Hi Guys,

This is my first post and would like to know if anyone can assist with my issue regarding pocket cuts.

I've got a retro fitted BF20 Clone CNC (like a Grizzly G0704) and for some reason my x-axis shifts slightly every time it plunges which gives me a stepping effect on right hand walls. It only occurs with pocket cuts. Pocket cuts that are 3mm deep will shift about 0.5mm to the left. I'm doing climbs cuts but the stepping effect will swop to the left side walls if I do conventional cuts (I don't do conventional cuts but wanted to see what happens).

This is not the best photo but you can see in the top right radius that it has steps which smooths out as it goes to the left.


I've checked the following:
- Gibs are good
- Leadscrew backlash is 0.12mm (x-axis) which I think is acceptable for a retro fit.
- Spindle head is perpendicular with the bed.
- Pulley set screws are tight.
- Belts are tight.
- Belts aren't rubbing against anything.
- Machine vice has no play.

I did add backlash compensation in the Centroid Acorn Setup Wizard which does solve the problem but only for a few cuts and then it gives me the stepping effect again. I did notice ,while measuring the backlash, that the backlash value will be inconsistent by 0.01mm-0.02mm. What I mean is that the backlash value will be slightly different after I do a cut so it's impossible for me to enter a spot on value. The y-axis does the same but I don't get the stepping effect in this direction.

Has anyone had this problem before?

Machine Specs:
Retro Fitted CNC BF20 Clone
- Centroid Acorn Controller
- Wantai DQ542MA Driver (Nema 23)
- Wantai DQ860MA Driver (Nema 34)
- Nema 23 X and Y Axis
- Nema 34 Z Axis
- GT2 Belts and Pulleys connected to lead screws and stepper motors.