Strange Printing Defect! Please Help,
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@syko_symatic said in Strange Printing Defect! Please Help,:
M566 X400 Y400 Z20 E30 ; Set maximum instantaneous speed changes (mm/min)
; Pressure Advance
;M572 D0 S0.7Very low extruder jerk and very high pressure advance can lead to some odd side effects. I'm not super familiar with the nimble, but I realize they recommend low jerk due to the worm gear drive?
If you're running firmware 2.03 You could try enabling the new jerk policy setting with M566 P1 and see if it makes a difference. It's a long shot, but worth a try.
Looking at the pictures though it definitely seems like some sort of extruder eccentricity.
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@phaedrux extruder eccentricity? Never heard that term before? Could you give me a quick run down on it?
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@syko_symatic A gear or something in the path that transfers the rotation of the motor to the gear that pushes the filament is out of true. So instead of consistent motion there is pulsing, or vibration, or extra drag/friction. Some mechanical action causing the pattern you see.
Have you tried printing larger objects yet? Circles? Diagonals?
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@phaedrux diagonals, yes, circles no.
With the nimble what could actually cause that eccentricity?
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I imagine that would be the tolerance stacking they mentioned in that copy and paste above.
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Doesn't look like an eccentric gear or loose bearings/case/hob shaft due to the tight spacing. I had an undersized hobb shaft and the effect was more spread out. Looks more to me like cable/stepper side problem. What is your minimum cable radius? Can you detect any slapping of the cable against the sheath? Re lube, I use 20K diff lube and it works fine. Others I have heard using 10K to 100K.
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Oh, another thing to check is that the end of the cable is all the way down inside the worm gear.
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@phaedrux said in Strange Printing Defect! Please Help,:
Very low extruder jerk and very high pressure advance can lead to some odd side effects. I'm not super familiar with the nimble, but I realize they recommend low jerk due to the worm gear drive?
Honestly the low jerk / acceleration was the biggest hurdle for me. I almost gave up but I hunted for low inertia / fast steppers. I found that 3.6 degree parallel disc magnet steppers from Portescap (P430 258 005 01 with the coils wired parallel) allow for some serious extruder acceleration and jerk. As a test I have tried up to 100mm/s retraction without any problem even with the 30 to 1 gearing. Be sitting down if you look that stepper up though. Fortunately I got them used for less than 10% new price.
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Spoke quickly to Brian from Zesty Tech over email. He suggested a few things which have improved the quality but still not quite there 100%. May be having a call with him tomorrow.
One thing I have mentioned to him though, the worm gear seems much looser in the bearing on one end, I am not sure if this is intentional but may be an issue?
If anyone can suggest anything to improve this result further I am all ears....
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@damianm reducing the extruder acceleration to 1000 did wonders to be honest. I will have to check a few other slicer settings and esteps to see if I can improve on the finish I am currently getting.
It's good but now as good as I got from it on my previous printer.
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@syko_symatic That looks like it might be related to the loose fit at one end of the worm to me. It is similar to what I got when a bearing was getting worn out.
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Jammed some paper in between the looser end on the worm gear and the bearing and it seems to have helped. I have ordered a new nimble (as they have a slightly improved version now) so maybe I need to get a replacement worm gear? I will have to measure it first and see if it was manufactured incorrectly.
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@Syko_Symatic Thank You!
