Laser Technology

More power

By Russ Olexa

To gain greater productivity for cutting sheet metal, laser manufacturers are always developing and introducing new resonators. Some reduce cutting time or cut thicker materials while also decreasing or eliminating maintenance, which adds up to lower part cycles and more parts produced.

One constant heard from users is the need for more powerful resonators to cut thicker materials, such as 1.25-in. steel, and to cut thinner materials faster. And the manufacturers have heard their pleas. New resonators offer the high wattage needed to cut thicker materials or have been redesigned to cut thicker materials but with lower wattage.

Therefore, this article is about those new resonators from laser system manufacturing companies that build their own resonators (not just resonator producers) and have introduced new resonators within the last year to year and a half. There are many companies that build laser systems, but only a few of them build their own resonator. Others, such as Finn-Power and Amada for example, buy the resonator from companies that specialize in producing them, like Rofin-Sinar or Fanuc.

The heart of any laser system is the resonator that initiates the beam. Two types are commonly used. One is an Nd:YAG (Nidium Yitrium Aluminum Garnet), where the YAG is a solid crystal, and the other is a gas laser that uses CO2 gas instead of a solid crystal. The CO2 laser is commonly used for metal cutting while the Nd:YAG is used for welding, some cutting and especially for marking, scribing and specialty drilling.

While a solid crystal can be used to create a laser beam for cutting, using CO2 gas creates a wavelength that has the thermal properties needed for metal cutting. Wavelengths produced by other gases or solid-state lasers don’t have the same energy potential.

Thicker material cutting
Demand for thicker material cutting led Prima Laser Systems, Chicopee, Mass., to introduce its CV Series Fast Axial Flow (turbine-style) CO2 laser resonator. The 5-kW system can cut up to 1-in. steel, thick aluminum plate and stainless steel from 0.6 in. to 0.8 in. with faster speeds.

Pieter Schwarzenbach, vice president of laser technology at Prima, says that the CV Series produces high power with exceptional beam quality for difficult material processing. "Its new design stresses simplicity, low operating costs and high reliability, reducing maintenance," he says.

  Schwarzenbach says that if a company has a two-year-old laser that cuts a significant amount of thick steel, stainless or aluminum, the higher wattage and cutting speeds of the CV Series should be considered as a replacement. With it, he says a company can cut more parts with the same amount of assist gas used with its present resonator, or decrease the amount of assist gas to save costs.

He says that the beam has a high brightness for excellent power density and DC excitation for superior electrical efficiency. It uses a magnetic bearing turbine that eliminates bearing changes, a resonator structure for fast warm-up and temporal and spatial stability and a solid-state power supply for reliability and low-maintenance. It also features a user-friendly PC-based controller with advanced remote diagnostics and a single cabinet design for access to maintenance points.

The resonator features machined aluminum end plates for increased optical stability and a resonator design that offers symmetry and near-zero growth during operation for a more stable beam. Advanced composite elements are used along with a kinematic mounting for increased beam quality and pointing stability.

The oil-less, solid-state power supply features high-voltage components protected from environmental contamination and a fast rise time to cut complex contours without overheating.

New solid-state power
Frank Arteaga, laser product manager at Bystronic Inc., Hauppauge, N.Y., says that the company’s 6-kW RF resonator was the result of an evolutionary process to meet the needs of those wanting more power to cut thicker materials with less maintenance.

"Bystronic’s Bylaser 6-kW RF laser resonator offers a solid-state power supply designed by Bystronic, which replaces the older vacuum-tube type for older DC and RF Bystronic resonators," he says. "The technology offers zero maintenance and improved electrical efficiency. Cost savings are realized by eliminating the replacement of high-voltage or RF-tube components that have a limited life span. Bystronic’s RF technology uses low-frequency RF, (less than 1 Mhz), lowering component cost.

"Another Bylaser enhancement is the CNC-control monitoring of the resonator optics’ temperature and automatic power calibration features," he says. "Temperature sensors are located in the output window and the end mirror, which monitor each component’s temperature. If one of the optics reaches a high temperature outside of its typical operating range, the system will give a warning and shut down the resonator power depending on the severity of the temperature increase. This feature provides additional operating security for unattended shift operations and for cutting reflective materials such as aluminum."

Bystronic’s automatic power calibration recalibrates the resonator in minutes if the power drops below 10 percent of the requested wattage, enabling users to continue to operate their machines at full production speeds even though an optic might be on its last hours of operation. Arteaga says that Bystronic’s 6-kW resonator can cut up to 1-in. steel or stainless steel and up to 5/8-in. aluminum.

Resonator cuts 1.25-in. steel
Mitsubishi Laser, Wood Dale, Ill., introduced its 40 CF-R 4-kW CO2 resonator technology, built from Mitsubishi’s CFX-series resonators for the company’s LVPlusII laser system. This resonator, and the company’s next generation 60 CF-R 6-kW CO2 resonator, are designed to meet customer expectations for advanced cutting, says Jeff Hahn, laser product manager.

"We came up with enhancements in our resonator as to where components are placed," he says. "Our resonator includes the power supply, the damper and vacuum pump all in one unit for faster and easier maintenance. Both resonators reduce rise time/fall time, giving the laser beam a truer square-wave form. This provides a more consistent beam power and low power distribution while cutting and delivers a more consistent edge quality with more power stability even when used at lower wattage. The uniform low-current discharge provides low power stability for improved micro machining and etching."

Mitsubishi resonators have a cross-flow design that eliminates the turbine and glass tubes used to excite the gas for low-cost ownership, says Hahn. "We’ve never replaced a resonator in the last 21 years."

The resonator’s Brilliantcut technology produces a cutting surface roughness equivalent to the typical machined finish. Brilliantcut provides optimal processing conditions and reduced taper and discoloring on the heat-affected zone, says Hahn.

A new Jet Pierce technology decreases part time by allowing material to be pierced faster and more aggressively during small-hole processing. Mitsubishi’s Diamond-Path technology maintains consistent beam quality by using a constant beam-length system. It provides cutting stability up to 1,150 ipm. Mels Eye, the optional intelligent process monitoring system has autofocusing and other detection features to ensure cut quality. Burn detection tracks each cut, and when it’s no longer sustained, the laser system automatically restarts. Pierce detection increases productivity by eliminating the buffer in conventional oxygen piercing.

Mitsubishi’s 40 CF-R can cut up to 1-in. mild steel. The 60 CF-R cuts up to 1.25-in. mild steel, 1-in. to 2-in. stainless steel and 3/4-in. aluminum.

Faster cutting
Trumpf’s RF excited TruCoax 3200 (3.2-kW) CO2 laser resonator in the TruLaser 2030 family of machines gets more power from a smaller resonator for greater performance, especially in thicker materials, says James Rogowski, product manager of 2-D lasers for Trumpf Inc., Farmington, Conn.

"Any time you use a coaxial gas resonator [like the TruCoax], the more surface area you have inside the resonator between the electrodes, and the more power you’ll get," Rogowski says. "So we made changes to the resonator to boost power. The higher-power resonator increases productivity with a diffusion-cooled, highly intense cutting beam in an ultra-compact footprint. The resonator is nearly solid state and has few moving parts, only a vacuum system and several switches. It doesn’t have a blower or parts that other CO2 resonators have. From a maintenance standpoint, there’s none except for a gas change every year or year and a half." Currently it costs less than $9 per hour to run, and Trumpf is working to bring expendable costs to less than $8 per hour, Rogowski says.

"As a laser manufacturer we want to increase our resonator sizes because of the demand for more speed for thinner materials and the ability to cut thicker materials," he says. "This new resonator can cut up to 3/4-in. steel, 5/16-in. stainless steel and 1/4-in. aluminum. It can cut the same thickness of materials that higher-wattage, fast-axial-flow CO2 4-kW resonators can. In fact, Trumpf’s TruCoax 3200 increased cutting speeds up to 100 percent in certain materials. This resonator gives a job shop the security to cut whatever comes through the door." FFJ


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