Delta Homing Behavior

fieryjekyll

Hello. I'm confused about homing behavior with RepRapFirmware 3. I'm using the default homedelta.g that was generated by the RRF config tool, and I'm using a Duet 2 WiFi on a Mini Kossel.

My build height is 240mm (actually 241.619mm). When I power up my printer, regardless of the actual state of the printer, RRF sets the x, y, and z coordinates to (0, 0, 240), the home position, and reminds me that the axes have not yet been homed.

When I home the axes (G28), the carriages move up to the top of the printer, but the resulting position is not reset to the home position. This leads RRF to set the printer's position to something completely outside of the build dimensions, e.g. (0.1, 0.2, 443.7). Basically, it is adding the amount of Z travel to the initial, default position.

Below is my homedelta.g, which is unmodified from what I got from the RRF config tool.

; homedelta.g
; called to home all towers on a delta printer
;
; generated by RepRapFirmware Configuration Tool v3.2.1 on Mon Jan 18 2021 01:46:04 GMT-0800 (Pacific Standard Time)
G91                        ; relative positioning
G1 H1 X265 Y265 Z265 F1800 ; move all towers to the high end stopping at the endstops (first pass)
G1 H2 X-5 Y-5 Z-5 F1800    ; go down a few mm
G1 H1 X10 Y10 Z10 F360     ; move all towers up once more (second pass)
G1 Z-5 F6000               ; move down a few mm so that the nozzle can be centred
G90                        ; absolute positioning
G1 X0 Y0 F6000             ; move X+Y to the centre

The behavior is problematic because the firmware thinks the printer head is somewhere that it is not. When I home the printer again, I'll get an error: G0/G1: target position not reachable from current position. If I try to calibrate the printer in this state (G32), the print head will crash into the bed.

If this is the default behavior, then I have to believe this configuration is working for most people. So am I doing something wrong?

To make the printer useful at all, after homing, I manually reset the z coordinate to the build height (which I've determined from calibration). Is this something I'm supposed to add to homedelta.g myself?

Thanks.

Doug

Veti

post your config.g

Phaedrux

You must select High End for the endstops in the configurator. If you don't it will do something silly like generate low end endstops for a delta. Which probably explains the crazy coordinates.

Make sure your M574 is configured for high end endstops.

https://duet3d.dozuki.com/Wiki/Gcode?revisionid=HEAD#Section_M574_Set_endstop_configuration

And yes, I've asked for the defaults for delta to be auto selected as high end.