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Layered manufacturing with curved layers is a recently proposed rapid prototyping (RP) strategy for the manufacture of curved, thin and shell-type parts and the repair of worn surfaces, etc. The present investigation indicates another possible application area. In case of flat-layered RP of computer-aided design models having randomly located, small-dimensioned but critical surface features, adaptive slicing is resorted to. Large number of thin slices have to be employed to preserve the critical features. In contrast, a considerably lower number of curved thin slices would be required to preserve such surface features in case of RP with curved layers.

The method of preservation of critical features by RP with curved layers is formulated and demonstrated for two clusters of critical features on the surface of a part. A minimum number of such curved layers is identified by application of genetic algorithms (GAs) in case of a simple example. GA evolves the shape of the curved layer passing through the lower cluster so as to make a curved layer pass through the upper cluster of critical features.

In the example part, a 21 per cent reduction in the number of layers is achieved by the application of adaptive curved layers over adaptive straight layers.

The novelty of the concept is the proposed use of curved layered RP with adaptive slicing for the preservation of critical features in final prototyped part. This methodology, applied to part with two distinct clusters, leads to reduced number of layers compared to that obtained in flat-layered RP.

The purpose of this paper is to solve the problems of poor mechanical properties, high surface roughness and waste support materials of thin-walled parts fabricated by flat-layered additive manufacturing process.

This paper proposes a curved-layered material extrusion modeling process with a five-axis motion mechanism. This process has advantages of the platform rotating, non-support printing and three-dimensional printing path. First, the authors present a curved-layered algorithm by offsetting the bottom surface into a series of conformal surfaces and a toolpath generation algorithm based on the geodesic distance field in each conformal surface. Second, they introduce a parallel five-axis printing machine consisting of a printing head fixed on a delta-type manipulator and a rotary platform on a spherical parallel machine.

Mechanical experiments show the failure force of the five-axis printed samples is 153% higher than that of the three-axis printed samples. Forming experiments show that the surface roughness significantly decreases from 42.09 to 18.31 µm, and in addition, the material consumption reduces by 42.90%. These data indicate the curved-layered algorithm and five-axis motion mechanism in this paper could effectively improve mechanical properties and the surface roughness of thin-walled parts, and realize non-support printing. These methods also have reference value for other additive manufacturing processes.

Previous researchers mostly focus on printing simple shapes such as arch or “T”-like shape. In contrast, this study sets out to explore the algorithm and benefits of modeling thin-walled parts by a five-axis machine. Several validated models would allow comparability in five-axis printing.

The purpose of this paper is to study the feasibility of the fabrication of circle arc curved-layered structures via conventional fused deposition modeling (FDM) with three-axis machines and to identify the main structural parameters that have an influence on their mechanical properties.

Customized G-codes were generated via a script developed in MATLAB. The G-codes contain nozzle trajectories with displacements in the three axes simultaneously. Using these, the samples were fabricated with different porosities, and their influence on the mechanical responses evaluated via tensile testing. The load-displacement curves were analyzed to understand the structure-property relationship.

Circled arc curved-layered structures were successfully fabricated with conventional three-axis FDM machines. The response of these curved lattice structures under tensile loads was mapped to three main stages and deformation mechanisms, namely, straightening, stretching and fracture. The micro-structure formed by the transverse filaments affect the first stage significantly and the other two minimally. The main parameters that affect the structural response were found to be the transverse filaments, as these could behave as hinges, allowing the slide/rotation of adjacent layers and making the structure more shear sensitive.

This paper was restricted to arc-curved samples fabricated with conventional three-axis FDM machines.

The FDM fabrication of curved-structures with controlled porosity and their relation to the resulting mechanical properties is presented here for the first time. The study of curved-lattice structures is of great relevance in various areas, such as biomedical, architecture and aerospace.

This paper aims to provide an approach to print shell-type objects using a 5-axis printer. The proposed approach takes advantage of the two additional printer degrees of freedom to provide a curved layer path planning strategy.

This paper addresses curved layer path planning on a 5-axis printer. This printer considers movements along the three usual axes together with two additional axes at the printing table (rotation and tilt), allowing to build more complex and reliable objects. Curved layer path planning is considered where polygons obtained from the slicing stage are approximated by linear and cubic splines. The proposed printing strategy consists in building an inner core supporting structure followed by outer curved layers.

The curved layer path planning strategy is validated for shell-type objects by considering a 5-axis printer simulator. An example with an aeronautic object is presented to illustrate the proposed approach.

The paper presents an approach to curved layer path planning on a 5-axis printer, for shell-type objects.

The rapid development of three-dimensional (3D) printing makes it familiar in daily life, especially the fused deposition modeling 3D printers. The process planning of traditional flat layer printing includes slicing and path planning to obtain the boundaries and the filling paths for each layer along the vertical direction. There is a clear division line through the whole fabricated part, inherited in the flat-layer-based printed parts. This problem is brought about by the seam of the boundary in each layer. Hence, the purpose of this paper is to propose a novel helical filling path generation with the ideal surface-plane intersection for a rotary 3D printer.

The detailed algorithm and implementation steps are given with several worked examples to enable readers to understand it better. The adjacent points obtained from the planar slicing are combined to generate each layer's helical points. The contours of all layers are traversed to obtain the helical surface layer and helical path. Meanwhile, the novel rotary four-degree of freedom 3D printer is briefly introduced.

As a proof of concept, this paper presents several examples based on the rotary 3D printer designed in the authors’ previous research and the algorithms illustrated in this paper. The preliminary experiments successfully verify the feasibility and versatility of the proposed slicing method based on a rotary 3D printer.

This paper provides a novel and feasible slicing method for multi-axis rotary 3D printers, making manufacturing thin-wall and complex parts possible. To further broaden the proposed slicing method’s application in further research, adaptive tool path generation for flat and curved layer printing could be applied with a combination of flat and curved layers in the same layer, different layers or even different parts of structures.

Layered manufacturing (LM) is emerging as a new manufacturing technology that can enhance the scope of manufacturing. One of the essential tasks in LM is process planning. This paper defines, conceptualizes and reviews the literature in this emerging area. The paper concludes with future projections on the possible directions of research in this area.

The purpose of this paper is to design and develop a rotary three-dimensional (3D) printer for curved layer fused deposition modeling (CLFDM), and discuss some technical challenges in the development.

Some technical challenges include, but are not limited to, the machine design and control system, motion analysis and simulation, workspace and printing process analysis, curved layer slicing and tool path planning. Moreover, preliminary experiments are carried out to prove the feasibility of the design.

A rotary 3D printer for CLFDM has been designed and developed. Moreover, this printer can function as a polar 3D printer for flat layer additive manufacturing (AM). Compared with flat layer AM, CLFDM weakens the staircase effect and improves geometrical accuracy and mechanical properties. Hence, CLFDM is more suitable for parts with curved surfaces.

Double extruders have brought improved build speed. However, this paper is restricted to complex process planning and mechanical structures, which may lead to collisions during printing. Meanwhile, the rotation range of the nozzle is limited by mechanical structures, affecting the manufacturing capability of complex curved surfaces.

A novel rotary 3D printer, which has four degrees of freedom and double extruders, has been designed and manufactured. The investigation on the prototype has proved its capability of CLFDM. Besides, this rotary 3D printer has two working modes, which brings the possibility of flat layer AM and CLFDM.

While additive manufacturing via melt-extrusion of plastics has been around for more than several decades, its application to complex geometries has been hampered by the discretization of parts into planar layers. This requires wasted support material and introduces anisotropic weaknesses due to poor layer-to-layer adhesion. Curved-layer manufacturing has been gaining attention recently, with increasing potential to fabricate complex, low-weight structures, such as mechanical metamaterials. This paper aims to study the fabrication and mechanical characterization of non-planar lattice structures under cyclic loading.

A mathematical approach to parametrize lattices onto Bèzier surfaces is validated and applied here to fabricate non-planar lattice samples via curved-layer fused deposition modeling. The lattice chirality, amplitude and unit cell size were varied, and the properties of the samples under cyclic-loading were studied experimentally.

Overall, lattices with higher auxeticity showed less energy dissipation, attributed to their bending-deformation mechanism. Additionally, bistability was eliminated with increasing auxeticity, reinforcing the conclusion of bending-dominated behavior. The analysis presented here demonstrates that mechanical metamaterial lattices such as auxetics can be explored experimentally for complex geometries where traditional methods of comparing simple geometry to end-use designs are not applicable.

The mechanics of non-planar lattice structures fabricated using curved-layer additive manufacturing have not been studied thoroughly. Furthermore, traditional approaches do not apply due to parameterization deformations, requiring novel approaches to their study. Here the properties of such structures under cyclic-loading are studied experimentally for the first time. Applications for this type of structures can be found in areas like biomedical scaffolds and stents, sandwich-panel packaging, aerospace structures and architecture of lattice domes.

This work presents an experimental approach to study the mechanical properties of non-planar lattice structures via quasi-static cyclic loading, comparing variations across several lattice patterns including auxetic sinusoids, disrupted sinusoids and their equivalent-density quadratic patterns.

The purpose of this paper is to describe an innovative Parametric and Adaptive Slicing (PAS) technique to be used for generating material addition paths along three-dimensional surfaces.

The method is grounded on the possibility to generate layers starting from multiple reference surfaces (already available in the model or created on purpose). These are used for mathematically deriving a family of parametric surfaces whose shape and spacing (the layer thickness) can be tuned to get the desired aesthetic, technical and functional characteristics. The adhesion among layers is obtained guaranteeing a smooth transition among these surfaces.

The examples described in the paper demonstrate that the PAS technique enables the addition of the material along non-planar paths and, hence, the elimination of the staircase effect. In addition, objects printed using this technique show improved mechanical properties with respect to those printed using standard planar layers.

As the method allows a local control of the material addition/deposition, it can be used to design the mechanical behavior of the objects to be printed.

The technique proposed in this paper overcomes the limitations of currently available adaptive and curved layer slicing strategies, by introducing the possibility to generate layers with a non-constant thickness whose shape morphs smoothly from one layer to another.

With the development of 3D printing or additive manufacturing (AM), curved layer fused deposition modeling (CLFDM) has been researched to cope with the flat layer AM inherited problems, such as stair-step error, anisotropy and the time-cost and material-cost problems from the supporting structures. As one type of CLFDM, cylindrical slicing has obtained some research attention. However, it can only deal with rotationally symmetrical parts with a circular slicing layer, limiting its application. This paper aims to propose a ray-based slicing method to increase the inter-layer strength of flat layer-based AM parts to deal with more general revolving parts.

Specifically, the detailed algorithm and implementation steps are given with several examples to enable readers to understand it better. The combination of ray-based slicing and helical path planning has been proposed to consider the nonuniform path spacing between the adjacent paths in the same curved layer. A brief introduction of the printing system is given, mainly including a 3D printer and the graphical user interface.

The preliminary experiments are successfully conducted to verify the feasibility and versatility of the proposed and improved slicing method for the revolving thin-wall parts based on a rotary 3D printer.

This research is early-stage work, and the authors are intended to explore the process and show the initial feasibility of ray-based slicing for revolving thin-wall parts using a rotary 3D printer. In general, this research provides a novel and feasible slicing method for multiaxis rotary 3D printers, making manufacturing revolving thin-wall and complex parts possible.