Hello all- I just bout a Shapeoko XXL and finally put it to the test. I have some experience with CNC woodworking using a much smaller machine I purchased a few years back. My first test consisted of a number of circular holes, including some shallow ones with smaller, deeper ones in the middle, and then some larger contours cutting all the way through my material but held in place with tabs. I’m cutting into baltic birch with a 1/4 endmill.
My first test was quite disappointing. What were supposed to be circles were ellipses or worse, and deep circles that were supposed to be directly in the center of shallower ones were very obviously not centered. A “notch” that was supposed to be perfectly horizontal was not. My outside contours worked out better, but there are a few points where the machine jogged a little off course and made nicks in otherwise straight lines.
I decided to tighten all three belts quite a bit and the eccentric nuts slightly. A second test shows a lot of improvement, but the problems remain on a lesser scale. This second time I can still tell with my naked eye that circles are not quite circular and other things are not quite perfect. I’m not sure about tightening the belts any more because I really think they are as tight as the manual said to make them. The v-wheels can be moved by hand, but not without resistance.
I’m confident my workpiece is fully secured down (using clamps and threaded nuts in my wasteboard with bolts and washers), so I’m sure that’s not it. What else can be done? Thanks in advance.
If you continue to have difficulties post a .c2d file, generated G-Code, step-by-step instructions on how you are securing your stock and setting zero relative to it, and a photo of the failed cut still secured on your machine and we’ll do our best to work through this with you.
Thanks so much for your reply. I’ve made all of the mechanical checks and didn’t find anything that seemed wrong. I did some more tests of circles and I am consistently getting circles that are wider on the y axis than the x axis. I even rotated the exact same circles 90 degrees in CC, generated new code and then cut them again, and the problem is still on the y axis. A circle that should be .275" in diameter ends up being .276" on the x axis (which is plenty accurate for my purposes) but .3" on the y axis. I’ve tried it both as a “pocket” and “inside / left” and got the exact same result.
If you’d like to see the .c2d file, G-Code and other information I can provide that, but I thought the above information might be a clue first.