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Coaxial Laser wire Direct Energy Deposition (L-DED) promises a direction-independent buildup due to a centric supply of the welding material. To fabricate Functionally Graded Materials (FGMs), a processing head was designed that is capable of supplying two wire materials into the processing zone. This study investigates the direction dependency of welding seams produced by two 1.4718 metal wires with a diameter of 0.8 mm in a coaxial laser setup using three separately controllable single laser beams with a maximum combined laser power of 660 W. The welding wires are supplied simultaneously to the laser spot under an incidence angle of 3.5° to the middle axis of the processing head. The seam geometry is investigated using a confocal laserscanning-microscope. A comparison of the height, width and macroscopic seam geometry reveals the influence of the welding direction on the seam geometry and quality in Laser Double wire Direct Energy Deposition (LD-DED).
A proven method to enhance the mechanical properties of additively manufactured plastic parts is the embedding of continuous fibers. Due to its great flexibility, continuous fiber-reinforced material extrusion allows fiber strands to be deposited along optimized paths. Nevertheless, the fibers have so far been embedded in the parts contour-based or on the basis of regular patterns. The outstanding strength and stiffness properties of the fibers in the longitudinal direction cannot be optimally utilized. Therefore, a method is proposed which allows to embed fibers along the principal stresses into the parts in a load-oriented manner. A G-code is generated from the calculated principal stress trajectories and the part geometry, which also takes into account the specific restrictions of the manufacturing technology used. A distinction is made between fiber paths and the matrix so that the average fiber volume content can be set in a defined way. To determine the mechanical properties, tensile and flexural tests are carried out on specimens consisting of carbon fiber-reinforced polyamide. In order to increase the influence of the principal stress-based fiber orientation, open-hole plates are used for the tensile tests, as this leads to variable stresses across the cross section. In addition, a digital image correlation system is used to determine the deformations during the mechanical tests. It was found that the peak load of the optimized open-hole plates was greater by a factor of 3 and the optimized flexural specimens by a factor of 1.9 than the comparison specimens with unidirectional fiber alignment.
Continuous Fiber-Reinforced Material Extrusion with Hybrid Composites of Carbon and Aramid Fibers
(2022)
An existing challenge in the use of continuous fiber reinforcements in additively manufactured parts is the limited availability of suitable fiber materials. This leads to a reduced adaptability of the mechanical properties to the load case. The increased design freedom of additive manufacturing allows the flexible deposition of fiber strands at defined positions, so that even different fiber materials can be easily combined in a printed part. In this work, therefore, an approach is taken to combine carbon and aramid fibers in printed composite parts to investigate their effects on mechanical properties. For this purpose, tensile, flexural and impact tests were performed on printed composite parts made of carbon and aramid fibers in a nylon matrix with five different mixing ratios. The tests showed that the use of hybrid composites for additive manufacturing is a reasonable approach to adapt the mechanical properties to the loading case at hand. The experiments showed that increasing the aramid fiber content resulted in an increase in impact strength, but a decrease in tensile and flexural strength and a decrease in stiffness. Microstructural investigations of the fracture surfaces showed that debonding and delamination were the main failure mechanisms. Finally, Rule of Hybrid Mixture equations were applied to predict the mechanical properties at different mixture ratios. This resulted in predicted values that differed from the experimentally determined values by an average of 5.6%.
Die Digitalisierung birgt sowohl für den Unternehmer, als auch für den Kunden diverse Vorteile. Als Instrument zur Veranschaulichung dieser Vorteile dienen vor allem Service-Apps, welche bereits von großen Unternehmen beispielsweise zur Produktnachverfolgung etabliert wurden. Das Mittelstand 4.0 – Kompetenzzentrum Hannover legt den Fokus auf kleine und mittelständische Produktionsbetriebe und vermittelt das Potenzial der Digitalisierung im Rahmen von Industrie 4.0. Dies geschieht anhand einer Produktionslinie personalisierter Kugelschreiber und einer zu Demonstrationszwecken entwickelten App für mobile Endgeräte. Konzeptionierung, Entwicklung und Umsetzung dieser App werden genauestens aufgeführt und erläutert. Die App wurde unter dem Betriebssystem Android entwickelt und gliedert sich in sieben Phasen, beginnend mit der Anforderungsanalyse bis hin zur Veröffentlichung im Google Play Store. Während der Unternehmer die Möglichkeit geboten bekommt, Rückschlüsse als Entscheidungshilfe zur effizienteren Gestaltung der Produktion zu nutzen, ist der Kunde in der Lage, seine Aufträge echtzeitnah in der Produktion nachzuverfolgen und gegebenenfalls Änderungen vorzunehmen.
