Lost Foam Casting - Essay Example

Lost Foam Casting of the of the Introduction Lost Foam Casting (LFC) is a form of casting which follows the evaporative pattern of casting. This casting process is similar to the traditional investment casting process except for the fact that in the Lost Foam Casting (LFC) technique, foam is used in place of wax for making the patterns for casting and molding. The Lost Foam Casting (LFC) was invented by a Canadian sculptor named Arman Vaillancourt in the early 1950s. The general benefits of this casting technique were publicly recognized through the well-known automobile manufacturing company, General Motors in the year 1988 when the company announced the manufacture of its new car model, Saturn and also announced that the Lost Foam Casting (LFC) would be used as the primary casting technique for the production and manufacture of the different engineering parts of the automobile line including the cylinder heads, engine blocks, differential carriers, crankshafts and transmission cases etc. This report aims at studying the technique of Lost Foam Casting (LFC) in the field of engineering and construction. The process would be discussed by describing the various techniques and casting methods used in the Lost Foam Casting (LFC) technique, the application of this casting technique and the advantages and disadvantages of the same. Also, the economics related to this technique, the principle of application, the limitations, design considerations and the defects inherent to this casting technique would also be analyzed and explained. The report would be concluded by summarizing the findings from the discussion and evaluating the usefulness of the Lost Foam Casting (LFC) as a main form of casting technique used in the engineering and construction of different products. Discussion Principle of operation The first patent for this casting technique was filed by H. F. Shroyer in the year 1956 in which the patent for the evaporative pattern of casting using foam pattern embedded in the traditional green sand technique of metal casting. The Lost Foam Casting (LFC) is a type of casting process that makes use of the pattern materials made of foam. The pattern materials, thus evaporate during the phase of casting or pouring which means that the manufacturers in this casting technique do not have remove the used pattern materials from the formed mold before starting the solidification stage of the casting process (Figure 1). Figure 1: Schematic illustration of the lost foam or evaporative casting (Source: Kalpakjian and Schmid, 2006) The main principle of the application of the Lost Foam Casting (LFC) process employs the use of multiple steps of casting (Figure 2). The primary steps that are included in the Lost Foam Casting (LFC) are given as followed: 1. Making of the casting patterns through tool preheating, pattern ageing, pattern molding, bead pre conditioning and bead pre heating. 2. Assembling of the patterns or clusters used in the acting and molding process. 3. Coating and drying of the formed patterns. 4. Sand filling and compaction of the cast usually done with the vibration technique. 5. Metal casting followed by cooling of the same. 6. Shaking out the materials used for pattern forming, cleaning up and finishing the cast. Figure 2: Molding process in LFC (Source: Degarmo, Black and Kohser, 2003) The pattern is made through the use of polystyrene foam. If the cast is to be made on the basis of a simple geometrical form, then the use of a hot wire foam cutter can be done. In case the volume of casting is large, then a mass production usage pattern is sued which is similar to the injection molding technique. The foam cluster done for the casting is coated with ceramic material via the use of brushing, dipping, flow casting and spraying. This form of coating is known as the refractory coating technique. After this coating dries, then the cast is put into a container and baked up on a vibration table with unbounded sand. The system of automatic pouring is significant in the Lost Foam Casting (LFC) because the pouring process is most critical in this form of casting technique (Youtube.com, 2013). The common metals that are used for casting in the Lost Foam Casting (LFC) are cast irons, nickel alloys, aluminum alloys, copper alloys, stainless steels and steels. The size of the casting ranges from 0.5 kg to hundreds of tons. The minimum thickness of the walls of the casts is 2.5 mm. There is no upper limit for the thickness of these types of castings. The linear tolerance of these casting is 0.005 mm/mm and the general surface finish ranges from 25 to 23 mm in RMS. There are different types of LFC employed in the arena of engineering and construction (Figure 3). Figure 3: Different forms of Lost Foam Casting (LFC) technique (Source: Kalpakjian and Schmid, 2006) Applications There are many industrial applications of the Lost Foam Casting (LFC) technique. This casting process is commonly used in small scale and large scale engineering and manufacturing of products. Both small products and large products like automobiles and engineering products can be manufactured through the use of the Lost Foam Casting (LFC) technique. This casting technique is preferred by the large scale manufactures because it is the most effective casting technique of the large scale and complex casting that generally call for extensive cores on the part of the manufacturers (Degarmo, Black and Kohser, 2003). Limitations There are few limitations associated with the Lost Foam Casting (LFC) technique. The two main drawbacks of this casting technique are that the cost of the patterns used in this technique can be very high for the low volume casting applications which makes the process much non economical for the manufactures and secondly, the patterns made by this technique can get easily distorted or damaged because the tensile strength is much low (Foam cast Technology, 2014). Economics There are a number of environmental impacts associated with the Lost Foam Casting technique. The most significant ecological impact of the casting techniques are the large scale use of energy resources and the emission issues. However, if compared to the other casting techniques the Lost Foam Casting technique can be much advantageous, because the production of castings under this technique make use of a virtual production system of foam patterns due to which the machining applications are much reduced. This in turn, results in lesser environmental impacts of the whole casting process (Ruiou Company, 2014). The use of chemicals like lubricants and coolants cause the highest volume of environmental impacts in the manufacturing and metal construction industry. Since, the lost foam casting technique uses enhanced dimensional control means and lesser use of machining, therefore, the impacts of this technique are negligible. Design considerations and defects Many advanced design considerations are to be made in the Lost Foam Casting processes. The use of ceramic investment for the purpose of coating is a major design consideration made in this casting technique. The problem of carbon pick up is a main issue with this casting technique due to which a number of alternative casting technologies are being developed which allow lesser carbon pick up. The new casting technologies involve the processes in which the materials used for making the patterns are fully burnt out before the solidification of the casting is done. This process allows a wider variety of alloys and metals to be cast as the molds, which also enables the casting process to become more efficient in terms of ensuring that the carbon pick up from the system is eliminated while at the same time the advantages pertaining to the Lost Foam Casting technique are retained in the new casting processes. Conclusion There are high found benefits of the LFC form of casting technique. As such, many large scale manufactures prefer this casting technology to be used in their production and manufacturing systems. However, the retest disadvantage of the Lost Foam Casting (LFC) technique lies in the high costs of tooling which acts as a constraint for the manufactures with lower manufacturing volume to make the use of this innovative and advanced casting method in their manufacturing and construction systems. Thus, if high durability and economies of scale are to be considered then, the Lost Foam Casting (LFC) is found to have lower weightage as compared to the other available casting techniques in industrial construction and manufacturing processes. References Degarmo, E. P., Black, J. T. & Kohser, R. A. (2003). Materials and Processes in Manufacturing (9th Ed.). New Jersey: Wiley. Foam cast Technology. (2014). Traditional Lost Foam Casting - Foam is Burnt by Molten Metal. Retrieved from http://www.foamcast.in/lost-foam-casting-process-video.html. Kalpakjian, S. & Schmid, S. (2006). Manufacturing Engineering and Technology (5th Ed.). New Jersey: Pearson. Ruiou Company. (2014). The Lost Foam Casting Process Flow of Ruiou company. Retrieved from https://www.youtube.com/watch?v=6fEU3fuQd9s. Youtube.com. (2013). Lost Foam Casting. Retrieved from https://www.youtube.com/watch?v=HFITqk2KTjw. Read More