Need help on Tolerance stackup

[amitpaul713]

Hi,

Please find the attachment of the aprt. I am really struggling to perform stackup on this. Please help

Regards,
Paul

 

[Oaklandishh]

I am pretty sure that you are missing information about size tolerances of each component part depending on what stack-up you want to figure out. Can you provide more info?

 

[drawoh]

amitpaul713,

What are you trying to figure out? I think you are missing info too.

--
JHG

 

[amitpaul713]

Hi,

I am trying to figure out the gap between the end of (1) and the portion of (6) which is outside, and it would finally help me to get the overall length (OAL) (which is what I am calculating by worstcase and later RSS). The problem I am actually facing here is, the dimensions 2.18 and 2.58 overlaps, I really did not come across this situation until now. What approach should I have to stackup incase of overlaping dimensions. Please find the attachment for the gap for your convenience. Thanks.

Regards,
Paul

 

[JNieman]

You need to know more information about the conical tapers including their location, size, form, and controls/tolerances of all of those.

 

[Belanger]

You need to think about whether you want to find the maximum or minimum distance that you've highlighted in red. Based on that, you would then envision the parts moved to their extreme positions (assuming there is any movement or "play" at all) to achieve that desired max or min.

Once that is done, you would start at the right side of component 1 and draw a path of vectors which eventually lead to the right side of component 6. This is the most important part of a stack -- chaining these vectors together, and this path has to go through the contact points where the various parts touch.

Based upon that you can then add up the appropriate numbers. But again, don't try to do the math until you first create the stack path. And that's just for one extreme; to find the other extreme (max or min) you would jiggle the parts again and probably get a totally different stack path.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[3DDave]

The stack of variation requires accounting for the hoop strain in the needle cover and in the needle base. It also includes the hoop strain in the needle base and in the syringe end.

These will be affected by the allowed assembly loads and their variation and the amount of friction at the interfaces.

 

[amitpaul713]

Hi,

The stackup is to be done at an initial stage i.e there would be no movement (of the plunger rod) at all. And there is no load as well. What I want is to create a stack path and calculate thereafter, but the problem is 2.18 and 2.58 is overlapping. So in this case how do I approach for creating the path or loop or chain as you say.
Please find the attachment as an example but without having any overlaps. Thanks

Regards,
Paul

 

[3DDave]

You can't.

 

[amitpaul713]

Hi 3DDave,

Thanks for the confirmation, could you please tell me if there is any other way out?

Regards,
Paul

 

[JNieman]

You can't figure out how to get from points A -> B -> C -> D if they don't tell you the length of segment B-C.