More strange pressure advance behaviour

OBELIKS

Check this one also, at the end: https://forum.duet3d.com/topic/6078/core-xy-movement-issues/57
He swapped M92 and M350 in config.g

deckingman

@obeliks said in More strange pressure advance behaviour:

Check this one also, at the end: https://forum.duet3d.com/topic/6078/core-xy-movement-issues/57
He swapped M92 and M350 in config.g

Thanks for trying but yes I've been trying to help that OP also so I'm well aware.

Edit. But just for the hell of it, I made those same changes (even thought it's not correct) and it didn't help my issue.

dc42

Hi Ian, I tried printing your tapered cylinder on my delta last week and again today with various pressure and advance extruder microstepping values. Even at pressure advance set to 0.4 and extruder microstepping set to 1 the XY movement is still smooth, although I can feel and hear the extruder vibrating.

[EDIT: I only tried the spiral vase version.]
[EDIT 2: I also tried with a mixing extruder configured, mix ratio 1:0.02:0.02, microstepping as low as 1:1:16. XY movement still smooth.]

So the next step is for me to replicate your configuration on my bench setup and see if I can see any jerkiness in the movement of the XY motors. But I have a feeling that you are not running very recent firmware. So please can you upgrade to firmware 2.01beta2 if you are running an older version, and verify that the problem is still there and it goes away at higher microstepping. Stay with DWC 1.20 (the latest DWC beta doesn't work properly with CoreXY) and add M564 H0 to config.g if you don't have it in there already.

PS - did the jerkiness happen at all heights of the tapered cylinder, or only in certain regions?

deckingman

@dc42

Hi David. As per post dated 14th July, I am indeed still on 1.20.1RC2 so I'll update and report back.

I can't say if the jerkiness happens at all heights. It does for the skirt and the first few layers, after which I've always aborted the print (didn't seem any point in continuing).

deckingman

Well now, it seems to be fixed

So I updated the firmware to 2.01beta2 and put extruder micro-stepping down to 16x and I cannot provoke the problem. Tried single tool, mixing tool, ratios from 0.96:0.020.02 to 0.34:0.33:0.33. Tried the tapered vases - both vase mode and 3 perimeter model. Tried the original test cylinders. These were sliced at mostly 90mm /sec and I changed the speed from 30% (30mm/sec) all the way up to 300% (theoretically 270 mm/sec but in reality limited by acceleration to somewhat less). Tried pressure advance from 0.1 to 0.5. Tried all combinations of those sometimes crazy settings and behaviour is fine and normal.

That is to say, no matter what I do, pressure advance gets applied once only at the end of each circle, instead of multiple times during the circle and there are no pauses or jerky behaviour of the head movement.

So something that changed in firmware between 1.20.1RC2 and 2.01beta has fixed it although I haven't seen anything in the release notes that would explain it. Maybe it was the change to RTOS??? Who knows? Who cares? I'm just happy it's fixed.

PS, the top layer surface finish on those test cylinders at some speed way in excess of 90mm/sec with highish pressure advance was as good as 30mm/sec - almost flawless.

dc42

Great! I'll cross that one off my list. I made some changes to the pressure advance calculations in release 1.21, so those may have fixed it.