Arnold invests in research

Powder deposition welding in an inert gas atmosphere

In addition to its regular business activities, KH Arnold Maschinenfabrik GmbH & Co. KG also actively participates in research projects in order to constantly expand the company's know-how and to continue to offer the industry solutions for its requirements in the future. As part of the BMBF's announcement “Line integration of additive manufacturing processes”, a laser welding system for powder deposition welding in an inert gas atmosphere was developed and put into operation in collaboration with other project partners.

Powder deposition welding is currently very much in the focus of the industry. Customers are currently already using systems in the area of ​​coating components or in 3D printing. However, the use of these systems is currently limited to the use of oxygen- and air-stable powders. However, in order to be able to use powders that do not have these properties, a system is required that can be sensed with a protective gas for this purpose and can maintain the necessary limit values ​​for water and oxygen throughout the application process. As part of the BMBF's announcement “Line integration of additive manufacturing processes”, KH Arnold Maschinenfabrik GmbH & Co. KG, together with a consortium, set itself the task of solving exactly this problem.

Figure 1: Nozzle head for powder deposition welding

The focus of the requirements for a powder deposition welding system for air-unstable powders is on the tightness of the interior of the system. Only if a high level of tightness is guaranteed can the limit values ​​in the protective gas atmosphere be maintained. The challenge of developing a machine concept suitable for this project was primarily to design the machine in such a way that as little gas exchange as possible takes place at the connecting lines. Connection lines that could not be welded were sealed by intelligently incorporating seals and screw connections into the machine design.
Diffusion-tight connectors and plugs have also contributed to this task. Since diffusion can never be prevented even with the best concept, a gas processing system was connected to ensure that the protective gas atmosphere set is maintained for as long as it is needed.

Figure 2: System for powder deposition welding in an inert gas atmosphere

Other requirements for the facility included radiation safety. In addition to the solid steel construction, radiation protection windows made it possible to take a look into the system during operation. To prevent radiation from escaping the work gloves, they can be closed from the inside. Furthermore, the introduction or removal of components was an important topic. In order not to have to open the system every time, a lock was installed through which this can be accomplished. This ensures that the protective gas atmosphere is maintained inside the system. In order not to require an unnecessarily large amount of protective gas to operate the system, the system was optimized as much as possible during construction in order to make the interior space as small as possible and still achieve the required travel distances.

Figure 3: Flange manufactured with LMD after the powder application process (left) and post-machining (right)

After all hurdles to implementing a successful machine concept had been overcome, we provided our project partners with a functional machine on which the powder application process of an air-unstable powder could be successfully modeled, thus fulfilling the consortium's project goal.

Project partners:
Fraunhofer Institute for Materials and Beam Technology IWS
SKM Informatik GmbH
IfWW of the Technical University of Dresden
PFW Aerospace GmbH