DEFECT ANALYSIS OF HAND WHEEL CASTING USING COMPUTER AIDED CASTING SIMULATION TECHNIQUE

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 7, Issue 5, September October 2016, pp.46 56, Article ID: IJMET_07_05_006 Available online at Journal Impact Factor (2016): (Calculated by GISI) ISSN Print: and ISSN Online: IAEME Publication DEFECT ANALYSIS OF HAND WHEEL CASTING USING COMPUTER AIDED CASTING SIMULATION TECHNIQUE Bijendra Prajapati Asst. Professor, Institute of Engineering, Western Regional Campus, Pokhara. Hari Dhakal Assistant Professor, Nepal Engineering College, Kathmandu Mukesh Regmi Assistant Professor, Nepal College of Information Technology, Kathmandu ABSTRACT In the present casting arena, emphasis is laid on the precise and defect free casting, minimum production cost, develop the components on demand in short period of time accompanied by high yield of production for casting units & foundries. In order to achieve this level, Fish-bone diagrams and computer simulation technique are inevitably necessary. The paper studies on the shrinkage defect prevailing in the Hand wheel casting and its remedy with the help of casting simulation software ADSTEFAN. Due to the lack of standard acceptable theoretical procedures, the design processes are normally carried on a trial-and-error basis. Systematic studies & analyses are carried out to understand the reasons for occurrence of defects and suitable remedial measures are identified. Then, computer assisted casting simulation technique is used to analyze the casting defects. Shrinkage porosity analysis is performed using this technique by introduction of a new gating system design, followed by various iterations that include changing of the length of runner and introducing a riser. The results show a significant reduction in shrinkage porosity and improvement in yield. This can be of great economic value due to reduction in material consumption and less unit price for production. The proposed approach reduces the rejection due to casting defects in foundries. This will especially help SME foundries to significantly improve their quality levels. Key words: Hand wheel, Casting Simulation, Fish Bone Diagram, ADSTEFAN, Shrinkage, Yield. Cite this Article: Bijendra Prajapati, Hari Dhakal and Mukesh Regmi, Defect Analysis of Hand Wheel Casting using Computer Aided Casting Simulation Technique. International Journal of Mechanical Engineering and Technology, 7(5), 2016, pp editor@iaeme.com

2 Defect Analysis of Hand Wheel Casting using Computer Aided Casting Simulation Technique 1. INTRODUCTION One of the oldest manufacturing processes, Casting, is still extensively used to produce complicated metal shapes with little or no further machining in a very economical way. Casting is a manufacturing process by which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify [1]. There are two main consecutive stages, filling process and solidification process in casting production. Casting process design is important for production quality and efficiency. Casting quality is heavily dependent on the success of gating/riser system design, which currently is conducted mainly relied on technicians experience. Therefore there is a need for the development of a computer-aided casting process design tool with CAD, simulation, and optimization functions to ensure the quality of casting [2]. With regards to the project work, defect analysis of Hand wheel casting has been selected. Hand wheel can be defined as a wheel worked by hand. Hand wheels are used to adjust a variety of machine functions and are great for any application where adjustments need to be made via a turning mechanism. Out of different casting processes, shell molding process is best suited casting process to manufacture Hand wheels since shell molding offers better surface finish, high productivity and precision of the process. No process is full-proof or perfect. Casting process also has some shortcomings namely casting defects. That s why Casting process is also known as process of uncertainty. An undesired irregularity in the metal casting process is termed as casting defect. Even in a completely controlled process, defects are found in casting. Such defects challenge explanation about the cause of casting defects. The complexity of the process is credited to the involvement of the various disciplines of science and engineering with casting. It is found that the cause of defects is often a combination of several factors rather than a single one. To tackle them, the methods like fish bone diagram, casting simulation technique & Campbell s 10 rules for making reliable castings have been proposed to ensure defect free castings with maximum yield. The main concern is shrinkage defect. Shrinkage is reducing the volume of the casting material when metal is cooling and solidifying that produces the line, holes in the casting, it s called the shrinkage defect. For the casting simulation of Hand wheel, ADSTEFAN software has been employed. ADSTEFAN stands for Advanced Solidification Technology for Foundry aided by numerical Simulation. ADSTEFAN is casting simulation software that accurately simulates the entire casting process providing a quick and reliable solution for real casting problems. Casting simulation should be used when it can be economically justified for at least one of the following three reasons: Quality enhancement by predicting and eliminating internal defects like porosity Yield improvement by reducing the volume of feeders and gating channels per casting Rapid development of a new casting by reducing the number of foundry trials [3]. 2. OBJECTIVES The main objective is to minimize the rejections of the Hand wheel casts through defect analysis by using casting simulation software namely ADSTEFAN. Apart from this, the secondary objectives of the study are Selection of appropriate process variables such as Pouring temperature, Filling time, Shell mold, Chemical property of the molten metal for simulation and others. Develop a 3D model of Hand wheel pattern for simulation by ADSTEFAN software along with mold filling & solidification analysis. Investigate Effect of gating system to overcome shrinkage defect. Find out the reduction in shrinkage defects & improvement in Yield after applying modifications in design & use of casting simulation software editor@iaeme.com

3 Bijendra Prajapati, Hari Dhakal and Mukesh Regmi 3. LITERATURE REVIEW An extensive literature review has been done with few of the selected papers related to Casting defects & Casting simulation technique. The main focus areas of these papers are the occurrence of shrinkage defects in the casting piece and the application of the casting simulation technique to optimize the defects effectively. These papers discuss on the various types of defects that are studied for different casting processes, the materials used, methodologies involved, different types of casting simulation software s used, different parameters considered for the defect analysis and so on. Swapnil A. Ambekar and Dr. S. B. Jaju [2] have studied about the need of foundry to manufacture defect free castings with minimum production cost. Due to the lack of existing theoretical procedures the designing processes are normally carried on a trial-and-error basis. Different optimisation approaches like Multi-Objective Evolutionary Algorithm (MOEA), Theory of Inventive Problem Solving (TRIZ), and Design of Experiments (DOE) have been discussed. It is concluded that with a more reasonable gating system obtained by analysis of casting simulation results, the need can be achieved with other added benefits. Dr. B. Ravi [3] has studied the benefits of casting simulation (both tangible and intangible), bottlenecks (technical and resource related) and some best practices to overcome the bottlenecks. It has explained all five stages of simulation projects in detail. Major concerns relating to simulation have been properly addressed & illustrated with industrial examples. Bhupendra [4] studied & found that about 90% of the defects in castings are due to wrong design of gating & risering system and only 10% due to manufacturing problems. Casting simulation process can be used to solve those problems. He studied detection of hot spots in casting of Release Bearing Housing with the help of casting simulation software called ProCast. The simulated results are also compared with the experimental works. Vipul Vasava and Dhaval Joshi [5] have studied about the Shrinkage cavity that is detrimental to mechanical performances of casting parts. They have found that Design engineers often use large safety factors in many designs due to insufficient understanding of quantitative effects of shrinkage cavity defects. Harshwardhan et al. [6] have studied that the methods layout of a casting is an important activity in tooling development. It involves critical decisions regarding part orientation in mold, parting line, cores, cavity layout, feeders, feed aids and gating system. Optimization of methoding parameters with the help of simulation is discussed and it is tried to minimize efforts and avoid conventional trial and error practice. The simulation model is built to assess the methoding parameters using Auto Cast simulation software. Yeh-Liang Hsu and Chia-Chieh Yu [7], In this research, a casting simulation software is used to simulate the casting process of aluminium wheels. The casting simulation is done iteratively until the mold temperature converges to a stable temperature with the help of ProCast. Shrinkage Index (SI) is defined to describe quantitatively the level of casting shrinkage from casting simulation. This paper also discusses the influence of cooling process parameters on SI, including initial mold temperature, and geometry of the wheel, which verifies engineers empirical data. They concluded that this iterative simulation process and SI can be used to predict the casting quality of aluminium wheels and to find the optimal parameters of the casting process. The review of literature has provided lots of information & insights about the defect analysis, various methodologies related to defect analysis, different causes and remedies of the casting defects and various types & working of the casting simulation softwares. 4. PROBLEM STATEMENT The casting defect in Hand wheel has been considered for the study. The problem belongs to SME, Matruchaya Engineering that manages to get the order of hand wheels as per the drawing specifications. Following the shell casting process, the hand wheels have been manufactured but the main concern is the occurrence of shrinkage defect as shown in the figure editor@iaeme.com

4 Defect Analysis of Hand Wheel Casting using Computer Aided Casting Simulation Technique It was noticed that these defects are frequently occurring at particular locations and are of the irregular shape & size. The defects are found inside the drilled portion of hand wheel which are otherwise invisible before drilling. Its occurrence is found to be about in every 100 casts. Since, the rejection is so high, it is to be solved to attain 3-5 defects. 5. PROPOSED STUDY In order to obtain remedy, the project work has been destined to study the following perspectives: Finding the root cause of occurrence of defects in the rejection of casting Taking necessary steps to reduce the defects and to improve the casting yield Techniques like cause-effect diagrams and casting simulation technique to be used 6. MATERIALS & METHODOLOGIES Though various types of metals like cast iron, grey cast iron, S G iron and others can be used, based on the requirement to the respective requirement, S G iron 400/12 has been selected. Essentially ductile cast iron consists of graphite spheroids dispersed in a matrix similar to that of steel. For the defect analysis of the hand wheel, two methods have been employed namely Fish bone diagram and casting simulation technique. Third method has been proposed to ensure proper foundry practices for reliable castings Fishbone Diagram/ Cause-Effect Diagrams Ishikawa diagrams (also called fishbone diagrams, herringbone diagrams, cause-and-effect diagrams, or Fishikawa) are causal diagrams created by Kaoru Ishikawa (1968) that show the causes of a specific event. Common uses of the Ishikawa diagram are product design and quality defect prevention, to identify potential factors causing an overall effect. Each cause or reason for imperfection is a source of variation The possible causes are: Volume contraction of the metal, either from liquid contraction of the melt or from contraction during phase change from liquid to solid Insufficient feed metal in defect areas. Improper Gating, feeding system and part design Aggressive mixing, Improper pouring, Moisture contamination, Improper ramming of mold box [8] Casting Simulation Not all defects can be accurately simulated. Solidification shrinkage defects (macro, micro and centerline shrinkage) can be predicted fairly accurately. Flow-related defects (cold shuts and blow holes) can be simulated but may not always match actual observations. Cooling stress related defects (cracks), microstructure and mechanical properties are difficult to simulate, and extensive calibration experiments may be needed for practical use [3]. The figure 2.1 shows the systematic procedures that leads to casting simulation and ultimately to optimization of the process Campbell s 10 Rules for Making Reliable Castings The guidelines for effective production of reliable castings continue to evolve. A significant increase and improvement in the understanding of the casting process has led to new insights and criteria. Now ten rules have been identified that incorporate the latest technology for the production of reliable castings. Rule 1: Good-Quality Melt Rule 2: Liquid Front Damage Rule 3: Liquid Front Stop 49 editor@iaeme.com

5 Bijendra Prajapati, Hari Dhakal and Mukesh Regmi Rule 4: Bubble Damage Rule 5: Core Blows Rule 6: Shrinkage Damage Rule 7: Convection Damage Rule 8: Segregation Rule 9: Residual Stress Rule 10: Location Points [10] 7. DEFECT ANALYSIS As soon as the defect has been identified properly, all the causes must be studied in order to identify the true root causes of the problem. Until and unless the causes of defect are identified, the problem cannot be solved out. This should be a team effort that involves study of foundry related books, journals and advices from foundry experts to uncover all possible contributions to know the reasons behind defect and the mitigating factors that lead to corrective action. The defect analysis involves the application of computer simulation technique in both existing and modified pattern to achieve the objective. That s why the stages of casting simulation technique have been employed using ADSTEFAN software as follows: Step1: 3D Modeling of Hand wheel & Pattern Step 2: Meshing Step 3: Define Process for Filling Step 4: Material Properties setting Step 5: Fluid flow settings Step 6: Analysis in Filling Step 7: Analysis of solidification Step 8: Analysing result The simulation program was installed at Abhishek Alloys, Belgaum. The material database was defined with experiments to suit the melt used in the foundry. The experiments were carried out with shell castings and pattern casting accompanied with various sizes of runner, Gating system and presence or absence of feeder. A number of iterations were carried out by changing the size of runner, modifications in gating system as well as riser. The tests showed that the prediction & subsequently reduction of the casting defects depending on the type of pattern by use of the ADSTEFAN simulation software. The difference in simulated porosities between two pattern castings is shown as: 8. FOR EXISTING DESIGN The 3D Modeling of existing Pattern is shown in figure 3.1. After, the model is fed to ADSTEFAN in the form of a stp file from Solid Edge V19, meshing is performed. The casting method is set as Gravity casting. The next step is to set the material properties giving the required parameters like material type (FCD450), density (7.1 gm/cc for SG iron), Initial temp.(1450 c), volumetric shrinkage (2%) and so on. The fluid flow settings are set by software after setting fill ratio to 98% then; filling time is shown as 5.56sec. Analysis in Filling is shown in figure 3.2 wherein the uniform distribution of colour suggests no presence of unwanted gases, slags, inclusions, dross etc. Also as shown in figure 3.3, the discontinuity in the solidification suggests that certain defects may prevail in the hand wheel. Lastly, figure 3.4 shows the result as analyzed by the simulation software. It is observed that the shrinkage defects are occurring in central portion of hand wheels. It is also observed that defects occurred in two hand wheels differ in value 50 editor@iaeme.com

6 Defect Analysis of Hand Wheel Casting using Computer Aided Casting Simulation Technique i.e. values of shrinkage defect are different. As shown in figure 3.4, the shrinkage that are significant for study have value of 0.697cm 3, 0.666cm 3 and 0.002cm 3 resp. Rest two values of shrinkage are insignificant. Hence, by studying the possible causes of shrinkage defect and analysing the result of casting simulation of existing pattern, the following remedies have been proposed with help from experts, manuals and so on. Proper foundry practices, including melt preparation and mold design can reduce the occurrence of these defects. Avoid heavy isolated casting sections that are difficult to feed. Design the part with a progressive change in casting thickness Design the gating and feeding system to provide for directional solidification back to the risers. Limit the pouring temperature so that the liquid contraction is minimized. Trial & error method in optimizing Runner height/length Inclusion of riser/feeder 9. MODIFIED DESIGN Some of the changes carried out in pattern design are: Changing the size of runner: length reduced by 65mm. Changing the gating system: making the gating system symmetric as shown in figure 3.5 and adopting circular shapes of the gates & ingates for feeding the molten metal. Introduction of the riser: Riser is placed just above the center of hand wheel as shown in figure.3.5 where shrinkage defect was often found. The steps involved till analysis in filling are similar to that of existing pattern design. Only filling time is shown as 4.05sec. The figure 3.6 shows the uniform distribution of colour suggesting no presence of unwanted gases, slags, inclusions, dross etc. As shown in figure 3.7, though there is some discontinuity in solidification, the presence of feeder suggests that defects that may prevail in the hand wheel will be minimized to a greater extent. The occurrence of the shrinkage defects have been significantly reduced as shown in the figure 3.8. The shrinkages that are significant for study are cm 3 and cm 3 whereas rest two values are insignificant. The shrinkage now shown is almost negligible and this hand wheel casting is ready for production. 10. RESULTS AND DISCUSSIONS The shrinkage porosity in existing design is (Sp) 1 =( )cm 3 =1.365 cm 3 (from figure 3.4) The shrinkage in the Modified design is (Sp) 2 =( )cm 3 = cm 3 (from figure 3.8) Thus, reduction in shrinkage=99.8% This doesn t consider the shrinkage defects prevailing in places other than the hand wheel since the metal casts are going to be reused & are insignificant for the Hand wheel castings. Thus, there is significant reduction in the shrinkage defect by the use of modified design. Considering single shell molds in which two hand wheel are casted, the yield is being calculated. Density of Ductile iron=7100 kg/m3 [11] For Existing Design (Yield) 1 =(wt. of good casting/wt. of molten metal)*100% 51 editor@iaeme.com

7 Bijendra Prajapati, Hari Dhakal and Mukesh Regmi =2.05/4.877*100%=60.75% For Modified Design (Yield) 2 =(weight of good casting/weight of molten metal)*100% =2.05/3.374*100%=42.03% Improvement in Yield=18.72% Reduction in wt. of molten material/cast= =1.503kg Thus, there is also the significant improvement in the yield by using the modified design. The weights have been calculated from Solid Edge V19 using Physical properties option and for two hand wheels, the yield has been calculated. As a whole, the use of the modified design has helped to reduce the shrinkage defect significantly and improve the yield immensely by using the casting simulation software ADSTEFAN. The significant reduction in material consumption has become a boon to the SMEs, thus leading to profit increment. Figure 1.1 Shrinkage Defect in Hand wheel Figure 2.1 Flowchart of analysis of casting defects using casting simulation technique 52 editor@iaeme.com

8 Defect Analysis of Hand Wheel Casting using Computer Aided Casting Simulation Technique Figure 3.1 3D Modeling of existing pattern Figure 3.2 Analysis in Filling Figure 3.3 Analysis of solidification 53

9 Bijendra Prajapati, Hari Dhakal and Mukesh Regmi Figure 3.4 Analysing result Figure 3.5 3D Modeling of modified Pattern Figure 3.6 Analysis in Filling 54

10 Defect Analysis of Hand Wheel Casting using Computer Aided Casting Simulation Technique Figure 3.7 Analysis of solidification Figure 3.8 Analysing result 11. CONCLUSION Casting simulation and fish bone diagram are of great essence in carrying out the defect analysis. By using them, it has been possible to find out all possible causes, their effects & ultimately using that information for simulation in casting simulation software ADSTEFAN to get desired result. In practice, Casting defects are eliminated by iteratively designing casting filling (gating) system through experience and experiments, but it requires large number of shop floor trials; taking huge amount of resources (cost) and time. With the introduction of Casting simulation software along with changes in the gating design, reducing the runner length and using the feeder in pattern, it has helped to minimise the casting defects & rejections as a whole. The proposed approach reduces the rejection due to casting defects in foundries, material saving and reduction in per unit cost of production & increase in yield and ultimately profit. Casting simulation technology thus, has become a powerful tool for casting defect troubleshoot in and method optimization. It will reduce the lead time for the sample casting; improved productivity and knowledge of software can be maintained for future use and for training new engineers editor@iaeme.com

11 Bijendra Prajapati, Hari Dhakal and Mukesh Regmi 12. FUTURE SCOPE In order to continue with the defect analysis of casting, there are lots of fields for study. Some of them are mentioned below: Study of the metallurgical failures, some other defects like sand drop, extra material deposits, shell crack etc that are not taken into consideration during simulation. Study of the application of DOE methods for optimisation of various system parameters to minimise the defects. Use of sleeves, chillers etc to minimise the casting defects and uniform solidification Use of pattern less technology for the casting simulation by use of the latest casting simulation software s like solid cast, flow3d etc. ACKNOWLEDGEMENTS The author wishes to thank all Professors for their suggestions, encouragement and support in undertaking the present work. Also, the author would like to express our gratitude to A.S. Kulkarni, Proprietor, P. M. Kulkarni, QA, Matruchaya Engineering. Madhav Acharya, MD, R.D. Rathore, QA senior engineer, Abhishek Alloys, Belgaum deserve special thanks for their continuous help & support in carrying out the work successfully. REFERENCES [1] E. Paul DeGarmo, J. T. Black, Ronald A. Kohser (2003), Materials and Processes in Manufacturing (9th ed.), Wiley, ISBN pg 277 [2] Swapnil A. Ambekar, Dr. S. B. Jaju, A Review on Optimization of Gating System for Reducing Defect, International Journal of Engineering Research and General Science Volume 2, Issue 1, January 2014,ISSN [3] Dr. B. Ravi, Casting Simulation-Best Practices, transactions of 58th IFC, Ahmedabad (2010) [4] Bhupendra J. Chudasama, Solidification Analysis and Optimization Using Pro-Cast, International Journal of Research in Modern Engineering and Emerging Technology Vol. 1, Issue: 4, MAY: 2013 (IJRMEET) ISSN: [5] Vipul Vasava, Dhaval Joshi, Simulation of shrinkage Defect-A Review, International Journal of Engineering Trends and Technology (IJETT) Volume 4 Issue 6- June 2013, ISSN: [6] A. Harshwardhan Pandit, B. Uday Dabade, Optimisation: Need of today s Competitive Age A Case Study on Simulation using Autocast, International Conference on Current Trends in Technology, nuicone 2011 [7] Yeh-Liang Hsu, Chia-Chieh Yu, Computer Simulation of Casting Process of Aluminium Wheels A Case Study, JEM381 imeche 2006 Proc. Imeche Vol. 220 Part B: J. Engineering Manufacture [8] Ishikawa, Kaoru (1956), Guide to Quality Control, Tokyo: JUSE. [9] Aniruddha Joshi, Pritam Kadam, An Application of Pareto Analysis and Cause Effect Diagram for Minimization of Defects in Manual Casting Process, Proceedings of Annual International Conference IRAJ, 19th January 2014, Pune India. ISBN: [10] Campbell, John (2004), Castings Practice The 10 Rules of Castings. [11] [12] Vasdev Malhotra and Yogesh Kumar, Casting Defects: An Literature Review. International Journal of Design and Manufacturing Technology (IJDMT). 7(1), 2016, pp editor@iaeme.com