dfma stapler

DFMA as Applied to the Swingline® 747 Desktop Stapler.

Department of Mechanical Engineering, The University Of Utah, Salt Lake City, Utah.

Group Members

Xiaofan Xie, Vamsi Uppalapati, Charan R. Sarjapur Naveen Huilgol, Clief Castleton

Submitted 7 April 2003

To

Dr. A.K. Balaji

i

Table of Contents

List of Figures and Tables… … … … … … … … … … … … … … … … … … … … … … … .iv

Abstract…………………… … … … … … … … … … … … … … … … … … … … … … … .vi

1 I n t r o d u c t i o n … … … … … … … … … … … … … … … … … … … … … … … … .… … … … 1

1.1General Stapler Propert ies……………………………………………………..1

2 DFMA Paradigms and Analyses………………………………………… .… … … … 8

2.1Material Selection Paradigms………………………………………… … … … . 8

2.2 Material Selection of the Stapler…………………………………………….10

2.3 Recommended Changes………………………………………..… … … … … 11

2.4 Manufacturing Methods of the Stapler…………………………..… … … … . 11

2.4aSheet Metal Analyses … … … … … … … … … … … … … … … … … .…….13

2.4aiAnalysis for the Original Upper Staple Guide……………………13

2.4aii Analysis for the Changed Upper Staple Guide……… … … … … ..18

2.4a iii Abbreviated Analyses Results for Other Parts……… … … … … 23

2.5 Assembly Paradigms……………………………………… … … … … ..…….25

2.5a Assembly Times and Efficiency……………………………………….25

2.5b Guidelines for Manual Assembly…………………………………….. .26

2.5c Effects of Weight and Dimension…………………………………….. .26

2.5d C h a m f e r s … … … … … … … … … … … … … … … … … … … … … … … … 2 7

2.5e Miscellaneous Effects on Assembly Time……………………….…….28

2.5f Further Gui d e l i n e s … … … … … … … … … … … … … … … … … … … … . . 2 8

2.5g Assembly Layou t…………………………………………….… … ..…29

2.6 Assembly of the Stapler………………………………………….… … … ….30

2.6a Efficiency… … … … … … … … … … … … … … … … … … … … … … … . . . 3 1

2.6b C h a m f e r s … … … … … … … … … … … … … … … … … … … … … ...……31

2.7 Recommended Changes… … … … … … … … … … … … … … … … … … … … 3 1

3 D i s c u s s i o n … … … … … … … … … … … … … … … … … … … … … … … … … ..… … .32

4 C o n c l u s i o n … … … … … … … … … … … … … … … … … … … … … … .… … . … … … 33

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Appendix A: Material Selection Analyses………………………………………34

Appendix B: Manufacturing Process…………………………………………… 49

Appendix C: ProE© P a r t s D r a w i n g s … … … … … … … … … … … … … … … … … .51

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List of Figures and Tables

Figures

1. Rubber Pad… … … … … … … … … … … … … … … … … … … … … … … … … … … . . 2

2. Release Clip… … … … … … … … … … … … … … … … … … … … … … … … … … … . 3

3. Closed Stapler Function… … … … … … … … … … … … … … … … … … … … … … . . 3

4. Open Stapler Function… … … … … … … … … … … … … … … … … … … … … … … . 3

5. Lower Leaf Spring… … … … … … … … … … … … … … … … … … … … … … … … ...3

6. Anvil… … … … … … … … … … … … … … … … … … … … … … … … … … … … … … 4

7. Pinning vs. Stapling… … … … … … … … … … … … … … … … … … … … … … … … . 4

8. Base… … … … … … … … … … … … … … … … … … … … … … … … … … … … … … . 4

9. Anvil Actuator… … … … … … … … … … … … … … … … … … … … … … … … … … . 4

10. Spacer… … … … … … … … … … … … … … … … … … … … … … … … … … … … … . . 5

11. Spring… … … … … … … … … … … … … … … … … … … … … … … … … … … … … . . 5

12. Pin… … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … 5

13. Staple Guide… … … … … … … … … … … … … … … … … … … … … … … … … … … 5

14. Staple Slide… … … … … … … … … … … … … … … … … … … … … … … … … … … . . 6

15. Upper Arm… … … … … … … … … … … … … … … … … … … … … … … … … … … . . . 6

16. Upper Staple Guide… … … … … … … … … … … … … … … … … … … … … … … … . 6

17. End Cap… … … … … … … … … … … … … … … … … … … … … … … … … … … … . . . 7

18. Upper Leaf Spring… … … … … … … … … … … … … … … … … … … … … … … … . . . 7

19. Upper Cover… … … … … … … … … … … … … … … … … … … … … … … … … … … 7

20. Plastic Cover… … … … … … … … … … … … … … … … … … … … … … … … … … … 8

21. Stress-Strain Plots… … … … … … … … … … … … … … … … … … … … … … … … … 9

22. General Trends… … … … … … … … … … … … … … … … … … … … … … … … … … 9

23. Bench Station… … … … … … … … … … … … … … … … … … … … … … … … … … 2 9

24. Multi-Station… … … … … … … … … … … … … … … … … … … … … … … … … … . 2 9

25. Modular Station… … … … … … … … … … … … … … … … … … … … … … … … … . 2 9

26. Custom Layout… … … … … … … … … … … … … … … … … … … … … … … … … . . 3 0

27. Flexible Layout… … … … … … … … … … … … … … … … … … … … … … … … … . . 3 0

v v

28. B a s e … … . . … … … … … … … … … … … … … … … … … … … … … … … … … … … .34

29. R e d e s i g n … … … … … … … … … … … … … … … … … … … … … … … … … … … … 34

Tables

1. Specifications of the Stapler… … … … … … … … … … … … … … … … … … … … … 1

2. Stapler Components… … … … … … … … … … … … … … … … … … … … … … … … . 2

3. Brief Overview Data… … … … … … … … … … … … … … … … … … … … … … … . . 11

4. Manufacturing Processes… … … … … … … … … … … … … … … … … … … … … . . . 1 2

5. Insertion Parameters… … … … … … … … … … … … … … … … … … … … … … … . . 2 7

6. Handling Times Data… … … … … … … … … … … … … … … … … … … … … … … . 3 0

7. Insertion Parameters fo r the Pin… … … … … … … … … … … … … … … … … … … 3 1

vi

ABSTRACT:

An analysis of the Swingline® Classic 747 desktop stapler is presented with a focus

on stapler components and their functions, materials, and other specifications. The

methods and paradigms used for analysis of manufacture, assembly, materials

selection, cost, times, and other factors follow those set forth by Boothroyd Dewhurst

Inc.’s Design for Manufacture and Assembly as found in Product Design for

Manufacture and Assembly, 2nd edition by Boothroyd, Dewhurst, and Knight.

DFMA as Applied to the Swingline® 747 Desktop Stapler

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1 Introduction As an introduction to DFMA paradigms and processes, the analysis of the Swingline®

Classic 747 stapler is presented. This full-strip desktop stapler has been on the market for

over 30 years. The stapler design is classic and therefore any part of the stapler could be

considered sufficient and require no change. However, the aim of this project was to

perform DFMA analyses on the components to determine if changes were possible and, if

needed, to have justified those changes. A materials selection analysis was run on all

parts except one. Manufacturing analyses were run for sheet metal operations for four

parts and the assembly sequence and time was derived based on certain plausible

assumptions. The DFMA paradigms applied to this project will be discussed as they are

used; viz. the paradigms for manufacturing are discussed prior to the presentation of

manufacturing methods for the stapler, etc. We begin with the stapler specifications,

functions, and capabilities.

1.1 General Stapler Properties The basic specifications of the stapler are given in Table 1. It should be stated that there

are various styles and capacities of staplers with various specifications. The 747, as with

other models, meets the required performance capacities.

Table 1. Specifications of the Stapler [1]

Stapling capability 20 sheet capacity

Staple type S.F.4 standard staples

Staple number 210

Jam-resistant Yes

Staple reload indicator

Yes

Height 60mm (2.36ins)

Width 45mm (1.77ins)

Length 200mm (7.88ins)

Weight 529g (1.167lbs)


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The stapler is designed to be used in three ways. The first two are dependent upon the

orientation of the anvil, which provides for stapling and pinning. The stapler can also be

opened to be used in tacking sheets to the wall. Table 2 shows the 17 components,

excluding fasteners, of the 747 and the material of which each is believed to be made.

There was a level of uncertainty in some cases, so an educated guess was made. A brief

description of each part and its function and properties follows with pictures of each part.

1. Rubber Pad:

Fig 1 Rubber Pad

The function of the rubber pad was identified as providing a good grip on the working

surface, protecting the surface, and covering the cavities on the bottom of the base. Due

to its material, it also provides a damping of vibrations while in use, which leads to better

ergonomic use of the stapler.

Component Name Actual Material

Rubber Pad Rubber

Release Clip Aluminum Alloy Lower Leaf Spring Spring Steel Anvil Alloy Steel Base Aluminum Alloy Anvil Actuator Aluminum Alloy Spacer Plastic Spring Spring Steel (Alloy Steel) Pin Alloy Steel Staple Slide Aluminum Alloy (Cu Coating) Bottom Staple Guide Aluminum Alloy Upper Arm Alloy Steel Upper Staple Guide Aluminum Alloy End Cap(747) Alloy Steel Upper Leaf Spring Spring Steel (Alloy Steel) Upper Cover Alloy Steel Plastic Cover Plastic

Table 2 – Stapler Components


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2. Release Clip

Fig 2 Release Clip

In order to facilitate tacking, when depressed the stapler base and cover assemblies can

open to 180 degrees. The unlocking mechanism allows the use of staples without

bending the ends. The clip also provides a locking mechanism between the base and the

upper arm when in desktop use. See figures 3 and 4. The release clip also provides a

springing action to the upper arm by means of connecting it with the lower leaf spring.

Fig 3 [2] When the release clip is in the locked position we have the ends of the staple bent by the anvil.

Fig 4 [2] When the release clip is in the unlocked position we have the ends of the staple go through the paper without being bent by the anvil.

3. Lower Leaf Spring

Fig 5 Lower Leaf

The lower leaf provides springing action for the anvil actuator which helps in rotating the

anvil and, along with the release clip , provides the restoring force to the upper arm,

allowing the stapler to return to initial orientation.


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4. Anvil

Fig 6 Anvil

The main function of the anvil is to provide a guiding mechanism for the staple ends.

Figure 7 shows the two stapling methods which can be achieved by rotating the anvil.

The left-hand figure shows that the anvil is set for conventional stapling, giving a more

secure hold, while the right-side figure shows a configuration providing a looser pinning

of the sheets that can easily be taken apart.

Fig 7 [2]

5. Base

Fig 8 Base

The base houses the rubber base, anvil, anvil actuator and lower leaf spring. Along with

the pin, it also provides the necessary hinging action between the upper and the lower

assemblies.

6. Anvil Actuator

Fig 9 Anvil Actuator The anvil actuator holds the anvil in place and also helps in rotating the anvil. Connected

to the lower leaf, it will automatically reset the anvil in its well when released.

Staple

Anvil


5

7. Spacer

Fig 10 Spacer

The spacer supports the pin. It also holds the upper assembly and the lower assembly in

place. It is also believed to aid in the assembly of the upper and lower parts. (See

assembly section for further details.)

8. Spring

Fig 11 Spring

The spring along with the staple slide helps in pushing the staples forward, maintaining

adequate forward force on the staples, and when reloading removes the staple slide to the

rear.

9. Pin

Fig 12 Pin

It provides the necessary hinging action between the upper and the lower assemblies as

well as keeps the stapler together.

10. Bottom Staple Guide

Fig 13 Bottom Staple Guide The staple slide and staples rest on the bottom staple guide.


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11. Staple Slide

Fig 14 Staple Slide

The staple slide along with the spring helps in the feeding of the staples. The staple slide

moves along the staple guide. The copper coating helps in indicating the amount of

staples left in the stapler when viewed through the opening in the upper arm.

12. Upper Arm

Fig 15 Upper Arm

The upper arm houses the staple guide sub-assembly. It is an important component of the

upper assembly. Through a narrow opening at the distal end of the upper arm, the level of

remaining staples is visually indicated. It also keeps the cover secure while in use. The

upper leaf pushes out the staples through the gap in the front of the arm.

13. Upper Staple Guide

Fig 16 Upper Staple Guide The upper staple guide keeps the staples from coming off the lower guide and provides a

point of attachment for the spring as well as a turning point for the spring.


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14. End Cap

Fig 17 End Cap

The end cap helps in preventing the spreading out of the upper arm. It also serves as a

logo marquee.

15. Upper Leaf Spring

Fig 18 Upper Leaf Spring

The upper leaf spring provides the springing action between the upper arm and the upper

staple guide. It also serves the vital function of pushing out the staples.

16. Upper Cover

Fig 19 Upper Cover

The main function of the upper cover is to hold the upper assembly. The main

components held by the upper arm are the upper staple guide, upper leaf spring, and the

plastic cover.


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17. Plastic Cover

Fig 20 Plastic Cover

The plastic cover mainly serves as an advertising plate for Swingline®. It also covers the

holes in the upper cover.

2 DFMA Paradigms and Analyses

What follows is the discussion of DFMA paradigms and their application to three

areas; material selection, manufacturing, and assembly. In each area, the general

paradigms will be followed by their application to specific parts of the product.

2.1 Material Selection – General Paradigms

There are several factors which bear consideration while designing a product.

Among these are weight, strength, cost, durability, environment, aesthetics, etc. Each one

of these can affect the design both from the manufacture and assembly aspects. A part

that is designed for optimum manufacturability with a specific material may give rise to

assembly issues. The converse is also true. While still in the design phase, giving

thought to these factors will help reduce problems in the subsequent stages. With respect

to the mass of the material, and therefore the weight, some thoughts might go to whether

the product needs to be portable, if it will be manufactured on-site, what loads will be

placed on it, what are the costs involved, and so forth. Strength of the material selected is

also important primarily to prevent failure of the design. Figure 21 shows the stress-

strain plots for various materials. A DFMA analysis of a part might yield wood as the

best possible choice when considering cost and ease of manufacturability, as was the case

with one component of the stapler. However, functional analysis would identify that

material to be inadequate as it would fail under normal operating conditions. Figure 22

describes several general trends in relation to strength of materials.


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Fig 21 Stress Strain Plot for Various Materials [3]

n E (Young’s Modulus) is the slope of the stress-strain (σ−ε) curve. n Metals are stronger than other materials n Woods are stronger than some plastics but may break before much elongation. n Plastics have odd behavior but can be useful. n Rubbers are soft but can deform a great deal before failure. n Some materials do not have well defined yield stresses. If not given, use σT.

Figure 22 General Trends [3]

In order to achieve optimal overall costs, which is vital in a competitive market, the costs

of manufacture and assembly of the product must be considered early. DFMA provides

several methods which can be carried out by hand or computer that will analyze designs

based on projected costs. The specifics not used in our analysis are available in the text

by Boothroyd, Dewhurst, and Knight or in the DFMA software. A final product which is

too costly as a result of poor planning and inefficient methods will be priced out of the

market. Other factors also should contribute in the initial design phases. The product

should be durable and aesthetic, given toda y’s consumer-driven market. Also,

environmental issues in manufacture, governed by political climates, must also be dealt

with, as well as problems that may be caused by the environment in which the product

Metals

Plastics

Rubbers

Woods

σ

ε

σu

σy


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will be used. Weather, temperature, soil acidity, and a host of other factors may affect

the lifetime of the product, which in turn can also affect the design. As was mentioned,

the optimal design for one aspect might be the least desirable for another.

One of the key material selection paradigms in DFMA is the derived parameter

ranking. This enables the designers to rank each material depending on the desired

property or ratios of related properties. According to the resulting data, proper selection

of material can be better made.

2.2 Material Selection – Stapler

The full material selection data obtained by using DFMA equations is available in

appendix A. Appendix B gives the selection criterion for DFMA. Table 3 gives a limited

overview of the materials selection for each of the 17 primary parts of the 747 stapler. It

is a brief presentation of what material DFMA suggests should be used for each part

based on different criteria. Some parts were not analyzed due to their apparent adequacy,

i.e. no materials change was deemed necessary. The column labeled analysis run

indicates the criteria desired. The three subsequent columns give the material best suited

for those criteria under certain conditions. For example, the release clip analysis was run

to obtain the strongest beam. The material yielding the maximum performance is alloy

steel. The minimum weight is achieved with aluminum. The minimum cost material is

cast iron. The variance of materials offered by the analysis is indicative of the subjective

nature of DFMA; sometimes a decision must be made when the data present conflicting

results. The last column of Table 3 indicates what is believed to be the actual material of

which the part is made.


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Table 3 - Brief overview data on material selection for 747 stapler parts. Note: The detailed results for the above analysis have been attached (Appendix A).

2.3 Recommended Changes

While an analysis was run on each of the parts that was believed to require change,

the DFMA analysis revealed that the presumed actual materials already were properly

chosen. Therefore, no recommended changes to the materials used in the Swingline ® 747

stapler can be made. While change was considered for the cover and base from metal to

plastic, it was decided to leave them metal due to strength and durability issues.

2.4 Manufacturing Method of Stapler

Table 4 shows the various parts of the stapler along with the various

manufacturing processes along with the sub-operations. Thereafter is given the sheet

metal analysis for several stapler components. Guidelines for design for manufacturing

are given in Appendix C. The specific equations and numerical analysis is given in

No. Component Name Analysis Run Maximum Performance Minimum Weight Minimum Cost Actual Material

1 Rubber Pad NA NA NA NA Rubber

2 Release Clip Strongest beam Alloy steel Aluminum Cast Iron Aluminum

3 Lower Leaf Spring Best Diaphragm Spring Beryllium copper Beryllium copper Ductile iron Spring Steel

4 Anvil Strongest plate Beryllium copper Aluminum Cast Iron Steel

5 Base Strongest plate Beryllium copper Aluminum alloy Cast Iron Aluminum

6 Anvil Actuator Strongest Ten Member Alloy steel Alloy steel Ductile iron Aluminum

7 Spacer NA NA NA NA Plastic

8 Spring Best Coil Spring Beryllium copper Alloy steel Ductile iron Spring Steel

9 The Pin Strongest beam Alloy steel Aluminum alloy Ductile iron Alloy Steel

10 Staple Slide Strongest Comp Member Alloy steel Alloy steel Gray cast iron Al (Cu Coating)

11 Bottom Staple Guide Light Weight NA NA NA Aluminum

12 The Upper Arm Strongest beam Alloy steel Aluminum alloy Ductile iron Steel

13 Top Staple Guide Light Weight NA NA NA Aluminum

14 End Cap(747) Strongest Plate Alloy steel Aluminum alloy Ductile iron Steel

15 Upper Leaf Spring Best Diaphragm Spring Beryllium copper Beryllium copper Ductile iron Spring Steel

16 Upper Cover Strongest beam Alloy steel Aluminum alloy Ductile iron Alloy Steel

17 Plastic Cover NA NA NA NA Plastic


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whole for the upper staple guide. The analyses for the other parts, while completed fully,

have been limited in this paper to the presentation of the results. This was done for

brevity. The information in the last columns of Table 4 is not given in order of process

sequence.

Table 4 – Manufacturing Processes

No Component Name Manufacturing Processes Operations

1 Rubber Pad Molding NA

2 Release Clip Sheet Metal working Part-off, Punching, Bending

3 Lower Leaf Spring Sheet Metal working Part-off, Punching, Bending, Plating

4 Anvil Sheet Metal working Blanking, Punching, Bending

5 Base Die casting Painting

6 Anvil Actuator Die casting Painting

7 Spacer Injection Molding NA

8 Spring Coiling Coiling, Bending, Plating

9 Pin Casting Turning, Knurling, Copper Coating

10 Staple Slide Sheet Metal working Blanking, Punching, Bending

11 Bottom Staple Guide Sheet Metal working Blanking, Punching, Bending

12 Upper Arm Sheet Metal working Blanking, Punching, Bending, Plating, Embossing

13 Upper Staple Guide

Sheet Metal working Blanking, Punching, Bending, Embossing

14 End Cap(747) Sheet Metal working Part-off, Bending, Embossing, Plating

15 Upper Leaf Spring Sheet Metal working Part-off, Punching, Bending, Plating

16 Upper Cover Sheet Metal Forming Drawing, Ironing

17 Plastic Cover Injection Molding Printing


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2.4a Sheet Metal Analyses

Equations and tables used for the following calculations are from [4].

2.4a.i Upper Staple Guide

Material: - Aluminum Gauge Number: -20 Thickness: - 1.02 mm Ultimate tensile strength: - 90 MN/m2

Cost of blanking die:

Taking 50 mm tolerances on four sides

Usable area = Au = 25.5*14.6 = 372.3 cm2

Cost of die set = Cds = 120 +0.36*Au = $ 255.

Profile complexity = Xp = P2/LW

L = 155 mm = 15.5 cm W = 46 mm = 4.6cm P = 432.5 mm = 43.25 cm

Therefore, Xp = 26.23

Total die manufacturing points:

Basic manufacturing points poM

From Fig. 9.9 poM = 33

Plan area = 71.3 cm2

Plan area correction factor wf1 from Fig. 9.10 wf1 = 1.75

Assuming number of parts to be produced as 500,000 hd = 21.31 mm from Equation (9.3)

Now considering hd = 25 mm


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Die plate thickness correction factor from Equation (9.5) is fd = 0.5 +0.02* hd = 1

Thus, total die manufacturing points are therefore Mp = fd*f1w*Mpo = 1*1.75*33 = 57.75

The estimated blanking die cost, assuming $40/hr for die making, is = Cds + Mp*40 = 255 + 57.75*40 = $2565. Scrap percent:

Area of each part is

Ap =19.5 + 6.875 + 4878 + 190 + 57.5 + 130 = 52.82 cm2

Area of sheet used for each part is

As = (15.5 + 0.204)*(4.6 + 0.204) = 75.44 cm2

Scrap % = (As – Ap)/As = .30 = 30 % Cost of piercing die: Cds = $255, L = 138.75 mm = 13.875 cm, W = 39.5 mm = 3.95 cm

The base manufacturing score from eq. (9.7) is

Mpo = 23 + 0.03 LW = 24.64

The number of hours required to manufacture the custom-punching element for the non-standard aperture is, from eq. (9.8)


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Pp = 112 mm = 11.2 cm, Np = 2 Mpc = 8 + 0.6 * Pp + 3 Np = 20.72

The equipment manufacturing time for punches, die plate inserts is, from eq. (9.9) Round holes K = 2, Np = 4, Nd = 1 Mps = K*Np + 0.4 Nd = 8.4

Rectangular holes K = 3.5, Np = 2, Nd = 2 Mps = K*Np + 0.4 Nd = 7.8 Total Mps = 16.2

The estimated piercing die cost, assuming $40/h for die making, is = Cds + ( Mpo + Mpc + Mps )*40 = $2720 Cost of bending die: Cds = $255, L = 155 mm = 15.5 cm, W = 46 mm = 4.6 cm, D = 1.7 cm

Basic die manufacturing score for bending Mpo = (18 + 0.023LW)*(0.9 + 0.02 D) = 18.34

Additional point for bend length and multiple bends Lb = 28.525 cm, Nb = 7 Mpn = 0.68 Lb + 5.8 Nb = 60


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The estimated bending die cost, assuming $40/h for die making, is = Cds + ( Mpo + Mpn) * 40 = $3390 Cost of embossing die: Cds = $255, L = 80 mm = 8 cm, W = 26 mm = 2.6 cm, Mpx = 0.13 Nsp Mpo = 23 + 0.03 LW Mpc = 8 + 0.6 Pp + 3 Np

Therefore, Mpo = 23.624

Rectangular embossing Mpx = 4 *(0.13*3) = 1.56

Circular embossing Mpx = 2 * (0.13 * 1) = 0.26

Total Mpx = 1.82 Mpc = 8 + 0.6 * 7.8 + 3 * 6 = 30.68

Cost of embossing die is, = Cds + ( Mpo + Mpc + Mpx) * 40 = $2500 Cost of progressive die: Cd = 2 Cid


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Where

Cid = 2565 + 2720 + 3390 + 2500 = $11175 Cd = $22350 Cycle time for each part: U = 90*103KN/m2 h = 1.02 mm = 1.02 * 10-3 m

Force for Blanking: Fblanking = 0.5UhLs

Where Ls = length to be sheared = 43.45 cm = 0.4325 m Fblanking = 19.85 KN

Force for Punching: Fpunching = 0.5UhLs

Where Ls = 260 mm = 0.26m

Fpunching = 11.93 KN

Force for Embossing:

For one embossing Fembossing = UhLsSinθ = 5.06 since Ls = 0.078m Total Fembossing = 6 * 5.06 (As they are six embossing effects) = 30.38 KN

Force for Bending: Fbendung = 0.08UhLb

Where Lb = Length of bend = 28.525 cm = .28525 m Fbendung = 2.094 KN


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So, Total force required = Fblanking + Fpunching + Fembossing + Fbendung = 64.25 KN = 65 KN

From Table 9.3 The space required for 4 die stations is, 4*14.6 = 58.4

From Table 9.8 Appropriate press for 58.4 is 500 KN press force, $76/hr operating cost and

speed of 90 strokes/min.

The estimated cycle time per part is, t = 60/90 =0.67 sec

Processing cost per part is Cp = (0.67/3600)*76*100 = 1.4 cents. 2.4aii Sheet metal analysis for changed part: Cost of blanking die:

Taking 50 mm tolerances on four sides

Usable area = Au = 25.5*14.6 = 372.3 cm2

Cost of die set = Cds = 120 +0.36*Au = $ 255.

Profile complexity = Xp = P2/LW

L = 155 mm = 15.5 cm W = 46 mm = 4.6cm P = 395.5 mm = 39.55 cm

Therefore, Xp = 21.93

Total die manufacturing points

Basic manufacturing points poM

From Fig. 9.9 poM = 32


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Plan area = 71.3 cm2

Plan area correction factor wf1 from Fig. 9.10

wf1 = 1.75

Assuming number of parts to be produced as 500,000 hd = 21.31 mm from Equation (9.3)

Now considering hd = 25 mm

Die plate thickness correction factor from Equation (9.5) is fd = 0.5 +0.02* hd = 1

Thus, total die manufacturing points are therefore Mp = fd*f1w*Mpo = 1*1.75*32 = 56

The estimated blanking die cost, assuming $40/hr for die making, is = Cds + Mp*40 = 255 + 56*40 = $2495. Scrap percent:

Area of each part is Ap = 51.52 cm2

Area of sheet used for each part is As = (15.5 + 0.204)*(4.6 + 0.204) = 75.44 cm2

Scrap % = (As – Ap)/As = .32 = 32 %


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Cost of piercing die: Cds = $255, L = 138.75 mm = 13.875 cm, W = 39.5 mm = 3.95 cm

The base manufacturing score from eq. (9.7) is

Mpo = 23 + 0.03 LW = 24.64

The number of hours required to manufacture the custom-punching element for the nonstandard aperture is, from Eq. (9.8)

Pp = 150.5 mm = 15.05 cm, Np = 3 Mpc = 8 + 0.6 * Pp + 3 Np = 26.03

The equipment manufacturing time for punches, die plate inserts is, from Eq. (9.9) Round holes K = 2, Np = 4, Nd = 1 Mps = K*Np + 0.4 Nd = 8.4

The estimated piercing die cost, assuming $40/h for die making, is = Cds + ( Mpo + Mpc + Mps )*40 = $2617.8 = $2620 Cost of bending die: Cds = $255, L = 155 mm = 15.5 cm, W = 46 mm = 4.6 cm, D = 1.7 cm

Basic die manufacturing score for bending Mpo = (18 + 0.023LW)*(0.9 + 0.02 D) = 18.34

Additional point for bend length and multiple bends Lb = 26.225 cm, Nb = 3 Mpn = 0.68 Lb + 5.8 Nb


21

= 35.233

The estimated bending die cost, assuming $40/h for die making, is = Cds + ( Mpo + Mpn) * 40 = $2397.92 = $2400 Cost of embossing die: Cds = $255, L = 80 mm = 8 cm, W = 26 mm = 2.6 cm, Mpx = 0.13 Nsp Mpo = 23 + 0.03 LW Mpc = 8 + 0.6 Pp + 3 Np

Therefore, Mpo = 23.624

Rectangular embossing Mpx = 4 *(0.13*3) = 1.56

Circular embossing Mpx = 2 * (0.13 * 1) = 0.26

Total Mpx = 1.82 Mpc = 8 + 0.6 * 7.8 + 3 * 6 = 30.68

Cost of embossing die is,

= Cds + ( Mpo + Mpc + Mpx) * 40 = $2500


22

Cost of progressive die: Cd = 2 Cid

Where Cid = 2495 + 2620 + 2400 + 2500 = $10015 Cd = $20030 Cycle time for each part: U = 90*103KN/m2 h = 1.02 mm = 1.02 * 10-3 m

Force for Blanking: Fblanking = 0.5UhLs

Where Ls = length to be sheared = 39.55 cm = 0.3955 m Fblanking = 18.15 KN

Force for Punching: Fpunching = 0.5UhLs

Where Ls = 210 mm = 0.21m Fpunching = 9.65 KN

Force for Embossing:

For one embossing Fembossing = UhLsSinθ = 5.06 since Ls = 0.078m Total Fembossing = 6 * 5.06 (As they are six embossing effects) = 30.38 KN

Force for Bending: Fbendung = 0.08UhLb

Where Lb = Length of bend = 26.225 cm = .26225 m


23

Fbendung = 1.92 KN

So, Total force required = Fblanking + Fpunching + Fembossing + Fbendung = 60 KN

From Table 9.3 The space required for 4 die stations is, 4*14.6 = 58.4

From Table 9.8 Appropriate press for 58.4 is 500 KN press force, $76/hr operating cost and

speed of 90 strokes/min.

The estimated cycle time per part is, t = 60/90 =0.67 sec

Processing cost per part is Cp = (0.67/3600)*76*100 = 1.4 cents. 2.4aiii For the remaining parts, the analysis is abbreviated: Staple slide:

Cost for progressive die = $9120 Cycle time = 0.6 sec Processing cost per part = Cp = 0.91 cents

Redesigned staple slide:

Cost for progressive die = $8500.00 Cycle time = 0.6 sec Processing cost per part = Cp = 0.91 cents

Anvil:

Cost for progressive die = $7590 Cycle time = 0.6 sec Processing cost per part = Cp = 0.91 cents


24

Redesigned Anvil:

Cost for progressive die = $7050 Cycle time = 0.6 sec

Processing cost per part = Cp = 0.91 cents Upper Arm:

Cost for progressive die = $22,220 Cycle time = 0.67 sec

Processing cost per part = Cp = 1.4 cents Redesigned Upper Arm:

Cost for progressive die = $22,060 Cycle time = 0.67 sec

Processing cost per part = Cp = 1.4 cents Unmodified parts: Upper leaf spring:


Bottom Staple Guide:


End Cap:



25

2.5 Assembly Paradigms

When designing for assembly, there are many varied considerations. As has been

the precedent, a brief discussion of the DFMA paradigms will be followed by application

of relevant paradigms to the Swingline 747 classic stapler. The object of design for

assembly is to provide the designers a tool for effective assembly considerations, to guide

the designers to simplicity, to provide information from experienced engineers early in

the process that will help less experienced designers, and to establish a database of

assembly times and cost factors. Most of the following information is taken from Product

DFMA, 2nd ed., hereafter referred to as PDFMA, by Boothroyd, Dewhurst, and Knight.

While there are tools and equations to be used for both manual and automated (robotic,

high-speed) assembly, the focus will remain on manual assembly since it is most

pertinent to the case at hand. Briefly, the main advantage for automation is the reduced

errors in assembly that lead to quality issues. The authors state, “… it is becoming widely

accepted that faulty assembly steps, rather than defective components, are more often the

reason for production quality problems.” For more information on automated assembly,

the interested reader is referred to the text. For manual assembly, there are several issues

to be considered.

2.5a Assembly Times and Efficiency

Assembly efficiency, also known as the DFA index, is vital to proper assembly

design. Two main factors that influence efficiency are the number of parts and the ease

of handling, inserting, and fastening those parts. To calculate the efficiency, Ema, the

following equation is given:

Ema = Nminta/tma

where Nmin is the theoretical minimum number of parts, ta is the basic assembly time for

one part, which is about 3 s, and tma is the estimated time to complete the assembly of the

entire product.

There are three time systems that can be used to estimate assembly times. One of

these, MOST, is used for very large parts which cannot be carried by workers. A lifting

device must be employed. Since this is beyond the scope of the example, it is not

discussed here. The other two systems, methods time measurement (MTM) and work


26

factor (WF) are useful. Both of these use part symmetry in their assessment of assembly

times. The symmetry of a part can be regarded about two axes; the insertion axis and any

axis perpendicular to insertion. The angle associated with the former is known as the

beta angle, the angle around the latter is alpha. These both have reference to the

maximum number of degrees by which a part that has been grasped needs to be rotated to

repeat its orientation. The total symmetry of a part is given by adding these two angles.

The MTM system uses the maximum possible orientation, given by 0.5β. The WF uses a

combination of both in the form β/α .

2.5b Guidelines for Manual Assembly

Handling and insertion/fastening are the two main areas of assembly. Some

design guidelines for handling and insertion/fastening are:

• Symmetrical design. • Prevent jamming. • Prevent tangling. • Avoid hazardous parts (sharps, slippery, etc). • Minimize resistance to insertion. • Standardize. • Employ pyramid assembly. • Part location prior to release. • Simplify fastening. • Avoid repositioning.

When dealing with these guidelines, it is safe to assume that not all may be able to be

incorporated simultaneously. The benefits and costs of each attribute must be weighed

against the over-all picture.

2.5c Effects of Weight and Dimensions

It is considered that a part whose thickness is less than 2mm will be difficult to

grasp and require the use of tweezers or other implement, thus adding to the assembly

time. The size of a part, which is the longest non-diagonal length, is also a factor. The

weight of a part is also a consideration, not only for assembly, but also for ergonomic

concerns. Generally, weight causes parts to be categorized as being able to be lifted with


27

one hand, two hands, two people, or by machine. Each of these has a different effect on

assembly time.

2.5d Chamfers

When dealing with insertion, chamfers will provide many benefits such as

reduced assembly time and incidents of jamming. Several parameters used to describe

attributes of both the pin and hole are listed in Table 5.

Table 5 – Insertion Parameters

The clearance c of the insertion is given by (D – d)/D and is dimensionless. PDFMA

presents the following conclusions regarding chamfer properties:

• For a given clearance, the insertion time for two different chamfer designs is constant.

• A chamfer on the peg is more effective than one on the hole. • The maximum effective chamfer width w is 0.1D. • The most effective conical chamfer design has chamfers on both hole and peg

with the widths equal to 0.1D and angles less than 45°. • Manual insertion time is not sensitive to angle changes from 10° to 50°. • For small c, round or conical chamfers can be more effective.

As the clearance decreases, the insertion time increases at various rates, depending on

whether there are chamfers on one or both parts involved or none. Another consideration

is when parts to be inserted jam. This is caused by one or more points of contact during

insertion. Different chamfer designs can alleviate this problem and reduce insertion time.

Insertion time can be estimated by the following equations:

D Diameter of hole. d Diameter of peg. L Length of insertion. w1 Width of peg

chamfer. w2 Width of hole

chamfer. θ1 Angle of peg

chamfer. θ2 Angle of hole

chamfer.


28

ti = 1.4L + 15 ms or

ti = -70 ln c + f(chamfers) + 3.7L + 0.75d ms

whichever is larger and where f(chamfers) = -100 (no chamfer) -220 (chamfer on hole) -250 (chamfer on peg) -370 (chamfer on both) 2.5e Miscellaneous Effects on Assembly Time

When designing parts to be assembled, obstructed views and access should be

considered. The effects of an obstructed view or obstructed access are that time for

assembly is increased and there is also a risk of harm to the worker. The inability to see

the parts can lead to fumbling, dropping or other time penalties, and obstruction may

force the worker to slow down, cause repeated small motions in awkward positions (i.e.

ulnar-deviated wrists while turning a wrench). The cost of time and ergonomics then

becomes an issue. Manual clamping also has a deleterious effect on time and has

ergonomic considerations. There are many parameters, born both empirically and by

experience, which bear consideration while designing for manual assembly. However,

the data presented are averages and therefore should not be taken to be cumulative. In

some cases, the times are overestimated, in others it is underestimated. Also, in the

situation where the assembly requires various different parts, care should be taken not to

accumulate times caused by different features. Only when large quantities of similar

parts are used should these results be consulted.

2.5f Further Guidelines

The minimum parts criteria also give the following guidelines:

• Avoid connections by placing parts to be connected at the same location. • Design so that assembly access is not restricted. • Avoid adjustments. • Use kinematic design principles to avoid over-constrained designs.

Also, for large assemblies with large numbers of parts, the differences in assembly time

generated by different parts will generally cancel each other out.


29

2.5g Assembly Layout

Depending on the size of the largest parts in an assembly, the layout of the assembly area

will differ. For small parts that can be placed within easy reach of the worker, the bench

or multi-station assembly methods are recommended (figs. 23 and 24). This layout

eliminates major body motion of the worker, reducing part retrieval time and cumulative

trauma disorders. For parts weighing more than 5 lbs but less than 30 lbs, or are longer

than 12 in. but less than 35 in., the modular assembly center is recommended (fig. 25).

There are three categories that determine which modular layout to use. These are based

upon the largest part being less than 15 in., between 15 and 25 in., and between 25 and 35

in. Larger parts will best be assembled in a custom assembly layout or a flexible

assembly layout (figs. 26 and 27). Other layouts do exist, such as on-site (i.e. for an

elevator), in clean rooms (microprocessors), modular assembly for very large parts

(automobiles), etc.

Figure 23 – Bench Station [4] Figure 24 – Multi-Station [4]

Figure 25 – Modular Station [4]


30

2.6 Assembly Methods – Stapler

Table 6 gives the alpha, beta, and handling times data for the various parts. This

data is derived from Tables 3.15 to 3.17 in PDFMA. A bench station assembly layout is

assumed.

Table 6 – Handling Times Data

No. Component or

Operation

Alpha Angle α

Beta Angle β

Symm. Angle

(α+β)

No. of

Items RP

Hand- ling

Time TH

Tool Acquire

Time TA

Inser- tion

Time TI

Time (s) TA+RP* (TH+TI)

Steps

1 Base 360 360 720 1 1.95 0 1.5 2.45 Place on Worksurface

2 Release Clip 360 360 720 1 3.34 0 3.0 6.34 Add

3 Lower Leaf Spring 360 360 720 1 2.25 2.9 2.6 7.75 Add Fasten

4 Anvil Actuator 360 0 360 1 1.13 2.9 2.6 6.63 Add Hold

5 Reorientation - - - 1 - - 4.5 4.5 Reorient

6 Anvil 360 180 540 1 2.36 2.9 2.6 7.86 Rivet

7 Set Aside - - - 1 - - 1.0 1.0 Special

8 Top Staple Guide 360 360 720 1 3.06 0 1.5 4.56 Place on Worksurface

9 Spring 180 0 180 1 2.25 0 5.2 7.45 Add

10 Staple Slide 360 360 720 1 2.73 0 1.5 4.23 Add

11 Bottom Staple Guide 360 360 720 1 3.06 0 1.5 4.56 Add

12 Upper Arm 360 360 720 1 1.95 2.9 4.5 9.35 Add

13 Set Aside - - - 1 - - 1.0 1.0 Special

14 Upper Cover 360 360 720 1 1.95 0 1.5 3.45 Place on Worksurface

15 Upper Leaf Spring 360 360 720 1 2.51 2.9 2.6 8.01 Add Fasten

16 Reorientation - - - 1 - - 4.5 4.5 Special

17 Pin 360 0 360 1 1.8 2.9 2.6 7.3 Add

18 Add Subassembly - - - 1 - - 4.5 4.5 Special

19 Spacer 360 180 540 1 2.36 0 1.8 4.16 Add

20 Plastic Cover 360 360 720 1 2.51 0 1.8 4.31 Add

21 Rubber Pad 360 360 720 1 1.95 0 3.0 4.95 Add

Figure 27 – Flexible Layout [4] Figure 26 – Custom Layout [4]


31

The total assembly time can therefore be derived from Table 6 to be 108.86 seconds.

2.6a Efficiency

Using Nmin = 19 (two fasteners), ta = 3 seconds, and tma = 108.86 seconds from

Table 6, the efficiency for assembling t he stapler is then 53%.

2.6b Chamfers The insertion of the pin and the anvil actuator are subjects for chamfer analysis.

We present the analysis for the pin only. Table 7 gives the chamfer dimensions for the

pin.

Table 7 – Insertion Parameters for the Pin

There is no chamfer around the insertion point. The pin has a rounded chamfer, therefore

no angle or chamfer width is given. From these data, we can calculate the clearance c

between the pin and the base to be 0.016 in. Since the clearance is so small, the pin uses

a rounded chamfer. The insertion time is 44.2 ms using ti = -70 ln c + f(chamfers) + 3.7L

+ 0.75d where f(chamfers) is -250. Despite the fact that insertion into the base, cover,

and subassemblies is progressive, we consider the diameters D to be the same and the

length L to be the entire width of the base along the insertion axis. As the pin is inserted

and parts through which it travels added, the stability of the pin increases. There is also

the draft on the base to consider. Since the clearance is such that the pin is inserted rather

easily, the draft need not be a concern.

2.7 Recommended Changes

A few changes in the manufacturing process led directly to changes in assembly.

For instance, if the spring is halved and the upper staple guide is redesigned, the spring

D 0.189

d 0.186 L 1.253

w2 0 θ2 0


32

no longer has to be threaded through the guide, saving on handling time. The time to set

the guide aside, insert the staple slide, and then later reacquire the guide is also reduced.

These have the effect of cutting the total assembly time from 108.86 to 97.86 and

increasing the efficiency from 53% to 58%. All other processes and methods were

believed to be adequate and therefore left unchanged.

3 Discussions

Due to numerical analyses performed on changes that were suggested, it was

determined that the overall design of the 747 stapler is adequate. The manufacturing cost

savings of $3650.00 for re-tooling, die costs, etc. and the assembly time savings of only

11 seconds do not justify implementation of those changes. For example, the time

savings only yields a 6-cent per unit saving. One such manufacturing change that DFM

suggested was to change the anvil manufacture method from blanking to cut off. This

would result in a savings in cost through die, reduced scrap, and cycle time. However,

DFA showed that it should not be implemented due to the sharp corners that would be a

safety issue both in the assembly and daily use of the product. Also, strength analysis

revealed residual stresses at the corners. Another change implemented was to create a

two-part foot pad. DFM recommended this change based on saving in time, cost and die

manufacture and reduced cycle time. Again, DFA showed this change to be unwarranted.

A basic principle of DFA was violated; reduce part numbers.

Thought was given into changing the materials in the manufacture of the stapler.

The DFM material selection analyses run according to Boothroyd-Dewhurst [4] revealed

that the material selected were already DFM compliant. However, consideration was

given to the use of plastics, particularly for the cover and the base. These changes were

ultimately rejected due to durability factors, cyclic loads, and severe impact safety factors.

Also, Swingline® makes different models made with plastic. Had the recommendations

to change the 747 to plastic been implemented, there would have been a reduction in the

variety offered to the consumer.


33

4 Conclusions

In general, a strict application of DFMA paradigms may give rise to contradictory

recommended changes in the design of a project. For the Swingline® 747 desktop stapler

such contradictions were evident. Some recommendations can also be made which are

wholly unsuitable for the task at hand. In any case, applying DFMA can and does reduce,

at least in part, the costs associated with the bringing to market of a product. Those costs

can be associated with manufacture, assembly, material selection, etc. or any combination

of these.

With regards to the stapler at hand, the overall results of our DFMA application

yielded some worthwhile recommendations. Five parts were redesigned from a

manufacture point of view which reduced the time and cost of manufacture. An added

bonus to those changes was a time and cost saving at the assembly stage. However, most

of the components, from the point of view of both material selection and manufacture,

and of assumed assembly methods of the stapler, proved to be very acceptable. It is, after

all, the Swingline® Classic™ stapler.

34

NOTE: The best and the worst materials obtained after running the DFMA

analysis for all the parts are represented by bold characters in the

Tables.

Part 1. Rubber Base.

No analysis was run. It could be recommended that the rubber base be

eliminated and instead have two foot pads at each one of the ends. This would in

turn save money which otherwise would be needed for the molding of rubber

base. This also reduces assembly time.

Fig A -1 Base Fig A-2 Alternate

The figures seen above are the two different designs discussed previously. Part 2: Release Clip:

The release clip is made of aluminum alloy.

Analysis Run for Strongest Beam and Max Performance, Their Respective Index

Values:

Gray cast iron 21 Ductile iron 43 Malleable iron 30 Mild steel 16 Alloy steel 100 Stainless steel 13 Aluminum alloy 0 Beryllium copper 88

APPENDIX A

35

Copper, hard 24

Analysis Run for Strongest Beam and Minimum Weight, Their Respective Index

Values:

Gray cast iron 20 Ductile iron 44 Malleable iron 26 Mild steel 7 Alloy steel 93 Stainless steel 0 Aluminum alloy 100 Beryllium copper 76 Copper, hard 0

Analysis Run for Strongest Beam and Minimum Cost, Their Respective Index

Values:


Part 3: Lower Leaf Spring:

The lower leaf spring is made of alloy steel.

Analysis Run for Best Diaphragm Spring and Max Performance, Their

Respective Index Values:

Gray cast iron 23 Ductile iron 39 Malleable iron 26 Mild steel 0 Alloy steel 95

36

Stainless steel 0 Aluminum alloy 24 Beryllium copper 100 Copper, hard 32

Analysis Run for Best Diaphragm Spring and Minimum Weight , Their Respective

Index Values:


Analysis Run for Best Diaphragm Spring and Minimum Cost, Their Respective

Index Values:


Part 4: Anvil:

The anvi l is made of alloy steel.


Values:

Gray cast iron 21 Ductile iron 43

37

Malleable iron 30 Mild steel 16 Alloy steel 100 Stainless steel 13 Aluminum alloy 0 Beryllium copper 88 Copper, hard 24


Values: Gray cast iron 20 Ductile iron 44 Malleable iron 26 Mild steel 7 Alloy steel 93 Stainless steel 0 Aluminum alloy 100 Beryllium copper 76 Copper, hard 0


Values:


Part 5: Base:

The Base is made of aluminum alloy.

38


Values:



Values:



Values:


39

Part 6: Anvil Actuator:

The anvil actuator is made of aluminum alloy.


Values:



Values:



Values:

Gray cast iron 94 Ductile iron 100 Malleable iron 88 Mild steel 58

40

Alloy steel 54 Stainless steel 30 Aluminum alloy 34 Beryllium copper 0 Copper, hard 32

Part 7: Spacer:

Remarks:

Made of plastic. No analysis was run for the spacer.

Part 8: Spring:

The spring is made of alloy steel (spring steel).

Analysis Run for Best Coil Spring and Max Performance, Their Respective Index

Values:


Analysis Run for Best Coil Spring and Minimum Weight, Their Respective Index

Values:

Gray cast iron 24 Ductile iron 43 Malleable iron 28 Mild steel 2 Alloy steel 100 Stainless steel 0

41

Aluminum alloy 46 Beryllium copper 99 Copper, hard 25

Analysis Run for Best Coil Spring and Minimum Cost, Their Respective Index

Values:


Part 9: Pin:

The pin is made of alloy steel.


Values:



Values:

Gray cast iron 20 Ductile iron 44

42

Malleable iron 26 Mild steel 7 Alloy steel 93 Stainless steel 0 Aluminum alloy 100 Beryllium copper 76 Copper, hard 0


Values:


Part 10: Staple Slide:

The staple slide is made of alloy steel.

Analysis Run for Strongest Compression Member and Max Performance, Their



43

Analysis Run for Strongest Compression Member and Minimum Weight, Their



Analysis Run for Strongest Compression Member and Minimum Cost, Their



Part 11: Bottom Staple Guide:

The staple bottom guide is made of aluminum alloy. No analysis was carried out

for the bottom s taple guide.

Part 12: Upper Arm:

The upper arm is made of alloy steel.

44


Values:



Values:



Values:


45

Part 13: Top Staple Guide:

The top staple guide is made of aluminum alloy. No analysis carried out for the

top staple guide.

Part 14: The End Cap (747):

The end cap is made of alloy steel.

Analysis Run for Strongest Beam Max Performance, Their Respective Index

Values:



Values:


46


Values:


Part 15: Upper Leaf Spring:

The upper leaf spring is made of alloy steel.

Analysis Run for Best Diaphragm Spring and Max Performance, Their



Analysis Run for Best Diaphragm Spring and Minimum Weight , Their Respective

Index Values:

Gray cast iron 28 Ductile iron 44 Malleable iron 29 Mild steel 2 Alloy steel 97

47

Stainless steel 0 Aluminum alloy 65 Beryllium copper 100 Copper, hard 28

Analysis Run for Best Diaphragm Spring and Minimum Cost, Their Respective Index Values: Gray cast iron 93 Ductile iron 100 Malleable iron 82 Mild steel 34 Alloy steel 54 Stainless steel 1 Aluminum alloy 33 Beryllium copper 0 Copper, hard 22

Part 16: Upper Cover:

The upper cover is made of aluminum alloy.


Values:


48


Values:



Values: Gray cast iron 100 Ductile iron 100 Malleable iron 92 Mild steel 68 Alloy steel 45 Stainless steel 44 Aluminum alloy 50 Beryllium copper 0 Copper, hard 43

Part 17. Plastic Cap.

Remarks: Made of plastic. No analysis was run for the plastic cap.

49

Manufacturing Process

The appendix C is meant to illustrate the various Manufacturing steps involved in

the making of the Upper Arm. At attempt using Pro – E to show the various steps

has been made.

Step 1

The first step would be to blank the outline of the part and then pierce out the

holes in the part. The assumption in making this part is to use a progressive die.

APPENDIX B

50

Step 2 The 2nd step as seen in the above figure is to bring in the initial bends to as

indicated by the circles.

Step 3 Finally in step 3 we bring in the side bends which gives us the final shape of the

part.

We have similarly simulated the manufacturing processes of all the parts.

However the Pro-E drawings were made only for a few parts.

51

The Pro-E part sketches of following parts have been attached. The parts being,

Sl No Part Name 1 Lower leaf Spring 2 Base 3 Spacer 4 Staple Slide ( Old Design) 5 Staple Slide ( New Design) 6 Bottom Staple Guide 7 Upper Arm ( Old Design) 8 Upper Arm ( New Design) 9 Upper Staple Guide (Old Design) 10 Upper Staple Guide (New Design) 11 End Cap 12 Upper Leaf Spring 13 Upper Cover 14 Plastic Cap

Note: The Pro-E drawings for the parts mentioned in the above table have been attached.

APPENDIX C

1. www.swingline.com

2. www.page.sannet.ne.jp/ gaho1300/proe/ practical_guide /hd90013/index_hd90013.html

3. www.materials.eng.com.ac.uk/mpsite

4. Boothroyd, G., 1988, Dewhurst, P., Product Design for Manufacture and Assembly.

5. http://www-ec.njit.edu/~das/1-1-2.html

6. http://www.tm.tue.nl/race/ce/dfma_2.html

7. A. U. Alvi and A. W. Labib, ‘Selecting Next-generation Manufacturing Paradigms - An Analytic Hierarchy Process-based Criticality Analysis’ Proc Instn Mech Engrs Vol 215 Part B , 2001 Pg. 1773-1786

8. Tomiyama, T. A manufacturing paradigm towards the 21st century. Integrated Computer Aided Engg, 1997, 4, 159-178.

9. http://www.dfma.com/news/dfmcost_news.html

10. Stoll, H.W., 1986, Design for Manufacture: An overview 11. http://www.scs.unr.edu/mecheng/me151/dfm/sld005.htm

References

dfma stapler

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