×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Worst case means variable ? -Resultant condition

Worst case means variable ? -Resultant condition

Worst case means variable ? -Resultant condition

(OP)
Y14.5-1994 question:

I am sure I miss something, but I don't know what:

1.3.23 Resultant Condition. page 3

The variable boundary generated by the collective effects of a size
feature’s specified MMC or LMC material condition,
the geometric tolerance for that material condition,
the size tolerance, and the additional geometric tolerance
derived from the feature’s departure from its
specified material condition.

Appendix A - page 199
Resultant condition is introduced and explained as
a worst case inner locus or outer locus condition.



RE: Worst case means variable ? -Resultant condition

Worse case is different for a stud than it is for the hole the stud is to go in.

"Know the rules well, so you can break them effectively."
-Dalai Lama XIV

RE: Worst case means variable ? -Resultant condition

winksmileI don't know the answer, but let's say the question shows up on the certification exam -1994-:

What is RC:
a.) The variable boundary generated by the collective effects .............
b.) A worst case inner locus or outer locus condition.........................

The other options you could eliminate and does not have a AND b option:)


What would you do?

RE: Worst case means variable ? -Resultant condition

According to 2009 it is both: the single worst-case boundary generated by the collective effects etc., etc., etc.
So I would wait for 2009 exam.

RE: Worst case means variable ? -Resultant condition

I think you are wondering how it can be both Variable and Worst case?

The answer is the committee was not structured for workers on different sections to review each other's work. This introduced a number of conflicts, such as this one. In addition, they were adding definitions for cases that are of dubious value - such as resultant condition - for descriptive completeness. In this case, the Appendix writer's were wrong.

Looking at 2.11.2 and the associated figures 2-7 to 2-12 support that Resultant Condition varies based on the combination of feature 'actual mating envelope' (AME) and the affect the AME has on the available tolerance to describe the unreachable volume of the feature. For example - 2-7, External feature. The minimum size of the pin .29.5 and they subtract another 0.5 for position tolerance to leave 29.0, which is a diameter that would be perfectly positioned and still be inside the solid pin. Since it is inside the pin, it is unreachable.

The definitions flip for LMC. For no good reason they are not applicable to RFS.

RE: Worst case means variable ? -Resultant condition

It's interesting that between 1994 and 2009 the committee saw fit to not only redefine terminology to be completely different in meaning, but add some new terms.

1973 - basis
1982 = 9 years
1994 = 12 years
2009 = 15 years

Extrapolating, the next version will follow an 18 year gap -> 2027?

RE: Worst case means variable ? -Resultant condition

Keep in mind that appendices are not part of the official standard. So while a discrepancy is indeed strange, it's not a huge deal.
The definition of RC was changed in 2009 to be a worst-case constant value. So it's fun to talk about this in 1994, but they've cleaned it up so it's no longer an issue.

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

RE: Worst case means variable ? -Resultant condition

It isn't 'cleaned-up,' just a new, incompatible interpretation of RC relative to the previous version. Which itself isn't new; the Y14.5 committees have flip-flopped a number of times.

RE: Worst case means variable ? -Resultant condition

Well, good point. I meant that RC is now a constant value, although unlike VC it doesn't carry that constant over the full size range.
So it's constant because that's how they define it, not because of any inherent concept. Still a improvement, I would say.

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

RE: Worst case means variable ? -Resultant condition

It does now. There is only one value for RC, just like there is only one value for MMB. in 1994 RC varied as the size of the feature varied, while VC was constant. Now no VC and no variation.

What was puzzling was the lack of utility of the concept for Resultant Condition. They spent a lot of effort on it for 1994 and then threw most of that away, but there's no reason given to even have it.

RE: Worst case means variable ? -Resultant condition

[quote John-Paul Belanger][Keep in mind that appendices are not part of the official standard.]J-P,

Ref: certification exam:

Are you saying that you are not going to be tested from the appendix?

RE: Worst case means variable ? -Resultant condition

Quote:

What was puzzling was the lack of utility of the concept for Resultant Condition.
I wouldn't say that concept of RC has no utility. It is helpful in calculating some types of tolerance stacks (wall thickness), allowing one to side-step a full-blown spreadsheet method.

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

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources