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  1. #1
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    Custom kinematic

    Is it possible to have a custom kinematic in planetcnc? Looking at the most recent user manual and digging through the settings it looks like it isn't possible, but used to be? H-bot and delta are mentioned. I was expecting an entry for Kinematic under Motion settings.

    All I am looking to do is correct for out-of-square (XY plane), so close to the trivial Cartesian kinematic. The machine is too stiff to gantry square.

  2. #2
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    Re: Custom kinematic

    Can't say I'm not disappointed! Poor form mentioning kinematics in the manual that are not supported. Limited value in a 9 axis board if you would be stuck in joint space.

  3. #3
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    Re: Custom kinematic

    Hi,

    We are currently developing a feature currently called "Meta(morphosis) Offset".
    User will be able to use its own calculations (dedicated files, located in users Profile folder) to support unconventional types of machines.

  4. #4
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    Re: Custom kinematic

    Sounds promising - do you have a timescale? Can you clarify if this is standard forward/inverse kinematics? Conventional terminology is preferable to the user (kinematic, joints, axes, etc.).

  5. #5
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    Re: Custom kinematic

    Hi,
    Mach3 had a feature that could do as you want....but it was never very successful.

    It allowed you to program the position of one axis and mathematically combine that with other axes for example:

    X= X + 0.05*cos(Y) or something along those lines. The only problem was that when it was applied was never very consistent. In most cases it was evenly applied but at the start of a job it
    would apply a axis correction in one hit, which often resulted in the steppers missing steps or stalling. For this reason it was never very successful. Having said that for a small angular correction
    between axes it might well work OK.

    It was never intended to be able to do wide ranging kinematic calculations and to my knowledge never tried to reverse the calculation, ie its not a solver.

    Most Windows CNC software including PlanetCNC, Mach, UCCNC are all 'Cartesian Kinematic' and all work perfectly well. Is it likely that any of these companies would invest the huge amount
    of time and research necessary to produce wide ranging kinematic solvers?....and for so few customers? Some linear combination to overcome an out-of-square gantry might well prove
    useful to enough to justify the effort, but beyond that a wide ranging kinematic solver does not sound realistic.

    Craig

  6. #6
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    Re: Custom kinematic

    I would hope that if the back end of PlanetCNC is structured to allow assigning motors to joints rather than axes then the user can supply the FK and IK functions which should allow the user to do whatever they need, like LinuxCNC.

    Irrespective of what you think is reasonable, clearly PlanetCNC at some point intended to support these kinematics. Quoting the manual:

    1.2 Features and specifications:
    ...
    • advanced motion interpolation and kinematic algorithms
    ...

    2.9.15 Motion
    This settings tab deals with machine motion in 3D space (from effector (tool) point of view).
    Short explanation:
    With use of combined motors per axis and special mechanics you can achieve movement which
    doesn’t follow the same kinematic rules as linear motion CNC’s. At that moment we do not
    perceive each motor as independent axis but as a system, which movement is result of
    simultaneous motion of multiple motors. Examples of such machines are H-bot, Delta printer or
    multiple axis machines.
    You can configure motion related parameters such as maximum machine/effector speeds,
    acceleration, deceleration. Machine motion range, blend and advanced settings

  7. #7
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    Re: Custom kinematic

    Hi,

    Irrespective of what you think is reasonable, clearly PlanetCNC at some point intended to support these kinematics. Quoting the manual:
    To date none of the regular Windows based CNC software have even simple kinematics OTHER THAN the regular Cartesian Kinematic which we are accustomed to. Mach have had a go,
    with limited success, PlanetCNC have indicated an intention yet not delivered yet......

    I ask again...'Do you think it likely that PlanetCNC can or will deliver in a reasonable timeframe?'

    Craig

  8. #8
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    Re: Custom kinematic

    Why mince your words? You seem to be saying PlanetCNC are making false claims, but more fool on me for believing them?

  9. #9
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    Re: Custom kinematic

    Hi,
    my apologies, not at all did I wish to cast aspersions to either PlanetCNC or you.

    I applaud PlanetCNC for trying to do as they have indicated, but understand also that its a major undertaking dealing with the very core of any CNC motion system,
    and have sympathy that it may take a while, even a long while.

    Craig

  10. #10
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    Re: Custom kinematic

    I get it, I do this sort of thing professionally. I just want clear answers.

    edited for risk of emoticon misinterpretation...

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