Critical Dimension 9

[rnanj001]

Hi,
I am a QA Engineer and i have to highlight the critical dimension on the Mechanical drawing for QA Incoming Inspection, so that the QA Incoming inspector can inspect only those dimensions to accept or reject the part. My question is, what is considered as "Critical Dimension" and how should i select it. Any information reqarding this subject will be greatly appreciated.

 

[tz101]

My comment about working in a vacuum was only directed at a single person, based on the quote I included with my post.

 

[ewh]

tz101,
Well, since you have seen fit to point your finger at me, just let me say that some people can be of the opinion that over 30 years experience, starting on the board, moving on to CAD not too long after it first appeared, supervising drafting departments, and spending a dozen years contracting at various companies across the south US could be considered "working in a vacuum", but IMO that it is not an accurate assessment.
Please don't take your frustrations out on those of us about which you know little or nothing. Not all industries or companies follow the same practices in this regard, and I am offended at your knee-jerk reaction at being exposed to experiences other than your own with which you may disagree (you know, those occurring in that vacuum). Just because other methods have been common in your experience does not mean that they are the only allowable (or preferable, depending) methods used.
There are good and valid reasons for using differing methods, but product definition does not have to be one of them. Product definition is just that, not process definition which statistical methods tend to direct.
I still stand by my statement with which you seen to have taken offense.


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

 

[fcsuper]

The term "critical" is misapplied when being applied to dimensions. Dimensions are a definition of the product. Asking which ones are critical versus other ones is a bit like asking which words in this sentence are critical to this sentence's meaning.

Criticality is determined by experience with the product. What are the specifications that the vendor finds challenging? Where have failures occurred?

If you want a starting point, you can use crutches, like defaulting to dimensions that define features that mate with other parts.

On molded products, you can determine "process control" dimensions; these are dimensions that are nominally no more important than any other dimension, but can serve as an indication as to the overall compliance of the product.


Matt Lorono, CSWP
Product Definition Specialist, DS SolidWorks Corp
Personal sites:
Lorono's SolidWorks Resources & SolidWorks Legion