Allow slower minimum movement speed

  • I switched my Duet3D powered 3D printer to a CNC router, which is working great for the most part.

    My only gripe is the inability to have an axis move slower than 0.5mm/s

    In CNC mode I find this a major limitation.

    It's kind of ridiculous because I could just halve my steps per mm to get 0.25mm/s and then just double my z output from the CAM but that's annoying and somewhat dangerous.

    If there is no technical reason to limit the speed and to save me from rapidly tapping Z-0.05 when drilling into 1/8 inch aluminum....

    I suggest the limit be based on the number of steps per second and not mm.
    It should be something like 10 steps/s, which with a 2mm per rev leadscrew would give 0.1mm/s.

    But really it should be configurable in CNC mode, since I think it is most needed on the Z, so if it could be a command like "M### Z5" for 5steps/s on the z axis that'd be amazing.


  • If the max feed rate configuration command M203 was configured like the axis limits M208 that would grant what you need. Add S1 to configure minimum speeds or S0 (or complete omission of S parameter) to set maximum.

    Defaults are fine for most, but as you say unless there is a hardware reason why there is minimum limit it would make more sense for it to be configurable.

    As you suggest it is probably linked to the steps per mm of common printers and the juttery 40Hz motion you'd get from an 80 step/mm axis running at 0.5mm/sec.

  • This would be very useful for laser-mode as well (very slow cut operations or simply to make underpowered lasers work very slowly)

    @doctrucker said in Allow slower minimum movement speed:


    Are you suggesting to implement S0/S1 in RRF, or are you telling us that it is already there and we can use it? Because doesn't mention anything...

  • No, it's not there. I was suggesting a feature request. Specifying minimum steps per second would also work but would require a new gcode command.

  • administrators

    Agreed, CNC users need to be able to set lower minimum speeds. I'll allow M203 X0.1:100 and similar in 2.03.

  • @dc42 Just spotted that formatting for the M208 commands. Can you confirm that this is only for 2.02+ and not the recent versions of firmware that run on the v0.6 & v0.8.5? I like the us of :, its far more intuative!

  • administrators

    It's supported in 1.23 as well.

  • @dc42 Thanks. Tweaked the duet gcode guide to reflect that.

    Didn't realise it was possible to edit the guides until recently!

  • @dc42 said in Allow slower minimum movement speed:

    n 2.03

    If no one has told you yet today, just wanted to let you know that you're awesome.

    Love the Duet board, your firmware, the community. Great stuff happening here.


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