Flexible component with profile of surface

[Sa-Ro]

Hi

My requirement:

This is a flexible rubber component used for sealing purpose.

The part variation shall be within 0.2 boundary from true geometry (Symmetrically disposed)

Did I represented correctly?

Thank you

 

[Wuzhee]

No. The profile callout is just hanging there not attached to anything. If you want to control the deviation you should establish a datum system according to your requirements.

 

[Sa-Ro]

@ Wuzhee

Kindly refer the attached ASME Y14.5:2018 standard.

As per the standard we can mentioned profile tolerance without leader line.

My understanding: Since it is a flexible part, even if we provide datum, we can not hold the datum.

So I mentioned like true profile variation shall be within 0.2 boundary.

Thank you.

 

[Wuzhee]

That is a common practice to make a general callout in a title block that UOS All dimensions are basic followed by profile callout. In that case there is usually an ABC datum system.

What's not common practice is to just throw a fcf in the middle of nowhere and not stating that's a general callout.

 

[Sa-Ro]

OK. So profile tol shall be specified with general note + FCF + datum.

Without general note and datum, profile tol should not use.

Am I right?

Provided profile tol with leader and all around symbol.

 

[Wuzhee]

I'd prefer the all over symbol because it's a cylindrical part. But I'm not sure if the 'all around' profile applied to the section affects the whole revolution of the part.

 

[Sa-Ro]

OK. Thank you

 

[Belanger]

If this is a flexible rubber part, can 0.2 mm be reliably held in the free state? (Check out paragraph 4.1 and then paragraph 7.20 and its sub-paragraphs from the Y14.5-2018 standard.)
Of course, it depends on the function and rigidity of the part -- I'm tossing tossing the idea out there.

Also...another way to accomplish your need is the "all over" modifier for profile. That doesn't need any datum references; see paragraph 11.3.1.5 and Fig. 11-10 from the same standard.

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

 

[Sa-Ro]

@Belanger

In fig 11-10, FCF is attached to drawing.

Can I place the FCF without datum in general note?

Thank you

 

[Wuzhee]

Please refer to 11.2.3 Profile Tolerances as General Requirements
When the profile tolerance feature control frame is placed in a general note or the general tolerance block, the tolerance applies to all features UOS.

For the sake of clarity, you can add a note like this:
UOS ALL SURFACES ARE DEFINED BY: |profile|0.2| ALL OVER

But be aware that profile without datums is form control only.

 

[Sa-Ro]

@Wuzhee

Thank you for your valuable input.

I will use datum with all over.

 

[Belanger]

Drop the datum. If the profile is all over, then it already encompasses the datum feature surface. Thus, all surfaces are inherently toleranced to each other (for form, location, orientation, and size).

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

 

[Sa-Ro]

@Belanger

Updated as per your suggestion

Thank you.