Solved Inconsistencies in Z axis - Z lift issues during retractions in print

All,

I've been a Robo 3D user for a while now - we bought a beta printer for my lab a couple of years ago, and I have recently purchased a newer R1 for my own personal use. I love this printer! As usual, I've been able to produce exceptional prints, and the machine has already run through close to 3 spools of filament since I received it last month. However, recently (in the last week or two) I've started noticing significant, random bands of poor adhesion that are occurring on the Z axis. I can *definitely* correlate this to retraction z lifts (0.5mm) - meaning that when the printer retracts and lifts, it doesn't *always* return back to its starting height.

This is evidenced by a seemingly very random positioning of the loose adhesion points. The picture below underscores exactly what's happening: Picture on the left: lifts disabled, print looks perfect. Cube on the right, lifts are taking place, and while many layers look good, others don't seem to adhere well.




Note that both cubes were printed on or near the same day! The second picture shows the adhesion issues better.

Things I've tried:

• Lubricate all axes, carriers, and threads
• Different spools of PLA
• increasing temperature by 4 °C (was printing at 210, tried 214).
• Tightening the couplers - they seemed extremely tight
• Making sure that the wiring harnesses are free to move

Note also that no two cubes print the same way, meaning that this is a seemingly random issue.

Any advice? At some point, it's going to have to lift, I'd appreciate any help. Thanks!

 

I believe I have found the issue - the right coupler, though extremely tight, doesn't seem to be holding the screw at all. I screwed the long screw clockwise into the coupler to stop motion - I hope that's the solution! I think oil may have gotten into it. Any ideas on how to clean or fix it?

 

Thanks Mark! I screwed it in as hard as I could, and last night's print was was flawless! Still felt a little loose again this morning, so I will try loctite. Any reason I should disassemble it and do something else? It seems to work just about perfectly, despite a little wobble in the rods, when it's screwed in tightly - no issues at all.

 

Understood. I took the lead screw out completely, used some degreaser on it, the plastic compression sleeve, and the coupler (piecleaners did the trick there.) After I put everything back in (I kept the plastic sleeve a bit higher to prevent any oil from seeping in later on, just in case), and some loctite. Flawless prints again! I have very minimal if any Z ribbing, so for now, I guess I'll stick to the couplers the way they are. Thanks!