Focusing on tube cutting lasers

Tube fabricators, producers see the light

TPJ - THE TUBE & PIPE JOURNAL® OCTOBER/NOVEMBER 2002

November 7, 2002

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State-of-the-art laser technology for cutting metal tubes includes capabilities for cutoff, beveling, and cutting an infinite variety of shapes such as holes, slots, and notches. In this article, manufacturers of laser cutting equipment discuss the state of advancements such as automated loading and unloading of parts; simplified programming; automatedinspection of finished parts; and lights-out operation.

Tube cutting laser

Object

It travels at 186,287.490 miles per second (299,792,458 meters per sec.). Its visible spectrum ranges from 400 to 700 nanometers. Its smallest unit is a packet of energy, a photon. While its chief use is illumination, it has many other commercial, industrial, and military applications.

It is light, and its use is growing in tube and pipe production and fabrication facilities throughout the world.

In most of its natural and artificial forms, light has little power. However, a groundbreaking invention in the latter half of the 1950s increased its power and concentrated it in a small area. Thus was born a modern and revolutionary concept: light amplification by stimulated emission of radiation, or laser.

The many uses of the laser reveal its versatility. When combined with fiber-optic cable, low-power lasers provide a fast, effective communication method. Because the light from a laser travels in a straight line and at a precise speed, it is useful for surveying and ranging. Its single frequency makes it suitable for advanced applications such as isotope separation and spectrography.

Of all the modern applications, though, the laser's ability to slice through metal is among the most impressive.

Capabilities of Modern Tube Cutting Machines

Relative newcomers to the metal forming and fabricating industry, laser machines are used for cutoff; beveling; and cutting slots, holes, notches, and other features of any conceivable size and shape in tube and pipe. Used most commonly for cutting the manufacturing industry's favored material, mild steel, they also are useful for cutting stainless steel, aluminum, and titanium.

Laser tube cutting machines for general fabrication work typically accept up to 20-foot lengths of tube and are equipped with load carriages that hold large quantities—up to 10,000 lbs.—of tube.

Many, if not all, can accept information in CAD format and use the information for nesting parts and developing cutting sequences and paths.

Primary Drivers

Competition is among the most significant forces driving tube and pipe fabricators toward increasing use of laser cutting machines.

"Most job shops have experienced a significant decline in the hourly rate they are able to charge, and it continues to decline every day," said Glenn Berkhahn, vice president of Mazak Nissho Iwai Corp. "In addition, the amount of work available is reduced, especially in the current economic situation. So job shops face a shrinking marketplace and shrinking sales, and the result is shrinking profits. Their challenge is one of survival.

"The challenges for manufacturers, whether they make their own products or components for other manufacturers, are different from those of job shops. Manufacturers are intent solely on driving costs down and increasing the variety of parts they can provide," he said.

Competition isn't just a local phenomenon; these days, it's worldwide.

"The field of manufacturing is under ever-increasing competition, both globally and domestically," said Jim Rutt, president of BLM-ADIGE USA Corp. "This competition takes two forms: pressure to reduce labor, both direct and indirect, and pressure to improve quality.

"Many manufacturing plants in the U.S. use a variety of machines to manufacture a single part. In a typical manufacturing process, parts are moved from machine to machine, with each machine performing one function each," Rutt explained. "In addition to the direct labor of performing each operation, these processes require significant amounts of indirect labor, too, which is incurred as parts are moved from workstation to workstation. Further indirect costs can include capital investments and maintenance—required, for example, to purchase and maintain a forklift used for moving semifinished components around the shop floor.

"To reduce overall production costs, manufacturers are moving toward machines that perform multiple functions, such as cutting to length, drilling, notching, punching, and machining, and that require little operator intervention," Rutt said. "As they adopt systems such as the ADIGE LaserTube System, manufacturers can consolidate up to six different fabrication steps into one continuous process."

With regard to quality, manufacturers strive to make items that last longer with greater reliability. One of the ways a laser machine can assist with these efforts is by being accurate. "With a typical laser machine, the axis system can position the cutting head with an accuracy of ±0.002 inch," Rutt said. "This level of accuracy, which is achievable but time-consuming and expensive with traditional fabricating equipment, enables the manufacture of parts that have better fit-up, which enables the use of robots in downstream welding operations."

For parts that are assembled manually, a tighter cutting tolerance makes them easier to assemble. Many part designs now incorporate self-locating features, such as a tab in one part that fits into a slot on a corresponding part. Such features decrease manual fit-up time and help decrease or even eliminate the need for assembly fixtures.

Ease of Programming, Ease of Use

The growth in the use of lasers has been accompanied by growth in other labor-saving devices: industrial robots. This growth has spawned, in turn, software that makes the devices easier to program and easier to use, according to Michael Sharpe of FANUC Robotics North America.

Simplifying Robotics. FANUC Robotics' software offerings for cutting tube and pipe include Autonormalizing, a program that automatically positions the laser head normal (perpendicular) to the tube's surface; ShapeGen, which generates a desired shape by incorporating centerpoint, direction, and corner radius; Custom Shape, which repeats custom geometries; and Laser Pro, an offline package that identifies features and allows the operator to use a mouse to drag the features to their appropriate positions.

The company's approach is to offer lasers with robotic devices to reduce or eliminate manual handling of parts, Sharpe said. Its latest laser-robot product is LaserMate RTC, or robotic tube cutter. It consists of a laser head indexed with a two-axis servo device, integrated with a six-axis robot. Its cut library, which stores tube sizes and features, facilitates part changeover. It also provides nesting for best use of stock, and its memory can hold instructions for manufacturing up to four unique parts from a single tube.

"Robots traditionally were programmed with a teach pendant," said Erik Nieves, senior manager of Motoman Inc.'s Technology Advancement Group. "The operator would drive the robot through each individual step, have the robot memorize the locations, and then execute the program. The operator then would tweak the programmed points and refine the logic and process parameters before an actual production run.

"To cut a round hole, an operator would have to program several points—at least one point every 90 degrees—or program a centerpoint and a diameter," Nieves explained. "Now the user can employ a program such as Motoman's FormCut software to automatically generate cut trajectories, including diameter, corner radii, and direction. Additionally, polygons can be generated by specifying the number of sides and size of the desired shape.

"Similarly, programming a bevel cut formerly was much more cumbersome. An operator would have to manually program the tube-to-tube intersection, the cut path, angle, and other process elements. Today, using a menu-driven program such as MotoSim®, the operator merely inputs the sizes of the intersecting tubes and the angle at which they meet, and the software automatically calculates all of the trajectory points. The functions of the robot are transparent to the operator," Nieves said.

Simplifying Laser Machines. Programming laser machines also is easier than in the past.

"Laser machines are simpler to operate now than they were years ago," said Michael Zakrzewski, division manager of metal processing systems for Bystronic Inc. "They used to require expert operators. Now the cutting parameters are well-defined and usually resident within the machine control. Operator adjustments now are minimized, so a semiskilled operator can run a laser machine."

However, this does not mean that software has made skilled personnel obsolete. Some situations still call for judgment.

"Programs aren't necessarily perfect. A good programmer sometimes can improve part cutting sequences and nesting to ensure that the tool is used most effectively," he said.

Simplifying Manufacturing Processes. Using a machine that accepts engineering drawings can streamline manufacturing. A part can go from concept to drawing to finished product with ease.

"A traditional manufacturing operation relies on design engineers to design parts and manufacturing engineers to figure out how to make them. The ability to download CAD files directly from a programmer's computer to the laser machine illustrates the simplicity of using laser machines," Rutt said.

Making machines easier to use for tube and pipe fabrication is no easy feat, however. Tube and pipe are characterized by a multitude of variables, including diameter, wall thickness, material, and shape. These variables pose interesting challenges for machinery manufacturers.

"Because the range of tube characteristics is so broad, it's not possible to standardize drives, chucks, and supports," said Zakrzewski. "The key is to make these items as versatile as possible. We then fill in gaps in versatility by making fixture changes as easy as possible."

However, laser cutting machines for tube and pipe, which are relatively new to the manufacturing world, advanced more quickly than their relatively older flat-part brethren did, according to Dan Robinson, laser product group manager of TRUMPF Inc.

"Many laser manufacturers developed cutting machines for flat parts first, and later used the knowledge they gained to design tube cutting machines, so tube-oriented machines developed much faster," he said.

TRUMPF used such knowledge to design and manufacture its TUBEMATIC®. It is available in two configurations—one that accommodates round tube only and the other for any tube shape. In addition to accepting CAD drawings, it can import information from 3-D modeling programs. A third programming option is the CAD software that comes with the machine.

Progress Toward Lights-out Operation

"Since the early 1990s there has been a bigger push toward automation," said Greg Walker of Modern Machine Tool Co. "We used to sell machines that were manually loaded. We never sell that type of machine anymore."

After developing automated machines, manufacturers took the next logical step: designing machines that run on shifts that aren't normally staffed, or lights-out manufacturing.

"There are significant process challenges to achieve true autonomy in lights-out operations," said Carl Traynor, senior director of marketing for Motoman. A typical autonomous operation involves a robot removing an item from a conveyor and placing it into a processing sequence. Another robot might move the part through the sequence, and finally the first robot extracts the item and puts it back onto the conveyor.

"If the operation is intended to cut a hole in a part, you need to know whether the slug fell out," Traynor said.

Until recently a person was needed to perform a visual inspection to verify that the slug had indeed fallen out. Requiring a person to perform such inspections negates any labor savings gained by upgrading from a manually operated to an automated system. A lights-out system performs inspections—it doesn't need a person to do the inspecting.

"Today inspection is handled by the robot. If its sensors detect that the slug is still present, the robot initiates the cutting sequence again. This is a huge improvement over sending the part downstream and only later finding out that a bracket cannot be fastened to a part because the hole that is supposed to exist isn't there," Traynor explained.

Sensors used for inspection can take a variety of forms, including using the laser head's own capacitive sensor, a proximity sensor, or laser triangulation.

In addition to increasing productivity, lights-out operation has a financial benefit, Walker said. "It allows a tube fabricator to amortize the cost of the unit over nights and weekends" in addition to 40 to 80 hours during the week, he said.

The lights-out concept isn't limited to nights, weekends, and holidays. Although it is called "lights-out," fabricators can use it during the day shift too.

"Many functions that used to require human intervention have become more automated—for instance, making cutting adjustments, cleaning the nozzle, and changing the focus to accommodate different materials," Zakrzewski said.

"Before autofocusing was perfected, automated systems were limited to running parts from just one material and one thickness. Now there is no particular limit to the variety of materials and thicknesses that can be processed without an operator present," he said.

This has advantages around the clock, not just during late shifts and weekends. "The operator can perform other tasks during the day shift. Fabricators typically schedule their most difficult parts on the laser machine during the day, when an operator is available to handle any problems that come up," Zakrzewski said.

In addition to advances that make lights-out manufacturing possible, many laser machine manufacturers have incorporated technology that notifies personnel if a manufacturing problem develops during an unstaffed shift. If a machine stops running, the machine pages the operator on call. Sending out an immediate notification can help to get production started again sooner rather than later. "It's better than lights-out," Walker said.

Heavy-duty Fabrication and Tube Production

Lasers aren't used just for general fabrication work. Some laser machines are designed for heavy-duty cutting applications and can accommodate structurals, components for industrial machinery, and oil country tubular goods. Mazak's models FG300 and FG300L can handle lengths of tube and pipe up to 48 ft. in length and up to 12 in. in diameter.

Fabricators aren't the only ones getting into the act. OTO Mills manufactures model TCL 1686, a 3-kW CO2 laser that functions as a flying cutoff for tube and pipe production.

"The unit is intended for cutting laser-welded stainless steel tubing on-the-fly," said Jon Gusel, vice president of sales for OTO Mills. "Because laser welding is faster than gas tungsten arc welding [GTAW], in some cases two to three times faster, laser mills need something faster than a traditional flying cutoff."

The laser head rotates around the pipe to perform the cut. It accommodates tube and pipe from 2 to 6-5/8 in. in diameter and is suitable for wall thicknesses up to 0.250 in.

Looking Ahead

Widespread industrial use of lasers to cut metal is still in its infancy. That notwithstanding, the lasers of today are a quantum leap ahead of the lasers that were first introduced a couple of decades ago. In this short time, changes in laser cutting machines—especially simplified operating and programming and automation advances—have been extraordinary.

The prospects for laser cutting machines in the tube and pipe industry seem to be secure, both in the short term—despite the slow-moving economy—and in the long term.

"Domestic tube consumption hasn't been hit as hard by the current economic downturn as some other niches of the metal forming and fabricating industry," Robinson said. Beyond the normal peaks and valleys of economic cycles, the growing use of tubing for hydroforming and increasing use of tailor welded blanks indicate the long-term growth potential of tube and pipe demand is strong.

"Because of their versatility, laser cutting machines are used in very diverse industries—essentially every industry that involves tube and pipe," said Zakrzewski.

That's not bad for a technology that hasn't yet reached its 50th birthday.



FMA Communications Inc.

Eric Lundin

Editor
FMA Communications Inc.
833 Featherstone Road
Rockford, IL 61107
Phone: 815-227-8262

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