I tried figure out why my CNC mill not so accurate.
I made axis calibration in area of 150mm and it seems ok, difference about 0,05mm, tolerance is enought for my needs on both X and Y axis
I have X axis with slave A axis
And Y axis driven by one motor.
Lead screw driven by timing pulley and belt

X-axis have long belts and I put backslash compensation to 0,1mm
Y-axis dont have any noticable backslash and runs realy smooth with short belts etc, better than X axis but...
Y axis is inacurate when try make details

I tried to make Rectangle and Circle with different diameters from 10mm - 40mm:
By X axis measures are correct +/- 0,05mm through all circle and rectangle size
But on Y-axis Measures are bigger by 0,2mm trough all circle and rectangle size, not realy mater do you make 10mm rectangle one side is ~10.2mm or 40mm size is ~40.2mm. smaller details looks more worse

I dont know whats wrong, i tried make 3 times Axis calibration but result are similar.
I want notice that Y axis dont have any backslash compenstation!
Can anyone help where to look and what to do.

My system is Mach3 with GeckoDrive G540, 4xXylotex 269 oz.in Steppers
I dont see anything wrong with G-code too
G-code is:
G21 G90 G64 G40
G0 Z1.5
T1 M6
G17
M3 S0
G0 X21.5875 Y-8.4125
G1 F200.0 Z-1.0
G1 F500.0 X38.4125
G1 Y8.4125
G1 X21.5875
G1 Y-8.4125
G0 Z1.5
G0 X7.8384 Y-3.0546
G1 F200.0 Z-1.0
G3 F500.0 X8.4125 Y0.0 I-7.8384 J3.0546
G3 X-4.2063 Y7.2854 I-8.4125 J0.0
G3 Y-7.2854 I4.2063 J-7.2854
G3 X7.8384 Y-3.0546 I4.2063 J7.2854
G0 Z1.5
M5
M30

Sorry for my BAD english