Understanding the Problem and the Development of Engineering Specificationsl Importance of finding the right problem to be solved:

– Unnecessary effort to design a retarder (dampener) determining the final position of the solar panels in the Mariner IV satellite

– Finding the right problem to be solved is often not easy although it may seem a simple task.

l Creeping Specifications:– Specifications changing during the design process

• More features can be added as more is learned during the process• New technologies or competitive products introduced during the design (ignore,

incorporate or start all over?)• Changes in any spec. affecting the previous decisions depedent upon that spec

l Engineering Specifications (requirements) should be:– Discriminatory:

• Reveal the difference between alternatives.– Measurable (most important and major topic of chap 6)– Orthogonal

• Each specification should identify a unique feature of the alternative.– “Product must give smooth ride over rough road.” vs. “Product should reduce shocks from bumps.”

– Universal• Characterizing an important attribute of all the proposed alternatives

– External• Only external features are observable.

Quality Function Deployment (QFD)

l Most popular technique used to generate engineering specifications in an organized manner

– Developed in Japan in the mid-1970s and introduced to the US in the late 1980s

• 69% of the US companys use the QFD method recently

l Important Points– Employ QFD no matter how well the design team thinks it understands a

problem.– QFD takes time to complete, but time spent for QFD saves time later.– QFD can be applied to the entire problem and also any subproblems.– QFD helps over come our cognitive limitation.

• We tend to try to assimilate the customer’s functional requirement (what is to be designed) in terms of form (how it will look).

Quality Function Deployment (QFD)

House of Quality

Example of QFDStep 1: identify the customers

Step 2: determine the requirements

Step 3: determine the relative importance of requirements

Step 4: identify and evaluate the competition

Step 5: generate engineering specification

Step 6: Relate customers’ requirements toengineering specifications

Step 7: Set engineering targets

Step 8: identify the relationships betweenengineering requirements

QFD Step 1: Identify the Customers: Who are they?

For general products:

Who are the customers?-Consumers-Designers’ management-Manufacturing personnel-Sales staff-Service personnel-Standard organizations-Etc.

For many products, there are 5 or more classes of customers whose voices need to be heard

For a spinal implant system:

Who are the customers?-Orthopaedic surgeons-Neurosurgeons-Nurses-Hospitals-Distributors-Sales Reps-Patients ?

QFD Step 2: Determine the Customer’s Requirements: What do the customers want

Consumers:- works as it should, - lasts long,- is easy to maintain, - looks attractive, - incorporates the latest technology,- and has many features.

Production Customer:- is easy to produce (both manufacture and assemble),- uses available resources (human skills, equipment, and raw materials),- uses standard parts and methods, - uses existing facilities,- produces a minimum scraps and rejected parts.

Marketing/Sales Customer:- easy to package, store, and transport,- attractive and suitable for display

Types of Requirements:-Basic features: neutral satisfaction with existence

-basic assumed functions; not included in QFD- Performance Features: good satisfaction with existence

- verbalized in the form that the better the performance, major part of QFD- Excitement (or WOW) Features: high satisfaction with existence

- often unspoken because customers do not expect these features

l How to collect customer’s requirements:– Observation of customers– Surveys: mail, telephone, face-to-face– Focus-group technique

• A group of surgeons for orthopaedic implants

l Steps for developing useful data for requirements:– Specify the information needed:

• Reduce the problem to a single statement. If impossible, more than one data collecting effort may be warranted.– Determine the type of data-collection method to be used:

• Depending on the use of data collection methods– Determine the content of individual questions:

• Write a clear goal for the results expected from each question.– Design the questions:

• Each question should seek unbiased, unambiguous, clear and brief information.• Do not: assume that the customers have more than common knowledge; use jargon; lead the customer toward the

answer you want; tangle two questions together. • Do use complete sentences

– Order the questions:• Order them to give context

– Take data:• Any set of questions should be considered a test or verification. • Repeated application is required to generate usable information.

– Reduce the data:• Make a list of customer’s requirements in the customer’s own word (easy; fast; other abstract terms).• The list should be in positive terms, i.e., wanted, not unwanted

QFD Step 2: Determine the Customer’s Requirements: What do the customers want?

Types of Customers’ Requirements:l Functional Performance

– Performance about the product’s desired behavior– Flow of energy, information, or materials; Operational steps; operation sequence

l Human Factors– Required in any products that is seen, touched, heard, tasted, smelled or controlled by a human– Appearance; Force and motion control; Ease of controlling and sensing state

l Physical Requirements– Available spatial envelope; Physical properties

l Reliability– Mean time between failures; Safety (hazard assessment)

l Life-Cycle-Concerns– Distribution (shipping); Maintainability; Diagnosability; Repairability; Testability; Cleanability;

Installability; Retirementl Resources Concerns

– Time; Cost; Capital; Unit; Equipment; Standards; Environmentl Manufacturing Requirements

– Materials; Quantity; Company capabilities

**For Spinal Implants:- Functional performance (flow of energy, operational steps and operation sequence)- Human Factors - Physical Requirements- Reliability (mechanical failure, corrosion, biocompatibility, and complications due to the failure)- Other requirements are not as critical as for other common products

QFD Step 2: Determine the Customer’s Requirements: What do the customers want?

l Evaluate the importance of each of the customers’ requirements

– Generate a weighting factor for each requirement considering• To whom is the requirement important• How is a measure of importance developed for this diverse group of

requirements

– How to determine the weight factor• Customer’s rating from 1 (unimportant) to 10 (important)• Fixed Sum Method:

– Distribute the importance on all the listed requirements

QFD Step 3: Determine the Relative Importance of the Requirements: Who vs. What

l Determine how the customer perceives the competition’s ability to meet each of the requirements.

– 1 The product does not meet the requirement at all.– 2 The product meets the requirement slightly.– 3 The product meets the requirement somewhat.– 4 The product meets the requirement mostly.– 5 The product meets the requirement completely.

l Why studying existing products?– It creates an awareness of what already exists.– It reveals opportunities to improve on what already exists.

l This process is called “Competition Benchmarking.”

QFD Step 4: Identify and Evaluate the Competition: How satisfied is the customer now?

l Engineering Specifications:– Restatement of the design problems in terms of parameters that can be

measured and have target values.– If units for an engineering parameter can not be found, the parameter is

not measureable and must be readdressed.l Examples:

– Easy to attach• The number of steps; time to attach; number of parts; number of tools used

l Every effort must be made to find as many ways as possible to measure customer’s requirements.

l Carefully check each entry to see what nouns are or noun phrases have been used because each noun refers to an object that is part of the product or its environment and should be considered to see if new objects are being assumed.

– “easy to adjust suspension system … ” then “an adjustable suspension system” has been assumed as part of the solution.

QFD Step 5: Generate Engineering Specifications: How will the customers’ requirements be met?

QFD Step 6: Relate Customers’ Requirements to Engineering Specifications: How to measure what?

Strong, medium, weak, and no relationship

QFD Step 7: Set Engineering Targets: How much is good enough?

1. Ascertain how the competition meets the egineering goal.2. Establish targets for the new product.Remember:

- Set the target early.- Too tight target may eliminate new ideas.- If a target is much different than the values achieved by the competition, it should be questioned.

Strong negative; negative; Positive; Strong positive

QFD Step 7: Identify Relationships between Engineering Requirements: How are the “HOWS” dependent to each

other?

Example of QFDStep 1: identify the customers

Step 2: determine the requirements

Step 3: determine the relative importance of requirements

Step 4: identify and evaluate the competition

Step 5: generate engineering specification

Step 6: Relate customers’ requirements toengineering specifications

Step 7: Set engineering targets

Step 8: identify the relationships betweenengineering requirements