Continuous fiber-reinforced manufacturing has many advantages, but the fabrication cost is high and its process is difficult to control. This paper presents a method for printing fiber-reinforced composite on the common fused filament fabrication (FFF) platform. Polylactic Acid (PLA) and Polyethylene terephthalate (PET) fibers are used as printing materials. A spatial continuous toolpath planning strategy is employed to reduce the workload of post-processing without cutting the fiber. Experimental results show that this process not only enables the printing of models with complex geometric shapes but also supports material recycling and reuse. A material recovery rate of 100% for continuous PET fiber and 83% for PLA were achieved for a better environmental impact. Mechanical tests show that the maximum tensile strength of continuous PET fiber-reinforced thermoplastic composites (PFRTPCs) is increased by 117.8% when compared to polyamide-66 (PA66).

Conventional Fused Filament Fabrication (FFF) equipment can only deposit materials in a single direction, limiting the strength of printed products. Robotic 3D printing provides more degrees of freedom (DOF) to control the material deposition and has become a trend in additive manufacturing. However, there is little discussion on the strength effect of multi-DOF printing. This paper presents an efficient process framework for multi-axis 3D printing based on the robot to improve the strength. A multi-DOF continuous toolpath planning method is designed to promote the printed part’s strength and surface quality. We generate curve layers along the model surfaces and fill Fermat spiral in the layers. The method makes it possible to take full advantage of the multi-axis robot arm to achieve smooth printing on surfaces with high curvature and avoid the staircase effect and collision in the process. To further improve print quality, a control strategy is provided to synchronize the material extrusion and robot arm movement. Experiments show that the tensile strength increases by 22–167% compared with the conventional flat slicing method for curved-surface parts. The surface quality is improved by eliminating the staircase effect. The continuous toolpath planning also supports continuous fiber-reinforced printing without a cutting device. Finally, we compared with other multi-DOF printing, the application scenarios, and limitations are given.

Hand pose estimation in cluttered environment is always challenging. In this paper, we address the problem of hand pose estimation from RGB-D sensor. To achieve robust real-time usability, we first design a data acquisition strategy, using a color glove to label different hand parts, and collect a new training data set. Then a novel hand pose estimation framework is presented, so that feature fusion drives hand localization and hand parts classification. Moreover, instead of using articulated model, a simplified and efficient 3D contour model is designed to assist real-time implementation, which does not require a large amount of training data. Experiments show that our approach can handle real-time hand interaction in a desktop environments with cluttered background.

Compared with native blood vessels and existing vascular grafts, design and manufacture of vascular grafts with a three-dimensional topological structure is a key to induce cells and tissue growth, which remains an essential issue in both tissue engineering and regenerative medicine. This study sought to develop a novel triple-layer vascular graft (TLVG) with oriented microgrooves to investigate the mechanical property and endothelialization. The TLVGs were composed of electrospun Poly-ε-caprolactone (PCL)/thermoplastic polyurethane (TPU) as the inner layer, albumen/sodium alginate (SA) hydrogel as the middle layer, and electrospun PCL/TPU as the outer layer. In detail, a cylindrical sacrificial template was designed and printed using polyvinyl alcohol (PVA), served as the electrospinning receiving platform to form the oriented microgrooves in the inner layer of TLVGs. The highly elastic albumen/SA hydrogel and PCL/TPU nanofibers were able to simulate the elastin in blood vessels. In addition, the introduction of the albumen/SA hydrogel layer not only solves the leakage problem of a porous vascular graft but also improves the wettability of the scaffolds. The physicochemical properties and biological characteristics of TLVGs were evaluated by tensile testing, Surface wettability test, Fourier transform-infrared spectroscopy (FTIR) measurement, Live-Dead cell staining assay, and CCK-8 assay. Especially, the oriented microgrooves on the inner surface of the TLVGs can promote human umbilical vein endothelial cells (HUVECs) directed growth and migration in favor of endothelialization. All results showed that the fabricated TLVGs with excellent physicochemical properties and biocompatibility has great potential in clinic application.

For the traditional three-axis (3D) configuration of the additive manufacturing (AM) platform, when printing the target model with a multi-branched structure, it is imperative to construct adequate support structures. To eliminate the use of support during the printing process, a non-directional unsupported 3D printing method for five-axis AM is proposed in this paper. By carrying out the K-means clustering algorithm, the coarse partition of the model is obtained, and then the fine decomposition represented by a sequence of separating planes is determined by a local dynamic search adjustment algorithm according to manufacturing constraints. The multi-branched structure of the model is divided into simple subparts so that the general model can be built in different directions and be printed with its own parts as the support. Two case studies were carried out for verification. The experimental results showed that the branch-model can be printed without support using the non-directional unsupported 3D printing method, and the non-directional unsupported 3D printing can save 18.72–20.60% of materials and 20.60–23.33% of time compared to conventional 3D printing.