GE 101 Final Design Project:

Transcription

1 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

2 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 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 ii

3 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 iii

4 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 iv

5 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. 1

6 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 2

7 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. 3

8 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. 4

9 Pencil Casing Nose Push Button Eraser Compartment which contains Eraser Clip Holder, Eraser Clip, Eraser Clip Holder Cap and the Eraser 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 5

10 pinch the prongs that connect the Eraser Clip Holder and the Eraser Compartment and separate them. Eraser Compartment Eraser Clip Holder Cap Eraser Eraser Clip Holder Eraser Clip Figure 4. The Eraser Section broken up into its sub components 6

11 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 Nose Tip Holder Tip Figure 6. The Nose Section broken down into its subcomponents 7

12 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. Pencil Casing Mechanical Compartment 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. Spring Housing Ring Chuck Lead Dispenser Spring 8

13 Figure 8. The Mechanical Compartment broken into its sub components 9

14 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 10

15 Figure 10. Clear Point on gradient shaded non reflective surface. Figure 11. Top profile View 11

16 Figure 12. Side Profile View Figure 13. Steep perspective view 12

17 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 13

18 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 Body Section Nose Section Part # Part Name Function when button is pushed Function when button released 1 Pencil Casing Protects internal parts Protects internal parts 2 Push button Displaces parts to dispense None pencil lead 6 Mechanical Rotates to push lead None Compartment forward 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 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 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 Eraser Section 7 Eraser Compartment Provides eraser clip with grooves to follow up and down 8 Eraser Clip Holds Eraser 9 Eraser Clip holder Twist to extrude eraser Cap 10 Eraser Clip Holder Holds eraser clip to eraser compartment 11 Eraser To erase markings on paper 14

19 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 Part # Part Name Manufacturing Process Material Estimated Weight (g) 1 Pencil Casing Blow molding Plastic Push button Injection Molding Plastic Nose Case Rotational Molding Plastic Tip Cold rolling Aluminum.076 alloy 5 Tip holder Injection Molding Plastic Mechanical Injection Molding Plastic.852 Compartment 7 Eraser Injection molding Plastic Compartment 8 Eraser Clip Injection molding Plastic Eraser Clip Rotational plastic.236 Holder Cap 10 Eraser Clip Rotational Plastic.596 Holder 11 Eraser Injection molding Vinyl Metal Ring Cold rolling Copper Spring Housing Blow molding Plastic Spring Cold winding Aluminum alloy.009 Table 4. Weight Estimate Comparison Total Weight Total Weight-Scale Estimate- Inventor 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 15

20 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 holeshaft 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. 16

21 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 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 19 th century that a model that was recognizable as a modern mechanical pencil finally emerged. This design was patented by Sampson Mordan in 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. 17

22 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 18

23 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: uct/product_detail.jhtml?attributeid=snatt40030&_dargs=/sanford/ consumer/papermate/nav/leftnavbrand.jhtml [2] Information and graphics for the Relative Maturity section found at: 19