Investment casting

Investment casting or lost wax casting has been used by many different cultures for thousands of years.The Egyptians used investment casting to make bronze statues and the Chinese made vessels and a variety of other items by using investment casting.Therefore, it is by no means a new process.The most modern approach, which has been used since the middle of the twentieth century is called ceramic shell casting.Because this is the most modern form of investment casting, I will bee focusing on this particular process for the entirety of the paper.
The two different types of patterns used in investment casting are called expendable and permanent.Expendable patters are made of wax, are joint less, and yield a casting with a higher degree of accuracy than the permanent pattern method.The permanent pattern method uses a pattern that is made of wood, steel, or some other type of solid material.Using the permanent pattern method is usually cheaper than the expendable pattern method.One disadvantage of the permanent pattern method is that the molds must be assembled in separate parts, which makes it less accurate than the expendable pattern method.
Thefirst step in investment casting when using the expendable pattern method is to manufacture a die.The die is made from strong alloys such as steel and Duralumin or softer fusible alloys where accuracy is less important.Steel dies are the best for long production runs and are machined from a solid piece of steel.Many dies are produced in two or more sections enabling the pattern to be removed once it is cast.After the die is done being machined it is coated with a parting agent or lubricant which helps the pattern to be extracted.The die is used repeatedly to makewax patterns for the investment process.
Wax is the most common material used in investment casting.The wax has a low ash content, is compounded from natural and synthetic waxes and resins, and usua…


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