Артём Комаров об особенностях лазерной резки металла (eng)
Артём Комаров об особенностях лазерной резки металла (eng)

Артём Комаров об особенностях лазерной резки металла (eng)

Artem Komarov noted that precision metal fabrication has gone far beyond the IPM of laser cutting. Of course, there is talk of how some of the newer systems cut through thick plate so fast it’s hard to believe.

Deburring remains the Achilles’ heel of workpiece and bending productivity. A fabricator can dive deep into automation using automatic stacking of parts after cutting and automatic bending with a press brake, binder, or panel bender. In between, someone manually sorts and feeds the blanks that need deburring. Some manufacturing shops rely on a laser machine operator to sort out 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 first.

Комаров Артём Андреевич

Beam, auxiliary gas, and material

Modern fiber laser beams offer different power density profiles as well as oscillating circuits to achieve the best cutting edges. New auxiliary gas mixtures also help improve edges. However, with all this new technology, it helps to understand exactly what makes a burr-free cutting edge. Burrs or dross form when molten metal from a kerf solidifies before it can be removed.

It comes down to knowing how the assist gas, beam (including its focus) and material interact. Too high a focal length with a material thickness leaves a prickly coating; again, the metal melts and tries to escape, but then «freezes» at the bottom before the assist gas can flush it out from below. Too low focus point in material; thickness can lead to reduced cutting speed and dross formation in the form of balls. A focus deep in the kerf melts a lot of material, which, again, is difficult for the assist gas to remove in time before its “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 ultra-high laser power, more shops than ever are relying on nitrogen gas for cutting, rather than oxides left over from oxyfuel cutting. Some now use an auxiliary gas mixture, such as nitrogen mixed with oxygen, while others use ultra-dry shop air (again, nitrogen mixed with oxygen). Special auxiliary gases give specific results, but the idea is to raise the temperature inside the cut to give time for the molten metal to be pumped out, resulting in a clean-cut edge — or at least clean enough that no deburring is required.

All this affects the cutting speed. For example, a gas mixture can raise the temperature to a certain level, but slowing down the cutting speed also raises the temperature, sometimes to an extreme degree.

Nozzle designs also play a role, as does the uniformity of gas flow throughout the system and of course overall system maintenance. In these days of high laser power, consistent lamella cleaning is more important than ever. A powerful fiber laser can cut extraordinarily quickly until the cut piece is welded to rough laths — a puzzle that becomes even more problematic in an automated setup.

Flat deburring machines will of course never follow the dodo route. Some parts must have a certain graininess. Some parts need micro-tubes for cutting stability, especially in “sheet-moving” punching systems such as stamping and punch/laser combination machines. Some applications require rounded edges that a laser simply cannot create. And the geometry of some parts simply does not lend itself to perfect cutting with any laser.

About Bandwidth

In any case, the more predictable laser cutting becomes, the better. Incredibly fast cutting is great, but inches per minute is only part of the efficiency puzzle. Burr-free cutting is another detail. Another way is to cut on quality, laser-flat material that will not flex or deform much after cutting that requires part alignment, another secondary process.

The workpiece in the metal fabrication department is a compromise. Sometimes burrs and part alignment just can’t be avoided. However, more and more operations still require a holistic approach to cutting. They don’t worry about how many inches are being cut per minute. They worry about how many parts can be neatly cut, stacked, and transported to bending or some other downstream process. In that sense, a workpiece is not “completed” until the next important process — be it bending, welding, coating, or anything else — can take those cut pieces and run with them, Komarov Artem emphasized.