help needed: first layer in midair (~.5mm)



  • My modified tronxy x5s refuse to print.

    Modiefied means:

    • changing the 8bit board to a duet2 ethernet
    • adding linear rails of the x5sa pro
    • changing the motor mounts to metal ones
    • correting the wiring of the "half heated" bed to 24v driving it through external mosfet (evth. else remains 12v)
    • adding a bltouch
    • changing the wiring to drive each z motor independently for bed leveling

    What works so far:

    Homing and leveling is working so far. Kind of...
    There are some problems with the z offset.

    I completley worked through this: Test and calibrate
    a couple of times.

    I added the appropiate G31 line. rebooted the duet, double checked that there are no overwrites or such (no m501) resulting in having the first layer printed aprox. .5mm above the bed. playing around with the z value in my g31 code i found out, that I can manage to print "higher" than .5mm in midair but not lower (as needed). the head will not go closer to the bed, regardles of the value.

    However: Going down .550mm via baby steps works. Kind of...

    1st.) this is more likely a "duct tape" approach. fixing a symptom not the problem.
    2nd.) it works with small objects like benchys (yes i can print benchys) but larger prints fails like that:

    20200718_182406.jpg

    while with the same settings on the same printer, benchys look like that:

    20200718_182211.jpg

    not perfekt, but ok...

    i'm completley lost here... and really hoping on somebody who might help me here...
    thanks in advance
    Martin

    config.g

    ; Configuration file for Duet WiFi (firmware version 3)
    ; executed by the firmware on start-up
    ;
    ; generated by RepRapFirmware Configuration Tool v3.1.4 on Sat Jul 18 2020 08:51:23 GMT+0200 (MitteleuropƤische Sommerzeit)
    
    ; General preferences
    G90                                            ; send absolute coordinates...
    M83                                            ; ...but relative extruder moves
    M550 P"muellmopped"                            ; set printer name
    M669 K1                                        ; 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 S1                                     ; physical drive 0 goes forwards
    M569 P1 S1                                     ; physical drive 1 goes forwards
    M569 P2 S0                                     ; physical drive 2 goes forwards
    M569 P3 S0                                     ; physical drive 3 goes forwards
    M569 P4 S0                       			   ; Drive 4 goes forwards Ist die rechte z schraube
    
    M584 X0 Y1 Z2:4 E3							   ; two Z motors connected to driver outputs Z and E1
    
    ;M671 X-30:360 Y165:165 S0.5 				   ; leadscrews at left (connected to Z) and right (connected to E1) of X axis !! check !!
    M671 X-30:360 Y0:0 S0.5                        ; leadscrews at left (connected to Z) and right (connected to E1) of X axis
    M208 X-30:360 Y-30:360:
                                
    M350 X16 Y16 Z16 E16 I1                        ; configure microstepping with interpolation
    M92 X80.00 Y80.00 Z400.00 E430.00             ; set steps per mm
    M566 X900.00 Y900.00 Z12.00 E120.00            ; set maximum instantaneous speed changes (mm/min)
    M203 X6000.00 Y6000.00 Z180.00 E1200.00        ; set maximum speeds (mm/min)
    M201 X500.00 Y500.00 Z20.00 E250.00            ; set accelerations (mm/s^2)
    M906 X1000 Y1000 Z1000 E1100 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 X330 Y330 Z400 S0                         ; set axis maxima
    
    ; Endstops
    M574 X1 S1 P"!xstop"                            ; configure active-low endstop for low end on X via pin xstop
    M574 Y1 S1 P"!ystop"                            ; configure active-low endstop for low end on Y via pin ystop
    M574 Z1 S2                                     ; configure Z-probe endstop for low end on Z
    
    ; Z-Probe
    M950 S0 C"exp.heater3"                         ; create servo pin 0 for BLTouch
    M558 P9 C"^zprobe.in" H5 F120 T6000            ; set Z probe type to bltouch and the dive height + speeds
    G31 P500 Z1.900 X-31.85 Y-14.76				   ; set Z probe trigger value, offset and trigger height
    
    
    ;G31 P500 X0 Y0 Z2.5                            ; set Z probe trigger value, offset and trigger height
    ;M557 X15:215 Y15:195 S20                       ; define mesh grid
    
    M557 X30:315 Y30:305 S59                                                          ; Define mesh grid
    
    ; Heaters
    M308 S0 P"bedtemp" Y"thermistor" T100000 B4138 ; configure sensor 0 as thermistor on pin bedtemp
    M950 H0 C"bedheat" T0                          ; create bed heater output on bedheat and map it to sensor 0
    M307 H0 B0 S1.00                               ; disable bang-bang mode for the bed heater and set PWM limit
    M140 H0                                        ; map heated bed to heater 0
    M143 H0 S120                                   ; set temperature limit for heater 0 to 120C
    M308 S1 P"e0temp" Y"thermistor" T100000 B4138  ; configure sensor 1 as thermistor on pin e0temp
    M950 H1 C"e0heat" T1                           ; create nozzle heater output on e0heat and map it to sensor 1
    M307 H1 B0 S1.00                               ; disable bang-bang mode for heater  and set PWM limit
    M307 H0 A214.5 C729.8 D7.5 S1.00 V12.2 B0
    M307 H1 A255.1 C101.4 D3.6 S1.00 V12.1 B0
    ; Fans
    M950 F0 C"fan0" Q500                           ; create fan 0 on pin fan0 and set its frequency
    M106 P0 S0 H-1                                 ; set fan 0 value. Thermostatic control is turned off
    M950 F1 C"fan1" Q500                           ; create fan 1 on pin fan1 and set its frequency
    M106 P1 S1 H1 T45                              ; set fan 1 value. Thermostatic control is turned on
    
    ; 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 are not defined
    
    ; Miscellaneous
    M575 P1 S1 B57600                              ; enable support for PanelDue
    ;M501										   ;restore data from overwrite
    
    

    homez.g

    ; homez.g
    ; called to home the Z axis
    ;
    ; generated by RepRapFirmware Configuration Tool v3.1.4 on Sat Jul 18 2020 08:51:23 GMT+0200 (MitteleuropƤische Sommerzeit)
    G91              ; relative positioning
    
    G1 H2 Z5 F6000   ; lift Z relative to current position
    ;G1 S2 Z4 F200     ; raise head 4mm to ensure it is above the Z probe trigger height
    
    
    G90              ; absolute positioning
    
    ;G1 X15 Y15 F6000 ; go to first probe point
    G1 X165 Y165 F2000 ; put head over the centre of the bed, or wherever you want to probe
    
    G30              ; home Z by probing the bed
    G30 P0 X0 Y165 Z-99999 ; probe near a leadscrew, half way along Y axis
    G30 P1 X280 Y165 Z-99999 S2 ; probe near a leadscrew and calibrate 2 motors
    
    ; Uncomment the following lines to lift Z after probing
    ;G91             ; relative positioning
    ;G1 Z5 F100      ; lift Z relative to current position
    ;G90             ; absolute positioning
    
    
    
    
    


  • While someone will give a better answer and find something in your config.g, I have fine tuned my height, assuming the nozzle & BLtouch is properly fastened (not loose or pin bent) and everything else is tight, using G31 P500 X-31.85 Y-14.76 Zx.xx and changing your current Z1.900 to a higher number, say, Z2.10 to start will get you closer to the bed. Now, being that you are .5mm too high, you may in fact wind up closer to Z2.30~2.40 (ish). Proceed slowly and measure change as to prevent nozzle crash.



  • @Jon hi, thanks for your answer. I already tried that. Actualy Z1.900 is a result of that since the correct z parameter G30 S-1 reported was 1.280. I think that values < 1.280 results in the head being lifted higher over the bed while values > 1.280 have no effect leaving the head hovered .5mm over the bed. I MAYBE WRONG ON THAT AND THE Z PARAMETER HAVE NO EFFECTS AT ALL. Its based on "optical observation" not on measurements. But thanks... šŸ˜‰



  • @Jon And i tried it once again with some greater vals as you suggested. What should i say: @ z3.0 Its now printing a benchy. BUT WITHOUT FIDDELING WITH BABY STEPS. YEAH!! Thanks!

    The problem was, as stated before, when figuring out the z offset as described in "Test and calibrate" I ended up with a value of 1.280. I went up to 1.900 without seeing a difference.

    Dialing down to z0 after homing z i messured the distance from nozzel to bed of 3.0mm. (I piled up some ordinary papers until they filled the gap between nozzel and bed, and measureing the pile with a slide gauge)

    after puttinig these z3.0 to g31 the nozzel touched the bed when dialing down to z0.

    So i suggest the "G30 S-1" way of finding the correct offset is either wrong for my configuration (dual z) or i did something stupidly wrong. (which is absolutly possible)

    Now i have to play around with the "homeall.g" macro but this is another story.
    So at least I'm not stuck anymore. Thanks so much!

    Martin



  • It might be possible that your M208 command "axis minima" Z0 is not helping you I usually set that to a minus number to allow the head to drop down


  • Moderator

    @ruhigundrelaxed said in help needed: first layer in midair (~.5mm):

    G30 ; home Z by probing the bed G30 P0 X0 Y165 Z-99999 ; probe near a leadscrew, half way along Y axis G30 P1 X280 Y165 Z-99999 S2 ; probe near a leadscrew and calibrate 2 motors

    It's generally a good idea to do another G30 at the center of the bed after doing the tilt correction, because the tilt correction changes the height of the bed slightly.


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