Anyone got a clue as to why I would suddenly develop Z ribbing that

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discussion
(Ryan Hescock (Stanos)) #1

Anyone got a clue as to why I would suddenly develop Z ribbing that looks like a rounding error. I have double checked the threads and pitch is 1.25, replaced the stepper motor and driver, filament is consistent (from Ultimachine), and the results are the same with two builds of slic3r and whether or not I’m using volumetric extrusion. The ribbing does not match my thread pitch but the pattern is evenly spaced which is why I think it looks like rounding error.

Prusa V2
ABS @ 241c
Speeds are all 40mm/s
No backlash and not too tight.
Verified threaded rods are not constrained and not pulling against the smooth rods.

(Matt Miller) #2

What layer height?

(Ryan Hescock (Stanos)) #3

.2mm

(Matt Miller) #4

steps/mm on Z?

what microstep rate?

(Ryan Hescock (Stanos)) #5

2560 with 1/16 micro stepping. My actual height is within .01 of model height as reported in slic3r.

(Ryan Hescock (Stanos)) #6

I’m at work now but I’m going to run some tests with other filaments and an older build of marlin when I get home.

I am having a hard time attributing this to mechanical since the z accuracy is perfect using expected microstep values.

(Whosawhatsis) #7

The periodicity is pretty consistent, but not perfectly so. At this point, my money’s on spool pulling.

(Ryan Hescock (Stanos)) #8

Yup I thought that too but the print you are looking at was done with a 3 foot cut of filament.

(Ryan Hescock (Stanos)) #9

I’m thinking maybe I’ll just get some M6 rods and modify it to use those. I’f anything it will make the problem less noticeable.

(Matt Miller) #10

If you do move to M6, just print an X/Z decoupler and install (2) PTFE washers between the decoupler and the X-end so it can move.

You’d have to modify these for M6: http://www.thingiverse.com/thing:20147
PTFE washers: http://www.mcmaster.com/#95630a219/=tlcydw

(Ryan Hescock (Stanos)) #11

Picked up some new M8 and some M6 from the local industrial supply store. Almost got lost the place is fricken amazing. I’ll swap the M8 first as soon as I get home to make sure it wasn’t just crappy rod. Its possible the rod pitch is inconsistent but averages out to be correct.

(Joseph Chiu) #12

Do other prints exhibit ribbing at the same elevations?

(Ryan Hescock (Stanos)) #13

@Joseph_Chiu Yes, I chose this particular print to verify it was ribbing and not wobble.

Update, here’s what I have done so far today:
Replaced M8 rods with good quality ones from local supply - No change

Reinstalled old build of Marlin - No change

Resliced with stable build of Slic3r on old Marlin build - No change

Printed another one with .3mm layers - Same effect just spaced out further but happening with the same periodicity of about 12 layers.

That right there tells me this is definitely a rounding error, but I can’t figure out for the life of me how it could just all of a sudden show up. My only thought is that it was there before, but now that I have the flow dialed in so well and everything else tuned in perfect, that this is now more visible.

(Ryan Hescock (Stanos)) #14

Here is my Configuration.h if anyone cares to take a look.

(Matt Miller) #15

Try full-step on Z?

(Ryan Hescock (Stanos)) #16

@Matt_Miller Just tried it and still had the same patterns. Gonna put in the M6 rods tomorrow with some temp modifications and see what I get. I may also try another firmware to rule out any compiling errors and the such. Figure if I get the same pattern with different firmware and slicer then it has to be hardware or electronics.

(Whosawhatsis) #17

or mechanics… missed the word “hardware”. I really think that’s where the issue is.

(Whosawhatsis) #18

Oh, btw, if you’re printing on a heated bed, you should try one with PLA on blue tape to rule out the platform expanding and contracting as the heater kicks on and off.

(Mike Downey) #19

While the previous comments are probably on the right track, dont rule out temperature fluctuations. Poorly tuned PID values can cause regular temperature swings which can manifest themselves in the print as regular occurring layers. Keep an eye on the temperature graph to make sure it is not oscillating.

(Will Dent) #20

If all else fails maybe try the cura slicer, It seems like every time something goes screwy on my printer it’s a slicer problem. My printer will be running fine then the next time I use it, it’s like wth is wrong with this thing. Next thing you know you spent 3 hours trying to figure out if something went wrong with the mechanical parts only to figure out it was the slicer being a jerk. So thats some food for thought anyway, best of luck.