Even though thick plate cutting has a subsidiary market share in laser material processing, it is still a necessary feature for state-of-the-art machines. In recent years, research has concentrated on various quality issues, especially dross attachment and surface appearance, that compromise productivity. This has resulted in notable improvements.
About $1.1 billion was allotted to research and development of macro laser metal cutting in 20161. Roughly 20 percent of this research addressed sheet thicknesses above 4 mm. Ongoing market monitoring points to a persistent industrial interest in this sector, because thick plate performance is a benchmark of laser cutting machines. CO2 laser cutting remains the established method for industry; every laser cut is compared with CO2
However, in recent years the market share of solid-state laser cutting devices has increased by a compounded annual growth rate of more than 10 percent2. Solid-state lasers offer various advantages, such as higher efficiency, easier handling and faster feed rate for thin sheets. However, in the case of thick plates, they have not achieved acceptable cut quality, nor even a higher feed rate in comparison to CO2 cutting.
A basic approach to achieve optimal results for solid-state laser cutting is to adjust the cut kerf dimensions for each application. (Of course, these must take into account influencing factors such as energy deposition and heat conduction.) In the case of thick plates, an appropriate kerf width is required to maintain melt ejection.
Static beam shaping is one common method for adjusting cut kerf dimensions, but the result is not always sufficient. With this technique, various optical elements can be utilized to modify the laser beam for spot size, beam geometry, amount of foci, polarization state and other factors. The result is an optical setup that suits a specific cutting task. This is advantageous for specialized tasks such as serial production. But static beam shaping cannot adequately accomplish the frequently varying operations that constitute the daily business of industry.
In addition, with solid-state laser cutting of thick plates, mechanical post-treatment typically is needed to remove dross. Thus, an additional production step is necessary that requires manpower and machinery. Static beam shaping can overcome this challenge by using laser sources with higher output power. Although this increases productivity, it also increases investment and running charges.
Innovative laser cutting
Fraunhofer IWS is pursuing dynamic beam shaping (DBS) as a solution to the challenge of laser beam cutting of thick metal plates. It addresses high productivity, improved quality and efficiency in combination with standard equipment. The technology is considered an add-on to the conventional process.