TMC2660 What khz?



  • I am try to find in this website

    https://wilriker.github.io/microstep-calculator/

    the best values for me extruder but i don't know the Maximum step rate-KHZ of TMC2660 driver than use the Duet Ethernet.

    Somebody can help me?


  • administrators

    I recommend that you normally keep below 100kHz to avoid overloading the processor. However for single motor moves such as extruder retraction, you can go to 200kHz or even higher.

    As a rule of thumb, when using 1.75mm filament I suggest choosing extruder microstepping to give about 800 microsteps/mm.



  • If i use 200khz:

    So, if my step/mm is 600 in x16 (non interpolated) i can use a retraction of 10mm in 6000mm/min. True?

    But i can't use x16 interpolated to 256 because the table say me than maximum is 1250mm/min?

    I am confused or i say true?



  • @fbg 16 interpolated to 256 still uses the same step rate as 16.



  • To conclude an that topic a little bit more:
    the TMC2660 driver can probably handle a lot more steps than the Duet's processor can create. Therefore the processor is the limiting factor in this case.

    This is also why - as @Phaedrux already pointed out - the driver will happily interpolate from x16 to x256 by dividing every pulse coming from the Duet at x16 into another sub-set of 16 microsteps.

    In your case you with 600 steps/mm you can retract with up to 20,000mm/min at x16 (interpolated or not) - but unless you are using 24V it is highly unlikely that back EMF won't stop you from reaching this speed even with the lowest induction motors around.



  • @fbg said in TMC2660 What khz?:

    If i use 200khz:

    So, if my step/mm is 600 in x16 (non interpolated) i can use a retraction of 10mm in 6000mm/min. True?

    But i can't use x16 interpolated to 256 because the table say me than maximum is 1250mm/min?

    I am confused or i say true?

    In case you are still confused after @Phaedrux and @wilriker answers, when you use 16x with interpolation, the Duet outputs 16X micro stepping but the TMC driver chip takes those micro steps and subdivides them into 16 smaller steps. The 200KHz limit applies to the Duet output and it does not matter if you use interpolation or not.



  • OMG!!! Thanks for the answers!
    Now i understand perfectly than is the Khz value.
    @wilriker : I use 24V dc yes

    @Phaedrux If the step rate will be 16 interpolated or not, SO, WHY use interpolated?
    What is the advantage of use interpolated if the final step rate will be the same and the calculations is the same if i use interpolated or not???



  • @fbg said in TMC2660 What khz?:

    @Phaedrux If the step rate will be 16 interpolated or not, SO, WHY use interpolated?
    What is the advantage of use interpolated if the final step rate will be the same and the calculations is the same if i use interpolated or not???

    It just makes it quieter. As we've tried to explain, Duet will output 16X micro-stepping but then the driver chip will divide those 16 micro-steps into another 16 smaller ones. So effectively what the motor sees is 256X even though Duet outputs 16X.



  • Ok i understand.
    So with the same "CPU load" in duet, i will have 256 micro-steps between TMC2660 and stepper.

    Thanks for explain


 

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