Published at 04.03.2021
THIEME introduces a highly productive inkjet printing system for printing on coins and bars in multicolor.
The market for colorizing coins and other precious metals is growing, making it all the more important to have an efficient, economical printing process. THIEME has taken a quantum leap in efficiency with an innovative digital coin printer. This unrivaled system is the first machine of its kind to print more than 600 coins per hour in a largely automated, highly productive printing process.
Colored coins – coins with partly colored minted motifs – are spectacular showpieces that are becoming increasingly popular among collectors as well as other users. Applying color adds variety to the otherwise limited design options in minting, which is why almost all official mints now offer colored coins. To achieve perfect printing results on three-dimensional minted reliefs, the coin blanks have to be precisely aligned prior to printing. In addition, the applied ink has to be stable enough to allow the colored coins to survive the final roller burnishing process intact.
Until now, most coins and other precious metals were printed using screen or pad printing methods. Thieme, working with a German mint, has now developed a new type of digital coin printer that significantly speeds up the printing process. Its one-of-a-kind inkjet printing system employs special tested inks that offer optimum adhesion and abrasion resistance when applied to metal substrates. The system offers a total of seven color channels (CMYK, white, primer and topcoat); a fluorescent clearcoat is also available for special luminous effects.
Efficient loading, automatic alignment
Extensive automation and easy loading are essential for an effi-cient printing process. The Thieme coin printer uses an entirely new approach with exchangeable adapter trays in which operators can load a large number of coins or bars at a time. The double table design allows parallel loading/unloading and printing with a cycle time of approx. 180 seconds per tray. That translates into 640 coins per hour when each tray is loaded with 32 coins.
The innovative automatic alignment system provides yet another efficiency boost: Digital Image Alignment allows the blanks to be inserted into the press in any position – a scanning process auto-matically adjusts the stored print layout to the orientation of each individual coin. Digital alignment takes only one to two seconds per coin and is therefore much faster than mechanical holder position-ing in conventional printing processes. “We have increased throughput many times over what was previously possible,” ex-plained Oliver Beck, Head of Sales Printing Systems at Thieme. The innovative system also offers unbeatable printing costs, he added: “Ink costs less than one euro cent for each 32-millimeter coin.”
High print quality and productivity
Print quality has not been sacrificed for better productivity. On the contrary, the print resolution of 800 x 1500 dpi can colorize the most delicate minted motifs in high quality. Automatic alignment is also highly precise with a repetition accuracy within ± 0.1 mm. “Our new inkjet printing system revolutionizes the current coin coloriza-tion process,” promised Oliver Beck. “The printing process used to be rather laborious. In the future, coins and metal substrates can be colorized far more efficiently and flexibly while maintaining high quality standards.” This efficiency gain is crucial in a time of rising demand: “For mints, this is a real quantum leap.”