Laser cutters are designed to make clean cuts, but in some cases, burrs can remain. While minor imperfections may seem like a normal part of the process, they can be avoided when operators make the correct adjustments to cutting parameters. To do that, the operator must know what happens when the laser beam, assist gas and work surface come together to create a cut edge. While there’s no secret to perfect laser cutting, there’s one element that’s under the operator’s control: the dynamics of gas flow.
Changing the Right Parameters
Modern laser cutters control the beam’s characteristics, such as its power and profile. Technicians (and machines themselves) may check a variety of parameters to ensure that the focus position input for the laser cutter matches that on the workpiece.
What Creates Burrs
A laser beam’s energy brings metals beyond their melting temperatures, and the assist gas removes molten metals from the kerf, or cut edge. When a cutter uses an inert gas such as nitrogen, the cutting process is solely reliant on the energy of the laser beam to melt the metal. However, when oxygen is used as an assist gas, it interacts with the metal, creating an exothermic reaction. For those reasons, less gas pressure is needed to eject the materials. In either event, burrs come from the molten metal or slag as it solidifies faster than it can be removed.
Slower Isn’t Always Better
The “lower and smaller” logic for gas pressure and nozzle diameter does not apply to cutter speed. When the operator goes too slowly, more heat is injected than is necessary, and vaporization disturbs the gas flow. The disturbance can cause more burrs, rather than less. By slightly increasing cutting speed, heat input and ablation are reduced, and the gas flow dynamic is restored.
It can seem like a delicate balancing act to get a clean edge without burrs. However, it boils down to two things: gas dynamics and laser beam parameters. A burr-free laser cut is about ensuring that these two factors work together to ensure that enough molten metal is removed, at the right time and in the proper way. Visit http://www.facebook.com/bosslasers to learn more about the company’s array of laser cutting products.