Metal casting, basically, is a process of producing objects by pouring molten metal into an empty frame. The metal cools and then hardens, thereby producing a product that takes the shape of the frame (often called a mold); the product is then removed from the frame. After that it may need to be finished off, depending on the product, if there is any surplus material obtruding from that product.
Advantages of Metal Casting
The main reason that manufacturers opt for metal casting to produce goods is that it is less expensive and sometimes quicker than producing them using other methods such as machine tooling the item from a block of metal.
Frames can, in certain circumstances, be reused and that will ensure further savings in the manufacturing process, after initial set up costs.
Materials Used in Production
Commonly, the metals used for casting are: magnesium, copper or aluminium alloys. Tin, Zinc and lead alloys are also used.
The Process
The starting point is to draw up a template, essentially a pattern which is a replica of the outline of the item being produced. Depending on the item, the pattern developers would, typically, use wood, plastic, or plaster. It has to be a careful and exact process; the design involves precise calculations so that the parts produced fit and operate correctly.
If the metal casting is hollow, an extra piece of sand or metal (known as a core) is needed to shape the internal form and make it hollow; these are usually strong and collapsible so that they can be easily removed from the finished product.
The next step is called molding. This is a multi-step operation which will establish a cast around the pattern using molding sand.
Pouring in the molten metal is the next part of the process. Once the metal is melted, it is poured into the cavity of the frame (mold) and left to solidify. When solidification has taken place, what is known as the shakeout process begins, and the frames undergo vibration to shake out the sand from the casting. Sand removed is often saved for future operations.
The final step in the process is cleaning. The product is removed from the frame, rough edges knocked off and cleaned of any molding material. This is known as fettling. The frame itself, if it is intended for re-use, is also cleaned and prepared for the next job.
Uses for Metal Castings
These days, almost every mechanical device that people use has been made by metal casting, for example – automobile parts, washing machines, tumble dryers, tools, all types of machinery; the list is endless.
Metal casting has, of course been around for many years, but what has increased usage is, of course, the advancement of computer technology; precision design processes and more precise tolerances. New and innovated methods of production are constantly evolving; reverse engineering and 3D modelling are examples of innovative techniques. As the industry develops, with the main focus on digital technology, costs will come down which will benefit manufacturers and assist them in maintaining their profit margins.
