Initial Layer Under Extrusion

[randomdude583 0]

Using Cura 4.4.1

 

I am seeing a strange behavior, where my first layer severely under extrudes, just a thin, wispy layer that does not usually stick to the bed. I have my machine configured to print a line on the edge of the build plate first to prep the extruder, and this works excellent, but then the first layer fails right after that.

 

The really strange thing is that enabling a raft completely fixes the issue. First layer of rafts print perfect, and I dont have any issues. Using a brim or skirt has the same issues as printing without a raft. Any ideas why this would happen and what I can do to resolve it? I have attached my configuration settings.

 

Thanks!

curaProfile.curaprofile

[torymiddlebrooks 0]

I am using Cura 4.10 but I am having this very same issue and it's most notable with TPU. The first layer is not printing correctly. 

I am using totally default profiles for both.

Screen capture 1, it's a brim and you can see it's got good solid connect to the build plate on the hexagons.

Screen capture 2, it's a skirt and you can see that the PLA is now a single wall and TPU is just dots.

 

Does anyone know why this happens?

It seems like the first layer is being reduced in wall thickness, as you can see in the line color coding.

PLA with Brim

PLA with skirt

TPU with brim

TPU with skirt

Edited September 14, 2021 by torymiddlebrooks

[torymiddlebrooks 0]

Any one got anything to say about this?

[GregValiant 980]

You need to post a 3mf project file.  Use "File | Save Project".  In your case - post one with the TPU and one with PLA so somebody can do a comparison.  

[torymiddlebrooks 0]

Done and done.

The issue comes into play when selecting Brim or Skirt, and it's with both material types. 

Pick either file, slice it with a brim and then slice it with a skirt and look at the first few layers to see the problem.

This happens no matter the model I use, it has something to do with the initial layer. I have attached a screen shot showing a cross section, you can see the first layer with a skirt. I don't know what to change to fix this but it seems problematic. 

Component1.3mf Component1.1.3mf

[GregValiant 980]

There are a couple of things.  (BTW one file was just the model, the other was a project file for TPU.

Foremost - the Initial Layer Horizontal Expansion of -0.2 is a problem for the narrow walls of the Hexagons.  Taking .2mm off of each side is causing them to pretty much disappear.  The only thing left are dots at the intersections.  That makes it look like under-extrusion but it's really NO extrusion.  I know you're probably trying to fight elephant foot but for this model I think I would prefer a little elephant foot.  You could try running the bed cooler to compensate.

 

The Initial Layer Line Width of 120% may be causing issues as well.  Probably not to the extent of the ILHE but you could try dialing that back.  Remember that Line Width is the index distance between your extrusions and your initial layer line width is .46mm and the hexes in the center are thin walled.

 

You have Compensate Inner Wall Overlaps checked and it is causing a bit of under-extrusion as well.  Since the outside lower corners of the box have radii and the inner corners are sharp that compensation comes into play.

 

For most models the only thing I leave checked in the Mesh Fixes section is Union Overlapping Volumes.  They are special usage settings but maybe you do need them.

 

I think the settings are causing, not conflicts really, more like me in third grade - "unacceptable behavior".  The -0.2 ILHE, the 120% line width, Compensating Overlaps, are all contributing.  It's a question of balance between the settings.

 

Sliced as downloaded:

 

Then with ILHE at 0.0

 

ILHE at 0 and Initial Layer Line Width 100%