1. Design for Manufacturing
Chapter 11
EIN 6392, Product Design
Summer 2012

2. Product Design and Development Karl T. Ulrich and Steven D
Product Design and Development Karl T. Ulrich and Steven D. Eppinger 4nd edition, Irwin McGraw-Hill, 2000.
Chapter Table of Contents
1. Introduction
2. Development Processes and Organizations
3. Product Planning
4. Identifying Customer Needs
5. Product Specifications
6. Concept Generation
7. Concept Selection
8. Concept Testing
9. Product Architecture
10. Industrial Design
11. Design for Manufacturing
12. Prototyping
13. Product Development Economics
14. Managing Projects
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3. Product Development Process
Planning
Concept
Development
System-Level
Design
Detail
Design
Testing and
Refinement
Production
Ramp-Up
How can we emphasize manufacturing issues
throughout the development process?
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4. Outline DFX concept DFM objectives DFM method Mfg. cost estimation
DFM impacts
DFM examples
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5. Understanding Manufacturing Costs
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6. Definition
Design for manufacturing (DFM) is a development practice which emphasizes manufacturing issues throughout the product development process.
Successful DFM results in lower production cost without sacrificing product quality.
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7. Three Methods to Implement DFM
Organization:
Organize cross-functional teams
Design Rules:
Exercise best practices specialized by the firm
CAD Tools:
Apply CAD systems such as the Boothroyd-Dewhurst DFA software
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8. Introduction DFM is part of DFX
DFM often requires a cross-function team
DFM is performed through the development process
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9. Major DFM objectives Reduce component costs Reduce assembly cost
Reduce production support costs
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10. The DFM Process (5 steps)
Estimate the mfg. costs
Reduce the costs of components
Reduce the costs of assembly
Reduce the costs of supporting production
Consider the impact of DFM decisions on other factors.
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11. 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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12. Reduce the costs of components
Identify process constraints and cost drivers
Redesign components to eliminate processing steps
Choose the appropriate economic scale for the part process
Standardize components and their processes
Adhere the black-box component
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13. 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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14. Reduce the costs of supporting production
Minimize systematic complexity (such as plastic injection modeling for one step of making a complex product)
Error proofing (anticipate possible failure modes in the production system and take appropriate corrective actions early in the development process)
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15. Considering impacts Development time Development cost Product quality
External factors such as
component reuse and
life cycle costs
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16. Design for Manufacturing Example: 1993 GM 3800cc V6 Engine Design
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17. DFM example Exhibit 11-15 on Page 230 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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18. Cost Appendices Materials costs Component mfg. costs Assembly costs
Exhibit on page 235
Component mfg. costs
Exhibits 11-18/21 on pages
Assembly costs
Page 242 for common products
Page 243 for part handling and insertion times
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24. 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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25. Design for X – Design principles
Standardization strategy
use standard parts
standardize design features
minimize the number of part types
minimize number of total parts.
standardize on types and length of linear materials and code them.
consider pre-finished material (pre-painted, pre-plated, embossed, anodized).
combine parts and functions into a single part.
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26. 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 from the 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 most likely to fail last.
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27. Design for X – Design principles
Assembly strategies 2
make sure options can be added easily
ensure the product's life can be extended with future upgrades.
use sub-assemblies, especially if processes are different from the main assembly.
purchase sub-assemblies which are assembled and tested.
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28. 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 that auto-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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29. 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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30. 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 electrical adjustments unless required for customer use.
minimize electrical cables; plug electrical sub-assemblies directly together.
minimize the number of types of cable.
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31. 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 to handle.
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32. 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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33. 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 consistent with quality goals.
tests should give adequate diagnostics to minimize repair time.
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34. 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 replace with disposable replacements
provide inexpensive spare parts in the product.
ensure availability of spare parts.
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35. 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 damage prevention.
protect parts with fuses and overloads
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36. 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 and easy to disconnect.
make sure repair, service or maintenance tasks pose no safety hazards.
make sure sub-assembly orientation is obvious or clearly marked.
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37. 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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38. Design for X – Design principles
Axomatic design
Axiom 1
In good design, the independence of functional requirements is maintained.
Axiom 2
Among the designs that satisfy axiom 1, the best design is the one that has the minimum information content.
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39. Design for X – Design principles
Axiomatic design- corollaries
Decouple or separate parts of a solution if functional requirements are coupled 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 proposed solution.
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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40. 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 the assembly.
Estimate the handling and assembly costs for each part using the appropriate assembly process - manual, robotic, or high-speed automatic.
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41. 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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42. Design for Assembly Rules Example 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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43. Design for Assembly http://www.dfma.com Key ideas of DFA:
Minimize parts count
Maximize the ease of handling parts
Maximize the ease of inserting parts
Benefits of DFA
Lower labor costs
Other indirect benefits
Popular software developed by Boothroyd and Dewhurst.
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44. To Compute Assembly Time
Handling Time
+ Insertion Time
Assembly Time
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45. 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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46. Videocassette DFM Exercise
2 billion worldwide annual volume
7 major producers of 1/2” cassette shells
JVC licenses the VHS standard
dimensions, interfaces, light path, etc
VHS cassette shells cost ~$0.25 each
What is a $0.01 cost reduction worth?
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47. DFM Strategy is Contingent
Corporate
Strategy
Product
Strategy
Production
Strategy
DFM
Strategy
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