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STEMMER IMAGING presents a custom-made automated marble refining machine

Updated: Jun 21, 2021

A highly sophisticated custom-made machine from Böhm AG in Thuringia is the first of its kind worldwide to enable the fully automated refinement of marble. The innovative system uses machine vision from our partner STEMMER IMAGING to guarantee the reliable removal of undesired structures in the stone reducing its value.

Marble is one of the most decorative construction materials in the world and highly valued as a high-class finish in buildings such as hotels, airports or upscale residences. No marble slab is identical to another, as inclusions, cracks or so-called veins shape the appearance of the naturally formed stone and always create a unique look. Depending on the number and characteristics of such flaws, marble is divided into three quality classes, which generate different prices on the market.

Special requirements apply to highly decorative buildings. The marble slabs should be as uniform as possible in colour and free of impurities. How close the stone comes to the ideal, however, only becomes apparent when the large blocks excavated in the quarry are sawn into slices. In terms of colour, slabs from one block are usually quite similar.

However, veins caused by sedimentation during the formation process can considerably spoil the appearance due to their sometimes strongly deviating colours and thus significantly lower the value of individual marble slabs.

With the BMM (Böhm Marble Machine) introduced in autumn 2019, Böhm AG, based in Zella-Mehlis, Thuringia, has developed a solution which enables the fully automated finishing of marble for the first time. The two BMM variants used for refining these two slab formats come in lengths of 14 and 32 metres, respectively. Depending on the degree of perfection, the larger version refines up to 1000 m² of natural stone surface in 12 hours, while the smaller one manages up to 400 m² in 12 hours.

The inspection results obtained by the machine vision module used in the very beginning are the basis for all subsequent steps performed on the BMM. Precise positioning of the imperfections is an essential prerequisite for the laser treatment, which should only remove the structures that actually reduce the value.

The image acquisition module is based on two trilinear RGB line scan bars from Mitsubishi Electric with widths of 600 mm and 900 mm respectively and built-in lighting. A Teledyne DALSA Xtium CameraLink frame grabber is used to transfer the image data to a customized PC, where the partial images captured by the two line scan bars are combined and evaluated with the help of STEMMER IMAGING's machine vision programming library Common Vision Blox.

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