Annular snap in PP

[kraykaID]

I'm designing a consumer product involving an assembly joined by an annular snap fit. (The OD of the male annular ring is approx. 14mm so it's not a small part) The client is dead set on using Polyproplylene for all the parts in the assembly however I'm concerned that the snap will wear prematurely given the soft nature of PP. Will the snap fit be more effective if the male component is harder than the PP part is snapping into? If so, what engineering thermoplastic would you recommend? (keeping in mind that it needs to be a food-grade material).

Thanks in advance!

 

[Pud]

I think a lot more info is required here:

e.g. No of operations, snap hold parameters, is the PP Homo/Co polymer, and so on ad nauseum...

Have you googled for "Snap Fits in Polypropylene" or spoken to the PP manufacturers - they've usually got white coats standing around not doing much.

They too though, will need a lot more information.

Cheers

Harry

http://www.tynevalleyplastics.co.uk

 

[patprimmer]

I fully support all that Harry says.

In addition I very much doubt PP will fail because it is soft. It may fail for lack of flex mod or tensile or creep, but lots more info is required, including the environment of use.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[7338]

Check out Designing Plastic Parts for Assembly book at Amazon. It has step by step calculations for annular snap fits and many other types.

 

[unclesyd]

Here are two snap-fit calculators that may answer your question. There is also a Java calculator "Modulus" that I've lost the link to.

http://engr.bd.psu.edu/pkoch/plasticdesign/snap_calc.htm

http://www.sabic-ip.com/webtools/toolsHomePage.faces