audible snap design

[jweaver1244]

We are trying to design a plastic latch that, when assembled, gives a very distinct snap sound. Has anyone ever worked with different beam geometries/materials to optimize a snap sound? Weird question, I know. Thanks in advance.

 

[MikeHalloran]

I don't think snap noise is terribly sensitive to beam geometry or material.
You need a 'sounding board', as in a related surface being relatively large and flexible, so as to radiate the shock wave that travels through the plastic when the snap drops off the far side of the ramp.

Examine some children's toys. Not for snap fits; you know how to do that, or can find out. Look at the size and thickness of the acoustic radiating elements of toys that produce sound without electronics.





Mike Halloran
Pembroke Pines, FL, USA

 

[jweaver1244]

Thanks Mike, I had not thought of that (brain fade due to old age). Of course. I need gap on impacted surface. Now off to fit it in to the design. thanks.

 

[Jboezi]

I have worked for a client to modify their plastic snap geometry with the intent to reduce a "soft" click. They desired for a more crisp audible sound and strong tactile feedback. Unfortunately, there are too many variables in play to predict this behavior or prescribe a method to you. We established a number of variables we wanted to tweak and then made several prototypes modifying one variable at a time. As we learned which knobs and dials controlled different characteristics we made more iterations until the client was satisfied (in this case we were also constrained in many ways by the existing geometries of mating components and tooling).

Things to consider :
-Snap stiffness - material (elasticity), thickness, shape/ribbing
-Resonance (As Mike stated more completely above)
-Stiffness of mating parts or nearby parts - in a way you are trying to control which parts vibrate and which do not by designing the proper stiffness into each.
-Volume around snap and amount of material between snap and outer surface
-Ramp/Cam profile - what does your force curve look like? How much designed deflection is there?
-Creep, stress - Is your part loaded at rest leading to creep? Is your design stress too high during motion causing plastic deformation (usually due to too much deflection)?

Mechanical design engineer

http://www.johnboezi.com