New Methods,
New Practices,
New Possibilities

By Mark Haverstock

Methods used today in stone quarrying and manufacturing are an interesting mix, ranging from classic craftsmanship to cutting-edge technology. In a small quarrying operation, one still can find people using feathers and wedges to split stone, something that has not changed for a thousand years. But at the modern end of the spectrum, quarries are cutting stone with diamond saws, while fabricators use robots and the latest in computer technology.

As we enter the 21st century, one could say that we're entering a new Stone Age. Contractors and homeowners are looking for the beauty and permanence of stone at affordable prices. Quarriers and processors of natural stone are looking to new technology to help them meet this demand by better utilizing their resources.

From the Ground Up
The object of quarrying stone is to remove large, rectangular blocks with the least outlay of time and labor, while keeping the quarry in good shape. In the days of old, that meant brute force and explosives. "One of the things we used to do is spot drilling — you drill a hole and then use the impact of the drill to crack the stone," said Tom Howard, plant engineer for Cold Spring Granite of Cold Spring, Minn. "At the end of the process, you'd use explosives to lift it out."

For the past five years, Cold Spring has been using a process called quarry wire sawing, which requires no dangerous blasting and gives workers more control over the process. "What we do is drill two holes into the ground and we string diamond wire through the holes — which is diamond segments impregnated in a wire with a resin or plastic," Howard said. "The wire is run through a saw and the saw pulls the wire through the ground and cuts out the block."

According to Howard, when you use explosives, you put stress on the stone, which can cause it to crack. But with the wire sawing, you get better quality stone, especially for stone that is brittle. "We started with some of our more brittle stones and have increased our yield quite a bit by using wire sawing instead of blasting and flat drilling," he explained.

Belt and Blade
Another useful quarrying saw is the diamond belt saw. Diamond belt saws from W.F. Meyers cut anywhere from 6'3" to 16' depth at 200 square feet per hour. The cutting unit weighs approximately 8,000 pounds and travels on railroad-like tracks into the quarry. To decrease setup time, each model utilizes a rotating guide bar that allows users to cut on either side of the machine. By adjusting the cutting widths, users can maximize the number of usable products. "You get nice square blocks and you don't fracture the stone," said Dick Dunlap, sales engineer for W.F. Meyers of Bedford, Ind. "This means more usable material and less waste."

Cutting quarried material also utilizes the hardness of diamonds, and manufacturers continue to refine this technology. Slab saw and narrow block saws from W.F. Meyers use .530-inch-wide diamond belts. "With limestone, it cuts anywhere from 15 to 19 inches per minute," Dunlap said. "You can cut up a bunch of stone with one machine very quickly."

For sectional fabrication, ripping or jointing, diamond circular blades have been the standard for a number of years. They deliver the cutting power needed to help process the maximum amount of square feet per man hour. Meyers' skilled sawsmiths design Dia-Brasive® blades according to customer specifications by calculating the size, concentration and diamond type for optimal performance.

The Jaguar Saw from Park Industries of St. Cloud, Minn., utilizes diamond blade technology to do precision, straight-line profiling. "It allows you to make coping material and surrounds for all straight-line profiles like window sills, and window and door surrounds," said Jeff Walerius, architectural division sales manager for Park Industries. "This is one of our simpler machines to operate — it doesn't require CAD training or experience to run. You simply download a .DXF file to the machine." The intuitive touch screen walks you through the process, so users only need basic PC skills.

Finished stone cuts.
Photo courtesy of Park Industries

To Infinity and Beyond
Another addition from Park Industries is the company's Infinity line, which raises the ante over conventional saws by giving precision sawing performance with the ability to change over and do complex shaping using industry-standard milling attachments. "The Infinity profiles stone for your applications, such as columns, archways, door surrounds, window surrounds, fireplace surrounds — anything that you want cut in a 3-D format," Walerius said.

The Infinity is a three-axis computer numerical control (CNC) profiling machine that utilizes Mastercam, a type of software that is structured so an operator can enter minimal data to allow the machine to function. Interfaces include both keyboard and mouse, as well as a touch screen. It also uses a Siemens DMI control, which has a keyboard and mouse built right on the interface. The machine accepts instructions in both English and Spanish.

"Operators need some basic CAD experience to run the equipment," Walerius explained. "You can take any .DXF file, download it to the machine, and they can take and manipulate that drawing and produce the product." Park also recommends some knowledge of G-code, a common CNC programming language, for best results. "We do an intensive 10-day training session here at Park Industries, teaching the standard operating and programming procedures that an operator will need," Walerius said. "They learn exactly what they need to know to produce the particular products they make."

A Cut Above
Omax of Kent, Wash., produces a line of JetMachining® Centers that utilize an abrasive water jet cutter that can trim a large variety of materials, including stone, such as marble and granite. Many stone fabricators utilize water jets like these to process stone for sink cutouts, inlays and just about any kind of three-dimensional cutting.

The abrasive jet pressurizes water up to 55,000 pounds per square inch and then forces it through a small sapphire orifice at about two and half times the speed of sound. Garnet abrasive is then pulled into this high-speed stream of water, and mixed with the water in a long, ceramic mixing tube. A stream of abrasive-laden water moving at 1,000 feet per second then exits the ceramic tube. This jet of water and abrasive is then directed at the material to be machined. The jet's cutting action is a grinding process, but instead of using a solid grinding wheel, the forces and motions of the cutting action are provided by water.

"We also have a new product called the Fabricator, which is well suited to the stone industry," said Sandra McLain, OMAX vice president of marketing. "It cuts large pieces — the unit can handle 12- by 12-foot pieces and can grow in length by 72-inch increments if needed." The unit is run by a CNC motion control system incorporating Windows XP, accepting standard .DXF files. According to McLain, the Fabricator's abrasive jet excels at contour cutting and producing intricate shapes with precision.

	The SEIS RoboJet provides the accuracy of industrial robotics and the flexibility to automatically switch between abrasive water jet cutting, rotary saw cutting, 3-D milling and edge profiling. Photo courtesy SEIS Group Inc.

Lending a Robotic Hand
Since the 1960s, when the first industrial robots took their place on factory floors, their numbers have increased to approximately one million around the world. A decade ago, these machines began finding their way into stone fabrication and finishing. "The stone industry can now benefit from the same kinds of automation technology as other industries, such as automotive or general manufacturing have been using," said Brian Mullins, chairman of the SEIS Group of Huntington Beach, Calif. "It takes what was traditionally a very manual process and brought some levels of machining to it."

The typical CNC manufacturer ships units in the hundreds per year. However, these robots are sold in quantities of 7,000 to 8,000 a year, and have an installed base of more than 70,000 units. "You get a much different level of support for this kind of product than you do for traditional stone equipment," Mullins explained. "Also, the mean time between failures — the typical time before you have to do any work on the machine or the robot — is about seven years, which is a level of quality you can't get with old-style machine tools." Modern automation standards require that similar robotic arms assemble cars 24/7, without any downtime, and are expected to do so for the life of the product line.

The SEIS RoboJet combines the capabilities of a water jet, a CNC saw and an edge profiling CNC to do all kinds of routing and CNC work. "For the price of one machine, you get the capabilities of three," Mullins said. "The footprint is also smaller, so you can fit more capability into a facility."

RoboCut software controls water jet cutting on this granite countertop. Photo courtesy SEIS Group Inc.

In addition to engineering tools and how the robot utilizes them, SEIS also writes the software running under Windows XP. They took standard industrial robots that typically are programmed very differently from CNC machine tools and produced software that allows you to program them, much like a traditional CNC. "It gives our users a lot of flexibility, but also ease of use," Mullins said. "Anyone who uses our machines will find it very intuitive and familiar. You can take the same CAD files you generate now from your countertop templates, for instance, drag them right into our software, and then run them as you would on a traditional CNC." This means no steep learning curve, since operators can utilize their current knowledge and experience.

Mullins noted that, in 2007, SEIS will release another tool that will compliment the current water jet, the saw and milling devices. "The robots will give even more flexibility — you can add a new tool, and perhaps more later on," he said. "Soon, we can bring as many of these tools as possible into one machine center so you can create a better product more efficiently."

Cutting Corners Constructively
One of the hottest items in the natural stone market is thin stone veneer. New technologies are making it easier to efficiently utilize stone to make face and corner pieces. "[Park Industries has] two versions of our ThinStone TXS System, one that cuts the flats and a new machine that cuts the corners," Walerius said. "The advantage of using the corner machine is that it cuts in a single pass." In the past, corners were made using hand chop saws — a very cumbersome, dangerous and labor-intensive task.

Making corner pieces can be particularly wasteful, unless care is taken to utilize the maximum amount of stone. The process on the Park TXS-4500 system begins with sawing a roughly rectangular piece of full veneer, ranging from four to 12 inches thick, one corner at a time, producing two corner pieces and a leftover piece from the middle. "A lot of our customers are taking that middle piece that is cut on both sides, and they are either tumbling and making another product from it, or they are splitting it again to process," Walerius said.

"The efficiency of stone utilization and yield of stone has been an issue in the past for quarriers," added Stephanie Kadlec, marketing manager for Park Industries. "You visit some old quarries and there are some huge rubble piles, thousands of tons of stone that was thought to be unusable. But with these veneer machines and other modern technology, they're able to reduce those rubble piles by turning the 'junk' stone into profitable stone."

Stone for the Masses
Modern stone cutting and fabricating machines reduce labor, labor costs and increase efficiency that can ultimately be passed on to the consumers, making natural stone more affordable. "Ten years ago, only the million-dollar homes had marble countertops and stone exteriors; today, we're seeing homes in the $250,000 bracket with similar stone products," Kadlec said. "Natural stone is becoming more affordable due to technology. Stone really adds to the appearance. We refer to it as the jewelry of the home — it gives homes character, warmth and depth."

Resources:
Cold Spring Granite Company
Cold Spring, Minn.
(320) 685-3621
www.coldspringgranite.com

OMAX Corp.
Kent, Wash.
(800) 838-0343
www.omax.com

Park Industries
St. Cloud, Minn.
(800) 328-2309
www.parkindustries.com

SEIS Group Inc.
Huntington Beach, Calif.
(714) 899-1399
www.robojet.net

W.F. Meyers Co. Inc.
Bedford, Ind.
(800) 457-4055
www.wfmeyers.com

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