lecture #8 - singhosesinghose.marc.gatech.edu/courses/me2110 summer09... · lecture #8. me 2110:...

ME 2110: Creative Decisions and Design1

Design for ManufacturingDfM

Lecture #8


Phases of Design

1) Customer Requirements

2) Specification Development

3) Conceptual Design

4) Detail Design

5) Specification of Production

6) Manufacture

7) Recycle

ME 2110: Creative Decisions and Design

Design for X (DFX)

• Design for

Manufacture

X is a Variable Name


Design for X (DFX)

• Design for Assembly


Design for X (DFX)

• Design for

Environment

• Design for Disassembly


• Design for Maintenance

• Design for Safety

Design for X (DFX)


Design for Assembly

• Methods consists of a design review by– Design and development personnel

– Production personnel

• The technique imposes– Discipline

– Objectiveness


Aspects of Design for Assembly

• DFA is applicable to

– Products consisting of 20 -200 parts

– Mainly for mechanical parts (not electronic circuits)

– Dimensions lie between those of watches and cars

• No specialized knowledge of production means is needed

• Requires 1-2 days to perform for a product

• Often 30% improvement in the assembly cost

• Can be performed in the various stages in the design process

and repeated


Design for Assembly (Criteria)

• Execution of assembly operations– Storing & Retrieval

– Handling

• Identifying, Picking-Up, Moving

– Positioning

• Orientating, Aligning

– Joining

– Adjusting

– Securing

– Inspecting



• Standardization of assembly operations

• Use of existing assembly equipment and tools

• Use of standard assembly tools



• Number of operations in overall assembly

• Favorable sequence (preassembly, parallel

assembly)



• Possibility of automation

• Freedom from possible assembly errors

• Avoidance of damage to components



• Avoidance of special training of the

assembly staff

• Maintenance of safe working conditions

• Observance of ergonomic standards


Questions Raised During DFA

• Is it possible to eliminate part of the process?– Can the product be assembled if the part is integrated with

another part?

• What is the cost to deliver a part to the

assembly with correct spatial orientation and

position?

• What does it cost to carry out the assembly of

the part?


Design for Assembly Guidelines

• During product operation, does the part move relative to other parts?– Consider only gross motions

– Small motions can be accomplished by deformation (such as elastic hinges).

• Must the part be of a different material than other parts?


Pneumatic Piston Sub-Assembly

1 - Screw (2) (steel)

2 - Cover (steel)

3 - Spring (steel)

4 - Piston stop (nylon)

5 - Piston (aluminum)

6 - Main block (plastic)


Design for Assembly Worksheet

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TM CM NMdesign efficiency

NM

TM= =

3 *

Name of Assembly

TM = Total manual assembly time

CM = Total cost of manual assembly

NM = Theoretical minimum number of parts


Pneumatic Piston Sub-Assembly

1 - Screw (2) (steel)

2 - Cover (steel)

3 - Spring (steel)

4 - Piston stop (nylon)




Worksheet for Pneumatic Piston

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1.5

2.5

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7.84

1

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42.25 16.90 4

TM CM NM

Main Block

Piston

Piston Stop

Spring

Cover

Screw

0.29design efficiencyNM

TM= =

3 *

Name of Assembly

Pneumatic Piston





Redesigned Pneumatic Piston

1 - Snap on cover

and stop (plastic)

2 - Spring (steel)




Worksheet for Redesigned Piston

1

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1.5

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3.30

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1.34

1.40

1

1

1

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13.29 5.32 4

TM CM NM

Main Block

Piston

Spring

Cover & Snap

0.90design efficiencyNM

TM= =

3 *

Name of Assembly

Pneumatic Piston

(re-design)





Design for Automated Assembly (Concepts)

• Layered design

– Clamshell base

– Sequential assembly

– Uni-directional

• Self-alignment

– Chamfer/countersink

– Posts/locating stops

• Combine detail parts

– Screws & washers

– Plastic moldings

– Castings

• Symmetry

• Direct drive systems

– Helical or gear vs.

Belt/pulley

• Common fasteners

– Minimize screws

– Snap fasteners

• Minimize springs

– Molded

– Compression coil

– Extensive coil

• Minimize cables

– Integrated packaging

– Solid connectors


Example of Layered Assembly

Snaps

Snaps


Compliance and Assembly

Avoid Better Best

No ChamfersBottom Part

Chamfered

Top Part

Chamfered

Both Parts

Chamfered


Self Alignment of Parts

This part could be oriented in any direction

These parts can be oriented only one way

Hole to accept

swaged part

Hole to accept

notched part

“D” shaped hole


Nesting of Parts

This part could be

placed in any orientation

and not be secured

This part has a “nest” to

orient and help it secure


Nonfunctional External Feature for Orientation

This slot would

be hard to detect

Pin to help orient slot

Chamfer to help orient slot


Symmetry

Orientation Required

Preferred


Tangling

These parts can tangle easily

The same parts redesigned, will not tangle


Tangling (continued)

Parts that interconnect

will not feed

Springs with open

loops will tangle

Springs with closed

loops will not tangle

A fillet will keep the parts

from interconnecting


Methods to Avoid Jams (1 of 2)

This results in

shingling

Base causes leading

edge to be lower than

trailing edge

Direction of Flow

A nonfunctional corner can

eliminate this problem


Methods to Avoid Jams (2 of 2)

Rounded corners

can prevent jams

Mating surfaces with sharp

edges can cause jams

A groove can prevent

jams by centering the part


Substitutes for Fasteners

Avoid designs that require fasteners

Design parts that snap together


Joining Moving Parts without Fasteners

C-Clip

Chamfered

SurfaceSnaps


Fasteners

Preferred: Have flat vertical sides for vacuum pickup

Avoid

Socket Head Fillister Head Hex Head

Round Head Flat Head

Round Side Slant Side


Cables and Connectors

Avoid:

Components that are connected

with cables to circuit board

Preferred:

Components that are plugged

on a slave circuit board

Example of a slave circuit board


Cables and Connectors

Example of a secured cable

If the use of a cable cannot be avoided.

Have the cable plugged into a dummy

connector to locate the cable end.

Then a robot can locate the

connector and plug it in.


Motion and Design

Avoid: Three motions required for insertion

Slot

Snaps

Preferred: Only one motion required


Design for ME2110 Assembly

• Keep it Simple

• Easy Access to All

Parts (So they can

be replaced)

• Easy to Set Triggers

• Start Assembly Now

Starting

Areas

Loose Balls

Backboard

Ball SupplyDefensivePlayers

Ball Storage

lecture #8 - singhosesinghose.marc.gatech.edu/courses/me2110 summer09... · lecture #8. me 2110:...

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