Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

Filters

39
39
Reset filters

Settings
Now showing 1 - 10 of 39
  • Publication
    Numerical investigation into cleanability of support structures produced by powder bed fusion technology
    ( 2022)
    Campana, Giampaolo
    ;
    Uhlmann, Eckart
    ;
    Mele, Mattia
    ;
    Raffaelli, Luca
    ;
    Bergmann, André
    ;
    Kochan, Jaroslaw
    ;
    Polte, Julian
    Purpose: Support structures used in laser powder bed fusion are often difficult to clean from unsintered powder at the end of the process. This issue can be significantly reduced through a proper design of these auxiliary structures. This paper aims to investigate preliminary the airflow within differently oriented support structures and to provide design guidelines to enhance their cleanability, especially the depowdering of them. Design/methodology/approach: This study investigates the cleanability of support structures in powder bed fusion technology. Digital models of cleaning operations were designed through computer-aided engineering systems. Simulations of the airflow running into the powder entrapped within the thin walls of auxiliary supports were implemented by computational fluid dynamics. This approach was applied to a set of randomly generated geometrical configurations to determine the air turbulence intensity depending on their design. Findings: The resul ts, which are based on the assumption that a relationship exists between turbulence and powder removal effectiveness, demonstrated that the maximum cleanability is obtainable through specific relative rotations between consecutive support structures. Furthermore, it was possible to highlight the considerable influence of the auxiliary structures next to the fluid inlet. These relevant findings establish optimal design rules for the cleanability of parts manufactured by powder bed fusion processes. Originality/value: This study presents a preliminary investigation into the cleanability of support structures in laser powder bed fusion, which has not been addressed by previous literature. The results allow for a better understanding of the fluid dynamics during cleaning operations. New guidelines to enhance the cleanability of support structures are provided based on the results of simulations.
  • Publication
    Additive manufacturing of precision cemented carbide parts
    ( 2021)
    Polte, Julian
    ;
    Polte, Mitchel
    ;
    Lahoda, Christian
    ;
    Hocke, Toni
    ;
    Uhlmann, Eckart
    Cemented carbide parts are commonly used as wear resistance components in a broad range of industry, e.g. for forming, mould making and matrices. At state of the art the machining of precision cemented carbide components by milling is strongly limited due to excessive tool wear and long machining times. Promising approaches for precision machining of cemented carbide components are dedicated cutting tool coatings, new cutting materials like binderless polycrystalline diamond and ultrasonic-assisted machining. Nevertheless, for all these approaches the components need to be machined of monolithic materials. The new approach addresses an innovative manufacturing process chain composed of near net shape Additive Manufacturing followed by a precision finishing process. Within this investigations for the manufacturing of precision cemented carbide parts, cemented carbide with a cobalt content of 17 % and a grain size in a range of 23 µm ⤠gs ⤠40 µm were used. As Addit ive Manufacturing technology laser powder bed fusion was used. Diamond slide burnishing and immersed tumbling were investigated as finishing technologies. Based on the investigations, a dedicated process chain for the manufacturing of precision cemented carbide parts could be realised. The findings show that the developed process chain composed of near net shape Additive Manufacturing and the finishing process diamond slide burnishing enables the manufacturing of precision cemented carbide parts with a geometrical accuracy of ag ⤠10 µm. Due to the finishing process the initial surface roughness after Additive Manufacturing could reduce by Ra = 89 %.
  • Publication
    Effects on part density for a highly productive manufacturing of WC-Co via laser powder bed fusion
    ( 2021)
    Polte, Julian
    ;
    Neuwald, Tobias
    ;
    Gordei, Anzhelika
    ;
    Kersting, Robert
    ;
    Uhlmann, Eckart
    The additive manufacturing of parts made from difficult-to-weld materials through the usage of preheating temperatures of up to Î0 ⤠500 °C is enabled by newest L-PBF machine tools, such as the RenAM 500Q HT from the company RENISHAW PLC, Wottun-under-Edge, UK. This work aims to delevop processing parameters for the dense and crack-free manufacturing of tungsten-carbide cobalt (WC-Co) via this off-the-shelf machine tool. Therefore the laserpower and scanning speed were varied between 80 W ⤠PL ⤠350 W and 140 mm/s ⤠vS ⤠650 mm/s respectively. Furthermore the influence of a continuous and pulsed laser mode was analysed. A focus was set on the identification of parameters that enable a highly productive manufacturing while maintaining a high part density. A parameter set for relative density rel. > 94 % and a buildup rate v = 0.59 mm3/s was developed.
  • Publication
    Cutting edge preparation of monolithic ceramic milling tools
    ( 2021)
    Uhlmann, Eckart
    ;
    Polte, Mitchel
    ;
    Polte, Julian
    ;
    Hocke, Toni
    Due to international competition, continuous increases in productivity, product quality and reduction of production costs are required. Especially, the development of milling tools made of innovative cutting materials and application-specific tool geometries for the machining of brittle materials are in focus to overcome these challenges. One approach to improve the performance and the tool behaviour concerning milling of graphite is the use of monolithic ceramic milling tools. Unfortunately, the high brittleness of the ceramic leads to breakouts on the cutting edge during the grinding process. This results in an increased maximum chipping of the cutting edge, which has a significant influence on the milling process. To improve the breakout behaviour, a cutting edge preparation with the immersed tumbling process was applied. To enable a process reliable cutting edge preparation, a suitable lapping medium, the influence of the processing time as well as the depth of imme rsion were investigated. Besides the maximum chipping of the cutting edge, the rounded cutting edge radius was also analysed. The results show that a process reliable cutting edge preparation of monolithic ceramic milling tools with a maximum chipping of the cutting edge RS,max ⤠3 µm and a rounded cutting edge radius of rβ ⤠7 µm could be realised. In future investigations, the experimental applicability of monolithic ceramic milling tools will be proved.
  • Publication
    Titanium Ti-6Al-4V alloy milling by applying industrial robots
    ( 2021)
    Grisol de Melo, Ever
    ;
    Mohnke, Christian
    ;
    Polte, Julian
    ;
    Oliveira Gomes, Jefferson de
    ;
    Uhlmann, Eckart
    Robotic machining is an alternative to manufacturing processes that combines the technologies of a high-performance machine tool with the flexibility of a 6-axis jointed arm robot. With their large working area, industrial robots are of particular interest for processing large-volume components and large structures, like aircraft components. An influencing variable, which is particularly relevant for milling processes with industrial robots are the cutting force F and the resulting dimensional deviation D. Milling tests of titanium alloys were carried out with an industrial robot and the results compared with a conventional machine tool. Due to the low thermal conductivity and high chemical reactivity of the Ti-6Al-4V alloy, heat is generated and increases the temperature in the contact region of the cutting tool/work piece. That has an impact on the cutting tool wear and increases the cutting force F, and consequently, the dimensional deviation D and the machined surface quality. The aim of the investigations is to find a suitable parameter selection and machining strategy for machining titanium alloys with minimal deviation D and an appropriate surface finish.
  • Publication
    Sensor integration in hybrid additive manufactured parts for real-time monitoring in turbine operations
    ( 2021)
    Uhlmann, Eckart
    ;
    Polte, Julian
    ;
    Kersting, Robert
    ;
    Brunner-Schwer, Christian
    ;
    Neuwald, Tobias
    Real-time monitoring of operation conditions such as tempeatures and vibrations enables efficiency enhancement for maintenance tasks. In energy industry monitoring of critical components such as turbine blades is essential for the operation safety. But the effective recording of critical process data is a challenging task due to the extreme operating conditions. With a hybrid processing approach combining two additive manufacturing technologies new classes of self-monitoring components become possible allowing data acquisition directly inside the component. Using the example of a turbine blade, the hybrid process chain is described. The turbine blade blank is produced via Laser Powder Bed Fusion (L-PBF) with channels for the integration of high temperature sensors. After integration cavities were closed by Laser Directed Energy Deposition (L-DED) followed by classical milling operations for part finishing. The data acquisition is integrated in state-of-the-art product l ifecycle monitoring (PLM) software to create a digital twin. Evaluation shows that temperature could be successfully monitored at conditions of Π= 550°C.
  • Publication
    Agiles Modellieren von Servicetätigkeiten
    ( 2021)
    Uhlmann, Eckart
    ;
    Bösing, Manuel
    ;
    Polte, Julian
    ;
    Kirsch, Lucas
    ;
    Altmann, Ian
    ;
    Emmerling, Roman
    Kontextsensitive Assistenzsysteme bieten ein großes Potenzial zur Optimierung von Arbeitsabläufen. Durch die Einbindung Digitaler Zwillinge können unmittelbar Kontextinformationen zur Verfügung gestellt werden, wobei die Modellierung der Arbeitsabläufe derzeit wenig standardisiert ist. Die in diesem Beitrag vorgestellte Lösung zeigt eine interaktive Software-Applikation für kontextsensitive Assistenzsysteme in Kombination mit Prozesspatterns für die Modellierung von Servicefällen.
  • Publication
    Evaluation of carbon fiber reinforced polymer – CFRP – machining by applying industrial robots
    ( 2021)
    Grisol De Melo, Ever
    ;
    Santos Silva, Jéssica Christina dos
    ;
    Klein, Tiago Borsoi
    ;
    Polte, Julian
    ;
    Uhlmann, Eckart
    ;
    Oliveira Gomes, Jefferson de
    Carbon fiber reinforced polymer (CFRP) is widely used in high-tech industries because of its interesting characteristics and properties. This material presents good strength and stiffness, relatively low density, high damping ability, good dimensional stability, and good corrosion resistance. However, the machinability of composite materials is complex because of the matrix/fiber interface, being a challenging machining material. The CFRP milling process is still necessary to meet dimensional tolerances, the manufacture of difficult-to-mold features like pockets or complexes advance surfaces, finish the edges of laminated composites, or drill holes for the assembly of the components. Besides, the demand for low-cost, reconfigurable manufacturing systems of the industry demonstrates that the application of industrial robots (IRs) in the CFRP milling process becomes an alternative for providing automation and flexibility. Therefore, the objective of this work is to evaluate the performance of the low payload IR KUKA KR60 HA in a milling experiment of CFRP, which indicates its potential application as an alternative to milling process. Furthermore, the influence of the cutting tool geometry as well as the cutting parameters in the machining behavior with IRs is evaluated.
  • Publication
    Micro-milling of a sprue structure in tungsten carbide-based metal matrix composite
    ( 2021)
    Uhlmann, Eckart
    ;
    Polte, Julian
    ;
    Polte, Mitchel
    ;
    Hein, Christoph
    ;
    Hocke, Toni
    ;
    Jahnke, Christian
    Many industries rely on plastic components manufactured by micro-injection moulding. There is a high potential to further increase the cost-effectiveness by machining the moulds needed for this process from non-ferrous metals and reinforcing the parts of the mould, which experience high loads during the micro-injection moulding. Inserting tungsten carbide particles locally into the surface of these non-ferrous metals is one possibility of reinforcement. The resulting metal-matrix-composites (MMC) exhibit the needed wear resistance, while the ground material can be machined very effectively through micro-milling. In contrast, the Micro-milling of these MMC-materials is challenging and so far not state of the art. Thus, this investigation is concerned with the development and qualification of micro-milling parameters for tungsten carbide-based MMC-materials. Binderless polycrystalline diamond as innovative cutting material was applied for this purpose. The goal of the mil ling parameter development was to optimize the surface roughness and the form accuracy for machining an aluminium bronze workpiece reinforced with tungsten carbide particles through laser injection. Based on an analysis of a wide range of process parameters, an optimised milling strategy was applied to machine a sprue structure from the described MMC-material. Different parameter sets are evaluated by analysing the form accuracy and measuring the surface roughness of machined structures. A surface roughness of Ra = 80 nm and form accuracy of a = 3 µm could be achieved with optimized micro-milling parameters and qualified the developed parameters for industrial applications.
  • Publication
    Tool wear and surface roughness in micro-milling of aluminium and high-alloyed aluminium materials using cutting tools made of binderless carbide
    ( 2021)
    Uhlmann, Eckart
    ;
    Polte, Mitchel
    ;
    Wiesner, H.M.
    ;
    Polte, Julian
    ;
    Hein, Christoph
    Micro-milling can be applied for manufacturing in a wide range of materials and complex geometries. This process is especially important for the aerospace industry. High-alloyed aluminium is a common material for aerospace applications with complex micro- and macro-geometry due to its high wear resistance. The costs-effectiveness of producing these parts can be increased by using tools with improved wear behaviour and higher life times. However, wear-resistant tools are often associated with higher tool costs, which reduces the cost-effectivness of the whole production. An innovative solution is offered by the use of a cutting tool made of binderless tungsten carbide. The micro-milling of conventional and high-alloy aluminium with a new cutting material based on a binderless tungsten carbide is analysed in this investigation. The absence of a binding phase leads to an increased hardness and improves the wear behaviour of these tools. Therefore, tools with a tool diamete r of D = 10 mm were manufactured and there machinability was successfully proven. The feasibility of these innovative tools is demonstrated in a series of experiments. The experimental investigations were carried out on the five-axis high precision machine tool PFM 4024-5D PRIMACON GMBH, Peißenberg, Germany, with a workpiece made of TiAl 48-2-2. A surface roughness of Ra = 0.202 µm was detected after a path length due to primary motion lc = 70 m without any noticeable wear marks on the cutting tool. These results show the economic potential for milling tools based on binderless carbide for achieving high precision surfaces while reaching high lifetimes.