1. EML 4550: Engineering Design Methods
Design for Manufacturing
(Brief Introduction)
Ulrich and Eppinger: Chapter 9
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2. 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
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3. DFMA DFM Overview 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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4. DFM Flowchart Proposed Design Acceptable 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
Good
Enough? Y
Acceptable Design
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5. Estimating Manufacturing Costs
Raw Materials
Software demo from BDI
Purchased Parts
Labor
Equipment
Manufacturing
System
Finished Product
Tooling
Information
Energy
Waste
Supplies
Services
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6. Elements of the Manufacturing Cost
Components
Overhead
Assembly
Standard
Support
Labor
Indirect
Allocation
Custom
Equipment
And Tooling
Raw Material
Processing
Tooling
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7. 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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8. 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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9. The Bill of Materials
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10. 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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11. 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.)
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12. 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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13. 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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14. 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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15. 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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16. 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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17. Reducing Assembly Cost
Maximize ease of assembly
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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18. Reducing Support Cost Minimize Systemic Complexity Error Proofing
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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19. 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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