Polar Printing Kinematics with U-axis



  • Hello all! We are playing around with polar printing using a Duet 2 Wifi. Does anyone know if polar kinematics work with a linear U-axis and rotational Y-axis (instead of the traditional linear X-axis and rotational Y)? If not, is there a way to tweak the config, homing or FW to use the U-axis with polar kinematics?

    Firmware Name: RepRapFirmware for Duet 2 WiFi/Ethernet
    Firmware Electronics: Duet WiFi 1.02 or later + DueX5
    Firmware Version: 2.05+1 (2020-01-19b1)


  • administrators

    What will you be using the X axis for?



  • @dc42 said in Polar Printing Kinematics with U-axis:

    What will you be using the X axis for?

    Hi dc42, thank you for the quick reply! We want to use U for a couple of reasons: 1) so we can control the feedrate based on Y only, 2) so we can use more than one linear axis in the future.


  • administrators

    Is your printer really a polar printer (maybe a kind of IDEX polar printer with one turntable and 2 radial arms)? Controlling the feed rate based on Y motion only doesn't really make sense for a polar printer. Or is it more like a Cartesian printer with an added rotary axis?



  • @dc42 said in Polar Printing Kinematics with U-axis:

    IDEX polar printer

    Yes more of an IDEX polar printer, although we don't want the heads just to mirror, so we were thinking of giving specific Y feed rates to have better control when printing at two different radii.

    Is there a way to use X and an additional axis as two radial arms where both run through the polar kinematics and feed rate adjustments?


  • administrators

    @gantri_hw said in Polar Printing Kinematics with U-axis:

    @dc42 said in Polar Printing Kinematics with U-axis:

    IDEX polar printer

    Yes more of an IDEX polar printer, although we don't want the heads just to mirror, so we were thinking of giving specific Y feed rates to have better control when printing at two different radii.

    Is there a way to use X and an additional axis as two radial arms where both run through the polar kinematics and feed rate adjustments?

    If you are saying that you want to print two different objects at the same time, then that will require very special preparation of the GCode. Your best option would be to generate GCode that has all the segmentation and Cartesian-to-Polar coordinate transformation already done, then you can configure the printer as a straight 4-axis Cartesian printer (XYZU).

    If you don't want to do that but you do want to be able to switch between 2 tools, the simplest approach would be to have both tools run on the same linear rail and cover the same radius values. Then the coordinate transformation would be the same for both heads. You could use the existing Polar kinematics, and use the M584 command to switch the X axis to either the X or the U motor in the tool change files.

    HTH David



  • @dc42 said in Polar Printing Kinematics with U-axis:

    If you are saying that you want to print two different objects at the same time, then that will require very special preparation of the GCode. Your best option would be to generate GCode that has all the segmentation and Cartesian-to-Polar coordinate transformation already done, then you can configure the printer as a straight 4-axis Cartesian printer (XYZU).
    If you don't want to do that but you do want to be able to switch between 2 tools, the simplest approach would be to have both tools run on the same linear rail and cover the same radius values. Then the coordinate transformation would be the same for both heads. You could use the existing Polar kinematics, and use the M584 command to switch the X axis to either the X or the U motor in the tool change files.
    HTH David

    David, that helps a ton. At this time, I think the best approach for us is to prepare our own GCode and treat it as a 4-axis Cartesian printer.

    Thank you for your help!


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