Please help! I have never felt so defeated in my life! In the last month I built my new Lead 1515 fully loaded CNC. I have it setting on the Open Builds modular table. Everything seems to be going fine other than cutting circles. I've spent countless hours the last week reading the forums, Facebook group and doing testing and still cannot get my machine to cut circles. Just today I: -wiggles the router bit to see if anything moved or seemed loose and it all seemed tight. -checked for loose screws. -calibrated machine using 46" length in each direction and getting the measurements as close as possible -tightened all the couplers and nuts -made sure the spindle was perpendicular to the table -ran a 3x3 square (manually entering 3" intervals in different direction, not programmed) in each corner (using a 1/4" up flute router bit) -checked for squareness and if it's out of square, it has to be less than 1/32" over a 45" x 45" area. For a machine like this I would say that has to be pretty good, right? -once the machine was confirmed to be tight and square, proceeded to run some circles. Programmed all different ways. I tried cutting circles: -with inside cuts with machine going both directions. -drill first then pocket to get to 3/8" hole -2mm depth passes at 500 mm/min Nothing seemed to work. So I got out my calipers and started measuring my cuts figuring I could post on here and see if anyone can offer any guidance with what you're seeing from the pictures.
How did you calibrate the machine? With a very pointy V-bit, or a round endmill? You said you got it as close as possible. With a pointy bit run along a meter/yard stick, you should be able to get it pretty much dead on. In your GRBL settings, are both the X and Y steps/mm the same or did you arrive at different values for each?
Using a 1/4" bit cut a straight line at -.125. Moved the machine 46.125", measured the inside cuts which should have been 46". My values changed very little from when I did the initial calibration with calipers and only going 6". And for measuring the squares I cut, there could have been some frays or saw dust making a slight difference on the numbers. But there wasn't any glaring issues with my measurements that I thought would give me ovals instead of circles.
It seems slightly (ever so slightly) off in one direction. If you have a V-bit, try this. If you are calibrating by measuring cuts, you will probably never be accurate because very few endmills are actually the diameter they claim to be. Most are slightly smaller so therefore, if you used those measurements to enter your steps/mm, they could be incorrect.
Thank you for that video and tip for calibration. I will give that a try. Is it possible to calibrate both y motors? Or are they assumed to have the same values?
Well I think that did the trick. After using your method of calibration, my values did change. X went from 198.12 to 198.02 Y went from 198.08 to 197.91 I ran a bunch of circles with different programming setting and each one came out much better. There is still a slight (like .002-.004) difference in the measurements, but I am pleased with the results. Thank you for the help!
