Combined infill max layer height (optional) parameter

[igiannakas]

Description

Introduced option that is only visible when combine infill is selected. It allows to set the maximum layer height over which the combination happens. Defaults to 0, which uses the nozzle diameter as it is currently done.

This setting is useful when using combine infill with layer heights that when combined result in the full diameter of the nozzle being used, resulting in weaker parts.

For example a 0.1 layer height print using combined infill for a 0.4 nozzle would result in a 0.4 layer height infill which is fast but weak. For better layer adhesion, 80% of the nozzle width should be used (0.32) which would mean 3 layers combined instead of 4.

Leaving this option to 100% (default) uses the nozzle diameter as the maximum, replicating the current behaviour. For user failsafe, 0 is also set to use the nozzle diameter.

EDIT: Updated PR to also allow a % of the nozzle size for the region.

0.1 LH combined over 4 layers for a 0.4 nozzle

0.1 LH combined over 3 layers for a 0.4 nozzle when 0.32 infill combination - max layer height is set

Available as an option on a per object

EDIT
Now also enabled as a % over the nozzle size used to print the region

Screenshots/Recordings/Graphs

Tests

Tested with setting applied to global settings
Tested with setting applied on a per object
Tested with 0.4 nozzle, 0.1 LH and value of 0.32 -> combined every 3 layers.
Tested with 0.4 nozzle, 0.16 LH and value of 0.32 -> combined every 2 layers.
Tested with 0.4 nozzle, 0.1LH and value of 0 -> combined every 4 layers. (ignoring this parameter and using the nozzle size as the limit - default behaviour)

Fixes #2735
Fixes #5421
Fixes #4066

Credits:

To Noisyfox for the original implementation that pointed me in the right direction where the change needed to be made
#2757

[idkjustgoogleit]

Could this also be also a percentage instead of mm?

[igiannakas]

I'll check and see what I can do...

[igiannakas]

Could this also be also a percentage instead of mm?

Done. Expressed as a % of the nozzle size used for the region.

[vovodroid]

May be it's good enough to hardcode max layer height to 65-80% of infill width (not nozzle diameter)?
I use following code in my fork:

                float w = region.config().sparse_infill_line_width.get_abs_value(nozzle_diameter);
                if (w == 0)
                    w = this->config().line_width.get_abs_value(nozzle_diameter);

                if (current_height + layer->height >= w / 1.5 + EPSILON) {

[igiannakas]

But isn’t layer adhesion mostly linked to layer height? So even say with a 0.8 line width on a 0.4 nozzle a 0.4 sparse infill layer height would still be brittle, no? Haven’t tried it but that’s my instinct.

https://help.prusa3d.com/article/layers-and-perimeters_1748#

Logic stems from here

“The layer height should be below 80% of the nozzle diameter (e.g. the maximum layer height with a 0.4 mm nozzle is about 0.32 mm). The layer height cannot be higher than the nozzle diameter, PrusaSlicer will display an error message if you try to input such a value.”

[vovodroid]

But isn’t layer adhesion mostly linked to layer height?

Sure. But sparse infill actually should be for "roof" support, not bending strength. So I guess some reasonable value could be hardcoded.

[CristianGTR97]

Great idea

[SoftFever]

Looks good
Thank you!