i3 Pro B Z Axis locking and buzzing towards the bottom

[tiggerbiggo]

Hi! Just got my i3 Pro B, have had a quite a lot of fun building it so far.

My problem is that once I have put everything together and was testing to see if the axes all work correctly, the Z axis immediately started grinding and buzzing when attempting to home. The X and Y axes work perfectly as far as i know, it's just the Z. There is also quite a bit of wobble. I have tried:

- Lubricating the z axis threaded rods with some light oil
- Re-building the Z axis, including attempting to re-align the spring couplings at the bottom to be perfectly straight
- Checking that the x axis rods are flat, and that the parts that attach the X to the Z axis are aligned

I'm really confused as to why this is happening. Does anyone have any tips?

Thanks :)

[William]

Have you tried to swap the A4988 of X axis and Z axis?
I think by this way you can know the issue root

[Yohan1502]

Hi tiggerbiggo,

I had the exact same problem than you last week just after building my printer. The Z-axis is more complex than the two others because it has 2 motors and thus need more precise adjustments to work fine.

Here is what I did to correct it :

- First, try to make the holes bigger in the top acrylic part where the rods should turn in. In my case, they were too small and prevented the rods to turn easily. I used the tool given in the printer toolkit and it just a bit of time.

- Then, I diassembled the 2 rods and put them back on in the opposite way (just in case) meaning top becomes bottom and vice-versa

- Finally I assembled correctly the coupling, the motor and the rods together. The online documentation AND the youtube videos are really missing accurate information there. You shouldnt fix the coupling with random positions, but with 5mm offsets. Follow this video : https://www.youtube.com/watch?v=T9vI6DqAcmo&t=335s

I also lubricated the rods and now the Z-axis works like a charm ^^

Hope this helps,

[BrokeIt]

Hi, Also just finished building my i3 Pro B and had, perhaps, a similar problem. I fixed it this way:
- removed all X axis gear so Z axis only had two motors, couplers, threaded rod and 8mm shafts with top mounts installed. Ran the Z axis and made sure the motors were turning. Had to adjust the couplings between threaded rod and motors to get rid of wobble and make sure everything was running smoothly. My coupling have are free to flex as this seemed to suit my build. They seem to run mostly without wobble however. My top frame mounts didn't need any filing or adjusting.
- Added RHS X axis steel bracket. I found the hole for the brass nut for the threaded screw needed some filing. Worked on the bracket until it would go up and down smoothly. Also turned brass nuts upside down as it seemed to help. Added a little machine oil but didn't want to get any on the frame. Took awhile to get it running to my satisfaction. For me the bracket really had to sit naturally without any force at all. I could make it fit without filing but it would just jam. I used a round file for the filing.
- Added LHS X axis steel bracket and repeated the same exercise. I left off the X axis motor to make it easier. Again kept adjusting with some filing of the shaft until it would go up and down easily. These brackets seem a little fussy to me and the brass nut didn't want to sit on my machine in just the right position. Took some effort to make it all fit just right.
- Added X axis motor and X axis without extruder. For me getting the X axis rods exactly horizontal is key. If it is a little bit out then the machine will not be happy at all. I found the holes in the RHS and LHS steel brackets (parts M1 and M2 on my parts list) for the X axis smooth rod needed a touch of filing to allow the rods to go through. Again fitted, levelled, raised and lowered Z axis lots of times until it was all good. I used the round file that came with the kit for this.
- This all took a little while with a few iterations of assemble and disassemble until I felt it was good. I had the machined powered up during this and used the LCD panel to instruct the motors to run up and down.
- The z axis was the hardest part of the machine assembly for me.

This is my machine, not sure if parts on other machines have the same issues. I have now printed 3 items and I am very happy with the outcome so far. I am still using up the sample filament that was included with the kit before opening a new reel.

Good luck!

[Soadyheid]

Ensure that the height of the X_Axis is the same at both sides, do this by measuring the distance between the Z-Axis mounting plates to the Z_Axis M8 screwed rod nut at both sides of the printer. If the heights are different, The axis will bind and the motors stall. With the printer switched off, manually adjust one of the screws so the height at the left and right hand side of the printer match. Power up and try homing the axies.

Play Bonny!

Soadyheid