Combing mode problem: not preventing wall cross at top layer of internal features

[tgwms 0]

Hello, first post. Love the slicer: used Prusa and Cura simultaneously for a while to pick the best, and Cura won. Grateful for all the hard work put into this program; thank you.

 

Using 5.0: See the first image below. The part has a simple oval cross section here with a few internal features which terminate in the Z and need "top" layers within the infill of the part. The image shows that after printing the walls and the top of one internal feature, it travels the tip over the walls, around the outside of the part, and back into the part to print the top of the second internal feature. This leaves a big bugger. It does this when combing is set to All, Not in outer surface, Not in skin, and Within infill. But why? Should it not stay inside the part for these settings? 

 

The second image shows a correct travel between one "top" and the other "top" before starting the infill. This is combing mode off. But I can't use combing off because higher in Z the part is a C cross section and setting combing off allows a bunch of travels off the part ...causing stringing. The Not in outer surface, Not in skin, and Within infill modes work as intended higher in the part... but there are no internal top layer printing.

 

So, the answer to one of these 2 questions would be super helpful:

1) How do I keep the tip inside the part with a "top" island and combing is set to Not in outer surface, Not in skin, or Within infill?

2) How can I assign combing to "off" for the lower half of the print and "not in outer surface" higher up? ...the same method of assigning different infill percentages does not allow different combing settings.

 

 

Many thanks!

 

 

 

 

Edited June 15, 2022 by tgwms

[tgwms 0]

Any thoughts here? 

[tgwms 0]

Can anyone offer some insight here?

[tgwms 0]

Am I doing something wrong and being ignored? Or is this just not a problem anyone can help with? 

[tgwms 0]

Could someone please help here? Or at least chime in and let me know that Cura is even supported in some way? I'm about to give up on the forum in general.

[GregValiant 1,145]

I didn't see this.  Sorry.

The different combing settings are meant to keep the nozzle from marring certain areas.  Keeping travel within infill is generally a good idea and you don't want the nozzle zipping across a show surface either.

Another setting that can come into play and alter the combing moves is "Avoid Printed Parts when Traveling" (also "Avoid Supports when Traveling" when it's applicable.)  If you have Avoid Printed Parts enabled then that might be the problem.  The nozzle is moving outboard of the print to avoid the print.

In the Cura preview you should be able to turn on the Travel Moves line type and those outside moves will be apparent.  If you play with the combing settings while the Travel lines are turned on you can make adjustments and see how the different combinations affect the travel.

Generally, the retraction distance and travel speed can mitigate the size of the boogers.  The usual problem is under-extrusion after a long travel move as the internal nozzle pressure falls off during the combing move.

 

 

 

[tgwms 0]

Bingo. Turning off "Avoid Printed Parts when Traveling" did the trick.

Faith restored.

Thanks GV.