Motor speed limits



  • So we have maximum machine speeds and feed rates, which is great. It's a start. But feels like something that's more a first-pass approach than it is a final stop.

    Whether it be coreXY, Cartesian, delta, etc, there is more than a single motor doing the driving. In my case, I use coreXY. When moving in 45 degree diagonals, only one motor does the work. That speed caps out at some arbitrary value, J. When moving in strict X or strict Y directions, both motors assist in movement, and would thusly create a maximum motion speed of 1.41*J.

    The same concepts can be applied to delta or Cartesian systems too, where the angle of a motion will result in different motor speeds for a given feed rate.



  • @SnowDrifter M203 could be what you search for, https://duet3d.dozuki.com/Wiki/Gcode#Section_M203_Set_maximum_feedrate
    The feedrates are axis values.



  • A coreXY machine doesn't obey traditional by-axis speeds



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  • @SnowDrifter What is the purpose of this thread? Are you asking a question, making a statement, asking for advice, or requesting a change or additional feature?

    Ultimately, the maximum motor speed will be determined by the torque curve of the motor(s). The maximum acceleration is a function of that torque divided by the mass to be moved and the maximum speed can therefore be calculated as sqrt(2x acceleration x distance/2). Most machines will never attain the maximum motor speed unless the axes travel distances are large enough to accommodate the acceleration and deceleration phases. In general terms, it is the rate of acceleration that the machine can withstand which will determine the maximum speed that can be attained. But that only applies to non-print moves. Print moves will be limited by the speed at which filament can be melted and extruded and those moves will be far below the motor speed limits.



  • @deckingman said in Motor speed limits:

    @SnowDrifter What is the purpose of this thread? Are you asking a question, making a statement, asking for advice, or requesting a change or additional feature?

    Ultimately, the maximum motor speed will be determined by the torque curve of the motor(s). The maximum acceleration is a function of that torque divided by the mass to be moved and the maximum speed can therefore be calculated as sqrt(2x acceleration x distance/2). Most machines will never attain the maximum motor speed unless the axes travel distances are large enough to accommodate the acceleration and deceleration phases. In general terms, it is the rate of acceleration that the machine can withstand which will determine the maximum speed that can be attained. But that only applies to non-print moves. Print moves will be limited by the speed at which filament can be melted and extruded and those moves will be far below the motor speed limits.

    It's a feature request. I want to limit individual motor speeds as the traditional X and Y speeds don't apply well to a corxy since everything's 'rotated' 45 degrees.



  • @SnowDrifter said in Motor speed limits:

    It's a feature request. I want to limit individual motor speeds as the traditional X and Y speeds don't apply well to a corxy since everything's 'rotated' 45 degrees.

    That's sounds as a well defined request since the motor has it's own rotational speed limit (pulse rate and such) and the ratio of head linear distance to motor's rotational speed varies with the head's position.

    I will leave to others to determine if this is a useful feature or not.



  • Apropos max speed, just stumbled upon this video where the duet is pushed to its speed limit.

    https://youtu.be/fVSZPHsiQDQ



  • @zapta said in Motor speed limits:

    Apropos max speed, just stumbled upon this video where the duet is pushed to its speed limit.

    https://youtu.be/fVSZPHsiQDQ

    Which kind of indicates that having a limits for motor speed is somewhat irrelevant IMO.



  • Here is another view of same printer. It seems to move from island to island in zero time. As if the moves were edited out.

    https://www.youtube.com/watch?v=1sPf8K_JV08



  • @zapta That is seriously fast travel speed - love it!


  • Moderator

    @zapta said in Motor speed limits:

    Here is another view of same printer. It seems to move from island to island in zero time. As if the moves were edited out.

    https://www.youtube.com/watch?v=1sPf8K_JV08

    I wonder if this is the same person... @PAULDGROOT


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