Ball and socket snap fit 3

[HeavyRain]

I would like to know if anybody has an idea how to calculate all the parameters needed to properly design a ball and socket snap fit.
I have searched on the internet but I did not find any clear equation that explains the relation among the ball diameter, the socket diameter, the opening width and the material properties (I will use the ERTALYTE).

Thank you in advance for any proposition.

 

[Eltron]

You might try posting this in the Machines & Machining Forum: forum281.

Dan

http://www.eltronresearch.com

Dan's Blog

 

[MDGroup]

I don't think you're going to find anything online to give you the exact answer. Every situation is different based on different materials, different surface finishes, different sizes, how tight you want it to be, and the features of the socket (whether it is split or solid, how much rotation you need, and how easily/tightly you want it to move)

You are probably going to have to figure it out for yourself through trial and error with some prototypes.
If you are machining the parts, start with it overly tight, and then you can remove material a little bit at a time until you get the fit you want.
If you are molding the parts, start with it overly loose, and then you can remove material from the tool (making the part larger) until you get it where you need to be.

I can tell you that it doesn't take much interference to get a real solid fit, usually only a couple thousandths depending on the overall scale of what you are working on.
Also, make sure you understand the tolerances of how the parts are going to be made. Again, a couple thousandths could make a big difference.

Good Luck.

 

[HeavyRain]

Thank you Eltron and sorry for posting it in the wrong forum

 

[HeavyRain]

MDGroup, thank you for your answer. If there is no solution, I will be forced to make it according to you advice.

 

[tgrimley]

This is a good reference for ball and socket:

https://cdn.sparkfun.com/assets/home_page_posts/1/4/1/0/Plastic_Snap_fit_design.pdf

also, ertalyte is probably too brittle to do this with if you need a small part (low max strain). iirc ertalyte is similar to delrin af which you might be able to use in its place. just make sure you calculate max strain (including tolerances).

 

[MadMango]

Try searching for a PDF from Ticona, called Design Calculations for Snap Fit Joints in Plastic Parts. It is probably very close to what has already been suggested.

"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the best use of these Forums?

 

[HeavyRain]

Thank you all, it is so interesting as reference.

 

[loki3000]

use FEA. in the linear zone it's quite reliable, if you set the model correctly.

 

[HeavyRain]

Unfortunately, I don't have an license for ANSYS and it is so expensive.

 

[loki3000]

use solidworks simulation, creo simulation or similar software then.

 

[HeavyRain]

Do you think that such simulations are possible using Solidworks? do you have any tutorial about that?

 

[loki3000]

there are built-in tutorials, if you have solidworks simulation.
click options, add-ons, then check simulation. then look in help for them.