Reverse Engineering

Establishing Product Functions

Learning Objectives

• Understand the concept of functional analysis and its role in the design process

• Use a “Subtract and Operate” procedure to develop a function tree for …..

• Use the function tree to develop a Function Structure diagram for ……

Reading

• Required Reading– Chapter 9– Establishing Product Functions handout

• Suggested reading– Appendix A - Function Structure Definitions

handout– Subtract & Operate handout

Functional Modeling and AnalysisProblem definition

ClarificationCustomer requirements

Distinguish constraints

Generate functions tree

Compare with customers requirements Create alternative

function structures

Identify product architecture and

assemblies

Functional analysis is an integral part of product design and re-design:A way of structuring your thinking about the problemA way of aiding Product Design Specifications developmentCan also aid in concept generation

Product Function(s)

Brainstorming / Directed Search / Inventive Problem Solving

Define Customer Requirements

Model and Analyze Function

Formulate Candidate System Solutions

Identify Functional Solutions + + + +

OR OR

F1 F2 F3 F4 F5

S1 S2 S3

6

Generating Concepts

Verify Functions Against NeedsHolds a lot of coffee L L LStays cool to touch L L L L

Keeps coffee hot (L) L L L LLooks nice

Feels nice (D) D D DLow price

Does not spill (B) B B B B B B B B B

DelighterLinear Satisfier

Basic Requirement

Acc

ept L

iqui

d

Con

tain

Liq

uid

Insu

late

Liq

uid

Con

tact

Air

Inte

rface

Han

d

Insu

late

Han

d

Tran

smit

Load

Insu

late

Sup

port

Sup

port

Con

tain

er

Inte

rface

Mou

th

Con

t. Li

q. /

Intf.

Mou

nth

Con

t. Li

q. /

Insl

. Han

d

Con

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Tran

s. L

oad

Product Functions

Cust

omer

Need

s

Functional Analysis...

• Identifies important system components and their functions.

• Describes how these components functionally interact with each other and super- and sub-systems.

• Clarifies the best problem to solve.

Functional Analysis/Modeling

• There are several methods for Functional Analysis– Product Function (Top-Down) --- Dissection– FAST (Functional Analysis System Technique) (Top-

Down)– Subtract and Operate Procedure (Bottom-Up) ---

Dissection

Functional Modeling Basics

Chop Beans

Transport People

AcceptHuman

Chopper Vehicle Door System

Product Function – What the product does. A statement of relationship between available input and desired output, independent of any particular form. (Overall Function)

Functional Modeling BasicsProduct Sub-function – A component of product function. The

combined effect of two or more product sub-functions is product function.

• Example: Hold Liquid• Contains liquid• Insulates liquid• Insulates hand• Supports liquid• Accepts pour• Interfaces hand• Pours out

A System...• Is an entity that is connected to its environment by

means of inputs and outputs defined on its boundary,• It can be defined in terms of mechanical construction (form)

or by function, and• It can be decomposed into Sub-systems connected to each

other by means of inputs and outputs defined on their respective boundaries.

Input 1 Output 1

Input 2 Output 2

Input 3 Output 3

SystemInputs Outputs

Functions

Functions should be expressed in terms ofmeasurable effects

Typical function expression: “active verb – noun”

“increase pressure”“transfer torque”

“store energy”“cool liquid”

Some functions that products/parts perform

amplify dissipate protect change fasten release channel heat rotate collect hold separate conduct increase store control join supply convert lift support cool lower transform decrease move translate

Refer to Appendix A - Function Structure Definitions handout for detailed description of functions.

Function & Flows

Function

Energy

Material

Signal

Energy

Material

Signal

State 1 State 2

All product activities involve changing the state of three basic quantities: energy, material and signal. We call this change of state a “flow”.

Form Function Flow

Hot Water

Water Heater

Cold Water

Electric Current

Heats WaterHot WaterCold Water

Electric Current

Form

Function

Flow

R

Is “Low Price” a function?

Functions vs. Goals vs. Constraints• Functions represent what the product does to satisfy the

customer need.• Some customer needs are satisfied by how the product is

implemented in form. These are attributes or features of the product.

• Criteria can be attributes on one product but functions on another. – Example: Storage compactness

Attribute : Small sizeFunctional Solution: Make it fold up

• When in doubt: If the criteria is met by an identifiable sub-system doing something, then it is a function; otherwise, it is an attribute.

Subtract and Operate Procedure1. Disassemble (subtract) one component of the

assembly.2. Operate the system through its full range.3. Analyze the effect.4. Deduce the subfunction of the missing component.5. Replace the component and repeat n times where n

is the number of components in the assembly.6. Translate the collection of subfunctions into a

function tree.

GrinderOperator

Coffee Beans

EnergySystem

Ground Coffee

Chamber

SealSlicing blade

Example: Coffee Grinder

Elements for Subtraction with ResultsChamber Seal Slicing Blade Shaft Armature

No defined way of holding content

No protection against contents splattering

Contents won’t be chopped

Slicing blade won’t be attached

Shaft doesn’t spin

No measurable volume

No protection against spinning blade

No resistance to torque

Contents will not be chopped

Electricity is not transformed into mechanical energy

No body to measure contents

Chamber can’t be closed

No resistance to torque

No body to contain contents

Impact noise will not be enclosed

No body to hold apparatus

Might not be able to turn on if safety feature

Looks bad

Difficult to clean undefined body

Pour out contents

The Subtract and Operate procedure helps us determine the critical functions and subfunctions of our device. These can be mapped to a function tree similar to figure 5.6 from Otto and Wood.

Function Tree

Steps in Creating a Function Structure

• Identify the overall function. In our case, this is the top block in the function tree.

• Identify the basic individual functions that are required to accomplish this task. We have already done this in the first row of functions of the Function Tree.

• Identify more precise functions from the basic functions determined in the previous step. Note that these two steps will be iterative. These more precise functions are the second level of blocks in the Function Tree.

• Arrange the function blocks in the order that they must occur to accomplish the desired overall function. This is a flow chart of functions in which order is important. The easiest way for us to do this is to take the 3x5 cards we used to make the function tree and place them in position until the group is satisfied.

• Add the energy, material, and signal flows between the function blocks as appropriate.

• Double check to make sure you haven’t missed a function block or flow line. • Reproduce the function diagram electronically.

Function Structure

Thick arrows: material flow Thin arrows: energy flow

Where to go from here?

• SOP for flash light• Generate SOP table• Generate function tree• Generate function structure• All of this is due next Monday

Activity for Today

Apply SOP on flashlight / spot light you have

1. Case - A very thin spring or strip of metal (usually copper or brass) that is located throughout the flashlight, making the electrical connection between the various parts – the batteries, the lamp and the switch. These parts conduct electricity and “hook everything up”, completing the circuit.2. Contacts - Deeper grooves for easier hold.3. Switch - The flow of electricity is activated when you push the switch into the ON position, giving you light. The flow of electricity is broken when the switch is pushed into the OFF position, thus turning off the light.4. Reflector - A plastic part, coated with a shiny aluminum layer that rests around the lamp (bulb, LED) and redirects the light rays from the lamp to allow a steady light beam, which is the light you see emitting from the flashlight.5. Lamp - The light source in a flashlight. In most flashlights, the lamp is either a tungsten filament (incandescent bulb) or a light emitting diode (solid state bulb), also known as an LED. The lamp glows when electricity flows through it, thus producing visible light. Incandescent bulb must be replaced when the tungsten filament breaks. An LED contains a very small semiconductor (diode) that is encapsulated in epoxy. LEDs in flashlights are widely considered “unbreakable” – a lifetime lamp.6. Lens- Clear, plastic part you see on the front of the flashlight that protects the lamp.7. Batteries- When activated, batteries are the power source for your flashlight.

http://www.energizer.eu/eu/ee/site/how-flashlights-work.html

Case Contacts Switch Batteries Reflector Lamp / LED

Lens