While the process of metal casting is fairly simple, there are many factors that need to be considered to ensure a quality product. The most important factor is the quality of the mold. Overly strong molds can result in hot cracks or tears. Excessive reinforcement can prevent the sand from collapsing and obstructs the free contraction of the casting. Metals contract when solidified, and a mold must be weak enough to allow the casting to contract.
In addition to the proper mold design, proper sand control and an excellent molding procedure can help to minimize the number of casting defects. Here are some common casting defects and their cures:
The molds are usually made of the same metal as the final casting. They sit inside a chamber that will be filled with material. Once the casting hardens, the molds will be separated and the finished product will come out of the mold. Depending on the size and weight of the part, a mold may contain multiple castings. When the casting is ready, the dies are separated and ejector pins are used to push the product out of the mold. The parts that will become scrap are cut off and cleaned, and the finished shape may need to be sanded or polished.
During the casting process, metal cores and loose mold members are withdrawn from the mold. The casting machine then returns to the “up” position. Once the full casting has cooled, it is post-processed. The cast is then trimmed, the gates are removed, and the part is checked for defects. For the purpose of testing, mold design is a crucial consideration. Often, this will determine a quality-as-a-product.
Metal casting defects include cavities, inclusions, cuts, and washes. These can be attributed to a variety of factors, including the type of metal to be used. The type of metal to be cast must be specified in the ship’s blueprints. In addition to the mold, the ship’s blueprints will specify the metal and alloy, and the specific properties of each. For the best quality of the casting, it is important to understand how metals react with the mold.
The melting temperature of metal in the furnace should be as close to the analysis as possible. For example, a metal used for shipbuilding should be at approximately 700-800degF for an hour per inch. This should be sufficient to prevent cracks. It is important to compensate for losses in charge and during the melting process. Incorrect heat treatment can lead to cracked castings. Whether it’s a copper-base casting or another metal, it is important to follow the proper melting process.
Today, the casting process has made it possible for modern engineers to create parts easily. Automation and electronics have made it possible to use various metals and increase the quality of the products. There are various types of casting processes that are used to produce every day items. While the fundamental principles of these processes are the same, the technological advancements that make these processes more efficient are possible only through computerization and automation. So, the benefits of using the casting process can’t be underestimated.
There are many different types of casting defects that need to be avoided. Common defects include rat tails, buckles, and scabs. These defects occur when sand expands and contracts during the process. The defect is easy to recognize by its discoloration. It also causes the product to be uneven, which is known as “rat-tailed casting”.
Whether sand or die casting, the mold will be the first part of the process. Both types of casting will require a mold. A mold is a structure that the metal is poured into to form the object. Molds can be reusable or disposable. Molds can be mounted to a board or fixed to a match plate, which makes the process much easier. This method also allows the creation of groups of parts in one mold.
