Simon Merkt

Mechanical response of TiAl6V4 lattice structures manufactured by selective laser melting in quasistatic and dynamic compression tests

This paper focusses on the investigation of the mechanical properties of lattice structures manufactured by selective laser melting using contour-hatch scan strategy. The motivation for this research is the systematic investigation of the elastic and plastic deformation of TiAl6V4 at different strain rates. To investigate the influence of the strain rate on the mechanical response (e.g., energy absorption) of TiAl6V4 structures, compression tests on TiAl6V4-lattice structures with different strain rates are carried out to determine the mechanical response from the resulting stress-strain curves. Results are compared to the mechanical response of stainless steel lattice structures (316L). It is shown that heat-treated TiAl6V4 specimens have a larger breaking strain and a lower drop of stress after failure initiation. Main finding is that TiAl6V4 lattice structures show brittle behavior and low energy absorption capabilities compared to the ductile behaving 316L lattice structures. For larger strain rates, ultimate tensile strength of TiAl6V4 structures is more than 20% higher compared to lower strain rates due to cold work hardening.

Scalability of the mechanical properties of selective laser melting produced micro-struts

Selective laser melting (SLM) is a manufacturing process that builds up metallic or ceramic parts layer by layer directly from 3D-computer-aided design data, offering, for example, the advantage of imposing little restrictions in terms of geometric complexity. One of the main challenges of the SLM process is to improve its efficiency by increasing the build rate of the process and thereby decreasing time and cost. One way of achieving this is increasing the applied laser power and beam diameter, thereby melting more volume in a shorter period of time. Another option of improving efficiency is reducing the volume of the material which has to be melted, made possible by the aforementioned limitless geometric freedom offered by the SLM process. Hereby, one can generate hollow parts for better exploitation and adaption of the volume to specific load cases. Large volumes can be replaced by lattice structures with a certain volume fraction, saving weight and production time by maintaining the stiffness of the s...

Geometric complexity analysis in an integrative technology evaluation model (ITEM) for selective laser melting (SLM)

Selective laser melting (SLM) is becoming an economically viable choice for manufacturing complex serial parts. This paper focuses on a geometric complexity analysis as part of the integrative technology evaluation model (ITEM) presented here. In contrast to conventional evaluation methodologies, the ITEM considers interactions between product and process innovations generated by SLM. The evaluation of manufacturing processes that compete with SLM is the main goal of ITEM. The paper includes a complexity analysis of a test part from Festo AG. The paper closes with a discussion of how the expanded design freedom of SLM can be used to improve company operations, and how the complexity analysis presented here can be seen as a starting point for feature-based complexity analysis.

Integrative Technology Evaluation Model (ITEM) for Selective Laser Melting (SLM)

This paper focuses on the evaluation of manufacturing processes that are competing with Selective Laser Melting (SLM). In 3D-part production of serial parts SLM is starting to be an economic choice for manufacturing. An integrated technology evaluation model (ITEM) is presented that helps decision makers to determine the potential of SLM while comparing with conventional manufacturing technologies. In contrast to conventional evaluation methodologies the ITEM considers interactions between product and process innovations generated by SLM. The paper closes with a technical and economical evaluation of a test part from Festo AG to validate two important parts of the ITEM.

Opportunities and challenges of profile extrusion dies produced by additive manufacturing processes

The design and manufacture of profile extrusion dies is characterised by costly running-in trials. Significant cost and time savings can be achieved by replacing the experimental running-in trials by virtual ones. A simulative optimisation, however, often leads to complex, free-formed flow channels. A feasible manufacture of such dies is only possible with additive manufacturing processes such as the Selective Laser Melting (SLM). Against this background, the manufacture of profile extrusion dies by SLM is investigated. A major challenge is to ensure a specific surface quality of the extruded plastics profiles. The roughness of SLM surfaces does not meet the high demands that are placed on the surface quality of extrusion dies. Therefore, in case of the SLM die a concept for the surface finishing of the flow channel is required, which can be applied to arbitrarily shaped geometries. For this purpose, plastics profiles are extruded both with a conventionally and an additively manufactured die. In case of the SLM die only the die land of the flow channel was reworked by polishing. The comparison of PP profile surfaces shows that the SLM die with polished die land leads to the same surface quality of the extruded profile as the conventional die (Ra ≈ l μm). Another important task in the design of profile dies by SLM is the optimisation of the die topology. The efficiency of the SLM process largely depends on the volume of the part being produced. To ensure the highest possible efficiency, it is necessary to adapt the die geometry to its mechanical loads and minimise its mass. For this purpose, the internal pressure in the die was numerically calculated and used for a first optimisation of the die topology. The optimisation, however, leads to a free-formed outer die wall so that the die cannot be tempered with heating tapes anymore. This problem is solved by using the high potential of SLM for functional integration and integrating contour adapted tempering channels into the extrusion die.The design and manufacture of profile extrusion dies is characterised by costly running-in trials. Significant cost and time savings can be achieved by replacing the experimental running-in trials by virtual ones. A simulative optimisation, however, often leads to complex, free-formed flow channels. A feasible manufacture of such dies is only possible with additive manufacturing processes such as the Selective Laser Melting (SLM). Against this background, the manufacture of profile extrusion dies by SLM is investigated. A major challenge is to ensure a specific surface quality of the extruded plastics profiles. The roughness of SLM surfaces does not meet the high demands that are placed on the surface quality of extrusion dies. Therefore, in case of the SLM die a concept for the surface finishing of the flow channel is required, which can be applied to arbitrarily shaped geometries. For this purpose, plastics profiles are extruded both with a conventionally and an additively manufactured die. In case of t...

Disruptive Innovation Through 3D Printing

Emerging technologies such as 3D Printing or Additive Manufacturing (AM) and especially Selective Laser Melting (SLM) provide great potential for solving the dilemma between scale and scope, i.e. manufacturing products at mass production costs with a maximum fit to customer needs or functional requirements. Because of the technology’s intrinsic advantages such as one-piece-flow capability and almost infinite freedom of design, Additive Manufacturing was recently described as “the manufacturing technology that will change the world”. Due to the complex nature of production systems, the technological potential of AM and particularly SLM can only be realized by a holistic comprehension of the complete value creation chain, especially the interdependency between products and production processes. Therefore, this chapter aims to give an overview on recent research in machine concepts and component design, which experts of the Cluster of Excellence “Integrative production technology for high wage countries” carried out.

Direct, Mold-Less Production Systems

Additive Manufacturing (AM) technologies in general—and in particular, Selective Laser Melting (SLM)—are characterized by a fundamentally different relationship with respect to costs, lot size, and product complexity compared to conventional manufacturing processes. There is no increase of costs for small lot sizes (in contrast to mold-based technologies) and none for shape complexity either (in contrast to subtractive technologies). Thus, only the holistic development of a direct, mold-less production system that takes all relevant interdependencies along the product creation chain into account provides the full economic, ecologic and social benefits of AM technologies in future production. The following six subjects of the product creation chain were examined: (i) New business models and customer willingness to pay for AM parts are revealed. (ii) The Product Production System (PPS) was totally revised regarding the adoption of SLM technology into conventional manufacturing environment. (iii) The SLM manufacturing costs were examined regarding different machine configurations. (iv) A high-power SLM process was developed for enhancing the process productivity. (v) High manganese steel was qualified for the SLM process. (vi) Finally, two lattice structure types and a design methodology for customer parts were developed.