The grbl parameters from the $$ command are in mm. For the benefit of upper level software you can have grbl send its values to that software (ie Easel, UGS, etc.) in inches by changing $13=1.
I just solved a Z-Axis issues and wanted to share in case it helps someone else. I was noticing that the depth cut was deeper on the right side and more shallow as it moved left. I triple checked the level of all parts and the construction and everything seemed fine. Finally, I fixed the problem by adjusting the X-Axis gantry eccentric nuts. By tightening the wheels, I was able to get a consistent depth cut across the whole X-Axis. Not an obvious fix, so I wanted to share.
I’m having the same issue and I noticed last night that 2 of my centric were pretty lose. I tighten then up but I haven’t use the machine yet. Hopefully that was the problem. Thanks for sharing!
I am also having the same issue, found this blog article about the same problem. Going to give it a try when I have a free moment.
I have checked everything above and still have this issue. I am going to change the motors z will go to y to see if the z motor is missing a step.