z-seam error?

[Kayu 0]

Hello community,

 

do you habe any idea what's happend here?

 

cura 5.3

 

On the build plate the walls are totaly fine but on the upper most wall layers the seam shows a strange outer wall shift.
Settings are pretty standard and i tried "coasting" / "combing" / "wipe" on and off.

 

Additional issue: every 7mm, there is a little blob in the seam line.

Would like to get some help from "practiced people",
cause i'm more the trail and error user...

i read about "coasting" / "combing" / "wipe", that's how i fixed the random z-seam blobs and make it smoth on one side...
but not even the whole side.

 

 

[Kayu 0]

Drastically reduced the inner wall flow from 100% to 70%...

I'm not happy with this solution... but it works for this piece of print...

 

checking the inside of the walls, it looks pretty solid, so it's enough flow...

 

But checking the top I can see a space between the lines...

so it must be something between this... maybe... ?!

or did i missed something i could give a try for?

 

And still wondering why on the long pieces the walls on the build plate working like a charm but not on the top. 🤔...

[GregValiant 1,409]

Load the model in Cura and set up to slice.  Use the "File | Save Project" command and post the 3mf file here.

What printer are you using and what material are you printing with?  

[Kayu 0]

Hi, thanks for your help.

 

I saved 2 files, the first with my major issues, the second with my adjustments to fix the top most walls at z seam, but with the problem on top surface areas.

 

I'm using a new Ankermake M5, but i know i got some one the same problem on my old anycubic i3mega with small parts like a tower of 5mm width... all small parts or small walls overextrude at layerchange.

I watched my last prints and noticed that on layerchange the starting prime line extrude to much.

also tried rectraction on layer change but no help at all.
Only setting wall flow down to 70-85% worked "ok".

Filament spezification: Kaisertech Filament, PLA 1.75mm, gold, tempature: 190-220 °C

 

 

Also tried another filament:

ERYONE Silk PLA Filament 1.75 mm, red copper (_adjusted.3mf)

AM5_SpoolholderSpindel_forum.3mf AM5_SpoolholderSpindel_forum_adjusted.3mf

[GregValiant 1,409]

I never know how experienced a poster is here is so if some of this seems basic, please don't take offense.

I'm looking at your settings.  A retraction speed of 120mm/sec may be beyond the material's capability to react.  The retraction should relieve the pressure in the nozzle, but you don't want to suck air into the nozzle.  With a speed that high, you may be creating an air bubble in the nozzle when the filament snaps backwards.  When the prime occurs, it has to account for that empty volume before the pressure comes back up.  With Coasting enabled, that can make the situation worse as the pressure falls off when the extruder stops before the end of an extrusion.

Looking at the rest of the speeds, it sounds like you have a very capable printer.  I would suggest sneaking up on the speed settings to find that speed where everything works well together.  I know my Ender will print certain models at 175 but on a model like you posted there is no way for the speed to approach 175 much less your setting of 200.  The print speed of the top layers of that model is your minimum speed of 50 (within the gcode).  That's a 6 second layer time and brings layer cooling into question.  Even the middle layers are only 70 to 75mm/sec.  You want a situation where the nozzle pressure is always consistent.  That means realistic print speeds so every time there is a retraction it is from the same base pressure level within the nozzle.

Back to the material, dependent on the shape of the model, I often print PLA between 50 and 125.  I never print PETG above 50 and even then I print the outer walls at 35.  The "speed comfort zone" for each material is just different.  Silky Silver PLA printed at 75 looks kind of gray.  But print the outer walls at 35 and they look like chrome.

I think if you print that model at 65 and with the retraction speed at maybe 40, and with coasting turned off, you will get better results.  If you sink that model into the Cura build plate you will only need to print that top problem area for testing.  Cura's "ChangeAtZ" post-processor might come in handy for dialing in the retraction speed.

 

In 3D printing, "Everything affects Everything", there is no "Easy" button, and "crossing your fingers and hoping for the best" doesn't work very often.

[Kayu 0]

Hello, thank you for your help.

I do not feel offended at all, even if I am familiar with many ideas that you would give me to help.

I can't hear any problems with the filament at that speed, it's not breaking or sounding like scrubbing, I think the direct extruder can handle that speed.

I understand the idea behind retracting too fast and maybe sucking air back into the nozzle, but not at this low amount of filament. My understanding is that the distance is the filament length, 4mm is not that much. but I will try and reduce the speed. (it's a direct extruder, I think I could reduce the length to 2mm, resulting in less pressure change, also worth a try...).

On the other hand, the printer prints at max 300mm/s and would give an acceptable quality of 0.3mm layer height for larger parts. And as you can see from my first prints, the quality is great at 200mm/s with 0.2mm layer height, except for the thin walls. I have reduced the wall speed to 150.... maybe I can reduce that too.

But the problem doesn't seem to be here, because the "blob" isn't created during printing, as I observed, the extra filament is extruded right at the layer change and at the beginning of the first layer line.

I printed a test part at reduced speed... (not the best timing that my filament runs out...)

min layer time: 6->12s

min speed 50mm/s

retract distance 4->2mm

retract speed 120->60mm/s

printspeed 200->100mm/s

 

i know i should change less values step by step... if something changes and leads to better quality, i would go step by step. but i think the problem is in a totally different part.
this is the result: nothing changed... still watched the same issue, on the thin walls the extra amount came out of the nozzle at layer change. There is no problem with the mid part where i got infill...

 

only the reduced inner wall flow results in good quality at this thin walls (thin... i mean, it's measured 1.2 mm thickness with 3 walls printed at 3.8mm line width)

 

One idea, it could be the problem of size measurement and gcode calculation:
original stl file: wall thickness 1.5mm, meassured 1.2mm ... 

cura setting: 0.38mm line width. rounded to = 3 lines...
2 outer line and 1 inner line. the inner line need's to extrude more filament, like we can watch in cura:

in a perfect condition the inner wall needs to be 0.74 mm width...

second setting: even with wall thickness: 0.74mm... (2 times line width) this should be 1.48mm i couldn't get a wall print with 4 lines?! i would like to edjust the model/settings to get a testprint with optimized walls... any ideas?`(did i missed something?)

 

 

The 50mm/s above results from the minimum layer time of 6s and the speed of 50.

Could be that my middle layers also print in an adjusted time....

It would be nice to see the layer time in Cura.... Feature Request (might not be that problematic, even an approximate seconds would be nice to see if the minimum shift time was reached or not...).

I don't think cooling is the problem:

It's that the nozzle changed layer, you can see the extra amount of filament coming out of the nozzle and a blob of filament being printed, I observed that and came pretty close to the result of a wider "V" shape of the problems on each higher layer because the extra amount is always more with each layer and scrubbed to the sides.