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Design for Manufacturing. Teaching materials to accompany: Product Design and Development Chapter 13 Karl T. Ulrich and Steven D. Eppinger 5th Edition, Irwin McGraw-Hill, 2012. Product Design and Development Karl T. Ulrich and Steven D. Eppinger 5th edition, Irwin McGraw-Hill, 2012.

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design for manufacturing
Design for Manufacturing

Teaching materials to accompany:

Product Design and DevelopmentChapter 13

Karl T. Ulrich and Steven D. Eppinger5th Edition, Irwin McGraw-Hill, 2012.

Product Design and DevelopmentKarl T. Ulrich and Steven D. Eppinger5th edition, Irwin McGraw-Hill, 2012.

Chapter Table of Contents:

  • Introduction
  • Development Processes and Organizations
  • Opportunity Identification
  • Product Planning
  • Identifying Customer Needs
  • Product Specifications
  • Concept Generation
  • Concept Selection
  • Concept Testing
  • Product Architecture
  • Industrial Design
  • Design for Environment
  • Design for Manufacturing
  • Prototyping
  • Robust Design
  • Patents and Intellectual Property
  • Product Development Economics
  • Managing Projects
product development process
Product Development Process







Testing and





How can we emphasize manufacturing issues

throughout the development process?

  • DFX concept
  • DFM objectives
  • DFM method
  • Mfg. cost estimation
  • DFM impacts
  • DFM examples
  • 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.
  • DFM is part of DFX
  • DFM often requires a cross-function team
  • DFM is performed through the development process
major dfm objectives
Major DFM objectives
  • Reduce component costs
  • Reduce assembly cost
  • Reduce production support costs
the dfm process 5 steps
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.
estimate mfg costs
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
reduce the costs of components
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
reduce the costs of assembly
Reduce the costs of assembly
  • Integrate parts (using the Boothroyd method)
  • Maximize ease of assembly
  • Consider customer assembly (do-it-yourself) technology driven products
reduce the costs of supporting production
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)
considering impacts
Considering impacts
  • Development time
  • Development cost
  • Product quality
  • External factors such as
    • component reuse and
    • life cycle costs
dfm example
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.
cost appendices
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.
design for x design principles
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.
design for x design principles1
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.
design for x design principles2
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.
design for x design principles3
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.
design for x design principles4
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).
design for x design principles5
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.
design for x design principles6
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.
design for x design principles7
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.
design for x design principles8
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.
design for x design principles9
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.
design for x design principles10
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.
design for x design principles11
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
design for x design principles12
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.
design for x design principles13
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.
design for x design principles14
Design for X – Design principles
  • Axomatic Design by Nam Suh
    • 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.
design for x design principles15
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.
design for x design principles16
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.
design for x design principles17
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?
design for assembly rules example set of dfa guidelines from a computer manufacturer
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.

design for assembly
Design for Assembly
  • 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.
to compute assembly time
To Compute Assembly Time

Handling Time

+ Insertion Time

Assembly Time

method for part integration
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.
three methods to implement dfm
Three Methods to Implement DFM

1. Organization: Cross-Functional Teams

2. Design Rules: Specialized by Firm

3. CAD Tools: Boothroyd-Dewhurst Software

dfm strategy is contingent
DFM Strategy is Contingent