Casting is a manufacturing process which is done by pouring molten metal (or other liquid material) into a mould cavity in the desired shape. The liquid is then left to cool and solidify, the solidified part is called a casting. To finish the process, the casting will be removed from the mould. Some examples of casting materials include, epoxy, concrete, plaster and clay. Often, it is easier to make a shape by casting, rather than joining several smaller pieces together, even large equipment such as a ship’s propeller can be cast in the necessary size.
Casting is an ancient process that has been around for 7000 years. There has even been a record of a casted copper frog dating back to 3200 BC.
Types of Casting
Casting with metal is similar to casting with any other material. The metal is heated until it becomes liquid and can be easily poured into a shallow mould. The mould includes the desired shape as well as runners and risers that control shrinkage. After the metal is sufficiently cooled, the casting can be removed from the mould. Any excess pieces of metal are then removed.
There are a few different ways in which concrete and plastic resin can be cast depending on the size and complexity of the desired outcome. These materials may be cast using a single-use waste mould, multiple-use piece moulds, or moulds made of small rigid or flexible pieces. Usually, there are several more steps to take when casting concrete or plastic resin before getting to a beautifully finished product. The cast often must be painted or etched to add aesthetic appeal. Often, a plastic resin cast will be made to look like metal or stone. Another option, to add beauty to this type of a cast is to alter the material when it is still in the liquid state. Sometimes, coloured sand will be added to give the look of stone. Plastic resins such as epoxy or polyester can be made to look like natural marble or travertine. This technique is often seen in washstands, countertops and shower stalls. Concrete is generally used for casting large products such as sculptures or outdoor seating.
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Imperfections in the moulds can cause imperfections in the casting as well. Fettling is the process of fixing these imperfections, whether it be by cutting, grinding, shaving or sanding. As you can imagine, fettling can be long and tedious work. Historically, fettling was all done by hand, but now there are robotic processes to help perform fettling. If there is quite a bit of fettling to be done, the resulting product will be significantly more expensive. Mould designers may add decorative items, use a different material or a different shape to reduce the amount of fettling needed.
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Casting Process Simulation
Casting process simulation is a new technology that allows a simulation of the entire casting process on the computer. This method has become an industry standard and utilizes numerical methods to calculate cast component quality, heat treatment, solidification and cooling time. It also provides a quantitative prediction of casting mechanical properties, thermal stresses and distortion. Using a simulation will allow one to visualize the final cast quality before production even starts. This has many obvious advantages including saving on energy and materials.
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