Block Slabbing at the Quarry
By Alice Tori, Romina Brocco and Paul Daniel
Diamond wire – a multi-strand cable with diamond cutting elements called beads – was invented independently by two British engineers in the late 1960s. One gave up because of frequent wire breakage; Derek Prowse persevered and emigrated to Carrara, Italy to carry out more trials. The early beads involved electroplating nickel with diamond particles in suspension onto a metal carrier.
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Meanwhile Luigi Madrigali invented a machine with pulleys nicknamed “the bicycle” to carry the diamond wire. The basic machine concept was refined and developed by commercial companies for use in marble quarrying.
Improved diamond wire and machines made an appearance in Carrara marble quarries in 1978-79. The first commercial use of diamond wire for quarrying of non-calcareous stone can be traced back to 1985; by late 1987 successful results were reported in granite. The first use of a multi-diamond wire (MDW) machine on hard granite came in 1986.
In 1997 Wires Engineering and sister company CO.FI.PLAST announced the Falcon 610L machine with 10 diamond wires/beads of 8mm diameter for granite block slabbing. Cutting 4cm slabs of Class V granites, production rates of around 200 m² / 2,152 ft² day were reported.
Several companies currently offer MDW machines for block slabbing, but CO.FI.PLAST / Wires Engineering now offers a complete ´in-quarry´ solution to economical and more-sustainable production of high-quality granite slabs.
FORWARD THINKING
Marbrasa Mármores e Granitos do Brasil Ltda was founded in 1968. Initially, Marbrasa centered its business on the Brazilian market, but now has representation in more than 40 countries; company and group headquarters is in Cachoeiro de Itapemirim.
A marble quarry was acquired in 1973, and Marbrasa still extracts from the area today. However, granite became a huge profit center, and now represents approximately 85% of production; some 6,000 m³ / 211,888 ft³of granite block is extracted monthly.
Click photo to enlargeMarbrasa´s leading material is Nero Sao Gabriel black granite, accounting for close t half of sales, but many colored granites (including yellow) are sold as well. The company never left its marble quarrying and processing behind The group´s white marble is especially popular.
The company was among the first in South America to import European machinery from Europe. The group currently has nine of its own quarries and state-of-the-art processing factories including a 50,000 m² / 538,195 ft² main facility.
“From the start we were set on using the best technology to extract stone from our quarries,” says company director Elvis Gomez.
With quarry and factory production continuing to expand, Marbrasa decided to continue with its capital-investment program. Factors such as the depreciation of the Brazilian real and the recession in the United States and Europe and the US motivated the company to seek additional markets.
Meanwhile the home market will receive a boost from all the new infrastructure needed for the FIFA World Cup games in 2014 and the Olympic Games in 2016. The overall business situation looks bright for the South American market leader; Acquisition of a new integrated quarrying and processing system was a logical step.
MACHINERY AND WIRES
The Brocco group, with headquarters at Lessolo, Italy, has 30 years’ experience in cutting stone. Group members CO.FI.PLAST and Wires Engineering test each other’s products in unison, allowing the two companies to accumulate experience and build up a unique know-how.
Wires machines employ a patented wire tensioning system which maintains the optimum tension of each wire in the set. Furthermore, by absorbing vibrations, diamond-wire life is extended. In another patented system, positioning of the wires can be varied to allow the simultaneous production of slabs of different thickness (2-3-4-5 cm and multiples). Machines can be fitted with 8, 20, 30, 40 or 65 diamond wires.
Emilio Brocco, the group founder, introduced plasticization of the diamond wire as a replacement for metal springs between the beads, improving safety and increasing wire life. Plasticization of the diamond wires opened up a new world of application: granites and other difficult-to-cut stones.
