Risk Priority Number
Special Process Characteristics
Special Product Characteristics
Cause: A Cause is the means by which a particular element of the design or process results in a Failure Mode.
Critical Characteristics are Special Characteristics defined by Ford Motor Company that affect customer safety and/or could result in non-compliance with government regulations and thus require special controls to ensure 100% compliance.
Criticality: The Criticality rating is the mathematical product of the Severity and Occurrence ratings.
Criticality = (S) ׳ (O). This number is used to place priority on items that require additional quality planning.
Current Controls (design and process) are the mechanisms that prevent the Cause of the Failure
Mode from occurring, or which detect the failure before it reaches the Customer.
Customer: Customers are internal and external departments, people, and processes that will be adversely affected by product failure.
Detection: Detection is an assessment of the likelihood that the
Current Controls (design and process) will detect the
Cause of the Failure Mode or the Failure Mode itself, thus preventing it from reaching the Customer.
Effect: An Effect is an adverse consequence that the Customer might experience. The Customer could be the next operation, subsequent operations, or the end user.
Failure Mode: Failure Modes are sometimes described as categories of failure. A potential Failure Mode describes the way in which a product or process could fail to perform its desired function (design intent or performance requirements) as described by the needs, wants, and expectations of the internal and external Customers.
FMEA Element: FMEA elements are identified or analyzed in the FMEA process. Common examples are Functions, Failure
Modes, Causes, Effects, Controls, and Actions. FMEA elements appear as column headings in the output form.
Function: A Function could be any intended purpose of a product or process. FMEA functions are best described in verbnoun format with engineering specifications.
Occurrence: Occurrence is an assessment of the likelihood that a particular Cause will happen and result in the Failure
Mode during the intended life and use of the product.
The Risk Priority Number is a mathematical product of the numerical Severity, Occurrence, and Detection ratings. RPN = (S) (O) (D). This number is used to place priority on items than require additional quality planning.
Severity: Severity is an assessment of how serious the Effect of the potential Failure Mode is on the Customer.
Significant Characteristics are Special Characteristics defined by Ford Motor Company as characteristics that significantly affect customer satisfaction and require quality planning to ensure acceptable levels of capability.
Special Process Characteristics are process characteristics for which variation must be controlled to some target value to ensure that variation in a
Special Product Characteristic is maintained to its target value during manufacturing and assembly.
Special Product Characteristics are product characteristics for which reasonably anticipated variation could significantly affect a product’s safety or compliance with governmental standards or
regulations, or is likely to significantly affect customer satisfaction with a product.
8-D Eight Disciplines of Problem Solving
AIAG Automotive Industry Action Group
APQP Advanced Product Quality Planning
ASQC American Society for Quality Control
DOE Design of Experiments
FMEA Potential Failure Mode and Effects Analysis
FTA Fault Tree Analysis
ISO International Organization for Standardization
QFD Quality Function Deployment
QOS Quality Operating System
RFTA Reverse Fault Tree Analysis
RPN Risk Priority Number
SPC Statistical Process Control