Interestingly I also save some gripes with PA in my machine (Delta with flying extruder).
I'm seeing people using 3k jerk on E but if I do that I get almost the same problems as the OP.
- Genuine BMG (also tested with a TL clone)
- Moons' 1.8deg Pancake (same behaviour with the 35mm stock motor that came with the machine)
- 10cm Bowden @ 0.15 PA / 30cm Bowden @ 0.36 PA
- retraction down to 0.75mm@45mms (zero stringing with the PA values mentioned above)
- E3D Volcano, 0.4mm Nozzle
I get good extrusion with 300 E jerk up to 120mms, okay-ish at 600 E jerk if I don't print above 60mms and massive underextrusion and blobbing at 3k E jerk no matter the speed (I get holes on the first layer at 15mms..).
Extrusion looks fine when I turn PA off (yeah, I get over extrusion at layer changed and corners, but no underextrusion)
I had a strange problem a while ago with PA where it stopped extruding completely (filament went back and forth, but not enough to actually extrude). Turns out: this happens with E Jerk 3k, XY Jerk 3k, 9k accel, > 140mms print speed and > 0.3PA, Retraction was at 2mm or so.. I gave up on finding the exact reason after burning through almost half a spool of filament and countless hours, but it went away as soon as I started to either: print slow (< 100mms) or turn XY and E jerk down to 300ish - or turn down acceleration to ridiculously low numbers (< 1k). In the end I think it boils down to cornering speed or E jerk (which also limits cornering speed wenn low enough).
From what I understand is: shouldn't PA do less instead of more when cornering speed increases? I would understand it at high accel and low jerk, but 9k acc/3k jerk on XY at 100mms shouldn't end up in retracting more than extruding with PA on - should it?
Is it somehow possible to keep PA from retracting at all or at least set a limit?
I also don't understand how people can run 3k jerk on E with a BMG. Neither my original, nor my TL clone can handle more than around 1.5k without leaving gaps
RRF 3.01 RC15 (? latest, but it's been like this at least all of RC 3.01, didn't use PA when I was on 2.x).
I'll post some pics tomorrow.
@NexxCat you're the only one besides me that I know of that uses PA with a similar setup and similar values and also uses a rather low E jerk of 600. Is this due to the same reason I mentioned above?