EML 4550: Engineering Design Methods
Design for Manufacturing
(Brief Introduction)
Ulrich and Eppinger: Chapter 9
EML4550 2007
1
Definitions
 “Design for…”: reliability, availability, serviceability,
environment, cost…. “DFX”
 Design for Manufacturing (DFM)
 Very important aspect of the design/development cycle
 Integrated throughout design process
 Interdisciplinary and Multi-departmental (design, manufacturing, and
production engineers, materials selection, accounting, purchasing,
etc.)
 Ensure that the product being designed can be
manufactured at minimum cost while maintaining
repeatability and quality
EML4550
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DFM Overview
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Estimate the manufacturing costs
Reduce the cost of components (DFM)
Reduce the cost of assembly (DFA)
Reduce the cost of supporting production
Consider the impact of DFM on other aspects of the product
DFMA
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DFM Flowchart
Proposed Design
Estimate the
Manufacturing Cost
Reduce the
Cost of Components
Reduce the
Cost of Assembly
Reduce the Cost
of Production Support
Consider the Impact
Of DFM on other Factors
Recalculate the
Manufacturing Cost
N
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Good
Enough?
Y
Acceptable Design
Estimating Manufacturing Costs
Raw Materials
Software demo from BDI
Purchased Parts
Labor
Equipment
Tooling
Manufacturing
System
Information
Energy
Supplies
Services
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Waste
Finished Product
Elements of the Manufacturing Cost
Components
Assembly
Standard
Labor
Custom
Equipment
And Tooling
Raw Material
Processing
Tooling
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Overhead
Support
Indirect
Allocation
Elements of the Manufacturing Cost
 Components
 Standard or custom parts; raw materials, processing, or tooling;
purchased or in-house
 Assembly
 Equipment and tooling plus labor needed to manufacture product
 Overhead
 Support
 Purchasing, QA, shipping & receiving, maintenance, etc.
 Indirect
 Administration, security, legal, etc.
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Elements of the Manufacturing Cost
 Fixed (independent of the number of units produced)
 Special tooling
 Tool set-up
 Variable (proportional to the number of units produced)
 Raw materials
 Purchased parts
 Assembly labor
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The Bill of Materials
Component
System 1
Subsystem 1.1
Subsystem 1.2
Subsystem 1.3
Sub-subsystem 1.3.1
Sub-subsystem 1.3.2
Subsystem 1.4
Subsystem 1.5
System 2
…
All amounts in K$
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Materials
Assembly Variable Cost
0.1
0.2
1.2
0.8
0.55
0.25
Tooling Tooling Lifetime
Fixed Cost
250
500
Total
0.5
0.1
0.1
0.1
0.1
0.1
Per Unit Total:
0.5
0.2
0.3
2.1
0.65
0.35
4.1
Reducing Component Cost
 Understand Process Constraints and Cost Drivers
Take into account production cost early in the design phase
Do not specify tight tolerances if not needed
Do not ‘over-specify’ part qualities (surface finish, etc.)
Focus on the part functionality and design accordingly
Bear in mind limitations of production equipment (in terms of limits,
rates, and complexity)
 Sometimes the manufacturing limitations can easily be quantified
and are repeatable, but oftentimes the ‘experience’ of the those
involved need to be invoked. Work closely with Production.
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Reducing Component Cost
 Redesign Components to Eliminate Processing Steps
 Consider eliminating steps that may not contribute to part
functionality (paint, surface finish, etc.)
 Try to design parts that can be manufactured in ‘one-step’ (molding,
casting, extrusion, etc.)
 If more steps are needed try to use ‘standard’ procedures (cutting to
length, drilling hole, simple machining, etc.)
EML4550
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Reducing Component Cost
 Choose the Appropriate Economic Scale for the Part Process
 Use ‘economies of scale’. Part cost decreases as production volume
increases
 Determine ‘breakeven’ production volumes to decide among different
processes (fixed vs. variable costs)
Process A
Process B
$/unit
Breakeven Point
Number of parts manufactured
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Reducing Component Cost
 Standardize Component and Processes
 Economies of scale applied at the component level
 Better quality at lower cost if part is purchased from a major supplier
(that has already specialized in the production of that component)
 Increase supplier platform (availability and price)
 Standardize across product platforms (same part for more than one
product)
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Reducing Component Cost
 Adhere to “Black Box” Component Procurement
 Japanese technique to specify only the functionality of the part but
not the part
 Leave supplier with freedom to produce best “black box”
 In essence ‘subcontracting’ and avoiding a large portion of the
design effort
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Reducing Assembly Cost
 Keeping Score
 Maintain an ongoing estimate of assembly cost and be mindful of
‘assembly efficiency’
 Manufacturing Efficiency Index = 3 seconds x (minimum # of
parts)/(estimated assembly time)
 ‘3 seconds’ is the minimum required to handle and position a part
 Minimum number of parts:
 Does the part move relative to the rest of the assembly?
 Does the part need to be made of different material than the rest of the
assembly?
 Does the part need to be removed for service or replacement?
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Reducing Assembly Cost
 Integrate Parts
 If a part does not qualify as such according to the criteria given
above, then it is a candidate to be integrated to another part
 Eliminate assembly
 Less expensive to fabricate
 Clear definition of function
 In some instances it is best to dis-integrate parts to reduce
manufacturing costs (e.g., shape considerations to utilize different
manufacturing methods)
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Reducing Assembly Cost
 Maximize ease of assembly
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Insert part from top of assembly
Self-aligning parts
Part is indifferent to orientation
Assembly is possible with one hand
No tools required
Assembly requires a single linear motion
Part is secured upon insertion
 Consider Customer Assembly
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Reducing Support Cost
 Minimize Systemic Complexity
 Create quantifiable way to keep track of ‘complexity’ and strive to
reduce it
 Error Proofing
 Anticipate error modes or possible failures to be encountered during
manufacturing (equivalent to FMECA in Design for Reliability)
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Consider Impact of DFM
 Impact on Development Time
 Economic model to ensure that by saving $ on manufacturing cost
we do not increase development time
 Impact on Development Cost
 Same as above but for development cost
 Impact on Product Quality
 Reduce manufacturing cost but not at expense of quality
 Impact on External Factors
 Possible ramifications to other projects within the company:
component reuse,
 Possible ramifications to customers and society: life-cycle cost (save
on manufacturing and ‘transfer’ cost to consumer), environmental
issues (toxics, disposal, etc.)
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