0 0 admin admin2018-05-08 23:49:252019-03-20 15:22:29Aluminum casting
Aluminum casting machining is a specialized process, requiring careful attention to detail. Due to the ways in which castings are produced, machining them can be difficult. Although there are still some machine shops that specialize in manually machining castings, CNC machining has become the option of choice for today’s manufacturers.
Aluminum die casting is the process whereby raw aluminum is melted in a foundry furnace to1360F, then poured into a mold with a cavity in the shape of the desired part. When the metal cools, it will have taken on the shape of the cavity.
There are four common methods of casting. Each method utilizes a different way of creating the mold cavity and of introducing the molten metal into the mold.
The fastest casting process is die casting. This method is best for large quantities, and uses a reusable steel mold called a die. High pressure is employed to force the molten metal into the die. Once the die is cooled (by air or by water,) the part can be removed. All this can be done in approximately a minute.
Sand casting uses a special type of fine sand, which is packed around a pattern. The pattern is then removed and the sand forms the cavity. The mold is made in halves; the bottom half is called the drag and the top half is the cope. On sand-cast parts, one can often see a line where these two halves of the mold meet. If the part requires holes, sand “cores” are fitted into the drag. After the part cools, the sand is broken up and removed. The main advantage of this method is that it’s relatively low-cost, and may be used for small quantities. Go to https://www.aludiecasting.com/bronze-sand-casting/ to know more information about sand casting
Investment casting uses a pattern coated with wax and ceramic slurry. When the metal is poured in, the wax melts. This can create a net-like surface for specialty parts. Finally, permanent and semi-permanent mold castings use a steel mold like die casting, but use low pressure or gravity to introduce the metal, which increases the time required.
Castings present more challenges for machinists than other types of parts. A casting will probably be difficult to place on a machining centre table, and may require some thought as to how it can be held. On a sand casting, the parting line may need to be sanded off. Metal can sometimes leak through the halves of a die cast mold, producing flash. Dealing with castings, even for a skilled machinist, is time-consuming.
This is why computer numerical control (CNC) machining has revolutionized the industry. Using computer software, a series of machines are programmed to produce any part required. The process is highly automated, cutting down on labour costs. Design engineers choose the machines required for any given part, and create a specific program. From there, the castings may be sent to a rotary indexer, which rotates automatically, allowing them to be machined on all sides. Often this is fully enclosed, and completely automated. With CNC, precision is possible, and this produces parts of superior quality.
Due to the many advantages of CNC machining, quality castings are easier than ever before to produce.