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Extruder doesn't move when linear advance is activated

CarlJonasCarlJonas
in Questions & Answers
Hi,

I'm experimenting with the linear advance feature. When i activated the linear advance and set a K value the extruder doesn't move anymore. Is there a manual how to set up linear advance?

Best Regards

Comments

  • RepetierRepetier
    K is the quadratic term, bette rnot set this and leave it to 0. Linear advance is set with L term. 40 for direct extruder is a good start.
  • CarlJonasCarlJonas
    thx
  • CarlJonasCarlJonas
    Hi,

    i noticed the problem still exists. when linear advanced is activated the extruder doesn't turn, but i found out if i set the extrudersteps very low, the extruder turns. Is it possible that my setup need to much Steps to calculate?

    Best Regards
  • RepetierRepetier
    We use a 32 bit variable for steps. Also computation might make it not use all bits I wonder if you need so many steps that it does not work any more. 

    - M232 - Read and reset max. advance values

    Should output maximum steps used (limited to 32000). So what does it show and what are your extruder steps per mm and L that it is so much? L 40 would be normal for direct extruder. As I already said, do not use K.
  • CarlJonasCarlJonas
    Thank you for the fast reply. I have 6500 steps/mm for the extruder. I only use L but the problem is, when i activate USE_ADVANCE the extruder doesn't move. Even not in the Filament change menu. So in the end, until now i wasn't able to use the advance algorithm. What can i do next?
  • RepetierRepetier
    Wow - 6500 is full overkill. If you are on 8 bit platform even more. Extruder can there move max. 10-15kHz frequency, so limit is 1-2mm/s. This might even limit max. xy speed. Most extruders have 100-200 here and values around 500 would be very good precision. Do not think anything above woul dbe visible and just cost cpu power and limits speed. For a normal retraction with 30mm/s this means 30*6500 = 195000Hz - AVR is limited to 40KHz in non advance mode. So in your cased I would reduce microstepping to get a more coarse resolution with benefit of better speed. I would not really wonder if that also causes overflows with advance making it fail.
  • CarlJonasCarlJonas
    i understand. I use a radds board with arduino due. i will change the microstepping and try it again. thank you very much. next step is to buy some tmc 2130 with interpolation from 16 to 256 microsteps.
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