AVTC Model Based Design
Curriculum Development
Project
DFMEA
Module 5
Introduction to DFMEA
• Design Failure Mode and Effects
Analysis
• Use of DFMEA
– New designs
– Modifications to current designs
– Use of a current design in a new
environment, place or application
• Why?
– To understand failures that may happen
in an electric motor.
Source: www.kookerkids.com/Coloring/computers.computer_trouble.htm
Characteristics of DFMEA
• Minimizes probability of a failure, or to minimize its effects
• Should be initiated before, at design concept finalization, or
before production starts
• Continuous iterative process
• Provides a system to document processes and designs
• DFMEA evaluates the faults of a product as a consequence of
design weaknesses
• Problems or failures normally arise during production stage,
but originate during planning and designing of the product
DFMEA Purpose
• DFMEA is an application of the Failure Mode and Effects
Analysis (FMEA) method specific to product design
Durability and Reliability.
Past FMEAs, field Data
Potential
Failure Mode
Parts List
Name and
Component
Part No.
Design
Requirements
Component
Function
Data
Product Specs
Potential
Failure
Effects
Remediation
& Product
Improvement
Process and Product
Historic Data:
Potential
Failure
Causes
DFMEA Process
1.
2.
3.
4.
5.
6.
Identify the components of a product
Identify possible failures and their effects
Assess severity of potential failure and causes of failure
Assess potential frequency of occurrence
Identify detection modes
Assess the detection of the failure. Calculate risk priority number
(RPN = severity * occurrence * detection)
7. For potential failures with highest RPN, create mitigation plans
8. Once actions have been taken, recalculate the RPN to confirm
failure risk has been reduced
Line No:
DFMEA for Manual Transmission
Function of Part
Potential
Failure
Mode
Potential Effects
of Failure
Mounts :
To hold
transmission
system
Breakage or
rust due to
moisture
Abnormal noise
and vibration
Aging of
seal or
gasket
Oil leaks
2
Transmission
housing:
To hold gear oil
Improper
shifting of
gears
Shifting hard or
not possible
3
Clutch:
Engage and
disengaging of
engine to drive
transmission
1
SEV
Potential
Cause
4
Loose or
broken
transmission
and engine
mounts
3
Damaged oil
seal or
gasket
5
Clutch plate
worn
4
5
Throw out
bearing
failure
OCC
Current Design
Controls
Prevention
DET
RPN
2
16
2
30
3
60
3
30
Tighten or
replace mounts
2
Replace
2
Replace clutch
Replace throw
out bearing
Line No:
DFMEA for Automatic Transmission
Potential
Failure
Mode
Potential
Effects of
Failure
SEV
Oil pump:
provide
1 hydraulic
pressure
Reduced
pressure
Transmission
inoperative
5
Brakeband:
Clamp
2
planetary
gear
Wear on
band
Transmission
fail to shift
Valve body:
route fluid
Fluid
blockage
Fail to shift
gears
Planetary
gears
Gear
teeth
breakage
Transmission
inoperative
3
4
Function of
Part
4
8
6
8
Potential
Cause
Bearing failure
Seal leak
Excessive
torque
ATF
contamination
from
overheating
Excessive
torque, load
and duration
too long
Current Design
Prevention
Controls
Current Design
Detection
Controls
2
Visual
Inspection
Function test
2
Visual
inspection
Function test
Visual
inspection
Function Test
for band
slipping
Replace fluid
and filter
Inspect fluid
and filter
Minimize
excessive
loads,
especially
towing
ATF at
excessive
temperature
OCC
3
3
2
DET
RPN
5
50
5
40
3
72
4
72
3
48
Line No:
DFMEA for Continuous Variable Transmission
1
2
Potential
Failure
Mode
Potential
Effects of
Failure
Driven
Pulley
Pulley flange
become
loose or
cracked
Pulley
transmission
stop working
Belt
Become
loose, worn,
or break
Transmission
could stop
working
Function
of Part
SEV
8
Potential
Cause
More stress
on pulley than
needed
More tension
than needed
OCC
Current Design
Detection
DET
Controls
RPN
3
Check periodically Inspection
if riveted flange
need
replacement
4
96
Replace belt
5
Check if belt
needs
replacement
periodically
4
160
Inspection
7
Minimize
excessive loads,
no towing
4
224
8
Excessive
torque from
load
Current Design
Prevention
Controls
References
• “Design Failure Modes Effects Analysis (DFMEA)”
http://www.clemson.edu/ces/crb/ece495/past_projects/MineSweeper/Fall2012/Gr
oup1/dfmea.pdf.
• “Failure Modes and Effects Analysis (FMEA),”
http://homepages.cae.wisc.edu/~me349/fmea/fmea_example4.pdf, 2000.
• Barry, Katy, “Avoid Failure When Using Failure Modes and Effects Analysis (FMEA), ”
iSixSigma, http://www.isixsigma.com/tools-templates/fmea/avoid-failure-whenusing-failure-modes-and-effects-analysis-fmea/, Aug. 2013.
• “FMEA Tutorial,” http://aaq.auburn.edu/node/501.
References
• “Automated Manual Transmission,” http://eex.gov.au/resource/potential-energyefficiency-opportunities-in-the-australian-road-and-rail-sectors/automated-manualtransmission/.
• T. Ma, “Model-Based Control Design and Experimental Validation of an Automated
Manual .
• Transmission,” M.S. thesis, Dept. of Mechanical Engineering, The Ohio State Univ.,
Columbus, OH, 2013,
https://etd.ohiolink.edu/rws_etd/document/get/osu1374198354/inline.
• “Failure Mode and Effects Analysis,” http://www.scribd.com/doc/90988964/FailureMode-and-Effects-Analysis.