Why not a first layer (only) extrusion multiplier setting?

[rw3iss]

I know I'm going to hear some pushback from this, but I'll argue it.

I know the idea is that we are supposed to set the (overall) extrusion multiplier, and then just set the extrusion width for the first layer, and adjust the first-layer/z-index height from the machine to get a better "push"+adhesion for the first layer...

This is alright, but most of the time I just want to extrude a lot more on the first layer only, to both guarantee bed adhesion, and also get a better bottom surface finish on a textured bed. Cura has this feature, and the prints stick and come out a lot better! Besides that, we shouldn't have to adjust three settings (extrusion multiplier, first layer width, and the z-height on the machine), for a simple setting to just want to get more plastic out of the first layer only. It's also just a nice feature to have in general, I think, and I see other people asking for it.

Would it be possible to add such a setting? Or otherwise maybe there is some way to manually add the G-CODE, I'm sure... and then change it again after the first layer. Is there a specific G-Code command that I can search for to check where the z-height changes after the first layer, and then insert the code to change the multiplier there?

Also, it's not clear how the extrustion width is actually derived from the nozzle diameter. Please see the picture:

Regardless of clarifying this area, I still think it would be beneficial to have a custom first-layer extrusion multiplier setting! Please :-)

[dw-0]

Or otherwise maybe there is some way to manually add the G-CODE, I'm sure... and then change it again after the first layer.

Depending on you firmware, M221 lets you set the flow percentage.
With a simple condition you can check for the first layer. An example for changing the flow to 110% only for the first layer and reset it back to 100% as soon as the second layer starts can look like this:

;Changes the flow to 110% only for the first layer
;and reverts back to 100% on the second layer
{if layer_num == 0}M221 S110
{elsif layer_num == 1}M221 S100
{endif}

Also, it's not clear how the extrustion width is actually derived from the nozzle diameter.

Given a nozzle diameter of 0.4mm
extrusion width = 1.125 x nozzle diameter = 1.125 x 0.4mm = 0.45mm

Personally, what i find more confusing and not clear, is the computation over layer height if expressed as percentage.

[rw3iss]

Righteous! Thank you for the G-Code logic, @th33xitus!
Your logic regarding the width makes sense. I think I was confused because I thought the sentence I highlighted was referring to the "if not 0" case... where it would use the set value in that field, but re-reading it it's actually saying "if default isn't set AND this value isn't set... then it uses nozzle diameter x1.125". Anyway, thanks.

Also agree... overall this menu is a little confusing. The tooltips can be derived if reading very carefully, but I'd rather just see the ability to set the value to something, and then actually show what the value would be to the right (ie. a read-label of the calculated value), just to avoid any confusion for the user, so they can understand it better themselves!

[fe60]

One of the options requested in #3635 a year ago.

[gitcnd]

This setting MAKES NO SENSE. Language is important guys.

If I'm printing (say) a 4mm wide object, with a 0.4mm wide extrusion width, that takes 10 lines.
If I set the "extrusion multiplier" to 200%, that means that my lines are now theoretically 0.8mm wide (like I said LANGUAGE), so I only need 5 lines to print that 4mm wide object.

In either case, the total amount of plastic extruded is EXACTLY THE SAME.

If the intent of this option is to extrude additional plastic for the first layer, then the name of the option should be "extrusion multiplier".

If the intent of this option is to extrude the EXACT same amount of plastic, with fewer overall lines, then the wording of the option as it stands is OK (although I can't imagine any time anyone would want this), however, we ALSO now need ANOTHER option to set our first layer extrusion multiplier...

It's unclear which meaning is in use here, however, I just tried 100% and 200% on this setting, and in both cases my first layer extruded lines are not touching each other, so something definitely seems wrong here.

[neophyl]

You are using percentages. When expressed as a percentage then the line width is NOT based on the nozzle size but on the configured LAYER HEIGHT. As alluded to by th33xitus.

Its one of the most counter intuitive settings in there but its one of those historical ones that if changed can potentially break existing profiles so no one wants to touch it. Which is why I always set specific width values and do not use percentages in PS.