New development in laser manufacturing.

Research Lab breaks new ground in laser manufacturing processes using Mikrotron Vision Technology.

Bayerisches Laserzentrum GmbH or simply "BLZ" is an independent, non-profit research association based in Erlangen, Bavaria, that aims to open new fields of application for photonics and laser technology through research, development and knowledge transfer. Acting as a link between the scientific community and industry, BLZ serves as an engineering partner, trainer, solutions provider, and a developer and manufacturer of application-specific optical systems and components.

Florian Kaufmann, who works in BLZ's Process Technology Metals department, is active in application-oriented research. “In applied research, we work closely with industrial partners and the Chair of Photonic Technologies at FAU Erlangen-Nürnberg. We are primarily investigating laser processes for copper and aluminum. Also, there is considerable research in the area of ​​e-mobility, as welding is required for the contacting of battery cells and the manufacture of power electronics for battery-electric vehicles."

Research conducted by BLZ on laser-based processes requires the continuous monitoring of processes such as welding, cutting, soldering and generative manufacturing. To accomplish this, BLZ acquired a Mikrotron MotionBLITZ Eo Sens® mini2 high-speed memory camera in 2020. Compact yet powerful, the MotionBLITZ Eo Sens® mini2 is ideal for confined lab spaces. In fact, the MotionBLITZ Eo Sens® mini2 replaced a previous generation of a Mikrotron camera that BLZ had deployed in an identical test system, therefore upgrading that system to perform more extensive studies. Specific research targeted the welding of aluminum and copper materials, remote welding of ferrous and non-ferrous metals, laser material processing with wavelengths in the visible range, and soldering microelectronic components.

Operating at a resolution of 1696 x 1710 pixels, the MotionBLITZ Eo Sens® mini2 is able to detect any defects -- so-called seam inhomogeneities -- such as weld spatter, pores and cavities that may occur during laser processing. It captures more than 200,000 frames per second allowing the operator to freeze-frame any action. By the camera identifying how and when these defects arise, countermeasures can be put into place to remedy errors. For example, splashes occurring in a powder bed during additive manufacturing can be detected and the process adjusted accordingly. Another instance would be the precise visual capture of the characteristics of a weld seam, including its melting dynamics and material evaporation, during a steam plasma torch operation.

Versatile as it is powerful, the MotionBLITZ Eo Sens mini2 can be installed either directly in the beam path or on the outside of a machine BLZ is testing. Depending on the technology, the camera can also be placed on a tripod or robot arm in order to document research findings. Due to its internal memory, the use of the camera is possible without connection to any notebook or PC. Three seconds at full resolution and speed can be recorded without being dependent on an extensive experimental set-up. In addition, the Gigabit Ethernet interface allows an operator to control multiple cameras from any standard Notebook/PC over a distance of up to 100 meters.

“The recordings from the Mikrotron camera analyze process stability. We want to understand how errors occur in the various applications and then use this knowledge to avoid them," said Kaufmann. “For example, there is increased spatter formation in copper welding, especially in laser beam welding with conventional laser beam sources, that emit approximately 1 µm in the infrared spectrum. This has to be recognized immediately, because in the worst case it can lead to product rejects or damage to a component."

Great potential is seen in laser beam sources of visible wavelengths, which are currently taking the development step towards the high-power class. BLZ currently has a laser system from Trumpf GmbH that offers 3 kW output power at 515 nm wavelength.

"The investigation of the influence of the changed processing wavelength on the process result in laser beam welding of copper is an essential area in which we want to use the Mikrotron camera system."

While the system configuration currently limits the duration of a camera recording to 1.5 seconds, longer observation times can be selected. For example, when soldering, images are recorded for up to 10 seconds, but this is accompanied by a smaller image section. Depending on the issue, camera recordings are either evaluated subjectively or by using an algorithm.

"Overall, we are very satisfied with the system," says Kaufmann.

@mikrotron @OConnellPR #PAuto #Laser

Monitoring Laser Melting of Powders.

Industries worldwide are now developing prototypes from 3D metal printing. Slowing the adoption of this form of additive manufacturing beyond prototyping and into larger-scale production is the high cost of system acquisition, resulting in industries that deploy 3D metal printing producing only small quantities of very expensive and complex structures with low weight and high strength, such as those increasingly required in aerospace, medical technology or auto racing.

Despite its high costs, it is difficult to overlook the value of 3D metal printing when compared to subtractive material processing, casting processes or even other types of additive manufacturing. Production of a workpiece by 3D metal printing allows for completely new designs. In a single operation, it is possible to create structures with a high degree of geometrical freedom that would otherwise have to be assembled from several individual workpieces.

For the 3D printing process, a workpiece is generated on the computer using CAD and is then optimized for printing. Based on the generated print data, the workpiece is then created in the build space of the printer from layer-by-layer laser melting using a powdery material. The powder is applied in thin layers, which are smoothed to the set layer thickness between 10 and 100 micrometers by using a variation of a doctor's blade. After the printing, the workpiece is cleaned, removed from the building platform and, if necessary, reworked. Mostly metals or metal alloys -- ranging from stainless steel, aluminum, and titanium to precious metals such as gold -- are processed as powdery pressure media. This essentially determines the properties of the product and represents a cost-intensive element of the manufacturing process.

Standard industrial CW lasers (continuous wave) are used for locally precise melting of the powder, with laser beams being controlled by powerful galvanometer scanners. The type and quality of the exposure, achieved by the laser beam and the resulting melting of the powder, have a major influence on the properties of the workpiece, such as its density and surface quality. The control parameters of the laser also affect the setup speed during 3D printing. Optimized process monitoring and control at the melting point can, therefore, have a positive influence on the quality of the process and the product.

Scientists like Tobias Kolb, Chair of Photonic Technologies of Friedrich-Alexander University in Erlangen-Nuremberg (D), devote their attention to these processes, which take place in rapid succession and in the tightest of spaces. As part of his research project, he uses coaxial process monitoring to investigate the thermal radiation generated when melting the powder.

In addition to the complex theoretical background that needs to be mastered, the instrumental use in the laboratory is considerable. There, coaxially integrated high-speed cameras capture the thermal radiation emitted during the melting of the powder by using the optics of the laser.

"With high-speed cameras we obtain a high temporal and spatial resolution and can draw conclusions about process fluctuations, surface roughness in the process or splashes in the powder bed," explains Kolb.

The studies are conducted by using EoSens® CL CMOS cameras from Mikrotron that enable the retrieving of data on the size and shape of the weld pool and on the intensity distribution of the thermal radiation. In the optical system, there is a dichroic mirror that transmits thermal radiation at a wavelength range of 700 to 950 nanometers to the camera sensor. Since the process requires a minimum of 500 mm/sec scanning speed to over 1,000 mm/sec, a recording frequency of more than 10 kHz is necessary. This is the only way to achieve the required high spatial resolution.

Kolb describes the particular requirements concerning the cameras as follows: "To obtain a resolution in the order of magnitude of the weld pool (100 micrometers), a recording frequency of 10- 15 kHz is required. With a macro-optic, we focus on the weld pool and observe the process with the sensor's recording area reduced to 100 x 100 pixels in order to achieve this high recording frequency."

The result is an enormous data volume providing information about the weld pool. This data volume must be processed in the shortest possible time. Therefore, the signals delivered by the image sensor are pre-evaluated with FPGA (Field Programmable Gate Array). A vector is generated from each camera image, which describes the properties of the image. This information is assigned to an exact spatial position based on the data from the scanner system. From this, images of the thermal radiation are generated layer by layer, before being analyzed.

"We are working on the further development of an image processing software to evaluate this data," adds Kolb. "In the future, this could result in a controlled process, where defects can be detected during printing and then compensated for in the subsequent layers through laser polishing or other methods."

Modern high-speed cameras from Mikrotron can deliver what is needed for optimized process analysis in Selective Laser Melting (SLM), Direct Metal Laser Sintering (DMLS) or Selective Laser Sintering (SLS). Thanks to the rapid process analysis, laser welding, soldering and drilling with lasers used to manufacture modern products based on innovative technologies and materials could also be improved in a comparable way.

Workpieces produced with laser-based manufacturing methods are becoming increasingly complex, light and robust. They will soon be indispensable in every automobile and aircraft, as well as in countless other products ranging from medical technology to high-quality consumer goods.

@mikrotron #PAuto #Pharma  

Video for manufacturing analysis & troubleshooting.

High-speed video capture helps engineers troubleshoot manufacturing processes, and assists researchers in analyzing fast acting events. However, traditional large-format high-speed cameras quickly run out of internal storage, delaying work while data is being transferred.

Mikrotron has solved that problem with its MotionBLITZ CVR recording system that combines an EoSens 4MP CoaXPress color camera remotely connected to an industrial-grade DVR. The MotionBLITZ CVR is capable of recording video sequences of up to 12 seconds at 560 fps and 2,336 x 1,728 pixel resolution directly into RAM. As the result of the fast download of the RAM into the internal RAID drive, the recorder is reset in under four minutes and ready for use. Exceptionally flexible, the camera and recorder system can be configured to record up to 35,000 fps in smaller image formats, as well. The detachable camera can be easily fitted into tight spaces, observing the event where it is happening up to 20 meters away.

By using the MotionBLITZ CVR, every critical detail can be captured, identified and eliminated if necessary, during event analysis in industries such as automotive, electronics, pharmaceutical, packaging, robotics, and factory automation, helping plant managers gain new research insights and decision-making visibility. For example, individual production steps of highly complex, extremely fast production processes can be recorded at resolutions down to the micrometer scale and precisely analyzed for flaws.

The system's recording station features 2TB storage capacity, and an onboard ring buffer that allows buffering of triggered events up to 12 seconds at full resolution and full speed. MotionBLITZ Director2 imaging software, which is included, has recording and triggering settings, viewing and editing functions, image correction, market and comment functions, image data export, and multiple sync and trigger options.

#PAuto #Manufacturing @mikrotron