Pressure Advance with S2.0 ??

LichtiMC · 15 Mar 2020, 03:08

I have a bowden extruder with the tube about 400mm long.
So it's suggested to use M572 D0 S0.1 as pressure advance value.

I did the testprint as instructed on the wiki pake about pressure advance and did'nt get a result when playing with values from 0.1 - 1.

Then just for fun I tried to use 2.0 and got a beautiful finished z-seam.
Of course the printer is extremely slow as it's written in the wiki.

Does anybody have a clue what's going on here? Is there another incorrectly set option that could cause this situation to occur?

Thank you very much!

bot · 15 Mar 2020, 03:12

@LichtiMC
The slowness is due to your extruder jerk limit. For PA to work, the extruder needs to instantly jump ahead. If it's limited by the jerk to an amount lower than it wants to due to the PA adjustment, then it will slow down the acceleration of the X/Y axes to accomodate the lower jerk limit. IE, it forces the toolpath/PA combo to not require more E jerk than is set in M566.

LichtiMC · 15 Mar 2020, 11:46

Thank you for your answer.

So you think a pa-value of S2.0 is normal even though the instructions imply that it should work with 0.1 for my tube length?

I have an CoreXY Printer and following e-jerk values activated: M566 X900.00 Y900.00 Z12.00 E120.00
How would I have to adjust the values to get more "normal" speeds?

dc42 · 15 Mar 2020, 13:38

@LichtiMC said in Pressure Advance with S2.0 ??:

So you think a pa-value of S2.0 is normal even though the instructions imply that it should work with 0.1 for my tube length?

I suspect the optimum for that tube length is longer than that, perhaps 0.2 or 0.3.

I have an CoreXY Printer and following e-jerk values activated: M566 X900.00 Y900.00 Z12.00 E120.00
How would I have to adjust the values to get more "normal" speeds?

Increase that E parameter. I use 600 on my delta with Bondtech extruder and 600mm Bowden tube. I could probably use a higher value.

Phaedrux · 15 Mar 2020, 18:20

Have you seen this yet? https://duet3d.dozuki.com/Wiki/Pressure_advance?revisionid=HEAD#Section_How_much_pressure_advance_to_use

LichtiMC · 15 Mar 2020, 23:17

Thank you for your answers. I will definitely try the suggestions and reply, but for now I have to solve another issue first:
https://forum.duet3d.com/topic/14954/volumetric-extrusion-massive-overextrusion