Transcript Course Overview

Detailed Design—Managing
Risk in Product Design
Failure Modes and
Effects Analysis (FMEA)
Integrated Product and Process Design
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ME 476 Course Outcomes
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Integrated Product and Process Design
Today’s Objective
• Learn how to perform a basic
FMEA analysis to identify
critical risks that should be
addressed in a design
project…
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Integrated Product and Process Design
Presentation Outline
• What is Product
Quality?
• What is FMEA and
why and how is it
done?
• Record Book writing
exercise
• Learning from case
studies and failures
• Summary
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Firestone Tire
Integrated Product and Process Design
Quality…
So, What Does the phrase
Product
Quality Mean to you? Mean
mean to you?
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Product Recalls
• Century Infant Safety Seats/Carriers: when
used as a carrier, handle could break and allow
infant to fall to ground………
• Chrysler, Dodge and Plymouth Minivans: fuel
injector system could leak, possibly causing fire…
• Kent Kickin’ Racer Scooters: handlebar
problems could cause rider to lose control and
fall…..
• Consumer Reports: Infant Car seat failures
• ….
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Good Design Leads to Good Quality
• Good designs result from asking good design
questions and answering those questions well…
• Answering design questions well comes through
appropriate and wise use of:
- Good Analytical models
- Careful testing & experimentation
- Good use of other engineering tools
- Good engineering judgment
- From yourself
- From others
- Faith and hard work
- Other…….
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Integrated Product and Process Design
FMEA: Failure Modes and Effects Analysis
• A detailed design
process tool for
systematically
improving the
quality of products
and preventing
failures
• Part of a product
design quality
assurance plan
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Good Design Questions:
One very important
design question to
ask:
1. What might go
wrong with our
design?…
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Quality
Some define the term product quality as:
“A Product’s Characteristic of being fit for
use over time……”
Two significant design questions:
•
•
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What might go wrong with our design so that our
product’s fitness for use might be compromised?
What can we do now (during the detailed design
stages of the design process) to prevent this from
happening?
Integrated Product and Process Design
How Do I Do FMEA?
Identify all possible failure modes:
• Could result from design weaknesses…
• Could result from
manufacturing
or material problems…
• Could result from how
product is used…
• …
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Integrated Product and Process Design
How Do I Do FMEA?
All possible failure modes are identified and rated (110 scale; 1- low, 10-high), for three characteristics:
• Severity- Severe consequences get a high rating
• Occurrence- High probable failures get a high rating
• Detection- Failures that are difficult to detect ahead of time
get high ratings
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Integrated Product and Process Design
How Do I Do FMEA?
• Risk Priority Number, (RPN) is calculated: (severity
x probability x detection)
• Failure modes are then sorted based on RPN
• A plan of action is identified for all high RPN’s (as
well as for those with high severity ratings)
• After plan is implemented, a new RPN is calculated for
that failure mode and compared with all other possible
failure modes…
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Integrated Product and Process Design
Severity Ratings: Example
Rating
10
8
6
4
2
Description
Dangerously High
Very High
Moderate
Low
Minor
Definition
Failure could injure a customer or employee
Failure renders the unit inoperable or unfit for use
Failure results in partial malfunction of product
Failure causes some performance loss
Failure not readily apparent, has minor effect on
product or process
Adapted from The Basics of FMEA, Robin McDermott, Raymond Mikulak, Michael Beauregard, Productivity
Press, 1996
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Example: Brake Failure
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How About For Your Project?
• Record Book exercise……
• Select one component from your design that would benefit
from performing an FMEA
• Identify most likely failure modes
• For one mode, select greatest concern:
• Severity of Failure (1-10)
• Probability of failure occurring (1-10)
• Detection of impending failure (1-10)
• Write results in Record Book
• Assign team member to present results
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Integrated Product and Process Design
FMEA Applied to Teams and Processes:
• Does your team and its individual members
meet important milestones?
• Are your prototypes (analytical/physical)
answering important design questions?
• Do you have and use your project schedule
each week in your team meeting? Why or
why not?
• Is there someone on your team you need to
reach out to and bring back into the project?
• Etc…..
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Learning from Failures
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All Products are Evolutionary…
2012 Chevrolet Volt
1931 Model A Ford
1906 Model N Ford
1965 Ford Mustang
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New Products Are More Challenging:
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New Product Failure Example
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Hydraulic Wrist Motor Failure
• Severe wear in rotating
cylinder of hydraulic
wrist motors, after only
60 hrs. of operation!
• First discovered during
acceptance testing!
• Each motor cost $2,500!
• 50 person years of
computer programming
already invested in
development of robot
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The Solution…
• Entirely new type of motor
developed; not dependent
on motor speed for internal
part lubrication
• Radial ball piston design
• Cost only $150/each
• What was learned?
Traditional axial ball piston
hydraulic servo motors
depend on speed for
hydrodynamic
lubrication…
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Integrated Product and Process Design
Failed Firestone Tire (Existing Product Failure)
• Tire failed after
apx. 40,000
miles
• Personal injury
case
• Company had
reputation of
two previous
major product
failures
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Integrated Product and Process Design
Brief Primer on Tires
• Bias ply tires have similar
sidewall and tread
stiffness. Less expensive
to manufacture.
• Radial tires have stiffer
tread but more flexible
sidewall, allowing tread
to last longer.
• However tire stresses
greater at “shoulder” of
tire, which means greater
bonding strength needed
between steel belt and
rubber. Tire pressure
25 more important.
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Note Tread Separation From Tire Casing
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Not Yet Failed
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Failed Firestone Tire (Existing Product Failure)
1. Tire failed after
apx. 40,000 miles
2. Personal injury case
3. Company had
reputation of
previous product
failures
4. However, failure
appeared to have
been caused from
improper previous
repair of a puncture
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Integrated Product and Process Design
Some Suggestions…
• Learn how to ask good design and good process questions
• Consider carefully: What might, go wrong?
• With the design you are developing…
• ….As a result of the way it may be used…
• Keep in mind: Most new products result from improvements
in previous products. Seek to learn from the past…
• Today’s new solutions can lead to tomorrow’s problems!
• Seek out applicable standards…
• Perform realistic FMEAs early and often!
• Seek counsel from others, your coach, experts in field, etc.
• As carefully as you can, think through all of your design
decisions—particularly those that involve risk and safety!
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Integrated Product and Process Design
Summary:
• Defined product quality and shared examples
• Focused on one course outcome for detailed
design—FMEA
• Showed you how to do FMEA
• Team exercise so you could learn to begin to
apply this detailed design tool to your
project
• Shared FMEA examples and suggestions
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Aim High!
Thank You!
Face trouble with
Courage
Disappointment with
Cheerfulness
And triumph with
Humility
President Thomas S. Monson
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Example Two: Mini-Baja Rear Suspension…
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Modified FMEA Example
Trailing Arm
Potential Failure Mode
Trailing arm member bends
Trailing arm member breaks
Limiting spring breaks
Rear axle shears at hub
Tire loses bead/seal
U joint breaks
Thrust bearings break
Averages
Double A Arm
Severity
Probability
Product
3
8
5
8
5
8
7
3
1
0.5
2
4
1
1
9
8
2.5
16
20
8
7
6.286
1.786
Total
70.5
Potential Failure Mode
Lower A-arm member bends
Lower A-arm member breaks
Upper A-arm member bends
Upper A-arm member breaks
Tire loses bead/seal
CV shaft breaks
CV boot tears/breaks
CV joint breaks
Averages
Total
Severity
Probability
3
5
3
8
5
5
2
5
4
2
1
1
1
3
1
4
4.5
2.125
Product
12
10
3
8
5
15
2
20
• Severity of failure is greater, on average, for the Trailing Arm Suspension
• Probability of failure is greater, on average, for the Double A Arm Suspension
• Detection not considered. Why?
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What can we learn from
product design failures?
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Failure Case Study
New Spoiler Spoils Chaparral 2E Debut
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Bridgehampton, N.Y. Sept 18- The spoiler on the new Chaparral 2E more
than lived up to its name in this second round of the Cam Am series.
In practice, a bolt fell off the device on Phil Hill’s car, dropped down
into the bodywork and onto a tire, causing it to blow and the car slewed off
the course at turn 11 and Hill trudged back to the pits.
Hall offered the ex-world champ his own car “to get some practice in”
and out went Hill again. After five tours of the track a bolt fell off the spoiler
of Hall’s car (Hill driving), dropped onto the bodywork and onto a tire,
causing it to blow. The car slewed off the course at turn 11 and parked
right next to the first car.
Then, with Hill’s (the only car capable of proper repair) Hall withdrew
his pole-sitting 2E and Hill began a classic chase of eventual winner Dan
Gurney.
For 50 laps they were within fractions of a second of each other until
the spoiler on the Chaparral stuck in the “brake” position and hill dropped
Integrated Product and Process Design
back to finish fourth.
Chapparal Race Car
Chapparal Spoiler Support
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Ball joint
rod End
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Motivation for FMEA
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What is OSHA?
• Occupational Health and Safety
Administration
• Founded by an act of the U.S. Congress in
1970
• OSHA has standards for machines used in
the workplace
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Integrated Product and Process Design
Do OSHA Standards
apply to your project?
•
•
•
•
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What are the applicable OSHA standards?
Are the OSHA standards reasonable?
What failures (accidents) have occurred?
Is there any precedence from precious
cases?
• What are the implications of making a
design change now or later?
• Etc.
Integrated Product and Process Design
OSHA
• You as a designer can be held responsible
for accidents based on the way people use
things:
OSHA Standard Interpretation Letter dated 26 February, 1999:
“….in order for employee exposure to [an accident to] exist, it
must be shown that it is reasonably predictable either by
operational necessity or otherwise (including inadvertence),
that employees have been, are, or will be in the zone of danger.
…..the inquiry is not simply into whether exposure is
theoretically possible. Rather, the question is whether employee
entry into the zone of danger is reasonably predictable.”
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OSHA Mixer Case
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Firestone Tire
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Next Week
• “Around the table” design reviews this
week!
• Linda has sent out a schedule
• See page 23 concerning Design Reviews
• Rubric found on page 26
• Next week Lecture:
• “Industrial Design and Engineering: Partners
in Product Development”—Richard Fry
• Make sure you read Chapter 10 of U & E
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Innovation—The Opportunity
Maine manufacturer innovates to compete with imports.
Mainebiz (1/15/08, Richardson) reports, "Most would assume" that
Saunders Manufacturing, maker of items such as aluminum form
holders and clipboards, "would have been driven out of business by
cheap imports long ago. But John Rosmarin, Saunders' president and
CEO..., says it's been the company's ability to adapt, innovate and
reduce costs that are responsible for keeping it afloat in the face of
cheap imports." Rosmarin said that his company has been able to
remain innovative by making clipboards more "more attractive to
consumers that shell out more money for products they view to be
environmentally friendly." To accomplish this, Saunders "began
manufacturing some of its products with aluminum recycled from beer
and soda cans," and "plans to manufacture all its products from
recycled aluminum by the middle of this year." Also, the company has
found "ways to cut its costs, find efficiencies, [and] reduce defects."
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FMEA: Motivation
• Even simple products can have many
ways in which they may fail
• Example: Breadmaker
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•
•
•
•
•
•
•
Heating element does not heat properly
Dough kneader motor fails to work
Kneading paddle becomes jammed
Display fails
Timer does not time properly
Controller fails
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Etc.
Cummins Engine for FMEA
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FMEA: Motivation
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• Product Recalls, Consumer Reports, Feb
2001:
• Playskool “Sesame Street Poppin Pals”
Toys: Small spring inside toy could break
loose and pose choking hazard to small
children….
• Leap Frog Alphabet Pal electronic pull toy:
Two-part red plastic connector on pull
string could come off and pose choking
hazard…..
• Fisher Price
andDesign
Go Walker: Car
IntegratedGet
ProductUp
and Process
FMEA and Product Quality
“Suppliers shall establish and implement an
advanced product quality planning
process…
Suppliers should convene internal crossfunctional teams to prepare for production
of new or changed products”
Quality System Requirements: ISO-9000
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