Where is the code for a Z probe?



  • I have a BLTouch on my FT-5. Not sure if this is an issue with my BLTouch or something in the firmware/Config. Whenever I home Z, the probe is done at the center of the bed. So far so good. Then as soon as the probe detects the bed the bed drops down 5 or 10mm as you would expect. Here is the problem...the bed drops so hard and fast it sounds like the belt is going to snap!
    Does anyone know where the code is that tells the bed to drop after a probe is detected? I often get a G28 error after this happens!


  • administrators

    @jdefant check out:
    https://duet3d.dozuki.com/Wiki/Connecting_a_Z_probe#Section_Software_setup

    The M558 can G1 commands contain the configuration settings.



  • I have a coreXY with a heavy bed as well and had a similar problem with the short rapid moves during probing so I modify the Z axis movement speeds in the homing files temporarily.

    ; homeall.g
    ; called to home all axes
    ;
    
    ; BLTouch prep so we don't catch the probe pin on the edge of the bed
    ;
    M280 P3 S160 I1 		; Alarm Release and Push-Pin UP just in case it's in alarm and deployed
    M402				; Retract probe just in case it's down
    
    ; Drop the bed for travel
    ;
    G91                     	; relative positioning
    G1 Z5 F200 S2        		; Lower bed 5mm to ensure it is below the switch trigger height
    
    ; Home XY
    ;
    M913 X30 Y30	 		; set X Y motors to 30% of their normal current for homing
    G1 S1 X-375 Y305 F4000   	; course home X or Y
    G1 S1 X-375 F4000              	; course home X
    G1 S1 Y305 F4000              	; course home Y
    G1 X5 Y-5 F1000             	; move away from the endstops
    G1 S1 X-10 F800           	; fine home X
    G1 S1 Y10 F800               	; fine home Y
    M913 X85 Y85	 		; set X Y motors to 85% of their max rated current
    
    ; Z homing section for BLTouch follows
    ;
    G90				; absolute positioning
    G1 X190 Y90 F6000		; Move x and Y axis over to bed center so probe is on top of bed
    
    ; Set lower speeds for homing
    M566 Z5				; Set maximum instantaneous speed changes (mm/min) (Jerk)
    M203 Z400			; Set maximum speeds (mm/min)
    M201 Z100	 		; Set maximum accelerations (mm/s^2)
    
    ; Probe the bed
    ;
    M558 A1 F350			; Set single probing at faster feed rate
    G30 				; Do a single probe to home our Z axis
    M558 A10 F100			; Set tripple probing at slower feed rate
    G30				; Probe again to get a more accurate position
    
    ; Set normal speeds again
    M566 Z75			; Set maximum instantaneous speed changes (mm/min) (Jerk)
    M203 Z500			; Set maximum speeds (mm/min)
    M201 Z200			; Set maximum accelerations (mm/s^2)
    
    ; Move X and Y back Home
    ;
    G1 X0 Y270 Z5
    

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