Lost-Foam Casting Process
The lost-foam casting process (LFC), also known as Full Mould Casting, is a type of evaporative-pattern casting process that uses polystyrene foam for the pattern. It is a very cost effective process for casting metals, mainly aluminum and its alloys, but also bronze and copper alloys. Each polystyrene pattern corresponds to one casting and is made from either a foam block which is cut and formed with a hot wire and glue, or from a pre-made foam pattern. The foam pattern is coated or “invested” with a refractory material to form the mould, which is then heat cured and metal is poured in.
Advantages
The lost-foam casting process provides the ability to produce very complex components in superior surface finish and accuracy. By using the LFC process, both production costs and lead times can be significantly reduced. The process does not require the use of large, expensive machines and the number of operations required between the raw material and the final product is generally minimized. As the mold is made of low weight foam and the entire volume of the mould cavity is filled with liquid metal, the pressure created is less than conventional casting. As LFC allows the use of raw materials with high melting points, it gives the possibility to produce castings with very thin walls and also in all internal shapes and configurations.
Disadvantages
Although the lost-foam casting process is advantageous in many ways, it also has certain disadvantages. The process requires the use of specific materials and chemicals which can be costly and technically complex. Fluctuations in the temperature of the furnace or the mould can lead to problems such as cracking of the finished casting. Also, due to the relatively high degree of complexity, the process often requires high levels of operator skill and experience. As with all casting techniques, the mould can only accommodate parts with a single solidification path, so very complex parts must be made with special techniques.
Conclusion
The lost-foam casting process is a relatively new casting technique which has been gaining popularity in recent years. By relying on low-cost mold materials and a high degree of automation, the process can deliver high quality components at significantly reduced production costs. It is an extremely efficient way to produce complex parts with greater accuracy and improved surface finish. Moreover, the process can also accommodate raw materials with higher melting points, allowing for thinner walled castings. Despite the advantages, the process requires a high degree of technical expertise and is complex in nature. Therefore, understanding the process and its various aspects is vital in order to successfully implement this casting technique.
