Expansion of the Fused Filament Fabrication (FFF) Process Through Wire Embedding, Automated Cutting, and Electrical Contacting

Additive manufacturing is establishing new forms of manufacturing processes to produce functional parts. It is thus seen as a hope for a shift towards decentralised production and the associated positive effects on the environment. The most widespread process, Fused Filament Fabrication, already impresses with a large variety of materials and the possibility of including non-polymeric additives as fibre materials. To support this development, this paper describes a form of wire implementation as an add-on for existing FFF systems, that can be realised without major changes to hardware or software. The aim is to integrate electrical functions directly into the component - in one manufacturing process. The process is based on a hybrid material made of PLA with a copper core, which was developed in advance. Within this work, two retrofittable units for FFF printers are described, which cut a continuous wire with a diameter of <inline-formula> <tex-math notation="LaTeX">$0.2~mm$ </tex-math></inline-formula> embedded in a polymer in a fully automatic manner. Furthermore, two thermal contacting processes are presented, which make it possible to contact the embedded wire via the heated extruder nozzle and metallic inserts. Thereby, a best contact resistance of 0.009 ± <inline-formula> <tex-math notation="LaTeX">$0.0023~\Omega$ </tex-math></inline-formula> (50% confidence interval) could be achieved for a screw contact. For a plug-in or solder contacts, a contact resistance of 0.059 ± <inline-formula> <tex-math notation="LaTeX">$0.028\Omega$ </tex-math></inline-formula> (50% confidence interval) was realised. In terms of process technology, the wire deposition within the plastic structure could be reliably realised at printing speeds of <inline-formula> <tex-math notation="LaTeX">$10~mm/s$ </tex-math></inline-formula> on straight sections and <inline-formula> <tex-math notation="LaTeX">$1~mm/s$ </tex-math></inline-formula> in curves with a radius of <inline-formula> <tex-math notation="LaTeX">$5~mm$ </tex-math></inline-formula>. The developed process was successfully validated using a functional demonstrator. The functional sample can be selectively heated to the glass transition temperature and reversibly formed. In summary, the developed methods are suitable for cost-effectively expanding existing FFF systems to integrate electrical functions during the 3D printing process.

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