by Nestor Gula
Although laser cutting systems have been around for a while, they are still constantly evolving. Introduced a few years ago, the Direct Diode Lasers (DDL) feature prominently in some new machines. “Direct Diode Laser (DDL) is not a fiber laser,” says Al Bohlen, president of Mazak Optonics North America. “It is indeed a solid state laser, however the design is very different from fiber, how the beam is generated, and the wavelength (0.94μ-0.97μ) itself differs from that of fiber, disk or CO2 laser. DDL is absolutely without question the next generation of solid state laser technology.”
The DDL beam characteristics allow for control of mode shape that was not possible on fiber or disk systems and combined with a shorter wavelength, the cutting parameters yield impressive speeds and a greater edge quality over existing laser systems, according to suppliers, explains Bohlen. “DDL provides a new wavelength and beam (mode) control not possible on CO2, fiber or disk and allows for greater levels of cut performance. Most notably, our customers are very impressed with edge quality in comparison to fiber or disk and this is in addition to cut speed gains.”
A direct diode laser uses the light directly from a diode, unlike a disc or a fiber system where you have a laser medium. “You have a crystal, either a YAG crystal like a glass or quartz silica, doped with a rare element like a terbium, and the stimulation of those atoms, the terbium atom, is actually what produces the light,” says Brett Thompson, TruLaser product manager at TRUMPF. “Then you have light coming from the diodes, that goes into the crystal and bombards the terbium atoms with energy. They split and create the photon of light that ultimately we are going to use to cut with. So, your actual mission of light is going to be different. With direct diode technology, you’re removing that intermediate, the solid state component, the crystal, and you’re using the drill for light directly from the diode source.”
The advantages of this technology are that there are fewer and less expensive components, and systems are more energy efficient, so operating costs will be lower.
There is debate about whether this is a revolutionary or evolutionary technology. “It’s kind of somewhere in between,” says Thompson. “The difficulty is having really high output in a single mode solid direct diode lasers and that’s typically what we see in a scalable laser system like a disc – that’s probably going to be the choice for high power applications. But for those mid-power ranges and then as the technology advances, it certainly makes sense because with the diode technology you have not only low investment costs and lower operating costs because of the efficiency, but you do have also the ability, theoretically, to kind of pick and choose what output of light you want to use, which is really phenomenal when you consider welding copper; I want green light because of the coupling, the interaction with the beam is much better so I need less laser power to weld that sort of material as opposed to one light micron laser.” SMT