problem with vibration affecting layers of print?

[bsaygan 1]

Hi,

 

I've been having this sort of annoying thing happen with my prints.  I wasn't sure if it was a sudden thing, or if it's been happening always or gradually happening (I think perhaps the last).  

 

I end up with slight gaps in middle layers of a print, particularly on these diaganal lines, it doesnt happen on purely horizontal or vertical paths.  At first I thought it was an underextrusion problem or maybe leveling problem, but I've done things like clean the core, the feeders, tubes, as well as increase heat settings for the filament, and realizing that it only happened during these diagonal lines, I started watching the print during this time.  I noticed that the gaps sort of coincide with a rubbing sort of sound?  Similarly, I'm not sure if the rubbing sound was always there, or if it's gotten worse over time.

 

Anyway, my question is two fold:

1) Is there any validity in my hypothesis that something about that noise/vibration is causing these gaps?

2) if not, any other theories?

 

Thanks,

Bobby

[Smithy 1,146]

On your photos it looks like this so it would be the first layer after the infill.  In this case it would be normal that you have holes in this layer. The filament is held by the infill, but you get a gapless surface only after 2-3 layers.

 

Or does the problem also occur later, that is not so obvious?

 

I don't think vibrations do that. But I can't judge the noises like that, maybe you can make a video where you can hear it?

[geert_2 558]

I don't see how vibrations could cause this? Unless there would be some mechanical defect, such as motor, gears or belts being blocked or so dirty that it hinders their free movement. This could cause abnormal sounds indeed. But a sort of "robotic singing sound" in diagonal lines is normal.

 

On the condition that these are not the very first layers on top of empty gaps (above infill or hollows), as Smithy says, I would guess: underextrusion, too low temperature or too high speed, not 100% infill selected (e.g. 90%), too much friction in the filament or feeding traject, dirty nozzle hindering the flow, worn-out teflon coupler (UM2), or less likely and if the lines are in pairs: too much play in the rubber belts?

 

What if you do a small test cube at low speed, at 100% infill?

 

[bsaygan 1]

Yeah, perhaps the vibrations not part of it.  I thought the belt rubbing might have been some misalignment, but I readjusted all those things last night.  So I do get slightly better print quality overall, but still the same issues with diagonal gaps.  It is not just the first few layers over infill, but it's also not 100% infill, although I've tried settings like a thicker top layer.  I'll try the cube.

 

I thought it was underextrusion as well, but the first layer does print very well (although I guess the settings for first layer are usually a higher temp and slower speed by default).  I did do things like try different brands of filament, clean the extruder and bowden tubes (although perhaps I could replace them) and try different cores (I use my second AA core less so than the BB so wondered if a "newer" core would help).  I also get these gaps regardless of "quality"/layer height settings.

 

I'll try the solid cube, and if it still shows the gaps, try reprinting it in incrementally higher temps or slower speeds.  There are no other appearances of underextrusion anywhere else on the print (side walls), so it's just a bit perplexing.  The solid cube should be an interesting test.

 

I'll let you guys know, and thanks for the input!

 

Bobby

 

 

 

 

[bsaygan 1]

solid cubes still showed the gaps with 100% infill.  The increased temperature was a little bit of a mixed bag.  It often helped a little more at the sacrifice of losing some dimensional accuracy in corners especially (globs).  

 

I think probably speed more of a culprit than heat.  I do notice on some lines that are layed down, the bead goes from a pretty straight smooth bead to having a little wiggle/waviness on the edge.  Wonder if this is an indicator of anything else?

 

ultimately, this is not a huge deal, mostly cosmetic, but I can't remember it ever being quite like this before.

 

[bsaygan 1]

So just to update:

 

I ended up doing all the maintenance again, but the two biggest things is I just full on replaced the bowden tubes and collet clips, and really took apart the extruders including the nylon gear wheel and knurled wheel.

 

It helped immensely.  There's still like a touch of the under extrusion, but it's significantly better.  THe one thing I noticed about the extruder wheel (the one having the issue), is that the bearing might be going bad?  I took the nylon wheel off leaving the knurled wheel/axle in that bearing, cleaned it off as there was some ground filament behind that nylon gear, but if I compare that bearing to the second extruder bearing, it doesn't roll as smoothly.  I wonder if that is contributing to that like 1% under extrusion I still have.  I may just have to replace that bearing on that extruder.  

 

I'm not sure how much having brand new bowden tubes helped, as it doesn't seem like that long ago that I replaced them, but I think it helped quite a bit too.  

 

I finished up with the rest of the maintenance of tightening the axles and belts, etc. and my print is looking good so far.  I'll know more when it finishes tomorrow morning, but the progress is looking good.

 

Anyway, just wanted to update.

[bsaygan 1]

Eh, I spoke too soon.  Later layers still showed the under extrusion or gappy layers.

[bsaygan 1]

Ok, another symptom to diagnose in this whole thing...

 

Here is a view of part of the infill print.  You can see some of the lines end up squiggly (the squigglyness is why I asked about "vibrations" before).  Are squiglies a result of underextrusion?  I feel like this is a related symptom of my overall print issue.  I also noticed that if I did print a square/cube - the left side has the worst finish.  So the Y direction on the leftmost side.  

 

Not sure what to make of all these pieces of information.

 

Bobby

 

[bsaygan 1]

Final (?) update - more or less solved all my issues:

 

TLDR; replaced feeder assembly and linear bearings to fix my issues.

 

1)  "Vibrations"/Wiggly lines:  I replaced the linear bearings on the X/Y axle rods in the print head.  The bearings were catching just slightly, more so at higher speeds than lower speeds.  I'm going to guess I've been over-lubricating on the monthly maintenance.  There was actually a buildup of what looked like sort of burnt oil, which probably led to those bearings going bad (sooner).  My infill pattern lines are now straight as can be, as well as the surface on the outer walls of my print.

 

2) Under-extrusion:  Mostly fixed, but bought a new feeder assembly so I'm going to guess once that comes in all will be solved.  Essentially two parts of my feeder were causing some additional friction, and sometimes if unlucky, caused the filament to lock up and grind.  First - the bearings that bookend the knurled wheel/large gear, were catching just ever so slightly.  My guess is that it would end up skipping a tiny bit during retractions as I noticed that the longer the print went on, the worse the print got, so the cumulation of skips over the duration of the print just made it worse.  The bigger culprit in the feeder - is the tension arm that has the wheel that presses the filament against the knurled wheel was off center(?) or mis-seated.  I think it would catch the filament at sometimes a weird angle and just wouldn't turn/move causing the filament to grind.  After oiling the bearings and wiggling the wheel in that tension arm to center it, my prints are now close to perfect, but I notice over a few prints, they start to degrade again, so that tension arm or the bearings may keep catching or something -- thus my theory that a new feeder assembly will fix this issue.  I came to the broader conclusion printing the same filament, in the same core, but on the different feeders.  The feeders were the only variable I am aware of, and one print came out great whereas the other came with symptoms of underextrusion.  Temperature settings/speed settings helped but seemed like an inconsistent bandaid fix that caused other issues like globbing.  

 

Anyway, just wanted to tie this up in case anyone in the future on this forum has a similar issue to me.

 

Bobby