Tolerance Stack Up Question

[sarah321]

I am performing a tolerance stack up on a indicator push button that when pushed compresses a micro-switch. I haven't done a tolerance stack up before, but understand the basic idea. The part I'm struggling with is that there are moving pieces in the stack up.

Both the plus-sign shaped ejector pin on the underside of the push button as well as the micro switch move. Any ideas?

 

[IRstuff]

What is the purpose of the tolerance stackup, bearing in mind that there are two constraints to be met? The moving part is irrelevant; you only care about the starting and ending positions.

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[SwinnyGG]

IR nailed as usual.

You analyze your stack in the down position and up position as necessary; tolerance stack ups aren't for parts in motion.

 

[FeX32]

Agree with both of the above.
But, you can include stackups (or statistical analysis methods) into analyzing motions. This is design for six sigma (DFSS).

For example, you can start with your basic force to displacement relations in your system and "bake in" the statistical variances in the contacts (tols, heat, etc.).
This approach can be quite useful.

 

[ProEpro]

If it helps push all the parts all the way up then all the way down and eliminate the gaps. This makes it easier to visualize.

 

[ctopher]

You attached a schematic. Do you have drawings of the parts with tolerances? Are you designing the parts?

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[tbuelna]

If the trip point of your limit switch is critical, you should provide some method for rigging the trip point in your assembly design.