Use of Function Analysis in Preliminary Design

Function Development

What are functions?

Functions defines “what” a product must do.

Form defines “how” that is accomplished.

Form follows Function!

Functions can be derived from requirements…

What behavior is necessary to accomplish

the requirement(s)?

What are functions?

Functions represent a flow of:

Material, Energy, Information

Functions are hierarchical.

A successful functional analysis will decompose functions to lowest possible level

Why use function analysis?

• Function controls the design process… we won’t waste time generating products which solve the wrong problem.

• Functions are used to facilitate the move from needs/requirements to solutions. Encourages “form independent” solutions.

• Want the customer needs and requirements to drive our concepts for solutions as well as serve as methodology for evaluation.

Why use?

• Finer decomposition of function leads to a greater understanding of the problem.

• May lead to the realization and identification of existing components that can provide the functionality.

How to use?

• Attempt to develop a list of all functions the design must fulfill

• Examine the defined needs/requirements for design,

Ask: “What behavior is necessary to accomplish these requirements?”

• Try to “de-compose” functions to lowest possible/practical level

How to use?

• For each need/requirement…

• Consider :

energy flow

material flow

information flow

• Write in verb/noun format, e.g. move mass, provide information, control energy

• Use list of verbs (on handout) to help you generate list

Examples of Function “verbs”

absorb collect fasten locate rotate transfom

accept conduct grasp move secure translate

actuate control guide orient separate verify

amplify convert hold position shield

apply couple increase produce start

assemble decrease interpret protect steer

avoid direct interrupt provide stop

change dis-assemble

join rectify store

channel dissipate lift release supply

clear drive limit remove support

How to use?

• Example :

For bicycle helmet requirement “safety”,

Consider “What behavior is necessary to provide safety?”

Absorb energy Decelerate mass

Dissipate energy Maintain attachment

• Revise any functions if needed.

• Try to identify and eliminate un-necessary functions.

• Use a tool (such as post-it notes) to organize functions by type and level of hierarchy (decomposition).

How to use?

Revision / Decomposition

Revising and decomposing functions.

From helmet example…

Maintain attachment could become maintain contact

Maintain contact could decompose to…

Provide attachment

Ensure attachment

Provide adjustment

Using Post-It Notes to Layout Functions

Using Post-It Notes to Layout Functions

Functions Example (Bike Helmet)

Functions Example (Drill)

Consider a Drill Overall Function is to “Create Hole”

Supply Power > Store Power > Control Power

Create Rotary Motion > Control Rotary Motion

Create Linear Motion > Control Linear Motion

Provide Enclosure

Accommodate Grip > Accommodate Controls

Next Steps

• Examine functions at lowest level of decomposition.

• Use various concept generation techniques

brainstorming,

6-3-5 (a brainstorming alternative),

research (patents, other devices),

TRIZ

to develop a list of potential solutions (“how” for the “what”)

Next Steps

From helmet example:

Function – “provide attachment” (the “what”)

Possible concepts – the “how”

Velcro, snap(s), bayonet style clasp…

Function – “provide adjustment” (the “what”)

Possible concepts – the “how”

Moving panels, insertable pieces, air bladder…

Identify as many potential concepts as possible…

DON’T WORRY ABOUT EVALUATING IDEAS YET!

Next Steps

From drill example: Function – “supply power” (the “what”)

Possible concepts – the “how”

Self-regulating chemical reaction Combust jobsite sawdust

Hydraulics Fuel/air combustion

CO2 in tank Battery

Flywheel charging Solar

Wind Geo-thermal

Steam Human power