shanghai jiao tong university 1 quality function deployment me 250: design & manufacturing i...
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Shanghai Jiao Tong University 1
Quality Function Deployment
ME 250: Design & Manufacturing I
School of Mechanical Engineering
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Outline
Objectives of QFD QFD Structure The General Process of QFD Project Plan Gantt Charts
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QFD (Quality Function Deployment)
QFD originated in 1972 at Mitsubishi’s Kobe shipyard site.
The “house of quality” is the basic design tool of the management approach.
The “house of quality” is a kind of conceptual map that provides the means for interfunctional planning and communications.
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Quality Function Deployment
“Let the customer be heard”
QFD is a tool to help understand the design problem and to translate customer requirements into a
technical description of what needs to be designed.
QFD focuses and coordinates skills within an organization, first to design, then to manufacture and
market goods.
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Effect of using QFD
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Objectives of QFD Identify exactly what the design goals are and how they are
going to be achieved
I.e., translate “customer requirements” into workable “engineering solutions”
Forces “fresh eyes” on the design problem; prevents getting stuck prematurely with preconceived concepts
Reduces risks of delay in new product introduction due to poor specifications, unrecognized interdependencies of specifications, etc…
Provides formal record of conceptual design process for documentary, legal, management, benchmarking, etc.
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CAs and ECs
Customer Attributes(CAs) : Customers use to describe products and product characteristics.
What do customers want?
Engineering Characteristics(ECs): Engineers use to describe the products.
How can we change the product?
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The General ProcessCustomer requirements
Part characteristics
Manufacturing operations
Production requirements
Design requirements
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Building the House For a car door
Customer Attributes(CAs)
Good operation and use
Good appearance
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Customer Attributes(CAs)
Good operation and use Easy to open and close door Isolation Arm rest ……
Good appearance Clean Fit ……
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Customer Attributes(CAs)
Easy to open and close door Easy to close from outside Stays open on a hill Easy to open from inside ……
Isolation Doesn’t leak in rain No (or little) road noise ……
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Customer Attributes (CAs)
Two problems Which CAs are important? What does the customer really mean?
quiet easy
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QFD Structure 6. Crosscorrelate
specifications
5. Correlation matrix for requirements & specifications
4. Engineering specifications
7. Specification targets
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Steps of QFD
0. Identify the customers.
1. Determine the customer requirements
2. Determine Requirement Weights
3. Benchmark the competition
4. Convert requirements to quantifiable eng. specs.
5. Correlate customer requirements to eng. specs.
6. Cross-correlate engineering specifications
7. Set the engineering targets with units.
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Step 0: Identify the Customers Every design must serve a practical need of one or more end-users or
“customers”. There may be several levels of customers/stakeholders with very different interests.
It is the desire of the customer that drives the development of the product, NOT the engineer’s vision of what the customer should want.
Some questions to be asking:
What is the target market for the product? Who is the consumer for the product? Who will buy the product (and tell other consumers about the product and its quality)?
Who are the stakeholders in the product? What roles will management, SPONSORS, manufacturing personnel, sales staff, service personnel hold? Are they also customers?
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Step 1: Determine Customer Requirements
These requirements commonly expressed in qualitative” terms and are determined by consultation in some form with the customer (Market surveys, focus sessions, customer feedback, etc).
Types of Requirements: Functional Performance Spatial Appearance/Aesthetic Time Cost Manufacturing/Assembly Safety Environment and Environmental
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Where to Gather Data
Interviewing Customers or Focus Groups. Observing the product in use. Surveying customers. Searching patent and other information
sources and benchmarking the competition.
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How to Gather Data Be receptive; avoid confrontations.
Express what the product has to do, not in terms of how it might do it.
Set targets ( the machine must weigh no more than 10 lbs).
Set value curves or slopes.
Express the need as an attribute of the product.
Prepare interview guide to structure dialogue such that all info. is gained.
Avoid the words must and should ( We will rank importance later).
Go with the flow.
Use visual stimuli and props.
Suppress preconceived hypotheses about the product technology.
Have customer demonstrate product and/or task related to the product.
Be alert for surprises and the expression of latent needs and follow up.
Watch for nonverbal information.
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QFD Structure 6. Crosscorrelate
specifications
5. Correlation matrix for requirements & specifications
4. Engineering specifications
7. Specification targets
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Customer Requirements
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Step 2: Determine Weights for Requirements
Different customers have different priorities! Identify the customers. Identify all the requirements that are
"absolute must". In the weighting column of the QFD indicate
these requirements with a value. All the remaining requirements are
considered “wants” The goal is to have as many wants as possible,
but we can’t have everything we want!
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Example of Establishing Weights
1. Make a chart with all of the requirements.
2. Compare two requirements at a time. Give the more important requirement a 1 and the less important requirement a 0.
3. Compare all requirements.
4. Sum totals for each requirement.
5. Divide totals for each requirement by number of combinations resulting in a percentage. This is the weight of the requirement.
6. Enter weight of requirement into QFD chart.
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Proposed Ranking System
(Ulrich, 1995)
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QFD Structure 6. Crosscorrelate
specifications
5. Correlation matrix for requirements & specifications
4. Engineering specifications
7. Specification targets
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Weight
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Step 3: Benchmark Competition How well do any existing competitive designs serve
customer needs & how can they be improved upon?
Identify one or more “benchmark” designs that serve identical or similar customer requirements. Evaluate against each requirement (customer and engineering) as follows (rather subjective):
1 = doesn’t satisfy requirement at all
2 = satisfies requirement “slightly”
3 = satisfies requirement “somewhat”
4 = satisfies requirement “mostly”
5 = satisfies requirement perfectly
Identifies area for improving current on practice; best suited to establish mass-market products
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QFD Structure 6. Crosscorrelate
specifications
5. Correlation matrix for requirements & specifications
4. Engineering specifications
7. Specification targets
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Custom perceptions
Our car
A’s car
B’s car
competition
Benchmark Competition
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Step 4: Engineering Specifications Market survey: what to do?
Engineering: how to do it?
We need to describe the product in the language of
the engineer.
Easy to close from outside
CA
Energy to close door
EC
“-”
Hope to reduce the energy required
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Step 4: Engineering Specifications Quantifiable parameters that design engineer may
specify/control to address the customer needs.
Every specification must have appropriate units
If you can’t quantify a specification (find appropriate units) it’s not a valid parameter and you’ll have to rethink it.
Example -- customer requirement quantifiable parameters: average life to failure (years); fraction
that survive > 10 years (%); max. drop onto hard floor without breaking (ft); failure load (lb)….
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Step 4: Engineering Specifications One or more engineering specifications addressing
each of the customer requirements will be needed (the more, the better) -- if you can’t find them, try re-formulating the customer requirement.
If a EC affects no CA, it may be redundant to the EC list on the house.
Any EC may affect more than one CA.
Door seal resistance
EC Easy to close from outside
Doesn’t leak in rain
No road noise
CA
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QFD Structure 6. Crosscorrelate
specifications
5. Correlation matrix for requirements & specifications
4. Engineering specifications
7. Specification targets
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EC
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Step 5: Correlate Customer Req. andEngineering Specifications
How much does each engineering specification influence the customer requirements?
Make a systematic pairwise comparison of the specifications & requirements; enter correlation value for each pair as follows: 9 = strongly related 3 = somewhat related 1 = weakly related = totally unrelated
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QFD Structure 6. Crosscorrelate
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5. Correlation matrix for requirements & specifications
4. Engineering specifications
7. Specification targets
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EC
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Importance Weighting
Importance Weighting identifies which technical requirements are most important to achieve. In this chart, each weighting is calculated by multiplying the “importance to customer” rating times the value, assigned to a relationship totalling the column.
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EC
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Step 6: Cross Correlate Specifications
The chosen engineering specifications are not always independent of each other -- we need to express the fact that changing any one can influence the others.
Use diagonally-oriented cross-correlation matrix in QFD area 6 (the “roof” of the “house of quality”) to express interdependencies of the specifications.
If you can’t do diagonally-oriented arrays, use a separate square array with both axes labeled with the specifications -- fill out the upper-left triangular matrix.
Use 9-3-1-blank system for correlation strengths.
The cross-correlation matrix helps reveal indirect dependencies of requirements upon specifications.
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QFD Structure 6. Crosscorrelate
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5. Correlation matrix for requirements & specifications
4. Engineering specifications
7. Specification targets
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EC
x 9
9
9
x
9
x
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Step 7: Set Engineering Targets List benchmarks enter their performance for each of the
specifications -- this may require some “reverse engineering”
Set targets for each specification, taking account of customer requirements and benchmark values -- the target may be:
Specific value Range of values Lower/upper bound Lesser/greater is better
Targets should be reasonable -- they can’t defy laws of physics, materials properties, economic constraints, etc.,
If competing state-of-the-art design exist, ask yourself how to achieve better targets than them -- be realistic!
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QFD Structure 6. Crosscorrelate
specifications
5. Correlation matrix for requirements & specifications
4. Engineering specifications
7. Specification targets
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EC
x 9
99
x
9
x
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Approach to QFD
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Example: Bicycle Splashguard
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Sample List of Customer Requirements• Riders’ and shop mechanics’ requirements
keeps water off rider easy to attach easy to detach quick to attach quick to detach won’t mar bicycle won’t catch water/mud/debris won’t rattle won’t wobble
Company management requirements capital expenditure of less than $15,000 developed in three months; manufacturing cost less than $3 estimated volume of 200,000 per year for five years
won’t bend has a long life won’t wear out lightweight won’t rub on wheel attractive fits universally won’t interfere with lights,
rack, or brakes
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QFD forSplashguard
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QFD forSplashguard
63 141 108 168 207 126 74 33
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QFD forSplashguard
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QFD A: Customer
Requirements B: Technical
Requirements C: Importance to
Customer D: Relationship
Matrix
A
B
C
D
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QFD E: Target Values F: Importance
Weighting G: Correlation
Matrix H: Competitive
Evaluation
F
HG
E
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Four Steps to Establishing a Project Plan
Step 1: Identify the tasks Step 2: State the objective for each task Step 3: Estimate the personnel needed
and the time required to meet the objective. This will help define development costs.
Step 4: Develop Sequence for the task.
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Step 1: Identify the tasks
The first step in planning a project is to list the tasks that make up the project.
Uncertainty but still need to plan.
Task list should contain 50 to 200 items.
Each task on average should correspond to a day or two of work for an individual.
Continually update plan as more information becomes available.
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Step 2: State the objective for each task
Each task must be characterized by a clearly stated objective. Make it:
Easily understood. Specific Feasible Defined not as much as activities to be
performed but as results to be achieved.
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Step 3: Develop Sequence for the task
1. Schedule tasks
2. Determine correspondences between tasks
3. Determine critical paths
4. Reduce critical paths to accelerate project.
Tools: Gantt Charts Pert Charts
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Gantt ChartsUseful tool for representing timing of task
and level of task completeness Assign a row to a task and to milestones Order task in chronological order Attach a horizontal time line Draw a bar from start to end of each task. Continually track and update the Gantt
chart
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Gantt Chart Example
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Step 4: Estimate the Personnel and Time
Who on the design team will be responsible for meeting the objective or task
What percentage of their time will be required.
Over what period of time will be needed.
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Summary1. Always use QFD for mechanical design.
2. The customer's requirements must be translated into measurable design targets. You can't design a car door that is "easy to open" when you don't know the meaning of "easy". Is "easy" 20 N force or 40 N?
3. QFD can be applied to problems and sub-problems.
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Summary
4. It is important to first worry about what needs to be designed and, only after that is fully understood, to worry about how the design will look and work.
Our cognitive capabilities generally lead us to try to assimilate the customer's functional requirements (what is to be designed) in terms of form (how it will look); these images then become our favored designs and we get locked onto them.
The QFD procedure helps to overcome this cognitive limitation.