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
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DFMA as Applied to the Swingline® 747 Desktop Stapler.
Department of Mechanical Engineering, The University Of Utah, Salt Lake City, Utah.
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)
DFMA as Applied to the Swingline® 747 Desktop Stapler
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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
DFMA as Applied to the Swingline® 747 Desktop Stapler
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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.
DFMA as Applied to the Swingline® 747 Desktop Stapler
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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
DFMA as Applied to the Swingline® 747 Desktop Stapler
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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.
DFMA as Applied to the Swingline® 747 Desktop Stapler
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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.
DFMA as Applied to the Swingline® 747 Desktop Stapler
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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
DFMA as Applied to the Swingline® 747 Desktop Stapler
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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
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
DFMA as Applied to the Swingline® 747 Desktop Stapler
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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
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
DFMA as Applied to the Swingline® 747 Desktop Stapler
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= 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
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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
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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
DFMA as Applied to the Swingline® 747 Desktop Stapler
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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:
Cost for progressive die = $9760.00 Cycle time = 0.6 sec Processing cost per part = Cp = 0.91 cents
Bottom Staple Guide:
Cost for progressive die = $9130.00 Cycle time = 0.6 sec Processing cost per part = Cp = 0.91 cents
End Cap:
Cost for progressive die = $5250.00 Cycle time = 0.6 sec Processing cost per part = Cp = 0.91 cents
DFMA as Applied to the Swingline® 747 Desktop Stapler
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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
DFMA as Applied to the Swingline® 747 Desktop Stapler
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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
DFMA as Applied to the Swingline® 747 Desktop Stapler
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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.
DFMA as Applied to the Swingline® 747 Desktop Stapler
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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.
DFMA as Applied to the Swingline® 747 Desktop Stapler
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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
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.
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 Copper, hard 24
48
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: 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.
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