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The Unidisc Mk2 is designed to produce 3mm diameter discs for electropolishing, and subsequent TEM examination, from sample strips
Sample strips are fed into the side of the Unidisc Mk2. When the handle is pulled, the strip is trapped between two rigid metal die faces. The punch then pierces the tightly held sheet and ejects the disc into the collection tray. Deformation is confined to a very localised shear zone at the edges of the disc away from the central region which is later thinned (see Metalthin). The punch and die are easily replaceable items made from hardened tool steel. A detailed view of the punch assembly is seen on the right.
The standard model produces 3mm discs for TEM from sheet/foil samples with minimum distortion.
Optional punches and dies to produce discs from 1mm to 6mm in diameter can be easily fitted. Examples of the use of these includes the production of 1mm discs of highly radioactive materials which are pressed into holes punched in non-radioactive 3 mm discs and the composite disc thinned (see Metalthin). This reduces the radiation dose to the personnel involved. The larger disc specimens are used in SEM.