Cura slicing small gear teeth non-uniformly

[krona 0]

Im using cura 5.0, .5mm nozzle with a .3mm layer height. Ive printed this part in the past without this issue 

Edited June 15, 2022 by krona

[GregValiant 1,240]

Hello @krona.  With the model loaded in Cura use the "File | Save Project" command and post the 3mf file here.  With the changes in 5.0 you will need to revisit your settings.  Off the top of my head I'd say it looks like your line width is too much for the teeth.  If you are at .5 line width try dropping it to .45 and see if the preview gets better.

Enabling "Print thin walls" may help as well.

Two other settings that didn't exist in 4.x are "Split middle line threshold" and "Add Middle Line Threshold".  Try setting them to 50%.  They can effect long thin features and how may passes the nozzle makes to print them.

[krona 0]

Pinion22t.3mf

[krona 0]

Setting split middle line threshold to 50% definitely cleaned up the preview, changing add middle line threshold didn't appear to make a difference so I left it at 94%

[GregValiant 1,240]

When you have features on a part that require an out-and-back movement (your gear teeth, tines on a comb or rake) then that setting comes into play.  At 50% the nozzle extrudes while outbound and while inbound then moves to the next tooth.  At 75% (or whatever it was) Cura decides on a single out extrusion, jumps to the next tooth, and then a single extrusion coming back towards the hub.  Not at all what you want on that model.

On a small detailed model like that I would think a .4 or even a .3 nozzle would be a better choice.  The line width can be smaller than the nozzle size but there is a point where things start to break down and a smaller nozzle is in order.  With the .5 nozzle the teeth don't really have the correct profile.  With a .3 nozzle they look like gear teeth.

Edited June 16, 2022 by GregValiant

[rosaeargentum 0]

sorry for reviving a dead thread. I can't seem to find the "split middle line threshold" in Cura 5.6.0. could someone direct me to find that setting, or whatever its been turned into?

[GregValiant 1,240]

I don't think it exists anymore.  "Minimum Wall Line Width" has a couple child settings and "Print Thin Walls" might help.

If you drop the Minimum Wall Line Width too far below the nozzle size then you won't get any squish on the extrusion and print quality can suffer.

[rosaeargentum 0]

thats mildly frustrating. ill poke around and see if theres anything i can do.