z-axis binding up

General LulzBot Mini
1

Hello. i am having issues with the z-axis movement on my mini.

A while back i started a print and noted that the z-axis was all off kilter and shut down the machine immidiatly. After some more trouble shooting today i have sorted out that the fast homing command from the lowest position causes the electronic’s side z-axis motor to bind and the other runs freely.

what i have established so far:
*seems to only happen from the lower end of the z-axis when home is hit on the cura control
*1 and 10 +/1 increments seem to work fine and are repeatable at the lower point
*coupling was verified to be tight on both lead screws
*generally the lead screws seem consistant with the frame
*zmin limit switch serves no function on the blue black wire as i thought it was failed and causing the jam up

Questions:
*is it possible to force the printer to not use the rapid return movements? perhaps that can rectify the issue
*does it sound consistant with alignment or oiling or binding issues?

  • which of the brackets have some play to soak up the alignment problems?
    *anything else sound fishy, or could potentially be causing binding issues? weak motor?
    *can i connect the zmin to anything i pulled it from the header above the 6 limit switch headers but can’t recall what pins it was attached to nor anywhere on the manuali that it can be installed to.

anyway thanks for the advice, would be great to use this again as its been months of neglect now :frowning:


Edit:

it appears that oiling the heck out of the lead screw helped but its still working hard a few points along the way. My thoughts now are that the lead nut and screw might have galled up over time originally creating a rough spot. anyway will keep tabs on its operation but i did get it to function again which is a plus and it seems to be able to print.

2

Hello Kevin,
It sounds like you have some binding in the Z.
First you will need to level the X gantry so that the smooth rod is level with the top of the frame. You can turn the silver coupler that attaches the Z axis motor to the lead screw to make the measurement on the left side to be equal to the right side. This way the X gantry does not bind on the lead screws when you are moving in the Z.
Then locate the X axis motor and X axis idler (opposite side from the motor), they will have three 4mm Allen screws in the top of each of them. This is what holds the whole X carriage with the tool head on to the threaded rods. Please loosen all 6 of the Allen screws (not a lot) and then with Cura move your printer to the home location. Then select motors off in Cura and move your tool head to the middle of the printer. Then move the X carriage assembly down 150mm (by selecting on the down arrow in the 10 position 15 times) please do this 2 times and then move the whole assembly down 75mm to the middle and re-tighten (finger tight) the Allen screws. Then try printing another print. This may take care of the issue, by settling the X carriage in the proper location. It may simply be bound up between the threaded rods.
This should allow the X gantry to move without resistance on the lead screws.
If it does well but then comes out of level again, then you may have an issue with the Z stepper diver getting too hot on the RAMBo.

I hope this will help.

3

thanks so much David for the detailed guide, very much appreciate your time! I am confident that will get me back into alignment and i had not considered adjusting the carriage itself. Looking forward to being back in business with this sweet little printer, you guys did great on the design!