Plastic detent design-help!

[bluly]

Hello everyone.

I have been tasked with designing some new detented handles/knobs for some of our products at work. To be clear, i'm talking about the "click" feature you feel when rotating a knob such as a fan control in a car. Our products currently use plastic injection molded handles/knobs with spring/ball style detents with a mild steel plate on the other side.

Please see this link:
http://www.anemo.eu/products/vlier-machine-parts/plungers/mating-part-design-guidelines

I have been able to find a lot of information regarding hinged snap fit feature design, but nothing for plastic detents that would replace the feature described in the link above. I have the following questions:

Am I using the correct terminology? Is it referred to as "detents" in the plastic injection molding world?
What materials are best in this sort of application? I'm assuming some sort of nylon 6/6 for both mating parts?
Does anyone have a link to a design guide for these features?

Thanks in advance. :cool:

[Suhas]

Hello Bluly,
There are no hard and fast rules of what they are called. I see what you are asking for and I think in plastics there are different ways to achieve the same 'click' you are looking for. Going with a ball mechanism will get expensive and complicated. I suggest that you look at some existing similar parts. You will find that the balls are molded in making it easier. You care correct on the materials, but that will also depend on the loads. Nylons and Acetals are used.
Regards,
Suhas

[bluly]

Suhas,

Thanks for the reply! Do you have any links to examples? Maybe a design guide? such as proper interference fits and preload force for molded in ball detents?

[Suhas]

I don't have a guide. You may have to just look around, sorry my friend. If I find something I will let you know.
Suhas

[katie87]

Oh sorry friends, I have no knowledge about plastic detent design. If I find any kind of information I will let you know.

[brentb]

Start here:

http://plastics.dupont.com/plastics/pdflit/americas/general/H76838.pdf

and Keep on Molding

brent

[foxconnmold]

Start here:

http://plastics.dupont.com/plastics/pdflit/americas/general/H76838.pdf

and Keep on Molding

brent
Thanks brentb sharing pdf,I'm still not very understanding of your position on the plastic design knowledge.

[Suhas]

Brent,
I think this is an EXCELLENT resource you pointed out to. I hope more people use this.
Thanks again!
Suhas

[4efkko]

Hi bluly,

Were you ever able to find a solution to this problem/task? I'm looking to accomplish the same thing and would appreciate anything to point me in the right direction.

I'm looking for a way to try to re-engineer my plastic part to work without threading in an outside part (spring/ball plunger detent).

Basically I'd like to eliminate the following part:
http://www.carrlane.com/catalog/index.cfm/27825071F0B221118070C1C513E111D081B0006280B1713050 245221E0107070F1A3C3B285350435D
possibly by creating bendable plastic arms that snap into the button as opposed to continually buying that part to install into my plastic part.

If anyone else could offer help as well, anything would be much appreciated.

Thanks in advance for anything that might help!

[JayDub]

What materials are best in this sort of application? I'm assuming some sort of nylon 6/6 for both mating parts?

:cool:

I can't help with design inforation, but I would strongly suggest using different materials for the mating parts. As with metals, using the same material for two components that move against each other creates a worst-case situation for abrasion. I believe using nylon for one part and acetal for the other is a common choice.