Dynamic model of a fronty loading washing machine

Home appliance industry has become more competitive than ever in recent years because of the technological development. Production expenditures are reduced with the new manufacturing systems and advancement in material science. Thus, consumers can purchase these goods cheaper than it was before. Balance between production cost and price competition, decreases company profits. This situation forces companies to reduce manufacturing costs even more by keeping their production system up to date and modifying poor part designs. To accomplish this goal, the current system should be examined to determine possible improvements and simplifications. The main objective of this thesis is creating a front loading washing machine model in order to examine and predict several poorly-designed-locations and improvable sections. The washing machine model is builtby using Finite Element Method, because it is cheap, easy to create and less time consuming than other evaluation systems. Using numerical method also allows analyzing different designs by making a few extra changes. First, a literature is study carried out to review any standards or related studies for creating numerical model. Although there are manystudies, which contain numerical model and test system couples, there are a few standards related to washing machine modelling and testing process. During the spin phase non-fixed clothes pushed away from the rotation axis by the centrifugal effect. These standards specifies some norms about modelling unbalanced clothes. According to norms, unbalanced textile can be modelled as a sheet metal fixed to the inner surface of drum. Its mass and dimensions varies depending on washing machine type and loading capacity. The studies related to washing machine modelling mostly base on multibody dynamics, thus all parts are connected other parts with singular nodes. Although this numerical modelling format is efficient to determine system oscillation characteristic, it is insufficient representing contact behavior between parts. On the other hand, better contact behaviors have released by other studies, however this type of relation between parts accomplished only in steady state solutions. Without time variable, the effect of two damper is neglected from the system. In addition, a literature study is also carried out for building a numerical model of roller bearing. Studies mostly focus on ball-race contact behavior; these bearing models are toolarge to integrate to another numerical models. Therefore, simplifications in bearing modelling is investigated to reduce numerical model size. Lastly, fiberglass contained polymers are examined in terms of mechanical, thermal and rheological properties for possible design and material changes. In the thesis, a numerical model for a front loading washing machine during its spin phase is released. This model assembled by structural parts like: shaft, bearings, tub and drum. Non-load-bearing parts like: contrete blocks and motor are attached to the system as concentrated masses. Since these parts do not carry or transmit any forces this simplification lessen total solving time for the model. As boundary conditions, two spring and two damper elements are used to fix tub at the global coordinate system. In addition, a centrifugal force, due to unbalanced mass, is applied to the drum inner surface to simulate washing machine spin phase. Normally, drum spins inside the tube and textile causes to centrifugal force as unbalanced force during spin. To create an actual system like it is described, multibody dynamic procedure should be used. However, with its poor contact behavior, it would be insufficient for some components. On the other hand, building entire system with drum spin motion and contact behavior would require much more computation power. In order to simplify numerical model, forces on the drum surface spin instead of drum itself. As last boundary condition, enginebelt forces is acted at the end of shaft. After solving numerical problem, displacement results at certain locations are compared with experimental results, and it is observed that these two results collected from different models are similar. This similarity between two results proves that numerical model accurate enough to be used in future work. In addition, stress results are examined in numeral model for predict future changes. While screening spin results, generally focused on bearing and busher region. At the next stage, manufacturing analyzes is carried out for busher and component related to it. Firstly, contact pressure between bearing races and related components. Although contact surfaces have similar tolerance clearances, surface pressures also depends on part geometry and material. After that, a thermo plastic injection molding model is built to simulate the contact behavior between busher and tube during injection molding and afterwards. There have been some simplifications at injection molding model of tub. Since these analyses conducted to study and examine the contact area, tub geometry reduced to a local geometry by applying proper boundary conditions. After tub model built, plastic injection molding analyses is performed 4 phases. These phases are: Fill, the phase that polymer fills cavity. Pack, which is material continues to fill cavity slowly to prevent shrinkage. Cool, the phase that temperature of the polymer reduces. Warp, the phase that product deform at ejected from cavity.In addition, material viscosity calculation models are discussed to use in cavity fill phase. Two new model has been suggested in order to reduce production costs and manufacturing by taking consideration of spin phase analysis results and thermoplastic injection molding analysis results. These new models are also tested for spin phase and manufacturability. In the first model, busher divided into three separate parts to assemble from more standardized and easy-to-manufacture components. These three parts can be produced by applying machining operations on standard steel parts. Contact surface pressure that occur in bearing – busher interaction are recalculated since busher design and material has changed. Considering spin phase results at current model and first model suggestion, it is observed that displacement at the control location (between drum and tub) and stress distribution at bearing-area-parts are almost identical. Then, plastic injection molding analysis is carried out for certain section of tub. Center of the tub geometry has changed with the new design of busher. These changes causes cooling problems during plastics injection cooling phase because of its thick material regions at the center of the tub. In addition, first busher suggestion requires extra surface tolerances at the contact surfaces of three busher components for reliable assembling, and this increases manufacturing cost and time. For the second model, while strong sides of first model conserving, weak sides are modified for improvements. Two metal components of the first busher design are kept, and one in the middle is replaced with polymer part. After two metal component are shaped to their final form by machining process, they are used as inserts in thermoplastic injection molding to manufacture second busher model. As fill material, fiber reinforced polyamide is used in injection molding. First, a numerical spin phase model is established for the second design, and considering this model, displacement results between tub and drum are almost same in current model and second model suggestion. For the stress distribution, similar results applies for bearing and shaft region. Contact region pressure are identical with the first model suggestion, since surrounding component are the same for bearing races. Manufacturing analysis are conducted in two steps as thermoplastic injection molding of busher with fiber reinforced PA material and thermoplastic injection molding of tub with PP material. For the first step, two metal busher component is placed in cavity as inserts to simulate molding with PA material. Fiber reinforced PA shows different mechanical and thermal properties like; thermal expansion coefficient and modulus of elasticity, based on its fiber orientation. By controlling fiber orientation, modulus of elasticity can be increase in desired direction, thus busher can be more stiff in certain directions. Similar to this, by controlling fiber orientation, thermal expansion coefficient can be controlled, thus large warpage values can be prevented. The fiber orientation of the part defined by the fill phase of the plastic injection molding. Folgar – Tucker is used to predict fiber motion in molten polymer during fill phase and determine fiber orientation after it solidified. In addition, these material properties are controlled and reoriented by changing rib placement on the busher. In addition, second model suggestion promises better cooling results with the help of increased total surface area. The changes in busher design also favor cooling rates during tub injection molding because of its rib placement and total busher – tub contact area. In this study, washing machine spin phase model and several manufacturing model are built in order to examine displacement and stress results for the system during spin and cavity fill time, cooling time and warpage results for certain parts during thermoplastic injection molding. Considering these results, two model suggestion are given in this study, then tested for spin phase and manufacturability. Lastly, all there models are evaluated for strong and weak sides in terms of analysis results. As a result, a numerical model is established for a front loading washing machine. This system can be used for predict possible improvable regions and inspire future work. With the help of this model, system modifications can be analyzed before prototyping step, and this reduces research and development expenses dramatically. In addition, a modification model is explained step by step to guide future studies.