FMEA - what does it stand for?
failure mode effects analysis
PFMEA vs. DFMEA
Process / Design
what is FMEA?
a step-by-step approach for identifying all possible failures in a design, a manufacturing process, a product, or a service
FMEA’s are the foundation for..
for Process Control Plans required by ISO/TS16949
“Failure Mode”
the way, or mode, in which something can fail. failures are errors or defects, especially those that affect the customer, and can be potential or actual
Effects analysis
- studying the consequences of those failures
- these systems do not assure failure can not occur but provide a structured assessment of risk
- when risk is properly assessed, actions must be implemented to reduce risk to define threshold levels
With GM’s current safety recall, which system failed: PFMEA or DFMEA?
DFMEA
failures are prioritized according to:
- how serious the consequence of failure (severity)
- how frequently they occur (occurrence)
- likelihood of detection (detection)
purpose of FMEA
to take action to eliminate or reduce failures, beginning with the highest-priority failures
where did FMEA originate?
originated in the 1940’s by US military. FMEA’s were further developed by the aerospace and automotive industries
PFMEA steps
- before developing PFMEA’s, teams should be selected and a process map developed
- list process steps in first column of form
- for each process step, brainstorm a list of potential failure modes (ways in which product/service might fail)
- identify potential effects for each failure mode: rate
- identify potential causes of failure modes and rate likelihood of occurrence
- list controls in place and rate ability of the control to detect the failure mode
- multiply three ratings
- result is Risk Priority Number (RPN) with 1000 as worst case
- identify improvement actions to reduce/eliminate risk associated with high RPN’s
- recalculate RPN, verify RPN is at or below threshold
Develop criteria…
tailored to the specific operation for rating the three factors to reduce subjectivity and inconsistency of the rating teams
error/mistake proofing
error proof - defect cannot occur
mistake proof - detect can occur but will be detected in station
causes of errors/mistakes
4 M’s - man, material, machine, method
error proofing
- ideal, this is what you want
- designing a potential failure or cause of failure out of a product or process
- defect cannot occur - prevention
mistake proofing
- change to design or process that helps the operator reduce/eliminate defects or prevent defect from continuing downstream
- detection in station
error/mistake proofing categories (in order of effectiveness - most effective first)
- error proofing: product/process design
- mistake proofing: control, warning, operational
- detection (out of station) - automated, manual (in zone), manual (after zone)
- procedural: visual aid/procedure
Mistake proofing control
- automatically shuts down an operation to prevent defects from continuing in process
- process stopped when defect detected
Mistake proofing warning
warning (visible, audible) to the operator of the defect or incorrect process
Mistake Proofing Operational
- parts color coded, stamped/marked, or has distinguished feature
- part selection lights
- part presentation
Detection: automated vs. manual
- automated: equipment used to detect defects by automated means in next station or after
- manual (in/out of zone): defect by visual means after offending process in and outside of the zone/department
Procedural: work instruction/visual aid
visual aid used on work instruction (selecting correct parts, orientation, sequence and example of good vs. bad)
Process FMEA
- improves likelihood of designing an error out of a product or process
- reduce defects or detect defects before affecting customer
5 why problem solving
reduce problems by root cause analysis with EMP strategies
