Coin life cycle
This page describes how New Zealand coins are designed, produced and minted.
The process of planning and producing New Zealand coins is complex, taking anywhere from 18 months to two years. The process generally incorporates six stages:
The coin minting process begins with us commissioning and approving the coin's design. Mint engravers have the challenging task of transforming this two-dimensional coin design into a three-dimensional sculpture. They can do this in two ways:
- Plaster model – the engravers create a large-scale plaster model of the chosen design, cutting the details into the plaster by hand. They place the plaster on a scanning machine where a digital camera captures the details from all angles. Now that the design is digital, the engravers can make any more changes to the design on screen. The electronic design file is then turned into a cutting programme for a computer-controlled engraving machine, which cuts the design into a master punch.
- Direct engraving model – the engravers digitally sculpt the coin's design on a computer tablet then transfer this to an automated milling machine, which engraves it to a master punch.
- Once the master punch is created, it is pressed or ‘hobbed’ against another blank die to produce working dies. These dies are used to make the coins, with each one able to make about 500,000 coins.
- The master punch always has a positive image so a negative of the design can be transferred to the working die. This allows the coin to be struck with a positive, recognisable image.
- The different metals for each coin—for example, copper, nickel and zinc—are melted together in the furnace, where temperatures can reach up to 1,450 degrees Celsius.
- A sample of this molten metal is then analysed to confirm it has the right composition.
- The molten metal is poured into a holding furnace and cooled.
- The metal is cast into a continuous strip, which is wound into coils that weigh up to three tonnes.
- Blank discs of metal of the correct size are punched from the coiled strip in a blanking press, much like a biscuit or cookie cutter.
- Next, the blanks are placed in a rimming machine to give each a slightly raised rim around the edge. This stops the coins from sticking together, makes them easier to stack and protects their surface.
The current $1 and $2 coins produced by The Royal Mint are solid alloy and plated steel. They have a steel centre encased in a layer of different metal such as nickel, brass or copper. After rimming, the blanks are electroplated where a layer of copper, nickel or brass is electroplated directly onto the surface of the blanks.
New Zealand's 10 cent, 20 cent and 50 cent coins are made by the Royal Canadian Mint, using its own innovative, multi-ply-plated steel (MPPS) technology. A special process is used to harden and dry them, so they are ready for striking.
Striking is when the coin's design is added to both sides of the blank using tools known as dies.
- Stillage or crates, which hold around 850 kilograms of clean and shining blanks, are tipped into a container (known as a hopper) above a coin press.
- Each blank is fed into perfectly sized recesses in a circular plate.
- As the plate rotates, the blank is held by a collar as it sits between a pair of dies.
- With one strike of up to 150 tonnes of pressure from above and below, the obverse and reverse (or heads and tails) are added, often together with the milled edge from the collar, and the blank disc becomes a coin.
Coining presses can strike up to 850 coins per minute. An operator regularly inspects coins for quality as they are ejected from the press. The operator regularly changes the dies to make sure the quality is uniform. Once they meet the operator’s approval, the finished coins are packaged, boxed and shipped to our vaults.
In 2015, we introduced a recycling system for old or damaged coins. We have these coins destroyed by smelting them and making them into metal ingots.