Funktionalisierte Bauteile durch Selektives Maskensintern

Das Selektive Maskensintern ist ein neues, pulverbasiertes Additives Fertigungsverfahren. Das schichtweise aufgebrachte Kunststoffpulver wird hier flächig über einen Infrarotstrahler belichtet und aufgeschmolzen. Das Verfahren bietet ein großes Potential dreidimensionale, wärmeleitfähige Bauteile mit beliebiger Geometrie herzustellen. In diesem Beitrag wird darauf eingegangen, wie kommerziell erhältliches Polyamid 12-Pulver mit thermisch leitfähigen Füllstoffen, wie Aluminiumgrieß und Kupferkugeln, modifiziert und funktionalisierte Bauteile hergestellt werden können. Prozessrelevante Materialeigenschaften werden mittels Differential Scanning Kalorimetrie, Rotationsviskosimetrie und der Wärmeleitfähigkeit der modifizierten Pulver bestimmt. An den gefertigten Bauteilen wird die ausgebildete Morphologie, die mechanischen Eigenschaften als auch die Bauteilwärmeleitfähigkeit untersucht.A new powder-based additive manufacturing technology is selective mask sintering (SMS). Here, the material is molten laminar by broad banded infrared radiation. There is a high potential to create three-dimensional thermal conductive parts by using this technology layer by layer. In this publication commercially available PA12 powders are modified with thermally conductive fillers like aluminum grid and copper balls. Process relevant powder properties were characterized by differential scanning calorimetry, rotational viscosimetry and thermal conductivity measurements were performed. Subsequently the morphology, mechanical behavior as well as thermal conductivity of the manufactured specimens is investigated

rietzel

Die komplexen transienten thermischen Bauraumverhältnisse während der Schicht-generierung beim Lasersintern von Thermoplasten haben direkten Einfluss auf die resultierenden Bauteileigenschaften. Dies schlägt sich in Effekten wie dem „Curl“ oder Bauteilverzug nieder. Ohne Kenntnisse über die zeitlichen und örtlichen Tempe-raturverhältnisse im Bauraum können weder der gesamte Bauraum ausgenutzt, noch die späteren Bauteileigenschaften vorhergesagt werden. Folglich wird die Wirtschaft-lichkeit des Verfahrens im Hinblick auf einen Einsatz zur Serienproduktion begrenzt. Neben der experimentellen Erforschung der transienten thermischen Zustände wäh-rend des Lasersinterns ist die Modellbildung zur simulativen Abbildung ebendieser von großer Bedeutung. Dieser Beitrag stellt den grundlegenden Aufbau eines Simu-lationsmodells für die schichtweise Bauteilgenerierung dar und zeigt allgemeine Mo-dellierungsansätze für die charakteristischen thermischen Materialkennwerte von Pulvern auf. Weiterhin erfolgt anhand einer Parameterstudie eine Quantifizierung der Effekte einzelner Materialeigenschaften und Prozessstellgrößen auf die mittels finiter Elemente Methode berechneten Temperaturverhältnisse an einer Pulverschicht

Selektives Lasersintern von teilkristallinen Thermoplasten

Da eine flexible Fertigung im Bereich von Losgrößen zwischen 1-1000 Stück in vielen Wirtschaftszweigen vermehrt an Bedeutung gewinnt, steigt das Interesse an Verfahren wie dem Selektiven Lasersintern. Dennoch sollen die Eigenschaften von in Serie eingesetzten Werkstoffen erreicht werden. Aufgrund der bestehenden werkstofflichen Restriktionen auf Polyamid 12 wird aktuell an der Verarbeitung anderer teilkristalliner Thermoplaste geforscht. In diesem Beitrag werden die sich in der Markteinführung befindlichen Werkstoffe vorgestellt und basierend auf der Verarbeitung weiterer Thermoplaste die bestehende Modellvorstellung zum Lasersintern erweitert.As a flexible manufacturing for lot sizes of 1-1000 components gains more interest in many branches of trade, technologies such as selective laser sintering (SLS) become more interesting. Nevertheless should the properties of materials used in series manufacturing be achievable. Mainly polyamide 12 can be used for direct part generation. This leads to restrictions for many applications. Thus research on other types of polymers plays a major role in applying additive manufacturing in the serial production of individual products. In this paper, the suitability and processing behavior with respect of melting, (isothermal) crystallization, morphology resulting and part properties of new thermoplastics is presented and compared to commercially available powders. By using thermoanalytical methods, comprehensive process simulation can be carried out

Comparative Analysis of the Impact of Additively Manufactured Polymer Tools on the Fiber Configuration of Injection Molded Long-Fiber-Reinforced Thermoplastics

Additive tooling (AT) utilizes the advantages of rapid tooling development while minimizing geometrical limitations of conventional tool manufacturing such as complex design of cooling channels. This investigation presents a comparative experimental analysis of long-fiber-reinforced thermoplastic parts (LFTs), which are produced through additively manufactured injection molding polymer tools. After giving a review on the state of the art of AT and LFTs, additive manufacturing (AM) plastic tools are compared to conventionally manufactured steel and aluminum tools toward their qualification for spare part and small series production as well as functional validation. The assessment of the polymer tools focuses on three quality criteria concerning the LFT parts: geometrical accuracy, mechanical properties, and fiber configuration. The analysis of the fiber configuration includes fiber length, fiber concentration, and fiber orientation. The results show that polymer tools are fully capable of manufacturing LFTs with a cycle number within hundreds before showing critical signs of deterioration or tool failure. The produced LFTs moldings provide sufficient quality in geometrical accuracy, mechanical properties, and fiber configuration. Further, specific anomalies of the fiber configuration can be detected for all tool types, which include the occurrence of characteristic zones dependent on the nominal fiber content and melt flow distance. Conclusions toward the improvement of additively manufactured polymer tool life cycles are drawn based on the detected deteriorations and failure modes

In-vitro evaluation of Polylactic acid (PLA) manufactured by fused deposition modeling

Abstract Background With additive manufacturing (AM) individual and biocompatible implants can be generated by using suitable materials. The aim of this study was to investigate the biological effects of polylactic acid (PLA) manufactured by Fused Deposition Modeling (FDM) on osteoblasts in vitro according to European Norm / International Organization for Standardization 10,993–5. Method Human osteoblasts (hFOB 1.19) were seeded onto PLA samples produced by FDM and investigated for cell viability by fluorescence staining after 24 h. Cell proliferation was measured after 1, 3, 7 and 10 days by cell-counting and cell morphology was evaluated by scanning electron microscopy. For control, we used titanium samples and polystyrene (PS). Results Cell viability showed higher viability on PLA (95,3% ± 2.1%) than in control (91,7% ±2,7%). Cell proliferation was highest in the control group (polystyrene) and higher on PLA samples compared to the titanium samples. Scanning electron microscopy revealed homogenous covering of sample surface with regularly spread cells on PLA as well as on titanium. Conclusion The manufacturing of PLA discs from polylactic acid using FDM was successful. The in vitro investigation with human fetal osteoblasts showed no cytotoxic effects. Furthermore, FDM does not seem to alter biocompatibility of PLA. Nonetheless osteoblasts showed reduced growth on PLA compared to the polystyrene control within the cell experiments. This could be attributed to surface roughness and possible release of residual monomers. Those influences could be investigated in further studies and thus lead to improvement in the additive manufacturing process. In addition, further research focused on the effect of PLA on bone growth should follow. In summary, PLA processed in Fused Deposition Modelling seems to be an attractive material and method for reconstructive surgery because of their biocompatibility and the possibility to produce individually shaped scaffolds