In 1964, lost form process was invented by M.C Lemmings. This process was made known in public in 1980s by General motors with the introduction of its new car the Saturn. This new car line utilized LFC in the production of its cylinder heads, engine blocks, crankshafts, transmission cases and differential carriers. Lost foam casting is a casting process that involves evaporative –pattern that is like investment casting but instead of wax, form is used for its patterning. Low boiling points is used in the casting process to simplify the casting process with only the need to melt the wax from the mold.
Currently, the iron blocks are cast by GM’S Saginaw Metal Casting Operations for the Gen, 3 V and 38000 V6. Aluminum heads for the companies Gen 3 V8 and Vortex inline six blocks are also cast. Vortex inline six used the lost foam process that was introduced by GM Saturn. Casting Development Validation center (CDVC) and SMCO have worked hard to refine modern castings which is a process full of subtle tweaks but a simple process.
The process of lost foam method starts with the use of Styrochem- supplied polystyrene beads. This substance looks like granules of sand which are then given a day to wet and expand. This is by placing on Styrologic pre-expanders. The granules are then placed in seven more cylinders which take a total pattern process of seven stages. Excessive water is removed through pre-heating then placed into the cavity of the tools. On the tool chest, steam is repeatedly passed which triggers the fusion process after heating. This links together the beads.
High pressure is created by the use of an autoclave in the steam chest to bind together the beads. Then the steam chest is de-pressured. This is the cooling process by piping cold waters on the chest cavity. Chilled water is used in the de pressure process by spraying it on the mold plate. Both the pattern and the tool are able to cool down. The pattern is finally exposed to room temperature. The patterns of lost foam process are sliced to pieces which are glued together to develop the final desirable component.
High performance and strong components of the lost foam casting by the company produces approximately 450 hp with V8S of 1, 5000 to 2,000 each day. These Romulus engines are used by light trucks. Expenditure reduction at the plants has cost the company $75- million since 1999. Quality and uptime improvements has been witnessed by GM’s Saginaw Metal Casting operation to match the way of V8 and to market at a more competitive advantage compared to its Mexico competitors.
Casting process is advantageous which requires cores and extremely complex castings. The work after this process shows excellently finished surface, and accurate with no drafts, no flash is formed since there are no parting lines. Lost foam casting is much cheaper compared to investment casting. This foam is cheaper than wax and the process is much simple. There is natural directional solidification which can be manipulated and caste into desirable shapes. LFC allows parts to consolidate into whole internal components. (Degarmo, Black, Kohser, 2003).
While other formational process require the assembling of various parts. The main disadvantages for this process are two. First, the pattern costs high if there is low volume production. Patterns can be distorted and easily damaged since they are weak. A large initial cost is incurred is a die is used. Austin Design Group Inc. is also another company which is lost foam casting industry. It produces high quality material with high accuracy tolling. Machined tooling has been supplied into the market by this lost foam castings Industry.
Degarmo, E. Paul; Black, J T.; Kohser, Ronald A. (2003), Materials and Processes in Manufacturing (9th ed.), Wiley, ISBN 0-471-65653-4.