Development of compaction system for reverse vending machines
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This master thesis addresses the product development of a screw compactor adapted to Tomra Systems ASA rear room system Multipac . Tomra is a leading company in the business of recycling used beverage containers in Norway and much of Europe. The compactor process in a reverse vending machine has an impact on the entire system's capacity, compaction rate, lifetime and storage capabilities. Thus, it is a crucial part of the total value of a RVM. The project description was formed between three actors; NTNU, Tomra and the student. It satisfies academic requirements from the university, commercial objectives from the company and background and interest of the student. This thesis contains a concept selection, a product requirement specification, analysis of alternative sub-concepts, testing and a final recommended design in the form of a CAD drawing. It takes into considerations various alternatives both concerning infeeds of objects and around the gripping ability of the screw. It also deals with technical considerations of the various components and the assembly of these. Several tests were conducted. These contributed to a better understanding of the screw compactor and its properties. It also provided verification and assessments of concepts. Testing of sub-concept implied how the machine behaved when inserting objects from the side, thus that the guide rails in the screw housing are essential for the progress of objects. It also showed that the longest objects had a tendency to ride the helical turn and thus did not enter the screw. Attempts to improve gripping performance were accomplished by cutting out parts of the screw thread. It turned out that objects were often stuck on this cut. By making a cut with smooth edges, the tendency for this became smaller. Some cutouts caused objects to have a void they could slip into, and the object-riding problem was close to eliminated. Based on tests, dimensioning and acquisition of knowledge, a final concept recommendation was designed in Siemens NX. It included a full-featured machine assembly adapted to a Multipac cabinet. Many of the choices taken during the project were based on finding the optimal solution, not the easiest solution. This means that there are still uncertainties associated with the final concept and further research should be conducted to attain a valid concept. By building the designed prototype and conducting systematic testing, one can end up with a compactor that is better than today's compactor, higher compaction rate, longer life and higher capacity.