Constant velocity mode

  • My printer gets quite noisy going point to point. I had the same problem with my cnc mill running mach 3, but there is a constant velocity mode where it will attempt to maintain velocity with set acceleration unless certain conditions prevent it such as changing direction on a single axis move. This setting improved the noise and finish quality on my mill and I have a hunch it would be really beneficial for printers as well.

    Here is a link to the constant velocity documentation from mach 3.

    I hope this can make it on the short list of improvements, I think it will help out a lot.

  • This is essentially what the "lookahead/planner" in the firmware already do. The jerk or instantaneous velocity change is the setting most related to this. The planner looks at the velocity change vector (dv) and determines how much it needs to slow the head down in order to be within this parameter.

    This is a big problem for 8 bit controllers (obviously the Duet is 32 bit) as their move buffer often runs out on fast machines, especially when doing circles. In those cases, since the planner has no moves to compare the current velocity to, it comes to a complete stop at the next point and then picks up again from there.

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