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Assembly System Design Te

Goals of this class

Introduce system design methods

Understand the things that must be cons

Look at two ways to approach it

Learn about SelectEquip

Asst Sys Des Tech 11/16/2004 Daniel E Whitney

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Assembly System Design Te

Assembly system design algorithms e

They solve the Equipment Selection

Assignment problem

Methods include dynamic programmi

travelling salesman, mixed integer-linprogramming, and a heuristic called A

These algorithms will design an assem

process line to meet average producti

requirements, adjusted for a fixed % u

Detailed simulation is needed to verif

rate and study queues and other issueAsst Sys Des Tech 11/16/2004 Daniel E Whitney

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What to Model

The tasks that need to be done

The number of units needed per year

What resources are available or applicable t

What each resource costs to buy

What tool it needs for each task

How long it will take to do the task, change tool

What is its uptime and other operating character

Time for transport from station to station Reuse of a resource for several tasks

Reuse of tools at one station


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History

Heuristics by R E Gustavson at Drape

Cook at MIT in 1970s Solutions based on OR techniques by

and OR Center students Terry Huttner, 1977 - mixed linear-integ

programming

Bruce Lamar, 1979 - bus routing algorith

Carol Holmes, 1987 - multiple productsprogramming

Curt Cooprider, 1989 - uncertain deman

programming Holmes-Cooprider method reprogram

Mike Hoag, 2001.


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System Selection Crite

Minimize annualized cost

= unit labor cost + annualized cost of cap

Systems can be forced to be all manu

or all fixed automation just by removresource classes

A wide variety of preferences can be

accommodated this way


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Summary of Required In

Info about assembly resources with co

time, and rho or installed cost factor

rho relates total cost to equipment cost

Info about assembly tasks with operattool number for each resource

Annual production volume, labor cost

acceptable rate of return, number of sh

Rate of return expressed in annualized co


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________

________

________

__________ __________ __________ __________ __________

Title Date

Working days/year ________ Annualized cost factor

Shifts available ______ Avg loaded labor rate ($/hr)

Station-station move time (s)

Resource data set name: _________ Task data set name:______

For each resource: When a resource can be used:

C hardware Cost ($)

rho installed cost/hardware cost Operation Tool

e % uptime expected time (s) number

v operating/maintenance rate ($/hr)Tc Tool change time (s) Hardware cost

Ms Max # stations/worker

NOTE: SEE FIG 14.8 OF CONCURRENT DESIGN AND PP 434-435

Resource:

......

....... C_______ C_______ C_______ C_______ C_______

......... rho_____ rho_____ rho_____ rho_____ rho_____

........... e_______ e_______ e_______ e_______ e_______

........ v_______ v_______ v_______ v_______ v_______

......... Tc______ Tc______ Tc______ Tc______ Tc______

Task: Ms______ Ms______ Ms______ Ms______ Ms______

1 | | | | |

2 | | | | |

3 | | | | |

4 | | | | |

5 | | | | |

6 | | | | |

7 | | | | |

8 | | | | |

9 | | | | |

10 | | | | |


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Asst Sys Des Tech Daniel E Whitney11/16/2004

NAME

DATE

PREPARED BY

NOTE: SEE FIG 14.7 OF CONCURRENT DESIGNSHEET OF

PAGE 433

TASK SEQUENCE

TASK TYPE INSPECTION

P = PLACE/ORIENT B=BOLT TORQUE

T=TIGHTEN BOLT, SCREW, ETC G=GAUGE DIMENSION

I=INSERT PART(S) C=COMPARISON

M=MEASURE

S=MODIFY SHAPE

A=ALIGN

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Asst S s Des Techy 11/16/2004 Daniel E Whitney

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Asst Sys Des Tech Daniel E Whitney11/16/2004

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Basic Nominal Capacity Equ

/

actual sec/op < required sec/op -> happiness

# operations/unit * # units/year = # ops/yr

# ops/sec = # ops/yr * (1 shift/28800 sec)*(1 day n sh

cycle time = 1/(ops/sec) = required sec/op

equipment capability = actual sec/op

required sec/op < actual sec/op -> misery (or multipl

Typical cycle times: 3-5 sec manual small parts5-10 sec small robot

1-4 sec small fixed automation

10-60 sec large robot or manualAsst Sys Des Tech 11/16/2004 Daniel E Whitney

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How the Holmes-Cooprider

Works

The maximum takt or cycle time is cabased on annual volume requirement

Each resource is tested to see if it canwithout running out of time, two task

etc. A network is built where pairs of nodand arcs are resources

Each arc has a cost based on investme

labor (labor cost based on time used) The shortest path through the network

of selected resources and the tasks the


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Network

$10K

$20K

$15K

$10K

$7K$7K

$14K

Shortest path


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Network Models of Assembly

Model of system as flows in a network

Represents equilibrium state

Based on probabilities and costs1.0, $10 0.9, $20

0.1, $50

Outbound probabilities add to 1.0 Equilibrium solution gives average co

through and average flow on each bra


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Equations

pij=pr of going from node i to node j

cij=cost of going from node i to node j

fij=flow from node i to node j

yi = total flow out of node i

=fij yipij

where we must have Node i N

pijcij

!

j

pij = 1 for each i

Conservation of flow at node j:

y =yj jpjj +!ykpkj +xj Y=k. j

xj=flow into node j from outsideSolution: Y = [

pjj=0 cost


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Example System: an assembly w

subassemblies and several test an

stations

Rework

#1$1

0.1Fail

#1

ly #1 ly #2

ild #2le

#2

l

NewParts

Build #1$10

Test 0.9 OK

Rework

$40

Subassemb Subassemb

BuAssemb#1 To #2

$20

Rework

$10

Subassy #2 A ready Done

Rework#1with #2

the Assy$50

#

Attached$80


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Network Equivalent of Ex

0.9

$0.002

0.02

$50 $80

1 1 0.9 1 1NewParts $0 1 $11

$03 $20 4 $22

0.1 0.1$40 A $10 B

A Build/repair Subassembly #1 and Test B Build/repair Subassembly #2 and Test C Repair/rebuild #1 While Attached to #2


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Matlab SolutionP=zeros(8)

C=zeros(8)

%Arc probabilities:

P(1,2)=1; Y=inv(eye(8)-P')*X

P(2,1)=.1; Y =

p(2,3)=.9; 1.1136

P(2,3)=.9; 1.1136

P(3,4)=1; 1.1162

P(4,5)=1; 1.1390

P(5,3)=.1; 1.1390

P(5,1)=.002; 0.0253

P(5,6)=.02; 0.0253

P(5,8)=1-P(5,6)-P(5,3)-P(5,1); 1.0000

P(6,7)=1; YY=[Y Y Y Y Y Y Y Y]P(7,4)=.9; F=box(YY,P)

P(7,6)=.1;

X=[1 0 0 0 0 0 0 0];

X=X'Asst Sys Des Tech 11/16/2004 Daniel E Whitney

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Equilibrium Flows

F =

0.0000 1.1136 0.0000 0.0000 0.0000 0.0000

0.1114 0.0000 1.0023 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 1.1162 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 1.1390 0.0000 0.0023 0.0000 0.1139 0.0000 0.0000 0.0228

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0228 0.0000 0.0025

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0


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Cost Solution

%Arc costs:

C(1,2)=11;

C(2,1)=40;

C(3,4)=20;

C(4,5)=2;

C(5,1)=50;

C(5,3)=10;

C(5,3)=10;

C(5,6)=80;

C(6,7)=11;

C(7,6)=40;

cost=sum(sum(box(C,F)))cost =

$44.7608Cost without rework = $33

%FF = total flow in system

FF=sum(sum(F))

FF=5.6720

%EX=excess flowEX=FF/5

EX =

1.1344

Total flow without rework

Capacity devoted to rewor


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Key Characteristics

Goals of this class

Introduce Key Characteristics (KCs)

Define the notions of KC delivery and KC delive

Understand the relationship between KC deliveryto-part location

Appreciate how many KCs an assembly can haveconcept of KC conflict

See some examples

KCs_04.ppt

9/13/2004 Daniel E Whitney

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Key Characteristics (KC

Key characteristics are product requirement

attention because

they are critical for performance, safety, or regul

AND

they are at risk of not being achieved due to proc

Usually, KCs are geometric relationships be

on non-adjacent parts

Two basic issues for KCs are

priorities

flowdown

KCs_04.ppt


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Chain of Delivery of Qu

Image removed for copyright reasons.

Source:

Figure 2-1in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Desi

and Role in Product Development. New York, NY: Oxford University Press, 200

No single part delivers the KC.

KCs_04.ppt 9/13/2004 Daniel E Whitney

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Chains Deliver KCs

KCs are delivered by chains that must o

repeatibly

Chains are made up of:

physical elements: parts, sub-assemblies, to

the associated organizations (supply chain)

the capability of the processes (technology)

Each KC is delivered when its chain is c

KCs_04.ppt


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KC Priorities

Everything is important to someone

KCs should be confined to things thaimportant but are at some risk of not achieved

Usually, manufacturing or assembly considered to be the main threat

So there is a direct link between KCsassembly tolerances

If there is no systematic process for iKCs, and if priorities are not assignedtend to proliferate

KCs_04.ppt


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When Can Key Characteristic

During concept design, to capture custo

During system engineering, to flow dowto lower levels of the design process

During detail design, to deliver reqmtsand process planning

During supplier selection and preparatito define deliverables

During program management, to track achievement of requirements


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Source:

Figure 1-1in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Design, Manufa

and Role in Product Development. New York, NY: Oxford University Press, 2004. ISBN: 01


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Source:Figure 1-2in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Design, Manu

and Role in Product Development. New York, NY: Oxford University Press, 2004. ISBN: 0


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Stapler KCs


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Each KC is Delivered by a

C

STAPLES

PUSHER

Chain

Key Charac


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Key Characteristics and the

Diagram

mage removed for copyright reasons.

Source:

Figure 1-3in [Whitney 2004] Whitney, D. E.

Image removed for copyrigh

Source:

Figure 1-4 in [Whitney 2004

Mechanical Assemblies: Their Design, Manufacture, Mechanical Assemblies: Th

and Role in Product Development. and Role in Product Develo

New York, NY: Oxford University Press, 2004. New York, NY: Oxford Univ

SBN: 0195157826.

Liaison Diagram KCs


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Only Some Liaisons Matter

Delivery


Source:




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The Delivery Path for Each St


Source:




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Optical Disk Drive KC

Imagesremoved for copyright reasons.Source:

Figure 2-7in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Design

and Role in Product Development. New York, NY: Oxford University Press, 2004.


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Some Statistics

A person at GM said

60% of body sheet metal tolerances can be met

40% must be altered to meet shop capabilities

A patent from Boeing on tolerancing says thparts are involved in a tolerance chain (prob

the length of a KC chain for us)

A survey of 600 consumer products by Ulri

reveals that about 6 parts are involved in de

functions that differentiate the product in th

You dont get real numbers like this every d

KCs_04.ppt


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How Parts Locate Each Other to

Quality at the Customer Le

BODY TO

HINGE FLAP1: 6 DOF

HINGE FLAP 1 TO

HINGE FLAP 2: 5 DOF

HINGE FLAP 2 TO

DOOR: 6 DOF

CRAFTMANSH

DOOR

CAR BODY

KC=


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DOOR FRAME

PERIMETER

SHAPE ACCURACY

BODY ASSEMBLY

METHOD AND

EQUIPMENT

BODY PARTS

ASSEMBLY

BODY PARTS

FABRICATION

CUSTOMER

PERCEPTION

OF DOOR

UNIFORMITY OF FLUSHNESS OF DOOR CLOSING WATER LEAKAG

DOOR-BODY GAPS DOOR-BODY FORCE AND WIND NOISSURFACES

SEALTIGHTNESS

DOOR-BODY DOOR-BODY

ALIGNMENT ALIGNMENT

UP/DOWN AND IN/OUT

FORE/AFT

DOOR MOUNTING

METHOD AND

EQUIPMENT

DOOR ATTACHMENT HINGE ATTACHMENT SEAL ATTCHMENT

TO BODY TO DOOR TO BODY

DOOR PERIMETER DOOR THICKNESS

SHAPE ACCURACY ACCURACY

DOOR ASSEMBLY

METHOD AND

EQUIPMENT

DOOR PARTS

ASSEMBLY

DOOR PARTS

FABRICATION


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Source:

Figure 2-8in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Design, Man

and Role in Product Development. New York, NY: Oxford University Press, 2004. ISBN


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Door Assembly


Source:

Figure 2-10in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their De



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Car Door Design KC

B PillarA Pillar

Outer

Fender

Hinges

Latchbar

A Pillar

OuterFender

Appearanceon placemeouter panel

Weatheron placeinner pa

fore-aft

up-down

Side View Top V

Appearance KCdoor tolerances and fit = uniformity of

this gap


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Two Door Methods - There A

DOORHINGES

HINGE-MOUNTING FIXTURE

= 6 DOF LOCATION

DOHINGES

DOOR MOUNT

Assembly Step 1a Assembl

HING

DOORHINGES

HINGE-MOUNTING FIXTURE

LOCATOR

CONES

Assembly Step 1b Assembl


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KC Conflict in Door Asse

KCs_04.ppt 9/13/2004

Impossible

o assemble

Daniel E Whitney

Align door inner

to seal, then attach

inner to frame

Align door outerto frame gaps, then

attach outer to inner

Attach door outo door inner,

aligning parts

Mount door (inner+outer)to frame and align seals,

possibly misaligning gaps

his way!

Difficult

KCs this

Not enough independe

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Ford Hinge Mounting


Source:




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Ford Hinge Mounting Fix

Photo removed due to copyright restrictions. (Detail of car door front and rear loca


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Door on Hinge-Mounting F

Photo removed due to copyright restrictions. (Detail of front and rear c


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Mustang Body in Whi

Photo removed due to copyright restrictions. (Detail of car door front a


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An Interesting Wrinkl

Doors are usually installed on a car be

painting and removed for trim installa you can grab a door rigidly (accurately) w

no paint to scratch

it is easier to install stuff on/in the door a

the doors are separate The challenge is to get them back on i

place without the benefit of assembly

It is done cleverly with the hinges

install door+hinges to car, remove door f

remove a temporary hinge pin, reinstall a

check which bolts have paint to see how


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GM Take-apart Car Door H

Photo removed due to copyright restrictions. (Detail of car door hinge


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Goals of this Course

Understand a systematic approach to assembly problems

Appreciate the many ways assembly product development and manufactur

See a complete approach that includesystems engineering, and economic a

Get a feeling for what is technologica

Practice the systematic process on a s

group project of your own

7/25/2005 Class I Intro _04 Daniel E Whitney 1997-2004

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Assemblies are System

Assembly is inherently integrative

Assemblies can be designed top-down

Decomposition and interface manage

Assemblies exhibit non-colocation of

effect

Assemblies also violate a hidden assu

big causes have big effects while shave small effects


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Chain of Delivery of Qu

Shows clearly who delivers what andhow long the chains of delivery are


Source:

Figure 1-8 in [Whitney 2004] Whitney, D. E. Mechanical Assemblies:

Their Design, Manufacture, and Role in Product Development.

New York, NY: Oxford University Press, 2004. ISBN: 0195157826.


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Course Mechanics

Class lectures and discussions Mon & Wed 1:0 Textbook at the Coop: Mechanical Assemblie

Manufacture, and Role in Product DevelopmenUniversity Press, 2004

Reading and homework assignments on MIT S

A group project to be done in phases during the

Homework

6 project reports

4 problem sets

A mid-term and a final project presentation No quizzes or final exam Grade formula: 1/3 on homework, 1/3 on projec

midterm and final presentation7/25/2005 Class I Intro _04 Daniel E Whitney 1997-2004

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Project Guidelines

Buy a small assembled product costing no m

and having 10 to 20 parts Be sure you can take it apart and put it baBe sure you can take it apart and put it ba

Save the packaging and instructionsSave the packaging and instructions

SDM students can use a product from wo

You will analyze it in detail technically and and design an assembly line

Wednesday Sept 15 hand in a description of bought and names/e-mails of team members

Examples: hand-held power tools, small cloc

Luxo lamps, small home appliances, toys Schedule a time to show it to me for an hour

Hand in Request for Payment to get reimbur


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Toy


Source:

Figure 13-10 in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: T

and Role in Product Development. New York, NY: Oxford University Pres


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Class Schedule - Typic

Monday Oct 28 Class 13 Assembly Wednesday Oct 30 Class 14

in the Large - basic issues, Architecture, flexibility

economics, step-by-step process

Monday Nov 4 Class 15 Design for Wednesday Nov 6 Class 16 A

Assembly Theory, Examples and System Design Issues: Kinds

video assembly lines and equipmen

production volume, cycle tim

Class 18

Monday Nov 11 Holiday No Class Wednesday Nov 13 Class 17

term presentation of student p

covering first three reportsMonday Nov 18 Class 19 Assembly Wednesday Nov 20 Class 20

in the large: Workstation design Assembly System Design So

issues

Monday Nov 25 Class 21 Discrete Wednesday Nov 27 Class 22

Event Simulation Economic analysis of assemb

systems

Monday Dec 2 Class 23 Wednesday Dec 4 Class 24 7Outsourcing, & supply chain Wing Case Study

management

Monday Dec 9 Class 25 Student

project presentations


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Daniel E Whitney 1997-2004Intro_04

Each report

generates info

for later

reports

7/25/2005 Class I

j

Wednesday Dec 4 Sixth project report due:

Economic analysis of this layout and Discrete event

simulation

Wednesday Nov 27

Fifth pro ect report due:

Create a floor layout

Wednesday Nov 20

Fourth project report due:

Design a workstation

Wednesday Nov 13

Third project report due:

Choreograph each assembly step & DFA

Wednesday Oct 30 Second project report due: DFCanalysis of your product

Wednesday Oct 23

Problem set on DFCs due

Wednesday Oct 16

Problem set on tolerances and constraint due

Wednesday Oct 2

Problem set on 4x4 matrices due

Wednesday Sept 25

First project report due:

Completely describe the product

Wednesday Sept 18

Problem set on rigid part mating due

Wednesday Sept 11

Student project descriptions due

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Why is Assembly Import

Assembly is inherently integrative brings parts together

brings people, departments, companies to

can be the glue for concurrent engineerin

Assembly is where the product comes there arent many one-part products

Assembly is where quality is delivere

quality is delivered by chains of parts,

single most important part

A paradox: assembly is not a big cost


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Example of This LinDenso makes many kinds of panel meters for T

Toyota orders different ones in different amou

Denso designed an assembly family of metemake any quantity of any kind at any time by s

right parts. Assembly interfaces were standard

parts. The result is assembly-driven manufact

Images removed for copyright reasons.

Source:




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Need for a Systems Appr

We design parts, we dont design assem

We spent all day identifying the reasons

features on certain parts relate to features

parts Tolerances are those little numbers that

put on the drawing before the boss will s

You cant have both cosmetic quality an

quality (car doors)


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Outline of Requirements-Driv

by-Step Process

Assess business context

managements objectives and constraints

character of the product

Analyze assembly in the small

understand each part, determine risks recommend redesigns

Analyze assembly in the large

revisit business context

take system view: technical and economi

design processes: assy sequence, line lay

make final recommendations


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Manual vs Automated Asse

People just do it Machines cant just do it

It was hoped that robots could just d

Early robot research focused on imita

people do in general behave flexibly

use their senses

react to the unexpected

fix mistakes that should not have othe first place


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Robotics as a Driver

Robotics raises a number of generic issues:

flexibility vs efficiency

generality vs specificity responsiveness or adaptation vspreplann

absorption of uncertainty vs elimination

lack of structure vs structure


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Sony Video

Compare 20+ years later:

multiple parts feeders at one station tool changer head

4 - 6 sec operation time per part

It is a complete solution

robot and tool set (VCR and school of VCR

part tray loader

transport

controllers Used for cameras, VCRs, Walkmen, d


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Understand Each Step

Take the product apart (or use drawings if thats al

Get really familiar with every part and its roassembly (story: Yes, Alex)

Make a structured bill of materials

Draw a picture (2D is OK) of each part

Make an exploded view drawing Choose any convenient assembly sequence

Study each part mate and draw it, noting ea

each feature where the parts touch during as

Note where the part can be gripped Note how the part can be fixtured before as

Note any problems that could occur

Class 2 Assy motions 9/7/2004 Daniel E Whitney 1997-2004

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Do Conventional DFA

The issues are: (Boothroyd except wh

assembling each part feeding/presenting

handling/carrying/getting into position

inserting without damage, collisions, fumblin

reducing part count (driven by local eco two adjacent parts of same material?

do they move wrt each other after assembly

is disassembly needed later (use, repair, insp

the part is a main function carrier?(Fujitsu)

if not, consider combining them (but see DF are there too many fasteners? (but see DFA

identifying cost drivers (Denso)


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Identify Necessary Experi

Usually address high risk areas

Determine physical feasibility

Determine economic feasibility

Generate metrics for successful assemmeans for detecting failures on the fly

cycle time

checks for part correctness/presence/pla

avoidance of parts damage

awareness of potential undocumented so

trouble


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Recommend Local Design Imp

These address the high risk areas as w

physical and economic feasibility

There usually is no strategic or system

these kinds of improvements

Assembly in the large addresses su


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Laptop Heat Remova

Fan

Radiator


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Gateway Laptop, 200

HEAT PIPE

BATTERY BAY

DVD

CARD

SLOT

HDD

ME

MO

RYOTHER

STUFF

CPU


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Over-designed Part

Imagesremoved due to copyright restrictions. (Photos of hinge mounts an


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Gross and Fine Motion

Assembly alternates between two kin

motions:

Gross motions

Fine motions

need high accuracy

basically used for transportare fast and do not need high accuracy

large compared to size of part

are likely to be slower than gross motion

small compared to size of partClass 2 Assy motions 9/7/2004 Daniel E Whitney 1997-2004

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Characteristics of Gross and Fi

Parts do not (should not) contact during

Parts normally contact during fine moti

Fine motion is basically a series of cont


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Nature of Gross Motio

Errors: Preplan

could happen - is rew

they can be seenbut - errors

not felt until too late catas

people use sensors - low co

machines use them

preplanning - saving

many

- characstruc

loop


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Nature of Fine Motion

Errors: Preplan

are unavoidable for is not

reasonable cost even t

they can be feltbut stop s

not seen cost o

they generate

signals that can be

used to correct them

them

as the

a closappro


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Class 2 Assy motions Daniel E Whitney 1997-20049/7/2004

Multi-axis Force-Fine Motion

Typicall

matrix re

task coo

comman

x =

Typicall

matrix resensed p

response

x =

=

Source:Figure 9-2 in [Whitney 2004] Whitney, D. E.

Mechanical Assemblies: Their Design, Manufacture,

and Role in Product Development .

New York, NY: Oxford University Press, 2004. ISBN: 0195157826.


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Differential Motion Analy

L L1

2

1.41

2 L

X direction: = - 0.707 2 LY direction: = 1.414 1 L + 0.707 2 L

0 -0.707 L

J =

1.414 L 0.707 L

0.707/L 0.707/L

J-1 =

-1.414/L 0[ ]][If V=[1,0]T, th2=-2 1 for all jo

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Active Force-Motion Str

Image removed for copyright reasons.Source:




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Closed Loop Force-Motion

Original Motion

Command

Modified Motion

CommandJ-1

x

Robot !!!! dt J

SensorKF

-

Actually modeled and analyzed as a sample

This allows us to single step through histo

the dynamics as carefully as we want.

.

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Force-Motion Stability

Stability Criterion:

KF KE T < 1

Essentially means that not all the accum

contact force can be removed during th see next slide

Problem is made worse by stiff couplin

environment

Problem is made better by faster samppoint

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The Stability Criterion in W

KFKET< 1 (1)

Xi + 1 =ViT

Fi + 1 =KEXi + 1

Vi =KFFimultiply both sides of (1) by

KF(KEViT) < Vi

KFFi + 1

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Motions Made by Choice

Diagonal KF creates damping, nulling feed

Cross terms in KF turn sensed force into rotorque into translation

Box packing, putting records on turntables


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Lateral Error Can Become Ang

with Disastrous Resul


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DFA

Goals of this class:

Place DFA in context

Learn basic principles of Design for Ass

Understand background and history

Understand its strong and weak points

DFA03.ppt 11/2/2004 Daniel E Whitney

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The Multiplier According to F

or: Why Is DFM/DFA Imp

For every product part, there are abou

manufacturing equipment parts*

Or, for every toleranced dimension or

product part, there are about 1000 tol

dimensions or features on manufactur

equipment

Such equipment includes fixtures, tdies, clamps, robots, machine tool ele*Note: Fords estimate is 1000, GMs is 1800. Both are in


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A Few Quotes

Just because you can make somethingmean you can manufacture it.

Its very hard to make cheap [low cos

get buried by your mistakes.

I dont understand why it wont assempassed inspection.

Word came down that we couldnt us

we used snap fits. Then word came d

had to pass a drop test. So we droppe

fell apart...


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History of DFA

Deep background in Group Technology

Coding and classification schemes European design tradition

Value Engineering

each part must be justified

Boothroyd

part feeding physics - 1960s

part handling and insertion experiments- 19

assertion that assembly cost = 30 - 50% of m DFA methodology and software - 1970s-8

switch to assertion that parts are the main c

= less cost, even if those parts are more comDFA03.ppt 11/2/2004 Daniel E Whitney

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Traditional DFA The issues are: (Boothroyd except whe

assembling each part -estimating and redu feeding/presenting

handling/carrying/getting into position (Sony e

inserting without damage, collisions, fumbling

reducing part count (originally driven by l

analysis, now driven by part cost itself) two adjacent parts of same material?

do they move wrt each other after assembly

is disassembly needed later (use, repair, inspec

is the part a main function carrier?(Fujitsu, Luc

if not, consider combining them (but see Archi

are there too many fasteners?

- identifying cost drivers (Denso)DFA03.ppt 11/2/2004 Daniel E Whitney

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How to Do Traditional D

Make a structured bill of materials

Identify every part mate and understand it

Choose a reasonable assembly sequence

Use the tables to estimate handling and ma

Label theoretically necessary parts, exclud

Calculate

3* # of theoretically nassembly efficiency =

total predicted assem

This ranges from 5% for kludges to 30% f


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DFA Spreadsheet

On SoanSpace there is a folder called

Software

In it is DFA.xls with the handling and

data from the previous two slides

Enter your code numbers and labor ra

and the sheet will calculate times and


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Heavy Duty Staple Gu


Source:

Figure 15-25in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Dand Role in Product Development. New York, NY: Oxford University Press, 200

Assembly efficiency = 17% before imp

= 25% after impro

= 30% with someDFA03.ppt 11/2/2004 Daniel E Whitney

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Low Cost Staple Gun


Source:


Assembly efficiency = 31%

Contains many of the suggested imp

But is it a better staple gun?


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Part Count TradeoffsPARTS CONSO

ONE PART PER FEWER PARTS FUNCTION FASTEN

MANYSIMPLEPARTS

LOTS OFINTERFACESIN ASSEMBLY

EXTRA WEIGHT,EXTRA FAULT

OPPORTUNITIES

EXTRA CHANCESFOR ERRORS

LOTS OFLOGISTICS,

FAB ACTIVITY,& ASSY ACTIVITY

EXTRA"SUPPORT"

COST

FLEXIBILITYIS POSSIBLE

DURINGASSEMBLY

QUALITY ISCREATEDDURING

ASSEMBLYPART COUNT TRADEOFFS

FEWER BMORE COM

PARTS

MORE FUNCSHARIN

PARTS TALONGER DESIGN APROTOTY

MORE ACTIDURING FLESS DUR

ASSEMB

PARTS COMORE

FEWER OPPOR

FOR ON-LINE FL

QUALITY CREDURING F


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Manual vs Automatic Assem

Whats easy for a person

reorienting the assembly

quickly eyeballing the part (story about b

Whats easy for a machine

picking up little parts using tools that are like tweezers

Part jams occur most often in feeder t

Denso: perfect parts dont jam!

A different balance between gross momotion times

Different ways of inspectingDFA03.ppt 11/2/2004 Daniel E Whitney

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Complex Molded Par



Source:

Figure 15-11in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their D


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Home Hot Water System Fam

11/2/2004DFA03.ppt Daniel E WhitneyPoschman


Source:

Figure 15-14in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Des


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Melt-Core Technology for Water H

PoschmanDFA03.ppt 11/2/2004 Daniel E Whitney


Source:

Figure 15-15in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Desand Role in Product Development. New York, NY: Oxford University Press, 2004.

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Questions of Scope

When can DFA be applied?

When should DFA be applied? When

the right approach?

What information is needed before D

applied?

What should the designers priorities

Can/should DFA be separated from product design?


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DFM-DFA Strategie

DevelopmentTimeNotCritical

DevelopmentTimeC

ritical

Low Lifetime Production Volume

Example Products:

High performance computers

Telecommunications equipment

DFM Strategy:

Avoid long lead time tooling

Use standard components

Minimize production risk

Example Products: Example Produ

Machine tools Blank videoc

Electrical distribution equipment Circuit break

DFM Strategy: DFM Strategy:

Avoid expensive tooling Use tradition

Use standard components Combine and

Other issues likely to dominate Consider auto

High Lifetime P

Example Produ

Notebook com

DFM Strategy:

Minimize com

complex p

For complex

with fast to

Apply traditi

time-critica

Source: Ulrich, Sartorius, Pearson, Jakiela, DFM Decision-making, Mgt Sci, v


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The Pneumatic Piston Red

Was the original function completely

Was it preserved in the redesign?

*Product Design for Assembly by Boothroyd and Dewhurst, workboo


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The Water Pump Redes

What are the differences between the

designs?

from the POV of product function

from the POV of assembly

What are we looking at in this examp


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Source:

Figure 15-16in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Design,

and Role in Product Development. New York, NY: Oxford University Press, 2004. ISB


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DFA at Sony

Applied to products like Handicams

Our designers take assembly into ac

Method: concept designs are sketched in explode

each concept is subjected to DFA analys

concept selection criteria include DFA s

A Sony engineer made a complete exdrawing of a Polaroid camera in 20 m


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Sony Walkman II Mecha


Source:




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Sony Exploded View


Source:

Figure 15-7in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Deand Role in Product Development. New York, NY: Oxford University Press, 200


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Hitachi Assembly Reliability E

Method


Source:

Figure 15-5in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Deand Role in Product Development. New York, NY: Oxford University Press, 200

Source: Hitachi; Suzuki, Ohashi, Asano, and Miyakawa


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Design for Recycling and


Source:



Source: Kanai, Sasaki, and Kishinami


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Web Sites from Goog

http://www.intel.com/design/quality/pcdesign/

http://www.engineer.gvsu.edu/vac/ (class note

http://www.dfma.com/ (Boothroyd-Dewhurst http://www.johnstark.com/pb18.html (a list of

http://www.munroassoc.com/design.htm (cons


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Flexible Manufacturing Sy

Goals of this class:

Understand goals of FMS

Place FMS in context of manufacturin Understand the history

Take some lessons about appropriate

11/24/2004 FMS Daniel E Whitney 1997-2004

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Background

Batch production - since the Egyptian

Mass production - 1880-1960

Flexible production - ? Lean production - since 1970?


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Computers and Manufact

Numerical control of machine tools R

1950s - see photo gallery along cor

From WW II gun servos

Early 1950s Air Force SAGE system

Computer-aided design R&D at MIT

If the computer can guide the tool, then

shape in its memory


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Numerical Control Techn

Initially one computer for each machi

Computer programmed in APT (AutoProgrammed Tool), a language like L

By the 1970s, a central computer conmachines - DNC (direct numerical co

By the 1980s each machine had its owpossibly loaded with instructions from

computer - CNC (computer numerica


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Job Shops and Flow Lin

Ford style flow lines utilize equipment at a

are inflexible and costly Big initial investment requires years to pay back

Dedicated to one part or a very limited family

At risk if the part is no longer needed

One failure stops the whole line

Job shops are flexible but utilization is low Some asserted that utilization is as low as 5%

Machines time is lost due to setups made on the

Parts time is lost due to complex routing and qu

Big WIP

Flexibility can be defined several ways, inc

Different part mix

Different production rate of existing parts

Different machines or routing if one breaks11/24/2004 FMS Daniel E Whitney 1997-2004

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Past Approaches to Utiliz

Improvement

Faster changeover AKA SMED

Reduction of setups

Standardization

Use of same setup for several parts

Same setup: Group Technology

Classify parts and code them

Design generic tooling, fixtures, and proclass of part

Ignore the differences that do not matter


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Ungrouped and Grouped

www.strategosinc.com/ group_technolog


Images removed due to copyright restrictions.

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The Flexible Manufacturing Sy

This idea sprang up in several places at once i The basic idea was a computer-controlled job

line characteristics

Group technology still important - system aimpart, such as prismatic < 2 ft sq, or rotational lights out operationproductivity

Typical FMS applications today are sihave 3 to 5 machines doing a few opefew kinds of parts


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Sheet Metal Bending Sys

www.mt-muratec.com/ eg/p/fms/fms_yuatu.html


Images removed due to copyright restrictions.

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Yamazaki Mazak

Built lights-out factory in mid 1980s to mak(machine tools) - visited by Whitney in199

Addressed tool proliferation with given too

Addressed system complexity by breaking umany simple cells having identical tasks, id

machines, and identical tool sets

Addressed reliability, in part, by reducing cspeed at night, eliminating tool breakage, th

preventing lights-out operation

American customers want 120-tool capacicarousels - ha ha. Japanese companies are h

Some of this documented by the late Prof JaHBS in cases on Yamazaki


http://www.mazak.jp/english/

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Fanuc

Originally a motor company Built NC machine in 1956!

Developed NC technology in 1960s and 70s

Started building robots in the 1970s

Applied robot controllers to simple CNC m1970s with low cost bubble memory and simcontrols for programming and simulating anoperations

Drove US NC controls makers (GE, Honeyof the market

Addressed needs of small manufacturers anmachines for the first time

Fanuc is still important in the controller and11/24/2004 FMS Daniel E Whitney 1997-2004

http://www.fanuc.co.jp/en/profile/index.htm

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Reconfigurable Manufacturing

Japanese demonstrator system in the included reconfigurable machine tool

Current research looks at entirely recosystems consisting of reconfigurable transport systems (see U of MI RFMS

Advances in machine design techniqu

included Economic analysis includes system li


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Current Status

FMS is a niche technology, not the sa

manufacturing

It is effective when applied judiciousl

limited aims, complexity, and scope

This is in spite of Jaikumars paper P

Industrial Manufacturing, HBR Nov

December 1986, which claimed that Umade less flexible use of FMS than Ja

firms, and that this was bad for US m


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Rigid Part Mating

Goals of this class

understand the phases of a typical part m

determine the basic scaling laws

understand basic physics of part mating

geometries

relate forces and motions arising from g

compare logic branching and direct erro

mating strategies

rigid part mating 9/13/2004 Daniel E Whitney 2000

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Main Phases of a Part Matin

contactforce

Approach Chamfer One-point Two-point Crossing Contact Contact


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E/2

E/2V

Required Bandwidth for Chamf

10E/V0.5E/V

0.5EE

2 2 ) si

= T=

/ V; T / = 40

lateral motion

Fourier coefficient = 2 T / (n n (2 n

Period = 2 20E/V

T = 20 E = E / 2 V;

= V /10 Ef = V / 20 E

If V = 10 in/s and E = 0.05", f = 10 Hz

If 5th harmonic must be adhered to, bandwid


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9/13/2004 Daniel E Whitney 2000

rigid part mating

Trapezoidal Wave Harmo


Source:

Figure 9-7in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Desiand Role in Product Development. New York, NY: Oxford University Press, 200

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Conclusions

Gross motions can be (must be) done

arms that necessarily will move slowl

No robot arm with practical reach can

motion error removal adjustments at 5

Fine motions can be fast if they are doarms, and must be fast to absorb typic

economical speeds

Big tasks with big parts will take a lon

compared to small tasks with small pa What we see: small parts cycle times a

big parts cycle times are ~ 60s.

rigid part mating


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Essentials of Part Mating Th

Fine Motions

Quasi-static assumption

Geometry of pegs and holes

Applied forces

Normal reaction forces and friction r

Entry geometry limits

Wedging conditions

Jamming conditions Alternate strategies for accomplishin


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The Basic Idea

In gross motions, it pays to pre-plan t

errors

In fine motion, it does not pay to try t

errors So the principle is to anticipate errors

out how to make assembly happen an

This requires us to understand three f

Geometry

Compliance

Friction

rigid part mating


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Dimensioning Practic


Source:



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Geometry Definition

r

R

W

D

d

o

o

c = (D-d)/D

Insertion Direction


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Insertion History


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Insertion History


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Insertion History


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Insertion History


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Insertion History


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Insertion History


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Life Cycle of a Part Ma

Image removed for copyright reasons.Source:




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Forces and Moments - Two

Contact Case


Source:



Al

fo

in


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Forces Applied During Two-po

Kx

K

Lg

When L >> 0K

xg

Kx

K

Kx

Big

Big


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Making Lg Small is Go

How to do it?

Active Robot Force Feedback

Costly

Slow

Some way that acts by itself

It was invented almost 30 years ago

Called Remote Center Compliance

Reduces assembly force

Avoids one of two main failure mode


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Wedging: Compressive Fricti

Prevent Insertion Regardless o

Force

==== tan

d

D

l

f1

- 1

l

2f

==== tan- 1

- d

l

Wedging can happen if > c/ Wedging can when two-point contact occurs enough or if t

deep enough rigid part mating 9/13/2004

Daniel E Whitney 2000

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Whats a Friction Con

FN

= tan-1

F

FFriction cone

FTFN

Sliding will occur if FT > FNFT /FN = tan So, sliding will occur if tan > and F will lie on the boundary

of the cone

If F is in

then slid

because

and F c


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Jamming: Insertion Force Dir

Wrong Way - Cant Overcom

COMPONENT NORMAL TO PEG AXIS COMP

OMPONENT

INSERTIONFORCE

ARALLEL TOCOMPONENT

EG AXISPARALLEL TO

FRICTION PEG AXISCORRESP.

TO NORMALCOMPONENT

REACTION

TO NORMAL

COMPONENT

Component ofInsertion force

Along insertion direction

Not big enough:

Peg Is Jammed

ComInse

Alo

Is b

Pegrigid part mating 9/13/2004

Daniel E Whitney 2000

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Jamming Examples

COMPONENT NORMAL TO PEG AXIS COMP

OMPONENT

INSERTIONFORCE

Fx

M

ARALLEL TOCOMPONENT

EG AXISPARALLEL TO

FRICTION PEG AXISCORRESP.

TO NORMALCOMPONENT

REACTION

TO NORMAL

COMPONENT

Fz

Fx/Fz is big.

M/rFz is big.


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Experimental Data -2


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Experimental Data - 3


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RCC Response to External

(d) RCC UNDERLATERAL LOAD

(e) RCC UNDERANGULAR LOAD


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(d) RCC UNDERLATERAL LOAD


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9/13/2004 Daniel E Whitne 2000y

r

rigid part mating

Angular Error =

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9/13/2004 Daniel E Whitne 2000

rigid part matingy

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Commercial Remote Center Co


Source:




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rigid part mating

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Objectives of Assembly Mo

Provide a computer environment that pdown design of assemblies with a persi

that captures the assembly as an assemb

Should link to geometry creation (CAD

generated)

Should permit specification of Key Cha

constraints on location, datums and loc

variation analysis for KCs using the ass

Should permit assembly planning, vend

ramp-up, and production support

Assy Models 9/16/2004 Daniel E Whitney

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Top-down and Bottom-up D

Top-down defines an assembly in this major customer deliverables

chains of delivery through possible parts

main part mates and necessary features

detailed part geometry

Bottom-up defines

the same things but in the reverse order

requires having some idea of final assem

Top-down used to be the only way be

CAD seems to encourage bottom-up


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Sketch of Top-Down Assemb

9/16/2004

Tooling

Constraints

Variation

Sequences

Responsibility

1

2

3

45

67

Pylon

EngineInlet

Door

PKC

PKC

Datum Flow Chain

Assy Models Daniel E Whitney

DFC

Assembly

FeaturizedDFC

Location

Dimensional

Control

Constraint (6 DoF)

Selected concept

Architecture

Integration risk

Key dimensions

Relating KCs to Chains

top-down assy process

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Goals of this Class

Review basic math that relates adjace

frames

Model assemblies as chains of frames

Attach these frames to mating featur

Introduce feature based design for ass


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Basic Math

Uses 4x4 matrices to relate adjacent f

Permits chaining together of parts

same math is used to describe robots

The matrix contains a rotational part a

translational part

The matrix is designed to translate fir

rotate so that rotation does not change

new frame

This matrix is a subset of a more gene

projection matrix that includes perspe


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HANDLEHAMMER

BASE

CARRIER

ANVIL

ANVIL

CARRIER

STAPLES

RIVET

RIVET

"X" DIRECTION

SIDE VIEW

TOP VIEW

HANDLE

HAMMER

PIN

CRIMPER

CRIMPER

STAPLE

PIN

AXIS

"A"A

XIS

"B"

"Y"DIRECTION

"Z"DIRECTION

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Stapler Frames and KC


Source:

Figure 3-5in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Desiand Role in Product Development. New York, NY: Oxford University Press, 200


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Frames and Chains

By following the arrows, you can trav

frame to frame

On the previous slide, the anvil was c

origin part, and the anvil-pin joint on chosen as the location of the origin fr

All arrows go out from the origin fram

You can travel from one end of a KC

by moving from frame to frame alongsometimes in arrow direction and som

reverseAssy Models 9/16/2004 Daniel E Whitney

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Basic Translation and Rot


Source:



Translate first, then rotate


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Basic 4x4 Transform

R p RT 1T = =

0

T

1 0

r

r11 r12 r13

21 r22 r23

T = r31 r32 r330 0 0

pxpy

p

z

1

All the info

location (po

orientation)matrix


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Basic Translation Matr

No rot

1 0 0

0 1 0

0 0 1

!

#

#

#

#

x

y

$

&

&

&

&%

trans(x,y,z)=

z

0 0 0 1"

This and the three basic rotation ma

are matlab .m files on MIT Servert


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9/16/2004

T01 locates frame 1 in frame 0 coor



Composite Transform

T02 = T01 T12

R01 p01 R12p12 =T02 =0

T0

T

T1 1

R01R12 R01p12+p0100

T1

Assy Models

T01T12T02

Daniel E Whitney

locates frame 1 in frame 0 coord



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Assy Models Daniel E Whitney9/16/2004

Transform Order is Impo

TB= T T

B. T

BA= T

B

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Nominal Mating of Parts

Imagesremoved for copyright reasons.

Source:




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Example

>>

TAB

Coordinate Frames MATL



Source:


Mechanical Assemblies: Their Design, Manufacture,and Role in Product Development.New York, NY:Oxford University Press, 2004. ISBN: 0195157826.

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Front, Top, and Side Vi

Top

Other Front Side

BottomAssy Models 9/16/2004 Daniel E Whitney

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Another Example

>> TAC = TAB roty

!0 0 1

0 1 0

1 0 0

0 0 0"

#####

=TAC


Source:

Figure 3-22in [Whitney 2004] Whitney, D. E.Mechanical Assemblies: Their Design, Manufacture,and Role in Product Development.New York, NY:Oxford University Press, 2004. ISBN: 0195157826.

function degtorad =% Converts degreedegtorad=theta*pi/


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Example Feature on Pa

>> TA

=TAD


Source:



and Role in Product Development. New York, NY:

Oxford University Press, 2004. ISBN: 0195157826.


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Feature on Second Pa

>>

TEF



Source:

Figure 3-24in [Whitney 2004] Whitney, D. E.Mechanical Assemblies: Their Design, Manufacture,and Role in Product Development.New York, NY: Oxford University Press, 2004. ISBN: 0195157826.

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Assembling These Par

>> TDE = rotz (d

1 0

0 1

!

"

##

###

=

TDE


Source: 0 0

0 0Figure 3-25in [Whitney 2004] Whitney, D. E.


>> TAF = TADTDEand Role in Product Development.

!0 0

0 1 0

1New York, NY: Oxford University Press, 2004. ISBN: 0195157826.

"

###

##

=TAF 1 0

0 0

0

0

4x4_examples copy


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Varied Part Location Due to To

TT

T

AF

FB'

AB'

A

B'

The varied location of Part B can be calcu

from the nominal location of Part A. Thiscan be chained to Part C, etc., including er

Part B. It uses the same math as the nomin

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Equations for Connective M

Nominal


Source:

Figure 3-19in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: The

and Role in Product Development. New York, NY: Oxford University Press

Varied


Source:

Figure 3-20in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: T

and Role in Product Development. New York, NY: Oxford University Pre


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A Hierarchy of Assembly M

Bill of materials - lists the parts in no partic

Structured BOM - aka drawing tree - group

assembly

Liaison graph - (Bourjault) parts are dots, j

Ordered liaison graph - the lines have arrow

Attributed liaison graph - the lines haveconstraint or feature information

Ordered-attributed liaison graph (Datum Fl


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Assembly Types Classified Te


Source:

Figure 3-1in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Designand Role in Product Development. New York, NY: Oxford University Press, 2004.


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Assembly Types Classified b

Diagram Form

Hub and spokes

Loop

Network

Stack


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Inside a Car Engine


Source:

Figure 5-2in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Design



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Feature-based Design

Seeks to rise above geometry and cap First efforts in machined features

slots

pockets

holes

Features look different depending on

made

drafted walls if cast pocket

pockets if cut

Feature recognition may be needed


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Assembly FeaturesEach feature has nominal geometry and a ref

coordinate frame expressed as a 4x4 matrix.

a variety of other attributes as needed for its t

Images removed for copyright reasons.Featu

Source:

Figure 3-12 in [Whitney 2004] Whitney, D. E.

Mechanical Assemblies: Their Design, Manufacture,may no

and Role in Product Development.

.

New York, NY: Oxford University Press, 2004.ISBN: 0195157826. Story: Fe

Head scr


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A Really Bad Exampl


Source:




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A Better Way, Based on Feat

Frames

O x

yx

y

x

y

1

2

R

p01

p12


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What The Different Mode

World coordinate model is good for d

pictures of the nominal arrangement;

interferences based on errors in the no

cant help you find out why they happ

Chained model is good for capturing

information and design intent, and can

effects of variation from the nominal;

necessarily find interferences becausethings to be assembled; can help yo

why things dont fit


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Information in Assembly M What parts mate to what parts

What features define the mates and wher

the parts

What interfaces must be controlled, plus

of describing them

Constraints and rule-checking about assembly in the small

about assembly intent in terms of features

about assembly in the large, including altern

It is a completely abstract and general mconnectivity

Geometry is an attribute of the partsAssy Models 9/16/2004 Daniel E Whitney

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Example Assembly Data MDECLARED ASSEMBLY FEATURE

ON PART_____ (text)

TYPE NAME_____SPECIFIC NAME__

LOCATION ON PART _____ (4x4)

LOCAL ESCAPE DIRECTION____

(DEFAULT: Z AXIS)

TOLERANCES

GEOMETRY_____

PARAMETERS________

TOLERANCES_____

OPTIONAL: FEATURES IT CAN MAT

CONSTRAINTS

MATED TO FEATURE___ ON PART _

CASE... (other parts in other circumsta


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Seeker Head


Source:




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Seeker Liaison Diagra


Source:

Figure 3-29in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Desigand Role in Product Development. New York, NY: Oxford University Press, 2004.


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PART PART NAME FEATURE FEATURE NAME FEATURE CLA

A 1

2

1

2

3

45

6

C 1

2

3

4

D 1

2

3

E 1

2

F 1

2

3

G 1

2

H 1

2

3

I 1

2

J 1

2

3

1

2

K

B OUTER GIMBAL

BASE

INNER GIMBAL

OUTER BEARING

RETAININGSCREW

OUTER BEARING

RETAININGSCREW

INNER BEARING

RETAININGSCREW

RETAININGSCREW

INNER BEARING

BEARING BORE

BEARING BORE

BEARING BORE

BEARING BORERET. SCREW HOLE

TRUNNION

BORE

OUTER DIAMETER

INNER RACE FACE

THREAD

HEAD

BORE

THREAD

HEAD

BORE

THREAD

HEAD

BORE

THREAD

HEAD

RET. SCREW HOLE

RET. SCREW HOLE

RET. SCREW HOLE

OUTER DIAMETER

INNER RACE FACE

OUTER DIAMETER

INNER RACE FACE

OUTER DIAMETER

INNER RACE FACE

(CHAMFERED) B

(CHAMFERED) B

(CHAMFERED) B

(CHAMFERED) B

(CHAMFERED) P

(CHAMFERED) P

(CHAMFERED) P

(CHAMFERED) P

THREADED BOR

THREADED BOR

THREADED BOR

THREADED BOR

(CHAMFERED) B

(CHAMFERED) B

(CHAMFERED) B

(CHAMFERED) B

(CHAMFERED) P

(CHAMFERED) P

(CHAMFERED) P

(CHAMFERED) P

PLANE

THREADED PIN

PLANE

PLANE

THREADED PIN

PLANE

PLANE

THREADED PIN

PLANE

PLANE

THREADED PIN

PLANE

TRUNNION

TRUNNION

TRUNNION

3

4

TRUNNION BORE

TRUNNION BORE

BORE

BORE

7

8

TRUNNION BORE

TRUNNION BORE

BORE

BORE

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ource:

Figure 3-30in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Design, Manufac

nd Role in Product Development. New York, NY: Oxford University Press, 2004. ISBN: 0195


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Feature-based Design V

Made at Draper in 1990

Illustrates a bottom-up approach

First demo of integrated design of ass

hooked to a CAD systemparts designed with mating features

parts joined by connecting the features

liaison diagram constructed automatical

assembly data model passed to CAE rouassembly sequence, assembly system de

economic analysis


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Kinematic Constraint in As

Topics

Assembly as zero-stress location

AKA Exact Constraint, Proper C

Kinematic Design

AKA 3-2-1 assembly

Assembly features as carriers of constra

operationalizing the coordinate frames

Non-zero-stress assemblies

Mathematical analysis of constraint

Class 6-7 Constraint 9/21/2004 Daniel E Whitney

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Assembly = Constrain

Assembly = removal of dof = applica

constraint

As constraint is applied, degrees of fr

taken away so that a part gets to wher

supposed to be.

When parts are where they are suppos

KCs can be delivered, assuming no v This is called the nominal design


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Parts Locate Each Other to Delive

the Customer Level

BODY TOHINGE FLAP1: 6 DOF

HINGE FLAP 1 TO

HINGE FLAP 2: 5 DOF

HINGE FLAP 2 TODOOR: 6 DOF

CRAFTMANS

DOOR

CAR BODY

KC=


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Definitions of Assembl

Whitehead: An instrument can be rechain of related parts any mechani

function is directly dependent on the

with which the component parts achi

required relationships.The Design and Use oAccurate Mechanism, by Thomas North Whitehead, 1934

Whitney: An assembly is a chain of

frames on parts designed to achieve c

dimensional relationships called KeyCharacteristics between some of the

between features on those parts. Des

Research in Engineering Design, (1999) 11:229-253.Class 6-7 Constraint 9/21/2004 Daniel E Whitney

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The Three Principles of S

Geometric compatibility

Force and moment balance

Stress-strain-temperature relations

We assume rigid parts, so the 3rdprindoes not apply to our work


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Properly Constrained and

constrained Assemblie

Assemblies that function by geometri

and force equilibrium alone are called

statically determinate

properly constrained

kinematic or semi-kinematic ~ 3-2 You just put them together

Assemblies that require stress analysi

statically indeterminate

over-constrained

You cant just put them together

Constraint is a property of the nominClass 6-7 Constraint 9/21/2004 Daniel E Whitney

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Constraint is Accomplished by

in Contact

The contact permits

some dof to movewith respect to

each other and

prevents motion of

other dof.

The black ones

can move.

The red ones cant.

Z

X

Y

D

sp

m

d


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Class 6-7 Constraint Daniel E Whitney9/21/2004

Degrees of Freedom

An objects location in space is comp

specified when three translations (X, three rotations ( ) are specified

How many DOFs are constrained?

cube on table (x-y plane)

cube at floor-wall interface

cube at floor-two walls interface

ball on table

ball at floor-wall interface

round peg in blind round hole Think about the constrained ones

x

. x

. ,. Y

,. Z

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Constraint - 1

Proper constraint provides a single valubodys 6 degrees of freedom

This is done by establishing surface co

surfaces on another part or parts

If less than 6 dof have definite values, under-constrained

If an attempt is made to provide 2 or m

a dof, then the body is over-constraine

bodies have only 6 dof Any extra needed dof must be obtained

the object


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Example of Proper and Over C

Two pins in holes One pin in hole,

Y Y

XThis is over-constrained

in the X direction

This is properX


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Constraint - 2

Proper constraint permits an assembl

unambiguous chains of delivery of K

Two pins in holes

O

2875 fall 2004

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