Does pressure advance depend on layer height?
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I run pressure advance calibration for 0.2mm layers and got a value of 1.15 which prints well (660mm bowden and E3D 0.4mm Titan).
Now I want to print at 0.08 layer height. Is the optimal pressure advance value suppose to stay about the same or is there a formula to estimate it from the 0.2mm layers values.
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@zapta In my experience, if nothing changes which alters the viscosity of the molten filament, then the PA value remains valid. I haven't tried printing at small layer heights but I have printed complex parts with small segment lengths.
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It's my understanding that acceleration of the extruder is the only thing it takes into consideration. With thinner layers (but same X/Y speed) your extruder velocity will be lower, so if your jerk is high enough you may see a different "acceleration profile" as it were, but then pressure advance would be multiplied by whatever acceleration there is. This assumes negligible non-linear extrusion effects, or well-correct non-linear extrusion at any rate.
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My printer has 660mm bowden tube. When I run the pressure advanced calibration I got 1.15 for 0.2mm layer and 2.0 for 0.08mm layer which is quiet significant.
I am using the calibration script here https://forum.duet3d.com/topic/6698/pressure-advance-calibration/1 and look for the extrusion factor where the thickness at the middle of the slow sections equals the thickness at the middle of the fast sections. I slightly modified the script such that the base layers are always 0.2mm.
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Perhaps because the lower layer height is more squished the bulges at the end are more pronounced?
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@zapta said in Does pressure advance depend on layer height?:
My printer has 660mm bowden tube. When I run the pressure advanced calibration I got 1.15 for 0.2mm layer and 2.0 for 0.08mm layer which is quiet significant.
Those are really weird values. My HEVO didn't cross 0.8 when I was using a 800mm Bowden with lots of slop in the connections back when I just started with the printer and I've used the same script. Now it's at 0.6 with 600mm Bowden, but I had to eliminate feeder slip the brutal way.
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@edgars, can you share your config.g file? I would like to see your jerk, acceleration and related settings.
Also, what test did you use to determine the optimal pressure advance value?
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@zapta The config.g: 0_1567783590060_config_06.09.2019.g
I think I took the very same script, modified it a bit:
0_1567783937967_advance_cal.py.txtand generated these gcodes for 30-200mm/s:
0.3-0.6 PA:
2_1567783937967_0.3-0.6_30-200_D0_1.gcode
0.0-1.0 PA:
1_1567783937967_0.0-1.0_30-200_D0_1.gcodeThe printer has an E3D Volcano and double feeders which allow for higher than usual pressure, so your mileage may vary.
Check if it fits your printer before running. Mine has roughly 480x480 print bed and I offset the print to the middle.
