Multi-Wire Saws Gains Ground

By Paul Daniel
  Unlike weapons of mass destruction (WMD), the proliferation of multi-diamond-wire (MDW) machines is completely verifiable.
  “Multi-wire sawing is still being developed and has yet to reach its full potential,” says Stephen Kelly, project engineer with Element Six (formerly De Beers Industrial Diamonds) at the group´s Market Support Centre in Shannon, Ireland.
  That is undoubtedly true, but there’s been a significant growth in sales in the past three years.
  Diamond wire – initially diamond electroplated beads threaded onto a multi-strand steel cable – was invented in England in the 1950s. A lot of development work (by Diamant Boart, among others) was needed to refine the concept; it wasn’t until the past 25 years that diamond wire was commercially accepted in Carrara marble quarries in Italy. Further machine and wire developments were needed for hard-rock sawing.
  Within the stone industry, there are three types of diamond-wire machines – and all used for completely different application areas.
  The first type is mobile and has a single wire for stone extraction in the quarry. It was estimated in 2003 there were, worldwide, around 2,000 machines of this type in use for quarrying marble and limestone, and a further 1,000 for extracting hard rock. Stationary monowire machines are mainly used for block squaring or profiling. 
  MDW machines are the newest type and, in 2003, it was estimated that there were some 50 in operation worldwide. In early October 2006, that number had grown to approximately 110.
  MDW machines can again be subdivided into two basic types: those for cutting thick slabs, and those for cutting thin slabs. Machines with 30 wires or more are primarily used for granite-block slabbing where they compete with, or complement, traditional steel-shot gang saws. Machines with a lesser number of wires are used for sawing thick slabs for monuments or architectural parts.
  Tests began in 1994 with a prototype MDW machine developed by Yamana Co. in Japan with cutting granite. The machine was equipped with 10 wires, with a bead diameter of 10mm. It’s believed that no production machines were ever developed.
  In 1997, Wires Engineering S.r.l. of Lessolo, Italy, announced the Falcon 600 machine with 10 diamond wires  and beads of 8mm diameter. Cutting 4cm slabs of Class 5 granite, production rates of around 250 m² (2,690 ft²) a day were achieved.
  In 2000, Bideseimpianti S.r.l. of Fara Vincentino, Italy, delivered a 50-wire machine to Granisa of Porriño, Spain. (The machine was later modified to take 58 wires.) Wire diameter was 4mm and diamond-bead diameter 6.7mm. Around 20,000 m² (215,278 ft²)of 2cm-thick Class 3 granite slabs were sawn per month, compared with about 6,000 m(2) (64,583 ft²)with a steel-shot gang saw.
  By the end of 2006, Bideseimpianti expects to have sold 20 of their GOLD 30 / GOLD 60 MDW machines, and believes they compare favorably to traditional steel-shot gang saws.
  Also in 2000, Pellegrini Meccanica S.p.A. of Verona, Italy, launched its range of Polywire machines. The  Polywire 5/16, as its designation suggests, can be fitted with between five and 16 diamond wires for cutting slabs in thicknesses from 2.1cm-15.1cm. Today the company also offers 30 and 32-wire models; the company notes that a single machine offers the production of three steel-shot gang saws.  
  Meanwhile, in the United States, Cold Spring Granite Co. (CSG) decided to design and build their own MDW machines. The first machines were in operation around 1996.
  Ray Jaeger, Cold Spring engineering manager, confirms that CSG has MDW machines in California, Minnesota, New York, South Dakota, Texas and Canada. Some of the machines are used in the quarries.
  The 15-wire CSG saws located in Texas and Minnesota are computer-controlled, automatically lubricated and run unattended using electronic censors that monitor the sawing process. All saws run on recycled water with a consumption rate per wire that is less than or equal to 1.5 gal/min.
  Despite all the advantages of the MDW system compared with traditional steel-shot frame saws, demand for granite slabs was not great in Europe in 2000/2003, so further sales of new machines were slow in coming. All that changed in 2004 with increased stone production.
  To gauge the market today, the heads of the three European industry MDW leaders responded to two questions: “What, in your opinion, are the main reasons for the increasing acceptance of Multi-Diamond Wire (MDW) technology?” and “Do you expect purchases of MDW machines to grow significantly?”
  Ilario Bidese, Bideseimpianti: “It is not a question of acceptance by the customers but a strong demand. Many people around the world already knew the benefits of MDW technology, and now they are ready to order it.
  “We think that only those with a minimum of 30 wires can be considered as real MDW machines. The reason is the capability to cut one full block in only one or a maximum of two passes. We are sure that for this type of application, the demand will increase in the immediate future. Some customers have decided to add on a MDW machine in addition to their traditional gang saws, in order to become more- and more-aggressive in the market.”
  Emilio Brocco, Wires Engineering/Co.Fi.Plast: “In my opinion, there are several reasons for the increasing acceptance of MDW machines:
  • it is not necessary to have highly skilled technicians. An operator can be trained within five working days - he can run the machine, under supervision, after the first day;
  •high output, low energy cost, better working environment;
  • high flexibility regarding output (eight-hour cut);
  • great versatility regarding the range of materials that can be cut using the same machine, i.e. marble, limestone, slate, granite, basalt, sandstone, etc.;
  • low machine maintenance;
  • low machine cost considering the high production capacity;
  • kerf width (diamond-bead diameter) of only 7 mm; and
  • the possibility ( on our machines ) to change wire spacing/slab thickness in a few minutes.”
   “Yes, of course. We expect to see about 20 new MDW machines every year. However not all  will have 72 wires like our Arianna XF 72 model which entered service with IGS (Industria Graniti Sardi) in late September 2007.”
  Gianluigi Biasco, Pellegrini Meccanica: “The main reasons for the increasing acceptance of MDW sawing are :
  • fast cutting speed;
  • you can cut difficult materials too;
  • easy to use and high flexibility considering (on a Polywire machine) the quick thickness change;
  • low maintenance costs;
  • small installation area; and
  • simple and inexpensive machine foundations.”
  “We think that the number of MDW machines in use will increase significantly ".
  There are several thousand traditional gang saws in use around the world today. The first models were installed in the mid-1950s, and steel shot was introduced around 10 years later.
  With a 5mm wide steel blade, the kerf (cut) width is 6.5mm, according to Gaspari Menotti S.p.A. of Carrara, Italy; 7mm, according to Barsanti Macchine S.p.A. of Massa, Italy; and 8.5-9mm according to Pellegrini. Do the traditional machine makers now see a threat from MDW machines in granite slabbing ?
  Sr. Loverdi, commercial manager (retired), Giorgini Maggi S.r.l., Pietrasanta, Italy: “The surface finish is better with diamond wire, but I think the accuracy is better with the traditional gang saws. And the cost?”
  Luca Mordenti, area manager, Barsanti: “We have just sold six so-called traditional gang saws to Marmi Bruno Zanet for their factory in Vitoria, Brazil. I think that says it all!” (Author’s note : Bideseimpianti also sold a GOLD 60 machine to the same factory).
  Carlo Bastianello, director, BM S.r.l., Montorso Vicentino, Italy: “I believe our costs are half that of the MDW method .”
  Dr. Alessandro Galleni, area manager, Gaspari Menotti : “MDW machines are worth having for peak times of demand. I might advise a new client to buy three traditional gangsaws and one MDW machine to satisfy fast demand.”
  In conclusion, it could be said that, in general granite slabbing, costs are currently higher with MDW machines, but the faster slab production is very useful in peak demand times. 
  Paul Daniel holds years of experience in the industrial-diamond trade. He now covers the stone industry as a freelance journalist based in Los Alcázares, Spain.
 This article first appeared in the December 2006 print edition of Stone Business. ©2006 Western Business Media Inc.