Good afternoon, So I have a longmill 30x48 machine new build. I have a X32 controller. I calibrated steps for 8 inch square and carved (60 degree VBit) and its right on. So then I carved another profile (60 deg VBit) for a 16 and 25 square as well. The issue is while the size 8 square is right on (x and y) the 16 and 25 are not, they measure right on in the X but off on the Y. The measurements are 16 1/8 and 25 3/16 in the Y. The x axis is on size for all squares. I thought maybe I was losing steps and ran the job 3 times. It followed the same paths all 3 times. My question is if its skipping steps wouldn't the path change in the Y or is skipping steps exactly repeatable? I also have the Y axis wired in parallel because I have a 4th axis. I turned the current up all the way on the Y originally cause the y axis steppers were stalling. That seems fine I don't have any heat in the steppers when I'm running the jobs. I slowed down the Y axis maximum rate to1200 mm/min also. I also disconnected the ballscrew bearing so I could move the x carriage back and forth. No binding or slop very smooth motion. I barely had to adjust the backlash and moves smoothly no play. It appears to lag in the Y briefly when it goes from x to y in the corner of the squares. Not sure whats going on.
If you lose steps you don't get them back again. A square or circle would end up not lining up when it got all the way round. Slowing down for corners is normal. Re-calibrate your Y axis over the longest distance you can accurately measure. Alex.
PS, I don't recommend making a cut to calibrate - that includes any backlash and tool deflection into the calculation. Use the V bit as a pointer for the measurements. Once you are sure you have your steps/mm correct then a shallow cut will indicate if there are other problems. Alex.
I calibrated initially with a steel ruler at 8 inches which turned out great for the profile carve. If I readjust for a longer measurement now won't that then throw it off at the 8 measurement? I have a good 8 inch square now but the 16 and 25 are off. I don't understand how it can be right with one and wrong with the others. You would think it would be off a bit but 3/16? I'm not trying to be difficult I'm just trying to understand whats going on.I appreciate your input and thanks for helping!
Explanation in the link below. Don't calibrate with a cut - that includes other variables like backlash and tool deflection. Our leadscrews are not "perfect" - deviation is very small but it does exist. Calibrate your steps/mm first without making a cut. If a cut after that is not accurate it is caused by something else. Calibrating your cnc Alex.
At 8 inches, there may not have been much of an error to see visually. It is also way too short of a distance for calibration. In that short of a distance it may be hard to visually see that it is off. Over 30 inches, you will definitely see it. For example, when I set mine up, I tested over a distance of 1000mm and my machine went 1000.3mm. I would have never noticed that error at 200mm (8 inches). The longer you calibrate over, the more accurate it will be.
