This article was originally printed in World Coin News.
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By Richard Giedroyc
Study your coins and you will find some have die cracks, raised lines resulting from the later state of a deteriorating die from which these coins were struck. The die was wearing out due to metal fatigue. The logical answer to how to avoid such problems is to give coinage dies a longer life by producing the dies from a harder metal.
Harder metals, such as steel, come accompanied by another problem. Traditional mechanical engraving requires additional working processes as well as hardening time. When the material is hardened the image may become somewhat distorted. This in turn will require further time and labor preparing the die to be ready for use.
Solving this problem may not be rocket science, but it does involve laser science. One of the companies addressing this technological breakthrough is FOBA Laser Marking & Engraving Solutions. Founded in 1969 as a mold construction and engraving facility, today FOBA is part of ALLTEC GmbH., which is under the wing of parent group Danaher Corporation. FOBA’s headquarters are in Selmsdorf, near Hamburg, Germany.
FOBA’s GP9000 laser engraving machine is a lightweight design machine that saves time and labor in the die production process, while offering additional bells and whistles that might not otherwise be able to be utilized for additional coinage security.Laser die manufacture involves engraving the desired coinage images directly onto the die after that die has gone through the hardening process. Since image distortion resulting from the hardening process won’t be a problem this invites adding further product innovations. Images unable to be achieved using hand crafting techniques may become a reality when employing laser technology. Security features such as micro inscriptions and micrometer-size symbols can be added to a working die in a consistent and extremely accurate way, also saving time since a die engraver was not involved using any additional manual labor.
The laser process developed by FOBA involves creating a coin design model, this model being digitized in the following step. First the plaster relief model is scanned using a three dimensional scanner. A three dimensional point cloud of this scan is then exported as a STL model.
A live image of the die blank is recorded by an IMP camera system and is displayed in the FOBA EMC. The scanned three dimensional data is opened in ArtCAM Pro engraving and relief software. At this point the image data is edited and processed. All images are positioned as two-dimensional vectors, with the two-dimensional graphics then being transferred into three-dimensional relief. All text, relief data, and enhancement file data are compiled. In the next step the three-dimensional models, already having been compiled into layers, are appropriately split by the software. The data is imported into the FOBA EMC, which will control the software for all engraving for the FOBA engraving lasers.
The GP9000 laser engraving machine applies the appropriately processed data to the blank hardened die surface using a high precision laser beam. The male mold is then subjected to electro-chemical machining. Working dies are sandblasted using a glass bead treatment, then polished. Any frosting, latent images, and micro images are then added using the laser. The die is then electroplated and is ready for use.
FOBA acknowledges that laser engraving of a die is time consuming when compared to CNC milling processes, however laser technology overrides the limitations of the die hardening process when processed steel or other harder metals are being used. The laser technology offers significant advantages when die manufacturing requirements exceed the limits of what can be done using traditional mechanical processes. This should lead to a superior quality coins in the future.
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