Improving Sand Casting For Small Scale Foundry
The aim of the present work is to improve sand casting products in a small foundry shop due to casting defects in sand casting process using a statistical tool namely Taguchi method and a computer aided simulation technique. Conventional techniques require a larger number of trials for checking outputs when the variety of input conditions increase and this problem can be reduced using this two techniques. In this investigation, the various casting process parameters such as moisture content (%), green compression strength (g/cm2) and permeability number are considered and organized according to Taguchi L18 orthogonal array. Taguchi approach is utilized to find out the most significant control factors which will reduce casting defects. Besides, the percentage contribution of process parameter has been determined using statistical Analysis of variance (ANOVA). Finally, the general regression equation is formulated and better cast product is obtained with less defects and it is validated by means of confirmation test. It is observed from experimental trials in foundry shop that average value of minimum casting defect is 3.1% for aluminum flywheel. Not only that in this thesis an attempt has been taken to redesign gating and feeding system for producing a casting free from defects. Defects such as shrinkage porosity, improper solidification, air entrapment, mold erosion are directly related with gating and feeding system design. Number of iterations using casting simulation software are performed for mold filling and solidification analysis to reduce the rejection level in cast component. With new gating and feeding system design improvement in casting yield (about 15%) is observed.
1.1 Background of study
Sand casting is one of the versatile methods of metal shaping because it is used most frequently for intricate shape casting practically both of ferrous or nonferrous material. Further, the necessary tools required for sand casting are very simple and inexpensive. For this reason it is an ideal method for trial production or production of a small lot. It consists of pouring molten metal into a sand mold cavity, allowing the metal to solidify and then breaking away the mold for getting the cast product. However, the surface finish and dimensional accuracy achieved by normal sand casting process are not adequate for final output in many cases, therefore many improvements can be done through quite modifications of casting process. Green sand casting process parameters perform a vital role for enhancing the quality of cast products. Many researchers performed their research on optimizing the value of casting process parameters to improve the quality of cast products using various techniques over the past few years. Up to now following methods are used for process design: Design of Experiments (DoE) techniques such as Taguchi approach, Response Surface Methodology (RSM), integrated approach of Taguchi approach and Response Surface Methodology (RSM), Finite Element Analysis (FEA), casting simulation techniques such as Magma 5, Quick CAST, Auto CAST X, Solid CAST simulation software’s, Artificial Neural Network (ANN), Gradient Search method [1-2].
- To establish the optimum settings of molding sand related parameters for improving selected cast component using Taguchi Method.
- To analyze filling and solidification related defects using casting simulation technique (Click2Cast).
- To measure the effectiveness of the proposed techniques through confirmation test.