Is your Z axis delrin nut worn in? This can cause incurable slop when changing directions and, including myself, I’ve seen several people in the forums receive warped ACME rods which cause wear in the threads of the delrin nut, eventually leading to increased slop in the rod/nut fit and poor stiffness. So, the error in the X axis motor was really tiny and not perceivable, even though it must be in I’m not sure if this is the cause of your circle problems, but this is what I’ve found in my case. It doesn’t make a smooth arc–it makes lots of little tiny straight lines that overlap to create the circle shape. The reason it didn’t happen with Estlcam, is because the way the GCode for a circle is calculated in that software. I marked the pulley and shaft and they remain in the same place during operation. I will see about getting a new one from Inventables. The issue isn’t as important on the Z, and the incorrect movement is smaller due to the screw. I swapped the X and Z axis motors and the problem is gone on the X axis. However, if the motor is being held in place by current this doesn’t happen. Then when the direction changes the same is true. So if I have it jog 1mm, it is only moving 0.5mm on the first step and then 1mm each step afterwards. My X axis stepper motor in not moving a full distance per step, but only on a direction change. I have a stepper motor that is not responding properly. I have found the cause of my circle issue. It just looks like the same wrong shape scaled up or down. But the circle shape produced is consitently the same (imperfect) shape from 1/8" all the way to a 6" diameter test that I tried. I cut an S pattern to check for backlash in the X axis and the results were perfect in Easel. I haven’t tried generating the gcode in Easel and using UGS to carve, but that should produce an imperfect circle as well if the problem is Easel. The size of the circle doesn’t matter either. I’m not losing steps… They just don’t happen, like they aren’t in the code. The circle was perfect along the Y axis, but had a very slight flat spot at each of the X axis extremes–we’re talking only 1 or 2 tenths of a mm–but it is noticeable. I flashed my Adruino back to the X-Carve GRBL and tried the same cut in Easel. Perfection! This makes me question Easel and how toolpaths are calculated for circles. Then I tried cutting a circle drawn in Inkscape with Estlcam and UGS. My machine is dialed in and is very accurate on everything (steps per mm are dead on), even arcs and curves–but the perfect circle is like the holy grail… I have had some issues with perfect circles as well. I have found something interesting when I was carving today.
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Here is a glance below of all of the prints cut out, and my kids enjoying them.
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