USP laser system replaces wire EDM
In micro-cutting with ultra-short pulse lasers, a special trepanning optic enables right-angled and post-processing-free cuts in the micrometer range.
USP laser system replaces wire EDM: Laser systems have become the standard for many cutting processes in recent years due to their speed and flexibility. An exception has been fine cutting of high-precision components, as the accuracy in this process lagged behind traditional wire EDM due to heat input and sometimes imprecise cutting geometry. The company GFH GmbH, a manufacturer of laser micromachining machines, has now developed the "GL.evo", a system that combines an ultrashort pulse (USP) laser with a trepanning optic, enabling sharp cutting edges even for right-angled contours. The quality even surpasses that of wire EDM: The tolerances when following the cutting line in this new laser cutting process are within a few micrometers, and the surface roughness (Ra) of the produced surfaces is less than 0.3 µm. At the same time, the system is faster and can also be used with non-conductive materials.
The core of the new GL.evo system is a 50-W ps-laser with a pulse rate of up to 1 MHz. Instead of emitting a continuous laser beam, it produces ultrashort energy bursts lasting 10 ps each. This approach minimizes heating of the material around the entry point compared to traditional laser sources. Consequently, it prevents distortion or other heat-related changes in the material, allowing for seamless processing of even thin foils measuring a few micrometers thick. Moreover, it can accurately cut thicker workpieces of various materials up to 1 mm thick without requiring post-processing of edges or cut surfaces. This capability is achieved through GFH's specially developed optics, originally designed for micro-drilling: the "GL.trepan" trepanning optic combined with the fixed optics "GL.optifix." The former (GL.trepan) causes the laser beam to rotate at speeds of up to 30,000 rpm, ensuring an absolutely uniform and stable beam profile that allows for right-angled cuts. The kerf width can be adjusted from 50 µm. Additionally, using the entry angle of the laser into the trepanning optic, undercuts of up to 3° can be easily created. An integrated photosensitive detector monitors the beam in four dimensions and adjusts any deviations in alignment using controllable mirror deflectors.
The precisely conditioned pulses are focused by the "GL.optifix" and guided along the contour to be cut by the axes of the system. Errors in axis movement as well as laser beam diameter variations are compensated for, ensuring geometric accuracy. Additionally, the fixed optics include a ring-shaped gas nozzle that blows process gas onto the cutting interface. This serves two purposes: protecting the optics from slag splashes or vapors and driving away melted or vaporized material from the kerf, resulting in clean surfaces without burrs or droplets. Moreover, the process gas prevents oxidation of the surrounding area when working with metallic materials. Typically, a scanner is used to accommodate the high repetition rates of the ultrashort pulse laser. However, the trepanning optic "GL.trepan" efficiently delivers its energy into the material even at slower traverse speeds. Furthermore, the trepanning optic can also be used with a galvanometer scanner to represent the generally slow wobble or spiraling motion of galvanometer drives through the helical drilling optic and effectively utilize the high jump speed of the scanner. This enables hole patterns to be produced with the required dimensions in just a few seconds of processing time. This method is primarily used for very thin materials with processing times of a few milliseconds.
While the trepanning optic GL.trepan ensures a uniform and stable beam cross-section, the fixed optics GL.optifix focuses the beam and compensates for errors in axis movement. This results in clean cuts, as seen in this copper-beryllium spring.
For some time now, fine cutting applications have been realized using fiber lasers, among others. However, their cut surfaces do not meet the requirements of micro-cutting.
The "GL.trepan" optic is based on a cylindrical lens telescope that is rotated, thereby rotating the laser as well. This rotation allows for adjusting the entry angle to potentially create a slight undercut in the workpiece if needed.
With GFH's laser processing center, both ferrous and non-ferrous metals, as well as non-metallic materials up to a thickness of 1 mm, can be cut. The cutting speed depends primarily on the desired contour and surface quality. For example, with a copper-beryllium workpiece measuring 0.12 mm thick and requiring high precision, speeds of several hundred mm/min can be achieved. For 0.2 mm thick stainless steel, the speed reaches 60 mm/min. The time required for laser micro-cutting significantly undercuts the duration of a comparable wire EDM process. Furthermore, the versatile adjustment options of the trepanning and focusing optics—such as kerf width, cutting angle, speed, focus lens, and cutting nozzle—allow for straightforward adaptation to specific applications, ensuring cost-effective production even for small batch sizes.
Precision work in tight spaces: The GL.evo creates burr-free surfaces without the need for post-processing and allows for right-angled cuts through its trepanning optic, as seen in this tooth flank.
Even with non-conductive materials like ceramics, where conventional wire EDM is not applicable, sharp edges can be achieved using the ultrashort pulse laser system.