Tools made from hard ceramic materials such as drills, milling heads, rollers and even punch inserts are highly resistant to wear, but the tools used to manufacture them wear out rather quickly. A process developed at Fraunhofer Institute for Laser Technology ILT (Fraunhofer ILT) changes this by using an ultrashort pulse laser to shape and polish these hard material components without changing the clamping setup. According to the researchers behind the advancement, even commercially available ultrashort pulse (USP) lasers with a power of 20-40 W are capable of effectively removing the hard materials used in toolmaking. The material vaporizes when met with the high-energy laser pulses, which last just a few picoseconds. Because this happens at frequencies in the MHz range, laser material ablation reaches surface of up to 100 cm2 per minute. High-energy pulses lasting just a few picoseconds vaporize the material during ultrashort pulse (USP) structuring. In the second step, the laser, now running with different parameters, melts the top 0.2–2 µm of the surface. It then smooths out. Courtesy of Fraunhofer Institute for Laser Technology ILT (Fraunhofer ILT). The potential of USP processing isn’t limited to forming materials by vaporizing them. The Fraunhofer ILT researchers developed a process chain in which the same USP laser not only forms and structures via ablation, but also subsequently polishes the tool surfaces. “The USP laser is a universal tool we use to conduct various processing steps, sometimes in the same clamping operation,” said Sönke Vogel, team leader for 3D Structural Ablation at Fraunhofer ILT, who has been driving the process forward together with Astrid Saßmannshausen, team leader for Structuring of Transparent Materials. The key to linking the process steps lies in the parameterization of the laser. While material is ablated with high pulse energy and a low repetition rate, the opposite is true for polishing. The USP laser introduces energy into the surface of the workpiece at a pulse frequency of up to 50 MHz, where this energy accumulates and only melts the top 0.2-2 μm. The material doesn’t vaporize, but forms a molten film that smooths itself out due to surface tension and solidifies as it cools. The surface properties can also be controlled via the process control. “With USP laser polishing, for example, it is possible to smooth out micro-irregularities while retaining macroscopic structures,” said Saßmannshausen. A mold tool made of tungsten carbide-cobalt was first USP-structured and then polished with the same laser. The mechanical processing of such hard materials is associated with extensive and costly tool wear. Courtesy of Fraunhofer ILT. In addition, the laser process makes it possible to polish complex 3D surfaces with micrometer precision. Specific areas can be selectively treated to adjust surface properties locally or to finish only the necessary zones — saving time in the process. USP polishing thus complements existing laser macro- and micro-polishing methods by enabling even greater precision and localized control. Depending on the process requirements, laser polishing can achieve surface rates of 10 to 100 cm² per minute, which is almost on par with the surface rates of the preceding material ablation method. “The combination of both processes with a laser in the same clamping operation enables companies to expand their range of services with existing USP lasers or to significantly accelerate the amortization of a new purchase,” said Saßmannshausen. Above all, however, it is suitable for replacing mechanical processes for machining hard materials, thus positioning the method to put an end to the sometimes immense tool wear involved in their manufacture. This not only reduces costs, but also specifically improves resource and energy efficiency in practice. According to Saßmannshausen and Vogel, the potential of the process combination is far from exhausted. With faster polygon scanners, higher laser powers, and enlarged laser spots, the surface rates could be considerably increased.