ISSN 1067-8212, Russian Journal of Non-Ferrous Metals, 2010, Vol. 51, No. 2, pp. 124–130. © Allerton Press, Inc., 2010. 124 1 1. INTRODUCTION Proper pouring techniques are required to produce castings that are defect-free. Conventional down-the- sprue pouring techniques entrain substantial quanti- ties of air, up to 30 percent of the total volume of metal poured [1]. Aluminium oxidizes readily in liquid and solid states forming aluminium oxide inclusions, and the oxidation rate is greater at molten metal tempera- tures [2]. The presence of these inclusions in the metal structure negatively affects the mechanical and physi- cal properties of casting products [3]. Vacuum casting, also called countergravity casting, is of particular interest because the sprue is filled in a non-turbulent fashion from clean metal beneath the surface of the melt [4]. Castings with far less slag and non-metallic inclusions are produced; hence castings have improved mechanical properties. In vacuum casting, a vacuum is used to draw metal up into the mould as opposed to gravity pulling metal down into the mould [5]. Every part of the mould is filled by the melt drawn by the vacuum through the permeable mould wall. The fill pipes are low cost and are dispos- able for high melting alloys. Many designs of vacuum casting equipment have been produced in recent years as prototype and actual working models. Vender Jagt and Tooley [6] have reported a two-chamber furnace 1 The article is published in the original. for low pressure vacuum casting while Kuhn and Wylie [7] reported a vacuum casting apparatus comprising a reservoir having a casting chamber and an electro- magnetic pump for pumping molten metal from the chamber into distribution vessel and mould situated above. Vacuum casting has been successfully used to pro- duce intricate components like open and enclosed shrouded impeller to a close tolerance of ±0.010 to ±0.015 on dimensions over one Inch [8]. Hoskyns [9] reported that several successful and well known com- panies are producing “high-vacuum” die-castings for prestigious high-performance products, underscoring the simplicity, reliability and cost effectiveness of the technique. The objective of this work was to design and con- struct a simple, low-cost vacuum casting equipment that will make the advantages of this casting technique more accessible particularly to small and medium scale foundries. 2. EXPERIMENTAL 2.1. Common Features of Vacuum Casting Equipment There is a number vacuum casting equipment designs available today, with varying degrees of com- plexity. Below are some common features of vacuum casting equipment. FOUNDRY A Low-Cost Vacuum Casting Equipment for Aluminium Alloys 1 B. Aremo a, * and M. O. Adeoye b, ** a M.Sc, Centre for Energy Research and Development, Obafemi Awolowo University, Ile-Ife, Osun State, Nigeria b Ph.D., Department of Materials Science and Engineering, Obafemi Awolowo University, Ile-Ife, Osun State, Nigeria *e-mail: bolaji_aremo@yahoo.com **e-mail: madeoye@yahoo.com Abstract—Some of the advantages inherent in the vacuum casting technique such as improved mechanical properties and elimination of shrinkage have been replicated in a low-cost design. Melting and vacuum requirements of the equipment were determined based on a furnace capacity of 15 kg of aluminium. Clay- based refractory and insulating bricks were used for furnace construction. The vacuum system was made from locally available materials and designed for efficiency required for vacuum casting. The equipment was used to melt and cast small-sized specimens using the lost-wax technique and compared with green sand and ceramic mould cast specimens. Tensile and shrinkage tests were carried out on all specimens. The results of the tensile tests were 123, 98 and 113 MPa for the vacuum cast, green sand cast and ceramic mould cast spec- imens, respectively. Furthermore, shrinkage defect which is common to both green sand and ceramic mould casting was eliminated in vacuum casting. The vacuum casting equipment cost an equivalent of about U.S $1000.00 (One thousand dollars) to construct and can be easily scaled-up for large-sized castings by increasing furnace capacity and the size of the moulding flask. Key words: Vacuum casting, aluminium, countergravity casting, foundry. DOI: 10.3103/S1067821210020094