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I am designing a device which clicks when rotated so as to wake up an accelerometer, allowing the device to run on low power and wake to take a reading.

I have access to SLA and FDM 3D printers. When I design a disc with a notch in the sla printer the material is degraded over use and the click diminishes. The fdm printer suffers from accuracy for the dimensions used.

The outer disc is 3cm in diameter in which there is another disc that is 2.5cm in diameter. The requirement is to use the space in the middle to use any materials to create a satisfying click.

I have used

  1. notches which suffer from degradation
  2. A spring mounted in the outer and inner disc which pushes out a small piece of plastic but this keeps getting caught.
  3. Mounted a small push button switch in the inner ring but due to the square shape of the button part and rolling motion I get no click.
  4. Printed leaf spring but this does not have the potential energy to create the click.

Any ideas would be a great help?

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  • $\begingroup$ Igus makes a filament that is meant to be wear resistant. Though its a bit geometry dependent. $\endgroup$
    – joojaa
    Oct 25, 2023 at 20:17
  • $\begingroup$ Thanks @joojaa I will check it out but problem with FDM is the dimensional accuracy. $\endgroup$ Oct 25, 2023 at 22:25

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I assume you need quite a click to activate an accelerometer and 3D printers are not known for making very wear resistant components.

Making it simply an electrical contact wake-up might be in order then with a gentler spring for tactile feel. You can use a hammer punch to punch out copper or aluminum foil flat rings to embed inside channels in your 3D printed part to send the requires electrical currents around.

The other alternative is to put in bearing surfaces into your 3D printed parts so they abrade against each other and not the 3D printed plastic. For example, a bunch of sockets for ball bearings, with perhaps one spring loaded ball bearing opposite to click against.

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  • $\begingroup$ Thank you @DKNguyen. The issue with the metal contact is that the surface needs to be airtight and if I make many then the wirings and connections add a time overhead and quality would decrease with need for a lot of testing and tweaking. I have also considered reed switches but have up because the reeds behaved inconsistently when making a lot of units. I do like the idea of using ball bearings to stud the outside of one of the rings, even though it’s labour intensive for making many the quality will be easier to maintain, I could even insert these mid way through the printing process. $\endgroup$ Oct 25, 2023 at 22:34
  • $\begingroup$ Hi I found Threaded Ball Index Plungers - vital-parts.co.uk/… $\endgroup$ Oct 26, 2023 at 12:35
  • $\begingroup$ @JaspalSinghRathour There are solid-state magnetically activated switches. These are more sensitive and consistent than reed relays I imagine. $\endgroup$
    – DKNguyen
    Oct 26, 2023 at 17:59
  • $\begingroup$ If you're lucky you might find that a very strong magnet at the close distances involved might produce the detent you want against the steel balls, as well as having a magnetic field to activate a magnetic switch. Then you have no wear issues. $\endgroup$
    – DKNguyen
    Oct 26, 2023 at 18:47

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