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GE 101 Final Design Project:
Clear Point
Mechanical Pencil
Presented and Submitted on: Monday May 8, 2009
Sarah Fullmer
David Montiel
Wonseok Oh
Ryan Smith
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Table of Contents Table of Contents .......................................................................................................................... ii List of Tables ............................................................................................................................... iii List of Figures............................................................................................................................... iv Introduction....................................................................................................................................1
Product Description .............................................................................................................1 Black Box Diagram..............................................................................................................2 Market Segment ...................................................................................................................2
Product Documentation.................................................................................................................4 Preliminary Dissection.........................................................................................................4 Eraser Section ......................................................................................................................5 Nose Section ........................................................................................................................6 Main Body Section ..............................................................................................................7
3-D Modeling ..................................................................................................................................8 Product Analysis ..........................................................................................................................11
Functional Decomposition Analysis ..................................................................................11 Additional Analysis ...........................................................................................................13
Digital Prototyping.......................................................................................................................14 Product Improvement .................................................................................................................15
Relative Maturity ...............................................................................................................15 Improvement Ideas.............................................................................................................15
Conclusion ....................................................................................................................................16 Bibliography .................................................................................................................................17 Appendix A .......................................................................................................................attached
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List of Tables
Table 1 Summary of functions for components in the Body Section and Nose Section 12
Table 2 Summary of functions for components in the Eraser Section 12 Table 3 Summary of Component Material Type, Estimate Weight
and Manufacturing Process 13 Table 4 Weight Estimate Comparison 13
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List of Figures Figure 1 Clear Point Mechanical Pencil 1 Figure 2 Black Box Diagram 2 Figure 3 The Clear Point pencil broken up into its primary sections 4 Figure 4 The Eraser Section broken up into its sub-components 5 Figure 5 The Whole Nose Section 6 Figure 6 The Nose Section broken down into its subcomponents 6 Figure 7 The Main Body Section broken into its primary components 7 Figure 8 The Mechanical Compartment broken into its subcomponents 7 Figure 9 Clear Point on black reflective surface 8 Figure 10 Clear Point on gradient shaded non-reflective surface 9 Figure 11 Top profile View 9 Figure 12 Side Profile View 10 Figure 13 Steep perspective view 10 Figure 14 Functional Decomposition Diagram 11 Figure 15 Conrad Gesner’s illustration of his pencil from 1567 15
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Introduction
Product Description
This product is the Clear Point model mechanical pencil, manufactured by Paper Mate. It
provides the user with a continually sharp graphite pencil lead and an eraser. It is composed of
13 parts.. Figure 1 displays the whole product:
Figure 1. Clear Point Mechanical Pencil [1]
The pencil lead is extruded when the user pushes a button on the side of the main shaft,
which can be seen in Figure 1. When pressed, the button performs several actions. First, it
applies pressure to a shaft inside the pencil, which moves forward towards the nose. The shaft is
made up of two parts: an inner and outer shaft. The button applies pressure to the inner shaft
while the outer shaft is held stationary by a ring at the nose of the pencil. This allows the inner
shaft to advance itself further towards the nose, relative the stationary outer shaft. In this way,
the lead is pushed forward by the inner shaft.
At the same time, another ring at the nose is opened, permitting the lead to be propelled
forward by the moving inner shaft. Once one releases the button, the ring closes, holding the lead
in place as the inner shaft retracts. A spring is connected to both the inner and outer shaft, which
forces the shaft back to its original position after the button as been release.
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Black Box Diagram The following black-box diagram illustrates the two principle functions of the Clear Point
Mechanical, in terms of input and output:
Figure 2. Black Box Diagram
Market Segment
This pencil belongs to the office supply market segment and competes with other writing
utensils that provide similar functionality. The design is driven by the customer's need for an
inexpensive pencil that provides:
- a continually sharp lead
- ability to erase work
- ability replenish lead supply
- consistent line width
- easy grip
Consumers with these needs include students, teachers, engineers, architects, office
workers, writers, etc. The product’s primary competitors are other mechanical pencil models.
These include other models produced by both Paper Mate as well as models manufactured by
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other writing utensil manufacturers, such as Bic, Pentel, the Autopoint Company, etc. It should
be noted that manufacturers which produce exclusively pens are not competitors because there
are many applications for which a pencil cannot be replaced by a pen. This includes any activity
where the ability to erase is crucial, such as drafting.
The Clear Point model has two unique features. First, the user pushes a button to compel
the lead through the nose. The button is located in the middle of the pencil, in the longitudinal
direction, where it can be accessed with a shift of the writing hand's finger. Most other
mechanical pencils have the user push the back end, where the eraser is located, to extrude the
lead. The eraser is the pencil's second unique feature. By twisting a ring, the eraser is brought out
in a corkscrew motion. Many competitor models utilize a stationary eraser that comes in a
smaller amount, whereas this model's mobile eraser is longer.
The lead button, located in the middle of the pencil, allows the consumer more ease of
use. It permits the user to employ only one hand to extrude the lead. In contrast, competitor
pencils require the consumer to use either two hands or else a thumb and extra movement. Also,
because of its longer eraser, the consumer need purchase fewer additional erasers. In addition,
there is a grip which allows for less stress on the fingers. In conclusion, regular pencils have
three downsides when compared to this pencil: the eraser is stationary, the lead must be extruded
with an extra action, and there is no grip.
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Product Documentation
Preliminary Dissection
The dissection process began by breaking the pencil into three major sections. First, the
eraser compartment was separated from the pencil casing. The eraser compartment contains the
Eraser Clip Holder, Eraser Clip Holder Cap, Eraser Clip, and the Eraser. About a half of the
Eraser Compartment fits inside the Pencil Casing, and there is a ridge within the Pencil Casing
that allows the Eraser Compartment to fit snugly. This provided some resistance when they were
pulled apart. After separating the Eraser Compartment, the Nose was unscrewed from the Pencil
Casing. Next, the Push Button was dethatched. This was done by pulling up on the end free to
rotate. The sides of the Push Button are slanted slightly outwards such an outside force, applied
perpendicular to the longitudinal direction the main casing is required to remove it.
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Figure 3. The Clear Point pencil broken up into its primary sections
After separating the three major sections—the Eraser Section, Main Body Section and
Nose Section- each section was examined in detail.
Eraser Section
The Eraser Section contains the Eraser Compartment and another cylindrical tube entitled
the Eraser Clip Holder (ECH). This is attached at the bottom of the Eraser Compartment by two
prongs that extend down from the base of the ECH and fit into a hole at the bottom of the Eraser
Compartment. The ECH holds the Eraser Clip at different heights. To dissect the Eraser
Section, the Eraser was pulled out from the Eraser Compartment, which was being held on by the
Eraser Clip. Next, the ECH was turned until the Eraser Clip moved to the very top. At this
point, pliers were used to pinch the Eraser Clip and pull it out. Then, the pliers were used to
Eraser Compartment which contains Eraser Clip Holder,
Eraser Clip, Eraser Clip Holder Cap and the Eraser
Push Button
Nose
Pencil Casing
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pinch the prongs that connect the Eraser Clip Holder and the Eraser Compartment and separate
them.
Figure 4. The Eraser Section broken up into its subcomponents
Eraser Compartment
Eraser Clip Holder
Eraser Clip Holder Cap
Eraser
Eraser Clip
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Nose Section Following the dissection of the Eraser Section, all parts enclosed inside the Nose Section were
broken apart. The tip of another pencil was used to push out the Tip and Tip Holder. These two
parts are combined inside the nose and work together with the Tip Holder by having a snug fit
with the Nose. Once the Tip/Tip Holder assembly was extracted, it was possible to pull them
apart.
Figure 5. The Whole Nose Section
Figure 6. The Nose Section broken down into its subcomponents
Tip
Tip Holder Nose
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Main Body Section Finally, the Main Body Section was dissected. A hex saw was used to cut the Pencil Casing, to
give access to the Mechanical Compartment. Figure 6 illustrates this.
Figure 7. The Main Body section broken into its primary components
As seen in Figure 7 below, The Mechanical Compartment contains the Spring, Spring Housing,
Lead Dispenser, Chuck, and Ring. After extracting the Mechanical Compartment from the
Pencil Casing, the Ring was cut off with pliers. The Ring was the only piece applying pressure
to the Spring, which was then easily removed from the Spring Housing. This exposed the Lead
Dispenser, which is 3 flaps oriented in a circular pattern. The lead passes through there, leading
to the Nose.
Mechanical Compartment
Pencil Casing
Ring Spring Housing
Spring Lead Dispenser
Chuck
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Figure 8. The Mechanical Compartment broken into its subcomponents
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3D Modeling The Clear Point pencil was modeled in the Inventor design program and rendered
pictures of the assembled product were created. The following rendered images display the Clear
Point pencil from different angles and in different lighting to convey a sense of the whole
product.
Figure 9. Clear Point on black reflective surface
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Figure 10. Clear Point on gradient shaded nonreflective surface.
Figure 11. Top profile View
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Figure 12. Side Profile View
Figure 13. Steep perspective view
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Product Analysis
Functional Decomposition Analysis The following figure graphically illustrates Clear Point’s 14 component parts broken down by
their location.
Figure 14. Functional Decomposition Diagram
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Each of the 15 individual components belongs to one of the three main sections: the Body
Section, Nose Section, or Eraser Section. The Body Section is further divided into inner and
outer components. The components in the Body Section and Nose Section perform different
functions depending on whether the Push Button is engaged or not. The following table describes
each component function in both modes:
Table 1. Summary of functions for components in the Body Section and Nose Section Main Section
Part # Part Name Function when button is pushed
Function when button released
1 Pencil Casing Protects internal parts Protects internal parts2 Push button Displaces parts to dispense
pencil lead None
6 Mechanical Compartment
Rotates to push lead forward
None
12 Metal Ring Pulled back to open prongs of lead dispenser
Keeps prongs of lead dispenser in place
13 Spring Compresses to allow the lead dispenser to open
Closes the lead dispenser
Body Section
14 Spring Housing Keeps spring in place Keeps spring in place 3 Nose Case Protects tip Protects tip 4 Tip holder Keeps tip in place Keeps tip in place
Nose Section
5 Tip Guides lead out of pencil Protects lead
The functionality of the components in the Eraser Section are not affected by the Push Button.
The following table describes the function of the components in the Eraser Section:
Table 2. Summary of functions for components in the Eraser Section
Location Part # Part Name Function 7 Eraser
Compartment Provides eraser clip with grooves to follow up and down
8 Eraser Clip Holds Eraser 9 Eraser Clip holder
Cap Twist to extrude eraser
10 Eraser Clip Holder Holds eraser clip to eraser compartment
Eraser Section
11 Eraser To erase markings on paper
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Additional Analysis Each of the 14 components are produced with manufacturing techniques chosen based on the
component material as well as the part geometry. The following table summarizes the material
type, estimated weight and manufacturing process for each part. The estimated weight of each
part was determined using the Inventor modeling program.
Table 3. Summary of Component Material Type, Weight and Manufacturing Process
Table 4. Weight Estimate Comparison
Total Weight Estimate- Inventor
Total Weight-Scale
9.167 g 12 g
The total weight of the product, 12 grams, was determined using the scale provided in the
Product Dissection Lab. This scale rounded all measurements to grams, so it was not possible to
Part #
Part Name Manufacturing Process
Material Estimated Weight (g)
1 Pencil Casing Blow molding Plastic 3.634 2 Push button Injection Molding Plastic .356 3 Nose Case Rotational Molding Plastic .527 4 Tip Cold rolling Aluminum
alloy .076
5 Tip holder Injection Molding Plastic .027 6 Mechanical
Compartment Injection Molding Plastic .852
7 Eraser Compartment
Injection molding Plastic 1.348
8 Eraser Clip Injection molding Plastic .086 9 Eraser Clip
Holder Cap Rotational plastic .236
10 Eraser Clip Holder
Rotational Plastic .596
11 Eraser Injection molding Vinyl 1.002 12 Metal Ring Cold rolling Copper .254 13 Spring Housing Blow molding Plastic .164 14 Spring Cold winding Aluminum
alloy .009
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obtain sufficiently precise weight measurements for individual parts. The majority of the part
weights rounded to zero. Nonetheless, the total weight of all the parts placed on the scale should
be close to the total weight estimate found in Inventor. There is a 25% relative error between the
estimated and actual product weight. This large difference may be accounted for in several ways.
First, the individual parts may have been inaccurately measured and so their model dimensions
are incorrect. Next, the wrong material type and hence material density may have been chosen.
Finally, the actual scale may be at fault since it did not given consistent weight readings.
A tolerance analysis was performed on the parts using the Inventor design program. The
results of this analysis can be found in Appendix A on drawing sheets 7, 8, 12 and 13. The parts
on sheets 7 and 8 are a hole-shaft combination. These parts are interference fit and the tolerance
is indicated as both basic hole and basic shaft. The parts on sheets 12 and 13 also depict a hole-
shaft combinations. The 12 and 13 numbered drawings have a clearance fit and the tolerances are
indicated as basic shaft.
Digital Prototyping Several part prototypes were created using a 3D printer. However, because the printer
was not able to produce parts of a sufficiently small size, the prototypes are not their true size.
Instead, they are scaled up by a factor of two.
The parts that were prototyped came from the Eraser Section of Clear Point pencil. These
parts were the Eraser Compartment, Eraser Clip, Eraser Clip Holder, Eraser Clip Holder Cap and
Eraser. The functionality of this section is seen when one rotates the Eraser Clip Holder Cap.
When rotating clockwise, this extrudes the eraser; counterclockwise rotation retracts it.
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Product Improvement
Relative Maturity [2]
The original pencils were known as “lead holders” and consisted of a hollow tube
containing a length of lead. Such a design was first documented by the Swiss naturalist Conrad
Gesner in 1567. Figure x below presents an illustration of such a pencil.
Figure 15. Conrad Gesner’s illustration of his pencil from 1567 [2]
Since then, the evolution of the mechanical and the wooden pencil have diverged. It was
not until the 19th century that a model that was recognizable as a modern mechanical pencil
finally emerged. This design was patented by Sampson Mordan in 1822. His pencil employed a
propelling mechanism and used a thin ~1 mm lead.
Improvement Ideas
The Clear Point mechanical pencil model could be improved by reducing the complexity
of the Eraser Compartment. The clip attached to the outside of the Eraser Compartment is not
necessary and frequently breaks off. Eliminating this aspect of the Eraser Compartment would
reduce the part’s complexity, thereby increasing both the ease of manufacture and ease of use.
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Additionally, mechanical compartment does not grip down on lead enough to hold the
lead in place all the time. When the user pushed down on the pencil over the course of writing,
the lead retreats back up into the pencil. The product would be much improved by increasing the
grip of the Mechanical Compartment on the lead, perhaps by introducing an additional source of
friction or shear stress.
Conclusion Reverse engineering this product was made difficult by its small size. First, it was hard to
measure dimensions with sufficient degree of precision. This challenge was overcome by the use
of high-precision calipers instead of rulers of scales. Additionally, the same dimension was
measured several times and then those values were averaged to establish a final baseline
dimension. The small size also made tolerance analysis difficult. This was overcome by using the
Inventor design program to perform a tolerance analysis on the modeled parts. Finally, it was not
possible to manufacture 3D parts in their true size, once again because of the smallness of each
part. Instead, models scaled to twice the size of the original parts were produced.
Mechanical pencils have been manufactured and used for hundreds of years. The Clear
Point model, by Paper Mate, does not differ significantly from other models made today or those
of a hundred years ago. However, it does have a several features which are combined in a unique
way. The push button on the side combined with the rotating eraser, sets the Clear Point pencil
apart.
Due to their age and wide application, mechanical pencils are already used all over the
world. There are no additional markets to be found for the Clear Point pencil. To increase the
number of Clear Point pencil’s sold, it is a matter of competing with other models within
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existing markets. The Clear Point is given a competitive edge by its side push button, which is
preferable from an ergonomic perspective to a button on the eraser. Additionally, the rotating
eraser allows for a longer eraser to be stored than is possible in non-rotating models. Finally, the
changing diameter of outer casing creates an ergonomic grip for the user, which makes the Clear
Point model preferable over single-diameter models.
Bibliography [1] Image found at:
http://www.papermate.com/sanford/consumer/papermate/jhtml/product/product_detail.jhtml?attributeId=SNATT40030&_DARGS=/sanford/consumer/papermate/nav/leftnavbrand.jhtml
[2] Information and graphics for the Relative Maturity section found at: http://www.leadholder.com/main-history.html