Plastic Design - Sumsung-Design Guide for Assembly of Injection Molded Plastic Parts
Class16DesignforAssembly Plastic Design
Transcript of Class16DesignforAssembly Plastic Design
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 1/32
© Daniel E Whitney
DFA
• Goals of this class: – Place DFA in context
– Learn basic principles of Design for Assembly
– Understand background and history – Understand its strong and weak points
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 2/32
© Daniel E Whitney
“The Multiplier” According to Ford and GM
or: Why Is DFM/DFA Important?
• For every product part, there are about 1000
manufacturing equipment parts*
• Or, for every toleranced dimension or feature on a
product part, there are about 1000 toleranceddimensions or features on manufacturing
equipment
• Such “equipment” includes fixtures, transporters,dies, clamps, robots, machine tool elements, etc*Note: Ford’s estimate is 1000, GM’s is 1800. Both are informal estimates.
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 3/32
© Daniel E Whitney
A Few Quotes
• Just because you can make something doesn’t
mean you can manufacture it.
• It’s very hard to make cheap [low cost] stuff - you
get buried by your mistakes.
• I don’t understand why it won’t assemble. It passed inspection.
• Word came down that we couldn’t use screws. So
we used snap fits. Then word came down that ithad to pass a drop test. So we dropped it and it
fell apart...
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 4/32
© Daniel E Whitney
Goals of DFM/DFA
• Historically, conventionally – reduce costs, simplify processes
– improve awareness of manufacturing issues during design
• More broadly (a goal of this course) – align fabrication and assembly methods to larger goals
• ability to automate, systematize, raise quality, be flexible
• access to assembly-driven business methods like delayedcommitment
• innovative designs, outsourcing (Siemens intake manifold)
• Inevitably pushes DFM/DFA earlier into the productdevelopment process where it blends with architecture(see AITL Basic Issues and Product Architecture classes)
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 5/32
© Daniel E Whitney
Complete Outsourced Subassembly
AIR
CLEANER
FUEL INJECTORS
INTAKE AIR
TEMPERATURE
SENSOR
INTAKE MANIFOLD
THROTTLE BODY
FUEL PRESSURE
REGULATOR
INTEGRATED
FUEL RAIL
AIR FLOW
SENSOR
IDLE SPEED
CONTROL
Courtesy Siemens VDOAutomotive. Used with permission.
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 6/32
© Daniel E Whitney
The Assembly from Heaven*
• Can be assembled one-handed by a blind personwearing a boxing glove
• Is stable and self-aligning• Tolerances are loose and forgiving
• Few fasteners
• Few tools and fixtures
• Parts presented in the right orientation
• Parts asymmetric for easy feeding• Parts easy to grasp and insert
*Dr Peter Will, ISI
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 7/32
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 8/32
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 9/32
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 10/32
© Daniel E Whitney
Characteristics of Traditional DFA
• Uses an easy to understand metrics-driven approach (metrics
story about demurrage)
• Uses a relative cost and time metric
• DFA in the small simplifies each assembly step
– single parts
– manual assembly
– small parts
– uses many context-free metrics to assess difficulty levels of
feeding and handling
• DFA in the large emphasizes part count reduction – It is essentially another force in product architecture
– Advanced plastics make part count reduction more attractive
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 11/32
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 12/32
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 13/32
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 14/32
© Daniel E Whitney
Part Count TradeoffsONE PART PER
µ FUNCTIONMANY
SIMPLEPARTS
LOTS OFINTERFACESIN ASSEMBLY
LOTS OFLOGISTICS,FAB ACTIVITY,
& ASSY ACTIVITY
EXTRA WEIGHT,EXTRA FAULT
OPPORTUNITIES
EXTRA CHANCESFOR ERRORS
QUALITY ISCREATEDDURING
ASSEMBLY
FLEXIBILITYIS POSSIBLE
DURINGASSEMBLY
EXTRA"SUPPORT"
COST
PARTS CONSOLIDATION:FEWER PARTS AND LESS
FASTENING
MORE FUNCTIONSHARING
FEWER BUTMORE COMPLEX
PARTS
MORE ACTIVITYDURING FAB,LESS DURING
ASSEMBLY
QUALITY CREATEDDURING FAB
PARTS COSTMORE
PARTS TAKELONGER TODESIGN ANDPROTOTYPE
FEWER OPPORTUNITIESFOR ON-LINE FLEXIBILITY
PART COUNT TRADEOFFS
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 15/32
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 16/32
© Daniel E Whitney
DFM Strategies
Example Products:
High performance computers
Telecommunications equipment
DFM Strategy:
Avoid long lead time tooling
Use standard components
Minimize production risk
Example Products:
Machine tools
Electrical distribution equipment
DFM Strategy:
Avoid expensive tooling
Use standard components
Other issues likely to dominate
Example Products:
Blank videocassettes
Circuit breakers
DFM Strategy:
Use traditional DFM
Combine and integrate parts
Consider automatic assembly
Example Products:
Notebook computers, Toys
DFM Strategy:
Minimize complexity of mostcomplex part
For complex parts, use processes
with fast tool fab
Apply traditional DFM to less
time-critical parts
Low Lifetime Production Volume
D e v e l o p m e n
t T i m e C r i t i c a l
D e v e
l o p m e n t T i m e
N o t C r i t i c a l
Source: Ulrich, Sartorius, Pearson, Jakiela, “DFM Decision-making”, Mgt Sci, v 39 no 4, Apr 1993.
High Lifetime Production Volume
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 17/32
© Daniel E Whitney
Questions of Scope
• When can DFA be applied?• When should DFA be applied?
• What information is needed before DFA can be
applied?
• What should the designers’ priorities be?
• Can/should DFA be separated from “the rest” of product design?
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 18/32
© Daniel E Whitney
The Pump Redesign
• See Redford & Chal, pp 118-119• What are the differences between the old and new
designs?
– from the POV of product function – from the POV of assembly
• What are we looking at in this example?
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 19/32
© Daniel E Whitney
R e d f or d - C h a l P
um pR
e d e s i gn
Ball
Ball
Valve
Valve
Courtesy of Alan Redford. Used with permission.
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 20/32
© Daniel E Whitney
The Pneumatic Piston Redesign*
• Was the original function completely understood?• Was it preserved in the redesign?
*Product Design for Assembly by Boothroyd and Dewhurst, workbook 1991
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 21/32
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 22/32
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 23/32
© Daniel E Whitney
DFA at Sony
• Applied to products like Handicams• “Our designers take assembly into account early.”
• Method:
– concept designs are sketched in exploded views
– each concept is subjected to DFA analysis and scored
– concept selection criteria include DFA score
• A Sony engineer made a complete exploded view
drawing of a Polaroid camera in 20 minutes!
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 24/32
© Daniel E Whitney
D
F A a t
D e n s o
L
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 25/32
© Daniel E Whitney
How to Do DFA
• 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 mating times
• Label theoretically necessary parts, excluding all fasteners• Calculate
• This ranges from 5% for kludges to 30% for good designs
assembly efficiency =3* # of theoretically needed parts
total predicted assembly time
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 26/32
© Daniel E Whitney
Handling Times
S =α + β
No handling difficulties Part nests or tangles
Thickness > 2mm <2mm Thickness > 2mm <2mmSize>15mm 6mm<size
<15mmSize>6mm Size>15mm 6mm<size
<15mmSize>6mm
Symmetry
( )
0 1 2 3 4 5
S < 360° 0 1.13 1.43 1.69 1.84 2.17 2.45
360°<S<540° 1 1.5 1.8 2.06 2.25 2.57 3540°<S<720° 2 1.8 2.1 2.36 2.57 2.9 3.18S=720° 3 1.95 2.25 2.51 2.73 3.06 3.34
α ≤180° α = 360°
0 1 2
4 4.1 4.5 5.6
For parts needing one hand only
For parts needing two hands(Courtesy of Boothroyd Dewhurst, Inc. © 1999.) Used with permission.
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 27/32
© Daniel E Whitney
Insertion Times
(Courtesy of Boothroyd Dewhurst, Inc. © 1999.)
Secured by separate operation or part No hold ing dow nrequ ired
Ho lding dow nrequ ried
Secured r igh t aw ay by snap fi t
Easy toalign
No t easyto align
Easy toalign
No t easyto align
Easy toalign
No t easyto align
0 1 2 3 4 5
No access
or visiondifficulties
0 1.5 3.0 2.6 5.2 1.8 3.3
Obstructedaccess or restrictedvision
1 3.7 5.2 4.8 7.4 4.0 5.5
Obstructed
access andrestrictedvision
2 5.9 7.4 7.0 9.6 7.7 7.7
Part inserted but not secured immediately, or secured by snap fit
Easy to align No t eas to align0 1
No access or vision difficulties
3 3.6 5.3
Restricted visiononly
4 6.3 8.0
Obstructedaccess only
5 9.0 10.7
Part inserted and secured immediately by power screwdriver. Note: add 2.9 s to get power tool.
Used with permission.
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 28/32
© Daniel E Whitney
A Few Conceptual Questions
• What’s a “base part?” – remember the alternator - the nut is the “base” in the
only assembly sequence family that achieves assemblywithout reorientation
– different types of “product structure” exist (Arch. class)
• What do you mean “difficult?” – for manual assembly, Boothroyd has some time-baseddata (originally derived from grad students)
• Why avoid screws? – 25 years ago’s reasons may not apply any more
– see Blonder video
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 29/32
© Daniel E Whitney
Manual vs Automatic Assembly DFA
• What’s easy for a person
– reorienting the assembly
– quickly eyeballing the part (story about bad filament)• What’s easy for a machine
– picking up little parts
– using tools that are like tweezers
• Part jams occur most often in feeder tracks
– Denso: perfect parts don’t jam!
• A different balance between gross motion and fine
motion times
• Different ways of “inspecting”
i hi A bl li bili l i
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 30/32
© Daniel E Whitney
Hitachi Assembly Reliability Evaluation
Method
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 31/32
© Daniel E Whitney
Design for Recycling and Reuse
PRODUCT ORSUBASSEMBLY
SINGLE
PART
MULTIPLE
PARTS
REUSE,
RECYCLE,
OR DUMP
SINGLE
MATERIAL
MULTIPLE
MATERIALS
SOME PARTS
CAN BE REUSED
NO PARTS
CAN BE
REUSED
CHOOSE DISASSEMBLY
METHOD THAT
PRESERVES
REUSABLE PARTS
CHOOSE DISASSEMBLY
METHOD THAT SEPARATE
PARTS INTO GROUPS
OF LIKE MATERIALS
NO PARTS
CAN BE
REUSED
RECYCLE
OR DUMP
A
TO A TO A
7/28/2019 Class16DesignforAssembly Plastic Design
http://slidepdf.com/reader/full/class16designforassembly-plastic-design 32/32
© Daniel E Whitney
Greg Blonder Video (17 min of 1:45)
• Talk given at Bell Labs Jan 16, 1990
• Has been analyzing precision consumer products
for about 5 years• Takes about a day to analyze each one
• Takes apart and analyzes a $100 Canon camera
• Classifies ~ 400 parts including 60 screws (!)• Tells what it means to get high assembly yield
• Tries to explain it to a high level executive
• Discusses shutter and flash subassemblies
• He later became a VP of Lucent