FMEA-Eng-3-8-00

• Detection, can it be detected if it goes wrong.
– P-Type controls- Preventing it from happening. – D- Type controls - Detect it if goes wrong.
Potential Cause of Failure
FMEA Purpose
• To reduce product or service concerns and to minimize the probability of defective product reaching the customer. • To identify potential failure modes and to rate the severity of their effects. • To identify the critical characteristics of the product or process. • To rank the order of potential design and process defects.
– – – – Next user. Ultimate user or customer. Product operation. Government regulations.
Severity Definition
• Severity is the assessment of the failure effects on the process as well as the product. • Severity rating apply to the effects and the effects only. • Severity assessment is focusing on both the process / operation and the product. • All causes of a failure mode having the same effect should be assigned the same severity ranking. • Severity ranking scale goes from 1 to 10.
RPN
Recommended Actions
Section 1: What Is FMEA
What is FMEA
• FMEA is the prefix of Potential Failure Mode and Effects Analysis. The word potential is omitted. • FMEA is a systematic method which identifies potential product problems in the following areas. – Product design. – Product manufacture. – Product use. • FMEA is developed by Chrysler,Ford,General Motors . • FMEA including DFMEA--Design FMEA & PFMEA--Process FMEA. • Based on SAE product characteristic, we will study PFMEA detailedly.
– Two Types of failure modes. • Failure to perform the required function. • Performs function poorly. • Performs a function that is not supposed to be there.
FMEA History
• Mid -60‟s: Started in the Aerospace Industries. • 1974: Navy created FMEA Standard. • 1976: US Department of Defense adopted an FMEA standard. • Late 70‟s: Automotive Industries started to use FMEA. • Early 80‟s: Micro Electronic Industry started to apply FMEA to assist in improving the “yield of memory devices”. • Mid 80‟s: Automotive industries started to apply FMEA to the manufacturing processes. • 90‟s: TQS 9000 recommended adoption of FMEA.
FMEA application in SAE
• Nonconforming prevention and correction • Failure analysis • QCC tools, major cause confirmation, action taking,and effect comparison • Others engineering area
Effects
• An effect of the failure mode that would be noticed or experienced at the next operation, at a subsequent operation, by any downstream user. • Consider:
Section 3: Elementary Concepts of FMEA
FMEA Concepts
• Function, what is supposed to happen here.
– What is the product or process objective.
• Failure Mode, what can go wrong here.
Current Controls
• Current controls are intended to prevent the cause of the failure from occurring, to detect the cause if it should occur, and to reduce the impacts of the failure effects. – For example: • SPC. • Fixture fool proofing. • Process DOE. • SE. approval. • Production validation. • Preventive maintenance program. • Gauge R-R study. • Operator training.
Process PFMEA Analysis Sheet
PFMEA
Process Analyzed _________________
Function
Potential Effect of Failure Mode Failure
Severity Cause of Occurrence Current Detection Failure Rate Process (1 - 10) (1- 10) Controls (1 - 10)
• Cause, how can it go wrong.
– Four types of possible causes. • Design related. • Manufacturing process related. • Application related. • Service related.
FMEA Concepts
• Effect, what happens when it goes wrong:
– Design possible effects. • Product end user. • Local user. • Other, in between users. – Process possible effects. • The product effects. • Process effects.
Failure Mode Sa rating corresponding to the seriousness of the effect of the potential failure mode. Severity Description (1) No effect on the system performance. (2) Very slight Effect. Nuisance fault noticed. (3) Slight Effect. Nuisance fault obvious. (4) Minor Effect. Chronic nuisance fault. (5) Moderate Effect. Nuisance repair required. (6) Significant Effect. Repair required. (7) Major Effect. Rework /repairs required. (8) Serious Effect. Equipment/very dissatisfied customer. (9) Very Serious Effect. Stop ship required. (10) Hazardous Effect, sudden failure , or non-compliance to regulations or liability issue.
• List all possible conceivable causes of each failure mode. • The list should be complete as possible so that corrective actions can be implemented effectively and timely. • It must be a process or manufacturing cause. • Use as much detail as possible to define the cause of the failure. • Consider: – Method, machinery, materials, people and environment.