[BUG] delta_calibrate and z_offset

General Discussion
1

Basic Information:

Printer Model: Custom Delta Printer
MCU / Printerboard: BTT Pico
Host / SBC: BTT Pi
klippy.log

I am setting up a probe and noticed the automatic “delta_calibrate” command appears to be calculating delta geometry incorrectly, and I think it has something to do with probe, “z_offset”. delta_calibrate is calculating arm lengths/ delta radius to be ~3/ 1.5x their actual dimensions.

If it matters, I’ve confirmed my probe is working correctly/ it works just fine when doing things like probe_calibrate and bed_mesh_calibrate.

Correct known dimensions for my printer

  • End stops at ~407mm (previously calculated using DELTA_CALIBRATE METHOD=manual)
  • Arm length of ~440mm (previously calculated using DELTA_CALIBRATE METHOD=manual)
  • Delta radius of ~232mm (previously calculated using DELTA_CALIBRATE METHOD=manual)
  • Probe z_offset of ~ 22.5mm (calculated using probe_calibrate, which gives correct results)

For quick reference, incorrect results of current delta_calibrate command

  • stepper_a: position_endstop: 402.833554 angle: 212.749820 arm_length: 1361.267107
  • stepper_b: position_endstop: 411.978615 angle: 333.176185 arm_length: 1257.387203
  • stepper_c: position_endstop: 405.020518 angle: 90.000000 arm_length: 1341.840522
  • delta_radius: 411.129110

klippy.zip (1.2 MB)