Max Printable radius

Hi, I have a Delta, and I have a question.

What is Max Printable Radius? 

When I send G1 x80 y-45 (or G1 x80 y45) with Max Printable Radius setted under 100, the printer don't move.

Someone could help me please?!



  • You are right in that 80/45 has a distance of 91.78mm from center, but only if the selected tool has no offset. For deltas origin for extruders is center of the carriage. If you have 2 extruder or use a z probe you will have an offset that gets added to these coordinates for verification.
  • This link gives a good idea of Delta Geometry:
    I did not author it.
  • Thanks, Roko.  That's very useful.  

    So can someone tell me what changes to the parameters DELTA_MAX_RADIUS , ROD_RADIUS, and  PRINTER_RADIUS impact?  I found and corrected an error in my steps/mm today (was 40 - should have been 44), which should go a long way toward correcting a scaling error I've had since day one.  Now I'm trying to get the height of the nozzle at the three tower positions and at the center to match.  I've got A, B, and C positions very close to perfect, but I'm having trouble getting the center tweaked the last little bit.  It's currently sitting about 1.7mm higher than the three tower positions. refers to increasing PRINTER_RADIUS in Repetier to lower the nozzle in the center of the bed, but changes to that seem to have reached some kind of limit where increasing it more does little or nothing.  I currently have:

    #define DELTA_DIAGONAL_ROD 352 // 350.00 // 355.87 // 249.57 081818 // mm
    #define DELTA_ALPHA_A 210 
    #define DELTA_ALPHA_B 330
    #define DELTA_ALPHA_C 90
    #define END_EFFECTOR_HORIZONTAL_OFFSET 42 // 40  //40? 081818
    #define CARRIAGE_HORIZONTAL_OFFSET 25  //25? 081818
    #define DELTA_MAX_RADIUS 136 // 134 // 132 // 136.52 081818 //132 081518
    #define ROD_RADIUS 134 // 131 081818
    #define PRINTER_RADIUS 150 // 146 // 144 // 142 // 140 // 135 // 134 // 133.0 // 132.5 //132.0 081818

    (The remarks are previous values, with the starting value and the date at the end.)  I just added the Horizontal_Offset for the carriages and the end effector today; they've apparently always been set to 0 since I switched from Martin to Repetier firmware.  Not sure how that happened.  

    Your input would be appreciated (and has been appreciated in the past with donations ;) .

  • First forget about the END_EFFECTOR_HORIZONTAL_OFFSET and CARRIAGE_HORIZONTAL_OFFSET - they have no impact on the math and make measuring just complicated. Set them to 0 and PRINTER_RADIUS and ROD_RADIUS are the same.
    DELTA_DIAGONAL_ROD is the distance between the 2 rotational centers at carriage and effector. That is the easy to measure part. Now if the effector is exactly in the center the ROD_RADIUS is the horizontal distance between the same points. This is hard to measure exact as center and horzontal distance are more a guess. A wrong value causes the effector make a bump or bow so that is what you calibrate first.

    DELTA_MAX_RADIUS is the maximum reachable radius you want to allow. In theory you can go that far outside that one diagonal is horizontal but there it would move speed toward infinity, so you need to constrain that area to physical reachable and motors staying in limit with speeds. So this is preventing moves outside what makes sense.

  • Thank you. 

    I was using as a guide, and found that if I use his formula of: new DELTA_DIAGONAL_ROD =100 / measured_length * original DELTA_DIAGONAL_ROD, it was going the wrong way (making the printed test object that was already too small even smaller).  If I use "measured/100 * original" it seems to work better, but that could have been a fluke.  

    It would be very helpful if the source code were commented with regard to the offsets, and the radii being the same.  (Does this mean I should always set the two radii to the same value?  If so, why do both exist?)

    Wouldn't want that speed reaching infinity... 
  • Normally one of them would get computed from the other by subtracting the 2 offsets. Call it historical reasons. In next generation V2 there will only be one of them.
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