Fast home vs accurate.



  • Hey all. So I have a machine that has a high end Z-stop and a BLtouch. I would like the initial home to be fast, and an immedaite followed by a more accurate probe. If I define:

    M558 P9 C"io7.in" H5 F800 T16000 
    G30
    M558 P9 C"io7.in" H5 F150 T16000       
    G30
    

    It seems to work well, as far as finding a "rough z" quickly and then an accurate Z, but it seems to effect the z-offset and and I dont know why. Is there a better way?


  • Moderator

    @Demi said in Fast home vs accurate.:

    but it seems to effect the z-offset

    How so?

    That is exactly how I use my BLTouch. What exactly are you seeing happen?



  • I have absolutely no idea. The Z-off just seems to......drift? I had to add .50 to it, so its not too much or anything, but it seems to effect.



  • @Phaedrux
    I played with it some more to get a better idea of how to explain what I am seeing. Its as if any z trigger defined in config.g is no longer effecting the z trigger height. If I dont use the "double home" and travel to Z0, its exactly where it should be. If I do, its 2.5-3mm off the bed at Z0. I have set the trigger height all the way down to 1mm and it always ends up at the same height, floating above home.

    I have ```
    M558 P9 C"io7.in" H5 F150 T16000

    in config.g and the cgode in the first post in homeall.g. Should I be using G28Z instead of G30?

  • Moderator

    Can you please post your full config.g and homeall/homez?

    It's impossible to say what's going on without seeing the configuration.



  • @Phaedrux

    Whoops, sorry about that!

    ; Configuration file for Duet 3 (firmware version 3)
    ; executed by the firmware on start-up
    ;
    ; generated by RepRapFirmware Configuration Tool v2.1.8 on Fri Apr 17 2020 12:59:14 GMT-0400 (Eastern Daylight Time)
    
    ; General preferences
    G90                                          ; send absolute coordinates...
    M83                                          ; ...but relative extruder moves
    M550 P"Evo Duet 1"                           ; set printer name
    
    M667 S1                                      ; select CoreXY mode
    
    ; Network
    M552 P0.0.0.0 S1                             ; enable network and acquire dynamic address via DHCP
    M586 P0 S1                                   ; enable HTTP
    M586 P1 S0                                   ; disable FTP
    M586 P2 S0                                   ; disable Telnet
    
    ; Drives
    M569 P0.0 S1                                 ; physical drive 0.0 goes forwards
    M569 P0.1 S0                                 ; physical drive 0.1 goes backwards
    M569 P0.2 S0                                 ; physical drive 0.2 goes backwards
    M569 P0.5 S0                                 ; physical drive 0.5 goes backwards
    M584 X0.0 Y0.1 Z0.2 E0.5                     ; set drive mapping
    M350 X16 Y16 Z16 E16 I1                      ; configure microstepping with interpolation
    M92 X100.00 Y100.00 Z806.45 E837.00          ; STOCK E837 STOCK Z806 set steps per mm
    M566 X800.00 Y800.00 Z15.00 E12.00         ; set maximum instantaneous speed changes (mm/min)
    M203 X7800.00 Y7800.00 Z1500.00 E1200.00     ; set maximum speeds (mm/min)
    M201 X850.00 Y850.00 Z20.00 E250.00          ; set accelerations (mm/s^2) (LAST 3000XY)too much
    M906 X1500 Y1500 Z1500 E1680 I30                 ; set motor currents (mA) and motor idle factor in per cent
    M84 S30                                      ; Set idle timeout
    
    ; Axis Limits
    M208 X0 Y0 Z0 S1                             ; set axis minima
    M208 X290 Y285 Z570 S0                       ; set axis maxima
    
    ; Endstops
    M574 X1 S1 P"io0.in"                         ; configure active-high endstop for low end on X via pin io0.in
    M574 Y1 S1 P"io1.in"                         ; configure active-high endstop for low end on Y via pin io1.in
    M574 Z1 S2                                   ; configure Z-probe endstop for low end on Z
    
    ; Z-Probe
    M950 S0 C"io7.out"                           ; create servo pin 0 for BLTouch
    M558 P9 C"io7.in" H5 F350 T10000             ; set Z probe type to bltouch and the dive height + speeds
    G31 P500 X22 Y24 Z2.75                   ; set Z probe trigger value, offset and trigger height
    M557 X15:300 Y15:300 S60                     ; define mesh gridM557 X5:255 Y10:300 S40 
    
    
    ; Heaters
    M308 S0 P"temp0" Y"thermistor" T100000 B4138 ; configure sensor 0 as thermistor on pin temp0
    M950 H0 C"out0" T0                           ; create bed heater output on out0 and map it to sensor 0
    M143 H0 S120                                 ; set temperature limit for heater 0 to 120C
    M307 H0 B1 S1.00                             ; enable bang-bang mode for the bed heater and set PWM limit
    M140 H0                                      ; map heated bed to heater 0
    M308 S1 P"temp1" Y"thermistor" T100000 B4138 ; configure sensor 1 as thermistor on pin temp1
    M950 H1 C"out1" T1                           ; create nozzle heater output on out1 and map it to sensor 1
    M143 H1 S280                                 ; set temperature limit for heater 1 to 280C
    M307 H1 B0 S1.00                             ; disable bang-bang mode for heater  and set PWM limit
    M308 S2 P"temp2" Y"thermistor" T100000 B4138 ; configure sensor 2 as thermistor on pin temp2
    M950 H2 C"out2" T2                           ; create chamber heater output on out2 and map it to sensor 2
    M143 H2 S280                                 ; set temperature limit for heater 2 to 280C
    M307 H2 B1 S1.00                             ; enable bang-bang mode for the chamber heater and set PWM limit
    M141 H2                                      ; map chamber to heater 2
    
    ; Fans
    M950 F0 C"out7" Q500                         ; create fan 0 on pin out7 and set its frequency
    M106 P0 C"Part Fan" S0 H-1                   ; set fan 0 name and value. Thermostatic control is turned off
    M950 F1 C"out9" Q500                         ; create fan 1 on pin out9 and set its frequency
    M106 P1 C"HotEnd Fan" S1 H1 T45              ; set fan 1 name and value. Thermostatic control is turned on
    M950 F2 C"out3" Q500                         ; create fan 2 on pin out3 and set its frequency
    M106 P2 C"CaseFan1" S0.25 H-1                ; set fan 2 name and value. Thermostatic control is turned off
    
    ; Tools
    M563 P0 D0 H1 F0                             ; define tool 0
    G10 P0 X0 Y0 Z0                              ; set tool 0 axis offsets
    G10 P0 R0 S0                                 ; set initial tool 0 active and standby temperatures to 0C
    
    ; Custom settings
    M307 H0 A110 C600 D60 S1
    M307 H1 A598.7 C312.1 D3.3 S1
    M307 H2 A70 C600 D60 S1
    						; filament sensor
    ;M950 J12 C"io6.in" ;working
    ;M581 P12 T3 S1 C1	;working
    M591 D0 P2 C"io6.in" S1
    
    
    
    
    ; Miscellaneous
    T0                                           ; select first tool
    
    
    

  • administrators

    You can send G31 without parameters to check what the trigger height is set to.

    We also need to see your homez.g and homeall.g files.



  • Oh thats handy, okay I will check that and see if it changes as soon as I can.

    ; homeall.g
    ; called to home all axes
    ;
    ; generated by RepRapFirmware Configuration Tool v2.1.8 on Fri Apr 17 2020 12:59:14 GMT-0400 (Eastern Daylight Time)
    
    M564 H0
    G91                     ; relative positioning
    G1 H2 Z5 F7200          ; lift Z relative to current position
    M558 P9 C"io7.in" H5 F600 T10000  
    
    G1 H1 X-345 Y-345 F7200 ; move quickly to X or Y endstop and stop there (first pass)
    G1 H1 X-345             ; home X axis
    G1 H1 Y-345             ; home Y axis
    G1 X5 Y5 F7200          ; go back a few mm
    G1 H1 X-345 F1800       ; move slowly to X axis endstop once more (second pass)
    G1 H1 Y-345             ; then move slowly to Y axis endstop
    G90                     ; absolute positioning
    G1 X-7 Y-9 F7200        ; go to first bed probe point and home Z
    G30                     ; home Z by probing the bed
    M558 P9 C"io7.in" H5 F150 T10000  
    G30
    
    M564 H1
    
     
    ; Uncomment the following lines to lift Z after probing
    ;G91                    ; relative positioning
    ;G1 Z5 F120             ; lift Z relative to current position
    ;G90                    ; absolute positioning
    
    
    
    ; homez.g
    ; called to home the Z axis
    ;
    ; generated by RepRapFirmware Configuration Tool v2.1.8 on Fri Apr 17 2020 12:59:14 GMT-0400 (Eastern Daylight Time)
    G91              ; relative positioning
    G1 H2 Z5 F7200   ; lift Z relative to current position
    G90              ; absolute positioning
    G1 X-7 Y-9 F7200 ; go to first probe point
    G30              ; home Z by probing the bed
    
    ; Uncomment the following lines to lift Z after probing
    ;G91             ; relative positioning
    ;G1 Z5 F120      ; lift Z relative to current position
    ;G90             ; absolute positioning
    


  • Okay, so I went line by line to see when the z-trigger height changed. In my latest config its set to 2.8
    G31 reports the same. When Homeall.g runs:

    M558 P9 C"io7.in" H5 F600 T5000 
    

    G31 reports 0.7.
    Thats when it is changing but I dont understand why. Unless re-declaring the pin without defining the mesh defaults to 0.7? I suppose I could just define the mesh 3 times?


  • Moderator

    Here are a few things I would change in your config and homing file. Though I don't see anything that would really explain the issue. However, these changes may improve things.

    In config.g modify your M558 and G31 to be:

    M558 P9 C"io7.in" H5 F60 T7800 A10 R0.5 S0.005
    G31 P25 X22 Y24 Z2.75
    

    This will force the BLtouch to be a bit more accurate and repeatable.

    Then in homeall.g I see you're using M564 H0 to allow movement before homing, which isn't necessary because you have an H2 in the Z move already and all the other moves are homing moves. You also don't need to duplicate the entire M558 command from config.g to change the dive speed, we can just use the F and A value to get what we want. You've also got it probing in the corner of the bed. Best to use the center.

    ; homeall.g called to home all axes
    M400 ; wait for movement to stop
    M913 X50 Y50 Z50 ; drop motor currents for safer homing
    G91                     ; relative positioning
    G1 H2 Z5 F7200          ; lift Z relative to current position
    G1 H1 X-345 Y-345 F7200 ; move quickly to X or Y endstop and stop there (first pass)
    G1 H1 X-345             ; home X axis
    G1 H1 Y-345             ; home Y axis
    G1 X5 Y5 F7200          ; go back a few mm
    G1 H1 X-345 F1800       ; move slowly to X axis endstop once more (second pass)
    G1 H1 Y-345             ; then move slowly to Y axis endstop
    G90                     ; absolute positioning
    G1 X134 Y130.5 F7200        ; Move probe to bed center
    M558 F600 A1 ; Set single fast probe 
    G30                     ; home Z by probing the bed quickly
    M558 F60 A10 ; set slower multi probing
    G30                    ; probe again for accuracy
    G1 X10 Y10 Z10 ; return to parking position
    M400 ; wait for movement to stop
    M913 X100 Y100 Z100 ; return motor currents to normal
    

    It's up to you if you want to do the same in homez.

    Please test and let me know how it goes.



  • @Phaedrux
    Woah. This is a treasure trove of information. So many new uses, that solve a number of things I have been working on. The M913 is exactly what I was looking for, thats brilliant. Im starting to understand part of my learning problem, I go to the zuki, look for the command and immediately scroll to the applicable firmware, not realizing that often only changes are listed. M558 for example, I had no idea feedrate was supported. Headslap. I used your changes, and it works perfectly thank you so much!

    One I dont fully understand is the P flag for G31. If I half understand, it sets the threshold for the signal for , in my case, the BLTOUCH. How is this value determined?

    Phaedrux, and everyone here, you have all been so helpful, and it really is appreciated. This seems to be a really amazing community, and thank you for taking the time.


  • Moderator

    Glad that helped you out. Sometimes all it takes is examples to open the eyes to what's possible.

    Yes the G31 P value is the threshold for triggering. Setting it low allows it to be picked up on the rising edge (from my limited understanding). The range is from 1 to 1000. For analogue probes I believe you can use it to tune the sensitivity a bit more. 500 is probably fine for most probes/switches. A while ago when the BLtouch got it's own probe type (P9) it was recommended to use P25. Wish I could tell you more than that.

    If you send G31 now does it always reply with the correct trigger height?



  • @Phaedrux
    It sure does. It works like an absolute champ. Thank you so much.


  • Moderator

    It must have been from having the full M558 in the homing file. I think 0.7 is the default in the firmware.

    It's also RRF3 so things are a bit different now sometimes. Which firmware version exactly are you using? Duet Wifi or Duet 3? Pi connected or standalone?



  • Using stand alone Duet 3, MB6HC 3.01-RC10, Duet Web Control 2.1.5. I think youre right. Went I went line by line, M558 is where it changed back to 0.7.


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