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Bending metal thanks to ductility and press brakes

September 14, 2010

As you take on your daily commute equipped with your faithful thermos full of coffee, it occurs to you that this metal thermos is perfectly round and sits flawlessly in the cup holder of your car. You begin to wonder how does a piece of metal go from just that, a piece, a sheet, or whatever initial form it was in, to be made into a perfectly cylindrical shaped product that will hold your morning coffee. Sure, we have all heard about machines and equipment that are able to bend, shape and cut metal…hydraulic presses, hydraulic machinery, press brakes, H-frame presses but still, ever wondered what makes metal bend and then assume the shape that it was given?

Ductility
Metals have a property which many other materials such as wood, glass or ceramic do not possess, this property is known as ductility. According to the Merriam Webster Online Dictionary, ductility is defined as “capable of being fashioned into a new form” [1]. Ductility is a mechanical property which illustrates the degree to which a solid material can be plastically deformed without cracking. Therefore, when a material has the characteristic of being ductile, it can be bent and formed into an unlimited number of shapes. The ductility of a metal is influenced by many factors such as the hardness and composition of the metal. For example, stainless steel is much harder to bend than copper, a soft metal which can be bent into never-ending shapes.

Bending

Bending is a flexible process by which many different shapes can be produced. Picture a sheet of metal on a table top. Imagine a few inches of overhang and the ability to apply enough force (using some type of hydraulic press) to hold the piece in place and to push on the overhang so as to cause it to bend. From a molecular point of view, it is the metal’s ductility characteristic which allows the bending to occur. At the bend line on the sheet metal, the outer side of the sheet is being stretched and the inner part is being compressed.

Resistance to bending
A metal that is harder and less ductile will display resistance to bending in three ways:
1. This metal will require more force to bend.
2. This type of metal will have a greater tendency to want to spring back to its original shape when the force being applied is stopped.
3. There is a greater chance of the metal cracking along the bend line.


In order to bend metals into the shapes that are required to manufacture our everyday products, hydraulic machines which are able to apply enough force are used. A brake, a metalworking machine, enables the bending of sheet metal. The press brake a more complex hydraulic machine “presses” or shapes the metal, by using force to compress certain sections of the metal and to bend it into pre-programmed shapes. A press brake, capable of making extremely complex shapes, enables sheets of metal to be bent into almost never ending shapes or sizes.

Established in 1980, RK Machinery is a hydraulic press manufacturer. Our products include H-frame presses, C-frame presses and press brakes. We pride ourselves on building quality, reliable and safe hydraulic machines. Visit RK Machinery.


1. http://www.merriam-webster.com/dictionary/ductility?show=0&t=1284060791
http://www.ehow.com/how-does_5030143_press-brakes-work.htmlhttp://www.efunda.com/processes/metal_processing/bending.cfm
http://www.helium.com/items/1941301-metal-bending
http://www.custompartnet.com/wu/sheet-metal-forming#bending
http://www.advantagefabricatedmetals.com/press-braking-process.html