Duet 3 3.2 Beta2 jerking motion

  • There comes a time with printing that you can't identify whether a problem is

    A : You
    B : The machine
    C : The Slicer / Gcode
    D : The Filament in use
    E : The day of the week

    You get the picture here I hope.

    I built a CoreXY based on the highest possible grade of everything, including linear rails, I drive it with a Duet 3. Enough background .... needless to say I have already eliminated the above list.

    Recently I've encountered some real wierd issues, all since rolling into 3.2 Beta. I had a strange low frequency ripple 'wavy line' in vertical surfaces that was 10 to 12mm peak to peak, it was totally vertical and not skewed in any way although it was very very slight and you needed a critical eye to spot it (the camera saw it first - I didn't).

    Every now and then the print head jerks violently almost like it had been snagged on something, I watched it, it wasn't, no belts were snagged, nothing was catching on the print, no reason for such a violent jolt - and thats what it is a jolt like it releases pressure or jumps back and forth really quickly, it is a very audible 'thud'. It doesn't happen in consistent places and sometimes is more violent than others and is so fast that I sure as heck can't spot exactly what is going on.

    I've spent a lot of days trying to figure this and ultimately rolled back firmware from 3.2 beta to 3.1.1 - what do ya now - the problems went away - all of them. There is no mechanical or other issue here - it is 100% been introduced in the code some place. But how to track down what it is ?

  • @Garfield

    Well beta code is expected to behave oddly at times - otherwise it wouldn't be beta would it. 😉

    I waited on the move from v2 to v3 until dc42, when asked, felt comfortable saying that 3.1.1 was good.


  • A little obvious - I kind of know this - I run beta on purpose in the hope that issues found may assist the team resolve. I'm not asking for a fix hence the FYI - but I am making those that can fix aware so it doesn't end up in a release version.

    This is an FYI. Partly in the hope that somebody with a better understanding of the code than me may have ideas that can be explored to detect whatever 'this' is or may be.

  • Moderator

    Moved to the beta firmware forum.

    Would you be able to share your config.g?

    Are you using the Duet 3 in standalone or SBC connected mode?

    Can you provide an example of the ripple you mention?

    Do you have an example gcode that was able to provoke the violent jolt?

    Reporting a problem is helpful, but the more details the better.

  • I have experienced this exact behavior. The print head jerks, almost as if it's skipping a step multiple times mid-print. I am running a duet 2 with SBC on a corexy machine with rrf 3.2-b2 as well.

  • administrators

    @Garfield, are you running your Duet 3 with or without attached SBC?

  • Duet3, attached SBC.

    All updates are done via the console of the SBC.

    I've attached the config.g but I don't think it adds much - this problem does not exist on 3.1.1 with the exact same file. I verified this behaviour by printing the exact same test piece using the exact same gcode. 3.1.1 does not demonstrate the behaviour.

    I didn't keep any pictures of the ripple - I will have to reproduce - I didn't think this was anything other than my problem - reverting the firmware was a last resort, I wasn't expecting the problem to go away.

    The test model gcode is too large to upload uncompressed. It is essentially a 5mm thick box, 75mm sides with a 75mm radius on one corner. Be aware though that this prints fine on 3.1.1.

    Be aware - this is a gcode file that has been zipped - the extension should be .zip but I couldn't upload that.

    wall test.doc

  • I'm going to set up and try to run without the SBC (never done this so result could take a while)

  • administrators

    There are some known issues with Beta2 used with SBC. I suggest you revert to Beta1 until Beta3 is available.

  • Appreciated Dave, I was about to report but have refrained since doing so would have been premature - and the kiss of death.

    So far running direct with no SBC and 3.2 b 2 I've had a print running 30 mins or so with zero issues so far.

    If you need me to do any testing let me know. I've created a completely new SD card to run local and can easily pop the Pi back on.

  • Said it was the kiss of death ....

    So no jolts or odd behaviour - except now the print failed 1hr 14 into the print with Error 1 - Cannot read file.

    File reads fine via the Duet GUI, can be downloaded, edited, viewed to the end etc etc
    File reads fine with the SD card on the PC - scanned with notepad++ - no defects in file -

    I will try again and see if it chokes at the same point.

  • Was just a glitch - file has printed fine now for hours ... all print defects are gone, the jolts are gone with the Pi removed from the equation.

  • Moderator

    @Garfield said in Duet 3 3.2 Beta2 jerking motion:

    the jolts are gone with the Pi removed from the equation.

    Thanks for the confirmation.

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