strange z axis anomalies, tried everything, pulling my hair out!

Hello to this always incredible forum!

I am writing this post to ask for help on my heavily modified robo 3d. It was the kickstarter edition, and as such, had a slew of problems which I supposedly fixed...

Switched out the hotend for an e3d lite6, switched to dual high cfm filament fans, switched out the 5/16 threaded rod for some 8mm 1.25 threaded rod, switched out the hobbed bolt for a better one, printed new z rod holders, top and bottom, converted to an 8mm smooth rod setup instead of the horrid drawer guides, switched out my x and y axis motors for .9 degree sanyo steppers with integrated dampers, and switched out the stepper drivers for drv8225 drivers. In addition, I uploaded the latest version of marlin.

I am using Simplify3d to slice.

The problem I am having is strange anomalies on my z axis. It almost appears that some layers are squishing more than others, which i attributed to uneven lifting of the z axis during printing. However, I have tried what feels like everything to get this working, and it still won't cooperate.

Here are my possible solutions thus far (some of which have helped, but not alleviated the problem entirely)

- Tightened the x and y axis drive belts
- Adjusted current on all motors to their absolute peak without the driver cutting out
- Changed out LM8uu bearings in the x-ends to known good ones
- Switched out the z rods with known good ones to eliminate possible binding issues
- significantly lowered acceleration and jerk in Marlin
- made sure bed was staying stable throughout the entire print
- lowered extrusion multiplier


I'm pretty well out of ideas at this point. Please help!

Attached is a picture of my latest 20mm cal cube, which is my best thus far.

Have you tried reading through this thread?
[community.robo3d.com]

I have, I am going to try and really force my z lead screws into the couplers. I have some new plum couplers on order from china, that I hope may help some more

I switched to 5mm rod on my robo and it totally got rid of my ribbing. I replaced the coupler with some vinyl tube and altogether it cost like $5. There a thread over in the mods and upgrades sections at the robo forum with some more info.

Awesome! I actually just ordered some 5mm threaded rod for that very purpose. My mendel has 5mm and has the best lines I've ever seen.

I have noticed on my rods that the surface quality also matters.
When they were new I had a lot of binding problems, one side lifted a bit less or literally jumped a bit while the rod as turning.
Used a drill at low speed with the rod in the chuck and these green pot cleaning pads to run it up and down the rod while spinning.
During the irst few minutes I had a green rod due to the fabic being pulled out of the pad, a few minutes the rod was smooth enough to not pull a paper towel into pieces.
Wih a bit of white lithium grease (had nothing else at hand) all runs very smooth now.

I know this thread is a month old, but just wanted to point out that there is a good article on our site regarding z-ribbing issues on the Robo3D, and how to possibly correct them. It was written by someone from the Robo3D forum, and just wanted to share it here with anyone who may be having the same issues currently. Check it out at:

www.american3ders.com

Go to the "Knowledgebase" section and you'll see it there.