it’s the same story, marking pacemakers, surgical instruments, or hearing aids, which are made of many materials.”
In stent cutting, the state-of-the-art cutting method still is the fusion cut with mostly 100 to 200-W fiber lasers, Weiler adds. “This works well for stainless steel, maybe for Nitinol, because here and there you can allow some postprocess- ing, and you need the postprocessing because it’s a fusion cut, where the laser melts the metal and you have gas nozzles that blow the metal out of the cutting surface.”
A Nitinol stent cut with Trumpf’s TruMicro picosecond green laser’s cold-cut process.
With fusion-cut stents, cutting kerfs typically are 10-20 µm, he notes. Trumpf offers fiber lasers, as well as newer short-pulse picosecond lasers in the green wavelength specifically aimed at cutting stents, which have relatively thin walls and don’t require higher power lasers. “For stent cutting, we typically use a green picosecond laser. The reason is because it’s more versatile—it can cut a metal stent as well as polymer and nonmetal stents,” Weiler states. “This is very different from the fusion cut. Picosecond pulses are so short that the material is not molten, like with the fusion cut, it’s vaporized. So now we don’t have any metal, we just have vapor, so we just need some kind of nozzle to blow away the vapor—people call it ‘cold cut’ or a cold process, and that eliminates any residual heat in the material, which results in perfect edge quality, and especially for the nonme- tallic stents, they cannot be cut with a fusion cut at all, the cutter would just melt the whole thing.” Picosecond lasers like the Trumpf
TruMicro Series 5000 laser line can vaporize metal or nonmetals using 50W of power and a pulse energy rated at up to 250 microjoules. These short pulses of less than 10 picoseconds vaporize the material so fast that no heat-affected zone (HAZ) can be detected. Micropro-