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Design for Manufacturing
Teaching materials to accompany:
Product Design and DevelopmentChapter 13
Karl T. Ulrich and Steven D. Eppinger5th Edition, Irwin McGraw-Hill, 2012.
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Produc t Design and DevelopmentKarl T. Ulrich and Steven D. Eppinger
5th edition, Irwin McGraw-Hill, 2012.
Chapter Table of Contents:1. Introduction2. Development Processes and Organizations3. Opportunity Identification4. Product Planning5. Identifying Customer Needs6. Product Specifications
7. Concept Generation8. Concept Selection9. Concept Testing10. Product Architecture11. Industrial Design12. Design for Environment
13. Design for Manufacturing14. Prototyping
15. Robust Design16. Patents and Intellectual Property17. Product Development Economics18. Managing Projects
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Outline
DFX concept
DFM objectives
DFM method
Mfg. cost estimation
DFM impacts DFM examples
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Design for Manufacturing Example:
GM 3.8-liter V6 Engine
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Understanding Manufacturing Costs
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Definition
Design for manufacturing (DFM) is a development
practiceemphasizing manufacturing issues
throughout the product development process.
Successful DFM results in lower production cost
without sacrificing product quality.
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Introduction
DFM is part of DFX
DFM often requires a cross-function team
DFM is performed through the developmentprocess
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Major DFM objectives
Reduce component costs
Reduce assembly cost
Reduce production support costs
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The DFM Process (5 steps)1) Estimate the mfg. costs
2) Reduce the costs of components
3) Reduce the costs of assembly4) Reduce the costs of supporting
production
5) Consider the impact of DFM decisionson other factors.
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Estimate mfg. costs Cost categories Component vs. assembly vs. overhead
Fixed vs. variable
Material vs. labor
Estimate costs for standard parts Compare to similar part in use
Get a quote from vendors
Estimate costs of custom made parts
Consider material costs, labor costs, and tooling costs
Depend on the production volume as well
Estimate costs of assembly
Summing up all assembly operations (time by rate)
Estimate the overhead costs
A % of the cost drives
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Reduce the costs of components Identify process constraints and cost drivers
Redesign components to eliminate processing
steps
Choose the appropriate economic scale for thepart process
Standardize components and their processes
Adhere the black-box component
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Reduce the costs of assembly Integrate parts (using the Boothroyd
method)
Maximize ease of assembly
Consider customer assembly (do-it-
yourself) technology driven products
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Reduce the costs of
supporting production Minimize systematic complexity (such as
plastic injection modeling for one step ofmaking a complex product)
Error proofing (anticipate possible failure
modes in the production system and take
appropriate corrective actions early in thedevelopment process)
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Considering impacts Development time
Development cost
Product quality
External factors such as
component reuse and
life cycle costs
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Design for Manufacturing Example:
1993 GM 3800cc V6 Engine Design
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DFM example
Exhibit 13-15 on Page 274
Unit cost saving of 45%
Mass saving of 66% (33 Kg.)
Simplified assembly and service procedures.
Improved emissions performance
Improved engine performance
Reduce shipping costs (due to lighter components)
Increased standardization across vehicle programs.
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Cost Appendices
Materials costs Exhibit 13-17 on page 279
Component mfg. costs Exhibits 13/18-21 on pages 280-283
Assembly costs Page 286 for common products
Page 287 for part handling and insertion times on
Ex. 13-23
Cost structures for firms on Ex 13-24.
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Design for X
Design principles
Part shape strategies: adhere to specific process design guidelines
if part symmetry is not possible, make parts very
asymmetrical design "paired" parts instead of right and left hand parts.
design parts with symmetry.
use chamfers and tapers to help parts engage.
provide registration and fixturing locations. avoid overuse of tolerances.
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Design for X
Design principles
Assembly strategies 1 design product so that the subsequent parts can be added to
a foundation part.
design foundation part so that it has features that allow it to
be quickly and accurately positioned.
Design product so parts are assembled from above or fromthe minimum number of directions.
provide unobstructed access for parts and tools
make parts independently replaceable.
order assembly so the most reliable goes in first; the mostlikely to fail last.
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Design for X
Design principles Fastening strategies 1 use the minimum number of total fasteners
use fewer large fasteners rather than many small fasteners
use the minimum number of types of fasteners
make sure screws should have the correct geometry so thatauto-feed screwdrivers can be used.
design screw assembly for downward motion
minimize use of separate nuts (use threaded holes). consider captive fasteners when applicable (including
captive nuts if threaded holes are not available).
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Design for X
Design principles Fastening strategies 2
avoid separate washers and lockwashers (make it be
captivated on the bolt or nut so it can still spin with respect
to the fastener)
use self-tapping screws when applicable.
eliminate fasteners by combining parts.
minimize use of fasteners with snap-together features.
consider fasteners that push or snap on.
specify proper tolerances for press fits.
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Design for X
Design principles Assembly motion strategies
fastened parts are located before fastener is applied.
assembly motions are simple.
Assembly motions can be done with one hand or robot. assembly motions should not require skill or judgment.
products should not need any mechanical or electricaladjustments unless required for customer use.
minimize electrical cables; plug electrical sub-assembliesdirectly together.
minimize the number of types of cable.
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Design for X
Design principles Automation handling strategies 1
design and select parts that can be oriented by automation
design parts to easily maintain orientation
use parts that will not tangle when handled in bulk. use parts what will not shingle when fed end to end (avoid
disks).
use parts that not adhere to each other or the track.
specify tolerances tight enough for automatic handling.
avoid flexible parts which are hard for automation tohandle.
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Design for X
Design principles Automation handling strategies 2
make sure parts can be presented to automation.
make sure parts can be gripped by automation.parts are within machine gripper span.
parts are within automation load capacity.
parting lines, spruces, gating or any flash do not
interfere with gripping.
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Design for X
Design principles Quality and test strategies product can be tested to ensure desired quality
sub-assemblies are structured to allow sub-assembly
testing testing can be performed by standard test instruments
test instruments have adequate access.
minimize the test effort spent on product testing consistentwith quality goals.
tests should give adequate diagnostics to minimize repairtime.
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Design for X
Design principles DF Maintenance strategies 1 provide ability for tests to diagnose problems
make sure the most likely repair tasks are easy to perform.
ensure repair tasks use the fewest tools.
use quick disconnect features
ensure that failure or wear prone parts are easy to replacewith disposable replacements
provide inexpensive spare parts in the product. ensure availability of spare parts.
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Design for X
Design principles Maintenance strategies 2 use modular design to allow replacement of modules.
ensure modules can be tested, diagnosed, and adjusted
while in the product. sensitive adjustment should be protested from accidental
change.
the product should be protected from repair damage.
provide part removal aids for speed and damageprevention.
protect parts with fuses and overloads
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Design for X
Design principles Maintenance strategies 3
protect parts with fuses and overloads
ensure any sub-assembly can be accessed through one door
or panel. access over which are not removable should be self-
supporting in the open position.
connections to sub-assemblies should be accessible andeasy to disconnect.
make sure repair, service or maintenance tasks pose nosafety hazards.
make sure sub-assembly orientation is obvious or clearlymarked.
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Design for X
Design principles Maintenance strategies 4 make sure sub-assembly orientation is obvious or clearly marked.
provide means to locate sub-assembly before fastening.
design products for minimum maintenance.
design self-correction capabilities into products
design products with self-test capability.
design products with test ports
design in counters and timers to aid preventative maintenance.
specify key measurements for preventative maintenance programs
include warning devices to indicate failures.
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Design for X
Design principles Axomatic Design by Nam Suh
Axiom 1
In good design, the independence of functionalrequirements is maintained.
Axiom 2
Among the designs that satisfy axiom 1, the best
design is the one that has the minimuminformation content.
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Design for X
Design principles Axiomatic design- corollaries
Decouple or separate parts of a solution if functional requirements arecoupled or become coupled in the design of products and processes.
Integrate functional requirements into a single physical part or
solution if they can be independently satisfied in the proposedsolution.
Integrate functional requirements and constraints.
Use standardized or interchangeable parts whenever possible.
Make use of symmetry to reduce the information content.
Conserve materials and energy.
A part should be a continuum if energy conduction is important.
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Design for X
Design principles DFA Method: Boothroyd and Dewhurst Apply a set of criteria to each part to
determine whether, theoretically, it should be
separated from all the other parts in theassembly.
Estimate the handling and assembly costs foreach part using the appropriate assembly
process - manual, robotic, or high-speedautomatic.
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Design for X
Design principles Three criteria
Is there a need for relative motion?
Is there a need for different materials Is there a need for maintenance?
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Design for Assembly RulesExample set of DFA guidelines
from a computer manufacturer.1. Minimize parts count.
2. Encourage modular assembly.
3. Stack assemblies.
4. Eliminate adjustments.5. Eliminate cables.
6. Use self-fastening parts.
7. Use self-locating parts.
8. Eliminate reorientation.
9. Facilitate parts handling.
10. Specify standard parts.
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Design for Assembly
Key ideas of DFA:
Minimize parts count
Maximize the ease of handlingparts
Maximize the ease of insertingparts
Benefits of DFA
Lower labor costs
Other indirect benefits
Popular software developed byBoothroyd and Dewhurst.
http://www.dfma.com
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To Compute Assembly Time
Handling Time
+ Insertion Time
Assembly Time
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Method for Part Integration
Ask of each part in a candidate design:
1. Does the part need to move relative to the rest of
the device?
2. Does it need to be of a different material because
of fundamental physical properties?
3. Does it need to be separated from the rest of the
device to allow for assembly, access, or repair?
If not, combine the part with another part in the
device.
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Three Methods to Implement DFM
1.Organization: Cross-Functional Teams
2.Design Rules: Specialized by Firm
3.CAD Tools: Boothroyd-Dewhurst Software
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DFM Strategy is Contingent
CorporateStrategy
ProductionStrategy
ProductStrategy
DFM
Strategy
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Other Images
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