APPLICATION FOCUS: POLISHING NEWSON NVFEATURED PRODUCT Higher-level cell control (communication and safety) Robot SCU (ScanControlUnit) Scannersystem Laser ON/POWER Laser system


Control Safety signal Power supply


Figure 2: A schematic of the communication and synchronisation in between the elements of the Alphanov team’s laser polishing setup


feature a five-axis platform that enables parts of up to 100kg to be fixed and moved in three dimensions during processing. As our system does not require this platform, it is able to process parts heavier than 100kg. Our team at Alphanov put


this into practice using a 10kW, 1,070nm YLR 10,000 continuous-wave (CW) laser from IPG, along with a galvanometric IntelliWeld FT scanner by Scanlab that was mounted on a robotic arm from Fanuc. A ScanControlUnit (SCU), from Blackbird Robotics, was also used to monitor and control the synchronisation of the movement between the scan unit and the industrial robot. This avoids any stitching errors and enables the continuous processing of large 3D parts. Figure 2 shows the schema


of communication in between the different elements. In order to control laser power in co-ordination with the scanner and/or robot movement during


operations, an interface to the laser source must be implemented. Unlike static processing, here the robot movement takes place in sync with the process (beam scanning) using bus communication between the robot unit and SCU. This process is also called on-the-fly (OTF) processing, and makes it possible to achieve maximum process efficiency with minimised cycle times. For the moment we have studied the upscaling of process speed with spot diameters up to 5mm. With it, laser polishing has been conducted with power up to 2.5kW and demonstrated for a one-pass process. It was shown it is possible to laser polish an initial surface Sa = 6µm down to Sa = 0.5µm in 3.25s/cm². With 10kW power reserve, we can use bigger spot size up to 15mm, and in doing so will be able to reduce processing times even further. High-speed beam scanning has not yet been investigated, but with it we envisage being able to reduce processing times further still.


Figure 3: The Alphanov team’s laser polishing setup can also be used to remodel surfaces. Pictured is a reflector mould for vehicles


The achieved processing speed outperforms polishing systems using CW lasers. Our system cannot be compared to systems using pulsed lasers, as these are instead used to polish from Sa = 1µm down to Sa = 30-50nm, while CW lasers are used to polish from Sa > 10µm down to Sa = 300-200nm. In order to bring this process and setup further to successful application, adjustments in thermal accumulation control are needed.


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Newson NV produces rhothor™ smart deflectors with integrated digital regulator using patented Moving Coil Technology offering State of the Art Performance in laser deflection, with very low power consumption, superior speed, low long-term drift. RTA runs aperture 10-20mm mirrors, RLA aperture 30- 35mm mirrors (average power consumption/axis: RTA 2 Watt and RLA 3 Watt), each steered by 24-bit setpoints over a single coax combining power and data. Newson NV produces the


CUA32 as complete laser beam steering unit, including


license free software. It communicates with a host computer, controls table stages, lasers and several I/O’s. Supporting streaming, stand-alone operation and master-slave (up to 8 deflection systems), it is a DIN rail compatible system allowing easy integration in any machine design. Directional multiphase wobble functions and speed modulation are standard integrated, ideal for laser welding and polishing. Interface adapters for interfaces like XY2-100 are available for third party laser deflection systems. www.newson.be


The potential of this robot-


based setup is not only limited to laser polishing. As we are capable of melting the surface to control its roughness using melt pool movement by fast laser power modulation, we are also able to move this melted material across the surface and shape it with different geometries. A remodeling process uses the same principle as laser polishing (melting a surface without material waste), therefore, our setup can also be adapted for the laser remodeling of large 3D surfaces. Applying this technology, we have fabricated defined topographies with astonishing accuracy for mould generation, an example of which can be seen in figure 3. To conclude, laser polishing


can be upscaled using a high- power continuous-wave laser, a large spot diameter and a robotic arm. The setup used by our Alphanov team enables the continuous processing of large surfaces without the need to use a stitching method. We are aiming to further decrease the processing time, not only with a bigger spot diameter, but also with an optimised and efficient process strategy using the full capability of OTF processing, enabling us to polish large-scale additively manufactured parts in almost all kinds of material. l


Florent Husson is an R&D engineer for laser micromachining at the French research institute Alphanov


SPRING 2020 LASER SYSTEMS EUROPE 33


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