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Snap fit features for round through holes

Snap fit features for round through holes

Snap fit features for round through holes

Just looking to see if anyone has any good links/design guides/feature details on snap fit features for locking into a round mating through hole. Like quarter round cantilever beams,etc...
Got an injection molded part to design that needs to snap fit onto a circuit board that will have round holes for attaching this plastic part.

parting line is going to be parallel with the mating plane of the circuit board. We tend to avoid side actions/inserts,etc.. if possible to attempt to keep tooling cost low.

Could do ultrasonic,etc.. welding of a simple round pin but we just don't have the tooling for that and I'd prefer just a snap fit feature vs welding,etc...
99% of the time its a one time use feature so welding could be done but I'd like to leave the option open to be able to remove it for rework,etc... fasteners are out too..

RE: Snap fit features for round through holes

I would suggest looking at PCB standoffs... they have snap-on versions that sounds like exactly what you want. Two prongs, separated by a cut down the middle, they squeeze together to allow the board to pass over them.

Dan - Owner

RE: Snap fit features for round through holes

yes..fully aware of those and was the first place I looked.. Just want to incorporate those types of features.. But most/all of them have the parting line running along the axis of the standoff making those features simple.. I don't necessarily have that luxury.. but still early in the design process so that could change.
Working on a quarter round cantilever now that seems to work ok..
Something about the "square peg into a round hole" like with a traditional beam hook just doesn't sit right with me..

Just seemed like every design guide,etc.. I came across looking for inspiration was all about square into square and virtually nothing about round locking features.

RE: Snap fit features for round through holes

Much to my surprise, I find this design guide is still around: Ticona



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RE: Snap fit features for round through holes

Talk to your molder. (S)he may have some favorite trick detail that will do what you want.

Remember that molded parts are still hot and pliable when the mold opens, so it is possible to do gentle reverse tapers without side pulls.

A stepped hollow boss with a gentle taper in the regular direction, and an interference fit at the board plane, can be used to retain a board that's not subject to military class vibration. You might need a tubular tool to fully seat the board against the step, but it shouldn't take a lot of force.

Same geometry without the interference fit can work, using a soldering iron with a slightly special tip to flare the boss' tip down over the board.

Mike Halloran
Pembroke Pines, FL, USA

RE: Snap fit features for round through holes

Thanks for the info.. just lets me know I was already headed in the right directions.
I've got that Ticona guide in my "library" already too.. Its a great brief but "all encompassing" document.

RE: Snap fit features for round through holes

I have a Bayer design guide titled Snap-Fit Joints for Plastics. It has a lot of different types of snap fits. I did not search to see if there is a newer version.


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