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Effective Button

A project log for Interact

Physically interacting with the world can be extremely difficult for some. This project aims to make it a little easier.

Mike TurveyMike Turvey 08/03/2020 at 16:043 Comments

After dozens of revisions, I've got a button that I feel is getting pretty close to meeting all the requirements.  Here it is:

It's rather unassuming, but it is a highly reliable switch and takes only ~60g of force, with a uniformity of activation pressure across the top surface.  Mechanically, this seems a really good solution.

Here is a breakout of the various components:

And here's a picture of the cap holder, and cap insert placed in the cap before being screwed down to the base:

And with the cap holder in place: 

A key aspect to the "feel" of the switch is that when in its resting (non-pushed) state, the microswitch is already under some pressure, although not activated.  If you don't do this, the switch will feel "sloppy" and rattles around. I found this to be tough to achieve consistently and reliably because it requires component precisions that near the layer thickness of the 3d printer (empirically, somewhere in the neighborhood of ~0.1mm).

Discussions

Simon Merrett wrote 08/03/2020 at 18:55 point

It's intriguing - please would you share more pictures of e.g. the inside of the cap or partially assembled so the principle of operation is apparent?

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Mike Turvey wrote 08/03/2020 at 19:41 point

Sorry about that.  There were supposed to be more pictures in this log that appear to have been dropped when I posted it.  I don't see a way to edit the log above, so I just posted a new one with pictures attached.  And definitely more to come.  This has been a really interesting project for me-- the tolerances ended up being a lot tighter than I expected.  That said, I've been impressed at what a 3D printer can reliably spit out.

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Simon Merrett wrote 08/03/2020 at 19:59 point

Ok, I think there should be an edit button near the log title. Thanks! I wonder which parts of the tolerances are most critical and whether continued design refinement could remove some dependence on material or process tolerance. For example, if it's the height of a part that is critical, can it be made from sheet stock of that thickness to start with? Not a suggestion but an illustration of what I mean. Looking forward to more logs too.

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