Coining Process is described as the squeezing of metal as it is held in closed dies. The work piece is placed in the die. A movable punch within the die cold works the material and forms intricate features. The coining process is typically used to produce coins, medallions and similar products.Historical Background
Though it would be very difficult to ascertain since when exactly man is using coin but evidences found by excavations suggest that it was conceived by three different Civilizations.
In 6th century BC coins were used for trading in India, Asia Minor and China. But the first coins may have been struck by the Greeks living on the west coast of modern Turkey. These were made of Electrum a naturally occurring alloy of silver.
The Ancient Indian coins are commonly known as punch-marked coins because, these coins bear the symbols that were punched on pieces of silver of specific weight. Interestingly earliest Indian coins have no defined shapes and they were mostly uniface.
The Greek emperor, Alexander the Great(336-323 B.C.) can be credited for spreading the concept of coinage over the vast territories that he conquered.
Perhaps it took long hours to produce a single coin in the mint of those days, compare that to today when mechanized machine makes it possible to make more than 75 million coins in just 24 hours.The following operations can be categorized under Coining Process: Creation of Master Die
The coining process begins with the time tested skill of the craftsmen designing and modelling the new coins . This can seem quite contrary to the rest of the production processes which makes use of the most sophisticated techniques. A 3D model of the design in plasticine is first made which is then refined by casting it in a very fine plaster. An Acrylic model is then made, reduced and cut in steel by precision 3D reducing machines. The production dies are then reproduced from the cut steel dies.Casting, new materials and slitting:
Actual production starts at the furnace in the casting section where raw materials are melted and then cast into strips that finally takes the form of coils.Rolling Mill:
Coils are rolled on modern computer-controlled rolling mills to produce strip of the correct thickness. Electronic measuring equipment controls the rolling gap and produces a product that is within eleven microns of the required thickness.
Such fine tolerances are essential in determining the final weight of the product. The delivery and removal of materials is done by means of automated guided vehicles, which makes it safer to work and an uncluttered workspace.Blanking
Blank discs, circular in shape are punched out of the coiled metal strips by high-speed blanking presses. This has the capacity to produce 4000 coin blanks per minute. According to requirements, unique edge marking on the coins, can be done at this stage. All the coin blank is rimmed before they are sent to the next stage i.e, blank store where it will be kept, ready for the next process.Electroplating
Coins made from the traditional alloys are not subjected to the electroplating process and therefore go past the plating plant to the next process. The production of bi-coloured coins by the electroplating process is a recent development.Annealing
Heat is applied to make the coin blanks malleable in preparation for the minting process. Then they are polished to make them resistant to tarnish.Coining and Packing
The coin blanks prepared as above are coined on high-speed presses, producing around 750 coins per minute. The finished coins are subjected to stringent quality control inspections. The end products are packed and stored in a computer controlled store that can be accessed by automated guided vehicles only.