Laser Technology
Tuesday | 15 March, 2011 | 2:50 am

Tight tolerances

By Lauren Duensing

February 2011 - Accuracy is key when cutting any type of part. According to Carl Bandhauer, product manager, for ESAB Welding & Cutting Equipment, Karben, Germany, customers who inquire about lasers are searching for the "best part accuracy they can get."

The company's Alpharex large-format laser provides accurate cuts on steel, stainless steel and aluminum heavy plate, up to six meters cutting width. "It's especially made for large plate size and thicknesses, so one of the customer benefits is the ability to cut up to 6 meters cutting width," Bandhauer notes.

For Russel Metals, Mississauga, Ontario, adding an Alpharex laser to its Edmonton, Alberta, plate processing center provides customers with another cutting option when they need clean cuts. Russel Metals is one of the largest metals distribution and processing companies in North America based on revenues and tons sold.

"We run a 34,000-square-foot processing center with plasma and oxy-fuel," says R.J. Weisner, plate processing manager for Russel Metals. The company has lasers in its other Canadian facilities and wanted to add the laser-cutting process to the Edmonton operations "to participate in a market we were not already competing in. Laser plate cutting enabled us to offer another cutting process to our customers," Weisner says.

Russel Metals Edmonton had looked at the technology before, but "we weren't interested in it when the lasers were only 2,000 kilowatt or 3,000 kilowatt," he notes. "We're a heavy plate processor, and we became seriously interested in it when laser manufacturers got in the 5,000-kilowatt range for true production cutting of up to 1-inch-thick mild steel.Ó

The company's 5-kilowatt laser can process widths up to 10 feet, with an 82-foot-long rail system that encompasses 10- to 20-foot tables. It has positioning accuracy of ±0.15 millimeters over a 6.5-foot-by-6.5-foot area. Production cutting capabilities are up to 1 inch on carbon steel, 5/8 inch on stainless steel and 1/2 inch on aluminum.

Flexible technology
According to ESAB, laser cutting does not have a physically caused angle. Thus, cuts created with the technology have smooth edges with "minor angular deviation and small kerfs, typically from 0.25 millimeters to 0.6 millimeters. This makes sharp-edged internal corners; square cutting edges, even with small holes; and intricate geometries possible."

Because of the technology's flexibility, Bandhauer says laser cutting is appropriate for all companies machining special materials--especially job shops.

Weisner says many of Russel's customers in Alberta are involved with the oil industry. "We also do some work for the agriculture business. With our large laser cutting table of 10 feet by 60 feet, we are able to process larger, wider and longer parts than many of our local competitors," he notes. The Alpharex laser's accuracy means extensive finishing is not necessary--the first piece in the batch is as precise as the last in both small and large batches. In addition, the heat-affected zone is small because of the focused beam and high feed rate. The system combines ESAB's patented beam delivery with a compact Trumpf CO2 resonator to provide high-quality cutting.

"We are known for our beam quality and cutting quality for any part. Any area of the cutting range has the same great quality," Bandhauer says. "In addition, the heat-affected zone is very important. When cutting stainless steel with a plasma system, you have a little bit darker cutting edge on the top and bottom. [The Alpharex's] cooler way of separating the material is very narrow, and users can cut very small and very large parts with precise contours.

"In most cases there is no dross, so there is no need for secondary machining after the cut," he continues. "And having this very narrow heat-affected zone means there is less heat in the material. If you have a very long part, let's say, 500 millimeters wide and 3 meters long, the material will not have any heat distortion, so the precise contours in the beginning of the cut and the end of the cut are very good."

This is possible because of the laser's optical sensors that detect the end of piercing, control cutting speed and recognize the loss of a cut. In addition, the Alpharex's laser is traveling, which gives consistently high processing quality over the entire working range.

The system's precision means that it's streamlining manufacturing operations up and down the supply chain.

"The laser is primarily eliminating a process or two for some of our customers," Weisner says. "You're cutting clean plate; it's not scaly, so they don't have to do any sandblasting. We can do holes with very tight tolerances so it eliminates a drilling process for our client. We also can do etching on the laser for identifying bend lines or fit-up templates for our customer."

Low-maintenance laser
The Alpharex has a completely encased beam guiding system that provides a safe environment for the operator. "Laser is very difficult. You cannot see it; you cannot smell it. You will only feel [the heat] if the part is coming out and then it possibly could hurt somebody," Bandhauer says. "That's the reason we put it in an enclosure. It is very safe for the operator. We fully covered the extra cutting area but not the complete machine. You can load and unload the machine when it is cutting."

The equipment has safe laser emission standards, which make it environmentally friendly. And it has systems in place to monitor the focusing optics, including automatic switch-off in case of a fault. The laser process requires no short-term consumable parts so it can handle unmanned shifts. The Alpharex has a window break detection system that detects dirt on the focusing optic and switches the beam off immediately.

"The nice thing about this particular unit, and others do it, as well, is we've done some lights-out operation, especially on the heavier plates where the machine might run for eight hours unattended and have had no problems," Weisner says.

Prior to purchasing the laser, the company was using plasma and oxy-fuel torches, so it was a fairly easy transition. Operators picked up the controller system quickly, and then, once they understood the process, the company was up and running, meeting customers' needs. With several different options for customers, Weisner says Russel can achieve its goal of "offering the best cut quality out there with the equipment we have. That's a determining factor in which process we use." MM

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