STUDY OF PISTON SLEEVE MANUFACTURED BY SAND CASTING PROCESS TO REDUCE REJECTION RATE USING SIMULATION SOFTWARE

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1 International Journal of Mechanical and Production Engineering Research and Development (IJMPERD) ISSN Vol. 3, Issue 2, Jun 2013, TJPRC Pvt. Ltd. STUDY OF PISTON SLEEVE MANUFACTURED BY SAND CASTING PROCESS TO REDUCE REJECTION RATE USING SIMULATION SOFTWARE ABSTRACT P. J. MANDALIYA & J. T. DAVE B.H. Gardi College of Engineering & Technology, Gujarat Technological University, Rajkot, Gujarat, India Gating layout of a casting is an important aspect of tooling development. It inverse decision regarding part orientation in mould, part line, cores, cavity layout, feeder, neck and gating system. An improper method layout leads either to poor quality or low yield, which affect the productivity. Gating design is mostly carried out manually, using 2D drawing of cast part. Then tooling fabricates the sample casting which undergo 3-4 trials, which involves lot of production cost in the form of wastage of man power, time and hamper the day to day schedule of the particular production. Computer simulation provides a clear insight regarding the location and extent of internal defects, ensuring right casting as first time and every time. The casting simulation software is used to study the simulation behavior of casting. It is expected that this work will be of immense important equally to the academicians, as well as, to the industrial design engineers. Final product should confirm the design requirement without internal defects. KEYWORDS: Sand Casting, Shrinkage Defect, Simulation INTRODUCTION In manufacturing casting is the one of the most economical processes. Metal casting involves pouring molten metal into a mould containing a cavity of the desired shape to produce a metal product. The casting is then removed from the mould and excess metal is removed, often using shot blasting, grinding or welding processes. The product may then undergo a range of processes such as heat treatment, polishing and surface coating or finishing and inspection. Figure 1: Cross Section of Typical Casting SOLIDIFICATION PHENOMENA OF COMMON CAST METALS One of the most important stages of manufacture of casting is the formation of solid casting from or molten metal phase. When poured into mold cavity. The various complex transformation that occurs during the process including physical, chemical, metallurgical and geometric changes, influence the quality and the cost of the final product of the casting. The casting process is essential solidification of liquid metal in the mold cavity such a phase change from liquid from solid state involves the phenomena

2 162 P. J. Mandaliya & J. T. Dave like changes in fluidity, volumetric shrinkage, segregation evolving of gases absorbed and the size of the grains which have profound influence on the quality of the final casting obtain a proper understanding of solidification mechanism help is avoiding major casting defect as like miss runs, cold shuts, shrinkage cavity, pin-hole porosity, hot tears, cracks, dissertation, and poor mechanical properties. SOLIDIFICATION DEFECTS Solidification defects cold lead to two different manifestations of porosity, localized shrinkage porosity and Micro porosity. Localized shrinkage porosity is caused by insufficient feeding of the alloy during solidification. As the alloy solidify, it also shrinks by over one percent and a sufficient supply of molten alloy is required during this phase to counteract reduction in the volume caused by the shrinkage. If the sprue is not properly designed and implemented then it may solidify before the feeding is complete thus preventing a continuous supply of molten alloy. This type of defect usually occurs close to the sprue-casting junction. Micro porosity is also caused by solidification shrinkage, but generally happens in fine grain alloys when the solidification is too rapid for the micro voids to segregate. This in turn is caused the mould or casting temperature being too low. CASE STUDY In one of the industry, they are manufacturing an automobile part called piston sleeve in which they have found the shrinkage defect after the machining process. Due to shrinkage defect rejection rate is near about 13%, which could not be tolerable as well as profitable. So that they wanted to reduced rejection rate by reducing shrinkage defect. Figure 2: Casting Part Figure 3: Shrinkage Defect Found after Machining

3 Study of Piston Sleeve Manufactured by Sand Casting Process to Reduce Rejection Rate Using Simulation Software 163 Table 1: Information about Casting Part 1 Material Grade ASTM Total pouring time 7 to 8 minute 3 Pouring Temperature 1380 C to 1390 C 4 No. of patterns 4 5 Solidification time 15 to 20 minute 6 Type of core Resin Coated sand core 7 Density 7.1 sq. cm 8 Bunch weight 75 Kg 9 Casting weight 12.2 Kg 10 Function of part Automobile sector 11 Moulding box size 24 x 26 x 6 inch. 12 Chemistry of component C- 3.55% to 3.60% Si- 2.45% to 2.50% Mn-0.25%, Cu-0.35% S-0.001%, P-0.020% Mg-0.045% In casting foundry, Manufacturing of sound casting is the main aim for foundry men. To achieve this number of trial casting has carried out on the shop floor and one repetition can take up a week or more, which affects the regular production. Many researchers reported that about 90% of the defects in castings are due to wrong design of gating & risering system and only 10% due to manufacturing problems. Figure 4: Gating System Used for Production There are several possibilities of shrinkage defect to arise. In which one possibility is to design a wrong gating system. A little consideration shows that to reduce the shrinkage defect in this automobile part, some modifications are needed in the design of gating system. There are some proposed designs for reducing the shrinkage defect. As shown in Figure 5, one possible solution is to put a rectangular pad between the casting body surface and ingate. The thickness of the pad is 2.25 mm so that after the solidification phenomena happened, shrinkage shifted to rectangular pad from the casting part and defect can be eliminated. This possible solution can be implemented or not that can be proved with the help of simulation software. Figure 5: Modified Design of Gating System

4 164 P. J. Mandaliya & J. T. Dave Simulation is the tool for virtual foundry in which without taking any actual trial and error method predictions of the major defects can be possible. Casting simulation saves the time of production as well as cost. ANALYSIS FOR INITIAL GATING DESIGN There are six basic steps for doing the simulation in sand casting process to predict the casting defects. Step 1- create CAD model of gating design. Step 2- Import the CAD model in simulation software Step 3- Pre processing Step 4- Apply boundary conditions Step 5- Post processing Step 6 Result and analysis Figure 6: Meshing of Mould and Gating Design After creating the CAD model, import the CAD file in simulation software in.iges or.stl format. Define number of nodes, number of materials, and number of elements for pre-processing. Element type is tetrahedral. Make interface between the mould and casting (Figure 7). Apply boundary conditions. Figure 7: Interfaces between Mould and Casting Air cooling to all mould surfaces Inlet velocity to pouring cup

5 Study of Piston Sleeve Manufactured by Sand Casting Process to Reduce Rejection Rate Using Simulation Software 165 Inlet temperature to pouring cup Define process for filling (gravity filling) Initial condition for mould Initial condition for casting Figure 8: Uneven Solidification Starts Figure 9: Shrinkage Prediction Figure 9 shows that the purple colour indicates the percentage of shrinkage in intensity graph. Generally in S.G. Iron shrinkage allowances is near about 1.2 %. The results shows after simulation of gating system that possibility of shrinkage is % which is more than given shrinkage allowances. So that modification in gating design is required.there is change in ingate location and add the extra padding to reduce the shrinkage defect. Same procedures are being done simulating modified gating system design and get the new results which are shown below. Figure 10: Interfaces between the Mould and Casting

6 166 P. J. Mandaliya & J. T. Dave Figure 11: Solidification Behavior Figure 11 shows that modification has been done in gating design; the problem uneven solidification can be eliminated and possibility of shrinkage defect also could be reduced. The modified design will be helpful to optimize the material also. Before modification in gating system design the weight of casting part is 12.2 kg and after modification the casting weight is 11.7 kg. So that material can also be optimized. Figure 12: Cross Section of Simulated Part CONCLUSIONS It can be concluded that simulation software is the powerful tool for prediction the casting defects and also can be helpful to save the time and money of the foundry owner. Modification in gating system by adding extra padding will be helpful to reduce shrinkage defects and improves the casting productivity and yield. REFERENCES 1. B. Ravi and M.N. Srinivasant, Casting solidification analysis by modulus vector method. International journal of Cast metals Res., Vol.9, pp. 1 to 7, B. Ravi, R.C. Creese, D.Ramesh, Design for casting- A new paradigm for preventing potential problems., Transaction of the American Foundry Society, 107, pp. 1 to 11, A. Reis, Y.Houbaert, Zhian Xu, Rob Van Tol, Modelling of shrinkage defect during solidification long and short freezing materials., Elsevier- journal of material processing technology, Vol.202,, pp. 428 to 434, Dr. B. Ravi, Computer Aided Casting Design past, present and future., IFC, pp. 1 to 16, 1999.

7 Study of Piston Sleeve Manufactured by Sand Casting Process to Reduce Rejection Rate Using Simulation Software Dr. B. Ravi, Durgesh Joshi, Feedability analysis and optimization driven by casting simulation., Indian Foundry Jouanal, pp 1 to 14, Zheng Hongliang, Sun Yeche ng, Zhang Ning, Zhang Kai and Tian Xuelei, Shrinkage porosity simulation of spheroidal graphite iron castings based on macro- micro models., Materials Science Forum, VOl. 689, pp 190 to Rabindra Behera, Kayal.S., Sutradhar. G., Solidification behavior and detection of hotspots in aluminium alloy castings : Computer Aided Analysis and experimental validation., International Journal of Applied Engineering Research, Vol.1, pp. 715 to 726, John Campbell Castings, Elsevier, a division of Read Elsevier India Private Limited, pg T V Ramana Rao, Metal Casting Principles and Practice, New Age International (P) Ltd., pg. 15 to 121, 1999.

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