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Abstract Additive manufacturing (AM), also known as 3D printing, has significantly advanced in recent years, especially with the introduction of multifunctional 3D-printed parts. AM fabricated monolith has multiple material capabilities, thus various functionalities are well-perceived by the manufacturing communities. As an example, a traditional fused filament fabrication (FFF) 3D printer fabricates multi-material thermoplastic parts using a dual extrusion system to increase the functionality of the part including variable stiffening and gradient structures. In addition to the multiple thermoplastic feedstocks in a dual extrusion system, multifunctional AM can be achieved by embedding electronics or reinforcing fibers within the fabricated thermoplastic parts, which significantly impacts the rapid prototyping of hybrid components in manufacturing industries. State-of-the-art techniques such as coextrusion systems, ultrasonic welding tools, and thermal embedding tools have been implemented to automate the process of embedding conductive material within the 3D-printed thermoplastic substrate. The goal of this tool development effort is to embed wires within 3D 3D-printed plastic substrate. This research consisted of developing a wire embedding tool that can be integrated into an FFF desktop 3D printer to deposit conductive as well as resistive wires within the 3D-printed thermoplastic substrate. By realizing the challenges for discrete materials interaction at the interface such as nichrome wires and Acrylonitrile Butadiene Styrene (ABS) plastics and polylactic acid (PLA), the goal of this tool was to immerse wire within ABS and PLA substrate using transient swelling mechanisms under non-polar solvent. A proof-of-concept test stands with a wire feed system and the embedding wheel was first designed and manufactured using 3D printing to examine if a traditional roller-guided system, primarily used for plastic extrusion, would be sufficient for wire extrusion. The development of the integrated wire embedding tool was initiated based on the success of the proof-of-concept wire extrusion system. The design of the integrated wire embedding tool consisted of three sub-assemblies: wire delivery assembly, wire shearing assembly, and swivel assembly. The wire delivery assembly is responsible for feeding the wire towards the thermoplastic using the filament delivery system seen within FFF printers. For the wire shearing mechanism, a cutting Tungsten carbide blade in conjunction with a Nema-17 external stepper motor was used to shear the wire. For the wire embedding assembly, a custom swivel mount was fabricated with a bearing housing for a ball bearing that allowed for a 360-degree motion around the horizontal plane. A wire guide nozzle was placed through the mount to allow for the wire to be fed down into a brass embedding wheel in a tangential manner. Additionally, the solvent reservoir was mounted such that an even layer of solution was dispensed onto the thermoplastic substrate. Through this tool development effort, the aim was to develop technologies that will enable 3D printing of wire-embedded monolith for various applications including a self-heating mold of thermoset-based composite manufacturing as well as smart composites with embedded sensors.
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3D printing using powder melt extrusion
Additive manufacturing promises to revolutionize manufacturing industries. However, 3D printing of novel build materials is currently limited by constraints inherent to printer designs. In this work, a bench-top powder melt extrusion (PME) 3D printer head was designed and fabricated to print parts directly from powder-based materials rather than filament. The final design of the PME printer head evolved from the Rich Rap Universal Pellet Extruder (RRUPE) design and was realized through an iterative approach. The PME printer was made possible by modifications to the funnel shape, pressure applied to the extrudate by the auger, and hot end structure. Through comparison of parts printed with the PME printer with those from a commercially available fused filament fabrication (FFF) 3D printer using common thermoplastics poly(lactide) (PLA), high impact poly(styrene) (HIPS), and acrylonitrile butadiene styrene (ABS) powders (< 1 mm in diameter), evaluation of the printer performance was performed. For each build material, the PME printed objects show comparable viscoelastic properties by dynamic mechanical analysis (DMA) to those of the FFF objects. However, due to a significant difference in printer resolution between PME (X–Y resolution of 0.8 mm and a Z-layer height calibrated to 0.1 mm) and FFF (X–Y resolution of 0.4 mm and a Z-layer height of 0.18 mm), as well as, an inherently more inconsistent feed of build material for PME than FFF, the resulting print quality, determined by a dimensional analysis and surface roughness comparisons, of the PME printed objects was lower than that of the FFF printed parts based on the print layer uniformity and structure. Further, due to the poorer print resolution and inherent inconsistent build material feed of the PME, the bulk tensile strength and Young’s moduli of the objects printed by PME were lower and more inconsistent (49.2 ± 10.7 MPa and 1620 ± 375 MPa, respectively) than those of FFF printed objects (57.7 ± 2.31 MPa and 2160 ± 179 MPa, respectively). Nevertheless, PME print methods promise an opportunity to provide a platform on which it is possible to rapidly prototype a myriad of thermoplastic materials for 3D printing.
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- Award ID(s):
- 1803644
- PAR ID:
- 10167518
- Date Published:
- Journal Name:
- Additive manufacturing
- Volume:
- 29
- Issue:
- 1
- ISSN:
- 2473-604X
- Page Range / eLocation ID:
- 100811
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.addma.2019.100811
