The micro pins shown in figure 4 can only be manufactured by electroforming. The left-hand portion of the picture shows the finished nickel tool (B mould). This is then used to press microscopically small pins (the C mould) in acrylic. If you were then to use this C mould as a mandrel, a new nickel tool could be cast.
Micro prints, such as those shown in figure 5, are often used as a security feature on identification cards. If the lettering should be perceivable by touch, it is usually stamped in plastic. Nickel electroforming is ideally suited to the purpose of casting micro prints from a mandrel. This avoids the need for elaborate batch production, for example by laser machining.
Optical security features can also be produced by electroforming. Micro lens elements are one such example. The tiny lens elements (over 100 per cm) are stamped in plastic using a nickel electroform. When looking at the finished identity document, you then see a picture or number, depending on your angle of vision. An advantage of this manufacturing process is that a great many nickel replicas can be produced from just one mandrel (also known in the industry as a master). This also avoids the need for conventional batch production.
Nickel electroforming is also used in the production of even finer-detailed objects. Holograms are one example. Embossed holograms are a cost-effective way of incorporating security features in banknotes. A stamp is used to press a suitable pattern into a film that is coated with a reflective material on the rear. These embossed holograms are very difficult to forge. An example of a holographic film is shown in figure 6.
Nowadays, nickel electroforming is not used to its full potential, although the advantages of this technology are obvious:
- The replication of special surfaces that cannot be produced by mechanical means
- Extremely accurate reproduction down to the nanometre - Multiple casts from one mandrel (or master) - The nickel electroform has a high level of wear resistance and is extremely durable
- Nickel is highly resistant to corrosion by a number of aggressive media
- High level of heat conductivity.
www.elektroform.eu
23 | commercial micro manufacturing international Vol 6 No.5
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