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Doing it all with lasers.

even the kitchen sink

Many people still associate lasers with futuristic deep-space travel, starships, and high-tech weaponry. Others think of lasers as a highly esoteric technology of last resort, to be used only when the work to be accomplished requires a solution so precise and so powerful that it cannot be achieved by any other means. Yet, last year, more than 3300 lasers were installed in what otherwise might be regarded as conventional machine-tool applications such as cutting, welding, drilling, and marking. And while lasers have enjoyed much success in high-tech industries such as aerospace, many are being used to produce parts as commonplace as electronics chassis, croissant cutters, and "egg crate" fixtures.

One company that exemplifies the versatility of laser use in industry today is Southwest Fabricators, San Diego, CA. Southwest and two sister operations are fully utilizing the potential of CNC laser cutting systems with sheet metal, plastics, composites, and wood to fabricate parts for land, sea, and air. It's fair to say they make everything including the kitchen sink, which they do for major restaurant chains.

This "can do" philosophy helped Southwest recognize the laser's potential early on to become a West Coast laser cutting pioneer. Since buying its first Cincinnati laser system in 1987, Southwest Fabricators has perfected laser cutting to a high art--in terms of both productivity and decorative work capabilities.

Productivity issues influenced the selection of its first laser, a machine that offered a moving-beam design with dual cutting tables, CNC control, and 1200 W DC resonator. "We recognized that a two-position, dual-pallet system could make a huge difference in productivity," says Southwest president Daren Weckerly. "We also wanted a large and powerful enough machine to cover the whole scope of fabrication, from light gage metals to 1/2" thick plate."

Growth through diversity

Southwest Fabricators belongs to a group of family-owned companies that traces its roots to 1905. That was when Mr Weckerly's great-grandfather founded the San Diego Sheet Metal Works, which still serves the construction industry providing architectural sheet metal components. In the late sixties, the family created a new company to serve several specialty markets: Pacific Marine Sheet Metal Corp and its Southwest Fabricators division concentrate on commercial restaurant kitchen fixtures and precision sheet metal for high-tech industries. Both also serve the fabrication needs of California-based cruise liners, navy vessels, and commercial boats and ships. San Diego Sheet Metal Works and Pacific Marine share a centralized fabrication shop and administrative offices on a two-acre site in downtown San Diego.

Laser cutting provided the versatility to meet the diverse material and fabrication requirements of these different markets, says Mr Weckerly. By eliminating shearing, deburring, and punch-tool setup, laser cutting lets Southwest Fabricators process material faster and more accurately than hard-tooling methods. "Prototypes, first articles, and limited production run jobs can be turned around very quickly," he adds.

Depending on the work volume, employee numbers can swell from 75 to over 100. "Our long success can be directly attributed to the caliber of our personnel and the technology we invest in," says Mr Weckerly. The shop's advanced facilities include a CAD/CAM programming center, CNC plasma cutting, certified welding, and an array of machinery including Cincinnati press brakes and CNC forming centers. A sophisticated vision inspection system helps the quality department assure products to customer specifications.

Diverse material cut

The two Cincinnati lasers cut aluminum and copper alloys to 3/16" thick, steel plate to 1/2", and stainless steel up to 1/4". They also process copper, chrome-moly, nickel alloys, titanium, Inconel, plastics, and composites, as well as wooden blanks up to 2" thick for decorative trim and cabinet work.

"When we bought our first laser in 1987, laser cutting was in its infancy," recalls Mr Weckerly. "It behooved us to learn the laser's cutting parameters as quickly as possible because of the diversity of our work and the investment made--so the sooner the machine began to pay for itself, the better. We experimented heavily, cutting materials of all types and thicknesses. Today, I think we are experts at understanding how different materials react to laser cutting."

Actual cutting is done with a contact laser head that rides the material as it cuts. To prevent marking of mirrored surfaces or dimpling of thin plastics and sheet metal under 0.030" thick, the head is positioned to ride slightly above the material.

Oxygen gas assists in cutting aluminum and cold and hot rolled steels. While oxygen enables high-feedrate cutting of stainless steel, nitrogen leaves a clean, oxide-free edge for cosmetics and easy welding, says Erik Lowry, laser technician and programmer at Southwest. Nitrogen is also essential for cutting flammable materials such as plastic laminates and acrylics. "The high-pressure assist gas capabilities of 250 psi at the nozzle give us an advantage over other laser job shops because it helps flush out any dross from the cutting area," he says.

Edge quality

Mr Lowry describes overall edge quality as "excellent." Steel and aluminum are processed without slag or dross left by the heat-affected zone. Finishing is necessary only where the edges are literally too sharp for the customer. With stainless steel, careful attention to feedrate, power, and assist gas achieves dross-free part edges.

Clean edges have reduced finishing and improved welding operations significantly. On one high-volume job, 3/16" stainless steel ductwork cut on a plasma cutting machine left burrs and dross. To remove them, the 3 ft x 4 ft parts required extensive grinding. "With the laser, edge quality is so good we eliminated deburring on these parts prior to welding," say Lowry. "We also reduced our welding and assembly time significantly, because the parts fit together perfectly."

Clean edges speed welding by reducing the amount of welding filler required to join the parts. During large-radius forming of some restaurant waiter stations, the laser beam's narrow kerf width "took out really small slices that helped us make better bend reliefs," says Mr Lowry. "Tight seams reduce welding and polishing and produce better looking products in a shorter amount of time."

Tight fitting seams, especially important on kitchen tabletops and fixtures where food could otherwise get trapped, ensure that Southwest and Pacific Marine meet standards set by the National Sanitation Foundation, NAVSEA, and the US Dept of Health. Pacific Marine, for instance, recently used lasers extensively to fabricate custom galley and restaurant equipment for the Royal Caribbean's Viking Serenade cruise ship.

Close tolerance cutting

With thinner materials, the Cincinnati lasers also provide the company with capabilities unmatched by hard tooling processes, says Mr Lowry.

Fabrication of 78" long channel from 0.020" thick aluminum for a phased array antenna proved especially telling. "The print had a parallel callout of 0.005"," recalls Mr Lowry, "which means the part's two sides had to be parallel to each other within 0.005" over the entire length. The laser easily held parallelism to within 0.002". If we had sheared it, we could never have held the tolerance."

Southwest's quality control program conforms with the requirements of MIL-I 45208A and MIL-STD-45662A. Aerospace and defense work now accounts for 30% of sales. The lasers have cut satellite skins from 0.030" thick aluminum, stainless steel gaskets for missile launchers, and manifold exhaust ducting for tanks and aircraft engines.

Decorative cutting

Of all the varied laser work, Lowry is especially proud of the company's ability to process decorative inlays. Satin finished bronze and stainless steel inlaid into mirror stainless is used to decorate elevator doors and cabs. During refitting of the cruise liner Viking Serenade, the lasers cut 0.050" thick Formica patterns for inlaying into 14-gage stainless steel cabinetry.

"You can't beat the laser to do inlays--the artistic effects are spectacular," says Mr Lowry. "By adjusting the width of the laser beam, we can process the material to an exact fit."

Programming for speed

To speed part programming, Lowry uses software that creates or inputs customers' 2D and 3D CAD files, generates program tool paths, and automatically nests multiple parts in a best-fit pattern on the sheet of material. Programs are then downloaded to the CNC lasers or to NC plasma cutters and punch presses.

The shop uses an optical scanner to reverse-engineer flat templates to |+ or -~0.010" accuracy, saving countless hours of program generation on complex parts. By scanning an airplane's 40" x 42" stainless steel fire wall, featuring dozens of eccentric holes, Southwest was able to download program data to the laser in a fraction of the time it would otherwise have taken.

The scanner also doubles as a measurement tool, inspecting first-article parts off the laser and other machines in a matter of minutes.

Laser cutting features

For optimum cutting control and improved part quality, Lowry uses the laser's Dynamic Power Control (DPC) and Superpulse features.

Developed by Cincinnati, DPC adjusts laser power proportionally to feedrate. This eliminates "looping" of corners and circles, a tendency of other lasers to cut beyond the designated path. The DPC power levels are added automatically, simplifying parts programming. Says Mr Lowry: "I mostly use DPC when we're cutting steel with oxygen and the laser beam is approaching an obtuse angle. If the laser spends too much time negotiating the turn, it might burn away more material than we want to cut. DPC works great by automatically changing the power to prevent the material from overheating as the feedrate slows into the corner."

Superpulse mode is used to pierce sheet metal in short, fast bursts at four-to-six times rated wattage. Used primarily at the start of a cut, Superpulse pecks holes quickly and cleanly. The laser will automatically switch back to continuous-wave mode to maximize cutting speed for the remainder of the cut.

On longer linear cuts, Mr Lowry says the lasers work at feedrates of 200 ipm to 300 ipm on 14- and 16-gage material, though contouring reduces average speed to around 100 ipm to 120 ipm. Slightly slower feedrates are used with copper alloys and mirror stainless, whose surfaces can reflect the beam. For intricate, precise patterning of thick material, such as flanges from 1/2" steel plate, feedrates drop to 20 ipm to 30 ipm.

Choosing a laser

Southwest's manufacturing team chose both lasers with optional twin-pallet design for maximum machine uptime. The operator can unload/reload a metal sheet up to 5 ft x 10 ft on one pallet while the laser is cutting parts on the other. The pallets slide in and out of the cutting area like drawers, switching places automatically when the laser has finished cutting. "In 1987, we recognized that dual-precision cutting pallets could make a huge difference in productivity," says Mr Weckerly. "On long production runs, we estimate it enables machine uptime as high as 95%, compared to 75% utilization for single pallet units."

The company purchased a second laser just a few years later, a Cincinnati CL-5 Model 350 with 1350 W power. It, too, features dual pallets for maximum flexibility--a single 4 ft x 8 ft cutting table twinned with a 4 ft x 4 ft table.

At Southwest Fabricators, laser cutting has boosted productivity on many jobs by eliminating shearing, deburring, and punch-tool setup. Superior part quality and accuracy has improved welding and forming operations. The lasers complement the company's other manufacturing capabilities to build complete products for a wide variety of industries.

"Laser cutting has increased our capabilities far beyond what we had hoped for back in 1987," says Mr Weckerly. "It broadened the scope of services we could offer our current customers and opened the door to many new opportunities as well. For a job shop, new opportunities create success, and success in business is what it's all about."

Marking and engraving

Though lasers are used extensively for cutting, welding, and drilling, one of the most interesting and widespread applications of laser processing involves marking or engraving. With several thousand laser marking and engraving systems now in use, worldwide acceptance of this industrial technology has been based upon the laser's ability to offer marking solutions and cost savings unavailable through traditional means.

Laser marking and engraving requires no ink, paper, or acid. Instead, a laser, focused on a material's surface, creates a permanent impression of less than 0.001" (marking), or more than 0.001" (engraving). Depending on the material's thermal conductivity, color, and surface finish, low- to medium-powered C|O.sub.2~ or Nd:YAG may be used.

Based upon the physical properties of the material to be lased, contrast can be achieved with any of three different techniques: annealing, melting, or vaporization. The particular technique selected determines the maximum amount of laser energy (working temperature) that must be achieved at the material's surface to achieve the desired effect.

The ability to mark directly on the material without the use of ink, paper, or acid allows manufacturers to quickly create alphanumerics, logos, barcodes, or technical flow diagrams. Intangibles, such as unique product image, or the ability to place laser marking at any stage of the manufacturing process, provide manufacturers with extremely flexible, cost-efficient, marking solutions.

Deep-hole drilling

Aero-Fab, an Indianapolis-based manufacturer of aerospace components, has increased production substantially with its recent acquisition of a Laserdyne 550 BeamDirector laser machining system.

One Aero-Fab part (a 17" long x 14" high x 1" thick cooling frame used in General Electric turbine engines) presented manufacturing difficulties because of the material (Nimonic) hardness and thickness. The part required 194 holes 0.060" (1.5 mm) in diameter to be drilled at 12 deg angles, each with a tolerance of |+ or -~0.003" (|+ or -~0.075 mm).

Originally, Aero-Fab produced the parts by hand drilling the holes, a costly and time-consuming process that frequently caused expensive tool breakage and substantial part rework. Today, Aero-Fab's process involves laser piercing into the part and trepanning or contour cutting the holes and forcing the minute slug through the exit hole. The process results in much straighter and cleaner holes than does percussion drilling.

Daryl Grubb, Laser Dept manager at Aero-Fab, reports that the laser is operated at 52 joules per pulse with a 250 mm focal length lens, which allows easy and fast deep-hole penetration. Repeatability has been a consistent |+ or -~0.003" (|+ or -~0.075 mm), and part production increases have been recorded at up to 200%.
COPYRIGHT 1993 Nelson Publishing
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Author:Stovicek, Donald R.
Publication:Tooling & Production
Date:Feb 1, 1993
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