Silvia takes us with her jeep to see the Carrara quarries. She carefully climbs the winding road to where the marble is cut. Up here, the air smells of marble dust, a white powder that reflects the rays of the sun and makes us think about how difficult it would have been in Michelangelo’s time to extract marble from these quarries and transport it to the sea.
Today, the “diamond wire” allows them to cut off chunks of mountain at an incredible speed; if once, it took a month and a half to make a cut, today the same cut is made in three or four days. The “diamond wire” is built like a pearl necklace, hence the name “beads” given to the small cylinders that are strung on the cable, small artificial diamonds, spaced apart by small springs. The only serious drawback of this method is that, when the cable breaks, the beads fly off like bullets. This is why workers must always be at a safe distance when the machine is in motion.
The general operating principle of diamond wire cutting machines is to engrave a rock by dragging a dynamic device with an abrasive action. The cutting element of a cutting machine is the diamond wire, which is arranged in a closed circuit around the section to be cut and is wet with water whilst cutting for it to cool .
The closed circuit is made possible by the preliminary creation of two intersecting holes through which the wire is passed, to then be closed in a loop. This drilling is carried out with perforating machines capable of drilling holes with diameters from 60 mm to 205 mm in all directions. During the execution of the cut, the wire receives and maintains a constant tension thanks to the progressive translation on tracks of the machine that puts it in motion. A cutting machine can operate at all angles and according to various criteria, depending on the type of cut to be performed. The machine consists of four basic parts: the frame, the drive section, the control unit and the diamond wire. The diamond wire is the heart of the system; in its standard configuration it is composed of a stainless-steel cable with a 5 mm diameter that absorbs static and dynamic stresses and supports the diamond beads or bushes. The cylindrical elements, that have an external diameter of 10 mm, are threaded like a necklace on the wire and are the element that causes the cut itself.
