Dual Z Towers BL Touch Configuration

demodemo

Hello, I'm currently building a machine which has 2 independent Z towers (1 for each extruder, similar to Zidex https://www.drdflo.com/pages/Projects/Zidex.html). The 2 towers are synced during operation, but separately operated during z homing.

In homez.g, I have configured the BL touch declaration separately, and only when the BL touch is needed for homing each tower.

The movements are executed per expected, BL touch for Tower 1 and Tower 2 are declared and G30 bed probe accordingly. However, I adjust the Tower 2 Z trigger height of Bltouch, the offset is applied to the first BLtouch of Tower 1 together with Tower 2, which is unexpected.

Therefore, I'm unable to make Tower 1 nozzle and Tower 2 nozzle to lightly touch bed at z=0, when Tower 1 nozzle is perfect, Tower 2 nozzle is too far from bed, when Tower 2 nozzle is perfect, Tower 1 nozzle reaches too low into bed.

I'd like to seek any advice to see why my configurations of homez.g having separate BL touch configurations, the Z trigger height seems to apply to both cases.

I'd be grateful for any help and happy to supplement with more details. Thank you very much in advance.

; homez.g
; called to home the Z axis
;

M584 Z0.2                                   ; Split the 2 Z towers for independent control. this will move tower 1 only
T0 P0                                       ; Select Tool 0 without running tfree tpre tpost

G1 X0 Y0 F6000                              ; 
G1 X150 Y150 F6000                          ; move T0 into center position

M950 S0 C"io7.out"                          ; create servo pin 0 for BLTouch 0
M558 P9 C"io7.in" H10 F300 T6000            ; set Z probe type to bltouch and the dive height + speeds
G31 P500 X-45 Y-75 Z2.5                       ; set Z probe trigger value, offset and trigger height
M557 X30:280 Y30:280 S50                    ; define mesh grid

G30                                         ; this will home and probe the tower 1
M280 P0 S160                                ; retract again if probe retract fails
G29 S1 			                            ; load height map

M584 Z0.5                                   ; Split the 2 Z towers for independent control. this will move tower 2 only
T1 P0                                       ; Select Tool 1 without running tfree tpre tpost

G1 U150 Y150 F6000                          ; move t1 into center position

M950 S0 C"io4.out"                          ; create servo pin 0 for BLTouch 0
M558 P9 C"io4.in" H10 F300 T6000            ; set Z probe type to bltouch and the dive height + speeds
G31 P500 U35 Y10 Z2.5                       ; set Z probe trigger value, offset and trigger height
M557 U50:250 Y50:250 S50                    ; define mesh grid

G30                                         ; this will home and probe the tower 2
M280 P0 S160                                ; retract again if probe retract fails
G29 S1                                      ; load height map



T0 P0                                       ; Select Tool 0 without running tfree tpre tpost
M584 Z0.2:0.5

;DEFINE IO7 PROBE AS DEFAULT
M950 S0 C"io7.out"                          ; create servo pin 0 for BLTouch 0
M558 P9 C"io7.in" H10 F300 T6000            ; set Z probe type to bltouch and the dive height + speeds
G31 P500 X-45 Y-75 Z2.5                     ; set Z probe trigger value, offset and trigger height
M557 X30:280 Y30:280 S50                    ; define mesh grid

danzaywer

@demodemo not how such a situation is handled, I would leave z with 2 motors and try to create 2 additional axes with a single motor, I would do the homing of the 2 axes and then do the homin of z and see if it keeps the offset

droftarts

@demodemo use the M558 K parameter to define the two probes individually, see https://duet3d.dozuki.com/Wiki/M558#Section_M558_in_RepRapFirmware_Num_3. Then probe with G30 K# to define which probe to use for each Z axis. Then you don’t have to keep redefining the probe.

Ian

demodemo

@droftarts thank you for your advice.

I now understand that a K value can be inserted to M558 command to configure separate z probes.
what about M950 where the BLtouch servo pin is declared, how do I change M950 command for each servo to correspond to each k value Bltouch specifically?

Thank you very much.

droftarts

@demodemo M950 S0 for first, M950 S1 for second, where S is the servo number. Make separate deploy and retract Gcode files for each probe and servo; use deployprobe0.g and retractprobe0.g for probe 0, deployprobe1.g and retractprobe1.g for probe 1. Deploy and retract macros should reference the respective servo for each probe.

Ian