Microhardness in the music industry
Metal hardness measurement is a common part of many industries. This is no different in the music industry, for example in the production of gramophone records. The properties of the copper layer into which a positive sound track is engraved during the mold preparation phase are decisive for the quality transmission of the sound track. This serves as a basis for the creation of a nickel negative matrix, into which the plastic of the resulting gramophone record is pressed by pressure. The hardness of copper before engraving the positive form affects the process and quality of the recording of the sound track. At low hardness, the material is not tough enough for the next process of production of the negative mold and the engraved layer is deformed. The high hardness makes it difficult for the engraving tip to penetrate the material and for a sufficiently fine trace to form. Unlike conventional microhardness measurement, where it is necessary to first create a metallographic sample, the measurement on the copper layer is simple thanks to a smooth surface with optical properties without the need for further modifications. The only limit is the layer thickness of 150 µm. Therefore, it is necessary to choose the correct loading force in order to follow the principles of measuring and the effect on the mass of material under the impression. A Future-Tech FM-110 microhardness tester with the Microness image evaluation program was used for this measurement.