Z-axis binding on one motor  

Z-axis binding on one motor

Hi all,

I just assembled my second MK3 (v3.05) and ran into a unique issue that might be applicable to others. I did a cursory search, and didn't find anything prior, so mine might be a one-off, but it's worth recording for posterity.

TLDR; I found an alum burr inside of the threads in a trapezoidal nut on one of my z-axis lead screws causing the screw to bind when powered to turn in the assembly. I took a knife to the burr and cleared the thread so it works now, but stripped away some of the coating in the process. Do I need to worry about ~1mm of coating inside one of the threads being missing and request a replacement part, or should I just let it ride and assume that I've fixed my problem?

Problem:

One of my Z-axis threaded rods was sticking when provided power, causing my entire x-axis assembly to skew in place while the other lead screw was turning freely.

After disassembling, the following symptoms presented:

1. Axis motor lead screw moved freely on its own, only bound up when in assembly
2. Trapezoidal Nut on lead screw was moving, but required more pressure than opposite Z-axis motor assembly
3. Swapping Trapezoidal nuts on lead screws moved the difficulty of threading to the new lead screw, pinpointing the cause to the nut itself.

After inspecting the nut, the cause was determined to be that one of the threads caved in at the chamfered entrance on the flange side, resulting in a slight layer of material buildup that still allowed for it to thread on without binding, but making it difficult to turn along the screw when assembled, to the point that the motor wouldn't power through it, and seemed like the motor itself was binding.

This was difficult to see right away due to the fact that the black coating (anodization?) was also on the debris inside the thread.

Solution:

Using a razor knife, I cleared the debris inside the thread, and the nut was free to move along the lead screw without hindrance.

Possible issues: (Input requested)

If that coating was an anodization for long term wear protection, then I've effectively stripped it from a small portion of the threading. I don't think this is an issue to be concerned over, as the metal for the trapezoidal nut is aluminum, and the lead screws are steel, so any protruding alum edge in the thread will wear to be even with the other anodized coating, but I figured I'd get input from others as to whether or not I should ask for a replacement part, because I'm lazy, and don't want to disassemble and reassemble it again if I don't have to.

Thanks!