Under-Extrusion Following Seam

[Benjamin4456 0]

Hey all, I'm fighting an artifacting issue that has now been plaguing me ever since I installed an SKR Mini E3 V3.0 board in one of my Ender 3 Pros.

 

The issue in particular is that at the beginning of some wall segments there is significant under-extrusion.  On some parts, printing inner walls first hides it, but on others it is still visible.  I prefer printing outer walls first, but that's an aside.  I've messed with retraction settings, extra prime distances up to absurd levels (higher than retraction values), disabling retraction when moving to the outer-wall, wall speeds etc. all with little effect.  The only thing that has sort of helped was the high extra restart (prime) distances, up to 2.0mm, but even then it doesn't solve the issue completely and seems indicative of another issue.  I've also tried fresh installs and default profiles of Cura, both 4.13.1 and the new 5.0 beta (the beta actually works a tad better).  Material in question is just some eSun PETG, which I've printed lots of successfully in the past.

 

The machine is a modified Ender 3 Pro: Micro-Swiss all metal hotend, garolite bed, metal tensioner, tighter bowden tube, etc. - nothing crazy.  Any slop in the bowden tube fittings is below the level I can detect with my eyes.  The printer is otherwise tight and well-behaved, and it had been printing fine for over a year before swapping boards.  The only other change I made at that time was taking my microswiss hotend from another printer and installing it on this one.  I don't see that as a likely cause, but it is a possibility I suppose.

 

I've also tried many many firmware compilations, ranging from bare minimum Ender defaults to every combination of junction deviation, linear advance, s-curve accel., etc.  Writing this now I did however just realize that I never tried disabling square-wave stepping, so I'll test that.

 

Attached below are a couple photos showing the glitches.  My apologies for the photo quality, it's a shiny PETG filament and that's as close as my phone can focus.  The parts on the bottom row have the inner wall printed first, and the top is the opposite.

 

 

I'm getting close to reinstalling the old board as a sanity check, although I'd of course rather avoid that.  Last time I troubleshot this was about three months ago before giving up for a while.  I'd like to get this printer up and going again though, as I have some things I would like to use it for.  If anyone has ideas please do share, I'm just about out of my own.  Thanks in advance.

[Benjamin4456 0]

Just updating that disabling square-wave stepping changed nothing.

 

What's most annoying is that the rest of these parts looks great, except for wherever the seam is.  Everything else is tuned in pretty darn well.

[GregValiant 1,251]

When the nozzle oozes on long travel moves prior to starting the outer wall extrusion then it can take a few mm's of movement before the pressure comes up in the nozzle.  The coasting setting can make it worse.  The problem can really show up on horseshoe shaped objects as the nozzle has to travel a long way on a combing move to avoid jumping across the gap.

If you aren't using Z-hops then there is a post-processor called Retract Continue that spreads the retraction across the travel moves instead of pulling the filament back and then traveling.  It might help.  One of the new settings in 5.0 is to print the walls "Outside to Inside" and it is the default.  With the outer wall first after a long combing move the initial low pressure problem is visible so try setting it to "Inside to Outside.  If the problem occurs on an inside wall then it usually get hidden by the outside wall.

[Benjamin4456 0]

True, quite true.  Thank you for the reply.

 

It's worth mentioning that "outside to Inside" isn't a completely new setting as it's been in 4.x.x for some time - this is what I was referring to in the photos and my tests.  The default value and visibility did change though as you said, as did it going from a check-box to a drop-down.

 

I'll take a look at combing as it's not something I'm sure if I've used in the past.  I know it is enabled presently though, and the worst example I'm running into is on a sorta half-a-horseshoe, so that makes some sense by how you described it.

 

Coasting is disabled, although linear advance is in use.  I did notice the issue get slightly worse when using linear advance vs without, but it cleans up the other corners enough to out-weigh it.

 

I'll continue experimenting and see if anything clears it up.  For the time being I've swapped to working on the same issue with my dual extrusion printer, but I'll probably bounce back and forth.  The normal Ender 3 is at least usable now, so long as I can stand seeing the wall glitch; my dual extruder setup has yet to be tuned in, so I'll multitask with it.

[liebherk 1]

Did you ever figure this out? I'm having similar struggles with a similar setup - skr 1.4 turbo Ender 3, micro swiss knockoff, no coasting, yes linear advance, adding retraction extra prime amount helps some.

[Kotaztrafee 2]

I have been fighting this problem too on my QIDI X Plus. I even discovered and replaced a bent Z screw that helped a separate issue but not this. Accelerations, flows speed and all the rest that everyone has mentioned.
My model is 100% a horseshoe shaped half pipe so.....
 

On 5/3/2022 at 9:58 PM, GregValiant said:

The problem can really show up on horseshoe shaped objects as the nozzle has to travel a long way on a combing move to avoid jumping across the gap.

But ........(in real time thinking commentary)  SO WAIT!   That's it! The combing! Retraction doesn't work with combing on, from my understanding and from the gcode info that shows no retractions with combing on. With combing off retraction can be adjusted for any stringing! Going to go try it now!

THAT'S IT!!!!  COMBING OFF !!! 
No stringing no under extrusion after the seam!
 

Thank You GregValiant !!!

[GregValiant 1,251]

There is a post processor called "Retract Continue" that you might try.  Instead of one quick retraction it does a shorter initial retraction and then continues the rest of the retraction during the combing moves.  That can keep drooling to a minimum and may help you out.  The current version doesn't understand z-hops so if you just have to have Z-hops you will have to ask me nicely for the re-write I did.  (I submitted a pull request but it has yet to be approved.)