Specified Extrusion Multipliers  

RE: Specified Extrusion Multipliers

When you say flow ratio do you mean extrusion width ?  If so then you have to be in Advanced or Expert mode to see those options.  They are under Print Settings>Advanced and there are settings for Default, First Layer, Perimeters, External Perimeters, Infill, Solid Infill, Top Solid Infill and Support material.  As you can see the items are yellow coded which means Advanced only.  As all the items on the Advanced tab are either yellow or red you wont even see the tab if you are in Simple (green) mode.

Flow ratio in Prusa Slicer is a setting for Bridging, its located on the same Advanced tab. 

If you install a default Prusa Mk3 printer using the wizard it creates in the printer profile the custom start and end gcode, that contains a conditional for flow ratio that sets it to 0.95 (95%) if the layer height is above 0.05, otherwise it sets it to 100%  but it does that using the marlin M221 command so you could do that with any printer that supports that M code in its firmware.

RE: Specified Extrusion Multipliers

@neophyl

When I say flow ratio I mean what I say. in other words an extrusion multiplier. How much material is extruded. but not a global one like the one that exists, but one that can specifically target first layer, infill, etc. 

RE: Specified Extrusion Multipliers

Forgive me if I'm not following but that's precisely what the settings I detailed previously do.  They change the amount of plastic extruded depending on the type of extrusion being performed.  In the example above which uses a normal 0.4mm nozzle from a default prusa profile the default is set to 0.45 (along with most of them) but the support, top infill and first layer are set to extrude less plastic.  You could just as easily set the first layer to extrude more or use a % value (which I believe is based on the defined nozzle diameter).

A profile for a 0.6mm nozzle will use different values and profiles designed for vase mode printing will often contain values such as 0.8mm even for a 0.4mm nozzle.

If the amount of plastic being extruded is already controlled by the extrusion width settings then a flow ratio setting for each of them is redundant as you would setting the same thing in 2 different places.

RE: Specified Extrusion Multipliers

@neophyl

While these settings in theory could be used to the same effect, changing them to lower values adds a hefty amount of print time, where if you had a standalone value specifically for extrusion multiplier on lets say the first layer, it wouldn't add print time, but would eliminate over extrusion. 

RE: Specified Extrusion Multipliers

If I changed the first layer extrusion width from 0.42 to 0.40 it wouldn't effect the subsequent layers and so would only have a minor hit on print time.  I normally set my first layer to a slower print speed anyway so it already takes longer, I'm willing to trade that off for a more reliable first layer but that's my choice with my settings. 

With the settings available it is possible to control both the amount of plastic put down and the speed at which it puts it down for those types.  That's exactly what you wanted from my interpretation of your question.

I guess my problem is that you haven't clearly stated exactly what you are trying to achieve with a practical example that I can get my head around.  I also cant understand why if you have an alternate slicer that gives you all the settings you want you are using one that doesn't ?

RE: Specified Extrusion Multipliers

I may not be seeing what is requested, but my opinion on what to choose between extrusion width (EW) and extrusion multiplier (EM) to try to control how wide the bead being laid down would be to choose EW. Also IMHO EM should only be used to tune how the hardware extrudes to get a desired extrusion width to make up for tolerances in the hardware. The slicer will generate paths based on what the EW set to so adjacent lines will bond to each other. If you intentionally under extrude by lowering the EM you lower the adjacent line bonding and if taken to the extreme you will get gaps between adjacent lines.

Now, if you want those gaps between adjacent lines, by all means under extrude. But I don't know of a way of convincing Plicer to dynamically change EM based on feature and/or position so you may have to post-process the resultant g-code by hand or script.

RE: Specified Extrusion Multipliers

Apologies if this thread is a bit old; I searched a bit and did not see any newer posts on the topic when I searched for it looking for a similar solution.

I agree with the OP - the ability to change the extrusion multiplier for different features is different from choosing the extrusion width, and also being able to manipulate the multiplier according to feature is useful. For example, you may want to keep the multiplier lower for solid infill to keep material from building up on the nozzle, but overextrude for lower percentage single line width fill patterns to make the vertical bonds stronger. Cura has this feature and it is quite useful.

G

RE: Specified Extrusion Multipliers

The developers at Prusa rarely if ever come on this forum as it is user to user only.

To suggest a new feature this you must go to:

https://github.com/prusa3d/PrusaSlicer/issues

First search that it has not already been reported and if not click on the "New Issue" button.