A dedicated management team and workers control the production process of circulation coins within a computer integrated manufacturing system at the South African Mint.
1. Casting, new materials and slitting
Production starts at the highly modern continuous casting furnace at the Casting Section. All the raw materials are melted in the furnace and then cast through carbon dies into two strips which are then drawn through a milling machine where the hardened crust of the alloy is scalped and rolled up into 1, 5 ton coils ready for the rolling process.
Traditional copper based coinage metals such as Cupro Nickel; brass and bronze have long been used in the production of coins and still represent an important selection of materials for this application.
Along with the range of plated coinage materials, the South African Mint offers a range of traditional coinage alloys. These include materials from the Cupro nickel; aluminum bronze; aluminum nickel bronze and brass range of alloys, as well as more exotic alloys aimed at achieving very specific criteria of color, electromagnetic properties and wear characteristics. These alloys are produced either in-house by the South African Mint in its modern computerized continuous casting furnace, or in conjunction with its local or international supplier network.
The South African Mint recognizes the importance of these alloys as a component in the design of coinage systems, and is constantly involved in research work aimed at finding innovative ways of expanding their field of application.
2. Rolling Mills
Coils are rolled on modern computer controlled breakdown and fine rolling mills to produce strip of the correct thickness. Electronic measuring equipment controls the thickness and produces a product that is within microns of the required thickness. These tolerances are essential in determining the final mass of the product. Automated delivery and removal of materials by means of automated guided vehicles allow for an uncluttered and safe working environment
3. Blanking
Blank circular discs are punched out of metal strip by means of precision die-sets mounted in high-speed blanking presses. Each coin blank is rimmed on the circumference of the blank before it moves on to the Deburring, Electroplating and Coining process.
4. Electroplating
Electroplating is the process of electro deposition of a specific thickness of coating either copper, nickel or bronze onto sub strait (core) material of either steel or an alloy.
The process of electro plating coin blanks is an alternative method of producing less expensive blanks while maintaining the visual and technical characteristics of a solid alloy based coin. Circulation coins in traditional alloys do not undergo the electroplating process and move past the plating plant on conveyor belts to the next process.
5. Annealing and Polishing
During the annealing process the coin blanks pass through a flat belt furnace which has a protective atmosphere of Nitrogen to prevent oxidization. All coin blanks then go through a process of polishing after heat treatment to remove any minor scratches or imperfections to give them a high quality surface finish in preparation for the minting process.
6. Coining
The prepared coin blanks are coined on high-speed presses at speeds ranging from 750-850 strokes per minute where the obverse and reverse of the coin are imprinted with the specific insignia of a particular country, both for South Africa and internationally.
Finished coins are continuously subjected to rigorous quality control inspections. Coins in traditional alloys and electroplated coins are minted in this department.
7. Packing
A variety of packaging options are offered by the South African Mint according to the client requirements. Once packed the product is thereafter stored in a computer controlled high-bay store, accessed by automated guided vehicles only. Alternatively, the product is transported to the Dispatch Department where they are shipped off the client.
MATERIAL HANDLING
What is Material Handling?
Material handling can be defined as the cost effective conveying and transporting of materials between different work centres’s and stores, using pre-defined and tested methods and equipment, to achieve the utmost efficiency and effectiveness. As a result of the Mint’s sophisticated Material Handling System (MHS), the shifting and lifting of materials between work centre’s and stores, and storage itself, are undertaken in the most time-, cost- and space efficient way possible.
Material Handling Devices
Material Handling Devices include stores, cranes, Automated Guided Vehicles, conveyors, drop-sections and auto motors.
STORES
Stores at the Mint where Material Handling Devices are used include:
Raw Material Store
- The Raw Material houses raw steel coils.
Coil Store
- The Coil store is where steel and copper coils are kept for the rolling and blanking processes.
Unplated Blanks Store
- The Unplated Blanks Store is used to store blanks for the plating process.
Final Product Store
- In the Final Product store, products are kept for the counting, coining, bagging and dispatching processes.
CRANES
Cranes, include a Coil crane that is located in the Coil store and two cranes that are located in the Final Product store (one per aisle).
Coil Crane
- The Coils store crane, located in the coil store, moves coils from the in-feed station to allocated locations in the store and issues coils from the coil store to the out-feed station of the coil store.
Final Product Cranes
- The two cranes located in the Final Product store serve to issue and remove product on both the northern and southern sides of the store.
AUTOMATED GUIDED VEHICLES (AGVS)
These are located as follows:
Coil Store
- AGVs are used in the Coil Store to issue Coils to the Rolling Mills, and deliver Blanking from the Coil store out-feed station. These AGVs also remove coils from Casting, Slitting, the Rolling Mills and Blanking, and convey them to the Coil store in-feed station. The removal of coils from Blanking to the Coil store in-feed station only occurs in the rare event that an incorrect coil is delivered at the Blanking machine.
Unplated Blanks
- AGVs remove blanks from Blanking to the Unplated Blanks store and issue blanks from the Unplated Blanks store to Plating. Issues and removals are affected by the AGVs, which collect and deposit blanks directly in the Unplated Blank store.
Plated Blanks
- •AGVs remove blanks from the Plating out-feed or Counting, and deposit them at the in-feed station of the Final Product Store.
FINAL PRODUCT STORE
- AGVs dispatch products from the out-feed stations depositing them at Coining, Counting and Packing and at Dispatch. The AGVs also remove products from Coining, Counting and Packing and Dispatch and deposit them at the in-feed stations of the Final Product Store.
Conveyors
In-feed and out-feed conveyors are located in the Final Product store. These devices are used to move material horizontally between two fixed points.
DROP SECTIONS & AUTO MOTORS
Counting In Drop section
- The Counting In drop section deposits the requested blanks into the in-feed hopper, to be counted on the Counting In machines.
Counting and Bagging & Coining Drop sections
- The Counting and Bagging drop section and the Coining drop section work the same way.
In-feed and out-feed conveyors are located in the Final Product store. These devices are used to move material horizontally between two fixed points.
TOOLROOM
The South African Mint is fortunate in having a state of the art toolroom which is fully equipped with the latest sophisticate CNC machinery; where all tooling associated in the manufacturing of coins and coin blanks is produced. By having this in house facility we are able to reduce the need to subcontract and thus minimise costs.
