Integrated Product and Process Design

Design for Manufacture and Assembly

ME 475/476

Some slides in this presentation have been provided courtesy of Emeritus Professor, Dr. Perry Carter, School of Technology at Brigham Young University

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Schedule

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Assignments

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Integrated Product and Process Design

What Would you Like to Learn About Design for Manufacture & Assembly (DFM/DFA)?

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Important Considerations in Product Design

• Functionality

• Safety

• Appearance

• Weight

• Maintainability

• Recyclability

• Reliability

• Manufacturability

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What is the Cost of a Product?

Bulb Boss Costs

     

Cost Remaining:

Selling Price:   $5.00      

Retail Store Gross Profit:   $2.50   $2.50  

Distribution:   $0.75   $1.75  

Overhead of Manufacturing:   $0.50   $1.25  

Development Cost:   $0.10   $1.15  

Warrantee Cost:   $0.05   $1.10  

Advertising:   $0.40   $0.70  

Packaging:   $0.20   $0.50  

Assembly:   $0.10   $0.40  

Materials:   $0.35   $0.05  

Manufacturing Profit:   $0.05   $0.00  

Reduced Production Costs

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Four Activities of Manufacturing

• Changing the shape of materials• Changing the properties of materials• Assembling materials (as component parts)• Creating or organizing the tools, machines

and systems to make the first three mf’g. activities happen

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We can Make Anything, Right?

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Engineering is a People Profession

Integrated Product and Process Design

“Nowhere in a company is the need for coordination more acute than between the people who are

responsible for product design and those responsible for

manufacturing.”

Harvard Business Review

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A Very Helpful Book

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The Cost of Design Changes…

Time of Change

• During Concept selection and early stages of product & process design

• During design testing• During process testing• During test production• During final production

Relative Cost

• $1

• $10• $100• $1,000• $10,000

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Improving Manufacturability

• The single most important principle to improving manufacturability is to want to

• The second most significant principle to improving manufacturability is to do it in the early stages of design

• A third important principle is to seek to learn from others

• A significant additional guideline for improving manufacturability is to strive for Simplicity!• Reduce the number of parts• Reduce tolerances• Use standard parts whenever possible• Reduce number of fasteners & adjustments

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Manufacturability (Cont’d)

• Seek to learn about the capabilities and limitations of manufacturing processes, equipment, and materials before you design the product.

• Consider preferred vs. nonpreferred processes and materials

• Consider manufacturing cost targets for the different parts of the your product

DFMA (Design for Manufacturability and Assembly) is a structured method for comparing alternative product designs with respect to manufacturability

What is DFMA?

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These comparisons are usually based on cost or time…

What are the benefits of DFMA?

• Improved communication and decision making

• Earlier and fewer design changes• Improved Quality• Reduced production costs• Shorter time to market• Increased market share and

profits…

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One Example…

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Three principle parts of the Porsche manifold

Two A’s and one B make up one C

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Designing for the Process

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Mf’g. Processes Reference Guide

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• Breaks 125 mfg. processes into three categories:

- Knowledge - Application

- Development • Defines, explains each process• Encourages integration of

design and manufacturing to yield better designed products

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What Mfg. Process Should I Use?

Preferred Methods Nonpreferred Methods           

Castings or plastic   Completely Machined

Near net-shaped casting   Casting    

Screw Machine   Lathe Turning  

Milling     Jig bore    

Turning     Milling    

Standard Materials   Nonstandard Materials  

Tolerances > +/- 0.005   Tolerance < +/- 0.001

6061 Aluminum   Steels, stainless steels

303 Stainless Steel   Other types of stainless steels

Thermoplastics   Thermosets  

Hardness < or = 41 Rc   Harness > 41 Rc  

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Tight Tolerances Cost Money!

Ken Foresterhas prepared a nice handout to get you started…

Designing for the Process: Example

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Ford Air filter cover, initial release

Designing for the Process

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Designing for the Process

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Ford air filter cover after redesign

Design for Assembly

• What does DFA accomplish?

• What are the basic assembly tasks?

• What are the cost drivers associated with these assembly tasks?

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- Reduce cost!

What are basic assembly tasks?

• Handling• Grasping, separating from bulk, orienting…

• Insertion• Aligning, engaging, inspection

• Fastening• Clamping, threading,

plastic deformation, adhesive, etc.

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Some Tips…• Design so the Assembly Process can be

completed in a layered fashion – preferably from above

• Consider easy part handling• Design mating parts that are easy to insert

and align• Avoid part designs that will cause tangling

with identical parts• Make parts symmetrical to aid in automatic

orientation• If symmetry can’t be achieved, exaggerate

the asymmetrical features…

Effect of Part Size on Handling Time

Part Handling

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Part Tangling

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Spring Tangling

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Insertion

Effect of Chamfers35

Insertion

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Example of Obstructed Access

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Alignment

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Assembly Time Example

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3. Fasteners

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Fastener Costs…• Number; type

• High assembly time

• Quality may be poor

• Higher quality is expensive

• Prone to assembly errors

• Cost of inventory

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Other Methods of Fastening

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What is the Cost of Inventory?

• Documentation

• Inventory space

• Inventory cost of h’wd.

• Shipping

• Incoming inspection

• Vendor relations

• Vendor qualification

• Part certification

• Failure replacement

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Lucent Technologies reports it costs$15,000/year to maintain one electronic part certification and $150,000 for a new part

Product Reliability Improvement

Product reliability, that is mean time between failures (MTBF), is inversely tied to part count!

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Proof-of Concept vs. Prototype

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Watch for Over-Constraint in Design

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Avoid Adjustments…

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What constitutes a theoretically necessary part?

Identify parts that don’t meet theoretical criteria for being separate parts…and eliminate them if possible

• Motion

• Material

• Access

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Motion

1.  During the normal operation of the product, does this part move relative to all the other parts already assembled?

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Material

2.   Must this part be of a different material than all the other parts already assembled?

(Reasons should be based on fundamental, properties of the material such as electrical conductivity, thermal conductivity, vibration damping, hardness, modulus, etc.)

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Access

3.   Must this part be separate from all other assembled parts to allow the assembly of other theoretically necessary parts.

This could involve parts that must pass through an opening requiring a door, cover, lid etc. that must be removable to allow assembly of other internal parts.

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DFMA Examples

• Flowserve valve

• GM Intake Manifold

• Jeep Throttle Linkage

• XEROX door lock

• Automotive “A-arm”

• Coat Rack

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Standardized Parts…

Interchangeable flanges

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What Material Should I choose?

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Aluminum design:

Sand casting process $3.53

Machining $1.70

Assembly _____

Total processing $5.23

Nylon design:

Injection Molding $2.66

Assembly _____

Manifold Cost Comparison

Cost Comparison

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Redesign Benefits

• 45% unit cost savings

• 66% weight savings

• Simplified assembly & service

• Improved emissions performance due to EGR mounting

• Improved engine performance due to reduced intake air temperature

• Reduced shipping costs due to weight reduction

• Increased part standardization

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British Motors Example

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Avoid Unnecessary Part Numbers

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Modern one-piece A- arm

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1964 Jeep Throttle Pedal

• 38 parts

• 23 fasteners

• 228 seconds assembly time

• 1 theoretically required part

• 1.3% assembly efficiency

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XEROX Door Lock

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XEROX Door Lock

Original Design

• 62 parts

• Total time = 6.9 min.

• Assembly cost = $2.76

• Parts cost = $9.80

• Min No. parts = 10

• Efficiency = 4.8%

Redesign

• 17 parts

• Total time = 1.48 min.

• Assembly cost = $0.59

• Parts cost = $7.44

• Min No. parts = 10

• Efficiency = 22.5%

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Coat Rack

Design for assembly analysis by MFG 572 student team

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16 parts, including 9 fasteners

One single part requiring several forming operations and one weld.

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Summary

• Observe what others have done, good and bad, in the way things are made

• Avoid the “us vs. them” paradigm• Seek input from experts, be eager to learn• Design your parts considering the mf’g. process• If you can, reduce the number of parts • Seek to eliminate fasteners and adjustments• Keep in mind that it’s the obvious that is most

often overlooked in DFMA• Most importantly—consider manufacturability

early in the design process… 66

Integrated Product and Process Design

Thank You!

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