X-Carve Z axis binds

When we are trying to zero our x carve the Z axis will not go down all the time. It sometimes tries to go up. Up works intermittently also and seems to bind.We have checked the connections and everything seems good. We have the NEMA 21 motors and a 500 mm deck. With a 611 router. When power is off we can easily move the router up or down.
Thanks for any input, Mr Yoast’s 8th Grade STEM class…

From what I’ve seen this is usually due to some loose wires (or strands of wires) causing either intermittent connection or intermittent shorts. Can you send some pictures of your set up?

When you assembled the X-carve, did you run the delrin nut up and down the ACME rod several times to loosen it up, prior to fully installing it into the z-axis?

If you did, I would take a look at adjust your x-axis potentiometer. The video for that is at this link:

Read my last post in this thread. I was having a similar issue and found it was due to a solder issue on the Z-axis driver.

So the STEM students are checking all the wires and connections. Nothing yet. We can shut of the controller box and easily turn the rod to raise and lower the Z axis. But once we power it up it is bound. When they try to move it down it will try to go up, then down. Up nothing at all. X and Y are just fine. I am going to try to work on it over the long weekend it they do not get it figured out. So any other ideas will be welcome if we do not find a wire. We will post up what we find. I would rather go fishing this weekend than troubleshoot the carver!
Thanks for the replies so far

Link to the shield schematic…

Straight forward to check J4 terminals 1-4 back to the driver at U3 pins 4, 11, 18 and 25. Just make sure to ohm out the top of the pin at the IC body (not at the trace/pad) to each terminal to see if there is continuity and good solder.

Under power, the steppers will hold so you have at least 1 side functional. It should be difficult to rotate. Further, a green LED (Z axis side) is tide to the motor pins. If your seeing green, it’s the opposite pair, and visa versa. No LED is most likely one of the pairs tide to the LED.