Special Characteristics
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Special Characteristics – What is that?
• Characteristic or feature that require additional control(s)
in order to control excessive variation (Product & Process)
• Examples include:
• Product safety related characteristics
• Characteristics that control compliance to gov’t regulations
• Fit / Function related characteristics
• Customer defined Special Characteristics
• Characteristics which may not be identified or verified by the
direct customer but ultimately affect a subsequent operation or
customer (i.e., Pass-Through Characteristic)
• Previously known as CTQ (Critical to Quality)
• Legacy Cooper Power Systems terminology
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Special Characteristics – How do we use it?
• 3 Types of Special Characteristics (SC)
• 2 Design SC and 1 Process SC
• Communicated on Product Requirements such as:
• Part Drawings
• Specifications
Example
• DpFMEA / PpFMEA
• Process Control Plans
• Design Special Characteristics Categories
• Required Control Dimension (RCD)
• Statistically Toleranced Dimension (STD)
• Process Special Characteristic (no symbol)
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The correct answer is B. Characteristic or feature that requires
additional control(s). Additional control required because product or
process has excessive variation.
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Design Special Characteristics
• Required Control Dimension (RCD)
• Drawing symbol is octagon
on left hand side of requirement
• Designated as D in Control Plan
• Additional control or capability addressed through techniques
including 100% inspection, poke-yoke (error proofing)
• Applied for characteristics that use pass/fail criteria or attribute data
• Statistically Toleranced Dimension (STD)
• Drawing symbol is “wide” hexagon
•
on right hand side of rqmt
ASME Y14.5M ST symbol
• Designated as Dst in Control Plan
• Must demonstrate initial & ongoing process capability
• Require Process Capability Study and Measurement Systems
Analysis (Gage R&R)
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The correct answer is A.
The symbol for a Required Control
Dimension (RCD) Special Characteristic is an Octagon
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Requirements of Special Characteristics
• Total number of Special Characteristics on given document
shall be recorded
• All product requirements revised after January 1, 2015 shall have
either: SC=0 (indicates zero special characteristics) or SC=X
indicating total number of both RCD and STD characteristics
combined.
• External Products being re-sourced to a different supplier
that do not adhere to this policy should be re-submitted to
Engineering to be updated prior to official quoting by supplier
• Component or Assembly prints used by externally sourced suppliers
must have special characteristics evaluation prior to being quoted for
production
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The correct answer is D. SC = 6. The drawing or specification revised
should have total number or special characteristics. In this case, there are
2 RCDs and 4 STDs, which accounts for 6 total special characteristics.
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Special Characteristics – Why use it?
• Tells Eaton and Supplier what is the MOST important
about a product with respect to Quality, Customer, and
Performance
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© 2013 Eaton. All Rights Reserved..
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