To ensure technological leadership, the six institutes of futureAM will systematically develop additive manufacturing in four fields of activity, each coordinated by one institute:
The lighthouse project has set itself ambitious goals within its four fields of activity: for example, novel software for automated AM component identification and optimization, a scalable LPBF (Laser Powder Bed Fusion) plant concept increasing productivity (by a factor > 10), a process and system technology for generating spatially resolved, customized multi-material properties and an autonomous manufacturing cell for the post-treatment of AM components.
The cooperation platform has not only been created through intensive cooperation in and between the individual fields of activity, but in particular through the establishment of a “Virtual Lab”. For this purpose, all partners will participate in developing technology demonstrators.
Field 2 focuses on the development of scalable and robust AM processes. The vertical process chain lacks new concepts for the scalability of AM processes in terms of build-up rate and component size (especially for the Laser Powder Bed Fusion LPBF, also known as Selective Laser Melting SLM), in order to achieve cost-effectiveness even for larger quantities. In addition, direct fault detection during the manufacturing process is a previously unsolved problem.
As part of futureAM, the scientists at the Fraunhofer ILT have developed a machine concept for the LPBF of large metal components. A new laser head was developed for the laboratory system with a very large, effectively usable build volume (1000 mm x 800 mm x 500 mm), which increases productivity by a factor of 10 compared to conventional LPBF systems.
A multi-award-winning technology is involved in “Extreme High-Speed Laser Material Deposition (EHLA)”, which can coat, repair or additively manufacture components in a particularly economical and environmentally friendly way. This technology has already proven its worth by applying thin protective layers, for example on meter-long offshore cylinders at high speeds. So far, EHLA has been used only in rotationally symmetric parts. The next step is to create 3D geometries. For this purpose, a prototype machine is being built in Aachen, where the workpiece is moved in a highly dynamic manner with up to five times the gravitational acceleration under the EHLA powder nozzle.
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, critical events, such as when support structures tear off, are detected in the future. 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. Tiny pores on the spot should be found in order to be able to intervene immediately. The in-situ measurement process should, for example, make it possible to rework problem areas with another exposure sequence.
The increase in process robustness is achieved by integrating quality assurance tools in (hybrid) production systems, e.g. for geometric recording and in-situ process analysis. In addition to inline measurement and quality assurance, the identification of a robust process window for various materials, machines, beam sources etc. is indispensable for area-wide industrial use.
The development of a process for volume build-up with Laser Material Deposition LMD with extreme build-up rates aims at reducing the €/cm³ price of the built-up material.
The aim is to develop an inline quality assurance system for powders using measurement methods positioned in the immediate vicinity of the manufacturing process. The idea behind this research arose from the knowledge that powders, especially their size distribution, are asymmetrically distributed by vibration during transport. Accordingly, it must be ensured that the production systems are continuously supplied with the same powder quality. The goal is achieved by simulating the transport behaviour with subsequent powder control. IFAM Bremen has developed a test bench for this purpose and tests various materials.
High powder prices result in high production costs. Most LPBF processes, however, require spherical powder for the perfect production of components. The aim of developing and testing modification processes that open up powders from alternative manufacturing routes for AM application is to increase competitiveness compared with conventional production methods. Various modification methods are being tested at the IFAM to support the flowability of the powders
In the futureAM research area “Materials”, the Fraunhofer scientists are focusing on two principal objectives:
In order to push the Additive Manufacturing of advanced materials, the researchers investigate the relationships between process parameters, process conditions and material properties. Nickel-based alloys are regarded as difficult to non-weldable. A stable welding process can only be achieved if all parameters and boundary conditions, such as temperature, material, feed rate etc. are precisely adjusted. All influencing parameters must be adjusted exactly to find the correct recipe. In addition, during the research process huge amounts of data are generated (“big data”), causing difficulties for humans in understanding them. In order to nevertheless identify hidden correlations in the signal floods, the Fraunhofer experts use advanced methods of “artificial intelligence” (AI) and “machine learning”. Over time, these machines learn to decide independently. For example, they detect for themselves whether a slight rise in temperature during the welding process can be tolerated or whether they must take immediate countermeasures before a component has to be classified as defect.
The Fraunhofer scientists succeeded in defect-free processing MAR-M 247, the nickel-based alloy considered to be non-weldable. For this purpose, they used the laser deposition welding process. The processing turned out challenging as the usable process windows are very small. For example, these alloys crack quickly when during solidification. An induction system developed at Fraunhofer IWS was used, enabling the process conditions to be tailored to the respective application. In order to meet the thermal conditions, a thorough understanding of the process is necessary in order to ensure that the exact application can be created after detailed series of tests.
An additional insight in this context is that a component can be tailored from various materials without subsequent joining processes. The Fraunhofer researchers succeeded in producing a graded material transition from Inconel 718 to Merl 72. Different features can not only be realized, but also different materials can be placed in the component exactly where they are best suited for the later application. The futureAM researchers thus opened the door to new functionalities and applications, which cannot be developed with conventional designs. These developments enhance possibilities for manufacturing high performance components such as lighter and high temperature resistant turbine blades.
Currently, relatively few materials are commercially available. Steels that have not yet been processed are to be produced by additive powder mixing. A “modular material system” is being developed for this purpose. This contains master alloys, element powders, but also pre-alloyed steels to which other powders can be added in order to adapt certain properties.
Research topic 4 deals with the development of systems engineering that allows automated manufacturing of functionally integrated components using powder bed based additive manufacturing processes and autonomous reworking of additively manufactured components.
Using automated component integration in laser beam melting can reduce manual process steps during the manufacturing process; it can avoid process interruptions, thus improving the reproducibility of component properties. An additional functionality of the deposited structures lies in multi-material manufacturing that opens up challenging fields of application by locally adapting the material properties.
A manufacturing cell is developed in order to demonstrate the autonomous mechanical reworking of additively manufactured components. It is based on a flexible machine concept that configures itself according to the process requirements. This demonstrator comprises hardware modules for handling, powder removal, removal of support structures, for mechanical reworking and optical component measuring.
Fraunhofer IWU has developed a new concept of combining the geometric flexibility of powder bed based processes and multi-material manufacturing. The prerequisites of the system technology were created in the project by installing a handling system with dispenser and suction module for local powder removal. In the installation space of the laser beam melting plant the powder is first removed from the cavities in the solidified area of the component. Then a dispenser locally adds a structure by using a paste. The project comprises the development of hardening and sintering processes that enable the defined generation of desired material properties such as electrical conductivity or insulation.
The system technology for multi-material manufacturing developed at Fraunhofer IWU is complemented by a gripper in order to integrate semi-finished products, sensors or actuators into a component without opening up the laser beam melting plant. For demonstrating the functionality, a glass-encapsulated RFID transponder is used, which is placed into a cavity directly below the surface of the manufactured component and will be tightly enclosed in the component during the subsequent construction process. This transponder is utilized to save and read information about the manufacturing process or about component properties. In addition, this data can also be complemented later during operation.
Researchers at Fraunhofer IWU developed the modular concept of an adaptable cell for autonomous reworking of additively manufactured components, which makes it possible to use the cell in flexibly demonstrating this technology using various components and approaches for manufacturing products of batch size 1. Additional components can be integrated quickly and flexibly into the process chain, which is also supported by the developed control concept.
Due to the high geometric variance of the additively manufactured components, a toolbox is used containing various strategies for grippers and clamping. The selection of a suitable strategy is based on the geometry of the component, the planned type of processing and the number of pieces to be realized.
Machining with industrial robots requires high structural stiffness and exact path planning for achieving high manufacturing quality. Using an analysis model, areas in the working space are identified where the stiffness is ideal for machining. Furthermore, the model makes it possible to use the process control to compensate for false positions of the tool.
Optical component measurement is the first step for reworking the component. The acquired point cloud is transferred to a 3D model of the actual geometry. Path planning and tool selection for robot-based reworking take place based on the deviations of the nominal geometry from the component design. After reworking is completed, the component is measured again. This process is repeated until the determined component quality is reached.
The prerequisite for autonomous reworking of additively manufactured components consists of the safe identification of the component in each process step. This is the only way to link product information to process parameters and to track the process chain for each component. Fraunhofer IWU develops measuring processes for real-time detection of defined cavities in the near-surface area of the component, e.g. using QR codes. Developing the algorithms required for real-time reading of the information is an essential part of the research activities.
futureAM – Next Generation Additive Manufacturing