Flow Tune vs Extrusion Multiplier  

Re: Flow Tune vs Extrusion Multiplier

hi jonnie. first thanks for that link to your little test (uploaded at thingiverse) for checking the extrusion multiplier !
then: i would have expected the same as you, that is to say that both methods should deliver the same result.

i'm going to test it with my slicer of choice (s3d) this weekend.

maybe some other settings inside the slicer (such as extrusion widths) interfere with the overall extrusion multiplier, set in the filament tab.

Re: Flow Tune vs Extrusion Multiplier

first thanks for that link to your little test (uploaded at thingiverse) for checking the extrusion multiplier !
then: i would have expected the same as you, that is to say that both methods should deliver the same result.
Hi, Jeff, and thanks for the reply. I would not like to take credits for the part fitting test, since that is just a remix of an existing model- I just made a thinner version for faster printing.

Re: Flow Tune vs Extrusion Multiplier

thanks anyway 😎

but an effect that i described here has to be considered as well, when you try to find the correct extrusion factor with such a method.

so even if the extrusion value is correct, it is very likely that the parts don't match exactly.
why ? because you'll always have a tiny clearance in the positioning of the printbed. so even if the thickness of the walls is correct, you'll "measure" a thicker print as expected, because the positioning clearance of the layers stacked upon each other will increase the width/diameter of the printed part.

hope i described it good enough to be understood.... otherwise i need to make a diagram.

Re: Flow Tune vs Extrusion Multiplier

but an effect that i described here has to be considered as well, when you try to find the correct extrusion factor with such a method.

Ok, I pretty much get it. That's why we have the XY Size Compensation to fix it, even though the Extrusion Multiplier was always enough for me. I don't want to go too much off-topic, because I would still like to get to the answer to the first question. 🙂

Re: Flow Tune vs Extrusion Multiplier

This is a rather interesting query, although not one I have concerned myself with, but something to consider.

I have a GCode file which contains a lot of this:

G1 X148.412 Y47.071 E0.00125
G1 X148.406 Y47.048 E0.00125
G1 X148.391 Y46.899 E0.00791
G1 X148.372 Y46.859 E0.00233
G1 X148.332 Y46.839 E0.00234
G1 X148.179 Y46.822 E0.00808
G1 X148.156 Y46.815 E0.00131
G1 X148.136 Y46.799 E0.00132
G1 X147.353 Y45.874 E0.06379
G1 X147.071 Y45.484 E0.02538
G1 X147.056 Y45.164 E0.01689
G1 X147.047 Y45.134 E0.00164
G1 X147.026 Y45.111 E0.00165

Notice the low E values.

One step on the extruder motor will generate an extrusion of a little over 6 microns, but the generated code requires extrusions of significantly less than one step. I really do not know how the printer will handle this and certainly doing a 1% flow tweak in the slicer will make no difference here.

The other thought is that I am told the relative extruder values are actually totalled into an absolute value contained in a 32-bit float. The precision here is 7 significant digits. The resolution will therefore reduce by a factor of 10 after 1, 10, 100, 1000 etc millimeters have been extruded unless the stored value is reset (G92 E0).

Basically after 1 metre of filament has been printed, extrusion values will be truncated to 3 decimal places and after 10 metres, a minimum extrusion of 10 microns will be required to extrude anything. Then there's the longer prints of over 100 metres (yes, I have) when a minimum extrusion of 100 microns will come into play.

Moral of this: Reset the counter regularly... Maybe every layer?

Apologies if this is a little off-topic, but it may go some way to explaining the original query.

Peter