IJMEIT// Vol.06 Issue 07//July//Page No: //ISSN x 2018

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1 Index Copernicus Value Study, Analysis and optimization of Front Load Washing Machine Tripod for Maximum Strength Authors Akshay Tondwal¹, Rachayya Arakerimath² ¹,2 Department of Mechanical Engineering, GH Raisoni College of Engineering and Management, Pune University, Pune, Maharashtra, India ABSTRACT- This paper presents a study, analysis and design optimization of front load washing machine tripod. To achieve safe design of tripod the finite element analysis, analytical calculation and material testing were conducted. First, the existing tripod material is identified and studied then the finite element analysis results were analytical validated followed by design optimization. With the help of finite element analysis results of existing tripod, a feature has been added where the maximum stresses were generated and then the optimization is done in four stages. By considering the variables like material consumption, stress results and ease in manufacturing process the tripod designs have been optimized. The CAD of tripod assembly is done in Unigraphics 8.5 and finite element analysis is done in Ansys/Workbench. Keywords- FEA, Tripod, Optimization, ADC1, Washing Machine INTRODUCTION Washing machines are one of the most commonly used appliances worldwide. This machine makes washing clothes easy and efficient. Clothes mixed with water and detergent is rotated inside the drum assembly. Horizontal washing leads to minimum use of water and it is more efficient due to falling of clothes by gravity while rotating through baffles. The drum is mounted on the tripod with the help of screws such that it cannot be get loosen, even while running in unbalanced loading conditions. Drum is made up of stainless steel to sustain high loads and due to corrosion resistant property [2]. Tripod is also known as flange, spider or crosspiece, made up of die casted aluminium. It is centrally connected to motor with the help of shaft, while each legs of tripod holds the drum circumferentially. The shaft is fixed permanently to tripod by insert molded by casting process [1]. The main disadvantages of front load washing machine over top load are lower washing capacity and less drying ability. Increase in size and improving drying performance of front load will eventually increase bending and twisting load on the tripod. The centrifugal force generated during spinning cycle is so high that spider must have to be well designed to sustain that much load [3]. In this report the existing tripod assembly from one of the top brand washing machine is taken into consideration for study, analysis and optimization. The existing tripod has been studied from assembly, manufacturing, usability and functionality point of view. Washing machine runs on very high rpm and also carries load. Continuous rotation of the assembly creates high stress on assembly which is completely held by tripod. High stresses can results into breakage of spider which eventually results into walking of machine, noisy operation, huge vibration and major accidents. By considering all above factor it was very important to study the tripod and analyze it. The flow to study the tripod is, tripod is firstly dismantled from the assembly, cut into three part for 3D scanning as shown in fig.4, material is studied and then FEA is done to find out the maximum stresses in the tripod and finally FEA results have been validated analytically. Akshay Tondwal, Rachayya Arakerimath IJMEIT Volume 06 Issue 07 July 2018 Page 1826

Optimization is done considering the design variable like manufacturing process, design geometry and material consumption into following four stages. Fig.1 Drum assembly Fig.

tripod at uneven loading condition of 0.5Kg.

This research shows that the stress generated is maximum on tripod and its strength is an important factor while designing the tripod. The tripod is optimized by its structural design to an extent.

2 Optimization is done considering the design variable like manufacturing process, design geometry and material consumption into following four stages. Fig.1 Drum assembly Fig. 2 Shaft Assembly LITERATURE REVIEW With the use of PRO/E software for CAD modeling and Ansys software for FEA analysis, study has been done on the stress generation on various rotational angle of tripod at uneven loading condition of 0.5Kg. The conclusion of this research was that the maximum stress generation occurs is at the direction of force of the applied mass is parallel to the direction of tripod leg [1]. This research shows that the stress generated is maximum on tripod and its strength is an important factor while designing the tripod. The tripod is optimized by its structural design to an extent. Validation is done by taking sheet metal strip for an experimental purpose and optimizing it for increasing the strength. By considering the aluminium alloy as tripod material and applying the force of 2018N they have redesigned it and reduced the mass up to 200 gram when compared it with the initial mass was 1.5Kg by considering static loading condition. The optimization of component with the help of Finite Element Analysis was done with the help of Optistruct software [4]. Huge mass can be resulted into more vibration and walking so the research shows that mass is also an important factor when it comes to design. Less mass means less will be the centrifugal forces on tripod To help Asko appliances for conducting analysis for future level manufacturing of high capacity drums by reducing their experimentation the research has been done. The analysis was mainly concerned with an evenly distributed load at a constant angular velocity where the load was applied with the help of lead plates instead of clothes. The three dimensional model of the drum was created using the CREO software. The material of the spin tub was considered as stainless steel and analysis was done by taking this into consideration [5]. This research shows that in case of even loading conditions the distribution of load in running cycle results in distribution of force equally over the periphery surface of the drum. CAD MODELING OF SPIDER One leg of existing washing machine spider has been cut and then 3D scanned. The output file is imported into the Unigraphics 8.5 (CAD Software). The CAD modeling of the spider is completely done into the same software. Fig. 3 CAD Model of Tripod assembly Fig. 4 3D scanning Finite Element Analysis Tripod Assembly Finite Element Analysis (FEA) is an emerging and efficient tool to make correct decisions. It saves money and time in design process. Here, Ansys (FEA Software) is used to analyze the current front load washing machine tripod. The CAD model of the drum assembly is imported in Ansys software. Table.1 Mechanical properties of Tripod and Shaft Material Yield Strength (MPa) Young s Modulus (GPa) Ultimate Tensile Strength (MPa) Density ( kg/ mm^3) ADC AISI Stainless Steel The tripod material is applied as ADC1 which is aluminium die cast alloy, shaft material is applied as AISI 4340 and Drum material is applied as Stainless steel. Akshay Tondwal, Rachayya Arakerimath IJMEIT Volume 06 Issue 07 July 2018 Page 1827

tripod model. L1 is distance between unbalanced load (mass) and bearing 1. L2 is distance between bearing 1 and bearing 2.

mrω2 (1) For existing tripod, object mass m is 0.

1, F = 2450 N Bending Moment for the assembly can be calculated by, M=F x (3/4) L (2) From Eq. (2) M=148633.94 N.

Both bearing outer races are fixed and shaft is free to rotate inside the inner race as shown in fig.

3 Fig. 5 Meshing Table. 2 No. of nodes & elements Type Nodes Elements Solids After meshing the next step is to set-up right loading case in Ansys in order to determine the strength of the existing tripod model. L1 is distance between unbalanced load (mass) and bearing 1. L2 is distance between bearing 1 and bearing 2. When the drum of radius R having an object of m (kg) is rotating at a speed of ω, the centrifugal force F is generated in form of bending force [3] which can be calculated by, F = mrω2 (1) For existing tripod, object mass m is 0.5Kg, R is 1400rpm and load is applied on distance of 3/4*L, taken into consideration for unbalanced loading condition [3] [6] so from Eq. 1, F = 2450 N Bending Moment for the assembly can be calculated by, M=F x (3/4) L (2) From Eq. (2) M= N.mm For the boundary conditions the shaft and the tripod with drum is given bonded contact. Both bearing outer races are fixed and shaft is free to rotate inside the inner race as shown in fig.9 Moment and load is established according to the point when a specific unbalanced mass is placed in the front portion (L) of the spin drum. Considering the above case, the drum is rotated at 146 rad/sec with the application of remote force as shown in fig 5. And M = N.mm applied centrally to the assembly Fig. 7 Remote force of 5N Fig. 8 Rotational velocity of 146 rad/s Fig. 9 fixed outer race of bearings Fig. 6 Outline diagram of Assembly Outcome of Analysis The maximum stress generated is at the minimum cross section of the tripod as shown in the fig. 10. The Von Mises stress generated here is Mpa. The stress generated is much closer to its yield point and the factor of safety of this tripod is Akshay Tondwal, Rachayya Arakerimath IJMEIT Volume 06 Issue 07 July 2018 Page 1828

Fig. 10 Maximum stress in existing tripod ANALYTICAL VALIDATION OF FEA RESULTS The unbalanced bending on tripod results in high bending a tensile stresses, the maximum bending stress on spider can be

Normal stress can be calculated by, σ2 =F/A (4) Where F is maximum centrifugal force on one of its leg and A is cross section area of the same.

4 Fig. 10 Maximum stress in existing tripod ANALYTICAL VALIDATION OF FEA RESULTS The unbalanced bending on tripod results in high bending a tensile stresses, the maximum bending stress on spider can be calculated by, σ1 =M.c/I (3) Where c is distance of neutral axis from cross section and I is area moment of inertia. Normal stress can be calculated by, σ2 =F/A (4) Where F is maximum centrifugal force on one of its leg and A is cross section area of the same. The total maximum stress on leg can be calculated by adding normal stress and bending stress [6]. σ=σ1 +σ2 (5) For existing tripod c is 11.67mm and I is mm4 so from Eq. (3) (4) (5) σ1 =81.83 MPa, σ2 =3.4 MPa, σ=85.23 MPa Optimization of Tripod The objective of the optimization is to make the tripod safer by increasing its factor of safety. To make tripod withstand on high load and rpm the addition of material in the form of shape optimization is taken into the consideration. To come up with the ideal design the focus is given on the less material consumption, geometry of design, manufacturing process etc as shown in fig. 12. Various designs have modeled to optimize the tripod to its best level. Fig. 12 Redesign objectives and Methodology With approach of design safety, less material utilization and all design variables the optimization is done in four stages. The different CAD model is done in UG 8.5 and by considering the same loading and boundary conditions the FEA analysis of each stage is done. Here, Optimization of design is done by taking FEA results of previous stage design of tripod. In first stage the flat rib is added in all three legs of tripod as shown in the fig.13. Here, the total volume is increased by 532mm3 and FEA analysis is done. Fig. 11 existing tripod cross section Maximum stress occurring on tripod in FEA analysis is 89.6 MPa, when compared to analytical results which is 85.23MPa is less than 5% and factor of safety for FEA results is 1.45 and for analytical results is 1.52, hence validate the FEA results. Fig. 13 Flat rib Stage-1 Akshay Tondwal, Rachayya Arakerimath IJMEIT Volume 06 Issue 07 July 2018 Page 1829

taking this factor into consideration one more design in made as stage 4 as shown in fig. 17 Fig.

shown in Fig. 15. Fig. 17 Curved rib stage 3. Fig. 18 Curved shelled rib stage 4 Fig.

material. The designed rib from stage 1 is shelled and volume is reduced to 423mm3 as shown in fig.

The result of stage two also shows that more material can be reduced. Fig.

shelled to reduce its volume as shown in fig.18.

20 Maximum stress in curved shelled rib tripod Fig.

reduced to 290mm3. The FEA analysis is done by considering the parameters. The maximum stress generated here is 32.

5 taking this factor into consideration one more design in made as stage 4 as shown in fig. 17 Fig. 14 Flat shelled rib-stage 2 Maximum stress generated by adding this feature is 13 Mpa which is not even near the rib as shown in Fig. 15. Fig. 17 Curved rib stage 3. Fig. 18 Curved shelled rib stage 4 Fig. 15 Maximum stress in flat rib tripod The FEA results of stage 1 show that tripod can be more optimized by reducing its material. The designed rib from stage 1 is shelled and volume is reduced to 423mm3 as shown in fig. 14 The FEA analysis is done for stage 2. The maximum stress generated here is 40.55Mpa. The result of stage two also shows that more material can be reduced. Fig. 19 Maximum stress in curved rib tripod From the stage 3 FEA results the rib feature is modified, the curved featured is shelled to reduce its volume as shown in fig.18. By shelling the curved feature the volume is reduced to 220mm3 and final analysis is done. Fig. 20 Maximum stress in curved shelled rib tripod Fig. 16 Maximum stress in flat shelled rib tripod In stage 3 the flat shape of rib is remodified into curved shape and volume is reduced to 290mm3. The FEA analysis is done by considering the parameters. The maximum stress generated here is 32.13Mpa which is still much safer and can be more optimized to reduce its material consumption. By CONCLUSION Results show that maximum stress generated is near the least cross section area of the tripod. The rotation of Assembly at 143rad/sec with a failure design can damage the tripod and can consequence an accident while running. The research and analysis has made the tripod safe so that it can Akshay Tondwal, Rachayya Arakerimath IJMEIT Volume 06 Issue 07 July 2018 Page 1830

6 withstand on higher load and can avoid accidents. Table.3 Optimization results Stages Tripod Rib Type Von Mises Stress at rib (Mpa) Factor of Safety Volume (mm3) 1 Flat Rib Shelled Straight ribs 3 Curved Rib Curved Shelled Rib The shape optimization of tripod by considering the entire mentioned design variable helped this research to come up with an ideal solution. With the approach of material reduction from the mass manufacturing perspective, huge amount of material can be saved and can be utilized for more production which will eventually save cost and time, Table.3 shows the optimization results. 6. Jung-Hyo Lee, Tae-Woong Kong, Won- Chul Lee, Jae- Sung Yu, Choong-Yuen Won Load modeling for the drum washing machine system simulation 7. Hee-Tae Lim, Weui-Bong Jeong and Keun- Joo Kin Dynamic Modeling and Analysis of Drum-type Washing Machine International Journal of Precision Engineering and Manufacturing Vol 11, No.3, pp Thomas Nygards and Viktor Berbuk Optimization of Washing Machine Kinematics, Dynamics and Stability during Spinning Using a Multistep Approach Springer, Sweden, December Roc ıo Gonza lez Zuheros, Raimundo Abril Lo pez and Pablo Huertas Molina Structural Analysis of a Washing Machine Through its Loading Cases Sweden, REFERENCES 1. Sun Weili, Zhang Sen, Ge Weiwel and Li Yuanyuan Structural Analysis of Inner Cylinder Components of Drum Washing Machine Based on Ansys/Workbench Applied Mechanics and Material Vols (2013) China, July 2013, pp Clieve Marsh, Steve Taylor, Paul Milliken and Galka- dowitesenaratne (Sena) Developing and Understanding of washing machine dynamics 3. K. VenkataKrishnaiah and Rama Narasimha Reddy Design and Analysis of Washing Machine Drum Interna- tional Journal and Magazine of Engineering, Technology, Management and Research, India, October 2016, pp Sunil Patil and S. A. Kulkarni Optimization of Crosspiece of Washing Machine IJRET, India, March 201, pp Dinesh Kumaar and S. Palanisamy IJRSET Stress analysis of washing machine drum IJRSET Vol.4, Special Issue 6, May2015 Akshay Tondwal, Rachayya Arakerimath IJMEIT Volume 06 Issue 07 July 2018 Page 1831

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