[QUESTION] LIN_ADVANCE 1.5 -- extruder rattles *a lot*.

[Artem-B]

Description

I'm trying to enable LIN_ADVANCE on bugfix-2.0.x branch on my CR-10s + Cohesion 3d remix board (smoothieboard variant). As soon as LIN_ADVANCE is enabled extruder starts rattling. X and Y seem to start jerking, too, but it's hard to tell with all the noise the extruder motor is making.

I've checked step/dir signals on the extruder and it confirmed that it frequently changes motor direction

• ~20-70 ms worth of forward progress with about evenly spaced pulses.
• ~10-50 ms retraction
• repeat

Rattling happens regardless of what I print. Even when printing LIN_ADVANCE calibration pattern extruder starts rattling as soon as LIN_ADVANCE is enabled.

Despite the noise the printer is printing OK. At least, I don't see anything obviously wrong with the print, but the noise is rather bad. It's way worse when I had LIN_ADVANCE 1.0 working on the same printer. With 1.0 extruder was making 'tat-tat-tat-tat' noises. Now it's 'drrrrrrrrrrrr'.

I'm not quite sure whether that's working as intended (on close examination of the result there is a slight improvement in print quality), whether it's a problem with my config, or if it's something unexpected in LIN_ADVANCE implementation.

Steps to Reproduce

1. bugfix-2.0.x branch (as of March 30th)
2. start printing
3. M900 K0.6 (best value on calibration test print for my CR-10s with ~400mm long bowden)
4. enjoy the noise!

Expected behavior: [What you expect to happen] LIN_ADVANCE 1.5 is supposed to ensure a smooth extruder movement without rattling

Actual behavior: [What actually happens] Instead, the smooth movement with no retractions turns into constant back-and-forth.

Additional Information

Here is the album with the videos and oscilloscope shots demonstrating the problem: https://photos.app.goo.gl/l8hzKHgBgaR0dw5I2 This is what is the extruder step(yellow)/dir(blue) signals look with LIN_ADVANCE disabled.

Here's what I get with LIN_ADVANCE enabled:

Marlin config files: Marlin-configs.zip G-code for the test cube I've been printing: xyzCalibration_cube-gcode.zip

[boelle]

closing, the discussion can continue on discord

Marlin Discord server. Join link: https://discord.gg/n5NJ59y

or here even if its closed

[yeowjoon99]

It doesn't only occur on TMC2208's though. My extruder uses an LV8729 and I have the exact same issue as @Snagi0.

Straight lines print perfectly fine but curves are EXTREMELY jerky on the extruder.

[hazedav]

Hello, I can confirm that I also have same problem with TMC 2209 (board SKR mini E3) on my ender 3.

I also have LIN_ADVANCE extruder jerky/jittering with TMC 2209 (board SKR mini E3) on my ender 3. Marlin 2.0-bugfix (2.0.3). I notice this issue is closed, but it still seems like a thing.

Please advise.

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