Products and solutions, 2002-04-15, 02:00 AM
ThyssenKrupp VDM: Major operation for the introduction of the euro
Modern coin blank production in German countryside
ThyssenKrupp VDM in Werdohl is one of the world`s five biggest producers of blanks for euro coins. A huge 50 billion coins were needed to replace the German Mark, French Franc, Italian Lira and other currencies. 285,000 metric tons of coins, some 7,100 truck loads, had to be produced over the past three years.
Ahead of this major event some changes were needed at the company`s production plants in the rural Sauerland region of Germany. Since the end of the 1980s output has increased from 9,000 to 12,000 metric tons of coin blanks per year. The current level is actually 20,000 tons taking into consideration the extra work involved in producing the bimetal blanks used for the two highest denominations, the 1 and 2 euro pieces, which each comprise an inner core and outer ring of different materials. The center of the 1 euro piece is made of the three-layer material Magnimat and the outer ring of a nickel-brass alloy, while the color scheme is reversed for the 2 euro piece. Magnimat is a copper-nickel alloy developed and patented by ThyssenKrupp VDM.
The alloys needed - as well as Magnimat, copper-plated steel is used for the 1, 2 and 5 cent coins and Nordic Gold for the 10, 20 and 50 cent coins - are produced at the company`s Unna plant. After the slabs have been hot-rolled in Bochum, the strip is finally sent to Werdohl where it is cold-reduced to the requisite thickness.
To protect against counterfeiting, the chemical composition of the material has to comply with strict specifications and final rolling has to be carried out with the highest precision, because the prescribed coin weight depends on the thickness and density of the material used. For example, for coins with an overall thickness of two millimeters, the permissible tolerance is plus/minus two hundredths, i.e. 0.02 millimeters. The permitted weight variance is three percent per coin, and just one percent for 100 coins.
To handle the enormous production flow, the workforce of this ThyssenKrupp VDM unit was increased from 100 to 150 employees and a large number of production facilities replaced. This was necessary because sophisticated process technology and extensive quality controls were needed to guarantee the quality of the coveted blanks.
In the first step the strip is tensioned on coilers and fed to the punching unit via a leveller. The main punching unit turns out blanks - also known as planchets or flans - at a rate of 20,000 per minute, or up to 15 million per day. After punching, beading is applied to the blanks to give them the typical rim which determines the basic shape of the dies in the mints. Cold reduction hardens the material to such an extent that before being struck the blanks have to be soft annealed at temperatures of 900°C. This process is a balancing act - on the one hand the blank has to be solid enough to survive the minting process, on the other hand it must be soft enough to allow a good impression.
The company`s annealing operation also had to undergo significant changes. In addition to the drum type furnaces, continuous furnaces were installed: This process is gentler and consequently better for the delicate rings, though the blanks lose much of their shine in the necessary heat treatment. The downstream processes were also modified. Previously barrels were used for washing, polishing and preserving - and each of these processes was carried out individually, involving a lot of manual work. Centrifugal systems were introduced in Werdohl using ceramic or steel pellets. Three parallel lines were installed in the finishing center which carry out all three processes in a single step. After "laundering" the blanks can then be dried with hot air and repolished.
The all-important quality control system was also overhauled. No matter how carefully managed, no production operation is one hundred percent defect-free. In the normal course of production surface defects such as scratches, dents or stains occur which make it necessary to carry out a final visual inspection. At ThyssenKrupp VDM every blank is inspected on both sides. At first all blanks were inspected on sorting belts by specially trained staff. A few years ago the first specially developed automatic image processing systems with cameras were introduced. The first generation of these control systems could inspect 20 to 25 blanks per second. Higher-performance second-generation systems have since been installed in Werdohl which can handle 40 to 50 blanks per second. However, all the blanks rejected by the cameras are checked again by inspection staff.
The quality management team also carries out random measurements with lasers which check the diameter, potential ovality and centricity at a total of 40 measuring points. In addition, for the centers of the 1 and 2 euro pieces the magnetic moment of the nickel core is measured against a reference value.
ThyssenKrupp has a 30 percent share of the market for the higher-value 1 and 2 euro blanks, as against 10 percent for the full range of euro coins. The company which first obtained approval for the minting of coins from copper nickel back in 1873 is thus now writing a new chapter in its success story.
For more information:
ThyssenKrupp VDM GmbH
Heinz-Jürgen Möller, Head of Sales Organization and Marketing Services
Tel. +49 (0)2392 55 25 01
Fax +49 (0)2392 55 25 96