9 research outputs found
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Investigation of the Process Parameters and Geometry Dependent Shrinkage Behavior of Raster Lines in the Fused Deposition Modeling Process
Additive Manufacturing processes are able to generate components from raw material
(filament, powder etc.) without the need of tools or conventional machining. One of the most
common Additive Manufacturing processes is the Fused Deposition Modeling (FDM). Here, a
thermoplastic polymer filament is fed into a heated nozzle where the filament is plasticized.
The plasticized material is then deposited, layer-by-layer onto the building platform or the
already existing component structure in a defined way. Thermoplastic polymers show a material
specific shrinkage induced by the cooling process. The recurring heat input by depositing
adjacent strands results in a complex cooling situation which contributes to the non-uniform
shrinkage of the component. In the investigations, first, a Design of Experiments (DoE) is
carried out to determine the influence of selected process parameters on the shrinkage behavior
of the raster lines. Following, the geometrical deviations of simple geometries under
consideration of different process parameters are determined and analyzed.Mechanical Engineerin
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Validation and Comparison of Fem-Simulation Results of the Fused Deposition Modeling Process under Consideration of Different Mesh Resolutions
The Fused Deposition Modeling (FDM) process is an Additive Manufacturing (AM)
technology. In the FDM process, components are generated by feeding a thermoplastic polymer
filament into a heated nozzle and depositing the molten material layer-by-layer in a defined
way onto the building platform or an already existing component structure. The strand-by-
strand deposition leads to a complex cooling situation which contributes to the non-uniform
shrinkage of components in the FDM-process. Using an AM plug-in for the FEM-simulation
software Abaqus, the thermal and mechanical aspects of a component can be simulated
according to the temporal sequence of the manufacturing process. For this, the birth-death-
method is used in the simulations. During the investigations, the simulation results regarding
geometrical deviations are compared to the actual deviation of the manufactured specimens.
Furthermore, the influences of the mesh resolution on the simulation results and the required
time for the simulations are considered.Mechanical Engineerin
Fabrication of highly filled wood plastic composite pallets with extrusion‐compression molding technique
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Process Parameter Optimization to Improve the Mechanical Properties of Arburg Plastic Freeformed Components
The Arburg Plastic Freeforming (APF) is an additive manufacturing process that allows three-dimensional, thermoplastic components to be produced in layer by layer. The components are generated by
depositing fine, molten plastic droplets. One of the main advantages of the APF process is the open machine
control. Thus, the process parameters can be adapted and optimized for the individual applications.
The optimization is carried out on the basis of a variation of the process parameters using a statistical
design of experiments. Relevant process parameters are the layer thickness, the form factor, the raster and delta
angle as well as the overlap between the contour and the filling of a layer. In addition, the nozzle and build
chamber temperatures are varied. Using this procedure, the effects of the influencing parameters on the
mechanical properties and the interactions between the influencing parameters are analyzed and converted into
mathematical models. On the basis of the results and the models, guidelines will be developed to assist the user
of APF technology in the systematic process configuration for their own applications. The material used is ABS,
one of the most frequently used amorphous thermoplastics in additive manufacturing. The mechanical properties
are determined on the basis of tensile tests and the characteristic values tensile strength, elongation at break and
Young's modulus. The results should show the performance of the APF technology in regard to the mechanical
properties.Mechanical Engineerin
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Investigation and Modeling of the Residence Time Dependent Material Degradation in the Arburg Plastic Freeforming
The Arburg Plastic Freeforming (APF) is an additive manufacturing process with which
three-dimensional, thermoplastic components can be produced layer by layer. One
disadvantage of the APF is the long residence time of the molten material in the plasticizing
unit compared to conventional injection moulding. The dosing volume is emptied very slowly
due to only discharging fine plastic droplets. As a result, long residence times can be expected,
which can lead to thermal degradation of the material.
The aim of this study was to develop a model for calculating the residence time of the
material in the APF. The residence time of the material in the thermally critical dosing volume
is predicted using software developed in-house. The accuracy of the model could be verified
by experimental investigations. Finally, the thermal degradation of the material was
investigated by analyzing the correlation to the mechanical properties of tensile strength
specimens.Mechanical Engineerin
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Comparison of Component Properties and Economic Efficiency of the Arburg Plastic Freeforming and Fused Deposition Modeling
The additive manufacturing process Fused Deposition Modeling (FDM) is established
in the industry for many years. A new, similar process to FDM is the Arburg Plastic
Freeforming (APF). The main differences between both processes are the form of the starting
material (FDM: Filaments, APF: Conventional granulate) and the material deposition during
the layer formation (FDM: Melt strand, APF: fine molten droplets).
Since the two processes can be used in similar applications, the aim of this study is to
compare both processes in a holistic way. Furthermore, the advantages and disadvantages of
the processes are to be highlighted. The systematic comparison between a Stratasys 400mc and
the Freeformer 200-3X is divided into the areas of component properties, design limitations and
economic efficiency. The material ABS-M30 (Stratasys) is used in both processes. The results
show comparable component properties regarding mechanical and optical properties but also
differences in design limitations and cost efficiency.Mechanical Engineerin
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Investigations for the Optimization of Visual and Geometrical Properties of Arburg Plastic Freeforming Components
Arburg Plastic Freeforming (APF) is an additive manufacturing process with which three-dimensional, thermoplastic components can be produced layer by layer. Visual and geometrical
properties are a major criterion for characterizing the resulting component quality. The aim of
this study was to investigate the influences on visual and geometrical properties of APF
components depending on process parameters. Initially the focus was on the analysis of the
shrinkage behavior of ABS-M30 (Stratasys). On the basis of the results and an existing
procedure by the machine manufacturer, an optimized procedure for determining the scaling
factors was developed to counteract the shrinkage. With this procedure a higher dimensional
accuracy of the components can be achieved. In addition, it was investigated whether an
adaption of the form factor based on a mathematical model depending on the component
geometry makes sense. The results were transferred into manufacturing guidelines, which allow
the user of the APF-technology to optimize process parameters more efficiently.Mechanical Engineerin
Entstehung und Untersuchung eines interpenetrierenden Polymernetzwerks aus Polyharnstoff und Silikonkautschuk beim Vakuumgießverfahren
Der Einsatz von Silikon-Gießwerkzeugen im Vakuumgießverfahren zur Replikation von dreidimensionalen Prototypen-Bauteilen aus Polyurethan ist Stand der Technik. Mit diesem Verfahren soll zukünftig in der Kunststoffverarbeitung die Lücke zwischen sehr geringen Stückzahlen (Rapid Prototyping) und sehr großen Stückzahlen (Spritzgießen) geschlossen werden. Die Entwicklung eines vielseitigen, wirtschaftlichen Kleinserien-verfahrens birgt für die Zukunft der Kunststoffverarbeitung und den alltäglichen Um-gang mit Kunststoffprodukten enorme Vorteile.
Beim Vakuumgießen wird mit Hilfe eines Urmodells eine Gießform aus Silikon aufge-baut. Diese wird dann mit einem Polyurethanharz gefüllt, welches anschließend durch Polyaddition reagiert und erstarrt. Zur Entformung des Bauteils wird das Werkzeug ge-öffnet und das Bauteil entnommen. Für den potentiellen Einsatz des Verfahrens in der Kleinserienproduktion entscheidet die maximal erzielbare Ausbringungsmenge der Werkzeuge über die Wirtschaftlichkeit. Nach aktuellem Stand der Technik versagen die Werkzeuge jedoch durch Alterung des Silikons schon nach wenigen Gießvorgängen.
Es konnte gezeigt werden, dass die Alterung der Werkzeuge durch die Diffusion einer Polyurethanharz-Komponente bedingt ist. Beim Gießprozess migriert Isocyanat in die Silikonoberfläche und reagiert dort mit Restfeuchtigkeit zu Harnstoffderivaten, was schnell zu einer Verhärtung der Silikonmatrix und zum Versagen des Werkzeugs führt.
Der Vortrag beschreibt die chemischen und physikalischen Mechanismen des Diffusi-ons- und Alterungsprozesses. Mit Hilfe der thermogravimetrischen Analyse (TGA) so-wie spektroskopischen Verfahren wie Röntgenfotoelektronenspektroskopie (XPS) und Infrarot-Spektroskopie (FTIR) konnte die Harnstoffbildung innerhalb der Silikonmatrix nachgewiesen werden. Der Einsatz eines Helium-Ionen-Mikroskops (HIM) ermöglichte die Visualisierung eines bei der Alterung entstehenden interpenetrierenden Polymer-netzwerks (IPN) aus Polyurethan und Silikon