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Blobbing at corners of print only on one side, help!  

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Pixel Visions
(@pixel-visions)
Active Member
Blobbing at corners of print only on one side, help!

I work with pixel art and will be doing a lot of tight-cornering prints, and I’m having a bit of a surface issue.  This only occurs during the infill of small sections being printed after the main body of the piece is complete, and only on one side (I assume this may be due to the different direction of nozzle movement on that side?) I watched the first layer, and the same issue was occurring, so I would assume its happening on each layer of the print. Any idea what can be tweaked to help resolve this?  I suspect its an issue of overextrusion at the very end of tight infills that end at a corner, but wasn't sure if adjusting the retraction or Linear advance for such a specific area was recommended/possible.  I have done a lot of the “book learning” on all these functions, but once I’m in PrusaSlicer there are so many moving parts that I get intimidated.  The pics below show part of the whole piece, the “bad corners” on one side and the “good corners” on the other side.

Problem corners

Posted : 26/01/2021 1:58 am
JoanTabb
(@joantabb)
Moderator
RE: Blobbing at corners of print only on one side, help!

Could you please save a model as a .3mf Project file, in prusa slicer,  then Save the file to a compressed Zip File, and attach it to your next post, please. so we can see what your settings are like,  do you have a picture of your first layer/ Or the underside of a print that we can see too please? 

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 26/01/2021 11:31 am
Pixel Visions
(@pixel-visions)
Active Member
Topic starter answered:
RE: Blobbing at corners of print only on one side, help!

I will zip a file momentarily, but I was using the default Prusament filament settings and default .2mm quality settings (the only change being 100% fill and rectilinear infill) in the most recent release of PrusaSlicer for this print if that speeds up the process.

Posted : 29/01/2021 1:37 am
Pixel Visions
(@pixel-visions)
Active Member
Topic starter answered:
RE: Blobbing at corners of print only on one side, help!

Here we go!  I unfortunately already sold the piece this print was made for (the problem side would not be visible in this case) so I can't take a pic of the back.  I am pretty comfortable that I have dialed in my z-adjust for the new filament, and am currently experimenting with bed temps to get better bed adhesion with Prusament (the included silver PLA had no problems, but Prusament seems a bit more fussy) I have also confirmed that the corners in question are the endpoint of the infill extrusion on these sections.

Attachment removed
This post was modified 10 months ago by Pixel Visions
Posted : 29/01/2021 1:58 am
JoanTabb
(@joantabb)
Moderator
RE: Blobbing at corners of print only on one side, help!

@pixel-visions

Hi 
this is a very thin item, 

the only thing I see which is a little odd, is the 100% infill

100% infill has been problematic for me. some infill patterns will not accept a 100% value... e.g.Gyroid and Honeycomb... 
in this instance, I would have simply increased the number of top or bottom layers and there would have been no need for any infill...   the model was 10 layers thick, your layer height was 0.2mm,  you had 5 top layers and 4 bottom layers so there was only one layer left to be infilled, increasing to 6 top layers or 5 bottom layers would have resulted in no need f0r infill layers.

top and bottom layers also give 100% infill by default, but don't seem to give the same issues

as far as your first layer goes, Try 70C for PLA. 

I find that giving the build plate a really good wash, with hot water and a tiny bit of Dish detergent, then rinsing well with hot clean water then immediately drying the surfaces, gives a good adhesion base for PLA, without any other surface preparation. 

I am currently printing your test piece in Prusament Galaxy Black, we will see what it looks like, in the morning. 

 

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 29/01/2021 2:48 am
Pixel Visions
(@pixel-visions)
Active Member
Topic starter answered:
RE: Blobbing at corners of print only on one side, help!

Thank you for looking into it! The software did let me know the default gyroid pattern couldn’t be done at 100%, and automatically switched to rectilinear when I made that change.  This piece is a structural backing for a sculpture hence the thin, solid production.  I have also designed a hinged easel which is being attached to the backing, which has the same little bit of “squish” of excess filament only at the very end of the last corner of each layer infill.

Posted : 29/01/2021 4:28 am
Pixel Visions
(@pixel-visions)
Active Member
Topic starter answered:
RE: Blobbing at corners of print only on one side, help!

How does it treat the external layers differently?  It seems to be going through the same process for the top and bottom layers as it does for the ones with infill, and you can see each corner get that bit of overextrusion at the completion of each layer (on alternating corners, since it seems to change angles with each layer under the currently settings.

Posted : 29/01/2021 4:33 am
JoanTabb
(@joantabb)
Moderator
RE: Blobbing at corners of print only on one side, help!

This was my print

Above, shows First Layer

Finished, 


worst corner

 

 

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 29/01/2021 12:29 pm
JoanTabb
(@joantabb)
Moderator
RE: Blobbing at corners of print only on one side, help!

there is obviously some difference between the way layers are sliced 
take a cube model say 25mm cube
Use 0.2mm layer heights
set top infill Like this 

For demonstration purposes

When you slice the model, you will get something like this 


as you can see, there is some sort of intelligence that differentiates between 
Top Layer, infill pattern...                                                        we chose Hilbert Curve   
top layers layers infill excluding the uppermost layer...    Prusa Slicer Chose Rectilinear!
Fill Pattern...                                                                                We chose 100% Octogram Spiral
Bottom layers infill...                                                                 Prusa Slicer Chose Rectilinear!
First layer infill....                                                                       We chose Concentric

If you use 100% rectilinear it's likely that the results will be similar to the automatic top layer infill and the automatic bottom layer infill.   certainly earlier versions of Prusa Slicer and Slic3R struggled with 100% Fill density in previous versions, so I have got used to using top and bottom layers to ensure solid models. 

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 29/01/2021 1:47 pm
Pixel Visions
(@pixel-visions)
Active Member
Topic starter answered:
RE: Blobbing at corners of print only on one side, help!

Okay, thanks for the thorough look into it!  I will give your suggestion a try on my next piece (may not be the same backing, but will almost certainly run into the same bugbears)

Posted : 30/01/2021 6:19 pm
JoanTabb
(@joantabb)
Moderator
RE: Blobbing at corners of print only on one side, help!

@pixel-visions

Good luck!

Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 30/01/2021 6:28 pm
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