need good piece of CAM software. I evaluated Bob CAM. It is OK for the mill, but no lathe support. It is a little light for me, as I am used to MasterCam flexibility, and power. But at $400 to $1000 (depending on a level) it is a great buy. It will do almost anything you need. I am lucky to have access to MasterCam which goes for $20,000 at my level. This is due to generosity of one of my clients, who had an extra license (actually more than one unused seat - isn't aerospace great?), and let me borrow it, sort-of indefinitely. Great to have friends in all the right places J.
Finally, I would like to thank:
q Art, at Artsoft for great software. I would not have even started if it was not for Mach3.
q http://www.homeshopcnc.com for their help and parts. Thanks Rick!
q http://www.camtronics-cnc.com for advice and great parts. Thanks Dan!
q Many other suppliers who yet again came through for me: McMaster, Enco, Shars, Digikey, Newark to mention few.
q Lastly, and mostly, my wife and life partner Ana, without whose understanding and support, any of this would not have happened.