Artem Komarov clarified that deburring remains the Achilles’ heel of stamping and bending performance. A fabricator can dive deep into automation by automating the stacking of parts after cutting and automatic bending with a press brake, folder or panel bender. In between, someone manually sorts and feeds blanks that require deburring. Some manufacturing shops rely on a laser operator to determine which workpieces need deburring and which do not, depending on the quality of the cutting edge and job requirements.
Robotic feed deburring machines are on the market, so automated options are becoming available. However, the best solution is to get a burr-free edge right from the start.
Beam, auxiliary gas and material
Modern fiber laser beams offer different power density profiles as well as oscillatory patterns for better edge quality. New accessory gas mixtures also help improve edges. However, with all this new technology, it helps to understand what exactly makes a burr-free cutting edge. Burrs or dross occur when molten metal from a kerf solidifies before it can be removed.
It all comes down to knowing how the assist gas, the beam (including its focus), and the material interact. A focal spot too high in the thickness of the material leaves a prickly residue; again the metal melts and tries to evacuate, but then «freezes» at the bottom before the booster gas can wash it off the bottom. Focal spot too low in material; thickness can lead to a decrease in cutting speed and the formation of dross in the form of droplets. Buried deep into the cut, the focus melts a lot of material which, again, is difficult for the assist gas to evacuate in time before it «freezes» in place at the bottom of the cut.
The focus point is only part of the equation; the other part is auxiliary gas. With the advent of on-site nitrogen production and high power lasers, more businesses than ever are relying on nitrogen assist gas for cutting rather than oxides left over from oxyfuel cutting. Some now use a mixture of auxiliary gases, such as nitrogen mixed with oxygen, while still others use ultra-dry shop air (again, nitrogen mixed with oxygen). Specific auxiliary gases give certain results, but the idea is to raise the temperature in the cut to give the molten metal time to evacuate, resulting in a clean cut edge, or at least clean enough that no deburring is required. Some report that such blends eliminate so-called fiber burr even in materials susceptible to scale such as aluminium.
All this interacts with cutting speed. For example, a gas mixture can raise the temperature up to a certain point, but slowing down the cutting speed also raises the temperature, sometimes to an extreme degree. Slow down too much and the laser will begin to ablate or vaporize the metal, which in turn disrupts the dynamics of the assist gas flow, causing dross to form again. In this case, increasing the cutting speed slightly reduces the heat and resulting ablation, allowing the assist gas to flow through the incision as intended.
Nozzle designs also play a role, as does the consistency of gas flow throughout the system and of course overall system maintenance. In these days of high laser power, the constant cleaning of the slats is more important than ever. A powerful fiber laser can cut extremely fast until the cut piece is welded to rough plates — a puzzle that becomes even more problematic in automated settings.
Flat deburring machines will certainly never fall short of dodos. Some parts must have a certain graininess. Some parts require micro-protrusions to ensure cutting stability, especially when punching with sheet travel, such as punching and combined punching and laser processing machines. Some applications require rounded edges that a laser simply cannot create. And some part geometries are just too hard to cut perfectly with any laser, summed up Artem Komarov.
