15 Nov 2018
Laser AM processing and systems at the heart of new industrial techniques demonstrated in this week's Frankfurt expo.Formnext trade fair, in Frankfurt, Germany, no fewer than 550 institutes and companies are presenting their latest designs and product developments for industrial tooling, production, quality management and measurement.
Industrial laser and machine tool developer Trumpf is showcasing its latest 3D printer and processes. The firm will demonstrate how its TruPrint 5000 system, preheated to 500°C, prints high-carbon steel or titanium alloy components that do not crack or severely warp.
"Tool and mold makers can now easily print forming tools, punches and dies. Previously, without preheating, that was not possible," said Tobias Baur, Trumpf General Manager, Additive Manufacturing. The company also has a new green laser with pulse function, enabling pure copper and precious metals to be processed in a 3D printer for the first time.
"This makes it attractive for use in mechanical and plant engineering, as pure copper can be used to print particularly conductive inductors and heat exchangers," said Baur. The green laser also offers great potential for printing gold in the jewelry industry, enabling individual unique pieces to be produced on demand, while saving expensive material.
In 3D printing, tool and mold makers often work with carbon tool steel 1.2343, an extremely hard and wear-resistant material that dissipates heat particularly well. To date, however, it couldn't be processed in 3D printers because the components crack during printing.
Trumpf’s Baur explained how his laser materials processing machine overcomes this: “The laser beam melts the component surface, which subsequently cools back down to room temperature. The components weren't able to withstand this temperature drop, and cracks formed. That's why the substrate plate of the TruPrint 5000 3D printer can be preheated to 500 degrees Celsius. This lessens the temperature drop following laser melting," he said.
Preheating also offers major advantages for prostheses and implants produced using additive manufacturing. "When the ambient temperature drops too sharply, the parts warp and we have to rework them. In addition, we often require support structures that are difficult to set up and take down," Baur added.
At this week’s Formnext, Trumpf used a green laser with pulse function to demonstrate for the first time how to 3D-print pure copper and other precious metals. To achieve this, the developers connected the new TruDisk 1020 disk laser to the TruPrint 1000 3D printer.
"Conventional systems use an infrared laser as the beam source, but its wavelength is too long and it can't weld highly reflective materials such as copper and gold. This can be done with laser light in the green wavelength spectrum," said Thomas Fehn, Trumpf’s General Manager Additive Manufacturing. According to Fehn, this process will open up new possibilities for 3D printing, for example in the electronics and automotive industries.
Optomec shows 5-axis hybrid betal printing
AM systems developer Optomec presents its latest hybrid machine tool system that enables larger build volumes and higher power capabilities for metal additive and hybrid manufacture.
The LENS 860 Hybrid Controlled Atmosphere System is the latest addition to its Machine Tool Series, which integrates Optomec’s LENS 3D metal printing technology with vertical machining platforms resulting in what the company describes as “the industry’s first hybrid controlled atmosphere system”.
“We are excited to be at Formnext with our biggest, most powerful system for printing high-value metal parts,” commented Urs Berger, managing director of Optomec’s new headquarters for EMEA in Dübendorf, Switzerland. “The LENS 860 has the capabilities and economics to make metal additive manufacturing more accessible for a wider range of industrial applications.”
In its booth (Hall 3.1 Stand J10), Optomec is running demonstrations showcasing simultaneous five-axis metal printing and a single tool path for both additive and subtractive processes on the same machine. With an 860 x 600 x 610mm work envelope, the LENS 860 Hybrid CA system offers a much larger build volume than other systems in the Machine Tool Series; furthermore its sealed workpiece environment allows the processing reactive metals, such as titanium.
All systems in the Machine Tool Series incorporate Optomec’s LENS 3D Metal Printing technology, which uses a high-power laser (400W to 3kW) to fuse powdered metals into fully dense, three-dimensional structures. These systems have a starting price of $250,000.
At Formnext 2018, in cooperation with the Chair for Technology of Optical Systems at Aachen University, the Fraunhofer Institute for Laser Technology is showing a new process in which the component in the powder bed is heated with laser diodes. As a result, distortion can be reduced, taller parts generated and new materials used.
This process – laser powder bed fusion, also known as laser beam melting – can build parts with less thermally-induced stress and less distortion than conventional process technology.
The internal stresses are caused by temperature gradients in the generated component: In the laser spot, temperatures above the melting point prevail, while the rest of the component cools rapidly. Depending on the geometry and material, this temperature gradient can even lead to cracks in the material. To avoid this, the component is usually heated from below via the substrate plate. However, that's not enough, especially with taller structures.
As part of Aachen’s Digital Photonic Production DPP research campus, a funding initiative of the German Federal Ministry of Education and Research, the experts from Fraunhofer ILT and RWTH TOS Chair are working together with their partner Philips Photonics to develop solutions for this task. In the joint project DPP Nano, they have developed a set-up in which the component is heated from above.
For this purpose, an array of six vertical-cavity surface-emitting laser bars with 400W each is installed in the process chamber. With infrared radiation at 808nm, this array can heat the device from the top to several hundred degrees Celsius during the building process. The bars can be controlled individually so that sequences of different patterns are possible. The process is monitored with an infrared camera.
In one experiment, the Aachen engineers have constructed parts of Inconel 718 and demonstrated significantly reduced distortion. The component was heated up to 500°C. The VCSEL heating reduces the thermal gradient, thus also the stresses, making it possible to produce taller parts. But even more interesting are the possibilities that arise for particularly difficult materials; soon, components made of titanium aluminides are to be produced. For this, the component will be heated to 900°C.
Another Formnext 2018 presentation on the “future of 3D printing” is the Fraunhofer Focus Project FutureAM, which involves six Fraunhofer institutes. For example, scientists from Fraunhofer ILT have developed a new processing head for Laser Powder Bed Fusion, which can generate large metal components additively up to ten times faster than conventional LPBF systems.
Not only suitable for coating rotationally symmetrical components: The EHLA process is now being further developed for additive manufacturing of 3D geometries.
“We are focusing on the complete process chain from order processing through design and simulation to production in the machines," said Christian Tenbrock, research associate at Fraunhofer ILT and project coordinator of futureAM.
For the past year, the research platform has been developing digital process chains, scalable and robust AM processes, system technology and automation as well as tailor-made AM materials. The researchers are currently implementing the configuration, and in 2019 the first practical trials will start with this prototype system.
In addition, the Aachen scientists are working on new methods for monitoring the 3D printing of metals in order to increase process robustness. “With structure-borne sensors in the construction platform, we want to detect critical events in the future, such as when support structures tear off,” said Tenbrock.
Ultrasonic sensors are also used to analyze airborne sound in order to determine component quality. Research into laser-based ultrasound measurement will go a step further in the future: a pulsed laser will induce structure-borne noise in the component, which in turn will be detected by a laser vibrometer.
The Fraunhofer-Gesellschaft has called futureAM into being to systematically develop the additive manufacturing of metallic components further. Six institutes have entered into a strategic project partnership in the field of additive manufacturing:
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