Root3 CNC built and working....kinda...

So, got it built, everything connected using Mach3...slaved A to the Y axis. X on gantry is silky smooth, and one direction on y, towards the side that the motor is on....but the other way, in the direction that the pulley that connects to the other side of the gantry (Root3 calls this the motion link), it is very jerky and struggling....and eventually, it gives up and then the jog in both positive and negative jog the gantry in the direction of the motor side....

I don't think it's mechanical...the belts are pretty tight (is there such a thing as too tight?). Without power, there is equal resistance pushing the gantry manually in either direction. If I restart Mach3, it resets and will try again, until the Y jog directions both go only toward the motor side (call that the smooth direction)....

I will say that the motors and drivers are Aliexpress specials, so not highest quality (wanted to learn before spending too much)...I am using the same RNR board on the buildyourcnc.com website and videos, and it seems to be able to power much larger machines.

Any and all help appreciated.

one direction on y, towards the side that the motor is on....but the other way, in the direction that the pulley that connects to the other side of the gantry (Root3 calls this the motion link), it is very jerky and struggling....and eventually, it gives up
So, the Y axis moves fine? This could be due to a faulty Dir signal on the Y axis.

Try using Mach3 to flip the Dir signal to reverse the Y axis directions. See what happens.

Cheers
Roger

Since writing my original post, I rewired the two Y axis motors to use the same signal wires from the motion card to the two different drivers, reversing the polarity of the connections on one motor. This solved the issue instantly. I have come across many posts that says the slaving function of Mach3 is not entirely predictable or reliable. The only negative of this is I cannot set up the two motors to autohome separately to ensure squaring of the gantry, I am unsure if there is anyway to do this without defining each motor as separate axis (ie Y and A).