Extrusion multiplier vs Flow  

Re: Extrusion multiplier vs Flow

Confusing...

The extrusion multiplier is used inside the Gcode generator to calculate the actual filament extrusion commands. Which are embedded in the Gcode.

If you run the same setup in your slicer and only change the extrusion multiplier
The extrusion values will change through the Gcode.

Then there is a start Gcode command in Slic3r which r3duces the flow ratio to 0.95 if the layer height is bigger than 0.05mm.

Then there is a flow option in the settings menu on the LCD.
This chang3s the same variable as the command in the start Gcode
So as I see the situation. You can either increase the extrusion multiplier in the slicer and realise for your trials. Or change the flow on the LCD.. . Or both

If you find that you need 105 percent flow. In the LCD then you should be able to raise the extrusion multiplier to 1.10 and get similar results without fiddling with the flow multiplier for every print.

Regards Joan

Re: Extrusion multiplier vs Flow

Thanks Joan.

So if I understand correctly, setting the Multiplier in the code will work and override the beginning gCode that sets it to .95. The Flow on the LCD is always multiplied by whatever is in the gCode.

So if I leave the standard 0.95 setting in the default gCode and then adjust the Flow on the LCD to 1.05, i should basically end up with 100% (1.05 * .95, yes I'm rounding). If I set the Slic3r to 0.9 extrusion multiplier and then set the LCD to 1.05 I will basically get 94.5% (1.05 * .9).

Is this right?

I was very confused the other day as I saw the LCD said 0.95 when I hadn't changed anything.

RE: Extrusion multiplier vs Flow

Sorry to respond to an old conversation but...

I would also like to know if phil's assumed calculation is correct. I'm just looking for a formula here so I can pinpoint perfect multiplier settings.

-Kevin

RE: Extrusion multiplier vs Flow

Posted by: @kevdoylejr

[...] I would also like to know if phil's assumed calculation is correct. I'm just looking for a formula here so I can pinpoint perfect multiplier settings.

Don't drive yourself nuts. Just be aware that the default Prusa printer profiles include a line in the startup gcode that tweaks the extrusion rate.

M221 S{if layer_height<0.075}100{else}95{endif}

If your layer height is < 0.075mm, it'll use 100% (of whatever you set in your slicer). If equal or higher, it will reduce it to 95%. This means the gcode is making adjustments to your settings at print time, which is frustrating when you're trying to calibrate your slicer settings. I just remove that line from the startup gcode so all of the tweaking is done in the slicer (unless I override something using the front knob).

If you search through the forum posts, you may find a very old post by Josef Prusa in which he explains they added this line as a work-around for the old Slic3r code to over-extrude at certain ranges of layer height. There's nothing overly magical about it. Just a kludge to work around an issue.

What you want to do is calibrate your slicer settings -- specifically your extrusion multiplier -- to account for small variations between filaments. Prusa has an article on one method. I use the "hollow cube" print approach myself. Whatever method you use, just do a few test prints when changing filament manufacturer or type and tweak it in your filament profile. I also recommend calibrating Linear Advance. I've got some rough notes here on my process.

RE: Extrusion multiplier vs Flow

Prusa has an article on one method. 

Unfortunatly, neither Google Chrome or IE can find the page. It is like the database is being searched, but can't find anything (wheel keeps turning)

To bad, I was looking for some more information here. For one reason or another, multiple different spools print with perfect extrusion. Then there is a new type of filament I'm testing, that loves to overextrude.

I want to be able to tweak my multiplier in  the slicer. Since it only happens to 1 type of filament.

So I disabled M221 command in the GCODE . (;M221 S{if layer_height<0.075}100{else}95{endif} ; set flow)

Then, for testing, I printed a hollow 20x20x20 cube with 0 top layers, 2 perimeters and multiplier set to 1, later again same settings but multiplier to 0.50 for testing purposes.

The result?

In the "1.0 multiplier" version, I've got 4 sides with thickness 0.91mm and visual lines of the overextruding. Checked the flow setting on the printer while it printed and it was resulting a value "100", what is correct if asking me.

In the "0.50 multiplier" version, the result was 4 sides resulting in 0.8 mm thickness. While printing I checked the flow and the machine gave me again a "100" result. I can understand this, since there was nowhere a M221 command in the gcode.

My findings are here: excluding the M221 command in the gcode, and then you can use the extrusion multiplier from the filament tab.

RE: Extrusion multiplier vs Flow

I am not a fan of the Prusa M221 command in startup gcode as it's hidden from the rest of the settings and causes confusion. I prefer to use 100% as the base extrusion rate, then calibrate the extrusion multiplier for each filament.

Be aware that adjusting the rate either using M221 or using the front knob mid-print is persistent. That rate will remain in use until you either set it back or cycle power on the printer. I added M221 S100 to my startup gcode to avoid this after a few mishaps.

FYI - that link is working for me (Chrome on Android).

RE: Extrusion multiplier vs Flow

Hey Bob,

Thanks for the reply.

1/ The link is working now. This morning they were on strike, I guess 😉

2/ I had the same idea about the setting to 100 with the M221 and adjusting with the extrrusion multiplier per filament. That's why I use the M221 in the "end code" to set the value to 100 each time a print has finished.

RE: Extrusion multiplier vs Flow

@dominiek

Would setting this multiplier at the end of gcode still be effective in the case where the print doesn’t finish normally?

-DJ 

RE: Extrusion multiplier vs Flow

Posted by: @djspathis

Would setting this multiplier at the end of gcode still be effective in the case where the print doesn’t finish normally?

No. I've gone a bit on the overkill side and reset it both in startup and end gcode.

I found that thicker layers over extrude, so have tweaked my setting in my startup gcode.

RE: Extrusion multiplier vs Flow

If you get everything else right, esp. extruded length you will find M221 S 100 will work correctly.

Here is a 0.6 mm nozzle, with extrusion width set at 0.65 mm and here is the result, M221 S100 in Custom G code.

Perfect all round.

RE: Extrusion multiplier vs Flow

I have to thank whoever resurrected this old thread- I posted a question about flow settings that has remained unanswered for the past couple of weeks.

It looks like 2 of my 3 questions have been answered, but the one remaining has to do with the flow settings during the embedded first layer cal. If I'm using, say Fillamentum ASA filament, which has an average diameter of 1.72-1.73 and adjust the first layer cal so that it looks right, how should I tweak the extrusion multiplier to match?

Main question was driven by poor adhesion for ASA on textured plate after first layer tweaks and bed leveling corrections that I thought were pretty good. Came back and had a blob of ASA wrapped around the print head, in and around wires, etc... Ripped wires off the thermistor and welded to the ASA extruder body, not to mention the fan shroud, which was the fifth I've printed and installed.

My prints are probably the worst possible for the Pinda probe sag... try to maximize space utilization on the plate and 75% of the printing is at 3mm and less height. I've since resorted to dissolving some glue stick in IPA and just wiping it on between prints. I'm not a fan of the inconsistent depression fills when I just apply the stick.

In the middle of the MK3S rebuild now- glad I have the two minis to print parts.

Steve

RE: Extrusion multiplier vs Flow

If anyone stumbles across this thread in their own troubleshooting, I thought I would add my experience with my Mini.

The current stock "Start G-code" (2.3.0) contains this line for the flow rate.

M221 S95 ; set flow

This works perfectly fine with Prusament which has an Extrusion Multiplier of 1, but everything else I've sent through the extruder ends up under extruded.

So after printing multiple calibration cubes using varying settings with all my different filaments, I came to the following conclusion.

• Prusament
  • Extrusion Multiplier = 1
  • Calculation is ( S95 * 1 = 95% )
• Everything Else (Overture PLA/PETG, Hatchbox PLA in my case)
  • Extrusion Multiplier = 1.05 
  • Calculation is ( S95 * 1.05 = 100% )

So it would seem that the default settings seem to be driven by how Prusament performs. However, Prusament appears to be the exception and not the standard in my experience.

In theory, and I may make this change anyway, you could change M221 to S100 and then just modify your Prusament filaments to a 0.95 extrusion multiplier to achieve the same as above. This might be more advantageous if you rarely or never use Prusament.

RE: Extrusion multiplier vs Flow

I've added some detailed notes on this topic to my pages. 

RE: Extrusion multiplier vs Flow

I have read this and think there is a confusion about flow rate (firmware set via m221) and extrusion multiplier from filament tab. These are two different things. One is the overall parameter and the other one filament specific. So I assume the conclusion before (0.95 x Extrusion Multiplier from filament Tab) is correct.

RE:

For what its worth on this old thread, the default printer presets in PrusaSlicer 2.6.0 for the MK3S and MK2.5S are inconsistent with each other regarding this M221 setting. The two printers have identical extruders, which I think should imply that if one needs multiplier tweaking so would the other. I happen to have and use one of each.

The MK3S presets include "M221 S{if layer_height<0.075}100{else}95{endif}" which caused me many First Layer failures: under extrusion and the filament wouldn't stick. I learned to wait until the auto home finished, go to Tune real fast, and set the Flow to 100. It took me quite a while to track down WHY this happens only on my MK3S. The MK2.5S presets don't have the M221, and now I have it fixed in my user presets.

RE: Extrusion multiplier vs Flow

is there a variable name we can use for the extrusion multiplier like we do with the first_layer_temp? something like [Extrusion_Multiplier]?.. i was trying to change that M221 line to something like:
M221 S{if layer_height<0.075}100{else}[extrusion_multiplier] * 100{endif}

RE: Extrusion multiplier vs Flow

Command which I implemented is 

M221 S{if layer_height<0.075}100{else extrusion_multiplier[current_extruder]*100 endif}