Burrs on cut and stamped edges of sheet metal increase the risk of injury and can often damage cables and scratch surfaces. For this reason alone, it makes sense to deburr such edges. Deburring with a laser offers several advantages. The edges can be selectively strengthened. In addition, the fatigue strength of parts can be increased and the tendency to cracking decreases. The Fraunhofer Institute for Laser Technology ILT in Aachen explains the advantages of laser deburring.
In the automotive industry, laser deburring has gained a foothold in a number of large-scale production processes over the past decade. "But the potential of this technology is far from exhausted." So says Dr Edgar Willenborg, expert for laser polishing and laser deburring at the Fraunhofer ILT. Deburring sheet metal in particular is straightforward. It improves the quality of parts and, thanks to processing speeds of up to 12 metres per minute, is also fast and efficient.
Mechanical processes
Basically, deburring is necessary to minimise the risk of injury. Moreover, sharp burrs on cut and punched edges often damage cables and scratch surfaces. Until now, mechanical processes were mostly used to remove burrs.
Laser deburring
However, research by Fraunhofer ILT shows that laser processes have clear advantages here. The process itself is straightforward. "The laser focus has to hit the front of the plate edge and cover it completely," Willenborg explains. There, the focused light beam briefly melts the metal edge and burr. The surface tension then causes the liquid metal to smooth itself. This creates a rounded edge. "Alternative process control makes it possible to not only round off the edge, but also strengthen it in a targeted way," says the expert. To achieve this, the institute has increased the power output of the laser. This extra energy input melts more material, which is placed around the edge as a strengthening round seam.
Various benefits
The smooth, rounded edges prevent cuts and damage to cables and surfaces. But the laser process can do more. It leaves defect-free edges. "This results in clear benefits in the fatigue strength and mechanical deformation behaviour of the sheet metal components." Tests on high-strength steel show that fatigue strength increased by 220 per cent as a result of laser deburring. At the same time, the deformation rate increased by 240 per cent. Until then, edge cracking can be avoided. The expert explains the positive effects as follows. Laser melting eliminates all edge microdefects caused by mechanical machining. Such pre-damages, which are invisible to the naked eye, are often where cracking begins.
Laser deburring is fast, clean and cheap
According to Willenborg, another major advantage of laser deburring over mechanical processes is that no grinding dust is produced. Instead of removing it, the process only briefly melts the excess material, making it relatively easy to integrate laser deburring into existing process chains and manufacturing environments. Where integration is possible, the benefits quickly become apparent. "Laser deburring is especially recommended for parts that are subject to heavy loads," he stresses. He cites chassis components as an example. The increased fatigue strength in the edge area allows their manufacturers to design them thinner and thus lighter and ultimately more economical.
Robots
For formed 3D sheet metal parts, the laser can be mounted on robots. An advantage here is that fibre-coupled diode lasers are already used for deburring. According to Willenborg, standard lasers in the near-infrared wavelength range are also cheap and readily available.
Featured image: Partially laser-rounded stainless steel sheet edges with a sheet thickness of 1.5 mm. (Photo: Fraunhofer ILT, Aachen, Germany)
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