What is Coining in Sheet Metal? (And how it is done?)

sheet metal coining press

What is Metal Coining?
Metal coining is an operation in which the sheet metal or forged metal is compressed or squeezed into a desired shape or profile by using a punch and die.

The coins which you use to buy something from a shop are manufactured by metal coining operation.

Metal coining is a type of precision stamping operation in which the sheet metal is subjected to high stress which results in plastic deformation of the material.

Metal coining is generally a cold working operation and a sheet metal blank is kept between the die and a punch.

The high pressure applied to the blank causes the material to deform and it takes the shape of the die.

The presses used for coining operation are generally;

  1. Hydraulic presses
  2. Mechanical presses
  3. Gear driven presses

Out of these presses, a hydraulic press is widely used for coining operation.

In coining operation, the material undergoes plastic deformation. Hence the amount of force required in coining operation is more than that in the stamping operation.

There are few benefits in cold coining operation like;

  • It gives good surface finish.
  • The plastic deformation reduced the surface grain size.
  • The material gets work-hardened by cold coining operation.

The name “coining” came from the manufacturing process of coins.

In coining operation, the design is made on both the sides of the sheet metal blank because of the dies having impressions.

sheet metal coining

The coins which you use for purchasing is the best example of product manufacturing by coining operation.

Coining operation is used in industries to manufacture coins, badges, medals, buttons, energy springs, etc where high precision is required.

For manufacturing of metal coins, the minting presses are used which applies a high amount of force in the small area where the coining takes place.

Coining operation is best suited for metals like copper, brass, gold, silver and other soft metals. Apart from this, the hard metals are also used in coining operation.

Advantages of coining

  • Coining operation can produce sharp, precise corners, and good surface finish.
  • The failure due to tension does not take place, as there is involvement of compressive forces during the coining operation.
  • The material gets work-hardened by cold coining operation.
  • The repeatability of the process is very simple and easy.

Disadvantages of coining

  • The main disadvantage of coining operation requires a very high amount of force to compress and plastically deform the material.

External links:
Coining press: Image by Luis García, CC BY-SA 3.0, via Wikimedia Commons
Two coins: Image by Anonimski, CC0, via Wikimedia Commons

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