Introduction
Castings, the process of forming a desired shape by pouring molten metal into a prepared mould, are used throughout a wide range of industries, most notably manufacturing. The two primary methods of casting, either gravity die or lost foam (LFM) and full mould vacuum (FV) casting, offer distinct advantages that make them ideal for particular applications. This article will compare and contrast the two, in order to offer a comprehensive comparison of the two processes.
Gravity die or lost foam casting
Gravity die or lost foam casting (LFM) is a casting process first developed in the late 1950s. It involves patterns made of foam, which are then placed into a prepared mould. Molten metal is poured into the mould and the foam is vaporised, creating cavities into which the metal is allowed to flow. The distinct advantage of this technique is that the resulting metal casting does not require machining, as the foam pattern produces very tight tolerances.
The greatest benefit of LFM is in its cost-effectiveness. Lost foam molds are relatively easy to construct out of lightweight materials and can handle a wide range of alloys. Furthermore, the process requires little in the way of post-casting machining, greatly reducing labour costs. This makes LFM an attractive option for those looking to save money on their metal casting projects.
One major downside of LFM is that it tends to be more time-consuming than other casting methods. As it requires a foam pattern, this pattern must be carefully crafted and removed from the mould prior to pouring. Furthermore, the process must be carried out under a controlled atmosphere in order to ensure that the foam does not overheat and cause damage.
Full mould vacuum casting
Full mould vacuum casting (FV) is a process designed to increase the quality and tolerances achievable with casting. Unlike LFM, which relies on foam patterns to create the desired shape, FV uses a closed mould which is then evacuated of air. This dramatically reduces the contact between the liquid metal and the atmosphere, creating a much tougher, higher integrity cast.
The greatest benefit of FV is its accuracy and consistency. The process eliminates the need for intricate foam patterns and can produce castings with very tight tolerances. Furthermore, the higher degree of structural integrity provided by the vacuum atmosphere also make it an ideal technique for creating high strength, long-lasting castings.
The downside of FV is its cost. Due to the complexity of the process, it tends to be much more expensive than other casting methods. Furthermore, the moulds required are generally costly to construct, making them a significant investment for many manufacturers.
Conclusion
Gravity die or lost foam casting and full mould vacuum casting offer distinct advantages and disadvantages that must be taken into consideration when choosing the best process for a particular application. LFM is more cost-effective but time-intensive, while FV offers greater accuracy and quality for a greater investment. By understanding the comparison between the two, manufacturers can make the best choice for their casting projects.
