Dr. Milton Pereira Profile

Dr. Milton Pereira

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Publications (3)

Proceedings Article | 16 March 2015 Paper

Contributions for the next generation of 3D metal printing machines

M. Pereira, U. Thombansen

Proceedings Volume 9353, 935318 (2015) https://doi.org/10.1117/12.2079027

KEYWORDS: Spatial light modulators, 3D printing, Laser scanners, Printing, Manufacturing, Metals, Laser processing, 3D scanning, Process control, Actuators

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SPIE Journal Paper | 8 October 2014 Open Access

Process observation in fiber laser–based selective laser melting

Ulrich Thombansen, Alexander Gatej, Milton Pereira

OE, Vol. 54, Issue 01, 011008, (October 2014) https://doi.org/10.1117/12.10.1117/1.OE.54.1.011008

KEYWORDS: Fiber lasers, Signal processing, Spatial light modulators, Manufacturing, Lenses, Sensors, Data acquisition, Laser processing, Cameras, Pyrometry

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The process observation in selective laser melting (SLM) focuses on observing the interaction point where the powder is processed. To provide process relevant information, signals have to be acquired that are resolved in both time and space. Especially in high-power SLM, where more than 1 kW of laser power is used, processing speeds of several meters per second are required for a high-quality processing results. Therefore, an implementation of a suitable process observation system has to acquire a large amount of spatially resolved data at low sampling speeds or it has to restrict the acquisition to a predefined area at a high sampling speed. In any case, it is vitally important to synchronously record the laser beam position and the acquired signal. This is a prerequisite that allows the recorded data become information. Today, most SLM systems employ f-theta lenses to focus the processing laser beam onto the powder bed. This report describes the drawbacks that result for process observation and suggests a variable retro-focus system which solves these issues. The beam quality of fiber lasers delivers the processing laser beam to the powder bed at relevant focus diameters, which is a key prerequisite for this solution to be viable. The optical train we present here couples the processing laser beam and the process observation coaxially, ensuring consistent alignment of interaction zone and observed area. With respect to signal processing, we have developed a solution that synchronously acquires signals from a pyrometer and the position of the laser beam by sampling the data with a field programmable gate array. The relevance of the acquired signals has been validated by the scanning of a sample filament. Experiments with grooved samples show a correlation between different powder thicknesses and the acquired signals at relevant processing parameters. This basic work takes a first step toward self-optimization of the manufacturing process in SLM. It enables the addition of cognitive functions to the manufacturing system to the extent that the system could track its own process. The results are based on analyzing and redesigning the optical train, in combination with a real-time signal acquisition system which provides a solution to certain technological barriers.

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Proceedings Article | 20 February 2014 Paper

Tracking the course of the manufacturing process in selective laser melting

U. Thombansen, Alexander Gatej, M. Pereira

Proceedings Volume 8963, 89630O (2014) https://doi.org/10.1117/12.2040330

KEYWORDS: Manufacturing, Laser processing, Spatial light modulators, Cameras, Lenses, Scanners, Sensors, Signal processing, Optics manufacturing, Laser applications

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