Trouble getting round circles!

Ok - this is an issue I have had since I put my x-carve together - I have read all of the threads and none seem to address my specific issue.

My circles never come out completely round. I have confirmed my belts are not too tight, or too loose. I am using NEMA 24 stepper motors with an X-controller to power them. I was told by inventables that its not necessary to adjust the pots on the X-controller to get the best power like with the old power supply. my set screws are tight. I have recently re-calibrated my steps/mm and in X and Y axis they are coming out dead nuts on over 600mm travels.

Now I used to think it was caused by flexing of my Z-axis under load - to which I have replaced my Z-axis with a rod/bushing style opposed to stock.

Fast forward to now - I am using a laser to engrave things and thus ZERO LOAD on the actual machine on the Z-axis along Z-axis which would cause a flex while making a circle. Still encountering circle issues!!

Attached are photos of a recent laser carve which are demonstrating my complaints

Note the bottom of the two concentric circles around the main logo

note the tips of the feathers on the wings. the entire engrave should have an equal space along the outline of the feathers.

Designed on Vcarve Pro, using UGS or GRBL Sender (to troubleshoot a programing issue) as programs to send g-code. Running on GRBL 1.0c

Current Settings:

Grbl 1.0c [’$’ for help]

$$
$G
$0=10 (step pulse, usec)
$1=255 (step idle delay, msec)
$2=0 (step port invert mask:00000000)
$3=4 (dir port invert mask:00000100)
$4=0 (step enable invert, bool)
$5=0 (limit pins invert, bool)
$6=0 (probe pin invert, bool)
$10=3 (status report mask:00000011)
$11=0.020 (junction deviation, mm)
$12=0.002 (arc tolerance, mm)
$13=0 (report inches, bool)
$20=0 (soft limits, bool)
$21=0 (hard limits, bool)
$22=0 (homing cycle, bool)
$23=3 (homing dir invert mask:00000011)
$24=25.000 (homing feed, mm/min)
$25=750.000 (homing seek, mm/min)
$26=250 (homing debounce, msec)
$27=1.000 (homing pull-off, mm)
$30=255. (rpm max)
$31=0. (rpm min)
$32=1 (laser mode, bool)
$100=39.966 (x, step/mm)
$101=39.966 (y, step/mm)
$102=188.882 (z, step/mm)
$110=8000.000 (x max rate, mm/min)
$111=8000.000 (y max rate, mm/min)
$112=500.000 (z max rate, mm/min)
$120=500.000 (x accel, mm/sec^2)
$121=500.000 (y accel, mm/sec^2)
$122=50.000 (z accel, mm/sec^2)
$130=790.000 (x max travel, mm)
$131=790.000 (y max travel, mm)
$132=100.000 (z max travel, mm)
ok
GrblFeedbackMessage{message=’[G0 G54 G17 G21 G90 G94 M0 M5 M9 T0 F0. S0.]’, distanceMode=‘G90’, units=‘G21’}
ok

I know you’ve said you’ve tried everything, but just to ask a dumb question- have you tried adjusting the V-wheels on your X-carriage assembly?

I only ask because I was having the same problem. Circles would be close to nominal in the Y direction, but severely undersized in the X direction. I loosened up all X-axis V-wheels and started with setting the top ones FIRST (non-adjustable tension) then the bottoms. Snug, but not TOO snug.

If they’re too loose or too tight, you will get half-assed circles that don’t come out right. There is a sweet spot somewhere in there that you will have to find. I’ve also found that my circles vary depending on where they are cut on the machine. I JUST added stiffeners to the Y-rails so I’m interested to see if this helps out at all.

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