FLAME CUTTING MOTHER LODE

Bucyrus International is one of the world's leading manufacturers of large-scale excavation equipment used in surface mining. Bucyrus machines are used throughout the world by customers mining copper, coal, oil sands, iron ore and other minerals. An important part of the company's business also consists of aftermarket sales in support of its large installed base of machines (approximately $12.5 billion based on estimated current replacement value) with service lives from 15 to 40 years.

Founded in 1880 in Bucyrus, OH, the company is now headquartered in South Milwaukee, WI, with subsidiary and support offices around the world. Known as a innovator in the mining industry, Bucyrus has produced some of the largest surface mining machines ever manufactured and introduced the first commercially accepted electric rotary blasthole drill in 1952, a product that changed the face of mining forever.

With demand for coal mining equipment on the rise, particularly in China, Bucyrus recently found itself facing a serious capacity issue in its main manufacturing plant in South Milwaukee. In order to keep up with customer demand, the company launched a three-phase $130 million expansion that included remodeling and re-equipping a new fabrication shop.

A key area of improvement focused on the company's flame cutting capabilities. The cutting productivity sets the stage for increased productivity down the line. The production of massive mining machines requires the ability to cut and bevel very large parts. Bucyrus cuts plate from half-inch to 12.5 in thick. Since their products are so highly customized for the capacity of the mines they serve, Bucyrus also rarely cuts more than a few parts that are alike and has no high production runs. They wanted a cutting machine that was operator friendly and easy to program that could also increase their overall productivity.

After first purchasing machines from another company that did not work out as well as they hoped, they recently installed new machines from ESAB Cutting Systems. They had an older ESAB machine that they were still using after 17 years, according to manufacturing engineer and project manager John Fletcher. Since their experience with this equipment and service had been very good, they decided to see what new technology ESAB had to offer in oxy-fuel cutting.

They purchased two Avenger X cutting gantries, each equipped with three Flame Control torches, and one Avenger 2 gantry equipped with three Flame Control torches and two Programmable Contour Edge Prep stations.

The fully automated Flame Control system uses flame monitoring technology and electronic proportional valve gas controls to make oxy-fuel cutting easy to set up and use. The Electronic Proportional Valve Gas Control System automatically adjusts the fuel gas low preheat pressure, oxygen low preheat pressure, fuel gas high preheat pressure, oxygen high preheat pressure, cutting oxygen start pressure, cutting oxygen ramp time and cutting oxygen maximum pressure. This makes oxy-fuel gas setup as simple as selecting the material thickness.

ESAB's Vision 55 CNC control then uses ESAB's Programmable Cutting Parameters to fully automate process set up. The fully integrated process control system automatically sets the cutting speed, kerf offset, preheat time, pierce delay, creep speed, high preheat delay and travel delay. An optional automatic height control system automates the preheat height, pierce height and cutting height.

"The Flame Control senses the heat of the flame and sets the temperature consistently," says Fletcher. "We can cut with all three torches at the same settings with no need for the operators to intervene. This saves us approximately 20 percent in production time." The Flame Control torches also use high speed tips so the machine can cut faster, while the sensing technology minimizes problems with flame outs, all contributing to an overall reduction in production time.

"ESAB also designed a breakaway torch holder on the Flame Control torches," Fletcher explains. "If the torch bumps anything, the machine is shut off. It then resets and is ready to work again." This has significantly reduced maintenance at Bucyrus. With their previous machine, the mounting brackets were frequently damaged in "crashes" and needed to be reset and tested or repaired. These repairs generally resulted in two weeks to a month of downtime. "We were averaging a month of downtime every other month," Fletcher says.

The Avenger X gantry is designed with precision linear ways and a high-stiffness beam structure that make the machine ideal for precision cutting, marking and beveling. The fabricated beam is made from two steel tubes with welded stiffener plates to form an extremely stiff welded structure. Avenger X offers positioning accuracy of ±0.015 in over a 6 ft x 6 ft area with a repeatability of ±0.005 in. "Our operators are very pleased with these new machines," Fletcher says. "They learned to use the functions very quickly and were able to be very productive almost right from the start."

Bucyrus also uses a great deal of bevel cutting to prep pieces for welding. "We've been doing beveling for 30 years," Fletcher says. "Probably half our parts use some kind of beveling. We needed an alternative that was more consistent and reliable than our older machines." The programmable beveling stations consist of three oxy-fuel torches that rotate automatically to cut bevels on carbon steel up to 4 in thick. Various geometries can be cut, including X, V, Y and K bevels. A tactile automatic height control maintains the extremely accurate torch height critical to maintain the desired bevel geometry and part accuracy.

Bucyrus bevels parts up to 3 in thick in various grades of carbon steel. They purchased the Avenger 2 gantry with a 40 ft long x 25 ft wide cutting capacity so they can turn the plate sideways and cut two parts at the same time. Most of these cut parts go into sections or subassemblies that will be shipped to the mine for final assembly. Some parts, such as one particular gear for example, can be 12 ft in diameter. Their largest cut part weighed 20 tons. "The bigger the parts, the more efficient the contour bevel," Fletcher says. "Our big parts are where the contour bevel stations really save time."

Another function that Fletcher appreciates on the contour bevel stations is the height control. The dual sensor system freezes the height if it senses that the torch has gone off the plate. "Most systems drop lower if the sensor goes off the plate," Fletcher says. This system maintains the correct torch standoff above the plate surface, which is critically important for accurate bevel cutting.

It takes approximately one year to put an electric mining shovel, for example, into service (from order to complete installation), with approximately six months of that time dedicated to actual production. With such long lead times, one might assume that fast production would not be of critical importance but the added demand for product has resulted in the need to produce more work each year. "We used to do eight per year," Fletcher notes. "Today we do about 16 per year, and Bucyrus has set a goal to produce 24 shovels per year."

To reach these types of production goals, a company has to look for the best technology to do the job. In Bucyrus's case, these advances in automated cutting and beveling technology provide the speed, simplicity and reliability to help this company reach its aggressive goals.

Bucyrus International, Inc., 1100 Milwaukee Avenue, South Milwaukee, WI 53172, 414-768-4000, Fax: 414-768-4474, www.bucyrus.com.

ESAB Cutting Systems, 411 South Ebenezer Road, Florence, SC 29501-0545, 843-664-4394, Fax: 843-664-4403, www.esabna.com.