Hello all. New guy here. I have a question that I hope someone can help me with. I built my cnc a few weeks back and began running codes and trying to learn ALL there is to a cnc machine.

So I was getting an issue where I was losing steps on my z axis during milling. It was always the same direction, so the hunt began.

Im getting the proper steps on the motors, both direction; but played with the setting of the motors to see if that helped. Then I thought it may be the rails, which I wasn't to happy with and replaced them anyways. I then tried adjusting the belt tension, that didnt work. So I turned off the Y and Z axis and pulled the stepper for the x axis out and clamped it down to keep it from falling. I put tape on the shaft and marked the tape and the housing with a pen. I then ran a 1200 line code then hit back to zero to see if the marks line back up. It did not. I tried some tweaks in mach3 to see if that helped, I was still off of zero after running the code. I then reversed the x axis motor, ran the same code, hit go back to zero and BOOM, its back to zero. I feel like its something simple but I'm baffled. I think i came across a post of a person who had a something of the same thing happen but i can not find it again. What am I missing? Please, any help would be appreciated.

Thank you

Could be 2 things:
- too high acceleration for Z so steps are lost on upwards movement
- Wrong polarity of step pulses. If your drivers have common ground on step and direction inputs, active state of step and direction pulses should be HIGH. If you have common positive, active state of step and direction pulses should be LOW.

When you set the polarity correct, then, if motors are running in wrong direction, just swap two wires on appropriate motor driver.