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3d delta printer, convert tower vertical position to xyz in space

Discussion in 'Mathematics and Physics' started by Dr_Doggy, Dec 22, 2015.

  1. Dr_Doggy

    Dr_Doggy Well-Known Member

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    My new printer! has 3 vertical towers with rods at length D , which come together to form a position in xyz space.

    Any one happen to know the equation it uses to figure this out?
     
  2. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    The vector length , D of each rod, depends on the RMS difference in each axis.
    So D=√{(X-Xo)²+(Y-Yo)²+(Z-Zo)²}.
    For base Bo at location Xo,Yo,Zo
     
  3. Dr_Doggy

    Dr_Doggy Well-Known Member

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    I am very glad you mentioned about the RMS, actually the reason i ask was cause i was told one of my diagonal rods is bad length, I dont believe this is so , since i sized them while threaded through screw. but he is still probably right. I also used a spread sheet to log results for the G29 code, the best result showed a 0.3mm difference across the z-tower axis in the bed at the corners, but ok in center, like a u shape, however it is not a convex/concave error since the perpendicular axis' are ok aswell . I can post graphical later if it helps.

    is there a way we can break down the D value to each RMS value, so i can tune for a size difference in the towers?
     
  4. dave

    Dave New Member

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  5. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    only by offset from some reference calibrations , such as corner and middle test calibration with some object.

    If your actuator has stiction, there may be hysteresis error.
    If stressed in a static position, there may be geometric bias (offset) in some places more than others.
    If couplers or sleeve bearings have wobble, then other errors can occur including hystereis.
     
    Last edited: Dec 28, 2015
  6. Dr_Doggy

    Dr_Doggy Well-Known Member

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    I have induction probe that returns the offset value of the true bed - nozzle distance when z should = 0, at multiple points across the bed.
    if I understand that , would it help to get a second bed on stilts(level) that would measure the same values but at a higher point in z? it would be simple enough for me to modify code to do this..
     

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