Z Binding

I got to the point in my build where the gantry is installed, everything is square, and secure. I wired everything up and checked for stepper rotation but I had a problem with the Z axis. The stepper couldn’t turn the threaded rod. Powered off it’s very difficult to rotate by hand. I loosen the coupler and raised the Z-axis. The stepper and the rod both rotated easily when disconnected. Reading through the forums I saw repeated mentions of lack of lubrication, so I applied a lot of white lithium and ran the rod through the middle assembly with a drill motor (after I checked it for straightness). During re-assembly I noticed the rod didn’t line up perfectly with the bearing in the z-axis, off maybe 1/8-1/4 inch, which resulted in a side load that seems to be causing the binding.
Although everything checked square I played around with the Tension C bolts (and applied a heavier lube) with no improvement. Before I pull the Z and middle assembly back off and just disassemble/reassemble is there anything else I should try. I noticed in other threads that there were a couple questions about the position of the nut and spacer in the middle assembly; I have the nut in the top position.
I got everything from Vicious1 - Thanks in advance for the help.

Are both the spacer holes properly aligned? I have had it drag on the bottom one before. Check for relative alignment on these they can be shifted around a bit.

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I took a look and it looked aligned but it was too tight to move at all. I took a half turn off the Tension B bolt - just enough to wiggle it a bit and I guess a wiggle was all it needed. Rotates fine - like butter. Thanks for the advice.

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Yeah the center is a bit fiddly but once you dial it in it usually stays put. I have been sketching new designs since I released that one…I never stop trying to improve.

I had this same issue and was able to resolve it by removing the Z assembly from the center section and running a drill down through all the parts to create more lead screw clearance. It must have been catching somewhere through the travel.

Old thread, I know, but just in case someone finds themselves here trouble shooting…