FusedDepositionMaterial 3DPrinting Procedure and Algorithm Avoiding Use of Any Supports The threedimensional printing of complex shapes without using supporting structures is the most attractive factor of merit in current additive manufacturing because it allows to drastically reduce printing time, and ideally nullify postprocessing and waste material. In this work, we present an innovative procedure and algorithm (Print on Air, PoA) for additive manufacturing that, relying on sensing systems embedded into the threedimensional (3D) printer (e.g., temperature and speed sensors), aims at generating a printing sequence capable of a selfsustaining bridge and overhang structures. This feature was achieved by splitting the actual floating area of the layer where the aforementioned structures are in many subsections. Each is generated with a negligible floating surface and printed in a welldetermined sequence with accurate temperature and speed profiles. Therefore, each subsection is formed without the need for scaffolding, simultaneously acting as a supporting structure for the following subsection. The array of subsections constitutes the actual bridge or overhang structure. The proposed method can be used for any object, including very long bridges or convex surfaces. The revolutionary method is here reported and evaluated in order to show its applicability in any condition. Although the study was conducted in a Fused Deposition Material (FDM) environment, it can certainly be adapted to other manufacturing environments with adequate modifications.

Material characterization and precise finite element analysis of fiber reinforced thermoplastic composites for 4D printing Abstract   Fourdimensional (4D) printing, a new technology emerged from additive manufacturing (3D printing), is widely known for its capability of programming postfabrication shapechanging into artifacts. Fused deposition modeling (FDM)based 4D printing, in particular, uses thermoplastics to produce artifacts and requires computational analysis to assist the design processes of complex geometries. However, these artifacts are weak against structural loads, and the design quality can be limited by less accurate material models and numerical simulations. To address these issues, this paper propounds a composite structure design made of two materials  polylactic acid (PLA) and carbon fiber reinforced PLA (CFPLA)  to increase the structural strength of 4D printed artifacts and a workflow composed of several physical experiments and series of dynamic mechanical analysis (DMA) to characterize materials. We apply this workflow to 3D printed samples fabricated with different printed parameters to accurately characterize the materials and implement a sequential finite element analysis (FEA) to achieve accurate simulations. The accuracy of deformation induced by the triggering process is both computationally and experimentally verified with several creative design examples and is measured to be at least 95%, with a confidence interval of     (  0  .  972  ,  0  .  985  )    . We believe the presented workflow is essential to the combination of geometry, material mechanism and design, and has various potential applications.