PAN: The Mechanical Aluminum Can Crusher
... of affordability. The First Prototype: Hydraulic Can Crusher (Car Jack Design) Design A hydraulic design was used on the first prototype to take advantage of the pressure created by the hydraulic press, as shown in Figure 3 (page 8). This design also proved to have advantages over the pneumatic designs of PeBBles and Bam-Bam such as portability and costs, taking into consideration the major components of PeBBles and BamBam (namely the large air compressor and circuitries involved) compared to the one thousand five hundred peso (P 1,500.00) cost of the first prototype wholly. The prototype was given a qualitative assessment based on its performance including the reaction of its users. Heights of cans crushed with this prototype were also measured (it was found out that crushed can height is approximately equal to twenty millimeters). The prototype proved to have many disadvantages. Instead of improving on the hydraulic design, the group decided to shift to a mechanical design in order not to complicate costs. Figure 2. Illustration of Hydraulic Press based Can Crusher Design Figure 3. Hydraulic Jack based Can Crusher Design Manufacturing The first prototype was manufactured by Eurocomp Machine Shop located at Tandang Sora Avenue, Old Balara, Quezon City, headed by Mr. Dondie Brazil, and was supervised by the group. The major components were tension post rods, tension plates, nuts, the hydraulic jack, and the hydraulic jack platform base. The construction of the first prototype took two weeks. The Second Prototype: Mechanical Can Crusher Design The second prototype is a mechanical design (Figure 5, see page 10 for the internal and external images). The objective of using a simple mechanical system is that it costs less than pneumatic and hydraulic designs (i.e. PeBBles, Bam-Bam and an improved design of the first prototype). The mechanical design requires a lever and mechanical joints that would lessen the force needed to crush the can. The final appearance of the project involves the placing of the major internal components, can entry and crushing area, the output area, and the casing. Manufacturing The second prototype was also manufactured by Eurocomp. The major components were made of galvanized iron, screws for the joints in the internal mechanical system, and an angle steel frame. The construction of Pan took three weeks. Testing The user-force test was performed in order to compare the force required to crush cans with Pan with that required in the manual method (stepping into the can). The forces were determined by getting the difference between the initial weight reading in the weighing scale (due to the mass of the crusher in determining the force required using Pan, and due to the mass of the can in determining the force required in manual method), and the maximum reading observed after applying force and crushing the can. Ten replicates for the two experiments were used, and the mean force for each Figure 4. Internal and External Images of Mechanical Can Crusher Design experiment was obtained for comparison. Together with this quantitative analysis, crushing cans with Pan and the crusher itself was also evaluated descriptively or qualitatively. A one-man consistency test was then performed, wherein only one user crushed 100 aluminum softdrink cans consecutively using Pan. A second test called the random consistency test was also performed, wherein fifty random people from the Philippine Science High School – Diliman Campus environment were asked to crush a can. For control purposes, the cans used were whole, cylindrical, free from large dents, having an average height of 11.5 cm, and manufactured only by Coca-Cola Bottlers’ Philippines, Inc. The heights of the crushed cans from these tests were then obtained. The mean height of crushed cans and variance from the data obtained from both tests were computed. Variance is a measure of variability that shows how scattered or deviated are the data from each other. For control purposes, the cans used were whole, cylindrical, free from large dents, having an average height of 11.5 cm, and manufactured only by Coca-Cola Bottlers’ Philippines, Inc. Results and Discussion Discussion of Designs The first design that the group planned to create and came up with was a hydraulic design. Figure 2 on page 7 shows the first hydraulic design that the group visualized and created. The concept of hydraulic presses, such as those used in car lifts and car breaks, were utilized in the first can crusher design because the system produces a larger amount of force from a smaller force that is initially applied, thus the can could be crushed using a smaller amount of force when utilized with hydraulic press design. The first hydraulic design, however, was not as simple as it seemed. A mechanical engineer evaluated and it was found out that there were still several parts that were necessary for the hydraulic design to work, such as check valves and an oil control ring for controlling the liquid inside the hydraulic system. It was also estimated that the cost of creating the design with all the necessary parts would be approximately ten thousand pesos (P 10,000.00). The dimensions of the first design would also increase to give way for the necessary parts, therefore increasing the size of the can crusher. The hydraulic can crusher would also be difficult to manage because of the possible oil leakage and other problems concerning the maintenance of the liquid inside the system. Lastly, the engineer could not assure the group that the design would work because the person who will use the can crusher might have a difficult time pushing or exerting force on the piston or the assumed force produced might not be enough. It would probably take more than three prototypes for the hydraulic design to work, and this would further increase the cost. Because of this, it was recommended to incorporate a car jack into a new can crusher design. A car jack is a simple hydraulic system. It is commonly used in lifting cars for repair purposes because of the very strong force it can exert constantly for a long time. Figure 3 on page 8 shows the “car jack” crusher, and this is the first prototype fabricated by the group. The car jack based can crusher design is smaller than the hydraulic press design. The manufacturing cost of this crusher is one thousand five hundred pesos (P 1,500.00), which is smaller than the cost involved in manufacturing the hydraulic press design. The height of cans crushed with the hydraulic jack can crusher is approximately twenty millimeters, which is about eighty percent (80%) less than the original can height of 11.5 centimeters or one hundred fifteen (115) millimeters: 100% - [ (20 mm / 115 mm) x 100% ] = 82.609%. However, operation of this can crusher involves several pushes of the lever to be able to crush a can to this smaller volume. The check valve (the knob in the front side of the car jack) must be opened and closed before placing and removing another can for crushing. If used in a wrong way such as twisting it too much, it may cause the oil inside to leak out of the system. The car jack can crusher is therefore difficult to maintain and requires a large amount of work to crush a can. In addition from user’s reactions, even though they find it very portable, the prototype is not user-friendly because nobody knew how the crusher works on the spot and further explanations and demonstrations were necessary before other people can use this prototype. Also, because of the number of lever operations needed, users were complaining that too much work was needed in crushing only one can. Thus, the group decided to automate the system so that it would not be necessary to operate the lever many times and to manually open and close the check valve. However, the cost of automating the system is approximately thirty thousand pesos (P 30,000.00), which is three times the cost of manufacturing the hydraulic press design and twenty times the cost of manufacturing the hydraulic jack based can crusher design: P 30,000.00 / P 10,000.00 = 3 times the cost of hydraulic press, P 30,000.00 / P 1,500.00 = 20 times the cost of hydraulic jack. Generally, hydraulic systems are difficult to manage, whether it would be manual or automated, because the liquid inside the system must be regularly monitored for leakage and other problems. With this, the group shifted the main mechanism for crushing the can from hydraulic to mechanical design. The group decided to utilize the use of a long lever to drive the crushing mechanism in order to reduce the force required. The design also utilizes an entrance chute for cans, which could hold up to five cans, ready for continuous crushing. It also has a hole below the can crushing area to automatically release the crushed can from the machine. Figure 4 on page 10 shows the mechanical can crusher with its external and internal mechanisms. Because of these features and the fact that it uses a lever as a means to transmit the force from the user, the crusher is intended to be elevated for users to easily use the entrance chute feature, and be wall mounted or to be bolted on to a strong and stable base. This is a disadvantage for the mechanical can crusher. Because the crusher was meant to help school and office establishments to efficiently recycle aluminum cans, a cost benefit analysis was made in order to compute and infer whether the production of Pan would truly help establishments in costing matters. The establishment used for the specific cost analysis is Philippine Science High School – Main Campus. Given that • manufacturing of Pan with new materials costs four thousand five hundred pesos (P 4,500.00), • aluminum cans are sold for thirty-five pesos (P 35.00) per kilogram in most of recycling firms, • there are approximately sixty (60) cans in a kilogram of cans, and • PSHS – Main Campus consumes approximately three hundred fifty-six (356) cans in a day, it was found out that it would take only approximately 22 days to recuperate the cost for manufacturing Pan: 4500 Pesos x 1 kilogram x 60 cans x 1 day = 22 days. 35 Pesos 1 kilogram 356 cans With this, Pan could be feasibly implemented in PSHS – Main Campus environment in terms of the costing involved. However, cost analysis is not limited to this. Further cost benefit analysis on other establishments would also be recommended. Discussion and Analysis of Testing Results The main experiment performed on Pan was to compare the force needed to crush cans using Pan with that needed in the manual method. After performing ten trials for each setup (refer to Appendix A and B for complete data of these experiments), results show that the mean force needed in crushing with Pan is 28.6 kilograms while that needed in crushing with manual method is 40.5 kilograms. When computed, Pan only reduced the force by about thirty percent (30%): 100% - [ (28.6 kg / 40.5 kg) x 100% ] = 29.383%. Also from users’ reactions (during the fifty random people consistency test, to be discussed later), they generally had a difficult time operating Pan because of the great force that is still required in crushing cans. During these tests, Pan was not mounted to wall or bolted on to a strong base so they had a more difficult time because of the crusher’s instability. The group’s first consistency test was performed using only one user to crush cans with Pan consecutively. However, this could not be an accurate measure of performance by Pan because it relies on a mechanical design, therefore it relies mainly on the force exerted by the user. This is an obvious disadvantage for mechanical designs, and to further test and illustrate this, another experiment was conducted, but this time fifty (50) random people were asked to crush a can using Pan with only one pull of the lever, and the heights of the can (in millimeters) was be measured. The variance of the heights was computed to see if there are really differences between the heights of the crushed can, assuming each of the fifty people has varying strengths. The graph of the result is shown in Figure 5 on the next page (page 17, refer to Appendix C for the complete numerical data). The irregular behavior of the continuous graph illustrates how the height of the crushed cans varies greatly with each replicates or users. The distribution graph also shows that the number of cans that are crushed are not concentrated on the range of the mean height (45 -50 millimeters), but instead almost distributed evenly on the other ranges. With these graph interpretations and with the computed sample variance of 105.20, it can be said that the heights of the can after crushing using Pan relies more significantly on the user’s strength than the mechanism by which the crusher is made because of the great variations in heights of crushed cans. It is not feasible therefore for it to be compared to Bam-Bam and PeBBles’ variance and other tests because the cause for the variance of the two crushers is the force exerted by the system itself, while that of Pan is the force exerted by the user. However, if it would still be compared, Pan’s variance of 105.20 is still greater than the two crusher’s variances (variance in Bam-Bam is 9.05 while that of PeBBles is 20.01) and the mean height computed for Pan is 47.03 millimeters, which, if again compared to Bam-Bam and PeBBles, is also greater (mean height of crushed cans in Bam-Bam is 37.06 millimeters while that of PeBBles is 32.38 millimeters). Efficiency and volume tests are therefore also not feasible for Pan because of the said differences in the variance between the mechanical and pneumatic design. Figure 5. Random Consistency Test Graphs Summary and Conclusion The goal of this study is to design a portable, easy-to-use, manageable and affordable can crusher, Pan, that will reduce the crushing force required for the user compared to the manual method of can crushing - the goal of can crushing devices. The design must also be evaluated qualitatively and with minor experiment to determine whether the comparison with Bam-Bam (S. Balois et. al., 1999) and PeBBles (V. Balois et. al., 2001) is feasible. The purpose of this comparison is to determine whether the can crusher maintained the performance of these can crushers (tests were already performed on these can crushers). The first hydraulic jack aluminum can crusher prototype of Pan manufactured by the group was compact, affordable and could crush a can to a small height of approximately twenty (20) millimeters. However, the lever of the crusher must be operated many times in order to crush a can, and the check valve must be opened and closed regularly for another can to be crushed. This prototype, therefore, requires too much work and maintenance from the user. If this hydraulic design would be automated for easier usage, the cost that would be involved, however, would be too steep. The mechanical aluminum can crusher prototype of Pan could be a good can crusher in terms of its portability and affordability. Pan’s size is more compact compared to Bam-Bam and PeBBles developed by previous PSHS batches. Cost benefit analysis also shows that the cost of manufa...