New beta firmware 1.20.1RC2 and DuetWiFiServer 1.20+1
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Do you by any chance have any pics of with and without?
Sorry, no.
To be honest, I don't think there's going to be much visible differences because we're only talking about a few percent here and there. Having said that, I do think that it's worth using because now I know that for any extrusion rate up to the point at which it starts skipping I can be reasonably confident that it will print the amount of plastic demanded by the gcode. Whereas, before, I was getting -10% at the high rates.
That's a shame (no pics I mean).
I'm a bit confused though. You said in a post above that you were running 95% extrusion on the first layer but 104% on subsequent layers and that now you use 100% throughout. The 104% I can understand because it indicates that you were seeing some under extrusion issue, presumably caused by slippage and for which you have now compensated a different way. It's the first layer that I'm trying to get my head around. It would indicate that you were seeing 5% over extrusion before, because you were using 95% extrusion multiplier. Yet you've added a positive compensation plus taken out the 5% negative compensation. Assuming you print the first layer at half speed of other layers, then the slippage compensation would be around 2% so you must be laying down 7% more filament on the first layer than you were before, which ought to be hugely noticeable. It would on my machine anyway. Even with no slippage compensation, changing the extrusion multiplier from 95% to 100% is a pretty big step. Something very odd going on….
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Look, it's simple. Before I started using this new feature, I noticed that at my typical infill/skin speed I was getting underextrusion. So I upped the steps/mm for the extruder to 104% but then because I print my first layer walls really slow (so little underextrusion was occurring), I was then getting fat lines. So in the slicer I reduced the first layer extrusion to 95% to compensate. This way I was getting closer to 100% for all layers. But it was a gross simplification. The non-linear extrusion provides a much more accurate means reducing the effect of feedrate changes on extruded volume.
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Hi David, I am now trying out M592 on my Kossel XL which is fitted with a e3d v6 and a flex3drive extruder. Filament is PETG at 240C. I'm getting very odd results:
mm/s A0 B0 A0.015 B0.0012 1 52.5 52 2 51 50.5 3 50 48 4 47 44 5 44 38The larger I make A or B, the worse it gets!
I am not perceiving any extruder skipping or other odd noises.
The flex3drive extruder uses a lot of gearing so it's running at around 2250 steps/mm with the stepper set to 8 microsteps.
Any thoughts?
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Look, it's simple. Before I started using this new feature, I noticed that at my typical infill/skin speed I was getting underextrusion. So I upped the steps/mm for the extruder to 104% but then because I print my first layer walls really slow (so little underextrusion was occurring), I was then getting fat lines. So in the slicer I reduced the first layer extrusion to 95% to compensate. This way I was getting closer to 100% for all layers. But it was a gross simplification. The non-linear extrusion provides a much more accurate means reducing the effect of feedrate changes on extruded volume.
Ahh, sorry. But you didn't make any mention in your earlier post that you'd changed the extruder steps per mm at the same time, hence the reason I was confused. So your 95% for the first layer was actually 95% of 104% which makes a lot more sense.
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Hi David, I am now trying out M592 on my Kossel XL which is fitted with a e3d v6 and a flex3drive extruder. Filament is PETG at 240C. I'm getting very odd results:
mm/s A0 B0 A0.015 B0.0012 1 52.5 52 2 51 50.5 3 50 48 4 47 44 5 44 38The larger I make A or B, the worse it gets!
I am not perceiving any extruder skipping or other odd noises.
The flex3drive extruder uses a lot of gearing so it's running at around 2250 steps/mm with the stepper set to 8 microsteps.
Any thoughts?
Yes, that looks odd.
1. If you revert to A=0 B=0, does it revert to the speeds you measured before at A0 B0?
2. If you send M592 D0 does it respond with the values you configured, and a sensible value for L?
3. Please confirm that when doing these tests, you are doing head movement as well as extrusion.
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Yes to all 3 of your questions.
I can't fathom what's going on here. I'm getting some variation in the results from run to run.
A question: do the A and B get scaled by the steps/mm value for the extruder? i.e. if the steps/mm value is large will that mean that the values for A and B will be larger compared to the values used for an extruder with lower steps/mm?
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The calculation it does is:
const float dv = dda.directionVector[drive]; float stepsPerMm = reprap.GetPlatform().DriveStepsPerUnit(drive) * fabsf(dv); const size_t extruder = drive - reprap.GetGCodes().GetTotalAxes(); #if NONLINEAR_EXTRUSION if (dda.isPrintingMove) { float a, b, limit; if (reprap.GetPlatform().GetExtrusionCoefficients(extruder, a, b, limit)) { const float averageExtrusionSpeed = (dda.totalDistance * dv * DDA::stepClockRate)/dda.clocksNeeded; stepsPerMm *= 1.0 + min<float>((averageExtrusionSpeed * a) + (averageExtrusionSpeed * averageExtrusionSpeed * b), limit); } } #endif</float>Let me know if you spot a problem with it. dda.totalDistance is always positive, and dda.directionVector[drive] will be positive if a positive amount of extrusion is commanded. I guess the calulation would go wrong if you did a simultaneous movement and retraction.
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I did look at that code but I'm not familiar with the RRF source so I can only guess as to how it is working. I do agree that the calculation code looks like it is doing the right thing.
I will continue to play with my XL - let's assume that my odd numbers above are due to just clumsiness on my part. I'll get back when I have done more testing and have come to any kind of conclusion.
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I'm not very familiar with C++ but should't a, b and limit be pass by reference rather than pass by value?
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Passing them by value is best here because their values are read but not changed.
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Passing them by value is best here because their values are read but not changed.
Yes, I see, but are the variables initialized right here? My guess is that their values is supposed to be set in these two statements.
a, b and limit are passed by value here and not by reference. My guess is that the GetExtrusionCoefficients() method expects a pointer
to be able to write the values into the variables, like this:float a, b, limit; if (reprap.GetPlatform().GetExtrusionCoefficients(extruder, &a, &b, &limit)) -
I'm sorry, I forgot what that bit of code looked like. The a, b and limit parameters of function GetExtrusionCoefficients are already passed by reference, because they are declared as reference parameters in the declaration of GetExtrusionCoefficients. This is a C++ feature not available in C.
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Hi David, as I said, I'm not familiar with the RRF code so these may be dumb questions but in this code snippet, why are you multiplying totalDistance by dv and not fabsf(dv) and why do that multiply at all? Isn't dv a distance also?
const float averageExtrusionSpeed = (dda.totalDistance * dv * DDA::stepClockRate)/dda.clocksNeeded;
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Variable dv is the proportion of totalDistance that applies to the current drive, that's why totalDistance is multiplied by it. It shouldn't matter whether we multiply by dv or fabsf(dv) because nonlinear extrusion is only applied to extruding moves, for which dv is positive.
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Understood - thanks.
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@dc42
May I ask what development IDE you are using, Arduino or Atmel Studio (or other)? -
@dc42
May I ask what development IDE you are using, Arduino or Atmel Studio (or other)?We use Eclipse, see the BuildInstructions.md file in github.
Arduino is great for getting novices into programming microcontrollers, but truly awful for large scale firmware development. Atmel Studio is OK and I use it for the IR sensor and filament sensor firmware, but it offends those who think that only open source tools should be used or who want to develop under Linux.
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I use VisualMicro - Its an add-on to Visual Studio that enables to program and upload code for Arduino.
I found it a very good environment for programming. -
I'm familiar with it. I just can't come to terms with Atmel Studio. Professionally I use a derivative of Eclipse; Atollic True Studio which is hard to beat feature-wise.
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Hi David, I think I have discovered why I am seeing underextrusion when I use M592 on my Kossel XL fitted with a flex3drive extruder. With A and B set to 0, the x/y motion and the extruder activity start/stop at the same time (as close as I can tell by eye/ear). When I set non-zero values (e.g A=0.015 and B=0.0012) I notice that the extruder stops before the x/y movement stops. The faster the feedrate, the more obvious the gap becomes.
Here's the relevant config lines:
[[language]] M350 I1 X16 Y16 Z16 E16 ; all axes use x16 microstepping with interpolation (steps/mm will get adjusted automatically) M92 X160 Y160 Z160 ; Set axis steps/mm (20 tooth pulleys, 0.9deg/step motors) M906 X1000 Y1000 Z1000 E1000 I60 ; Set motor currents (mA) M201 X3000 Y3000 Z3000 E400 ; Accelerations (mm/s^2) M203 X18000 Y18000 Z18000 E1200 ; Maximum speeds (mm/min) M566 X300 Y300 Z300 E10 ; Maximum instant speed changes M92 E4320 ; Set extruder steps per mm (flex3drive)
