6.3 Design specifications: Specifying functions, features and behavior

Question 1

What do prescriptive specifications specify?

Answer 1

Prescriptive specifications specify values for attributes of design.

Question 2

What are the prescriptive specification values that may be applied to the following examples?:

• the children’s juice container
• the ladder

Answer 2

Prescriptive specifications for our examples:

For our children’s juice container: A juice container must be made of at least 50% recyclable plastic.

For a ladder design: Ladder step specifications

• Shall be made from Grade A fir
• Shall have a thickness of at least 0.75 in.
• Shall have a length that does not exceed 80 in.
• Shall be attached to the side rails through a full- width groove at each end.

Question 3

What do procedural specifications specify?

Answer 3

Procedural specifications specify procedures for calculating attributes.

Question 4

What are the procedural specification values that may be applied to the following examples?:

• the children’s juice container
• the ladder

Answer 4

Procedural specifications for our examples:

For our children’s juice container: must be disposable as stipulated by EPA standards.

For a ladder design: The maximum bending stress σ_max in a ladder step shall be calculated from σ_max = M*c/I and shall not exceed the allowable stress.

Question 5

What do performance specifications specify?

Answer 5

Performance specifications specify performance levels that a function must demonstrate to be successful.

Question 6

What are the performance specification values that may be applied to the following examples?:

• the children’s juice container
• the ladder

Answer 6

Performance specifications for our examples:

For our children’s juice container: must contain 75 mL

For a ladder design: shall support an 800lb

Question 7

What do interface performance specifications specify?

Answer 7

Interface performance specifications specify the manner of interaction of systems or device that must work with other systems or devices (i.e. how devices or systems must work together with other systems).

Question 8

What is the purpose of specifications?

Answer 8

We use specifications to scale functions.

Question 9

What are specifications needed for?

Answer 9

Specifications are needed for every function our design must perform.

Question 10

Do designs typically meet specifications for all functions?

Answer 10

Designs MUST meet each and every specification.

Question 11

Explain when specifications are projected into the future.

Answer 11

Specifications, such as constraints, are projected into the future when we specify, in advance, the functional or behavioral performance that MUST be achieved in order for a design to be considered to be successful.

Question 12

What does a utility (usefulness) saturation curve represent?

Answer 12

Utility saturation curves show that no additional benefit is achieved below some minimal realized level and above saturation.

Question 13

Draw a saturation curve to describe the lack of additional benefit below some minimum threshold and above saturation.

Answer 13

Question 14

What method is used to make the following utility curve more useful?

Answer 14

Linear approximation is applied to the saturation utility curve in order to make it more useful.

Question 15

How do we answer the following question:

Since we measure sound intensity levels in decibels (dB), we know that some dB range is likely to be of interest, but what range?

Answer 15

We answer this question by seeing how much noise is produced by other devices, and within different environments.

Question 16

What is the first step to setting performance levels?

Answer 16

The first step to establish performance levels is to:

• identify design variables that reflect the functions that must be performed AND
• identify the units in which those variables are measured

Question 17

What questions might we ask to identify the useful variables and units to set performance levels for the following function of a juice container:

Contain Liquid

Answer 17

Useful questions to ask for establishing performance levels for the containing liquid function may include:

• How much liquid must the container contain, and at what temperatures?
• Is there a range of fluid amounts that we can put into a container and still meet our specification?

Question 18

What questions might we ask to identify the useful variables and units to set performance levels for the following function of a juice container:

Resist forces induced by temperature extremes

Answer 18

Useful questions to ask for establishing performance levels for the resist forces induced by temperature extremes function may include:

• What temperature ranges are relevant?
• How might we measure the forces created by thermal stresses on the container designs?

Question 19

What questions might we ask to identify the useful variables and units to set performance levels for the following function of a juice container:

Resist forces induced by handling in transit

Answer 19

Useful questions to ask for establishing performance levels for the resist forces induced by handling in transit function may include:

• What is the range of forces that a container might be subject to during routine handling?
• To what degree should these forces be resisted in order for the container to be thermal stresses on the container designs?

Question 20

When are interface performance specifications important?

Answer 20

Interface performance specifications are particularly important:

• in cases where several teams of designers are working on different parts of a final product, and all of the parts are required to work together smoothly.

And are gaining in importance:

• for large firms that, in a highly competitive international arena, are trying to minimize the total time needed to design, test, build, and bring to market new products.

Question 21

What is key when establishing interface performance specifications?

Answer 21

Boundaries between subsystems must be clearly defined, and anything (i.e., energy, material, information) that crosses a boundary has to be specified in sufficient detail to allow all teams to proceed.

Question 22

How have proper interface performance specifications improved design and development in the automobile industry?

Answer 22

Most of the world’s major automobile companies have reduced their design and development times for new cars to less than one-half of what they were a decade ago by having design teams work concurrently, or in parallel, on many subsystems or components.

Question 23

What has having design teams work concurrently, or in parallel, on many subsystems or components emphasized.

Answer 23

Having design teams work concurrently, or in parallel, on many subsystems or components has emphasized:

• that teams must work together (i.e. teamwork between teams)
• the importance of understanding and working with interface performance issues.

Question 24

For what is a house of quality useful?

Answer 24

A house of quality is useful for:

• accounting for the customer’s requirements
• relating and exploring relationships among stakeholder interests, design attributes, measures, targets and current products

Question 25

What is design quality and what do we mean by design for quality?

Answer 25

Quality, in terms of design, is:

• “fitness for use.”
• a measure of how well a product or service meets its specifications and requirements

Question 26

Visually describe/outline a house of quality.

Answer 26

Question 27

What is one of the most important notions used by many designers and which tool is used to express that notion?

Answer 27

One of the most important notions used by many designers is quality function deployment (QFD), which is expressed in a tool called the House of Quality (HoQ).

Question 28

What is a house of quality?

Answer 28

A HoQ is a matrix that combines a lot of information about stakeholders, desirable characteristics of designed products, current designs, performance measures, and trade-offs.

Question 29

What does the Who refer to in the house of quality?

Answer 29

In a house of quality:

Who refers to the stakeholders in the design process: client(s), users, and other affected parties.

Question 30

What does the What refer to in the house of quality?

Answer 30

In a house of quality:

What entries correspond to the design’s desired attributes (i.e., objectives, constraints, functions) objectives.

Question 31

What does the Now refer to in the house of quality?

Answer 31

In a house of quality:

Now entries refer to existing products or designs that are typically found during problem definition, and they are used for benchmarking proposed designs.

Question 32

What does the How refer to in the house of quality?

Answer 32

In a house of quality:

How elements refer to the metrics for objectives and the specifications for functions.

Question 33

What does the How Much or Target refer to in the house of quality?

Answer 33

In a house of quality:

How Much or Target are goals or targets for the What entries.

Question 34

To what are the additional sections of the house of quality devoted?

Answer 34

The remaining sections of the house of quality are devoted to the relationships, values, or trade-offs among the Who, What, Now, How, and How Much or Target elements.

Question 35

Make a house of quality for the design of a computer laptop and an office computer.

Answer 35