Theoretical and experimental investigation of mechanical parameters affecting the dishwasher cleaning performance

While technology has been being improved day by day, investigation on machines which simplify human life is increasing. Household appliances which are used frequently in house that people can spend most of their time are affected positively. Research and Development operations that facilitate the human lifestyles are performed at R&D centers of companies. Home appliance producers competes each other in order to obtain more efficient, low-energy consuming, more silent machines and companies focus on them and make their intensive efforts on these points. World's most known firms which creates home appliances investigate deeply for designing different and unique machines and development of customer perception. High number of production demonstrates considerable demands of customer. Increase in sales figures of companies can be possible by producing machines which elevates customer comfort and machines with making difference. In this thesis, it was aimed to increase washing efficiency of dishwashers which is one of the washer appliances. Therefore, spray arm mechanism has been examined in detail with experimental studies and differences on performance has been observed by creating prototype. Dishwashers take part almost every home nowadays and they have been being designed so as to ease style of human living. In this extent of study, history of dishwasher has been examined. Dishwashers are defined as machines which perform kitchen equipments cleaning and rinsing. The first cleaning system has been discovered at second half of 19th century and they are not automatic as today's machines and they have more likely mechanic structure. Then, automatic dishwashers have been coming into human life at 20th century. By development and optimization, these machines has been transformed into current figure. Primarily, structure and working principles of dishwasher has been addressed in order to obtain new structural design with elevated performance. Dishwashers are basically divided into 4 parts which are defined as boiler, door, washing group and control panel. Extent of this study includes components of each part and their function in details. The most important subject is washing group which affects washing performance. Washing group is composed of lower spray arm, upper spray arm, lower basket, upper basket, filter, cutlery basket. Lower spray arm has been supported with lower region boiler while being independent from lower basket. On the other hand, upper spray arm has been located at the bottom of the upper basket and they have been moved together. Nozzles on the spray arm have been located at the region in order to gain more efficient washing and cleaning performance. Waste materials have been collected from dirty dishes and filter groups which also remove external materials from washing water. Soils at dishwashers which are closed system are removed by combination of chemicals and mechanic effect. Washing steps are divided into hot and cold. Firstly, cold washing steps are performed, then, hot washing steps are applied. After these washing steps were terminated, rinsing step begins and drying step will be followed. When cleaning process has been started, running water is heated until appropriate temperature in respect to chosen washing program. Cleaning performance is dependent on 4 parameters which are chemical effect, mechanic effect, temperature and time. In this research, studies are focused on increase of mechanic factor which is the parameter of washing performance. Although washing efficacy of mechanic factors is lower than chemical factors, chemical washing methods are not preferred, since, most of the people are prone to choose healthy and natural living. In addition, customer experiences were not recorded with maximum satisfaction until now. Therefore, alternative resolution procedures were searched. Confirmation of this study which aims enhancing cleaning performance by boosting mechanical effect can be explained by defining mechanic effect and how it can be raised. By scope of literature research, cleaning procedures has been stated simply. Water jet impact on washing performance, experimental standards of washing practice and studies about boosting washing performance has been examined. 3 crucial elements which affect cleaning performance exist: water pressure, speed of spray arm, the angle of arrival of the water on the contaminated surface. According to these parameters, cleaning performance of dishwasher can be varied machine to machine. EN50242 "Test methods for measuring the performance of electric dishwashers for household use" standards are applied in order to clarify cleaning performance. According to these standards, it is determined that machines which are tested could be classified and specified which machines are belongs to which class in respect to their score. It can be compared with each other and measurement of performance enhancing can be analyzed by using these scores. Designs which are able to wide to cleaning area and spray arm mechanisms which rotate with gearwheel has been surveyed at the extent of patent research. Examined studies point out that numerous different resolution ways exist. Dishwasher spray arm system has been analyzed during design phase and some lack points which needs to be developed have been identified. Dishwasher contains 2 spray arms which are upper spray arm and lower spray arm. Lower spray arm of dishwasher is located under of washing basket and center of washing area. Nozzles which are located at spray arms have been positioned in which best performance and angle could be obtained. During creating designing criterias, it was paid attention that geometric limitation which belongs to current design was conserved and it was noticed that minimum alteration has been applied on design of present system. Thus, design criterias has been generated via performed trial and design has been made in respect these metrics. This study results in project simplification while decreasing the cost of project. After designing criterias had been created, draft sketch has been completed. Then, design has been constituted at CAD software upon calculation and dimensioning. Geometric limitation which design was not able to overcome has been detected at preform stage. On the other hand, visible gear mechanism inside of the dishwasher does not satisfy customers according result of survey and research on customer demands. In order to handle with these problems at the preform stage, it was studied on new resolution ideas. In the result of this situation, gears were placed inside of spray arms and it was focused on designed system, primarily. To reach final stage thereby designed gears were positioned inside of the spray arms, dimension of spray arms and gears have been calculated once more. Bearing of spray arms and gears were differentiated in respect to preform stage. Main spray arm has been brought into gradual form so as to overcome geometric limitation. At the confirmation stage of final design, mechanical effect factor has been established by using articles at literature. Mechanical effect factor has been expressed mathematically and design was confirmed by comparing existing dishwasher mechanical effect factor with mechanical effect factor at new design. After design had been confirmed, prototype has been manufactured. It was utilized from 3D printer, which is additive manufacturing technology and CNC during prototype manufacturing. Gears and spray arms were manufactured by applying machining process at CNC after materials has been selected. Thanks to this manufacturing procedures, prototype has been obtained rapidly. The working prototype was mounted on the machine and subjected to experimental work. These experimental studies were carried out according to EN 50242 "Test methods for measuring the performance of electric dishwashers for household use" standard. It was observed that cleaning performance of new design whose cleaning performance has been measured has been increased and it corresponds to experimental result and mathematical result, which was obtained from mechanical effect factor. Increasing cleaning performance during running of dishwashers were confirmed by applied methods, experimental design, mathematical model and spray arm system with high performance aroused.