Precision Piezo z probes guide for duet users reference



  • @DjDemonD:

    Plasticmetal- hmm yes i don't know why I posted that, must have been tired and looking at the wrong message. Show us a photo of your setup especially where the piezo is mounted. First thing to try is reversing the polarity of the piezo disc by flipping the plug around at the piezo pcb.

    Agniusm - make sure the red led is on by tuning vr2 (or the single pot if its a later revision), then use I1 in M558 (which is active low, the default mode for the latest piezo boards). It should be - red LED on until the piezo is bent/squeezed then it changes to blue for 0.25 seconds. There's nothing wrong with using Z1 (although it's technically deprecated after 1.19) but if homing with a piezo probe you are better off homing x and y then using G30. You might need to change threshold in G31 P…. or consider using M558 P5 mode or P8 mode which I find less difficult to work with.

    I have red light and when i touch the nozzle blue comes on without any force. When i home Z it digs into the bed, and stays there. It should just touch it and back off as i understand which is not happening.

    I now tried M558 P1, P5 and P8
    P8 brings manual leveling dialog in web interface and P1 and P5 acts the same.
    I have more recent board with 1 pot and if i adjust it to sensitive it triggers on the start with error message



  • Components are 50% off in Maplins as part of the closing down sale ;(
    I picked up a couple of spare Piezo's today for 75p
    The price reductions have put them closer to online prices, ironically, I've never seen the Oxford Street store so busy at a lunchtime



  • @Agniusm:

    @DjDemonD:

    Plasticmetal- hmm yes i don't know why I posted that, must have been tired and looking at the wrong message. Show us a photo of your setup especially where the piezo is mounted. First thing to try is reversing the polarity of the piezo disc by flipping the plug around at the piezo pcb.

    Agniusm - make sure the red led is on by tuning vr2 (or the single pot if its a later revision), then use I1 in M558 (which is active low, the default mode for the latest piezo boards). It should be - red LED on until the piezo is bent/squeezed then it changes to blue for 0.25 seconds. There's nothing wrong with using Z1 (although it's technically deprecated after 1.19) but if homing with a piezo probe you are better off homing x and y then using G30. You might need to change threshold in G31 P…. or consider using M558 P5 mode or P8 mode which I find less difficult to work with.

    I have red light and when i touch the nozzle blue comes on without any force. When i home Z it digs into the bed, and stays there. It should just touch it and back off as i understand which is not happening.

    I now tried M558 P1, P5 and P8
    P8 brings manual leveling dialog in web interface and P1 and P5 acts the same.
    I have more recent board with 1 pot and if i adjust it to sensitive it triggers on the start with error message

    Okay so on your duet web control, when you tap the sensor and the light changes from red to blue with light force, what does the z-probe box say? It should say 0 (if on p5/p8) then 1000 when triggered, or if on P1 it might read something around 200-300 open and then rise to 700+ triggered.

    P8 bringing up the manual levelling dialogue in DWC suggests a software or config problem as that should not happen. Are you using the z-probe connector on the duet? and have you verified the wiring is correct?

    Please also do this polarity verification test "push up on the (cold) nozzle (not tap) see what happens, then release the pressure. If it triggers on push it's correct if it triggers on release the polarity is reversed of the piezo disc.



  • So, it seems I've gotten mine into a working state now. Haven't printed yet, as I'm also moving the extruders around to install Capricorn tubing. This is a SeeMeCNC Rostock delta V2, with Hayden's mag arms, PEI adhered to boro glass, on 7mm MIC-6 aluminum bed.

    In a nutshell (these steps were actually many, many iterations and trying other things):

    1. Piezo seemed far too sensitive to any movement at all
    2. VR1 to positive pin was 500K ohms, adjusted down to about 230K (decreasing sensitivity)
    3. Adjusted VR2 to ever so slightly beyond where the red LED just comes on (decreasing sensitivity)
    4. Went round and round with P5 (digital) settings, ultimately went with P1 (analog), matching kraeger's experience with the same printer
    5. Due to my machine's specific Frankenstein collection of mods, re-arranged wiring going to effector

    Relevant config.g lines:

    M201 X1000 Y1000 Z200 E1000		
    M558 P1 I1 R1 F300 H5 T2400
    G31 X0 Y0 Z-0.1 P400
    
    

    Z acceleration ended up at 200 mm/sec, and the P (threshold) became 400. The resting Z-probe value (as shown in the DWC) is 340. I tried P360, but the box turned green and deviation increased. I think P380 was also flaky, so I stuck with 400 - it's enough of a difference from the resting value to require a distinct tap, but still low enough to be reasonably sensitive. I could likely reduce the R (pause) value, but it's pretty insignificant. As I haven't printed yet, I haven't adjusted the G31 Z offset value.

    My deviation at 90mm radius is 0.04, which isn't great (and slightly worse than what I can get with the Smart Effector), but I believe that's due to the mount, not the sensor. This is without any H offsets in the bed.g file. That's a time-consuming process, that I'm putting off for now.



  • I'm glad it's working and that you've dialled it in.

    I'm not sure h values are really that applicable since there is no difference to measure between the trigger height and the actual nozzle to bed gap as they are coincident and basically 0. That's not to say the effector isn't tilting to some degree and on some (probably most) setups, but I imagine the effect is just that the nozzle prints nicely onto the bed at extreme coordinates, but at 89 or so degrees to the bed rather than 90.



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  • Hey, again. The piezo was working fine for several builds / hours, but then one day suddenly reverted to being overly sensitive again. I checked that the resistance measurements on both trimpots hadn't changed, and then went back as I had previously done to dial back the sensitivity.

    That worked for a few days, but then the oddity occurred again, but this time it suddenly became very insensitive. In both cases, I know of nothing that would have caused the changes. Both times, I was printing fine the day before, and when I went to start a print the next day, the problems were immediately there. There's been no change in the mount, possible disturbances or damage to the printer, no one has touched it, etc.

    It seems as though there might be a cracked or poor solder connection somewhere. As I had posted earlier in this thread (14 March), I've never measured 10K from VR1 to a negative connection - always 0.5 or less. No one commented on that, so perhaps that's not an issue.

    Any ideas?



  • I'll get Idris to chime in on this one.



  • @plasticmetal said in Precision Piezo z probes guide for duet users reference:

    changes. Both times, I was printing fine the day before, and when I went to start a print the next day, the problems were immediately there. There's been no change in the mount, possible disturbances or damage to the printer, no one has touched it, etc.

    That's very odd behaviour, it suggests that VR1 is occasionally going open circuit. Are you able to measure the resistance between PZ+ and PZ- while turning VR1 (gently) from one end of it's travel to the other?

    Can you drop me a PM or a message on the website with your order number, I may need to send you a replacement.

    Idris



  • @moriquendi said in

    Can you drop me a PM or a message on the website with your order number, I may need to send you a replacement.

    I've sent a message via your website. Thanks!



  • Hi @DjDemonD ,

    I have recently installed an Orion on my Kossel XL and would like to make a modified version of the groovemount part. Is it possible to obtain the STL for that please? Even better would be an scad file if that's available.

    Thanks,

    Mark



  • Hi Mark,

    STLs can be found here, let me know if you need anything else.

    Idris


 

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