Today I will be discussing on evaporative pattern casting process. previously, some articles were published on investment casting process.
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What is evaporative pattern casting?
Evaporative pattern casting is a sand casting process that uses foam to form a replica of an item in order to evaporates in a sand mold in replacement of a molten metal. This casting process is also known as consumable or eva-foam casting. it is similar to investment casting.
Evaporative pattern casting is of two forms; lost-foam and full mold casting. They are widely applicable due to complex design that can be produce with relative ease. Their difference is that, in lost-foam casting sand is bounded. whilst, in full mold casting the sand is bonded (green sand). As of 2010, evaporative casting process is predicted to be used for 29% of aluminum and 14% of ferrous casting.
Evaporative pattern casting is widely used for aluminum casting. It is also used for steel casting, and for iron parts like water pipe and pump parts.
- Ability to cast light weight parts
- It is easy to performed when compared with other casting process
- It offers high dimensional accuracy
- Intricate and complicated shape can cast without using cores or drafts
- It offers high surface finish (smoothness) to the casting
The working principle of evaporative pattern casting is achieved by producing a foam patter, which is the replica of item to be cast. This pattern is brushed with refractory substances in order to add extra life to the pattern when molten metal is poured or to make it resistant to high temperature. The pattern is then attached with sprues and gates using adhesives. It is placed into a mold surrounded and packed by sand. Another way of doing this is by dipping the pattern into a ceramic slurry, just as investment casting. it forms a shell around it when it dries
The mold is kept at a specific temperature in order to allow the liquid metal to easily flow and reach all parts and cuts of the pattern. After this, molten metal is poured into the mold and the pattern-foaming material vanish out of the mold as molten metal reaches it. As the pattern vanishes, the molten metal takes its shape and solidifies. After it solidified, the casting is removed from the mold.
The difference between evaporative casting process and sand casting method is that, in evaporative casting the pattern is not remove from the mold. This help to reduce the need for draft provision. Evaporative casting method is determined by the grain fineness number, time of vibration, degree of vacuum, and pouring temperature on surface roughness etc.
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And that is it for this articles, what is Evaporative pattern casting, its applications and advantages. I also enlighten on its working principle. I hope you enjoyed reading this articles. Freely ask questions and please share with other. Thanks for reading!