Extrusion tuning: Filament diameter vs extrusion multiplier
 
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Extrusion tuning: Filament diameter vs extrusion multiplier  

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stahlfabrik
(@stahlfabrik)
Honorable Member
Extrusion tuning: Filament diameter vs extrusion multiplier

Hi,

I wonder how to best dial in the extrusion on the MK3.

As far as I understand, the Extruder steps do not have to be touched, because the bond tech setup does extrude 10cm when you tell it to do that. I tested it once a few months ago and that was my take away - is that correct? Or should I revisit that?

But what I really want to talk about is the filament diameter and the extrusion multiplier that I can set in Slic3r. Because with default values my prints tend to come out over extruded. So should I measure the filament and dial that measured value into Slic3r? And then print a extrusion test and measure it? Or is it the same effect (after all) to NOT change filament diameter, print a extrusion test and measure it? In both cases, I would measure and deduce a extrusion multiplier from it. All I wonder, what is the difference? Is taking the true filament diameter (which might even change throughout the print) into the slicer good in some aspect (Like of course better print quality), or would exactly the same print quality be achieved by only tuning the extrusion multiplier?

Best regards,
Stahlfabrik

Posted : 20/04/2018 2:08 pm
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ibn
 ibn
(@ibn)
Trusted Member
Re: Extrusion tuning: Filament diameter vs extrusion multiplier

As far as I know that changing steps/mm, extrusion multiplier or cross sectional area of the filament (not diameter) all has the same linear effect so it doesn't really matter which ones we change.

The steps per millimeter extruded filament may change slightly with the filament and/or tightness of the extruder springs (the deeper the bondtech gears grab into the filament the smaller their effective radius becomes), whenever I tried it with the default settings it was so close to perfect I never bothered with adjusting.

So far I only used brand Filament and the diameter was never too far off 1,75 mm, that's a value I would adjust in the slicer though to get a better feel for my extrusion multiplier. Because the effect of diameter in cross sectional area is to the power of two a slight difference has a surprisingly big effect. For 1,75 mm filament a change of 0,05 mm equals about 5% change in cross sectional area.

If the above are in the ballpark the value I do adjust is the extrusion multiplier. For this I usually use a hollow cube (no infill, no top layer) with one or two perimeters, measure it's thickness and adjust the extrusion multiplier accordingly. If the wall thickness is on the numbers the often mentioned extrusion test ( https://www.thingiverse.com/thing:1622868 ) fits very nicely too.
For me the quality of a top surface layer serves more as a plausability check, I'm not experienced enough to set the extrusion multiplier just by top layer quality.

The above seems to work well for the extrusion multiplier, for adjusting K-Factor and retraction I'm still practicing

Posted : 24/04/2018 5:20 pm
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