International Journal on Mechanical Engineering and Robotics (IJMER)
________________________________________________________________________________________________
Design, Analysis & Optimization of Impeller
1Zeyaullah Ansari, 2N.V.Srinivasulu
1VIF college of engg, Hyderabad.
2CBIT, Hyderabad-75.
Abstract : The project is about application of reverse engineering in part modeling of Impeller. Reverse engineering helps in obtaining the geometry of part or product which is not available. Its application makes it possible to reconstruct the original component with its drawing and manufacturing process. It is used in various fields but here the main application is related to a damaged impeller of an old 0.5 HP motor. Currently this part is not available in the market as it is out dated and drawing of the component does not exist. As the part is no longer available it has to be made in-house so it will require all activities from designing to rapid prototyping. The procedure includes various stages which will help understand the different phases of reverse engineering.
The process starts with understanding the reverse engineering procedure. The part geometry is first obtained with the help of scanning technology. Then with the use of different softwares the three-dimensional image of the damaged impeller is obtained. Once the image is obtained the part is optimized using ANSYS software.
I. INTRODUCTION :
This is most crucial part of Reverse Engineering. After reviewing the most important measuring techniques, the relative merits and difficulties associated with these methods are discussed. Often, methods for reverse engineering are developed based on simulated data acquisition only. Our experience is that a certain amount of reservation is needed in such cases, as actual physical measurements may display many problems and undesirable side effects not present in artificial data.
II. LITERATURE REVIEW:
A paper by Eyup Bagc defines obtaining CAD data step by step from damaged three different parts to reproduce or make a new design for some recoveries, which has no technical drawings. When these parts had been recovered, some problems occurred. These problems have been solved by referring to some practical approaches. Establishing continuity across curve and surface patches is an important concept in the free form surface modelling. The CAD models were recovered and reconstructed to consider parametric and geometric continuity. The iso-phote method was used for surface continuity analysis. Hence, in this work, not only occurring problems but also solving methods were explained. Firstly, CAD models are created from damaged and broken parts by data digitization method
by using CMM and the process was explored in detail.
Later, CAD models that had been obtained earlier are transferred into CAM module of the software and G codes are taken by the NC post-processor, and finally, the parts are manufactured by means of CNC milling machine.
Bhupendra Raghuwanshi, Viswash Tomar in a paper on Computer aided Reverse engineering for replacement of a part present methodologies and technologies for computer-aided reverse engineering, illustrated by a case study of a pipe joint of a pipe line assembly. It involved reconstruction of part (creating 3D computerized model) from a cloud of points acquired from a physical object.
For this Comet5 laser scanner is used. The most crucial part of the reverse engineering is the segmentation and surface fitting. Here the individual (natural) surfaces of the object have to be determined and surfaces of suitable geometric types have to be fit. Feature based approach is used for surface fitting. Consequently, their research work seeks to develop automatic, efficient and robust reverse engineering methods to meet practical requirements.A paper by V. Tut, A. Tulcan, C. Cosma, and I. Serban Application of CAD/CAM/FEA, reverse engineering and rapid prototyping in manufacturing industry presents some aspects about rapid prototyping which stays at the base of manufacturing design using CAD/CAM/FEA programs, scanning and measuring machining and its integration in industrial field. A big economical advantage is that products made by rapid prototyping express a low risk failure and the manufacturing process takes less time and involves lower costs than the conventional techniques. A new gasket for a ball screw used in a bending tube machine was produced by rapid prototyping techniques starting from a broken one. First thebroken gasket was scanned by Modella Roland LPX-600 scanning machine obtaining the primary 3D model which is imported to CAD/CAM programs and the final product is achieved on ISEL GFM 4433 milling machine. The gasket mechanical characteristics were investigated by finite element analysis (FEA). FEA provides a way of simulating the gasket design under working condition and an opportunity to understand interactions with the mating machine. Therefore, problems in tooling or mould mating would be minimized. After FEA simulation a new material was chosen in order to
increase the mechanical characteristics.
The work done by William B. Thompson, Jonathan C.
Owen, H. James de St. Germain, Stevan R. Stark, Jr., and Thomas C. Henderson on Feature-Based Reverse Engineering of Mechanical Parts describes a prototype of a reverse engineering system which uses manufacturing features as geometric primitives. This approach has two advantages over current practice. The resulting models can be directly imported into feature- based CAD systems without loss of the semantics and topological information inherent in feature-based representations. In addition, the feature-based approach facilitates methods capable of producing highly accurate models, even when the original 3-D sensor data has substantial errors.
In the paper by Alexandre Durupt1, Sébastien Remy and Guillaume Ducellier on (KBRE) Knowledge Based Reverse Engineering for Mechanical Components focuses on Reverse Engineering (RE) in mechanical design, RE is treated an activity which consists in creating a full CAD model from a 3D point cloud. The aim of RE is to enable an activity of redesign in order to improve, repair or update a given mechanical part.
Nowadays, CAD models obtained using modern software applications are generally “frozen” because they are sets of triangles of free form surfaces. In such models, there are not functional parameters but only geometric parameters. This paper proposes the KBRE (Knowledge Based Reverse Engineering) methodology which allows managing and fitting manufacturing and/or functional features. Specific geometric algorithms are described. They allow extracting design intents in a point cloud in order to fit these features.The work done by Jian Gao, Xin Chen, Detao Zheng, Oguzhan Yilmaz in Adaptive restoration of complex geometry parts through reverse engineering application proposes a defects-free model-based repair strategy to generate correct tool paths for build up processand machining process adaptive to each worn component through the reverse engineering application. Based on 3D scanning data, a polygonal modelling approach is introduced in this paper to rapidly restore worn parts for direct use of welding, machining and inspection processes. With this nominal model, this paper presents the procedure to accurately define and extract repair error; repair volume and repair patch geometry for the tool path generation, which is adaptive to each individual part. The tool paths are transferred to a CNC machine for the repairing trials.
Further research work is performed on repair geometry extraction algorithm and repair module development within the reverse engineering environment.The paper presented by L. Li, N. Schemenauer, X. Peng, Y. Zeng, P. Gu is a reverse engineering system for rapid modelling and manufacturing of objects with complex surfaces. The system consists of three major parts: the 3D optical digitizing system, the surface reconstruction software and an FDM rapid prototyping machine. The optical digitizer utilized a white-light source for image acquisition that makes this technology cost-effective,
fast in image acquisition and portable for various applications. The specially designed software system processed the image data cloud acquired by the digitizer which includes the 3D data pre-processing by creating triangle meshes from range images. The vertices of newly created range surfaces were also associated with weights. The range surfaces were then registered by minimizing the weighed least-square distance between the points on the overlapping portion of two surfaces.
THE TYPICAL REVERSE ENGINEERING PROCESS CAN BE SUMMARIZED IN FOLLOWING STEPS:
1. Physical model which needs to be redesigned or to be used as the base for new product.
2. Scanning the physical model to get the point cloud.
The scanning can be done using various scanners available in the market.
3. Processing the points cloud includes merging of points cloud if the part is scanned in several settings.
The outlines and noise is eliminated. If too many points are collected then sampling of the points should be possible.
4. To create the polygon model and prepare .stl files for rapid prototyping.
5. To prepare the surface model to be sent to CAD/CAM packages for analysis.
6. Tool path generation with CAM package for suitable CNC machine manufacturing of final part on the CNC machine.
The Roland Modella lpx-600 laser scanner is a medium sized scanner used to scan object of maximum height of around 150 mm and diameter of 120 mm. It operates with interface of computer with software Dr. Picza which helps in setting up the scanning parameters and also shows the scanning process. It stores the scanned file in .stl format. The scanner is shown in Fig.4.6.
Fig. 4.6 Roland Modella LPX-600 Laser scanner
Fig.4.7 Modella software setting for scanning Once the scanned image of object is obtained using scanner it is exported into .stl format shown in Fig.4.8.
The parameter set in the above software decides the quality of scanned image. As the time for scanning increases the quality of scanned image improves. The software used for the purpose is provided by Roland Lpx scanner named Dr. Picza shown in Fig.4.7.
Fig. 4.8 .stl image file of scanned component OBTAINING THE SOLID GEOMETRY FROM THE POINT CLOUD DATA:
Figure 4.9 shows a Rapidform software window which is used for converting the point cloud data in CAD model. The original .stl data is scattered and contains some noise around the boundary of model. The noise creates a problem while generating a solid model so it has to be cleaned from the data. Rapidform software has features which help to point out the noise from the data and with the help of noise reduction tool the noise is reduced. Then a clean .stl data obtained which can be used for further processing.
The scanned image is imported in Rapidform software which helps to extract geometry from the .stl file or point cloud data shown in Fig.4.9 to Solid geometry.
The main problem with the software is that it cannot directly save the file in .STEP or .IGES format for that we have to transfer the file to solidworks software and do the necessary changes which can be saved in any format required. Once the three dimensional geometry is
ready we can use it for further purpose of CAM and CAE operations. The captured point cloud data was converted into polylines and the file was transferred to .IGES file format. Finally the model is converted into solid model, the cross section of which is showed in Fig.4.10
Fig. 4.10 Solidwork model of scanned component Analysis & Optimization of impeller
The analysis of part is done in two steps first is Computational fluid dynamic and then Static analysis.
Finite Element Analysis (FEA) is done in order to solve problems such as stress, heat flow, vibration and other fields for analysis. ANSYS is used for general purpose Finite Element Analysis, this enables user to perform strain and stress analysis for the given part. Thus, in this case study we have successfully completed.
1. 3 D scan and reconstruction of geometry of damaged component
2. Developed CAD model and clean up the geometry of the component.
3. The analysis of component was done using ANSYS Static structural analysis. It helps to find whether the Model will work in specified conditions.
The steps involved in analysis Model:
For analysis purpose water model of impeller has to be
divided into small portions which are done with the help of mesh and at each point the calculations are carried out which shows the ultimate behaviour of the water model of impeller for the applied conditions. In this step the water model was converted in mesh with fine structure.
So once the command is given Software automatically generates the mesh on object. Details such as fine medium or coarse mesh have to be selected. More the mesh is fine more accurate results can be considered butat the same time the calculation time is increased.
The meshing of the water model of impeller is shown in figure 6.3.
Fig.6.3 Meshed model of solid CFD model
Fig.6.4 CFD model of pump (with impeller blades) Setup:
After meshing of component was completed it was exported to Setup module. Here the boundary conditions and input conditions for the model were given. The inlet was denoted with notation “IN” and opening was detonated with “OUT”. Rest of the body was recognized as wall. The impeller was given RPM as per required.
Water was considered as Default liquid medium. The completed boundary condition of the part is shown in Fig.6.4.
Solution:
Once the boundary and inlet outlet conditions were given, then model is ready for solution. The CFX solver is used for solving the problem, depending on complexity of geometry and mesh size the solution time varies.
RESULTS A. Pressure:
1. without any modification of geometry:
It can be observed from the Fig.6.5 that pressure is increased at the inner edges of blade. So it results in clogging of water at the inner edges of impeller so fillet of 15 mm was provided at inside edges of impeller and calculations were again carried out.
Fig.6.5 Pressure contour for impeller without
modification
Fig.6.6 pressure contour for impeller after fillet of 15
mm is provided
2. with fillet at inner edge:After providing fillet of 15 mm at inner edges it was seen that there was decrease of pressure at inner edges of impeller which can be seen in Fig.6.6.
3. with side fillet and inner edge fillet:
From Fig.6.6 it is seen that there is pressure at the outer edges of blades hence the outer edges were provided with chamfer of 2 mm. which generates the curved profile at the edges. After carrying out CFD analysis the results presented in Fig.6.6 show that the pressure at the outer edge has reduced as compared to Fig.6.7
Fig.6.7 pressure counter for impeller with inner edge
fillet and side edge fillet
Fig.6.8 Velocity vector for impeller without any modification
6.6.6. B. Velocity:
1. without any modification of geometry:
It is observed from Fig.6.8 that the velocity vector is scattered. Due to this the overall flow rate decreases.
with fillet at inner edge:
Compared to Fig.6.8 the velocity vector is in order which ultimately results in increase of flow rate of fluid as seen in Fig.6.9.
6.9 velocity vector for impeller with fillet at inner edge and side fillet inner edge fillet with side fillet and inner edge fillet:
Comparing with Fig.6.9 the velocity vector is in order which ultimately results in increase of flow rate of fluid as shown in Fig.6.10.
To avoid the wear of the edge chamfer of 2 mm was
provided at the ends of blades. As the neck of the impeller was showing concentrated stress it can be overcome by providing a round fillet. After making the necessary changes the blade was capable of withstanding the design load. Once fluid analysis is done in order to increase its efficiency of water from the pump which can be observed from Fig.6.5 to Fig.6.10.
STATIC ANALYSIS:
Finite Element Analysis (FEA) is done in order to solve problems such as stress, heat flow, vibration and other fields for analysis. ANSYS is used for general purpose Finite Element Analysis, this enables user to perform deformation of component, strain and stress analysis for the given part.
Geometry:
After the damaged impeller was scanned in scanner and exported in .stl file format. The solid model was generated using Rapidform software which accepts imported .stl data file and exports in other editable formats. The component was rebuilt and saved in solidworks for further use. Solidworks is based on Parasolid modeller which utilizes a parametric feature- based approach for creating models and assemblies. So in ANSYS workbench for geometry module the part was imported in .IGES format shown in Fig.6.11.
Fig 6.11 Solid works model in IGES format
Fig.6.12 Meshed impeller
Model:
For analysis purpose impeller has to be divided into small portions which are done with the help of mesh and at each point the calculations are carried out which show the ultimate behaviour of the component for the applied conditions. The body was converted in mesh with fine structure. So once the command is given Software automatically generates the mesh on object shown in Fig.6.12.
Setup:
Once meshing is done then impeller is ready for applying boundary conditions as shown in Fig.6.13. For static study on impeller parameters were considered relating to its working condition. In general working of pump a pressure of around 5- 6 bar is built up inside the pump housing. So the pressure of 2 bars was applied on both sides of impeller on its blades. Then motor was run at around 1500 rpm i.e. nearly equal to 150 rad/s. The impeller was held at centre using cylinder support joint.
Fig.6.13 Setup of load & boundary conditions
Fig.6.14 Deformation of impeller
Solution:After applying boundary conditions for the component. It was solved using ANSYS solver. The solving time depends on size of geometry and also on mesh structure; finer the structure more is the calculations time.
RESULTS:Calculations were carried and results were displayed with following parameters.
6.7.5.a. Total Deformation- The maximum deformation is found 3.59992e-6 m at the end of the blades as shown in Fig. 6.14
6.7.5.b. Equivalent (Von –Misses) stresses: The minimum and maximum value of stress is obtained 37835 Pa and 2.2015e+007 Pa as shown in Fig.6.15.
Fig.6.15 Equivalent (Von –Misses) stresses
Fig 6.16 Shear stress developed in component 6.7.5.c. Shear stress:
The minimum and maximum value of shear stress is found to be -8.5403e+006 Pa and 9.222e+006 Pa as shown in Fig.6.16.
The static analysis shows us maximum deformation at the outer edges of blades which can result in wear of the edges. To avoid this chamfer of 2 mm was provided at the ends of blades. As the neck of the impeller was showing concentrated stress it can be overcome by providing a round fillet. After making the necessary changes the blade was capable of withstanding the design load. Once fluid analysis was done, static analysis was done in order to increase its efficiency of water from the pump.
III. RESULTS AND DISCUSSIONS
After doing CFD Analysis of fluid part of the impeller the pressure are increased at the inner edge of the blade.
And further, doing necessary changes the following results are found.
Pressures at inner edge are decreasing as per modifications:
Without any modification pressure is found to be 9.478 e+004 Pa
With fillet of 15 mm at inside edge then pressure is found to be 5.961 e+004 Pa
With fillet of 15 mm at inside edge & 2 mm fillet at outer edge then pressure is found to be 5.786 e+004 Pa.
Velocity Vectors are increasing as per modifications: Without modifications velocity is found to be 1.122 e+000 Pa
With fillet at inside edge of 15 mm then velocity is found to be 1.227 e+000 Pa With fillet at inside edge &
outer edge then velocity is found to be 2.779 e+000 Pa.
After doing Static Analysis of Impeller total deformation is found to be 0.0035 mm at the end of the blades.
Minimum Von-misses stress is found to be 37835 Pa and maximum Von-misses stress is found to be 2.2015e+007 Pa.
Minimum shear stress is found to be -8.5403e+006 Pa and maximum shear stress is found to be 9.222e+006 Pa.
IV. CONCLUSIONS
The work done till now shows how reverse Engineering can be used for worn out or damaged parts whose availability is a problem, in such cases as there is no documentation or drawing available prior so everything has to be done from the starting phase. Reverse engineering plays a vital role in providing a digital data for CAD CAM & CAE applications. As the basic data is recovered by Reverse Engineering process it can be used further for different procedures. The main advantage is that once the CAD model of the component is obtained it can be used for analysis and design optimization which proves to be beneficial in developing any product from market point of view. It is shown that the ANSYS Workbench environment can be used very effectively to realize any parametric optimization.
REFERENCES:
[1] Ali, N.S., “Reverse Engineering of Automotive Parts Applying Laser Scanning and Structured Light Techniques”, Uni. of Tennessee, Knoxville, pp.1–3, (2005).
[2] Cox, G., Martin, R.R., Varady, T., “Reverse Engineering of Geometric Models – An Introduction”, Computer and Automation Research journal pp. 1-4,(1996).
[3] L. Li, N. Schemenauer, X. Peng, Y. Zeng, P. Gu,
“Reverse engineering of complex objects”
Advances in Manufacturing Science and Technology Vol. 35, No. 2, 2011
[4] Fudos I. “CAD/CAM Methods for Reverse Engineering: A Case Study of Re-engineering Jewelry”, University of Ioannina, Computer- Aided Design & Applications, Vol. 3, No. 6, pp 683-700,(2006).
[5] Langbein, F. C., Marshall, A. D., Martin, R. R.
“Numerical Methods for Beautification of Reverse Engineered Geometric Models”. In:
Proc. Geometric Modeling and Processing, IEEE Computer Society, Los Alamitos, CA, pp. 159- 168 (2002).
[6] Literature referred from website
http://texelq.com/reverse-engineering/dated 4-1- 2013
[7] R. A. Jarvis, A Perspective on Range Finding Techniques for Computer Vision, IEEE PAMI, Vol. 5, No. 2, (1983) pp 122-139
[8] S. Motavalli, B. Bidanda, A Part Image Reconstruction System for Reverse Engineering of Design Modi_cations, Journal of Manufacturing Systems , Vol. 10, No. 5, (1991) pp 383-395
[9] J. P. Moss, A. D. Linney, S. R. Grindrod, C. A.
Mosse, A Laser Scanning System for the Measurement of Facial Surface Morphology, Journal of Optics and Lasers in Engineering, Vol.
10, (1989) pp 179-190
[10] A. Modjarrad, Non-Contact Measurement Using a Laser Scanning Probe, SPIE, Vol. 1012 In- Process Optical Measurements (1988) pp 229- 239
[11] I. Moring, T. Heikkinen, R. Myllyla, Acquisition of Three- Dimensional Image Data by a Scanning Laser Range Finder, Journal of Optical Engineering, Vol. 28, No. 8, (1989), pp 897-902 [12] R. A. Jarvis,A Laser Time-of-Flight Range
Scanner for Robotic Vision, IEEE PAMI, Vol. 5, No. 5, (1983), pp 505-512
[13] P. W. Will, K. S. Pennington, Grid Coding: A Novel Technique for Image Processing, Proceedings of the IEEE, Vol. 60, No. 6, (1972), pp 669-680
[14] Y. F. Wang, J. K. Aggarwal, 3D Object Description From Stripe Coding and Multiple Views, Proceedings of the 5th Scandinavian Conference on Image Analysis, Vol. 60, No. 6, (1987), pp 669-680
[15] H. K. Nishihara, Practical Real-Time Imaging Stereo Matcher, Journal of Optical Engineering, Vol. 23, No. 5, (1984), pp 536-545
[16] J. L. Posdamer, M. D. Altschuler, Surface Measurement by Space-encoded Projected Beam Systems, Journal of Computer Graphics and Image Processing, Vol. 18, (1982), pp 1-17 [17] R. J. Woodham, Photometric Stereo: A
Reectance Map Technique for Determining Surface Orientation from a Single View, Image Understanding Systems and Industrial Applications, Proc. SPIE 22nd Annual Technical Symposium, San Diego, California, Vol. 155, (1978) pp 136-143
[18] A. Rockwood and J. Winget, Three-Dimensional Object Reconstruction from Two-Dimensional Images , this special issue, Computer-Aided Design, Vol. 28, No (1996)
[19] Y. L. Xiong, Computer Aided Measurement of
Pro_le Error of Complex Surfaces and Curves:
Theory and Algorithm, International Journal of Machine Tools and Manufacturing, Vol. 30, No.
3, (1990), pp 339
[20] K. C. Sahoo, C. H. Menq, Localization of 3-D Objects Having Complex Sculptured Surfaces Using Tactile Sensing and Surface Description, Journal of Engineering for Industry, Vol. 113, (1991), pp 85-92
[21] C. Butler, Investigation Into the Performance of Probes on Coordinate Measuring Machines, Industrial Metrology, Vol. 2, No. 1, (1991), pp 59-70
[22] S.Watanabe, M. Yoneyama, An Ultrasonic Visual Sensor for Three-Dimensional Object Recognition Using Neural Networks, IEEE
Transactions on Robotics and Automation, Vol.
8, No. 2, (1992), pp 240-249
[23] T. Tsujimura, T. Yabuta, T. Morimitsu, Shape- Reconstruction System for Three-Dimensional Objects Using an Ultrasonic Distance Sensor Mounted on a Manipulator, Transactions of ASME, Vol. 111, (1989), pp 180-186
[24] Eyup Bagci, “Reverse engineering applications for recovery of broken or worn parts and re- manufacturing: Three case studies”. Advances in Engineering Software 40 (2009) 407– 418.
[25] Bhupendra Raghuwanshi, Viswash Tomar
“Computer-aided Reverse engineering for replacement of part: A case study" International Journal of Mechanical Engineering and Research Volume 1 Issue 1 (Page, 1-5).
