Drop forging is a metalworking technique that is used to slowly and methodically shape a piece of metal that has been heated at extreme temperatures. This heated metal is called an ingot. A die or hammer is used during this process which is raised and dropped with force onto the ingot to shape it. As the hammer or die is dropped, the metal ingot is flattened or if a mould is being used, forced into the mould.
Many complex parts are used during the forging process. These parts often require a number of different dies and moulds. Drop forging can complete most of the component manufacture process but additional machines may be required to finish the piece. An industry where drop forging is used widely is the automotive industry. Engine parts, axles and gears for example are still made using this manufacturing process.
Drop forging dies are typically made out of high alloy steel. This is often referred to as tool steel and is designed to withstand high impact. Its dies undergo a lot of heating and cooling processes and need to be able to withstand thousands of cycles. It is common for drop forging dies to be made in two halves. The hammer forms the top half and this is attached to a block which is repeatedly raised and dropped onto the metal. The bottom half forms the anvil and this is the surface that will hold the metal whilst it is being forged.
There are two types of forging - open die and closed die. Open dies, as their name suggest, do not completely enclose around the ingot and they are usually flat in design. You can also have cutting dies or dies that are contoured. An open die means that the ingot has room to expand to the desired shape and thickness. Open die forging is traditionally used in a process called cogging. This process helps to ensure that a uniform thickness is created and is used with a concave die.
Closed die drop forging is often referred to as impression die forging. The hot metal is poured and forced into a mould and the molten metal fills up the mould creating the desired shape. Any excess material, referred to as flash, is then forced out of the mould and discarded.
You may have also have heard of flashless drop forging. As the name suggests, no flash is produced during this process as the metal is completely enclosed inside the mould. Many manufacturers prefer this drop forging technique because it is more cost effective and results in less waste ingot being created. http://www.geleval.com
These processes have years of history attached to them and have changed hardly at all over the years because it is one of the most efficient and effective means of creating different metal components.
