The power of metal
How raw metal is transformed into a finished product
Metal is one of the most common materials used in the industrial world – but very few people know the process of how raw metal is transformed into a finished product. Like other manufacturing processes, metal manufacturing requires the use of both humans and automated robots.
Typically, there are two types of raw metal manufacturing that is performed. These are: metal mould casting, and sheet metal formation. Both these processes yield different results, and are suitable for different metal products. Metal mould casting, for example, is more effective for thick and complex metal products, whereas sheet metal transformation is more appropriate for metal products that are relatively thin and one-dimensional.
Metal Mould Casting
The metal casting process involves pouring molten metal into a mould cavity where, once solid, the metal takes the shape of the cavity. There are two main types of moulds that are used. These are:
- Expendable Mould: whereby the mould is rigid and is subsequently destroyed after the metal has solidified.
- Permanent Mould: the mould is kept intact after the metal has solidified, due to the ductile material. It can be reused multiple times.
Sheet Metal Transformation
There are various sheet metal working processes that are used in order to transform a sheet of metal into a given shape. These processes include: bending, drawing and stretching.
All of these forces work by applying pressure to the metal beyond its yield strength, causing the material to plastically deform, but just enough, otherwise the sheet may break. In doing this, the sheet metal can be bent or stretched into numerous complex shapes. The possibilities are infinite. Sheet metal forming processes include the following:
- Bending: The process involves applying a huge amount of force along one axis of a metal sheet, in order to cause it to bend at an angle. A machine called a press brake, which can be manually or automatically operated, initiates the bending action. It is important to note that when a piece of metal is bent, the residual tension causes the sheet to spring-back slightly. In order to overcome this retreat, it is necessary to over-bend the sheet a to precise amount. This will enable the sheet metal to achieve the desired bend radius and bend angle.
- Deep Drawing: Deep drawing requires sheet metal to be stretched into the desired part shape. A tool pushes the sheet metal into die cavity in the shape of the desired cup-shaped part. These parts come in variety of shapes such as with straight or curved walls. Deep drawing is most effective with malleable metals, such as aluminium, brass, copper, and mild steel.
- Stretch forming: Stretch forming involves bending and stretching sheet metal over a die in order to form large contoured parts. Gripping jaw holds the edge of the sheet, and force is applied are increased incrementally. The metal sheet is then stretched into a new shape.
The assembly of the metal products is usually done by welding and binding with adhesives, riveting, threaded fasteners, or even yet more bending in the form of a crimped seam.
After metal product has cooled, it is generally sand blasted, primed and painted. Additional manufacturing elements may be applied after this step. The finished product is then inspected and shipped off to the customer!