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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. 

In the composite manufacturing industry, production tooling commonly requires preheating for molding. The most commonly used method for preheating is indirect heating, in which heat is transferred from heat sources to the materials by convection and radiation. However, in the case of direct heating, in which heat is generated directly within a material by passing an electric current through it, the tools are preheated through joule heating. In this project, we manufactured a self- heating mold for direct heating. The manufacturing process involves 3D printing self-heating tooling, in which resistive wires are embedded into the tool at every so number of layers using a programmed 3D printer. Thermal characterizations were performed on the self-heating tool and a thermoset composite layup process was performed to study the suitability of the mold. 

This research evaluates and characterizes the thermal and physical characteristics of thermoplastic specimens embedded with resistive wire using a Fused Filament Fabrication 3D printer. The specimens were manufactured through a novel approach “Pause and Go” in additive manufacturing for embedding resistive wires into a 3D printed thermoplastic substrate using a custom-built wire embedding tool integrated into a commercially available desktop scale Independent Dual Extruder (IDEX) printer. Wire- embedded test specimens were produced via 3D printing using Polylactic Acid. The 26-gauge nichrome wire was embedded in the top substrate and continued the printing to fully embed the wires. Thermal testing was carried out and observed steady-state temperatures after 30 minutes. The wire pulls tests characterized the bonding strength of the wire and substrate.