Today's advanced 3D laser cutting machines are tomorrow's metal-processing standard.

Prima's Domino, a 2D/3D high-speed laser system, efficiently cuts pre-formed parts.

New applications for 3D lasers include bevel cutting mild steel.

Modern laser systems can tackle even deep-drawn parts.

In standard 2D CO2 laser cutting, the laser beam runs perpendicular to a workpiece surface, and most of the process gas gets deflected.

Even more process gas gets deflected with an inclined beam.

3D profiling cuts a mild steel part from a 0.5-in.-thick U-profile.

Several bevel cuts were necessary for a part made from 0.5-in.-thick mild steel.

Shops have grown accustomed to using 2D laser cutting machines for flat sheetmetal processing. But, until recently, fabrication jobshops have shied away from 3D laser cutting, because systems were complicated, expensive, and difficult to program. Most of the inroads 5/6 axis lasers have made in recent years were in prototyping or low-volume production for the automotive industry. However, this will change as the process becomes more widespread in the factory of the future.

2D high-speed laser cutting already fills much of the demand for higher productivity in the sheetmetal processing industry. For one, high-acceleration motion control and elevated laser power have boosted laser cutting speeds to 60 ft/min and more. Also, using nitrogen assist gas — rather than oxygen — lets companies overcome speed-limiting oxidization.

Today's CNC machines, which feature 2D and 3D capabilities, give shops additional avenues to profitable new applications. These surprisingly affordable CNC systems are highly dynamic and stiff, and they offer high resolution for the required timing and positioning. Adding an optional rotary axis for profiling gives shops a low-cost, all-in-one machine that pumps out a variety of jobs.

Today, smart shops know they must diversify to survive and prosper into the future. For example, shops having only multiple flat-sheet cutters face fierce competition — it's easy to cut light gage sheetmetal, so almost any laser sheet cutter will do. The better strategy is to become a one-stop shopping opportunity by offering a variety of technologies.

Exploiting a niche market
Because 3D laser cutting fills a niche market (less than 20% of the entire laser cutting market), it demands a premium price be paid. Fortunately, competition is still limited and those entering the field first will benefit from a faster return on investment.

There are several profitable applications for the new machines:

• Laser cutting of small 3D parts.
• Efficient 3D trimming of small deep-drawn parts.
• Processing holes and cutouts in hydroformed parts.
• Bevel cutting on 2D sheetmetal and 3D parts.

The addition of an optional rotary axis further expands processing possibilities:

• Cutting of tubes and profiles.
• Bevel cuts in tubes for better fits.

Tilting the beam
In standard 2D CO2 laser cutting, the laser beam is usually oriented perpendicular to a workpiece surface. The beam melts the metal, while a jet of assist gas blows the molten material out of the cut kerf.

With such an orientation, the gas jet is substantially larger than the focused laser-beam diameter. This means only a small part of the jet passes through the narrow cut kerf and most of the gas is deflected. This problem is compounded when the beam is tilted, for instance, in bevel cutting on a flat-cutting system fitted with a 3D head. In fact, the greater the tilt, the less effective the system is in blowing out the molten metal from the cut kerf.

Another difficulty is that tilting the beam may mean a particular machine can't to handle a cut. That's because the cut depth is larger than the sheet thickness as soon as the angle of incidence deviates from 0°. Just tilting the beam 45° can increase the effective part thickness from ¹ /4 to nearly³ /8 in. These difficulties are why bevel cutting with a tilted laser beam is not merely a straightforward add-on. Adjusted parameters are required — for example, the X and Y axis will

have to move in a nontypical trajectory because of the offset between the Z axis and the focal point. (This offset is a function of the bevel angle, and the trajectory calculation is a tool-correction offset evaluation.) In some extreme cases, the cut kerf quality might be compromised as well.

However, new laser cutters and their software, which have been optimized for productivity and performance, now let systems effectively run applications tilting the beam. In fact, laser bevel cutting, for instance, eliminates additional processing on the workpiece.

For example, welding preparation is a time-consuming and difficult process when parts are conventionally laser cut. But with a tilt cut, the laser delivers the bevel is during the initial profiling process, eliminating an entire process step (including planning, working space, personnel, tools, logistics, stocking, and rejected parts). This slashes process time and operation costs.

Another example for the tilt beam is the high-speed trimming of hotstamped parts in the automotive industry. Because these parts are made from hardened steel, conventional stamping tools would wear out in no time.

The tilt beam also lets shops produce more complex parts such as slanted teeth for helical gears or simple beveled holes for countersunk screws.

Shops should be aware that reflected laser light can present a safety hazard. Therefore, they should perform the piercing process with a perpendicular incidence (angle = 0°). As soon as piercing is complete, shops can then tilt the cutting head to the required bevel angle.

Optional process enhancements
The old teach-in programming method is costly, because the machine is not productive during the programming period. However, having this ability might be helpful for special applications, where CAD files are not available. In most cases, it's

best to have programming software allowing for off-line programming directly from the CAD files. In addition, optimal exchange tables, automatic loading and unloading systems, and pallet towers can optimize automation and productivity.

About the authors Thomas Burdel is vice president sales and marketing, and Pieter Schwarzenbach is vice president laser technology, at Prima Laser Tools, Chicopee, Mass. For more information, call 413) 598-5200, or visit prima-na.com