Production process in pictures

Production of coins and medals in the Mint is depicted in the following photographs with attached descriptions.

Preparation and processing of a plaster model

To create a plaster model, a nylon imitation of a curved coin surface is used to model the relief of a future medal (coin). Special software allows designers and programmers to adjust the scanned model through the reduction phase.
Plaster model – a common model showing the relief of the required product (magnified). Reduction, preparation of dies on the IMPALA 400 CNC equipment.
Modern CNC technology uses a laser scanner to generate an initial electronic version of a future product. To manufacture a new CNB commemorative coin, traditional technology is used, the so-called reduction on a mechanical reduction cutter. This procedure requires casting a silicone mould and, subsequently, a resin replica of the original plaster model.

Preparation of dies

Hand engraving is instrumental in cutting the relief parts and coin surface; this work is usually performed under the microscope. The final preparation of dies for minting proof products includes fitting the die with transparent foil that is then cut off, and the uncovered parts are sand-blasted for a matte finish.
When making multiple dies, reliefs are cold-pressed into soft steel, after which the tooling machine is centered and the dies are tempered and their surfaces finished. Samples of dies for proof coin production.
The coin surface needs to be polished to mirror lustre. To achieve that, polishing tools are employed, such as nylon and wood rollers, leather plates and diamond paste. Obverse and reverse dies and the press ring used for minting a 50-crown denominated coin. The coin is bi-colour, made of two different materials (the centre part is yellow and the outer circle is red).

Semi-finished coins and medals

Semi-finished products (blanks), from which circulation coins are struck, are fed into the counting machine through a vibration conveyer. Semi-finished products used for commemorative coins and medals are adjusted in special tumblers with beads.

Production process

The dies are fastened to the press by clamps, the obverse and reverse sides are centered with the help of a ruler. Circulation coins are struck in the press ring by the upper and bottom dies. The feed device of the press allows for transport of blanks into the workspace between the upper and bottom ends of the press tool.

Quality control and product samples

Commemorative silver coins (here with a 200-crown face value) are continuously inspected during mintage and prior to packaging into plexi-capsules. Samples of proof commemorative medal from the CM Issue Plan. Material: Au.
Detailed inspection of a minted coin. Samples of proof commemorative medal from the CM Issue Plan. Material: Ag.
The proof mintage technique results in a characteristic polished coin surface and a matte (sand-blasted) relief. Sample of bi-colour commemorative coin with a face value of CZK 2000.
The bottom die is centered in the press ring and it also serves as a “shaper” of the medal.
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