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<< Figure 3: Mandrel (left) along with the finished nickel electroform used to make reflector elements. Below right: enlarged section. >>
Another advantage of the procedure is its cost effectiveness. When producing moulds and dies, there are options that are simply impossible when using conventional methods. When making steel moulds, it is not necessary to work with solid material. By casting electroforms from an easy-to-work-with plastic mandrel, it is possible to manufacture high quality nickel tools. Identical tools can be produced very economically by repeated casting.
At this point, we should take a look at some of the limitations of electroforming. When using a mandrel which has recesses in it, any narrow slits only receive a thin coating of nickel. Deposits are thickest in areas of high current density, which are at their highest on the edges and their lowest in recesses. This limitation only really affects macroscopic objects. Microscopic objects, e.g. narrow recesses of 100 μm with a width of 10 μm, can be cast without any issues. This is due to the electrolyte’s ability to disperse the dissolved nickel. Whether or not a mandrel can be reused for further casts depends on the structure of its surface. If there are undercut areas on its surface, it cannot be separated from the electroform. In such cases where an exact duplicate of the surface is required, the mandrel is destroyed once the depositing process is complete.
Electroforming microscopic structures Some examples of electroforming microscopic structures are given in the following paragraphs. The casting of reflectors, for example those used for rear reflectors in vehicles, requires a microscopically accurate reproduction of surfaces and edges. If an injection mould exhibits minor abnormalities, this leads to degradation of the reflective qualities. Figure 3 shows, from left to right, the mandrel (A mould), the electroform (B mould) in pure nickel and an enlarged section of the honeycomb (viewed from above). This electroform can now be used to manufacture reflectors.
Another advantage of the procedure is its cost effectiveness. When producing moulds and dies, there are options that are simply impossible when using conventional methods. When making steel moulds, it is not necessary to work with solid material. By casting electroforms from an easy-to- work-with plastic mandrel, it is possible to manufacture high quality nickel tools. Identical tools can be produced very economically by repeated casting.
20 | commercial micro manufacturing international Vol 6 No.5
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