Chapter 5: Product Specifications

Product Design and DevelopmentsFourth Edition

by Karl T. Ulrich and Steven D. Eppinger

Announcements

• There will be no lab the week of the career fair.

Concept Development Process

Perform Economic Analysis

Benchmark Competitive Products

Build and Test Models and Prototypes

IdentifyCustomer

Needs

EstablishTarget

Specifications

GenerateProduct

Concepts

SelectProduct

Concept(s)

Set Final

Specifications

PlanDownstreamDevelopment

TestProduct

Concept(s)

DevelopmentPlan

Target Specs

Based on customer needs and benchmarking

Final Specs

Based on selected concept, feasibility, models, testing, and trade-offs

• Basic control and reference document for the design and manufacture

• Specific, measurable, testable criteria• “Unambiguous, Understandable, Correct, Concise, Traceable,

Traced, Design Independent, Verifiable, Unique, Complete, Consistent, Comparable, Modifiable, Attainable”

• Functional decomposition• Performance targets• Constraints (Demands, Musts)• Goals (Wishes, Wants)• Features

Product Design Specifications

Our Approach to PDS

• Process recommended for high-risk new product design.

• PDS development will be modified based on your product or process.

Last Class You Performed Benchmarking on Metrics

Met

ric #

Nee

d #s

Metric Imp Units ST

Trit

rack

Man

iray

2

Rox

Tah

x Q

uadr

a

Rox

Tah

x Ti

21

Tonk

a P

ro

Gun

hill

Hea

d S

hox

1 1,3 Attenuation from dropout to handlebar at 10hz 3 dB 8 15 10 15 9 132 2,6 Spring pre-load 3 N 550 760 500 710 480 680

3 1,3 Maximum value from the Monster 5 g 3.6 3.2 3.7 3.3 3.7 3.44 1,3 Minimum descent time on test track 5 s 13 11.3 12.6 11.2 13.2 115 4 Damping coefficient adjustment range 3 N-s/m 0 0 0 200 0 0

6 5 Maximum travel (26in wheel) 3 mm 28 48 43 46 33 387 5 Rake offset 3 mm 41.5 39 38 38 43.2 39

8 6 Lateral stiffness at the tip 3 kN/m 59 110 85 85 65 1309 7 Total mass 4 kg 1.409 1.385 1.409 1.364 1.222 1.1

10 8 Lateral stiffness at brake pivots 2 kN/m 295 550 425 425 325 650

11 9 Headset sizes 5 in1.0001.125

1.0001.1251.250

1.0001.125

1.0001.1251.250

1.0001.125 NA

12 9 Steertube length 5 mm

150180210230255

140165190215

150170190210

150170190210230

150190210220 NA

13 9 Wheel sizes 5 list 26in 26in 26in26in

700C 26in 26in

14 9 Maximum tire width 5 in 1.5 1.75 1.5 1.75 1.5 1.515 10 Time to assemble to frame 1 s 35 35 45 45 35 85

16 11 Fender compatibility 1 list Zefal none none none none all17 12 Instills pride 5 subj 1 4 3 5 3 518 13 Unit manufacturing cost 5 US$ 65 105 85 115 80 100

19 14 Time in spray chamber w/o water entry 5 s 1300 2900 >3600 >3600 2300 >360020 15 Cycles in mud chamber w/o contamination 5 k-cycles 15 19 15 25 18 35

21 16,17 Time to disassemble/assemble for maintenance 3 s 160 245 215 245 200 425

22 17,18 Special tools required for maintenance 3 list hex hex hex hexlonghex

hex,pin

wrnch23 19 UV test duration to degrade rubber parts 5 hours 400+ 250 400+ 400+ 400+ 250

24 19 Monster cycles to failure 5 cycles 500k+ 500k+ 500k+ 480k 500k+ 330k25 20 Japan Industrial Standards test 5 binary pass pass pass pass pass pass

26 20 Bending strength (frontal loading) 5 MN 55 89 75 75 62 102

Metric Units Mar

gina

l Val

ue

Idea

l Val

ue

1 Attenuation from dropout to handlebar at 10hz dB >10 >152 Spring pre-load N 480 - 800 650 - 7003 Maximum value from the Monster g <3.5 <3.24 Minimum descent time on test track s <13.0 <11.05 Damping coefficient adjustment range N-s/m 0 >2006 Maximum travel (26in wheel) mm 33 - 50 457 Rake offset mm 37 - 45 388 Lateral stiffness at the tip kN/m >65 >1309 Total mass kg <1.4 <1.1

10 Lateral stiffness at brake pivots kN/m >325 >650

11 Headset sizes in1.0001.125

1.0001.1251.250

12 Steertube length mm

150170190210

150170190210230

13 Wheel sizes list 26in26in

700c14 Maximum tire width in >1.5 >1.7515 Time to assemble to frame s <60 <3516 Fender compatibility list none all17 Instills pride subj >3 >518 Unit manufacturing cost US$ <85 <6519 Time in spray chamber w/o water entry s >2300 >360020 Cycles in mud chamber w/o contamination k-cycles >15 >3521 Time to disassemble/assemble for maintenance s <300 <16022 Special tools required for maintenance list hex hex23 UV test duration to degrade rubber parts hours >250 >45024 Monster cycles to failure cycles >300k >500k25 Japan Industrial Standards test binary pass pass26 Bending strength (frontal loading) MN >70 >100

We Also Asked You to Assign Marginal and Ideal Values

The Product Specs Process

• Set Target Specifications– Based on customer needs and benchmarks– Develop metrics for each need– Set ideal and acceptable values

• Refine Specifications– Based on selected concept and feasibility testing– Technical modeling– Trade-offs are critical

• Reflect on the Results and the Process– Critical for ongoing improvement

Now What? Can you get there from here?

• Make a functional model of the product• Make a technical model of the product• Make a cost model of the product• Refine the specifications, making trade-offs

where necessary.• Flow down the specifications as appropriate• Reflect on the results and the process.

Functional Analysis/Modeling

• Your text does not do the functional analysis until concept generation.

• There are several methods for Functional Analysis– Product Function (Top-Down)– FAST (Functional Analysis System Technique) (Top-Down)– Subtract and Operate Procedure (Bottom-Up)

• Functional analysis is NOT unique– A way of structuring your thinking about the problem– A way of aiding PDS development– Can also aid in concept generation

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.

What are we going to do today?

• Define Functions and Sub-functions• Define Systems and Sub-systems• Map Functions through a System• Apply Subtract and Operate Procedure to

Develop a Function Tree

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

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 and Systems• Functions and sub-functions definitions parallel those of

systems and sub-systems but do not necessarily have a one-to-one correspondence.

• A sub-system may serve more than one sub-function.– Exhaust plumbing sub-system contains and transfers engine

exhaust

• Several sub-systems may be needed to provide a single sub-function.– Pump, fan, and radiator sub-systems cool engine

• Several sub-functions can be distributed among several sub-systems.– Sensors, wires, computer, and actuators control, diagnose, and

prognosticate engine function

Functions

Functions should be expressed in terms ofmeasurable effects

Typical function expression: “active verb – noun”

“increase pressure”“transfer torque”

“store energy”“cool liquid”

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 : Make smallFunctional 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.

Goals vs Constraints

• A Constraint is a requirement that MUST be met.– If a constraint is not met, the design is NOT

USABLE– Meet FDA requirement for biocompatability

• A Goal is a requirement that may be used to make trade-offs in design decisions.– Minimize cost– Maximize speed

Form Function Flow

Hot Water

Water Heater

Cold Water

Electric Current

Heats WaterHot WaterCold Water

Electric Current

Form

Function

FlowR

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

• Functional relationships can be described using just 3 elements.

• In a function, an object is acted on by a tool.

• The action typically involves a parameter change for the object.

Tool ObjectAction

Functional Analysis

Auto PassengerTransports

System: Automobile

Chair PersonSupports

System: Chair

Oven FoodHeats

System: Oven

Component

Super System

ProductUseful

Harmful

B

D

Monitors Insufficient

Dispenses

Positions Required

Actuates Excessive

Holds E

C

A

Functional Analysis Diagram• Start with your knowledge of the product (or

process) system.• Draw a diagram of the elements and functions.

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

Liqu

id

Con

tain

Liq

uid

Insu

late

Liq

uid

Con

tact

Air

Inte

rfac

e H

and

Insu

late

Han

d

Tra

nsm

it Lo

ad

Insu

late

Sup

port

Sup

port

Con

tain

er

Inte

rfac

e M

outh

Con

t. L

iq.

/ In

tf.

Mou

nth

Con

t. L

iq.

/ In

sl.

Han

d

Con

t. L

iq.

/ T

rans

. Lo

ad

Product Functions

Cu

sto

mer

Nee

ds

Example: Washing Machine from Freshman Design

Washer

Dirty Clothes

Clean Clothes

Loosen

Dirt

(Fill)

Dirty

ClothesSeparate

Dirt

(Agitate)

Remove

Dirt

(Rinse)

Clean

clothes

Water Detergent

HowSpecific ?

This washer should loosen 85% of dirt particles or washer should have inputs for water and detergent assuming that this is the desired mode

Clean Water

Dirty Water

But Wet!!

Remove

Dirt

(Rinse)

Clean

wet

clothes

Clean Water

Dirty Water

Remove

Water

(Spin)

Clean, Damp

Clothes

FAST• Brainstorm all functions that product will

serve in the eyes of the customer.• Select the overall product function• Distinguish between the basic function and

the secondary functions• Arrange functions in a critical path

How? Why?

HigherOrder

Function

BasicFunction

RequiredSecondaryFunction

RequiredSecondaryFunction

AssumedFunction

GrinderOperator

Coffee Beans

EnergySystem

Ground Coffee

Chamber

SealSlicing blade

Figure 5.5, Otto and Wood

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.

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

Scan in Figure 5.6 Otto and Wood

Quiz for TodayCreate a functional diagram for a squirt gun using the subtract and operate procedure.

http://entertainment.howstuffworks.com/water-blaster1.htm

The Classic Water GunBefore the 1980s, water guns had fairly limited capabilities. Handheld pistols could only shoot water a short distance. They shot a weak, narrow stream and you had to run to a spigot to refill them after every shoot-out. These guns are still terrific toys, of course, and they're a wonderful demonstration of basic plumbing principles. In a classic squirt gun, there are just a few basic parts: 1.There is a trigger lever, which activates a small pump. 2.This pump is attached to a plastic tube that draws water from the bottom of the reservoir (in most cases, the reservoir is the entire inside of the gun). 3.The pump forces this water down a narrow barrel and out a small hole at the gun's muzzle. 4.The hole, or nozzle, focuses the flowing water into a concentrated stream. For the purposes of your quiz, assume that there is a trigger lever, plastic tube, reservoir, narrow barrel, nozzle, body and pump. Furthermore, you may assume that the pump has both one-way valves attached to it and that the pump and valves act as a unit.

The only complex element in this design is the water pump, and it's about as simple as they come. The main moving element is a piston, housed inside a cylinder. Inside the cylinder is a small spring. To operate the pump: You pull the trigger back, pushing the piston into the cylinder. This compresses the spring, causing it to push the piston back out of the cylinder when you release the trigger. These two strokes of the piston, into the cylinder and out again, constitute the entire pump cycle. The downstroke, the piston pushing in, shrinks the volume of the cylinder, forcing water or air out of the pump. The upstroke, the spring pushing the piston back out, expands the cylinder volume, sucking water or air into the pump. In a water gun, you need to suck water in from the reservoir below and force it out through the barrel above. In order to get all the water moving through the barrel, the pump must only force water up -- it cannot force water back into the reservoir. In other words, the water must move through the pump in only one direction. The device that makes this possible is called a one-way valve. The one-way valve in a basic squirt pistol consists of a tiny rubber ball that rests neatly inside a small seal. There are two one-way valves: one between the reservoir and the pump, and another between the pump and the nozzle.

Name:_________________________CM:______Name:_________________________Name:_________________________

Trigger Lever

Plastic Tube

Reservoir Narrow barrel

Nozzle Body Pump

List Functions identified, but don’t attempt to structure your solution.

Now What? Can you get there from here?

• Make a functional model of the product• Make a technical model of the product• Make a cost model of the product• Refine the specifications, making trade-offs

where necessary.• Flow down the specifications as appropriate• Reflect on the results and the process.