Laser Applications: Material Processing & Precision
Laser Applications in Material Processing
Stainless Steel Welding (1.5mm)
Material: Stainless Steel, 1.5mm thickness. Process: Welding. Requirements: Dimensional accuracy, moderate precision.
From an absorption perspective, Excimer lasers are optimal at room temperature. However, this application involves approximately 20µm penetration across multiple layers. As temperature increases, CO2 laser absorption rises from 10% to 90%, but this is undesirable as it leads to the stainless steel liquefying. A high beam quality is not strictly necessary, making this suitable for microwelding or microcutting. A 1000W laser is needed for rapid processing of 1.5mm thickness, or a 500W laser for slower speeds. A Diode laser offers the best solution due to its lower beam quality and higher wall-plug efficiency. Fiber optics are typically used for guidance, but a direct diode laser (a compact laser located on the processing head) eliminates the need for a guiding system. Given the large size of the workpiece and the moderate precision requirements, a robotic positioning system is appropriate.
Titanium Pacemaker Welding (1mm)
Material: Titanium (Steel), 1mm thickness. Process: Welding pacemakers. Requirements: Dimensional accuracy, high precision.
It’s crucial to avoid damaging internal electronics, necessitating low power. An Excimer laser is unsuitable due to its limited penetration depth (around 20µm), whereas 1mm is required. Excimer lasers are primarily used for plastics and are not suitable for welding or cutting metals in this context. CO2 lasers are a viable option, as melting is required for welding. A 1000W laser is sufficient for 1mm thickness; therefore, Disk lasers are not ideal due to their higher power requirements. Fiber lasers, with their superior wall-plug efficiency (10x that of Nd:YAG), could also be considered. To prevent damage to electronics, a good beam quality is essential. CO2, Nd:YAG, and Fiber lasers all offer this at the required power. However, an Nd:YAG (lamp-pumped) laser is preferred to minimize radiation and heat input to the weld. Fiber optics are not ideal due to beam divergence and the need for focusing optics at both ends, which degrades beam quality. Mirrors are a better choice for beam delivery. Ideally, the laser would be directly mounted without mirrors, and a CCD Camera would be used for monitoring. An X-Y Gantry positioning system provides the necessary precision.
Methacrylate Sheet Cutting (1mm)
Material: Methacrylate sheets (insulating), 1mm thickness. Process: Cutting. Requirements: Large dimensions, moderate precision.
Methacrylate is transparent to visible light and 1µm radiation (Nd, Fiber, Diode, Disk lasers) due to low absorption. Excimer lasers are unsuitable for this thickness. They are best suited for superficial marking. Only a CO2 laser provides the necessary beam quality and, with 100W, can effectively cut 1mm thick material. Fiber optics cannot be used due to the high wavelength of CO2 lasers; therefore, mirrors are required for beam guidance. Due to the large size of the workpiece, an X-Y Gantry system is more practical than a robot for moving the laser or optics.
Carbon Steel Hardening (1.5mm)
Material: Carbon steel, 1.5mm thickness. Process: Hardening treatment. Requirements: Dimensional accuracy, low precision.
Excimer lasers are unsuitable due to their limited penetration. The goal is to harden several micrometers, not just the surface. While Excimer lasers have good absorption at room temperature, CO2 laser absorption increases significantly with temperature (10% to 90%). However, we want to avoid melting the material, only hardening the surface above the transition temperature. Therefore, CO2 lasers are not optimal. High beam quality and tight focusing are unnecessary for hardening, making Nd and Fiber lasers less suitable. An HDL Diode laser is the best choice due to its lower beam quality and superior wall-plug efficiency. Both fiber optics and mirrors could be used, but fiber optics offer a lighter and more easily maneuverable structure. Given the large material size, an X-Y Gantry system is preferred over a robotic system.
Resin Stereolithography (500mm)
Material: Resin, 500mm. Process: Stereolithography. Requirements: Dimensional accuracy, low precision.
Excimer lasers are the best choice for stereolithography because the resin requires UV curable radiation, which UV lasers provide. The layer thicknesses are also very small. Mirrors are used in the scanning system because the workpiece is not excessively large, combined with an X-Y Gantry system.