This article is describing how to use DFA (design for assembly) method to decrease the cost, time and difficulty in assembly processes of a product. the product which is selected as reference is a toaster. Reduction of components and redesign of parts are some of the DFA method to provide the ease of assembly process.

1. 1
Design For Manufacturing and Assembly
TOASTER
MEHDI HOURMAND MM101120
ALI KARANDISH MM121003

2. DFMA
DFMA stands on Design for Manufacture and Assembly. DFMA is
the combination of two methodologies; Design For Manufacturing,
which means the design for ease of manufacture of the parts that will
form a product, and Design For Assembly, which means the design
of the product for ease of assembly.
DFMA is used as the basis for concurrent engineering studies to
provide guidance to the design team in simplifying the product
structure, to reduce manufacturing and assembly costs, and to
quantify improvements. The practice of applying DFMA is to
identify, quantify and eliminate waste or inefficiency in a product
design. DFMA is also used as a benchmarking tool to study
competitors’products, and as a should cost tool to assist in supplier
negotiations.
2

3. Introduction
The aim of this project is to identify unnecessary parts in
an assembly and to Specify assembly time and costs.
Reduction and redesign the parts is one task that is
useful to decrease the costs and time of assembling . In
this project, new design and old design have been
compared and the results of development has been
included.
3

4. Objective
-Numbering of parts in the original design
- Redesign of the product (Description, Justification and Sketches)
- Classification of each part for the new design
- Estimated Assembly time for new design
- Design efficiency of new product
- Discussion/Comparison of new with the old design
4

5. Product to be Studied
Toaster
The toaster is typically a small Mechanic-
electric kitchen appliance designed to toast
multiple types of Bread products. A typical
modern two-slice toaster draws from 600 to
1200 Watts and makes toast in 1 to 3 minutes.
There are also non-electrical toasters that can
be used to toast bread products over an open
fire or flame.
5

6. Numbering of parts in the original design
According to the Charts below the number of total parts in original design is : 82
6
Name of assembly:
TOASTER
1 2
The names of parts
PartI.D.number
Numberoftimesthe
operationiscarriedout
consecutively
Front plate 1 1
Small L plate (nut) 2 1
rivet 3 5
L Plate A 4 1
Small Fire proof plate 5 7
Medium Fire proof plate 6 1
Holder of moving system
guide
7 1
Guide 8 1
Spring 9 1
Main plate of moving
system
10 1
Handling plate 11 1
Holder of U shape plate 12 1
U shape 13 1
Plastic part of U plate female 14 1
Plastic part of U plate male 15 1
Name of assembly:
TOASTER
1 2
The names of parts
PartI.D.number
Numberoftimesthe
operationiscarriedout
consecutively
Name of assembly:
TOASTER
1 2
The names of parts
PartI.D.number
Numberoftimesthe
operationiscarriedout
consecutively
Name of assembly:
TOASTER
1 2
The names of parts
PartI.D.number
Numberoftimesthe
operationiscarriedout
consecutively
Heater board left 16 1
Heater board middle 17 1
Heater board right 18 1
Bread holder 19 2
Back plate 20 1
Upper cover 21 1
Wire connector 22 2
welding 23 4
Electrical kit 24 1
soldering 25 2
Timer regulator 26 1
Front cover 27 1
Snap fit 28 4
Stopper switch 29 1
Holder of stopper switch 30 1
Screw M3*6 31 5
Switch 32 1
Nut M3 33 1
Screw M3*20 34 1
connector plate 35 1
Washer 36 2
wire of plug 37 3
screw M3*6 small pitch 38 3
Holder of wire 39 1
Cover of wire 40 1
Screw M3*12 ,different
shape
41 2
Back cover 42 1
Side cover 43 2
Screw M3*12 large pitch 44 4
Screw M3*12 small pitch 45 1
Bottom cover 46 1
Holder of bottom
cover
47 1
Screw M4*6 48 1
Handling plastic part 49 1
0.179 82
Design Efficiency
total
part

7. Eliminated/Changed parts in the NEW design
7
Name of
assembly:
TOASTER
Mustthepartmoverelative
toallotherparts?
Mustthepartbemadeofa
differentmaterials?
Mustthepartbeseparateto
allowaccesstootherpartsit
encloses?
The names of
parts
Name of
assembly:
TOASTER
Mustthepartmoverelative
toallotherparts?
Mustthepartbemadeofa
differentmaterials?
Mustthepartbeseparateto
allowaccesstootherpartsit
encloses?
The names of
parts
Name of
assembly:
TOASTER
Mustthepartmoverelative
toallotherparts?
Mustthepartbemadeofa
differentmaterials?
Mustthepartbeseparatetoallow
accesstootherpartsitencloses?
The names of
parts
1 no yes yes Front plate
0 no no no Small L plate (nut)
0 no no no rivet
0 no no no L Plate A
1 no yes no
Small Fire proof
plate
1 no yes no
Medium Fire proof
plate
0 no no no
Holder of moving
system guide
1 no yes yes Guide
1 yes no yes Spring
1 no no yes
Main plate of moving
system
0 no no no Handling plate
0 no no no
Holder of U shape
plate
1 no yes yes U shape
1 no yes yes
Plastic part of U plate
female
1 no yes no
Plastic part of U plate
male
1 no yes yes Heater board left
1 no yes yes Heater board middle
1 no yes no Heater board right
1 yes no yes Bread holder
1 no yes yes Back plate
1 no yes yes Upper cover
1 no no yes Wire connector
1 no yes yes Electrical kit
1 no no yes brazing
1 yes no yes Timer regulator
1 no yes yes Front cover
0 no no no Snap fit
1 no no yes Stopper switch
0 no no no
Holder of stopper
switch
0 no no no
Screw M3*6
,Large pitch
1 no yes yes Switch
0 no no no Nut M3
0 no no no Screw M3*20
1 no yes no connector plate
0 no no no Washer
1 no yes yes wire of plug
1 no no yes
screw M3*6 small
pitch
1 no no yes Holder of wire
0 no no no Cover of wire
0 no no no
Screw M3*12 ,
shape
0 no no no Back cover
0 no no no Side cover
0 no no no
Screw M3*12
large pitch
1 no no yes
Screw M3*12
small pitch
1 no no yes Bottom cover
0 no no no
Holder of bottom
cover
0 no no no Screw M4*6
1 no yes yes
Handling plastic
part
Orange Color shows Eliminated parts
Green Color shows Changed parts

8. Introduction of Eliminated/Changed parts in the NEW design
8
OLD (Original) Design NEW Design
Front Plate
Small L plate
(nut)
Rivet
L Plate
A
Holder of moving
system guide
Large
fire
proof
Small fire
proof
Small fire
proof
Description:
New Front Plate has changed in the shown position. The Holder of moving system has been removed and replaced with
the folded part as you can see.
The other change is about the fireproof hole, it has standardized with same size according to the other holes.
Due to use just one shape of fire proof (Small size) .
NEW Front Plate
Eliminated Parts

9. Introduction of Eliminated/Changed parts in the NEW design
9
OLD (Original) Design NEW Design
Main plate of
moving system
Description:
New moving system has produced with one sheet and using of folding the sheet instead of attaching the parts by rivet.
NEW Moving System
Eliminated Parts
Handling plate
Holder of U shape
plate
Breads Holder
Rivet

10. Introduction of Eliminated/Changed parts in the NEW design
10
OLD (Original) Design NEW Design
Upper Cover
Description:
New Cover will cover all the parts easily . Also, the assembly time will reduce much.
Stopper switch will assemble in the electrical kit such as regulator and there is no need to any holder or fastener.
NEW Main
Cover
Eliminated Parts
Front Cover
Snap fit Stopper
switch
Holder of
stopper
switch
Stopper
holder
Fastener
Back Cover
Side Covers
NEW Stopper
Switch

11. Introduction of Eliminated/Changed parts in the NEW design
11
OLD (Original) Design NEW Design
Description:
Fastening method for new switch has been changed from Nut and bolt to snap fit.
Switch
Eliminated Parts
Switch
Nut Bolt
Washer

12. Introduction of Eliminated/Changed parts in the NEW design
12
OLD (Original) Design
NEW Design
Description:
The fastening method of Bottom Cover has been changed from old method to 4 screw and 4 snap fit which is fastened
to the main body and the main cover will assemble via Screw M3X12 Large pitch.
Bottom Cover
Eliminated Parts
Bottom Cover
Screw M3*12
small pitch
Holder of bottom
cover
Screw M4*6
Screw M3*12
large pitch

13. Introduction of Eliminated/Changed parts in the NEW design
13
OLD (Original) Design
NEW Design
Description:
The previous design for connector needs 8 welding and 2 connector. However, in the new design it is reduced to 4 welding.
Connector s
Eliminated Parts
NEW
Connectors
Welding

14. Description of each New Designed Parts of Toaster
Acc. To DFA Methods
14
picture
Nameofpart
PartIDNO.
No.ofpart
α
β
Two-digitmanual
handlingcode
Manualhandling
timeperpart
Two-digitmanual
insertioncode
Manualinsertion
timeperpart
Function
Front plate 1 1 360 360 30 1.95 00 1.5
Main role of front plate
is Holding the heater
board and moving
system
Small Fire
proof plate
2 5 180 180 13 2.06 32 4
To avoid connection
between wire and body

15. Description of each New Designed Parts of Toaster
Acc. To DFA Methods
15
picture
Nameofpart
PartIDNO.
No.ofpart
α
β
Two-digitmanual
handlingcode
Manualhandling
timeperpart
Two-digitmanual
insertioncode
Manualinsertion
timeperpart
Function
Cylindrical
Guide
3 1 360 0 11 1.5 32 4
To Control the sliding
movement of moving
system.
Spring 4 1 360 180 20 1.8 34 6
To Return the moving
system in its position
(Returning The breads)

16. 16
picture
Nameofpart
PartIDNO.
No.ofpart
α
β
Two-digitmanual
handlingcode
Manualhandling
timeperpart
Two-digitmanual
insertioncode
Manualinsertion
timeperpart
Function
moving system 5 1 360 360 30 1.95 06 5.5
Holding the handling
plate, Magnet, Bread’s
Holder. Also sliding
movement to move the
breads down and return it
up after toasting
Operation.
U shape 6 1 360 180 20 1.8 32 4
With Magnetic flux
allow the moving system
to connect and hold
down the breads.
Description of each New Designed Parts of Toaster
Acc. To DFA Methods

17. 17
picture
Nameofpart
PartIDNO.
No.ofpart
α
β
Two-digitmanual
handlingcode
Manualhandling
timeperpart
Two-digitmanual
insertioncode
Manualinsertion
timeperpart
Function
Plastic part of
U plate female
7 1 360 360 30 1.95 00 1.5
To avoid the connecting
of magnetic flux to the
other parts
Plastic part of
U plate male
8 1 360 360 30 1.95 00 1.5
To avoid the connecting
of magnetic flux to the
other parts
Description of each New Designed Parts of Toaster
Acc. To DFA Methods

18. 18
picture
Nameofpart
PartIDNO.
No.ofpart
α
β
Two-digitmanual
handlingcode
Manualhandling
timeperpart
Two-digitmanual
insertioncode
Manualinsertion
timeperpart
Function
Heater board
left
(Standard Part)
9 1 360 360 30 1.95 32 4 Toasting the breads
Heater board
middle
(Standard Part)
10 1 360 360 30 1.95 32 4 Toasting the breads
Description of each New Designed Parts of Toaster
Acc. To DFA Methods

19. 19
picture
Nameofpart
PartIDNO.
No.ofpart
α
β
Two-digitmanual
handlingcode
Manualhandling
timeperpart
Two-digitmanual
insertioncode
Manualinsertion
timeperpart
Function
Heater board
right
(Standard Part)
11 1 360 360 30 1.95 32 4 Toasting the breads
Back plate 12 1 360 360 30 1.95 33 5
Holding the heater
boards
Description of each New Designed Parts of Toaster
Acc. To DFA Methods

20. 20
picture
Nameofpart
PartIDNO.
No.ofpart
α
β
Two-digitmanual
handlingcode
Manualhandling
timeperpart
Two-digitmanual
insertioncode
Manualinsertion
timeperpart
Function
connector 13 2 180 180 10 1.5 96 12
Connecting the
electricity between heater
boards.
Electrical kit
(Standard Part)
14 1 360 360 30 1.95 92 5
Distribute the electricity
between heater boards,
Magnet system and
Setting the time of
toasting.
Description of each New Designed Parts of Toaster
Acc. To DFA Methods

21. 21
picture
Nameofpart
PartIDNO.
No.ofpart
α
β
Two-digitmanual
handlingcode
Manualhandling
timeperpart
Two-digitmanual
insertioncode
Manualinsertion
timeperpart
Function
Timer regulator 15 1 360 360 30 1.95 30 2
To Change the time of
toasting
Stopper switch 16 1 360 0 11 1.8 30 2
To Disconnect the
electricity
Description of each New Designed Parts of Toaster
Acc. To DFA Methods

22. 22
picture
Nameofpart
PartIDNO.
No.ofpart
α
β
Two-digitmanual
handlingcode
Manualhandling
timeperpart
Two-digitmanual
insertioncode
Manualinsertion
timeperpart
Function
Screw M3*6 17 2 360 0 11 1.8 38 6
Fastening the electrical
board
Switch
(Standard part)
18 1 360 360 30 1.95 30 2 Electricity Connector
Description of each New Designed Parts of Toaster
Acc. To DFA Methods

23. 23
picture
Nameofpart
PartIDNO.
No.ofpart
α
β
Two-digitmanual
handlingcode
Manualhandling
timeperpart
Two-digitmanual
insertioncode
Manualinsertion
timeperpart
Function
wire of plug 19 3 180 360 20 1.13 92 5 Transfer the electricity
screw M3*6
small pitch
20 3 360 0 11 1.8 38 6
Fastening the wire of
plug
Description of each New Designed Parts of Toaster
Acc. To DFA Methods

24. 24
picture
Nameofpart
PartIDNO.
No.ofpart
α
β
Two-digitmanual
handlingcode
Manualhandling
timeperpart
Two-digitmanual
insertioncode
Manualinsertion
timeperpart
Function
Screw M3*12
large pitch
21 4 360 0 11 1.8 38 6
Fastening the Main
Cover to the Bottom
cover
Bottom cover 22 1 360 180 20 1.8 30 2
To cover and maintain all
assembled parts and the
main cover.
Description of each New Designed Parts of Toaster
Acc. To DFA Methods

25. 25
picture
Nameofpart
PartIDNO.
No.ofpart
α
β
Two-digitmanual
handlingcode
Manualhandling
timeperpart
Two-digitmanual
insertioncode
Manualinsertion
timeperpart
Function
Top Cover 23 1 360 360 30 1.95 00 1.5
Covering all Sub
assembly parts.
Handling
plastic part
24 1 360 360 30 1.95 01 2.5
To ease of moving down
the breads by users
Description of each New Designed Parts of Toaster
Acc. To DFA Methods

26. 26
picture
Nameofpart
PartIDNO.
No.ofpart
α
β
Two-digitmanual
handlingcode
Manualhandling
timeperpart
Two-digitmanual
insertioncode
Manualinsertion
timeperpart
Function
Holder of wire 25 1 360 360 31 2.25 00 1.5 Holding the wire
Description of each New Designed Parts of Toaster
Acc. To DFA Methods

27. 27
Product tree structure for new design
Toaster
1-Main Body 2-Top Cover 3- Bottom Cover 4- Handling Plastic
Part
3- Holder of wire1-Electrical kit
2-Time Regulator 3- Stopper switch
2- Switch
Sub assembly is in
the next page
1- Screw M3*6
1- Screw M3*12
large pitch

28. 28
Product tree structure for new design
Toaster
1-Main Body
2- Cylindrical Guide1- Front plate 3- Spring 4- moving system 5- Heater board left 6- Heater board middle 7- Heater board right 8-Back plate
9- connector10- wire of plug
1- Small Fire
proof plate
1- U shape
Plate
2- Plastic part
of U plate female
3- Plastic part
of U plate male
1- screw M3*6
small pitch
2-Top Cover 3- Bottom Cover 4- Handling Plastic
Part

29. 29
Assembly

30. 30
Assembly
Assembly
Sketches

31. 31
Classification and analysis for each part of the new
design
Name of assembly: TOASTER 1 2 3 4 5 6 7 8 9
The names of parts
PartI.D.number
Numberoftimesthe
operationiscarried
outconsecutively
Two-digitmanual
handlingcode
Manualhandlingtime
perpart
Two-digitmanual
insertioncode
Manualinsertiontime
perpart
Operationtime(sec)
2*[4+6]
Operationcost
(RM)
Figuresfortheoretical
minimumparts
estimation
Front plate 1 1 30 1.95 0 0 1.5 3.45 0.004485 1
Small Fire proof plate 2 5 13 2.06 32 4 30.3 0.03939 5
Guide 3 1 11 1.5 32 4 5.5 0.00715 1
Spring 4 1 20 1.8 34 6 7.8 0.01014 1
Moving System 5 1 30 1.95 0 6 5.5 7.45 0.009685 1
U shape 6 1 20 1.8 32 4 5.8 0.00754 1
Plastic part of U plate female 7 1 30 1.95 0 0 1.5 3.45 0.004485 1
Plastic part of U plate male 8 1 30 1.95 0 0 1.5 3.45 0.004485 1

32. 32
Classification and analysis for each part of the new
design
Name of assembly: TOASTER 1 2 3 4 5 6 7 8 9
The names of parts
PartI.D.number
Numberoftimesthe
operationiscarried
outconsecutively
Two-digitmanual
handlingcode
Manualhandlingtime
perpart
Two-digitmanual
insertioncode
Manualinsertiontime
perpart
Operationtime(sec)
2*[4+6]
Operationcost
(RM)
Figuresfortheoretical
minimumparts
estimation
Heater board left 9 1 30 1.95 32 4 3.56 0.004628 1
Heater board middle 10 1 30 1.95 32 4 3.56 0.004628 1
Heater board right 11 1 30 1.95 32 4 3.56 0.004628 1
Back plate 12 1 30 1.95 33 5 6.95 0.009035 1
Wire connector 13 2 10 1.5 96 12 27 0.0351 2
Electrical kit 14 1 30 1.95 92 5 6.95 0.009035 1
Timer regulator 15 1 30 1.95 0 1 2.5 4.45 0.005785 1
Stopper switch 16 1 11 1.8 30 2 3.8 0.00494 1
Screw M3X6 17 2 11 1.8 38 6 15.6 0.02028 2
Switch 18 1 30 1.95 30 2 3.95 0.005135 1

33. 33
Classification and analysis for each part of the new
design
Name of assembly: TOASTER 1 2 3 4 5 6 7 8 9
The names of parts
PartI.D.number
Numberoftimesthe
operationiscarried
outconsecutively
Two-digitmanual
handlingcode
Manualhandlingtime
perpart
Two-digitmanual
insertioncode
Manualinsertiontime
perpart
Operationtime(sec)
2*[4+6]
Operationcost
(RM)
Figuresfortheoretical
minimumparts
estimation
wire of plug 19 3 20 1.13 92 5 18.39 0.023907 3
screw M3*6 small pitch 20 3 11 1.8 38 6 23.4 0.03042 3
Holder of wire 21 1 31 2.25 0 0 1.5 3.75 0.004875 1
Screw M3*12 long pitch 22 4 11 1.8 38 6 7.8 0.01014 4
Bottom cover 23 1 20 1.8 30 2 3.8 0.00494 1
Top Cover 24 1 30 1.95 0 0 1.5 3.45 0.004485 1
Handling plastic part 25 1 30 1.95 0 1 2.5 4.45 0.005785 1
25
Total
different
part
0.4851
Design Efficiency
38
Total part
235.02 0.305526 38
TM CM NM

34. 34
Discussion – Comparison between New design and Old design
New Design
The formula to calculate the design efficiency :
Design efficiency =(3*NM)/TM
* NM = Theoretical minimum number of parts
According to DFA worksheet, NM= 38
*TM = Total manual assembly time
According to DFA worksheet, TM= 235.02
*CM = Total Cost of Manual assembly
According to DFA worksheet, CM= 0.305
Design Efficiency = (3*38)/235.02 = 0.485
Old Design
The formula to calculate the design efficiency :
Design efficiency =(3*NM)/TM
* NM = Theoretical minimum number of parts
According to DFA worksheet, NM= 38
*TM = Total manual assembly time
According to DFA worksheet, TM= 641.24
*CM = Total Cost of Manual assembly
According to DFA worksheet, CM= 0.833
Design Efficiency = (3*38)/641.24 = 0.178

35. 35
Discussion – Comparison between New design and Old design
No. Criteria Old Design New Design Improvement Percentage
1 Design Efficiency (%) 17.8 % 48.5 % 30.7 % 30.7%
2 Assembly Time (sec) 641.24 sec 235.02 sec 249.62 sec 36.65%
3
Total Assembly Cost
(RM)
0.833 RM 0.305 RM 0.528 RM 36.6%
4
Total Number Of Different
Parts
49 25 24 51%
5 Fasteners 32 12 20 37.5%

36. 36
Conclusion
Based On Design For Assembly (DFA) Guideline, The aims of this method
have been satisfied by:
- Simplifying the assembly sequences, component handling and insertion.
- Standardize the materials , components and subassemblies to increase
economics of scale and reduce tooling costs.
- Reduction of mass production of many parts.
- Taking the advantage of process capability to reduce unnecessary
components of additional processing.
In addition, the new design outcome is available in below.
* Design efficiency has been improved 30.7 %
* Assembly time has been reduced 249.62 sec
* Manual assembly cost has been reduced 0.528 RM
* Total Eliminated different part is 24

37. 37
Appendix B1

38. 38
Appendix B2

39. 39
References
1- Boothroyd, G., Dewhurst, P. & Knight, W. (1994), “Production Design for
Manufacturing and Assembly”, New York: Marcel Dekker, Inc.
2- http://www.investinpahang.gov.my/index.php?rp=comptetitive_wages.pdf
3- Norcross, Eric (2006). "The Cyber Toaster Museum". Toaster.org. The Toaster
Museum Foundation. pp. section "1900–1920". http://www.toaster.org/museum.html.
Retrieved 2008-08-16.
4- http://en.wikipedia.org/wiki/Toaster
5- http://www.dfma.com/software/index.html

40. 40