Issue with 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)

2

Your printer.cfg has distances in the [delta_calibrate] section. It looks to me like detla_analyze was run at some point so it is using that data and calculating arm lengths. The delta calibrate docs have a note that unexpected values may be returned. You could do a bed mesh with that configuration and see how flat that looks but be ready for emergency stop.

I’d delete out all saved configuration by delta calibrate and restart with your known correct values.

3

Thanks for the suggestion; that did the trick.