Scars on Monotonic  

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jem
 jem
(@jem)
New Member

Hi everyone! 

I have this problem in which line scars on the top layer of the print will appear, even though the top fill is monotonic. 

Default Settings + changes below for the left print(from the photo):
Infill - 10% Gyroid
Top & bottom Infill pattern - Monotonic
Infill/perimeters overlap - 50%
Wipe while retracting is untick

Default Settings + changes below for the right print(from the photo):
Infill - 10% Gyroid
Top & bottom Infill pattern - Monotonic
Infill/perimeters overlap - 50%
Wipe while retracting is untick
Extrusion Multiplier - 0.95
(the change of extrusion multiplier created tiny gaps)

I tried to do ironing as well but it didn't turn out nicely.

Is there a way to get rid of that line scars on the top layer? or did I miss out something else?
Thank you!

Posted : 20/04/2021 9:24 am
Clarmrrsn
(@clarmrrsn)
Honorable Member

Can we see the bottom of those prints to see what the first layer looks like?

Or can we see some first layer photos.

Did you try this for the first layer adjustment?

life adjust Z - my way – Assembly and first prints troubleshooting – Prusa3D Forum (prusaprinters.org)

 

Tank you very much!...
Posted : 20/04/2021 2:15 pm
bobstro
(@bobstro)
Illustrious Member

The problem you appear to be having at the red arrows is that a bit of filament ooze is dragged across that nice smooth top surface when the extruder moves. Two things to try:

  1. If you're using a 3rd party filament, do an extrusion calibration multiplier calibration. Even slight over extrusion can contribute to ooze & stringing. If your slicer settings don't match your physical filament, there can be a mismatch in expected versus actual extrusion.
  2. Reducing temps slightly can help with oozing.
  3. If you still have problems with top surface scarring, you can try increasing Printer Settings->Extruder 1->Retraction->Lift Z. This setting inserts a small vertical nozzle (Z) position lift on every retraction in preparation for a move. I believe the default is 0.6mm in the Prusa presets. 

Save your current  3MF project file, zip it up, and attach it to a reply here so we can see your part & settings and give better recommendations. It would be helpful to view physical extruder moves after slicing.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 20/04/2021 6:33 pm
Neophyl
(@neophyl)
Famed Member

I think its an artefact from the layer below the monotonic.  Only the very top layer is monotonic, the layers below are just normal rectilinear infill.  If that builds up a line there then a single layer isnt going to help.  The request has already been made on github to extend monotonic to cover other layers than top/bottom precisely due to observations like this.

I do agree though that if the filament was properly calibrated then the effect would probably be (alot) less and then a single layer of mono might be enough.

Posted : 20/04/2021 8:03 pm
jem
 jem
(@jem)
New Member

Hi everyone, thank you for your replies.
I'll try out your suggestions and see the results.
Here is the picture of the bottom parts and I've attached the 3MF file. Thanks! 
zero 5

Posted : 21/04/2021 1:31 am
Tim
 Tim
(@tim-2)
Illustrious Member

And a little bit of belt and/or bearing slop can accentuate the layer infill collisions and voids. 100% monotonic is the real solution - even to the point of ensuring all infill goes one direction - not just per layer. i.e., infill always moves front to back, left to right ... and never fills front to back on one layer then back to front on another. 

It is always wise to get more than one opinion...
Posted : 23/04/2021 9:43 am
Neophyl
(@neophyl)
Famed Member

@-2

Tim as that's already been requested I hope they implement that.  I did see a post on github from one of the devs saying they were considering it on a time vs quality basis and making it default.

Posted : 23/04/2021 12:31 pm
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