Fiber-Based Laser Micro-Machining

April 28, 2011
Flexible, precise, and affordable process for optimized industrial processing
A microscopic image of a workpiece made of V70 hard metal, the result of an optimized micro-machining technique that may be used for industrial-scale production is.

Together with six industrial partners, Germany’s Laser Zentrum Hannover e.V. (LZH) has developed a fiber-based, “picosecond” laser system that has achieved impressive results at micro-machining brass and aluminum. (A “picosecond” is a fraction of an instant: 10-12 of a second!) LZH is an R&D enterprise sponsored by the Lower Saxony Ministry of Economic Affairs, Labour and Transport that conducts development programs in the field of laser technology.

Industrial users have a long list of demands for micro-machining laser systems: the laser beam must be easy to focus, nearly non-fluctuating, and beam re-alignment should be minimized, as LZH explained. In addition, for practical application in micro-machining an industrial laser system must be as compact as possible, placed close to the workpiece, and yet not susceptible to the stress and other atmospheric factors that make manufacturing components such a rugged assignment.

Until now, solid-state lasers have been used for metal micro-machining. These systems are usually based on free-beam set-ups, which are easily prone to misalignment. Since the laser systems need water-cooling they are relatively large and difficult to integrate into a production line.

The new fiber-based, picosecond laser system that LZH has developed fulfils all the requirements for industrial use. It is the result of the PULSAR (PUlsed Laser System with Adaptive Pulse PaRameters) research project. It is flexible and adaptable to different settings because the laser oscillator and amplifier are separated. Depending on the material and the desired process results, the repetition frequency and the average output can be easily adapted to the current process, according to LZH. “Thus, quick and up to now unique optimization of the work steps is possible,” the researcher stated.

A laser diode with a wavelength of 1,03 µm and a pulse length of approximately 40 ps serves as the pulse source. The pulse repetition rate is flexible, and can be set between 50 kHz and 40 Mhz. Using a three-step amplifier, the pulse can be amplified from several 10 µW to an average output power of 14 W. At a repetition rate of 1 MHz, a pulse energy of 14 µJ is possible.

LZH goes on to report that the fiber-based laser system has an excellent beam quality, and resists the standard hazards of a difficult production environments, such as dust contamination, temperature fluctuation, or mechanical vibrations.

Specifically, the researchers report very good results have been achieved working with aluminum or brass. Because the system is smaller and less expensive than conventional solid-state lasers there are many applications for high-power laser machining, such as marking aluminum or stamping hard metal (V70), e.g., minting coins.

PULSAR is subsidized by an initiative of the German Federal Ministry of Education and Research known as INLAS (Integrated-optical Components for High-power Laser Sources.) Companies involved in the initiative include PicoQuant GmbH, InnoLight GmbH, LPKF Laser & Electronics AG, cicor Microelectronics, and Alltec GmbH FOBA Laser Marking + Engraving.