Precision Piezo z probe advice for custom hotend



  • Hi!

    I plan to make a water-cooled hotend. The water-cooled block (in blue on last view) will be made in 3D-printed metal (on Sculpteo), and all will be mounted on a 3mm aluminium metal sheet.

    I would like to use piezo probe(s) for precise Z homing. Could you advice me how could I integrate the piezo disc(s) on my design?

    Thanks,






  • Hi Frederick. This could be easy or complex.

    Just before we start trying to figure it out what type of printer? Is using underbed sensors feasible? This would make the hotend less complex.



  • If I'm reading your pictures correctly the simplest option, so probably the first one to try, would be to put a drilled piezo disk between the waterblock (blue) and the waterblock mount (green?). You might need to modify the shape of the parts to support the piezo disk around the rim and apply force on the centre.

    Other options include putting drilled disks between the waterblock mount and the aluminium sheet or modifying the aluminium sheet to allow controlled flex and bonding piezo disks where the flex is concentrated.

    As Simon suggests, underbed sensors can be the easiest option if you want to avoid complexity in the hotend.

    Idris



  • This is a CoreXY; putting piezzo under bed is possible, but I don't have my final bed yet, so I don't know what it will look like.

    Idris, you're right, a drilled disc at the top of the cooling block should work fine, and is easy to manage. I'll first try this solution.

    Thanks!

    PS: I also need to buy the electronic…



  • I use underbed on my corexy (disc stuffed in TPU feet) and this works good, no need for a complex hotend!



  • Well, underbed solution is not that simple, and require more piezo discs.

    About piezo discs, I read there are different types, some can be tight and still deliver the same signal only depend on the pressure variation. Where can I buy such discs in Europe?

    Thanks,



  • I buy murata 20cm disks from mouser.



  • There are different types of piezo disk but our system is designed to work with the type of disk that is used in piezo buzzers. These piezo disks (usually the Murata 7BB series) will produce a usable signal if they are bent or through a change in pressure. We sell everything you'll need, including piezo disks, on our website https://www.precisionpiezo.co.uk/shop

    Idris



  • Ok, I'll give a try with this discs.

    BTW, which PCB should I buy? The 'Piezo20 PCB v1.1', or the 'Universal Piezo Z-Probe PCB v2.x'?



  • Universal kit system is more versatile especially for anything custom like this. The Piezo20 pcb has evolved into something that only really suits the Piezo20 module design or very close derivatives.



  • Ok!

    About pressure on the disc, should I design the top mount so it as a large surface on the piezo disc (white part), or is something like only 3 pressure points better?



  • For best sensitivity support the disc on one side on its periphery and push into the centre from the other side. Evenly spread compression work but is slightly less sensitive.



  • The problem is I need to keep the disc compressed so the hotend does not move…



  • You can preload them quite a lot, the signal is produced on change so even a heavily preloaded disc generates a rising voltage on further bending/compression. Our circuit is a differentiator in part so it looks for change in voltage. Even small rises generate triggers.



  • Good! Thanks.


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