Laboratory characterization aimed at analyzing the performance of diamond wires for marble cutting

Over the years the diamond wire has got many improvements and optimizations, thanks to which one of the greatest revolutions in the stone industry took place. However, its use is still the cause of injuries, sometimes fatal, following the opening of the loop during cutting, with consequent whiplash and high-speed projection of its elements. The present work is focused on the study of some possible causes of diamond wire breakage, from those known, including slipping of the support cable from the junction clamp and cable break near the clamp, to that, observed in quarries of the Carrara Basin during on-site analyzes, of breaking the same junction clamp. To help improving the safety level in the quarries, tensile tests were carried out at the “Marmotest s.a.s” laboratories of Carrara and DISEG of the Politecnico di Torino on wire elements, in detail junction clamps, pressing devices and support cable, supplied by the ‘Megadiamant Srl’ manufacturer of diamond wires, reproducing configurations and technological choices observed on site and assessing compliance with the European reference standard UNI EN 13236:2016 (“Safety Requirements for superabrasive products”). 100% of pressing devices and more than 90% of junction clamps subjected to slip tests have respected the limit value imposed by the reference standard. For the latter, three factors mainly contribute to the slip resistance: the type of material, the length of the junction clamps and their thickness. Despite the research carried out, no technical documents are available regarding the chemical composition of the materials with which the joints are made but, in general, the clamps marketed as copper (or, more properly, copper steel) and annealed steel have provided greater extraction resistances than those in steel. Furthermore, the slip resistance is linked to the length of the clamp by direct proportionality, and its thickness by inverse proportionality. The water for cooling the diamond wire during cutting may not be used correctly or be limited byenvironmental problems. For this reason, the study of the slip resistance of copper and steel clamps has been extended, including the variation of their properties to temperature increase. Finally, the deterioration of the mechanical characteristics of the diamond wire following the cutting was measured by performing tensile tests on used elements.