Direct coupling of fixed screw extruders using flexible heated hoses for FDM printing of extremely soft thermoplastic elastomers (original) (raw)
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Rapid Prototyping Journal, 2018
Purpose This paper aims to target to print functionally gradient materials (FGM) devices made of immiscible polymers in multi-material fused deposition modelling (FDM) systems. The design is intended to improve adhesion of dissimilar thermoplastics without the need for chemical compatibilization so that filaments from many different sources can be used effectively. Therefore, there is a need to invent an alternative solution for printing multiple immiscible polymers in an FDM system with the desired adhesion. Design/methodology/approach In this study, the authors have developed a bi-extruder for FDM systems which can print two thermoplastics through a single nozzle with a static intermixer to enhance bonding between input materials. The system can also change the composition of extrudates continuously. Findings The uniqueness of this extruder is in its easy access to the internal channel so that a static intermixer can be inserted, enabling deposition of mechanically interlocked ext...
Mechanics of Materials, 2021
This work presents the first experimental characterization of the mechanical and thermomechanical properties of a soft 3D printed thermoplastic styrenic elastomer. The tested specimens were obtained by Fused Deposition Modeling with a modified commercial 3D printer. Three different deposit strategies (deposit angle of 0 • , 45 • and ±45 •) have been tested. Scanning electronic Microscopy was used for analyzing the microstructure of the printed specimens. The specimens were tested under two different uniaxial tensile loadings. The first one consists in applying several sets of load-unload cycles at three increasing strain levels. The second one corresponds to one load-unload cycle at different loading rates. For both tests, the temperature variations were characterized by means of infrared thermography. Results showed that the printing strategy does not have a significant effect on the mechanical response, including the softening, the hysteresis loop and the permanent set, but has an effect on its thermal response. Differences found in terms of self-heating due to intrinsic dissipation clearly show that the deposit angle influences the viscosity of the specimens.
Journal of Dynamic Systems, Measurement, and Control, 2019
Polymer three-dimensional (3D)-printing has been commercialized rapidly during recent years; however, there remains a matter of improving the manufacturing speed. Screw extrusion has a strong potential to fasten the process through the simultaneous operation of the filament production and the deposition. This paper develops a control algorithm for screw extrusion-based 3D printing of thermoplastic materials through an observer-based output feedback design. We consider the thermodynamic model describing the time evolution of the temperature profile of an extruded polymer by means of a partial differential equation (PDE) defined on the time-varying domain. The time evolution of the spatial domain is governed by an ordinary differential equation that reflects the dynamics of the position of the phase change interface between polymer granules and molten polymer deposited as a molten filament. The steady-state profile of the distributed temperature along the extruder is obtained when the...