Nonlinear extrusion
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I have been using nonlinear extrusion for years with mixed results. I have gotten setups dialed in better than running without it but it always felt like it wasn't consistent.
I have been using this calculator.I tried setting it up doing static extrusion tests marking 100mm on the filament then extruding 100mm.
I found a better method has been to see where a print is under/over extruding then tweak those tables.I started to feel like sometimes trying to increase extrusion by using a lower number at higher flow rates actually decreased the flow.
Tonight I think I finally confirmed this with the volumetric flow readout on the Duet web display. I was printing something that should have been 5mm3/s.
I started with a moderately aggressive NE number. Like say 100 at 0mm3/s and 78 at 6mm3/s (this is for TPU BTW).
The display showed something like 5.1mm3/s
So I went to an aggressive number. Something like 68 at 6mm3/s and the number Duet was reporting went down to 5mm3/s.
So then I clicked through the history and started selecting various ones I had tried before and finally found one that bumped it up to 5.3mm3/s. This was a less extreme ratio than at least one but I think several of the others I tried. Reverse engineering the numbers I think around 72 at 6mm3/s.I can test this more soon but it makes me think maybe this isn't working like it should and maybe that is why it has been such a struggle for me to dial in these settings.
All of the threads I have found on this are either very old and include these two calculators often discussed, or are newer and really don't have much information.
I will admit that the math goes a little beyond me so I need a calculator or an easy way for me to get from seeing under extrusion at a flow rate and understanding how to change values to address it.
One thing that would be amazing is if there was actually an interface in the web interface where you could just enter values to create a curve then it just does the math in the background. Even better if there was a way to link it to slicer profiles or something but that's probably getting complicated unless the slicers worked to integrate something there too IDK.Anyway I love the concept and when it works it is amazing but it feels about like 50% science and 50% pulling the lever on a slot machine. Or maybe I'm just doing it totally wrong.
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@yoshimitsuspeed while I can’t really help with tuning of nonlinear extrusion, as I haven’t used it, other than suggesting reading other threads on it, which you have already done. It does seem odd that the volumetric flow rate is reporting incorrectly. @dc42 would need to take a look at that. What firmware version are you using?
It does seem like a better idea to adjust temperature to account for high rates of extrusion. There’s a recent thread on this, see https://forum.duet3d.com/topic/36364/feature-adaptive-feedforward-temperature-setpoint
Ian
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Haha I made the suggestion ages ago to adjust heat based on volumetric flow rate here and in Prusa Slicer forums and more people than not basically told me I was being stupid lol. I will check it out as that would be huge especially with filaments like TPU which I print with a lot.
I think nonlinear extrusion is still valuable especially with TPU.
I am currently running 3.5 RC2 but I have had frustrations with nonlinear extrusion for ages and several different versions. -
@yoshimitsuspeed said in Nonlinear extrusion:
Haha I made the suggestion ages ago to adjust heat based on volumetric flow rate here and in Prusa Slicer forums and more people than not basically told me I was being stupid lol.
Yes, you did! https://forum.duet3d.com/topic/32930/volumetric-temp-change
I don't think forum members here laughed at you. There was concern about how quickly the hot end could heat up and cool down.And it seems someone did exactly what I suggested: https://forum.duet3d.com/post/319377
I'd think the best way to do what you want is to write a slicer post processing script to identify fast and slow printing, and change the temperature accordingly. You can even write it with look ahead to change temperature in advance; RRF is unlikely to be able to look far enough ahead to do this.
Ian
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The volumetric flow rate shown by DWC is the commanded flow rate before pressure advance or nonlinear extrusion is applied. Pressure advance only changes the commanded flow rate during acceleration and deceleration. For the steady speed part of a long move the volumetric flow rate should be the same as the value implied by the GCode command and the nozzle diameter, provided that the actual speed matches the requested speed.
One way to check the calibration of nonlinear extrusion is to use the Duet3D Magnetic Filament Monitor (or the MFM add on to the Roto Tool board) to compare actual vs commanded extrusion during a sequence of long straight moves executed at various speeds and corresponding flow rates.
