In Bone Tissue Engineering (BTE), autologous bone-regenerative cells are combined with a scaffold for large bone defect treatment (LBDT). Microporous, polylactic acid (PLA) scaffolds showed good healing results in small animals. However, transfer to large animal models is not easily achieved simply by upscaling the design. Increasing diffusion distances have a negative impact on cell survival and nutrition supply, leading to cell death and ultimately implant failure. Here, a novel scaffold architecture was designed to meet all requirements for an advanced bone substitute. Biofunctional, porous subunits in a load-bearing, compression-resistant frame structure characterize this approach. An open, macro- and microporous internal architecture (100 µm–2 mm pores) optimizes conditions for oxygen and nutrient supply to the implant’s inner areas by diffusion. A prototype was 3D-printed applying Fused Filament Fabrication using PLA. After incubation with Saos-2 (Sarcoma osteogenic) cells for 14 days, cell morphology, cell distribution, cell survival (fluorescence microscopy and LDH-based cytotoxicity assay), metabolic activity (MTT test), and osteogenic gene expression were determined. The adherent cells showed colonization properties, proliferation potential, and osteogenic differentiation. The innovative design, with its porous structure, is a promising matrix for cell settlement and proliferation. The modular design allows easy upscaling and offers a solution for LBDT.
The direct use of an advanced binder‐free additive manufacturing technique, namely laser powder bed fusion (L‐PBF), does not easily allow obtaining variously shaped, fully dense Nd–Fe–B magnets with high coercivity. The process inherently leads to the re‐melting of the powder and appearance/disappearance of undesired/desired microstructural features responsible for low and large coercivity. In this work, the development of a useful microstructure responsible for high coercivity in Pr21Fe73.5Cu2B3.5 and Nd21Fe73.5Cu2B3.5 alloys and a possible way to produce fully dense permanent magnets via additive manufacturing processes is demonstrated using: (i) suction casting technique, which provides a high cooling rate and thus similar microstructures as in L‐PBF but requires only very small amounts of powder; (ii) conventional L‐PBF processing using kg of powder, and (iii) a subsequent annealing treatment that is similar to a conventional sintering treatment. The subsequent heat treatment is necessary to develop high coercivity by forming a novel microstructure: hard magnetic (Nd,Pr)2Fe14B grains embedded in a matrix of intermetallic (Nd,Pr)6Fe13Cu phase. Furthermore, it is demonstrated that Pr21Fe73.5Cu2B3.5 exhibits a higher coercivity than Nd21Fe73.5Cu2B3.5 because of a finer and more homogeneous grain size distribution of the Pr2Fe14B phase. The final L‐PBF printed Pr21Fe73.5Cu2B3.5 samples provide a coercivity of 0.75 T.
Additive manufacturing, in particular the powder bed fusion of metals using a laser beam, has a wide range of possible technical applications. Especially for safety-critical applications, a quality assurance of the components is indispensable. However, time-consuming and costly quality assurance measures, such as computer tomography, represent a barrier for further industrial spreading. For this reason, alternative methods for process anomaly detection using process monitoring systems have been developed. However, the defect detection quality of current methods is limited, as single monitoring systems only detect specific process anomalies. Therefore, a new methodology to evaluate the data of multiple monitoring systems is derived using sensor data fusion. Focus was placed on the causes and the appearance of defects in different monitoring systems (photodiodes, on- and off-axis high-speed cameras, and thermography). Based on this, indicators representing characteristics of the process were developed to reduce the data. Finally, deterministic models for the data fusion within a monitoring system and between the monitoring systems were developed. The result was a defect detection of up to 92% of the melt track defects. The methodology was thus able to determine process anomalies and to evaluate the suitability of a specific process monitoring system for the defect detection.
Due to time and cost-intensive quality assurance of LPBF an in-process monitoring is developed by data fusion of photodiodes, thermography and high–speed camera on three abstraction levels resulting in a defect detection of 86 %.
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