RECYCLING FOR THE 22nd CENTURY

Altaf Arsiwala, Gilbert Gardu&endash;o, & Neal Lipman Department of Mechanical Engineering The University of Texas at Austin, Austin, TX

ABSTRACT

The integration of people with disabilities into society is and will continue to be an important issue into the next century. One example of how this can be achieved is being demonstrated by a school named Rosedale. One of their programs involves recyclting of aluminum cans. This provides the students with the opportunity to ineract with society while learning skills that can be used in society, and generate income for themselves and the school. In keeping with these goals, the authors designed an aluminum can crushing device that was aimed at enhancing the abilities of the students.

BACKGROUND

Rosedale School, a member of the Austin Independent School District, is a provides students with disabilities a chance to "live, work, and enjoy life in our community [1]." The school also strives to demonstrate how providing students "educational opportunities and quality instruction [1]" in addition to care and love, will "increase their independence, improve their self-esteem, and [allow them to] experience a greater quality of life.[1]" The Rosedale School currently provides students with opportunities to interact with their environment and the people around them through a variety of activities. One such activity involves recycling aluminum cans. This is intended to provide interaction and involve teamwork among a group of students. The role of the design group was to assist Rosedale by improving the current method and equipment used in the activity to increase the interaction and level of involvement of the students. The decision was made to redesign the current recycling process to accomplish this. The design team was committed to provide a safe, effective, and stimulating method for processing aluminum cans that would enable people with disabilities, at Rosedale School or elsewhere, to enhance their physical and mental development.

PROBLEM STATEMENT

Rosedale currently has a recycling process which includes cleaning, crushing, storing, and delivering the aluminum cans. The staff at Rosedale was not completely satisfied with the current process for a number of reasons. First, the current automatic crusher jams constantly which makes the process frustrating for teachers. It is crucial that the process be uninterrupted so that student interest can be maintained. Second, the current process required the teacher to assist the students more than was desired. This made it difficult for the students to be independently involved in the process. It was decided that a mechanism would be designed that would be more reliable and that would provide the opportunity for greater student involvement. Time and manpower became a limiting factor during the concept selection phase of the design. After much deliberation within the design group, it was decided to narrow the design down to an aluminum can volume reduction system. The time and effort required to effectively improve on the entire can washing and volume reduction process was determined to be less than feasible. Effort was focused on designing a new "crusher" that would allow the students with varying abilities to be involved more than they are with the existing can crusher.

DESIGN

After determining a path and direction for the team, a product design and development methodology was employed as proposed by Ulrich and Eppinger [2]. The methodology involves a structured step-by-step method for creating a product based directly on needs expressed by the customer. The needs are interpreted based on interviews conducted directly with the customer(s). Once these needs have been interpreted and ranked, a Quality Function Deployment is performed which leads to generation of actual design concepts, engineering requirements, and technical specifications. Finally, a prototype is constructed to meet these specifications and needs. The primary customers were determined to be students with disabilities and those who teach them and supervise their development. The team interviewed ten individuals including teachers, parents, physical therapists, people with disabilities. On-site observations of the current process in operation were also conducted. The interviews and observations provided the insight necessary to determine that the six most important needs were that the device should be safe, reliable, durable, easy to load, keep students interested, and not jam. In addition, two other issues were that the device be manufacturable by the staff at Rosedale, and cost less than $100 to build. In order to achieve a design that focuses on the involvement and response of the students, it was necessary to analyze the needs and relate them to student involvement in the process. The device needs to be reliable so each can that is input into the device experiences a reduction in volume and exits the system in a repeatable and anticipated manner. Reliability directly relates to the ability of the design to maintain the interest of the students. Ease of loading is important to allow students with all levels of ability to use the device. Therefore, an entry point for the device that allows a margin of error would be beneficial. Lastly, one of the more important needs determined was that the device crush cans without jamming. The current machine jams approximately 20% of the time. The intent of the future design was to reduce, and possibly eliminate, any jamming that might occur. Although the needs addressed above were important, manufacturability and cost issues were imperative to the success of the design. The capability at Rosedale is limited by the tools and staff available. The school has a small woodworking shop consisting of two staff members who build products out of wood and plastic in addition to performing simple electrical assembly. This imposed a large constraint on the design. After determining the customer needs, the target specifications for the system were developed. These specifications were necessary in determining the guidelines for the design. These guidelines quantified aspects such as safety, forces, materials, and ergonomics. Given these specifications, solutions were developed for each function of the device. These solutions were rated against each other to determine how well each one satisfied the customer needs and combined to form the overall solution. Next, specific solution principles were generated to find ways to achieve the generalized solutions. Once this was accomplished, the solution principles were scored against each other with respect to the needs. The results were summed and the concepts with the highest scores were chosen.

DEVELOPMENT

In the development stage of our chosen concept, a preliminary cost analysis was performed and the results were demoralizing. Since the staff at Rosedale were expected to be able to manufacture the device, a complex design had to be avoided. The solution, consisting of an electric motor, gear train, and a slider-crank mechanism, required a gear train that is complicated to manufacture and mount. Thus it needed to be a single unit which could be inserted into the system as is. The price of the gearbox alone was determined to be approximately $100, making the solution infeasible. The next solution, a lead screw mechanism, was also determined to be significantly over the allotted budget. Other similar solutions proved to be infeasible due to cost or manufacturability constraints. Finally, it was realized that modifying the can crusher currently in use at Rosedale would be most economically feasible. In addition, it supplied the drive mechanism, making the design manufacturable by Rosedale staff. With a rejuvenated spirit, the design team pressed on in this direction. An Alpha prototype was then built to show the functionality of the device and to demonstrate the ability of the "retrofitted" design to satisfy the customers needs (see figure 1 below). It was also used to determine unforeseen problems that might occur. After completion of the Alpha prototype, the design was reviewed. Jamming was still a major problem in the crushing chamber due to cans getting hung up on each other and not falling into the crushing chamber properly. Also, if a can was dented, it would not slide down the boxed chute to the crusher and would stall the entire process. The Alpha prototype also had not addressed the need to keep the students interested, ease of loading, durability, or safety. Therefore, a Beta prototype was constructed to eliminate the problems associated with the Alpha prototype and to satisfy the needs not addressed. (see figure 1 below).

Figure 1 - Beta prototype

The Beta prototype operates as follows: A student manually pre-forms the can, the next student drops the can into a funnel that receives and channels it into the crusher, then another student enables the crusher via a push-button or lever switch. Finally, a student receives and stores the crushed can after it has been ejected. When more than one can is dropped into the system, the first can falls into the chamber while the second sits on top of the can being crushed. The slider moves beneath the second can. The first can is crushed and falls out of the ejection port and as the slider returns, the second can falls down into the chamber. This was different from the Alpha prototype since it does not push the can out of the way, thus eliminating the need for the unreliable pushing attachment. The Beta prototype addresses the customer's needs in many ways. The safety of the device was treated with priority and the following solutions were incorporated into the design. It is imperative that the crusher not operate when a hand is within the device. Therefore, the device has been enclosed so it is inaccessible unless the user remove the lid. A cutoff switch is attached to the lid so that when the lid is removed, no power is transferred to the motor. The geometry of the ejection port was also modified to make the crushing chamber inaccessible. The reliability of the Beta to crush cans uninterrupted also increased tremendously. This prototype did not rely on the questionable pushing mechanism that the Alpha prototype required. Increased reliability of this device will lead directly to the satisfaction of students participating in the recycling activity. The Beta also provided more involvement and stimuli than the Alpha. This was accomplished in various ways. First, the cans are dropped into a funnel. The funnel allows students with varying physical abilities to perform the insertion. Exact orientation and placement of the can is completely unnecessary. Also, the funnel is constructed of sheet metal which creates audible stimuli. Second, the Beta provides an option when turning on the crusher. A choice can between pushing a simple button or pulling an adjustable force lever. This feature allows students with varying physical abilities to operate the device. The Beta also keeps students more interested than the Alpha prototype would by providing more visual and audible stimuli. The sound of the motor running, the sight and sound of the can being crushed, and the can entering and exiting the device all provide a significant amount of stimuli. Durability is an important issue because large forces are required to crush a can, and also because rough usage is inevitable. The parts that have the largest forces applied to them have been made easily changeable. This allows the staff at Rosedale to provide the can recycling activity to the students often without being interrupted by faulty equipment as has been the case in the past.

DESIGN EVALUATION AND TESTING

The device was tested to determine how well it satisfied the customers. The reliability of the device to successfully crush and eject the cans was found by testing thirty cans in the system. The reliability of a can entering the crushing chamber correctly was found to be 93% for undamaged, 90% for mildly damaged , 90% for medium damaged, and 83% for severely damaged cans. The can ejection reliability was determined to be 96%. This was a great improvement over the existing device for both ejection and jamming within the chamber. Further evaluation of the design will be done by taking it to Rosedale and testing the device by letting the students use the device to crush cans. This will enable the design team to determine how well the device keeps the students interested and how easy it is for them to load. It is expected and hoped that the students will be very enthusiastic about using the device. It is also desired that the device perform its intended purpose and provide the students with feelings of accomplishment and increased interaction with their surrounding environments. A training and maintenance program will also be developed .

DISCUSSION AND CONCLUSIONS

An aluminum can crushing device was designed to adapt to and enhance the abilities of the customer. The students of Rosedale can now more effectively recycle their cans and not only receive the benefit of interaction with people and things around them, but also generate income for themselves. The design team focused on modifying an existing design to improve and enhance the reliability, durability, ease of loading, and its ability to keep the students interest. These needs were met while keeping within budget and designing the device so it is maintainable by the staff of Rosedale School and keeping the cost around $100.

References 1. Rosedale School Pamphlet - Austin Independent School District, 2117 West 49th Street, (512) 414-3617.

2. Ulrich, Karl T. & Eppinger, Steven D., Product Design and Development, Mc-Graw-Hill, Inc., 1995.

--------------------------

Neal Lipman Department of Mechanical Engineering The University of Texas at Austin ETC II 2.128, Austin, TX 78712-1063 (512) 471-5838, ndlipman@sffoffice.me.utexas.edu