SOLVED Stuttering extrusion at the start of each new layer

[kulfuerst 6]

Hello everyone,

 

I am having trouble with some strange underextrusion. In some prints, maybe 1 out of 10 and in only certain parts, the PLA is extruded in little pulses that increase in frequency untill they turn into a smooth line. This always happens at the beginning of a new layer, after z-hop and retraction. Due to this the print is massively weakened at these parts and shows striations on the surface. I managed to capture this on video and also have a picture of it, but I have no idea what could be causing this, especially because it only shows up every now and then. I would be very grateful for tips and help regarding the issue. Here is the link to the video: https://photos.app.goo.gl/G3TLKveMsLNRQmgv7

Thank you very much!

 

[edit by gr5: note solution was found by the original poster - see 2 message far below by author with "heart"/like icon]

[kmanstudios 1,120]

Printer?

[kulfuerst 6]

It's an Anycubic i3 Mega. Sorry for not clarifying that right away.

[kmanstudios 1,120]

No worries. It is just helpful for the people who have experience on certain printers to be able to give concise information.

[kulfuerst 6]

Another example, this time fortunately only in the support, the print itself shows no sign of it this time. The cause for both is probably the same tho, so I'd like to figure it out. I am using Cura 3.6.0 as a slicer btw.

[Smithy 1,144]

Normally Infill is printed faster than walls, so I guess your printer has problems with extruding the needed amount of filament which is needed. So try to print slower, set the speed for infill, walls, etc. all to the same slow value and set it slow like 30mm/sec and check if it is better.

[kulfuerst 6]

7 minutes ago, Smithy said:

Normally Infill is printed faster than walls, so I guess your printer has problems with extruding the needed amount of filament which is needed. So try to print slower, set the speed for infill, walls, etc. all to the same slow value and set it slow like 30mm/sec and check if it is better.

Since the problem only occurs after a retraction, I am confident that it is also somewhat caused by it. As you can see in the video, the speed is no problem for the extruder after it has established a steady flow. The problem is also occuring in the wall, not the infill. There is no infill in that part of the print.

[Smithy 1,144]

Sorry my failure, I meant support structure, not infill.

Anyway, have you checked your retract settings? Maybe the retract is too long for your printer. I don't know the Anycubic, but I guess it is a direct extruder, right? 

 

I think the problem is, that when your printer retracts and then should forward the material again, that he don't forward it enough. Then you get the underextrusion until the filament is at the nozzle again. Check also the tension of the feeder gear and the gear itself, maybe the filament slips a little bit. 

[kulfuerst 6]

25 minutes ago, Smithy said:

Sorry my failure, I meant support structure, not infill.

Anyway, have you checked your retract settings? Maybe the retract is too long for your printer. I don't know the Anycubic, but I guess it is a direct extruder, right? 

 

I think the problem is, that when your printer retracts and then should forward the material again, that he don't forward it enough. Then you get the underextrusion until the filament is at the nozzle again. Check also the tension of the feeder gear and the gear itself, maybe the filament slips a little bit. 

The problem occurs in all line types, it doesn't matter what the kind is. The only thing that matters is that a retraction took place beforehand. what baffles me is that the spacing of the dots decreases until it becomes a steady line. Esteps are constant though, aren't they? What causes the frequency of the stuttering to increase? Also, the fact that these dots are placed shows that there is indeed filament in the nozzle, otherwise nothing would be extruded. Long story short, this makes absolutely no sense to me.
I am not the first one to discover this issue btw. A google search yields many entries in forums of people having the same issue, but no solution anywhere. I find it surprising that this somewhat common issue appears to be so difficult to find a solution to...

[kmanstudios 1,120]

1 hour ago, Smithy said:

Sorry my failure, I meant support structure, not infill.

Infill too.....

[Smithy 1,144]

1 hour ago, kulfuerst said:

I am not the first one to discover this issue btw. A google search yields many entries in forums of people having the same issue, but no solution anywhere. I find it surprising that this somewhat common issue appears to be so difficult to find a solution to...

And is it spread among different printer types or can it be narrowed to a specific type?

 

I never had such an issue, that's why I am asking for.

[kulfuerst 6]

12 minutes ago, Smithy said:

And is it spread among different printer types or can it be narrowed to a specific type?

 

I never had such an issue, that's why I am asking for.

Not limited to a specific printer as far as I can tell, but don't quote me on this.

[kmanstudios 1,120]

I believe the speed is the most appropriate solution. Have you given that a shot?

 

I know I do not have this issue on either the S5 or UM3.

[kulfuerst 6]

yes I have. And according to other entries in other forums and also this one, variations in speed made no difference for them either. If it had anything to do with speed, then I believe this stuttering would also occur constantly, not only at specific points. I'm not saying that I know what it is, I really don't, but some things can be ruled out and speed appears to be one of them.

[kulfuerst 6]

here is just one example of this issue occuring previously for other people. In this thread, which was unfortunately discontinued, a lot of parameters were also changed with no noticeable results. From my observations I can second the statements made in it. In my case though, I even have a video which unmistakably shows what exactly the problem is, not just a picture.

[Smithy 1,144]

I think it is not software related or not related to Cura. Do you use Cura or something else? Have you made a cross-check with another slicer, just to be sure?

 

If it is hardware or firmware related it will be hard because most people here have Ultimaker printers and the knowledge with other printers are limited. But maybe someone else has an idea what you could check.

[kmanstudios 1,120]

1 hour ago, kulfuerst said:

here is just one example of this issue occuring previously for other people. In this thread, which was unfortunately discontinued, a lot of parameters were also changed with no noticeable results. From my observations I can second the statements made in it. In my case though, I even have a video which unmistakably shows what exactly the problem is, not just a picture.

Kinda overlooking that this example is not a UM printer. Ergo, a bit more difficult to diagnose for a lot of people here unless they are expert on your brand of printer.

 

What I would hope you understand is that 3rd party printers behave differently. Hence my specifying that the printers I have are UM printers.

 

What would be best is that the owners of the printer companies actually made proper profiles for the printer to be included. I do know that many people try to contribute to their brand of printers. But it is not fully vetted.

 

And, @Smithy's suggestion to cross check with another piece of software will very much help identify issues.

Edited November 25, 2018 by kmanstudios

[ungutknut 4]

Just to show this issue affects multiple users: me too!

 

Since I tried upgrading from Cura 2.7 to any 3.x I'm unable to achieve flawless shells like I was used to before. No matter how slow I print (usually between 20 and 30mm/s), no matter how high the extra prime amount (tried until +1mm³). Eventually there are always gaps in the z-scar.

 

So I'll try to increase acceleration/jerk (and ringing... *sigh*) and see how activating retraction at layer change will affect the results. I'll upload some pictures when testing is done.

 

Is there some preferred thread to handle this issue? Seems to be quite fragmented over several threads.

 

(Printer: Wanhao Duplicator i3 v2.1 with MS all metal hotend and 0,5mm nozzle. Used to print in decent quality with 2.7. Currently unable to print anything useful with 3.6).

 

edit: Here's another one with (probably) the same issue:

 

Edited December 12, 2018 by ungutknut

[kulfuerst 6]

I have also found some other threads in multiple forums, but nobody I talked to has found a solution or even a cause! Most have given up. Currently I am also out of ideas what could be causing this. In the meantime I have switched from stock to a titan extruder, but the issue persists. I therefore rule out the extruder as a cause with relative confidence. If anything, my current working hypothesis is that retraction distance could have something to do with it. Still figuring it out.

[kulfuerst 6]

I think I may have solved it! In all my prints that show these defects, a section was made up of very fine lines with which cura fills gaps between walls. I believe that during these very fine lines, filament oozes away DURING printing because extrusion is so very low, causing ever so slight overextrusion in the structures prior to the retraction! So after the next travel move, the nozzle is empty and has to first fill up before the print can continue as normal. Usually, these defects occur in infill and are not visible in the finished print. This is unless there is no infill, either because the print is very thin and consists of only walls, or because a part of it is narrow and made up of only few lines to begin with! That is also why this issue shows up besides holes so often. I can't believe I may have finally figured it out

[Camaro 0]

Hello,
I think I'm having the same issue for about half a year now... My printer is a Hypercube Evolution. At some point I switched to a Titan Extruder as you did, which as you said didn't solve the problem. I also tried different slicers All had the same issue.
The problem can be minimized by disabling "Outer before Inner Walls" in Cura, effectively hiding the issue inside. This however works only for large "islands" on every printed layer.
Further i switched to a original V6 hotend, changed the nozzle, tried different heatbreaks (PTFE Inlay, full metal and titan) and replaced the bowden tube multiple times (currently I'm using a Capricon bowden tube ~60cm).
Your theory about the small parts could be right. I also see over extrusion on some parts or a blob at the end of an extrusion right before a retraction.
Did you find a way to fix this issue? Or have you tried other slicers too? Im really frustrated over this issue.. Would be nice to finally have a fix for it.
Thank you for your help

[kulfuerst 6]

Hi Camaro,

I have started rigorously drying all my Filament before every print! this solved the issue almost entirely. with some filaments that tent to ooze strongly no matter what, I disable "fill gaps between walls". this solves it in even the most stubborn cases 🙂

[kulfuerst 6]

in cura I also enabled "equalize filament flow" which helps sometimes. the setting is extremely moody though. sometimes it does nothing, other times the difference is huge. it's really strange. the preview in cura also shows this but I've stopped trying to understand cura a long time ago 😄

[Camaro 0]

Thank you for your fast response. I will try your suggestions and report back on any new findings. 😉

[samtaylor 0]

Retraction prime extra amount. Is the answer your all looking for.