Vertical Hole Walls

[sb66 0]

Hi ,

I'm not sure if this should be in the Ultimaker or Cura section but ...
I have an Ultimaker S3 and I'm running Cura 5.1.0.
Printing Generic PLA at 210C, bed at 60C. "extra fast 0.3mm"

Some of my vertical holes have a gap between the inner layer and the infill. It a bit concerning as I need to thread these with a tap after printing. 

Edited June 6, 2023 by sb66

[sb66 0]

Printing Generic PLA at 210C, bed at 60C.
extra fast 0.3mm",
AA 0.8 Nozzle,
4 * walls at 0.8 (for strength).

Some of my vertical holes have a gap between the inner layer and the infill. It's a bit concerning as I need to thread these with a tap after printing. 

Looking at the print preview in Cura it seems to be OK.

Any suggestions would be greatly appreciated.

[gr5 2,210]

What you post *seems* like enough information for me to duplicate this but it isn't quite enough.  Hopefully your model isn't secret.  Please post a project file.  In cura menu do "file" "save project as" and post that file here.  It will contain your model, material settings, printer settings (machine settings), profile, overriden settings and much more.  Also even though you mentioned cura 5.1.0, it's worth mentioning again when you post the profile.

 

Also is that a photo of the bottom layer?  when it is partially complete?

[sb66 0]

Project file attached  (cura 5.1.0)

 

Photo is of mid layer

UMS3_Sun 9706-27A-J03 - FMS Block Cut 1.3mf

[sb66 0]

I created a smaller test sample (the full item is a 5 hour print) using the same hole dimensions with the holes the same distance from the edge and the results are OK.

 

UMS3_Sun 9706-27A-J03 - FMS Block_3D Test.3mf

[gr5 2,210]

You have line width at 0.8 (this is good as you have a 0.8 nozzle) and you have wall width at 1.6 which implies 2 walls but then you changed wall line count at 4.  There was a time when cura would make 4 lines at half width each causing underextrusion like in your photo.  But it *appears* that cura did the right thing.  Still, I highly recommend you reset wall lines to default and change wall width to 3.2mm (0.8 X 4) to get your 4 lines and to avoid cura underextruding.

 

However I don't think that's the problem.  I'll look at the gcode with a gcode analyzer that looks at flow but I don't think that's the problem.

 

So vertical holes tend to print smaller than the CAD because as PLA cools (in the first few milliseconds after leaving nozzle) it shrinks.  PLA is also very sticky - it sticks to itself like snot.  So you have this liquid rubber band pulling inward as you print that inner ring.

 

I think a solution is to change wall ordering to inside to outside so that when it prints that inner wall it can stick to the previously printed wall better.  Type "order" in the settings search box and you will also see this which I think you should uncheck: optimize wall printing order.  Unchecking that will let the initial walls cool a little more before printing the final inner most wall (I call it inner wall but cura thinks of it as an outer wall - the wall farthest from infill - the wall facing air).

 

 

 

 

[gr5 2,210]

I noticed something else more important!  That particular hole that you highlight - on those layers, that is the very first line printed for that layer.  And the nozzle comes across from the farthest corner of the print.  Almost completely across the printer.

 

I think I would leave optimize wall printing order checked (default) and change wall order ordering to "inside to outside" as that way there isn't a lot of travel to that inner circle (where the nozzle can leak a bit and then when it gets there start underextruding).