Abstract
The filament is the most widespread feedstock material form used for fused deposition modeling printers. Filaments must be manufactured with tight dimensional tolerances, both to be processable in the hot-end and to obtain printed objects of high quality. The ability to successfully feed the filament into the printer is also related to the mechanical properties of the filament, which are often insufficient for pharmaceutically relevant excipients. In the scope of this work, an 8 mm single screw hot-end was designed and characterized, which allows direct printing of materials from their powder form and does not require an intermediate filament. The capability of the hot-end to increase the range of applicable excipients to fused deposition modeling was demonstrated by processing and printing several excipients that are not suitable for fused deposition modeling in their filament forms, such as ethylene vinyl acetate and poly(1-vinylpyrrolidone-co-vinyl acetate). The conveying characteristic of the screw was investigated experimentally with all materials and was in agreement with an established model from literature. The complete design information, such as the screw geometry and the hot-end dimensions, is provided in this work.
Highlights
Fused deposition modeling (FDM) is a widespread manufacturing technique in numerous pharmaceutical and medical applications, such as solid dosage forms [1,2], implants [3,4] and tissue engineering [5,6]
The hot-end was designed as a single-screw extruder for a custom FDM printer [19]
The presented single-screw extrusion hot-end processes material is used in powder form and does not require an intermediate filament
Summary
Fused deposition modeling (FDM) is a widespread manufacturing technique in numerous pharmaceutical and medical applications, such as solid dosage forms [1,2], implants [3,4] and tissue engineering [5,6]. The feedstock material is provided in filament form and is usually produced by hot-melt extrusion in a preceding step [8]. In this way, filaments consisting of pharmaceutical excipients and active pharmaceutical ingredients can be manufactured in various combinations and compositions [9,10]. The range of filaments useable in the printing process is limited by the geometrical and mechanical properties of the individual filaments [11]. The nominal filament diameter is usually stored in the printer software to determine the filament feed velocity required to obtain a specific extrudate mass flow. The subsequent pushing process into the hot-end frequently causes flexible filament materials to buckle and brittle filament materials to fracture [15]
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