Laser Technology
Friday | 02 March, 2012 | 1:31 pm

Clean beam pathway

By Nick Wright

Sealed optics, a moveable resonator produce powerful, lights-out laser cutting

February 2012 - After weathering the financial downturn of 2009, SMF Inc., Minonk, Ill., rebounded in 2010 followed by a strong 2011, according to owner Paul Halvorsen. “This year, forecasts are great,” he says. The full-service metal fabrication shop is primarily a Tier 1 supplier for OEMs, which make up 95 percent of its business. Many of its products include large engine components and weldments that require weld-ready edges for large customers such as Caterpillar. 

Koike Button ADTo accurately cut steel in plate, sheet and square tube form with finished, weldable cut edges and a minimal heat-affected zone, SMF runs a pair of identical 4-kilowatt Lasertex LT-3540Z CO2 laser cutters manufactured by Koike Aronson Inc./Ransome, Arcade, N.Y. Before SMF purchased its first Lasertex through its distributor about five years ago, the company was outsourcing its laser cutting. 

“This saved us about 30 percent in costs not having to outsource these parts to an outside vendor,” Halvorsen says. 

Established in 1972, SMF also makes fabricated oil pans, bases and other parts that join generators to engines as well as products for the mining and construction industries.

At first, SMF was running its Lasertex lights-out, 24 hours a day, seven days a week. “So we bought a second identical machine and that helped both as a backup and additional capacity,” Halvorsen says, noting SMF purchased its second laser cutter two years ago. “The nice thing about the lasers is that they cut out so precisely. Things you’d normally have to put on a CNC machine or get stamped, you can cut with a laser and save a lot of money.” 

SMF typically cuts steel sheet in 12-foot to 16-foot sections, however, the largest is 10 feet by 44 feet, according to Steve White, plant manager. “One laser runs almost nothing but rectangular tube” in 8-foot by 12-foot up to 14-foot by 14-foot sections with thicknesses of 1⁄2 inch or 3⁄8 inch. Each machine has two tables to accommodate cutting longer parts. 

Usually there is no finishing required for most pieces, such as square tubes, which will go to the weldment or to a second operation such as the brake press or sometimes machining, Halvorsen says.

With a cutting tolerance of ± 0.005 inch and high repeatability, the Lasertex delivers a cut edge that eliminates cleaning any dross or other secondary finishing, according Koike’s website. Its high-speed piercing reduces cycle time for cutting holes in steel plate.

SMF’s Lasertex models have a cutting width of 111⁄2 feet with a rail length of 50 feet. Koike also offers customizable sizes. “What’s neat about it is it’ll cut between 40 feet and 50 feet long, 10 feet wide,” Halvorsen says. The machines are massive, with platforms for an operator to ride on. However, their large footprint is no problem for the company’s 140,000-square-foot facility.

SMF uses SigmaNest CAD/CAM software to program parts on a PC-based Fanuc controller. After parameters are set, “we load everything with [an] overhead crane and manually,” White says. Since adding a second machine to keep up with the demanding workload resulting from steadily increasing business, “both machines run 24 hours per day five to six days per week,” White adds. “Both lasers run for approximately eight hours unmanned.”

Running the Lasertexes unmanned is key, especially when cutting thicker plate that takes more time.

“That means some customers will run their thickest materials at night because the machine is running so slow,” says Tim Joslin, product manager at Koike. “What they can do is load multiple plates of multiple thicknesses. As long as they are the same material, you can start under one program and cut all of those plates, and when you get there in the morning, you just pull your parts, clean your skeleton and start cutting again.”

Another one of SMF’s requirements was the ability to rotate 4,000-pound and 5,000-pound rectangular tube for cutting holes, says Brian Brown, president at SMF. Koike added headstock tailstock positioners that rotate tube in 90-degree increments, a feature that, at the time, no other company offered. “That’s one reason we bought the laser the first time. We knew beforehand what this laser could do.”

Sigma Box 
At the heart of the Lasertex’s design is Koike’s Sigma Box, a proprietary, self-contained laser-beam stabilizing system that maintains constant beam-path length. “One operator can quickly adjust the focal length up and down for different material thicknesses,” says Brown. “We’ve heard nightmares about transferring mirrors on machines, but we’ve had no problems with ours.”

However, the Sigma Box provides advantages on multiple levels beyond focal length adjustments.

The Sigma Box is integrated directly with the CO2 resonator, and the whole assembly sits on top of the cross carriage, says Joslin. When the cross carriage moves across the plate so does the resonator. This eliminates a bellows, the accordion-like assembly that contains moving optics required for maintaining beam length in machines with stationary resonators. 

With the Sigma Box, “what we do is move the power source and the mirrors and everything all at the same time,” Joslin says. “So the beam length never changes.” 

He notes that Koike’s Sigma Box also keeps SMF’s operators from having to change the focus lens when cutting different plate thicknesses. “With the Lasertex, as long as you’re running the same material, you run one set of consumables and one focus lens through the whole range of material from 1⁄16 inch to 3⁄4 inch.”

Halvorsen says the integration of the lenses and power source ultimately makes SMF’s cutting more efficient. “Our plant manager said one thing that’s nice about Koike’s setup—and he’s had experience from previous companies—is that everything rides on the column,” Halvorsen says, referring to the resonator. “You have your Sigma Box, and all the lenses and everything are right there as opposed to being on a stand-alone box so they have less travel distance. So he said that contributed to improved maintenance and reduced downtime.”

Do without dust
Because the Lasertex’s optics are sealed within the Sigma Box, maintenance for cleaning the mirrors and cavity through which the beam passes is simplified. The stainless steel box is air-purged, keeping the optics as clean as possible during machine use.

Without a bellows, which essentially concentrates air pressure, there is less chance of dust from the shop’s environment contaminating and adhering to the mirrors, Joslin says. That can compromise beam quality.

“As soon as that happens, you’re going to start losing laser power. Your beam quality goes down because of your mirror being dirty,” he says. The other problem with dust is compromised beam quality can concentrate heat on the contaminated mirror, preventing it from deflecting properly, potentially damaging the mirror. “So ours is all done inside.”

With SMF’s around-the-clock cutting, the clean Sigma Box reduces concerns about beam quality as well as maintenance time. The Lasertex also is equipped with a preventative maintenance program. SMF keeps track of the number of hours on the machine, after which Koike will come onsite.

“We can send one guy to do maintenance in about a four-hour period to replace the particular optics or clean them,” Joslin adds. Koike’s representatives are Fanuc-certified to work on the internal optics, so separate workers don’t need to come in.

Koike’s customer service, aside from the maintenance, has been a cornerstone of the relationship between the two companies. When SMF purchased its laser cutter, Koike dispatched representatives for training over the course of a week, according to Halvorsen.

“The service department is great,” Brown adds. “ I can call them almost 24/7 and they’ll call me right back. We’ve been [really] happy with them.” MM

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