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kulfuerst

Stuttering extrusion at the start of each new layer

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Posted · Stuttering extrusion at the start of each new layer
3 hours ago, samtaylor said:

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

 

Unfortunately, no. It's not that simple.

Retraction extra prime compensates for material that oozes away during travel moves, but this is not the issue here. A function that would solve the above mentioned problem (but doesn't exist), would be something like "gap-fill extra prime amount" that compensates for material that oozes away during low flowrate print moves.

 

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Posted (edited) · Stuttering extrusion at the start of each new layer
9 hours ago, samtaylor said:

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

As kulfuerst mentioned, Extra Prime didn't solve this issue, but also led to blobs on other parts of the print.
I dried my filament and played with 'Equalize Filament Flow' but wasn't able to improve the issue. I will probably revisit this setting though later on.
As I had this problem with any slicer and a freind  of mine has a similar setup I thought about what about my hardware is different from his: than it occured to me, that I'm running an 8-bit board with a 0.9° extruder motor on the E3D Titan and use 1/16 micro stepping on my extruder which led to about 800 steps per mm. I changed to 1/8 microstepping  which massively improved quality. I guess the necessary step rate for driving the extruder on the retracts simply exceeded the one my board was possible to generate.
I'm not a 100% sure about this explaination, but reducing the microstepps worked for me. This also wouldn't explain why this problem didn't appear after each retract.
As a next step I want to exchange this board with an 32-bit one. After that I will try increasing the microstepps again and if I'm right the problem shouldn't reoccur.

Edited by Camaro

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Posted · Stuttering extrusion at the start of each new layer
On 11/24/2018 at 9:40 PM, 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.

Just a quick update to my findings on this issue:

 

I think I got it fixed now and what made the biggest difference was to set a small value (e.g. 1mm) for "max comb distance with no retract". These unretracted travel moves over printed parts were the cause for filament oozing away before each layer.

 

A suggestion to people experimenting with "equalize filament flow" and such: there's a new feature in marlin called "linear advance"... looks very promising although I haven't yet used it.

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Posted (edited) · Stuttering extrusion at the start of each new layer

Hi,
yes 'max comb distance' brought some improvement for me too. Even better worked enabling 'connect infill lines' and turning off combing completely. (this is similar to what slic3r does by default) This results in slightly more filament used, but improved my print quality a lot.
I also experimented with the Linear Advance feature in Marlin. My bowden tube is about 60cm in length, which resulted in a huge K-factor for the algorithm. This in turn slowed my printing speed down a lot (probably due to other not optimal settings made in Marlin) and made the extruder quite noisy. At those speeds the quality was acceptable even without LA and at least the extruder was quiet.
I also tried the Pressure Advance feature in Klipper, which also caused the extruder to be noisy, and mainly fixed the overextruded edges. So I turned it off again until I could fix the main issue.
Hope this helps someone with similar quality issues.
 

Edited by Camaro

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Posted · Stuttering extrusion at the start of each new layer

The reason these topics are fragmented and rare I think is because most people (like me) don't experience them.

 

It's hard to diagnose a problem when it doesn't happen to me even when printing at 150mm/sec.

 

 

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Posted · Stuttering extrusion at the start of each new layer

Yes, I would say so too. but that makes it really hard to find a solution for it. I also would guess that this is some kind of configuration issue, as I already swapped out every possible component, but nothing really worked.

The last thing I changed were the Stepper drivers. I previously had TMC2130 on XYZ and MKS LV8729 for my Extruder. Now I use TMC5160 for all axis. They are total overkill but at least it reduced the issue further. However, this couldn't have been an issue on its own, because a friend of mine used the same combination and had no problem at all.
I am on high-end hardware for the whole extrusion system now but still have the problem on higher speeds.

 

@gr5 Are you printing with a direct extruder? But with 150mm/s printing speed, I guess it's a bowden. And if so, how long is your bowden tube?


I will report back if I have done further testing on this issue. Until then I'm printing slow (<65mm/s), which is kind of a shame for a CoreXY..

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Posted · Stuttering extrusion at the start of each new layer

Okay this is going to be my last post on this topic since the issue has been fixed a while ago. The fix is posted on page 1 of this thread. I have answered numerous personal messages on other platforms where I also posted this question and the fix has so far been 100% successful with everyone who came to me directly as well as myself. People have also shared before and after pictures with me like the one I'm attaching here.

@gr5
Printing at 150mm/s makes the issue far less likely to appear, as anything that increases the feedrate of the extruder (layer thickness, layer height, print speed, flow...) masks the issue.

before.jpg

after.png

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Posted · Stuttering extrusion at the start of each new layer

69869082_382547592390061_7574180714896162816_n.thumb.png.bd7512c780106131226d26285ff1fb1a.png69836285_881707762223148_2337230737587044352_n.thumb.jpg.2bac3899f030d499e471b739c527db9a.jpg

 

Solved the issue for another person. Before - After

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