3. Implicaciones de la filosofía de Wittgenstein para la educación
3.4. Aportaciones wittgensteinianas a la comprensión de la memoria: revisando la
Following the steps previously outlined that described the planning functions preceding an FMEA, the analysis proceeds as the FMEA team completes appro-priate documentation, such as the FMEA form. For purposes of this discussion, one form applicable to either a design or process FMEA will be described. Where the criteria change between a design or process FMEA, both criteria will be pro-vided. Figures 20.13 and 20.14 are blank FMEA forms applicable to design and process FMEA—each component of the forms will be identified and described.
P ar t III .E .4
Item Function Potential failure mode Potential effect(s) of failure Current design controls Responsibility and target completion date
Potential cause(s)/ mechanism(s) of failure Recommended action(s)
S e v
C l a s s
O c c u r
D e t e c
R. P. N.S e vO c cD e tR. P. N.
Action results Actions taken
System Subsystem Component Model year(s) vehicle(s) Core team Design responsibility Key date Prepared by FMEA date (orig.) (rev.) FMEA number Page of
Potential Failure Mode and Effects Analysis (Design FMEA) Figure 20.13Blank design FMEA form.
P ar t III .E .4
Process function Requirements Potential failure mode Potential effect(s) of failure Current process controls Responsibility and target completion date
Potential cause(s)/ mechanism(s) of failure Recommended action(s)
S e v
C l a s s
O c c u r
D e t e c
R. P. N.S e vO c cD e tR. P. N.
Action results Actions taken
Item Model year(s) vehicle(s) Core team Process responsibility Key date Prepared by FMEA date (orig.) (rev.) FMEA number Page of
Potential Failure Mode and Effects Analysis (Process FMEA) Figure 20.14Blank process FMEA form.
P ar t III .E .4
Heading Information and Documentation
Product or process name Provide the formal and/or commonly used (if different) name for the product or process.
Product or process Provide a brief description of the product description or process that is meaningful to the FMEA
team members.
FMEA number Assign an FMEA number to each FMEA for tracking and documentation purposes.
There are no standards for numbering FMEAs; however, a numbering system that links the FMEA to a specific period of time and product/process family is preferred.
Design/process owner Identify the individual or team assigned primary responsibility for the design or process for tracking and documentation purposes. This individual or team is also identified for reference, if needed, during the FMEA.
FMEA team leader Identify the individual assigned primary responsibility for completion of the FMEA for documentation purposes. This individual is also identified so as to establish a point of contact should any stakeholder need information during or after the FMEA.
FMEA team List each member of the FMEA team along with any key responsibilities relative to the FMEA.
FMEA date Provide the date(s) during which the FMEA is completed to help establish a chronology of events. Revision dates should be noted here as well.
FMEA risk assessment Indicate the basis of the risk assessment.
The FMEA risk assessment may be based on either actual failures or failure causes. It is important to document the team’s decision to assess risk based on failures or causes to ensure that everyone evaluating the FMEA understands exactly how risk was assessed.
Analysis Content and Documentation
DFMEA part name, Identify the product (that is, part name, number, function, or part number, and function) or process PFMEA process function (that is, functions to be completed as part
of the process).
P ar t III .E .4
Potential failure mode List each of the potential failure modes associated with the design or process. Design failure modes may include dented, deformed, fractured, loosened, leaking, warped, and so on. Process failure modes may include overheating, inoperable, visual defect, and so on.
Potential effect of For each potential failure mode, indicate the failure mode potential effect on customers or production/
process personnel—it is entirely possible to have multiple effects for each potential failure mode.
Severity Indicate the seriousness of the effect of the potential failure using the severity criteria defined in Tables 20.3 and 20.4. Note: The severity rating applies only to the effect of the potential failure.
Table 20.3 Design FMEA severity criteria.
Effect Severity criteria Ranking
Hazardous Very high ranking when potential failure mode affects safe 10 without operation and/or regulation noncompliance. Failure occurs
warning without warning.
Hazardous Very high ranking when potential failure mode affects safe 9 with warning operation and/or regulation noncompliance. Failure occurs
with warning.
Very high Item or product is inoperable, with loss of function. Customer 8
very dissatisfied.
High Item or product is operable, with loss of performance. 7
Customer dissatisfied.
Moderate Item or product is operable, but comfort/convenience items 6 inoperable. Customer experiences discomfort.
Low Item or product is operable, but with loss of performance of 5 comfort/convenience items. Customer has some dissatisfaction.
Very low Certain characteristics do not conform. Noticed by most 4 customers.
Minor Certain characteristics do not conform. Noticed by average 3 customers.
Very minor Certain characteristics do not conform. Noticed by 2
discriminating customers.
None No effect. 1
S × O × D = risk priority number (RPN) Derived from Technical Standard SAE J 1739.
Reprinted by permission of The Society of Automotive Engineers (SAE).
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Classification Classify any special characteristics that may require additional process controls. SAE J1739 identifies classifications that include critical, key, major, and significant.
Potential cause of For each potential effect of each failure mode, failure mode identify all possible causes—it is entirely
possible to have more than one cause for each potential effect.
Table 20.4 Process FMEA severity criteria.
Effect Severity criteria Ranking
Hazardous May endanger machine or assembly operator. Very high severity 10 without ranking when a potential failure mode affects safe operation and/
warning or involves noncompliance with regulation. Failure will occur without warning.
Hazardous May endanger machine or assembly operator. Very high severity 9 with ranking when a potential failure mode affects safe operation and/
warning or involves noncompliance with regulation. Failure will occur with warning.
Very high Major disruption to production line. 100% of product may have to 8 be scrapped. Item inoperable, loss of primary function. Customer
very dissatisfied.
High Minor disruption to production line. A portion of product may have 7 to be sorted and scrapped. Item operable, but at reduced level.
Customer dissatisfied.
Moderate Minor disruption to production line. A portion of product may have 6 to be scrapped (no sorting). Item operable, but some comfort items
inoperable. Customer experiences discomfort.
Low Minor disruption to production line. 100% of product may have to 5 be reworked. Item operable, but some comfort items operable at
reduced level of performance. Customer experiences some dissatisfaction.
Very low Minor disruption to production line. Product may have to be sorted 4 and a portion reworked. Minor adjustments do not conform.
Defect noticed by customer.
Minor Minor disruption to production line. Product may have to be 3 reworked online, but out of station. Minor adjustments do not
conform. Defect noticed by average customer.
Very minor Minor disruption to production line. Product may have to be 2 reworked online, but out of station. Minor adjustments do not
conform. Defect noticed by discriminating customer.
None No effect. 1
Derived from Technical Standard SAE J 1739.
Reprinted by permission of The Society of Automotive Engineers (SAE).
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Occurrence Indicate how frequently each failure is expected to occur using the occurrence criteria defined in Tables 20.5 and 20.6.
DFMEA design For a design FMEA, identify the actions verifications or PFMEA completed that ensure or verify the adequacy process controls of the design. For a current process FMEA,
identify the control currently in place that prevents a failure mode from occurring.
Table 20.5 Design FMEA occurrence criteria.
Probability of failure Possible failure rates Ranking
Very high: Failure almost inevitable > 1 in 2 10
1 in 3 9
High: Repeated failures 1 in 8 8
1 in 20 7
Moderate: Occasional failures 1 in 80 6
1 in 400 5
1 in 2000 4
Low: Relatively few failures 1 in 15,000 3
1 in 150,000 2
Remote: Failure is unlikely < 1 in 1,500,000 1
Derived from Technical Standard SAE J 1739.
Reprinted by permission of The Society of Automotive Engineers (SAE).
Table 20.6 Process FMEA occurrence criteria.
Probability of failure Possible failure rates Ranking
Very high: Failure almost inevitable. > 1 in 2 10
1 in 3 9
High: Generally associated with processes similar 1 in 8 8
to previous processes that have often failed. 1 in 20 7
Moderate: Generally associated with processes similar 1 in 80 6 to previous processes that have experienced occasional 1 in 400 5
failures. 1 in 2000 4
Low: Isolated failures associated with similar processes. 1 in 15,000 3 Very low: Only isolated failures associated with almost 1 in 150,000 2 identical processes.
Remote: Failure is unlikely. No failures associated < 1 in 1,500,000 1 with almost identical processes.
Derived from Technical Standard SAE J 1739.
Reprinted by permission of The Society of Automotive Engineers (SAE).
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Detection Indicate the ability of design verification or current process controls to detect a potential failure mode in the event that failure actually occurs. Use the detection criteria defined in Tables 20.7 and 20.8.
Risk priority number For each potential failure mode, multiply the (RPN) severity (S), occurrence (O), and detection (D)
assessments together. Since each scale (S, O, and D) ranges from 1 to 10, RPNmin = 1 and RPNmax = 1000.
Recommended actions For each potential failure mode, list one or more recommended corrective actions. For further direction and guidance on prioritizing recommended corrective actions, refer to the
“Taking Action Based on an RPN” section of this chapter.
Table 20.7 Design FMEA detection criteria.
Effect Detection criteria Ranking
Absolute Design control will not and/or cannot detect a potential cause/ 10 uncertainty mechanism and subsequent failure mode or there is no
design control.
Very remote Very remote chance the design control will detect a potential 9 cause/mechanism and subsequent failure mode.
Remote Remote chance the design control will detect a potential cause/ 8 mechanism and subsequent failure mode.
Very low Very low chance the design control will detect a potential cause/ 7 mechanism and subsequent failure mode.
Low Low chance the design control will detect a potential cause/ 6 mechanism and subsequent failure mode.
Moderate Moderate chance the design control will detect a potential 5 cause/mechanism and subsequent failure mode.
Moderately Moderately high chance the design control will detect a 4 high potential cause/mechanism and subsequent failure mode.
High High chance the design control will detect a potential cause/ 3 mechanism and subsequent failure mode.
Very high Very high chance the design control will detect a potential 2 cause/mechanism and subsequent failure mode.
Almost Design control will almost certainly detect a potential cause/ 1 certain mechanism and subsequent failure mode.
Derived from Technical Standard SAE J 1739.
Reprinted by permission of The Society of Automotive Engineers (SAE).
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Individual/team For each recommended action, assign an
responsible and appropriate individual or team and an expected completion date completion date.
Actions taken Provide a brief description of the actual actions taken and their respective action dates.
Resulting RPN analysis Following each action taken, reiterate the severity, occurrence, and detection assessments and calculate a new resulting RPN. Actions taken based on RPNs and resulting RPNs continue until the risk assessment for each potential failure is “acceptable” to the customer and/or authorizing agent for the FMEA.