Christoph Klahn

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Klahn

First Name

Christoph

ORCID

0000-0001-6947-3621

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Publications 1 - 10 of 37

Considering Part Orientation in Design for Additive Manufacturing
Leutenecker, Bastian; Klahn, Christoph; Meboldt, Mirko (2016)
Procedia CIRP ~ 26th CIRP Design Conference
Additive Manufacturing (AM) is established not only in prototyping, but also in serial production of end-use products. To use the full potential of the production technology the restrictions of current additive manufacturing processes (like support structures in Selective Laser Melting) must be considered in the design process. Especially the compliance with design rules from early design stages on is important in AM serial production, due to production quantities and the resulting scale effect. The part orientation in the build space has a strong influence on many quality characteristics. In order to use the full potential and to consider the restrictions from the start, a design guideline is necessary to support the whole design process. For this purpose, this paper presents a framework for design guidelines. The framework distinguishes between process characteristics, design principles and design rules; each supporting the designer during different stages of the design process. Furthermore, the paper examines the influence of part orientation in existing design rules and elaborates its importance. Based on this result, the design principle “early determination of part orientation” is presented, which includes a process for determining the part orientation in early stage of the design process. In addition, a design process for additive manufactured parts is demonstrated on an extensive showcase, following the guideline framework and including the principle for early determination of part orientation. The presented framework proved to be helpful in the design process and will be used in the future to collect more process characteristics, design principles and rules.
Design and validation of integrated clamping interfaces for post-processing and robotic handling in additive manufacturing
Ferchow, Julian; Kälin, Dominik; Englberger, Gokula; et al. (2022)
The International Journal of Advanced Manufacturing Technology
Additive manufacturing (AM), particularly laser-based powder bed fusion of metals (LPBF), enables the fabrication of complex and customized metallic parts. However, 20-40% of the total manufacturing costs are usually attributed to post-processing steps. To reduce the costs of extensive post-processing, the process chain for AM parts has to be automated. Accordingly, robotic gripping and handling processes, as well as an efficient clamping for subtractive machining of AM parts, are key challenges. This study introduces and validates integrated bolts acting as a handling and clamping interface of AM parts. The bolts are integrated into the part design and manufactured in the same LPBF process. The bolts can be easily removed after the machining process using a wrench. This feasibility study investigates different bolt elements. The experiments and simulations conducted in the study show that a force of 250 N resulted in a maximum displacement of 12.5 mu m. The milling results of the LPBF parts reveal a maximum roughness value, Ra, of 1.42 mu m, which is comparable to that of a standard clamping system. After the bolt removal, a maximum residual height of 0.067 mm remains. Two case studies are conducted to analyze the form deviation, the effect of bolts on build time, and material volume and to demonstrate the application of the bolts. Thus, the major contribution of this study is the design and the validation of standardized interfaces for robotic handling and clamping of complex AM parts. The novelties are a simple and clean interface removal, less material consumption, less support structure required, and finally an achievement of a five-side tool accessibility by combining the interfaces with a three-jaw chuck.
Valve Body Element with Generative Layer-By-Layer Construction
Stoll, Philipp; Spierings, Adriaan; Ferchow, Julian; et al. (2019)
The invention relates to a valve body element (10) which is produced as a single piece and which has a hybrid construction. The valve body element has a conventionally produced base (101) and structures which are constructed on the base (101) by means of a generative production method. The combination has such a valve body element (10) and an embedded sensor. The valve body (2) has one or more of said valve body elements (10) and two or more channels, each of which has an inlet (50). All of the inlets (50) are at least partly formed in the base (101).
Individualized and sustainable lightweight structures from Additive Manufacturing and carbon fiber patched composites
Kussmaul, Ralph; Biedermann, Manuel; Jónasson, Jónas; et al. (2018)
Book of Abstracts. Symposium Lightweight Design in Product Development, Zurich, 14.06. - 15.06.2018
Model of surface roughness and material removal using abrasive flow machining of selective laser melted channels
Ferchow, Julian; Baumgartner, Harry; Klahn, Christoph; et al. (2020)
Rapid Prototyping Journal
Purpose Internal channels produced by selective laser melting (SLM) have rough surfaces that require post-processing. The purpose of this paper is to develop an empirical model for predicting the material removal and surface roughness (SR) of SLM-manufactured channels owing to abrasive flow machining (AFM). Design/methodology/approach A rheological model was developed to simulate the viscosity and power-law index of an AFM medium. To simulate the pressure distribution and velocity in the SLM channels, the fluid behavior and SR in the channels were simulated by using computational fluid dynamics. The results of this simulation were then applied to create an empirical model that can be used to predict the SR and material removal thickness. To verify this empirical model, it was applied to an actual part fabricated by SLM. The results were compared with the measurements of the SR and channel diameter subsequent to AFM. Findings The proposed model exhibits maximum deviation between the model and the measurement of -1.1% for the down-skin SR, -0.2% for the up-skin SR and -0.1% for material removal thickness. Practical implications The results of this study show that the proposed model can avoid expensive iterative tests to determine whether a given channel design leads to the desired SR after smoothing by AFM. Therefore, this model helps to design an AFM-ready channel geometry. Originality/value In this paper, a quantitatively validated AFM model was proposed for complex SLM channels with varying orientation angles.
Integration of Gas-Permeable Structures in Laser Additive Manufactured Products
Klahn, Christoph; Meboldt, Mirko (2015)
Additive Manufacturing: Innovations, Advances, and Applications
Unique coding for authentication and anti-counterfeiting by controlled and random process variation in L-PBF and L-DED
Eisenbarth, Daniel; Stoll, Philipp; Klahn, Christoph; et al. (2020)
Additive Manufacturing
Additive manufacturing technologies enable various possibilities to create and modify the material composition and structure on a local level, but are often prone to undesired defects and inhomogeneities. This contribution makes use of such flaws to generate material-inherent, hidden codes and watermarks in metals for authentication and anti-counterfeiting applications. By controlled and random process variation, unique codes that can be read and authenticated by an eddy current device were produced with the processes of laser powder bed fusion (L-PBF) and laser directed energy deposition (L-DED). Two approaches are presented: First, volumetric, porous structures with a defined shape are manufactured with L-PBF. Second, coatings are fabricated by L-DED with alternating process parameters, leading to local deviations of the magnetic permeability. This non-deterministic coding approach generates a distinctive material structure that triggers high signal amplitudes in the eddy current measurement. Counterfeiting becomes impossible due to the irreproducible melt pool dynamics. Statistical hypothesis testing proves that the system is able to prevent false acceptance or rejection of a code with a certainty of 500 million to one. A low-cost setup for a novel locking system demonstrates that a code can be sensed reliably within one second.
Enabling Graduate Students to Design for Additive Manufacturing through Teaching and Experience Transfer
Ferchow, Julian; Klahn, Christoph; Meboldt, Mirko (2018)
E&PDE ~ Proceedings of the 20th International Conference on Engineering and Product Design Education (E&PDE 2018)
Valve Body Element with Embedded Sensors
Stoll, Philipp; Spierings, Adriaan; Ferchow, Julian; et al. (2019)
Eine Kombination (9) aufweisend ein Ventilkörperelement (10) und einen Sensor (40), wobei das Ventilkörperelement (10) zumindest teilweise durch ein generatives Herstellungsverfahren schichtweise und einstückig aufgebaut worden ist und der Sensor (40) in das Ventilkörperelement (10) eingebettet ist. Zudem ein Verfahren zu deren Herstellung; ein Ventil (1) aufweisend solche Kombinationen (9) sowie ein Set aufweisend zwei oder mehr Ventilkörper (2).
Composites Part Production with Additive Manufacturing Technologies
Türk, Daniel-Alexander; Kussmaul, Ralph; Zogg, Markus; et al. (2017)
Procedia CIRP ~ 1st CIRP Conference on Composite Materials Parts Manufacturing (CIRP CCMPM 2017)
Additive Manufacturing (AM) is of particular interest in the context of composite part production as AM promises the production of integrated, complex structures with low lead times. Currently, AM is used for tooling and sandwich cores with added functionalities. This paper presents four design principles that improve the production of composites parts during layup, handling, curing and post processing in the layup process. Design principles are applied to a hat-stiffener, a highly integrated aircraft instrument panel and a novel insert eliminating drilling operations. Results show that AM can reduce the part count, assembly steps and deformations during curing.

Publications 1 - 10 of 37

Christoph Klahn

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