Probing speed with analog piezo sensor



  • I have a D-Bot corexy printer with Duet2 Wifi/Duex2 and currently running RRF3beta12.

    I have just upgraded my Precision Piezo Universal PCB to the latest V2.85 which has both a digital and analog output. The digital output works as before and I can probe at 6mm/s with these settings

    M558 P8 C"!zprobe.in" R0.5 H3 F360 T9000 A5 S0.03   
    G31 X0 Y0 Z-0.1 P100  
    

    When I switch to the analog output I change the settings to

    M558 P1 C"^!zprobe.in" R0.5 H5 F360 T9000 A5 S0.03 
    G31 X0 Y0 Z-0.1 P540  
    

    (The DWC z probe reads 529 most of the time)

    It works but the 6mm/s requested results in an actual 2mm/s which is painfully slow.
    I have read in other posts that the probing speed is reduced to 1/3 for analog probes but this isn't appropriate for piezo probes. I have tried increasing the probing speed x3 but I then have to increase the z max speed to 18mm/s which is too high for the z axis. I get a 6mm/s probe followed by an 18mm/s bed down movement.
    Increasing the G31 P540 to P590 seems to disable the 1/3 speed reduction for some reason but then the probe doesn't always trigger causing bed crashes.
    It would be good if there was a way of permanently disabling the 1/3 speed reduction.
    Has anyone else experienced this with the PP 2.85 board?


  • administrators

    @tekkydave said in Probing speed with analog piezo sensor:

    It works but the 6mm/s requested results in an actual 2mm/s which is painfully slow.

    That's because with analog probes, RRF slows down probing to 1/3 speed when the reading gets close to the threshold, exactly as you said. What's the reason for not using it in digital mode?



  • Only the convenience of having the trigger level adjustment in the Duet rather than the fiddly pots on the pcb.



  • Is the 1/3 slowdown something specific of RRF3? I can't say I'm experiencing it on RRF2 but could be wrong



  • @matt3o said in Probing speed with analog piezo sensor:

    Is the 1/3 slowdown something specific of RRF3? I can't say I'm experiencing it on RRF2 but could be wrong

    It's been around for an awfully long time - at least 2 years.



  • I can see the sense in the slowdown for other analog sensors but not for piezos. The analog output is constant until the nozzle makes contact with the bed.
    Can I suggest 2 possible solutions:

    1. A way of specifying the amount of slowdown for analog sensors in M558
    2. A separate M558 probe type for piezo probes with no slowdown applied.

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