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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
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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
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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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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];
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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
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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
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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.
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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
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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
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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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Image removed for copyright reasons.
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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Image removed for copyright reasons.
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
Image removed for copyright reasons.
Source:
Figure 1-5in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Desi
and Role in Product Development. New York, NY: Oxford University Press, 200
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The Delivery Path for Each St
Image removed for copyright reasons.
Source:
Figure 1-6in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Desi
and Role in Product Development. New York, NY: Oxford University Press, 200
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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
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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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Image removed for copyright reasons.
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
Image removed for copyright reasons.
Source:
Figure 2-10in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their De
and Role in Product Development. New York, NY: Oxford University Press, 200
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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
Image removed for copyright reasons.
Source:
Figure 2-12in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their De
and Role in Product Development. New York, NY: Oxford University Press, 200
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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
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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
Image removed for copyright reasons.
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
Image removed for copyright reasons.
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:
Figure 1-7in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Desi
and Role in Product Development. New York, NY: Oxford University Press, 200
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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
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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.
Images removed for copyright reasons.
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Class 2 Assy motions Daniel E Whitney 1997-20049/7/2004
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:
Figure 9-3in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Desi
and Role in Product Development. New York, NY: Oxford University Press, 200
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Class 2 Assy motions Daniel E Whitney 1997-20049/7/2004
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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Class 2 Assy motions Daniel E Whitney 1997-20049/7/2004
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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Class 2 Assy motions Daniel E Whitney 1997-20049/7/2004
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
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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
Image removed for copyright reasons.
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
Image removed for copyright reasons.
Source:
Figure 15-30in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Dand Role in Product Development. New York, NY: Oxford University Press, 200
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
DFA03.ppt 11/2/2004 Daniel E Whitney
Image removed for copyright reasons.
Source:
Figure 15-11in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their D
and Role in Product Development. New York, NY: Oxford University Press, 200
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Home Hot Water System Fam
11/2/2004DFA03.ppt Daniel E WhitneyPoschman
Image removed for copyright reasons.
Source:
Figure 15-14in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Des
and Role in Product Development. New York, NY: Oxford University Press, 2004.
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Melt-Core Technology for Water H
PoschmanDFA03.ppt 11/2/2004 Daniel E Whitney
Image removed for copyright reasons.
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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Image removed for copyright reasons.
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
Image removed for copyright reasons.
Source:
Figure 14-15in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Des
and Role in Product Development. New York, NY: Oxford University Press, 2004.
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Sony Exploded View
Image removed for copyright reasons.
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
Image removed for copyright reasons.
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
Image removed for copyright reasons.
Source:
Figure 15-18in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their D
and Role in Product Development. New York, NY: Oxford University Press, 200
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
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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
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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
11/24/2004 FMS Daniel E Whitney 1997-2004
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
11/24/2004 FMS Daniel E Whitney 1997-2004
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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
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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
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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
Image removed for copyright reasons.
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
Image removed for copyright reasons.
Source:
Figure 10-16in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Dand Role in Product Development. New York, NY: Oxford University Press, 200
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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:
Figure 10-12in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their D
and Role in Product Development. New York, NY: Oxford University Press, 200
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Forces and Moments - Two
Contact Case
Images removed for copyright reasons.
Source:
Figure 10-18in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Des
and Role in Product Development. New York, NY: Oxford University Press, 2004
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
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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
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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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(e) RCC UNDERANGULAR LOAD
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(e) RCC UNDERANGULAR 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
Images removed for copyright reasons.
Source:
Figure 9-9in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Desi
and Role in Product Development. New York, NY: Oxford University Press, 200
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9/13/2004 Daniel E Whitney 2000
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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
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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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Assy Models 9/16/2004 Daniel E Whitney
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
Images removed for copyright reasons.
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
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Basic Translation and Rot
Image removed for copyright reasons.
Source:
Figure 3-6in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their Desi
and Role in Product Development. New York, NY: Oxford University Press, 200
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
T12 locates frame 2 in frame 1 coor
T02 locates frame 2 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
locates frame 2 in frame 1 coord
locates frame 2 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:
Figure 3-17in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their D
and Role in Product Development. New York, NY: Oxford University Press, 2
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Example
>>
TAB
Coordinate Frames MATL
Assy Models 9/16/2004 Daniel E Whitney
Image removed for copyright reasons.
Source:
Figure 3-21in [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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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
Image removed for copyright reasons.
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
Images removed for copyright reasons.
Source:
Figure 3-23in [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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Feature on Second Pa
>>
TEF
Assy Models 9/16/2004 Daniel E Whitney
mage removed for copyright reasons.
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
Image removed for copyright reasons.
Source: 0 0
0 0Figure 3-25in [Whitney 2004] Whitney, D. E.
Mechanical Assemblies: Their Design, Manufacture,
>> 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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Assy Models Daniel E Whitney9/16/2004
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
Image removed for copyright reasons.
Source:
Figure 3-19in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: The
and Role in Product Development. New York, NY: Oxford University Press
Varied
Image removed for copyright reasons.
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
Images removed for copyright reasons.
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
Images removed for copyright reasons.
Source:
Figure 5-2in [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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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
Image removed for copyright reasons.
Source:
Figure 3-43in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their De
and Role in Product Development. New York, NY: Oxford University Press, 200
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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
Image removed for copyright reasons.
Source:
Figure 3-28in [Whitney 2004] Whitney, D. E. Mechanical Assemblies: Their De
and Role in Product Development. New York, NY: Oxford University Press, 200
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Seeker Liaison Diagra
Image removed for copyright reasons.
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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Assy Models Daniel E Whitney9/16/2004
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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mage removed for copyright reasons.
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
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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
Class 6-7 Constraint 9/21/2004 Daniel E Whitney
7/25/2019 2875 fall 2004
291/835
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
Class 6-7 Constraint 9/21/2004 Daniel E Whitney
7/25/2019 2875 fall 2004
292/835
Constraint - 2
Proper constraint permits an assembl
unambiguous chains of delivery of K
Two pins in holes
O