Design%20for%20Manufacturing

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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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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

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Product Development Process
Concept Development
System-Level Design
Detail Design
Testing and Refinement
Production Ramp-Up
Planning
How can we emphasize manufacturing issues
throughout the development process?
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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 ExampleGM 3.8-liter V6
Engine
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Understanding Manufacturing Costs
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Definition

• Design for manufacturing (DFM) is a development
  practice emphasizing 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 development process

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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 assembly
4. Reduce the costs of supporting production
5. Consider the impact of DFM decisions on 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 the
  part 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 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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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 Example1993 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

• 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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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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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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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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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
  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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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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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
  consistent with quality goals.
• tests should give adequate diagnostics to
  minimize repair time.

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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 replace with 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 damage
  prevention.
• 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 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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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 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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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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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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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 handling parts
• Maximize the ease of inserting parts
• Benefits of DFA
• Lower labor costs
• Other indirect benefits
• Popular software developed by Boothroyd 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
Corporate Strategy
Product Strategy
Production Strategy
DFM Strategy
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