X-Axis Drift Problem

[ploughex]

I have converted a Chinese round column mill/drill to CNC operation using NEMA 23 steppers (3.1NM torque). I have encountered a problem with the X ais which I would be appreciative if someone could point the way to a solution.
I tried milling a 75 mm square with rounded corners by successively increasing the depth of cut.
It soon became apparent that the X axis position crept nearly 1 mm in the +ve. direction with each successive cut, the size of the square remained reasonably constant. The Y axis also kept position ok.
This indicated to me that the travel in the negative direction was less than the positive direction.
I then may a large number of measurements to the x axis (cutting fresh air) using a range of feed speeds and accelerations these indicated that the positive travel was indeed greater than the negative travel. I also tried varying the number of micro steps from 2 to 125 without any improvement. Needless to say I eliminated any backlash as I reversed the travel by making a small initial movement in the direction of travel before zeroing. I also tightened and loosened the x axis jibs without it making much difference. I also tried using the y axis driver but with no improvement.
Below is a list of x-axis measured travels. The speed was 300mm per min. and acceleration of 50, the microsteps for this exercise was 10.

Mach 3 X reading mm +ve travel mm -ve travel mm
50.00 49.96 49.51
10.00 9.84 9.82
10.00 9.90 9.69
10.00 9.96 9.72
5.00 5.03 4.90
5.00 4.88 4.89
15.00 14.97 14.71
15.00 14.71 14.69
20.00 19.78 19.36
20.00 19.94 19.36
2.00 1.98 1.85

[Plan_B]

Hello, I am wondering if you solved this issue. I have a new build and am experiencing similar drifting.

[ploughex]

I found that the problem was purely a mechanical one. I replaced the stepper with a 4.0 NM torque motor and there was an improvement but still a little problem so I changed the motor pulley to the smallest possible giving a pulley ratio of 2.5/1. The set up now seams fairly stable and workable. I am still not quite sure why the problem should manifest itself in just one direction but as the saying goes "if it aint broke don't fix it"

[levon18lopez]

If your motor run in one direction correct your pin config and check your hardware