ME2110 Concurrent Design - DfXsinghose.marc.gatech.edu/courses/me2110 Spring13/lectures/Concu… ·...

ME2110

Concurrent Design - DfX

Design for X (DFX)

1. Design for Manufacture

3

Design for X (DFX)

2. Design for Assembly

4

Design for X (DFX)

• Design for Environment

• Design for Disassembly

5

• Design for Maintenance

Design for X (DFX)

• Design for Safety

6

Design for Assembly

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

– Production personnel

• The technique imposes – Discipline

– Objectiveness

7

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

8

Design for Assembly (Criteria)

• Execution of assembly operations

– Storing

– Handling

• Identifying, Picking-Up, Moving

– Positioning

• Orientating, Aligning

– Joining

– Adjusting

– Securing

– Inspecting

9


• Standardization of assembly operations

• Use of existing assembly equipment and tools

• Use of standard assembly tools

10


• Number of operations in overall assembly

• Favorable sequence (preassembly, parallel

assembly)

11


• Possibility of automation

• Freedom from possible assembly errors

• Avoidance of damage to components

12


• Avoidance of special

training of the assembly

staff

• Maintenance of safe

working conditions

• Observance of

ergonomic standards

13

Questions for DFA Analysis

• 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?

14

Questions for DFA Analysis

• 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?

16

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)

17

Design for Assembly Worksheet

1

Part

I.D

. N

um

ber

2 3 4 5 6 7 8 9 N

um

ber

of

tim

es t

he

op

era

tio

n is c

arr

ied

ou

t co

nsecu

tively

Tw

o-d

igit

man

ual

han

dli

ng

co

de

Man

ual

han

dli

ng

tim

e p

er

part

Tw

o-m

an

ual

insert

ion

co

de

Man

ual

insert

ion

tim

e p

er

part

Op

era

tio

n t

ime (

sec)

(2)*

[(4)

+ (

6)]

Op

era

tio

n c

ost

(¢)

0.4

* (

7)

Fig

ure

s f

or

theo

reti

cal

min

imu

m

part

s E

sti

mati

on

TM CM NM d e s i g n e f f i c i e n c y

N M

T M = = 3 *

Name of Assembly

TM = Total manual assembly time

CM = Total cost of manual assembly

NM = Theoretical minimum number of parts

18

Pneumatic Piston Sub-Assembly

1 - Screw (2) (steel)

2 - Cover (steel)

3 - Spring (steel)

4 - Piston stop (nylon)



19

Worksheet for Pneumatic Piston

1

Part

I.D

. N

um

ber

2 3 4 5 6 7 8 9 N

um

ber

of

tim

es t

he

op

era

tio

n is c

arr

ied

ou

t co

nsecu

tively

Tw

o-d

igit

man

ual

han

dli

ng

co

de

Man

ual

han

dli

ng

tim

e p

er

part

Tw

o-d

igit

man

ual

insert

ion

co

de

Man

ual

insert

ion

tim

e p

er

part

Op

era

tio

n t

ime (

sec)

(2)*

[(4)

+ (

6)]

Op

era

tio

n c

ost

(¢)

0.4

* (

7)

Fig

ure

s f

or

theo

reti

cal

min

imu

m

part

s E

sti

mati

on

6

5

4

3

2

1

1

1

1

1

1

2

30

10

10

05

23

11

1.95

1.50

1.50

1.84

2.36

1.80

00

02

00

00

08

39

1.5

2.5

1.5

1.5

6.5

8.0

3.45

4.00

3.00

3.34

8.86

19.60

1.38

1.60

1.20

1.34

3.54

7.84

1

1

1

1

0

0

42.25 16.90 4

TM CM NM

Main Block

Piston

Piston Stop

Spring

Cover

Screw

0.29 d e s i g n e f f i c i e n c y N M

T M = = 3 *

Name of Assembly

Pneumatic Piston




20

Redesigned Pneumatic Piston

1 - Snap on cover

and stop (plastic)

2 - Spring (steel)



22

Worksheet for Redesigned Piston

1

Pa

rt I.D

. N

um

be

r

2 3 4 5 6 7 8 9 N

um

ber

of

tim

es t

he

op

era

tio

n is c

arr

ied

ou

t co

nsecu

tively

Tw

o-d

igit

ma

nu

al

han

dli

ng

co

de

Ma

nu

al

ha

nd

lin

g

tim

e p

er

pa

rt

Tw

o-d

igit

ma

nu

al

ins

ert

ion

co

de

Ma

nu

al

inse

rtio

n

tim

e p

er

pa

rt

Op

era

tio

n t

ime

(se

c)

(2)*

[(4)

+ (

6)]

Op

era

tio

n c

ost

(¢)

0.4

* (

7)

Fig

ure

s f

or

theo

reti

cal

min

imu

m

part

s E

sti

mati

on

4

3

2

1

1

1

1

1

30

10

05

10

1.95

1.50

1.84

1.50

00

00

00

30

1.5

1.5

1.5

2.0

3.45

3.00

3.30

3.50

1.38

1.20

1.34

1.40

1

1

1

1

13.29 5.32 4

TM CM NM

Main Block

Piston

Spring

Cover & Snap

0.90 d e s i g n e f f i c i e n c y N M

T M = = 3 *

Name of Assembly

Pneumatic Piston

(re-design)




23

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

24

Example of Layered Assembly

Snaps

Snaps

25

Compliance and Assembly

Avoid Better Best

No Chamfers Bottom Part

Chamfered

Top Part

Chamfered

Both Parts

Chamfered

26

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

27

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

28

Nonfunctional External Feature for Orientation

This slot would be

hard to detect

Pin to help orient slot

Chamfer to help orient slot

29

Symmetry

Orientation Required

Preferred

30

Tangling

These parts can tangle easily

The same parts redesigned, will not tangle

31

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

32

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

33

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

34

Substitutes for Fasteners

Avoid designs that require fasteners

Design parts that snap together

35

Joining Moving Parts without Fasteners

C-Clip

Chamfere

d Surface Snaps

36

Fasteners

Preferred: Have flat vertical sides for vacuum pickup

Avoid

Socket Head Fillister Head Hex Head

Round Head Flat Head

Round Side Slant Side

37

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

38

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.

39

Motion and Design

Avoid: Three motions required for insertion

Slot

Snaps

Preferred: Only one motion required

40

DfA - Construction

Photographs courtesy of Dr. Singhose

41

Photographs courtesy of Dr. Singhose

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