Daimler specify beam inspection for production

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Car maker Daimler has worked with Ophir Photonics to develop a non-contact beam monitoring solution to increase the rate and ease of beam inspection. At this year’s European Automotive Laser Applications conference (EALA) in Bad Nauheim, Germany, in February, Christian Dini, the director of global business development at Ophir Photonics – alongside Daimler’s Dr Andreas Bünting, responsible for process engineering for machining with lasers – presented the system, known as BeamWatch Integrated, for use on Daimler’s automated production lines. 

Daimler uses beam monitoring systems to ensure lasers for welding differential gears are aligned and the focal spot is in the correct position. Traditional beam profilers were previously used for such applications. However, these were difficult and time consuming to use, which typically led to only one beam measurement being made per shift. Additionally, they interfered with the beam to take a measurement, meaning they could potentially alter the beam in the process. Combined, these characteristics did not make such profilers suitable for the high-throughput production environment of an automotive factory. 

Process gases and stray particles in laser work cells can degrade the coatings on optical elements, causing them to warm up and change shape. In addition, when using a fibre to deliver a beam, continuous back-and-forth bending of the fibre during processing can lead to it becoming misaligned. Both can cause a shift in the focal spot position of the beam, which changes the properties of the welds. If the focal spot moves along the z-axis then the power density and spot size on the weld surface changes. This can lead to a hole being drilled if the focal spot is driven too deeply into the material, or not having enough power density resulting in a weaker join. 

BeamWatch is an 8kg non-contact beam analysis system that does not need to interfere with the beam in order to take a measurement. Rather than generating a beam profile, it instead gives an almost real-time video signal of the beam caustic around the focal spot location. 

While a beam profile effectively takes a slice out of a beam to give parameters such as power distribution and power density, a video of the whole beam caustic grants access to parameters such as pointing angle and focal shift, making it a lot easier to identify where and what is malfunctioning in the laser, according to Dini. ‘A single beam profile is weak compared to looking at the whole caustic and its behaviour over time, or changes in power if you want to troubleshoot or control a whole laser beam delivery assembly,’ he said. ‘Whenever you have any issue, you will be able to see it directly on your measurement image.’ 

Since the introduction of BeamWatch Integrated into its welding processes, Daimler has been able to perform a measurement after every single completed part. ‘This means they [Daimler] know up to every individual part whether the laser beam is as expected or starting to change,’ said Dini. ‘It avoids the production of any bad parts due to a fault with the laser, as the machine experts are warned when any of the beam parameters reach a tolerance limit. This allows them to repair or replace the necessary laser components before a bad part is made, not only reducing the cost inherent to destructive testing, but also allowing them to manage consumables and spare parts of the beam delivery system to actual demand, rather than replacing those either after failure or by estimated intervals – which also saves costs.’ 

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MKS Instruments – Ophir Business Unit

When designing or applying for a laser or when a laser system is no longer meeting specifications, one needs to know many different beam parameters, such as beam width and size, beam profile, and M2.

Ophir offers a wide variety of beam profiling products enabling users to obtain a precise measurement of the laser beam: BeamGage® is known as the most powerful beam profiling software in the laser market. Ultracal®,its baseline correction algorithm, is the basis for ISO 11146-3, the ISO standard for accuracy when making beam measurements.

In order to serve for a broad range of applications BeamGage® can be combined with both, camera-based as well as slit-based profilers covering the spectral range from FAR IR to THz. With its brand-new GigE camera SP920G, Ophir enables beam profiling in OEM applications, production cells or other security sensitive surroundings.

When it comes to fast and accurate measurements of the M2, Ophir offers BeamSquared®, the robust, portable M2 laser beam propagation system for CW and pulsed lasers.

www.ophiropt.com/laser--measurement

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Among the latest releases of beam analysis equipment are the PowerMax-Pro laser detectors from Coherent (www.coherent.com). These sensors give power measurement of continuous-wave laser beams of 3kW, and 5kW peak power with modulated laser beams.

The new PowerMax-Pro kW models will be particularly useful for materials processing applications based on high-power fibre lasers, CO2 lasers, and solid-state lasers, including welding, cutting, drilling, and engraving. PowerMax-Pro gives a stable kilowatt power reading in microseconds with no overshoot. In addition, the sensor’s optical design traps more than 99 per cent of the incident light inside the enclosure – 100 per cent when used with a direct QBH fibre adapter option, resulting in a Class 1 measurement system.

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Debe Lasers’ (www.debe.co.uk) In Line Beam Analyser (ILBA) passes a reflective needle through the laser beam to sample medium to high power lasers for both initial verification of the laser and for detecting changes in the beam over time. The system can sample 10W to 8kW continuous-wave and pulsed beams continuously or periodically, even while the laser is being used, as ILBA does not affect the beam and power loss is negligible. The laser beam characteristics analysed and recorded include beam position, beam diameter, power distribution and laser power. ILBA is a compact unit, connected via USB to the monitoring PC.

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The Beam Waist Analyser Monitor (BWA-MON) by Haas Laser Technologies, supplied in Europe by Laser Components (www.lasercomponents.com/uk), provides continuous real-time data covering the entire laser beam profile. The BWA-MON doesn’t have any moving parts. It uses an identical reflection of the actual beam to determine characteristics like beam waist and size, M2 or thermal lensing. Working at 50Hz, the system allows for several measurements per second.

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Finally, the PeakDetect from Photonic Solutions (www.photonicsolutions.co.uk) gives precise in-line monitoring of laser pulse variations to help maintain laser reliability and process stability. It measures the laser repetition rate, average power and non-linear efficiency, and thereby also calculates the relative peak power and pulse quality – how far the pulse is above the Fourier-transform limit. The compact and robust design makes PeakDetect ideal for incorporation into larger laser systems or production lines, and as a portable service tool.

The PeakDetect is ideal for applications involving ultrashort pulse lasers that can feature underlying non-linear distortion effects, pulsed lasers with changeable pulse durations, or applications where the results depend strongly on stable pulse conditions.

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