Additive manufacturing

Additive manufacturing (DED, WAAM)

Additive manufacturing with arc welding processes such as MSG, TIG or plasma processes represents a resource-efficient and economical option for the production of complex 3D components. The use of filler materials in wire or powder form enables buildup rates of several kg/h, which makes it possible to address the production of large-volume components. The work at the Department of Production Engineering is mainly concerned with the control of energy input and the resulting process-material interactions. The WAAM process (Wire Arc Additive Manufacturing) can be used to process almost all metallic materials in the form of wire.

Path planning and build-up strategies

In additive manufacturing, three-dimensional structures with varying complexity are manufactured. For the production of the components it is necessary a to create a path planning for the weld beads to be applied. The component is in vertical plane sections broken down (engl: sliced), in order to subsequently applied layer by layer using the appropriate manufacturing process. The strategy not only takes into account the geometric conditions of the component, but also the takes into account but also takes into account the heat transfer within the part. This can influence both productivity and the mechanical-technological properties.

Multimaterial structures and hybrid designs

Additive manufacturing with arc welding processes enables the targeted use of different materials within a component. The layer-by-layer build-up process allows specific alloy systems to be placed at functionally relevant positions within the workpiece. Thus, for example, multi-material structures with integrated wear protection or ductile intermediate layers to absorb residual stresses or reduce distortion are implemented at the Production Engineering department.

Lightweight construction and topology optimization

Filigree, material-saving, strength- and stiffness-adapted load-bearing structures made of metal are becoming increasingly important. Through such structures, it is not only possible to incorporate individual aesthetics into buildings or to create iconic architectural masterpieces, but also to generate stress-optimized technical solutions based on nature (bionics). The motivation to produce a lightweight structure with maximum stability is often paired with the desire for minimal and adapted material use as well as low manufacturing costs.

Process-material interaction

Metallic mixed compounds

Metallic mixed joints consist of materials that are considered suitable for welding only to a limited extent or not at all, but whose different properties in combination enable numerous advantages in the fields of lightweight construction, electromobility and other areas of research. Examples include the mixed compounds aluminum-copper, aluminum-titanium or steel-aluminum. Research activities focus on the modification of processes and system technology, on the one hand for adapted temperature control and control of diffusion between the materials involved, and on the other hand with regard to the implementation of control strategies in pulsed laser beam welding.

Interaction process metallurgy

The interrelationship between process and metallurgy can be influenced, among other things, by the targeted adjustment of the cooling/setting conditions and the melt pool convection. The temperature-time regime and the effective strains can be specifically influenced by pulse modulation in the laser welding process and the use of adapted intensity distributions. These strategies enable, among other things, hot crack-free welding of aluminum alloys (EN AW 6xxx) without filler metal or laser cladding of nickel-base superalloys of the same type.

Hardfacing of wear and corrosion protection coatings

Hardfacing describes a form of coating and is used to armor, plate or buffer components. In particular, the refurbishment of worn components with wear-protective or corrosion-resistant alloy systems represents an economical way of extending the product life cycle of stressed components. The metal inert gas and plasma powder cladding processes used in the Production Engineering department are plasma powder deposition welding are characterized by high productivity and very good automation. The research focus is on the correlation between process control and coating properties, such as wear resistance, using different alloy systems.

Welding and thermal joining

Laser beam welding

Laser beam welding is widely used in industrial processes and offers significant advantages over competing processes due to its high energy density and non-contact energy input. The work of the Production Technology Group focuses on process engineering, systems engineering, and materials science to develop innovative approaches to increase processing speed and weld quality, as well as novel strategies for processing hybrid material combinations. 

Thermal joining of metals with plastics

Thermal joining of metals with thermoplastics is a novel process that can be performed by laser and resistance joining. Applications range from the automotive industry to mechanical engineering and white goods. Thermal joining enables the direct joining of a hybrid composite without additional joining elements or adhesives and allows the simultaneous use of both materials for the realization of optimized component structures. The focus of the work is on the link between process design and the resulting material properties, aging and fatigue behavior, as well as fundamental considerations of the interface and bonding mechanism. 

Joint welding

Arc welding processes - such as gas-shielded metal arc welding - are widely used in many areas, such as automotive and power plant construction. Research at the Department of Production Engineering focuses on the development of joining strategies for highly productive welding using hot wires, but also for filigree welded joints on thin sheets with thicknesses of less than 1 mm, which are some of the most demanding tasks in joining joining technology with arc belong to.

Modeling and simulation

Numerical weld structure simulation

The weld structure simulation is used at the department of production engineering as a process-accompanying tool for the clarification of technical welding questions such as microstructural transformationsresidual stresses or component distortion.. The welding simulation on the numerical solution of a model and is validated by comparison with experimental tests. The comparison of different process variations, materials or clamping conditions makes it possible to an optimized approach for the selected welding task. Weld structure simulation is used in addition to additive manufacturing welding, it is also used in joint and buildup welding.

SPH method

The SPH method is a modern approach to the simulation of liquid or gas flows and also enables the determination of solid deformations, which occur, for example, during friction stir welding. The work of the Production Engineering department deals with the modeling of the tool and the materials in order to obtain statements on the mixing of materials by the tool or on the wear of the tool.

Process and structure simulation

The simulation of laser material processing processes depends on several influencing variables, including the intensity distribution of the laser beam and the material, which significantly affect the processing result.The use of modeling and simulation of material processing provides a deep understanding of the process and ranges from analytical considerations to numerical simulation of thermomechanical models to multiphase process simulation of laser beam deep penetration welding. 

Topology optimization

One area of structural optimization is topology optimization. Numerical calculation methods are used to generate design proposals for stresses and evaluate them in terms of utilization. This allows material-reduced and load-compatible structures to be determined. For implementation by the WAAM additive manufacturing process, process-specific boundary conditions must be taken into account when performing topology optimization.

AI and digitalization in production

AI-based process analysis

Artificial intelligence is becoming established in many areas of life. The large number of sensors and data that can be integrated or recorded in the manufacturing process provides an ideal basis for using artificial intelligence in manufacturing technology. This means that process changes can be detected very quickly on the basis of the data and necessary measures can be derived. In addition to extensive data, suitable models must also be selected and trained.

Multimodal sensor technology for joining and welding technology

The use of multimodal sensor technology enables novel approaches to process monitoring and control in the field of joining and welding technology as well as surface processing.With the help of modern signal processing methods and approaches of artificial intelligence systems for the automated acquisition, processing and linking of corresponding data streams are being developed at the Department of Production Engineering. This approach offers significant potential for the development of real-time process monitoring systems for various applications, including welding, thermal joining technology and additive manufacturing, as well as the possibility of controlling processes, e.g. for cleaning surfaces.