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New laser cutting modulating strategy tested with Mikrotron high-speed camera

Mikrotron EoSens CMOS camera. [Image courtesy of Mikrotron]

 

 

First invented in 1965, laser cutting technology works by directing the output of a focused laser beam onto a metal workpiece, vaporizing or melting the metal and creating a cut edge. Because of its non-contact characteristics, this technique prevents mechanical stress on the workpiece while maintaining extremely high cutting precision. Today, laser cutting is widely used in aerospace, construction, and automotive manufacturing, among other industries, and is typically controlled by a CNC for accuracy and repeatability.

Improving cutting quality
Modulating a laser beam's intensity distribution optimizes energy delivery to the process zone, resulting in better cutting speed, cut edge quality, and cut kerf geometry. The conventional approaches to modulating use the Static Beam Strategy (SBS) or the Dynamic Beam Shaping (DBS) method.

Scientists at KU Leuven, an international research community located in Leuven, Belgium, recently conducted a comprehensive investigation into a new strategy of modulating beam intensities they termed "dynamic intensity modulation" and compared it to SBS and DBS while cutting 15-mm-thick mild steel. This novel approach modulates the intensity distribution using oscillation speed alteration.

Experiments were conducted using an industrial 2D flat-bed laser cutting machine featuring 4-kW laser power and equipped with a multimode fiber laser source producing a top-hat intensity distribution. The laser beam was guided to the process zone via an optical fiber.

To gain visual insights into the dynamic flow of molten material within the cut kerf, the scientists relied on a Mikrotron EoSens 1.3 Megapixel CMOS camera equipped with a Navitar Zoom 7000 lens. An OD 6 notch filter was placed in front of the camera lens to remove reflected or scattered laser light.

The Mikrotron camera's region of interest was configured to 160 x 370 pixels with the exposure time fixed at 10µs, resulting in a frame rate of 5,000 frames per second. Dynamic range adjustment prevented overexposure, therefore enhancing visualization of the crude contrast between the cut edge and the molten material inside the kerf.

Once captured, the cut edge images were scanned at 100x magnification with an optical microscope. An algorithm was applied to measure the dross area using the 2D images. Additionally, 3D images were generated to assess the roughness of the cut edge.

Images from Mikrotron camera of cut edges for SBS and the three different DBS approaches: (a) SBS, (b) Rear, (c) Normal, (d) Front. [Photo courtesy of KU Leuven]

 

 

 

 

According to a Procedia CIRP paper on the study, "Utilizing the Rear beam leads to an increase in both dross and roughness compared to the Normal beam. Conversely, employing the Front beam strategy results in a notable reduction in these values. This enhancement in cut edge quality is visually evident in Fig. 2, progressing from the static beam to the Rear, Normal, and ultimately Front beams."

Testing dynamic intensity modulation on the cutting of mild steel indicated a notable enhancement in the cut edge quality compared to either the SBS or DBS strategies. The dynamic intensity modulation technology, according to the scientists, can also be used for other laser processes like hardening and welding.

Conclusion
This work by KU Leuven demonstrated the importance of maintaining precise control over the distribution of laser beam intensity, and its testing and conclusions uncovered new opportunities to maximize laser processing performance in ways that go beyond traditional techniques. Dynamic intensity modulation can be used for laser cutting as well as other laser operations such as welding and hardening. Dynamic intensity modulation can be applied to laser welding to process materials with varied thicknesses, dissimilar materials with different thermal properties, or a combination of the two. Similar to this, uneven surfaces -- especially those with sharp edges or holes -- may provide problems for laser hardening applications.

Learn more about Mikrotron cameras and vision systems at mikrotron.de/en/index.php.

Source: Mikrotron, a brand of SVS-Vistek GmbH

Published May 2025

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