Finally getting the printer dialed in, well enough to get this gimble printed out ok. Still got some z ribbing artifacts, any idea what could be causing this?
Its a prusa i3, the 6mm threaded z axis rods are not perfectly straight, but they are at least unconstrained at the top. I have the esteps dialled in as low as I can, still get the occasional tiny gap on top surfaces so I don’t think I can dial it down anymore.
As you can see from the photos the ribs are not totally consistent, there’s some correlation to the threaded rod pitch but its more pronounced on some layers than others. Could it be extruder slipping or something?
Thoughts?
Is your filament spool pulling on the extruder? That can cause inconsistent layer height.
Another thing to look at is whether a given layer is “sticking out” on all sides or not (not would suggest loose x/y belts).
Well I have the filament on a lazy Susan. You could be right about it dragging on the extruder. I have printed out a spool holder to be mounted on the top of the frame but I think it needs support struts before I can use that.
Some of the lines seem to be offset to one side more than the other others go around all sides. It could just be that I have more cooling on one side than the other. I will double check my belts now.
As a test, you should be able to eliminate the filament pulling issue by unwinding manually
I would unconstrained the Z rod at the top so to let the wobble not transfer to the bot. When it is constrained and there is wobble in the Z rod the wobble gets transferred to the bot.
Yeah the Prusa i3 has the unconstrained z rod so that is not the problem. Tightening belts seems to have helped a little will reprint this piece tomorrow to confirm. Thanks guys!
Trying to think of to explain. I’ve read how on some software if you don’t calibrate it just right you can end up with the computer having non whole number steps on a stepper and will lead to effectively be a rounding error. So if the computer knows it takes 11.6 turns to reach the height it may take 12 instead.
Ah yeah that I think is when the pitch of your threaded rods does not calculate to whole multiples of your microstepping and extruder step values. Not the case here since I’m using .2mm layers on 4mm threaded rods with standard pitch and 16 microsteps which I think works out correct. Please someone correct me if I am wrong.
The best way to keep your spool from pulling on the extruder head (which would be my guess as to the cause) is to run the filament through a tube from there to some fixed point. This way any tension of resistance from the spool will not transmit force to the carriage. PTFE tube like a bowden extruder uses is best, but a slightly longer length of dirt-cheap HDPE tube that is a little wider than you would want for a bowden can work just as well, and will be at your local hardware store.
Thats a great idea, I have some tube left over from the smoldering pile of Makerbot I have in the corner. I’ll try that in the morning thanks @Whosa_whatsis !
For some of us, that print would be good enough if it is functional.
Oh its functional. But I am a bit of a perfectionist sometimes. And I have seen up close the lovely quality prints @Whosa_whatsis gets from his bukito so I have something to strive for! 
I had a similar problem and it was caused by the wobble of the platform. Check your bed whether it is rigid or not. If it is moving a little bit in either x or y directions that is the probable cause.
