Ev tipi çamaşır makinaları için plastik kasnak konstrüksiyonu
Plastic pulley design for consumer washing machines
Yazar: ASLI GAMZE DALKILINÇ
Danışman: YRD. DOÇ. DR. VEDAT TEMİZ
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Makine Mühendisliği Ana Bilim Dalı / Konstrüksiyon Bilim Dalı
Derece: Yüksek Lisans, 2016
Konu: Makine Mühendisliği = Mechanical Engineering

Özet:
Gelişen teknoloji ve artan rekabet, mühendislik firmalarını kendini geliştirmeye zorlamaktadır. Değişen ekonomiye ve piyasalara uyum sağlamak, olası değişikliklere hazırlıklı olmak için, firmalar alternatif üretim yolları ve malzemeler aramaktadır. Özellikle beyaz eşya sektöründe, çok kısa sürede, görsel ve performans açısından geliştirilmiş yeni ürünlerin piyasaya sunulması çok önemlidir. Arçelik'in beyaz eşyalarında kullanılan her bir parça için başlıca hedefler, daha yüksek performans, daha kısa sürede üretim ve daha ucuza mal edilmesidir. Çamaşır makinası üreten firmalar, pazarda kalmak için düzenli olarak piyasayı takip etmek ve kendini geliştirmek zorundadır. Arçelik, rekabetin ve inovasyonun önemini bilen bir firmadır. Arçelik Çamaşır Makinası Arge Departmanında, bu hedeflere ulaşmak için sürekli bir çalışma yürütülmektedir.
Bu projede, Arçelik'in önden yüklemeli kayışla tahrikli çamaşır makinalarında kullanılmak üzere bir plastik kasnak tasarlanmıştır. Arçelik'in mevcut kasnağının malzemesi alüminyum olup, ucuzlatma projesi olarak malzemede alüminyumdan plastiğe geçilmesi ve şirketin değişen hammadde piyasalarına karşı hazırlıklı olması için bir alternatife sahip olması açısından yeni bir tasarım çalışılmıştır. Tasarıma başlamadan önce, literatür ve patent araştırması yapılmıştır. Tasarım kriterleri belirlenmiştir. Arçelik'in belirlediği kriterleri sağlayacak en uygun plastik malzemeler seçilmiş, bu malzemeler ile çalışılması halinde gelecek olan maliyet hesaplanmıştır. Rakip firmalardan plastik kasnak kullananların kasnakları incelenmiştir. Seçilecek malzeme, mevcutta kullanılan kayışlar ile de kullanılabilir olmalıdır. Bu yüzden, mevcut kayış ile alüminyum ve seçilmesi muhtemel malzeme arasındaki sürtünme katsayısını belirlemek için özel bir test düzeneği kurulmuş ve testler yapılmıştır. Testler sonucunda elde edilen katsayılar, kayış hesaplarında kullanılmış ve karşılaştırmalar yapılmıştır. Alüminyum kasnak çıkarılıp, yerine plastik kasnak takılabilecek şekilde tasarım yapılmıştır. İlk tasarım gerçekleştirildikten sonra Çin'de tek adet prototip üretimi yapılmış ve bu prototip ile temel testler gerçekleştirilmiştir. Tasarım üzerinde gerilme ve kalıp analizleri gerçekleştirilmiştir. Analiz ve test sonuçlarının ışığında tasarımda iyileştirmeler gerçekleştirilmiştir. İdeal malzemeye; şirketin plastik kasnağı kullanabilmesi açısından birçok kriter göz önünde bulundurularak, maliyet, moldflow, gerilme ve deplasman analizlerinin ve yapılmış testlerin sonuçları incelenerek karar verilmiştir. Malzeme PA6 GF60 olarak seçilmiştir. Son tasarımın teknik resmi ve montaj ilişki tabloları hazırlanmıştır. Nihai tasarım için kalıp ürettirilmesine karar verilmiştir. Bu kalıptan alınacak numuneler ile birçok dayanıklılık testi gerçekleştirilecektir. Bütün bunların sonucunda plastik kasnağın ilk olarak Arçelik'in önden yüklemeli kayışla tahrikli makinalarında uygulamaya alınması planlanmaktadır.

Abstract:
Developing technology and increasing competition force the engineering companies to improve themselves. To keep pace with the changing economy and market and to be prepared to possible changes, the companies seek for alternative production methods and materials. It is really important to release new products with improved aesthetics and performance in a really short time, especially in the white appliances market. Main targets for every part used in Arçelik's white appliances are having a better performance, having a shorter production cycle and reducing costs. Washing machine companies have to follow the market and improve themselves to stay in the market. Arçelik knows the importance of competition and innovation. Arçelik Washing Machine Research and Development Department works continuously to reach these targets.
Engineering plastics are improved by the material companies in the recent years. Plastics are much lighter, stronger and durable. The replacement of metals with plastics is really popular in so many engineering fields such as automotive, environment, white appliances or even aviation.
Like so many washing machine companies, Arçelik currently uses aluminium as the material of drum pulley. Having alternatives for every part used in production is really important since trades are affected daily by the political issues. This also means having alternative materials for the parts as well. Metals are becoming more and more expensive with the limited sources on Earth. Arçelik has washing machine plants in Turkey, Russia and China. While aluminium is cheap in Turkey, it is expensive in Russia and China. Therefore, it is essential to be prepared to the unsteady markets.
In this thesis; a plastic pulley is designed to be used in Arçelik's front load belt drive washing machines. After introduction of washing machines, belts and pulleys, the problem is defined. Literature and patents are researched. Relevant patents are discussed. Then the purpose of the thesis is decided conclusively.
For the 3D designing process, design criterions are determined according to the working conditions of Arçelik's washing machines. A list of criterions is created in accordance to geometry, material properties, storage conditions, production and cost. Arçelik's former plastic pulley design is examined, the advantages and disadvantages are discussed. The most suitable engineering plastics that maintain Arçelik's criterions are chosen and compared by properties and cost. Feasibility analysis is performed for the most expensive material. The limit volume of the part, production time, tool life, tool investment cost, production machine cost and secondary production cost are determined. Rival companies' plastic pulleys are examined by the geometric properties and materials.
The new design is supposed to work with the current washing machines as if the aluminium pulley is removed and the plastic pulley is assembled. Therefore, plastic pulley is going to work with the same belt used for aluminium pulleys. To make sure the belt drive works without a problem, calculations and tests have to be performed. A special test set up is created to compare the coefficient of friction between the belt and aluminium and the material likely to be selected. Later, the calculations are done with the coefficient of friction values provided by the belt companies.
In the light of gathered information, a new design is created on computer. A prototype must be produced and analyses have to be performed to make sure the part is safe to work with, since the tool investment costs a lot. Therefore, the data is sent to prototype producers in China. 1 unit prototype is produced from a PA6 GF30 block using CNC. Basic tests and assemblies are performed on the prototype, and the downsides of the design is determined.
Using an FEM software, static stress and displacement analyses are performed. The part is defined as solid and tetrahedral mesh is used. The shaft, pulley and belt contacts are defined. The belt is loaded with the maximum belt load obtained from the tests performed on the washing machines. The pulley is positioned for two different conditions. The shaft is loaded as if there is an object stopping the belt drive during the spinning cycle of the machine and the motor is still trying to spin.
Mould analyses are performed by the injection tool company. The results are evaluated and some changes are determined.
With the results of the analyses and tests, some improvements are performed on the geometry of the design. After the tests, the arms of the pulley are decided to be pulled backwards to avoid pulley contact with the tub. After the stress and displacement analyses, the arms are decided to have gaps in the middle part since the arms do not have so much stress on. After the mould analyses, the geometry of the rim is determined to be changed to have a better flow during the injection process.
When the second design is finished, a prototype is produced and the basic tests are performed on the prototype. The same analyses are performed on the last design. All the information is evaluated and the final design is determined.
The ideal material is chosen considering the criterions for Arçelik to use the plastic pulley, the cost, the feasibility, mould, stress and displacement analyses and the basic tests. The chosen material is PA6 GF60.
In washing machines, pulley works with so many parts directly or indirectly. These parts are bearing, bearing housing, shaft, belt, motor, screw and tub. To define the relationships with all these parts, a table is created to explain all the important measurements for the assembly with these parts. Since the pulley is a rotating part, the balance is really important for the sake of the machine. Also, the surface quality is important for the belt contact. The specifications are determined for the optimum working conditions. To explain the assembly and the measurements, technical drawings of the assembly are created.
When the parts are delivered to the plant, some of the measurements must be taken to make sure the part is ready to be assembled. Some of the measurements on the part is essential for the machine. These measurements are decided and the technical drawing of the part is created accordingly. 
The analyses and tests showed that the design is worthy and the injection mould tool is decided to be produced. However, before using the plastic pulley for the machines to be sold, Arçelik must make sure the plastic pulley is safe and durable. The prototypes will be produced to perform several mechanical tests such as durability during life cycle of the washing machine, under high stress and different ambient conditions. The design is expected to complete all the tests successfully.
In case of an error, the design can be changed to make it stronger. Removing the gaps on the arms, adding extra ribs or making the hub material metal are alternatives, as long as the design remains feasible.
As a result of these, plastic pulley is planned to become Arçelik's front load belt drive washing machines' pulley.