# The Current State of Research of Wire Arc Additive Manufacturing (WAAM): A Review
## 6 Anticipated Further Research  
Additive manufacturing technologies are fundamentally changing the way products are developed and manufactured. The great potential of additive manufacturing technologies has been demonstrated in numerous research studies for various application areas. It has been shown that economic use requires high material deposition rates and an end-to-end process chain from component design to the manufacturing process. Arc-based additive manufacturing processes are also suitable for the production of complex components with homogeneous or locally adapted material properties, as presented in this review. Although this process is widely used, the full potential of targeted heat and material transfer for the locally adapted properties of multi-material systems in components has not yet been tapped. Therefore, this potential should be further explored and complemented by new methods and processes for the development and fabrication of completely new components. The basis for this is the investigation and description of the process-specific interactions between product development, process technology, process control and process simulation. This can lead to material-efficient manufacturing of complex and highly stressed structural components and a new dimension in design freedom and functional integration. For this purpose, on the one hand, process-specific knowledge for wire and arc additive manufacturing (WAAM) is required, and on the other hand, generally applicable methods and processes for the integrated development and flexible process control of additively manufactured, monolithic components are to be researched and tested. In order to research the methods, technological principles and processes required for this, interdisciplinary cooperation is necessary (e.g., between product development, production engineering, materials science and metrology, as well as control engineering and computer science). The aim of further research should be the development of methods and processes for a continuous and highly automated production process for wire and arc additive-manufactured multi-material components with partially adjusted properties (e.g., strength, toughness and wear resistance) for the occurring operating loads via multi-material approaches. For this purpose, it is necessary to link the sub-areas presented in the review to form a holistic approach. The interactions that occur between the manufacturing process, component development and material and component properties should first be fundamentally investigated in order to be able to tap new potentials. The following questions arise from the current state of research and should be investigated in further research work:  
* How can WAAM-compatible components be designed? * What are the boundary conditions for WAAM-compatible components so that they can be manufactured? * What are the local system properties to realize multi-material components that are designed for operation under different types of loads (e.g., wear resistance and fatigue strength)? * Which path planning algorithms allow the use of the full potential of WAAM? * Which methods and procedures of process monitoring, control and information processing are suitable to enable a local adjustment of material properties in a process-reliable and reproducible way? * What are the interrelationships between the process setting variables, path planning, other process boundary conditions and the achievable material properties? * Which multi-material systems and material-dependent manufacturing framework conditions are suitable for WAAM? * Which modeling methods and procedures enable computer-aided FEM-based computational prediction of the properties for components with locally adjusted properties?