I'm designing a plastic smartwatch. Is it possible to use ordinary watch pushers?

[CarolinaBrunch]

Hello all. I'm a mechanical engineer working on a smartwatch design for a startup. Any chance I could seek some advice from you folks in the watch repair community?

Specifically, I'm having trouble finding a good source of information for how to design a water-resistant button for our smartwatch. After doing some digging, I'm thinking that the best solution might be to design the smartwatch case so that I can install an ordinary chronograph pusher into it.

A few questions I have. If you can help me address any of these, I'd be quite grateful!

• Can pusher tubes be installed into a plastic watch case? The resources I can find all talk about installing pushers into metal watches.
• If they can be installed into a plastic watch case, do press-fit type pushers work in plastic? How about screw-in? Or will either work in a plastic watch case?
• Anything I should bear in mind for the assembly process? We're making relatively low quantities, so it's OK if the process is somewhat labor-intensive.
• Any suggestions for pusher manufacturers that I might be able to reach out to?

Please forgive me if I'm using any terminology incorrectly, by the way. I'm a new arrival in the horology universe.

In case it's relevant, our minimum requirement is to achieve water resistance only down to 1 meter (an IP67 rating). If we can pull off 50 meters / 5 ATM without too much additional pain/cost though, that would be incredible.

Thanks for your time!

Edited March 25, 2021 by CarolinaBrunch

[Graziano]

Hi there CarolinaBrunch, good on you for taking on such a project and good luck. Have a read of this article so that you understand what a water resistant pusher looks like and operates.https://watchesbysjx.com/2018/05/the-beginners-guide-to-water-resistance-and-wristwatches.html. I say yes you can have metal pushers in a composition case. Maybe not plastic as such. I know that you are trying too keep cost down but you need the case to be strong. There are many watch companies over the years that have used different case materials such as fibreglass and other types of composite materials, aluminium, carbon fibre etc and yes they have achieved water resistance. So I say yes to metal pushers not plastic pushers. May be check out what other materials they have these days for the case that is long lasting and inexpensive. As for supply of pushers. I dare say you would be best to select the most appropriate pusher for your design of watch and source direct from a supplier or watch material house , which there are plenty of all over the world. (well almost), here is one with some pushers http://www.ofrei.com/page525.html , keep searching the internet and mix it with your imagination and you will find what you need. Oh and just letting you know that the buttons should not be pushed under water as you can introduce moisture into the case. 

Good luck hope this helps 

Graziano 

Edited March 25, 2021 by Graziano

[spectre6000]

With a plastic case, I think it's safe to say you're chasing a price point. Chinese suppliers are the place to be. I once spent a few lockdown weeks casually scrolling through Ali-X looking at all the mechanical watches for sale in the evenings. Tens of thousands of them, [i]maybe[/i] low six figures, all shockingly inexpensive. They're essentially all permutations on the same relatively small catalog of available parts. Chrono cases are available all day long on Ali-X/baba. 7750 is the movement you're going to find them designed for, as it's the most common chronograph movement (mechanical anyway). Another good movement/case option to chase to find pushers (still mechanical) would be the Sea Gull ST1901; it's the absolute cheapest mechanical chrono on the market, and powers probably every mechanical chronograph on the market under $1K. Find a case seller, figure out who the actual manufacturer is, then contact them and inquire about just pushers, and I guess pusher tubes (basic procurement tango). Quartz pushers would be even cheaper, and again that price point, but I personally don't pay any attention to quartz watches and wouldn't know where to point you there other than the same general place/strategy. 

A word of warning on the case material: watch cases take a serious beating. They get caught on doors, countertops, smashed into brick/stone walls. It's brutal. Sapphire crystals are a thing because the plastic and glass ones just don't last long before they get pretty sad looking. I'm not aware of any plastic formulation that's going to handle that very well for very long. Add steel pusher tubes to the mix (drastically different and superior material properties in all but cost)... Catch a pusher on much anything, and that plastic case is going to crack in a hurry. The scratches and dings from daily use will make it look terrible even quicker. Smart watches tend to be pretty disposable though, and price points being what they are, that arbitrage may be desirable. Like Graziano said though, every material under the sun has been used (including cheese, for real but not for serious), and stainless steel is the gold standard by a mile.

[jdm]

10 hours ago, CarolinaBrunch said:

Hello all. I'm a mechanical engineer working on a smartwatch design for a startup.

Have you taken apart any smartwatch, or any watch with pushers of the price range your are aiming for? That will give you an idea how things are done, and sealing is typically achieved. And you can verify the manuf. claims with a testing macchine which up to 6 bar is not too expensive. By the way in the watch industty IP ratings are not used, as there are is a dedicated standard

https://en.wikipedia.org/wiki/Water_Resistant_mark

Then when you will contact the companies in China/Hong Kong that actually manufacture the watch you will receive samples and can have a bit of technical discussion on what difference, if any, you will want on your product.