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Precision Piezo z probes guide for duet users reference

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  • undefined
    SuperJETT
    last edited by 13 Nov 2017, 01:33

    Ah, now I finally figured it out after some confidence from your post. I had it all configured but when I was issuing G30 earlier after already doing it once, I'd get Error: Z probe was not triggered during probing move which means I needed to override the Z position.

    Custom CoreXY at home with Duet Wifi, Hemera

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    • undefined
      SuperJETT
      last edited by 13 Nov 2017, 02:53

      A bit of interest.
      https://www.facebook.com/groups/makerbot/permalink/1442086032575563/

      Thanks DJ for helping me out so quickly.

      Now I just have to implement it into my printing.

      Custom CoreXY at home with Duet Wifi, Hemera

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      • undefined
        Lakko
        last edited by 27 Nov 2017, 16:51

        Hi,
        I have a D-BOT coreXY (30x30x30cm), i've purchased the precise piezo last week and it is on its way.
        While i'm waiting for it i want to prepare the firmware.
        So in Z probe section of config.g i've put the digital code:

        M558 P5 I0 R0.4 F300 X0 Y0 Z1        ; Digital Z probe, also used for homing the Z axis
        G31 X0 Y0 Z-0.1 P100				 ; Set the probe height
        
        

        i would like to use the piezo also for the z home in z min so i put "Z1 in M558".

        These are my homez.g and homeall.g:

        ;**********************************
        ;homeall.g
        ;homing using a x-MIN, Y-MAX and z-MIN endstops
        ;**********************************
        
        G91                       ; relative mode
        G1 Z4 F400 	          ; lowers bed 4mm to avoid dragging nozzle over the bed
        G1 S1 X-340 Y340 F2000    ; move 340/340mm in -X (x endstop is MIN) and +Y(y endstop is MAX)
        G1 S1 X-340               ; course home X
        G1 S1 Y340                ; course home Y
        G1 X4 Y-4 F500             ; move away from the endstops
        G1 S1 X-10                ; fine home X
        G1 S1 Y10                ; fine home Y
        
        G1 Z4 F200                ; lowers bed 4mm to avoid dragging nozzle over the bed
        G90                       ; back to absolute mode
        G1 X150 Y150 F4000        ; put head over the centre of the bed, or wherever you want to probe
        G30                       ; probe
        G91                       ; relative mode
        G1 Z4 F50                 ; move slowly 4mm in the +Z direction
        G90                       ; back to absolute mode
        G30                       ; probe
        
        
        ;**********************************
        ; homez.g
        ;homing using a z-MIN endstop
        ;**********************************
        
        G91                       ; relative mode
        G1 Z4 F200                ; lowers bed 4mm to avoid dragging nozzle over the bed
        G90                       ; back to absolute mode
        G1 X150 Y150 F4000        ; put head over the centre of the bed, or wherever you want to probe
        G30                       ; probe
        G91                       ; relative mode
        G1 Z4 F50                 ; move slowly 4mm in the +Z direction
        G90                       ; back to absolute mode
        G30                       ; probe
        
        

        and in my starting code i put this to perform the bed leveling/compensation:

        M561                      ; Cancel any existing bed compensation by sending 
        M557 X10:290 Y10:290 S40  ; Define the probing grid
        G29                       ; Probe the bed and save height map to SD
        ;M190 S[70]               ; i don't have a bed heater 
        M109 S130          ; set 130 extruder temp
        G28                       ; home axes
        
        

        Is this correct or i have to change something?
        Any advice and suggestions will be greatly appreciated

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        • undefined
          DjDemonD
          last edited by 27 Nov 2017, 18:55

          Looks okay to me, but then I'm not so good at just eyeballing it and spotting errors, just use low motor current at first so any crashes just stall the z motor, not do any damage. And tune the piezo carefully, so that a gentle tap up triggers it, and you see the trigger on DWC screen in Z-probe box goes red and says 1000.

          The do G30 with nozzle way above the bed, tap up with your finger or a tool, to make sure the firmware registers triggered and reacts to it before trying it on your bed.

          Then hit home all and go from there. But I'd say you are well prepared.

          Simon. Precision Piezo Z-Probe Technology
          www.precisionpiezo.co.uk
          PT1000 cartridge sensors NOW IN, just attach to your Duet board directly!

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          • undefined
            deckingman
            last edited by 27 Nov 2017, 19:49

            I don't have a Piezo probe so can't comment on your homez.g but your homeall.g file has errors related to homing Y.

            I note that the Y end stop is at Y max so the course homing part is fine but after this:
            G1 S1 Y340 ; course home Y
            you have this:
            G1 X4 Y4 F500 ; move away from the endstops
            G1 S1 X-10 ; fine home X
            G1 S1 Y-10 ; fine home Y

            In the first line above you want to move Y away from the end stop but it's already at max (Y=340 from the previous course home) so to move it away from the end stop, you need to move it negative i.e G1 X4 Y-4 F500 (Y minus 4)
            Then you have G1 S1 X-10 which is fine but G1 S1 Y-10 is wrong as it'll be moving away from the end stop so it needs to be G1 S1 Y10 (no minus sign).

            What will happen if you don't correct this is that course homing will work fine, then fine homing of X will work but after that, Y will move slowly away from the end stop (towards you) and keep going for ever (or at least until something nasty happens).

            HTH

            Ian
            https://somei3deas.wordpress.com/
            https://www.youtube.com/@deckingman

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            • undefined
              Lakko
              last edited by 12 Apr 2017, 11:23 28 Nov 2017, 13:17

              Ok, thank you! I have edited the homeall.g code.
              When the piezo arrive i will edit all the code so it can maybe help someone else and use it for a starter point.

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              • undefined
                vbtalent
                last edited by 29 Dec 2017, 15:01

                I'm wanting to replace my Z axis home switch on my CoreXY, Z home's at the top.

                M558 P0 X0 Y0 Z0 H5 F120 T6000
                
                

                I think I need the following in my config.g,

                M558 (P1/P5) I1 R0.4 F300 X0 Y0 Z0
                G31 X0 Y0 Z-0.1 P600
                
                

                I'm using the v2 PCB in a NC configuration. I'm also unclear what the difference is between the analog/digital and what it is used for? Does the board still need to be tuned in a digital usage or is that irrelevant?

                I also am a little confused on the homing sequence. I think I need to home X/Y then move to the center of the bed and run a G30, is this correct?

                Appreciate some help.. thanks.

                ampapa,

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                • undefined
                  DjDemonD
                  last edited by 29 Dec 2017, 18:59

                  You need to tune the PCB first whatever method you use this sets up the pcb to trigger when the nozzle is tapped. This sets up the sensor itself. If it's the v2 kit it triggers active low I1 if it's the Piezo20 unit it triggers active high I0 in M558.

                  Next step is setup how your printer will use this information.

                  Analogue mode (not present on most other lesser 3d printer controllers) allows you to set a threshold, if you are over it the firmware considers the z probe triggered, so you can use M558 P1…... As you have shown. Set the threshold for 500 and see how you go, you can raise it or lower it to change sensitivity. You can see the current value in the Z-probe box on DWC or paneldue.

                  You can also make it more or less sensitive on the piezo pcb read the instructions see www.precisionpiezo.co.uk on how to do it as this is not duet/RRF specific but applies to any setup.

                  Digital mode P5 is how most other 3d printer controllers run endstops and sensors either on or off. In this mode a change from 0v to more than 1.65v on the z probe signal wire (or 3.3v to less than 1.65v if using active low mode) will be considered a trigger (its probably more complicated than that but that's the gist of it). So use this mode if you prefer (I do). If using P5 then there is no adjustable threshold, as the threshold is fixed, as described above. But you can debounce the signal by filtering it slightly and that's what the G31 Pxxx refers to when P5 mode is chosen in M558. 100ms seems to be the right value.

                  There is also a P8 mode on 1.20 firmware which removes filtering and is digital like P5, so that you get more precision, once you have got your system working smoothly using P1 or P5 try it instead, but you'll only notice the improvement when doing sensor testing and using high microstepping.

                  Simon. Precision Piezo Z-Probe Technology
                  www.precisionpiezo.co.uk
                  PT1000 cartridge sensors NOW IN, just attach to your Duet board directly!

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                  • undefined
                    vbtalent
                    last edited by 1 Jan 2018, 14:28 29 Dec 2017, 19:43

                    Thanks for the quick feedback DjDemon.

                    I ran a first test with the unit and it seems to be working correctly.

                    https://youtu.be/rqbH40s8HNE

                    In my homing files (homez/homeall) what would that look like now, something like the following?

                    ORIGINAL homez.g

                    G91                ; Relative positioning
                    G1 Z-350 S1 F300   ; Move Z down until the switch triggers
                    G1 Z2.5 F300
                    G1 Z-5 S1 F150     ; Move Z down until the switch triggers
                    G1 Z2.5 F150
                    G90                ; Back to absolute positioning
                    G92 Z2.5           ; Tell the firmware where we ar
                    
                    

                    NEW homez.g

                    G91                       ; relative mode
                    G1 Z4 F200                ; lowers bed 4mm to avoid dragging nozzle over the bed
                    G90                       ; back to absolute mode
                    G1 X150 Y150 F4000        ; put head over the centre of the bed, or wherever you want to probe
                    G30                       ; probe
                    G91                       ; relative mode
                    G1 Z4 F50                 ; move slowly 4mm in the +Z direction
                    G90                       ; back to absolute mode
                    G30                       ; probe
                    G1 Z2.5 F150
                    G90                ; Back to absolute positioning
                    
                    

                    EDIT

                    Just wanted to close the loop on this and post my working Z homing file.

                    G91                     ; relative mode
                    G1 Z4 F400              ; lowers bed 4mm to avoid dragging nozzle over the bed
                    G90                     ; back to absolute mode
                    G1 X40 Y265 F4000       ; put head over the center of the bed, or wherever you want to probe
                    G30                     ; probe
                    G91                     ; relative mode
                    G1 Z4 F150              ; move slowly 4mm in the +Z direction
                    G90                     ; back to absolute mode
                    G30                     ; probe
                    G1 Z2.5 F150		;Move Z to 2.5 above the bed
                    G90  			;back to absolute
                    G1 X0 F4000 		;move to X0
                    
                    
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                    • undefined
                      DjDemonD
                      last edited by 29 Dec 2017, 21:09

                      Yes that should work.

                      Simon. Precision Piezo Z-Probe Technology
                      www.precisionpiezo.co.uk
                      PT1000 cartridge sensors NOW IN, just attach to your Duet board directly!

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                      • undefined
                        vbtalent
                        last edited by 1 Jan 2018, 13:00

                        One additional follow up question on setting the Z axis positioning.

                        [c]G31 X0 Y0 Z-0.1 P600[/c]

                        If the piezo is effectively able to find Z=0 then why the need for an offset in the config.g file? Is this to force the probe to go below the bed surface?

                        When the probe touches the bed surface shouldn't that effectively be the Z=0, no offset is needed from that point forward?

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                        • undefined
                          DjDemonD
                          last edited by 1 Jan 2018, 13:40 1 Jan 2018, 13:37

                          Great question. If the probe could do it's job with 0.1g of force then you'd be right z=0 would be 0mm above the bed. But it takes about 10g-15g which means the piezo disc deflects about 0.1-0.15mm before triggering. Effectively it triggers below the bed. So the offset is -0.1mm to -0.15mm.

                          The good news is that it's consistent so determine your offset by babystepping your first layer until it's perfect (assuming really good extruder calibration) then reverse the sign and change your G31 offset. So if you babystep up 0.05 then subtract 0.05 from G31 Z and vice versa.

                          Simon. Precision Piezo Z-Probe Technology
                          www.precisionpiezo.co.uk
                          PT1000 cartridge sensors NOW IN, just attach to your Duet board directly!

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                          • undefined
                            vbtalent
                            last edited by 1 Jan 2018, 14:41

                            After homing, assuming I'm using -.01 as posted above my control panel shows Z at -0.1 that assumes a deflection of the piezo if I understand you post correctly. The -0.1 is then adjusted based on baby stepping and printing of the 1st layer and ultimately could be less or more and that actual number should be reflected in the config.g file, correct?

                            So in Slic3r I need a Z offset that reflects that actual number +/-… I think I understand.

                            Thanks,

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                            • undefined
                              DjDemonD
                              last edited by DjDemonD 4 Dec 2018, 19:00 1 Jan 2018, 15:03

                              So if the offset is -0.1 in G31 after homing your DWC/paneldue/M114 will show Z=0, but the actual nozzle will be either too close or too far away from the bed.

                              You then babystep on your first print, record the amount you babystepped then reverse the sign and add it to the G31 offset. I use the first layer solid infill as my visual guide, if its got lines between the extrusion then its too high, if it piles up its too low, but this method relies on precise extruder calibration (and a precise extruder) to be accurate.

                              So just to be super clear

                              When its too low and you have to increase gap between nozzle and bed.
                              Initial G31 Z Offset -0.1
                              Babystep Amount 0.05 (up)
                              New G31 Z offset -0.15

                              When its too high and you have to decrease gap between nozzle and bed.
                              Initial G31 Z Offset -0.1
                              Babystep Amount -0.05 (down)
                              New G31 Z offset -0.05

                              If you prefer you could put feeler gauges under the nozzle and measure it that way, or jog up and down and measure it. But if its too low this isn't going to be practical.

                              Simon. Precision Piezo Z-Probe Technology
                              www.precisionpiezo.co.uk
                              PT1000 cartridge sensors NOW IN, just attach to your Duet board directly!

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                              • undefined
                                Cinpro
                                last edited by 9 Jan 2018, 01:34

                                I have a bit of a SNAFU on my install. in the DWC it reads 1000 in red. when I use a meter on the PCB it reads the opposite of what is listed in the directions. the Positive reads 10 Kohms and the Negative reads 4.4 Mohms.

                                M558 P1 I1 R0.8 F300 X0 Y0 Z0 H5 F120 T6000 ; Set Z probe type to unmodulated, the axes for which it is used and the probe + travel speeds
                                G31 X0 Y0 Z-0.1 ; Set Z probe trigger value, offset and trigger height
                                M557 X40:285 Y20:310 S20 ; Define mesh grid

                                on the Duet board I am plugged into the Z-Probe spot +3.3, GND and Z Probe IN

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                                • whosrdaddyundefined
                                  whosrdaddy
                                  last edited by 9 Jan 2018, 08:21

                                  Use P5 (or P8 if you are on a recent firmware) and use E0 endstop input, also set Z to 1:

                                  M558 P8 I1 R0.8 X0 Y0 Z1 H5 F300 T6000 (use I0 if you are using a v1 board)

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                                  • undefined
                                    Cinpro
                                    last edited by 9 Jan 2018, 20:57

                                    I have it set like in your example, except for the Z1. I don't plan to use it to home since my hot-end parks off to the side and doesn't touch the bed. Just to clarify, you are using the E0 endstop for all the wires, and not the Z-probe socket on the board beside the Panel Due socket?

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                                    • undefined
                                      DjDemonD
                                      last edited by 1 Oct 2018, 17:45 10 Jan 2018, 17:08

                                      Hi guys sorry for the slow response. Using the z probe connector is no issue. If the DWC or paneldue shows 1000 when the probe is open/untriggered, then just change the M558 I parameter from I1 to I0 or vice versa.

                                      What version of piezo device are you using? If correctly set up (red light on until triggered) a V2 universal kit board will output an active low signal (also called NC or inverted 3.3v open and nearer to 0v triggered). This offers failsafe operation in that a wire break between piezo pcb and the duet controller will show as triggered and therefore avoid a head crash. Upcoming versions of the piezo PCB (anything with V2) will work this way. Use I1.

                                      Currently, Piezo20 PCBs (which are v1) and the original V1.x universal kit PCBs operate with the blue LED off when open, it comes on momentarily when triggered, these devices, are active high (NO or 0v open and 3.3v triggered). Use I0. No failsafe, so when commisioning, use low motor current to avoid head crash issues.

                                      You can set up a v1 universal PCB inverted by moving VR2 until its just past the point where the blue LED comes ON and leaving it there, use I1 in this mode. But please DO NOT set up a Piezo20 PCB (the small one with one piezo connector) in this mode as it might burn out the blue LED (although this is less likely with 3.3v than with 5v.

                                      The piezo20 PCB piezo connector is wrongly labelled, so ignore the + and -, however this sometimes has to be the case as not every piezo disc is correctly polarised. The only reliable test (without a scope) is to push up on the nozzle (or down on the bed for underbed) not tap, and see if it triggers when you push. Then release the pressure, see if it triggers when you release. If it triggers on push it's correct, if it triggers on release its the wrong polarity, just turn the piezo disc plug to the piezo PCB the other way, retune and try again. If it helps when I build the ready-to-run units using genuine Murata 7bb piezos the black lead from the piezo goes to the upper pin (nearest the outside of the PCB), most of the time, but occasionally I find an inverted piezo disc.

                                      Simon. Precision Piezo Z-Probe Technology
                                      www.precisionpiezo.co.uk
                                      PT1000 cartridge sensors NOW IN, just attach to your Duet board directly!

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                                      • undefined
                                        rmriggin
                                        last edited by 2 Feb 2018, 22:00

                                        I have an odd issue in that if I have anything connected to the VIN pin on any endstop or the probe connector the duet becomes unresponsive until I unplug the VIN wire regardless of using the VIN pin on the z endstop connection or the z probe connection. Any ideas?

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                                        • undefined
                                          S1lencer
                                          last edited by 3 Feb 2018, 15:08

                                          Sounds to me like you have the polarity on youre piezo board not in the right order,
                                          please check if you got the signal and graund the right way around.

                                          mfg
                                          Kai

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