PSI - Issue 28

Manuel Sardinha et al. / Procedia Structural Integrity 28 (2020) 358–363

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Manuel Sardinha et. Al / Structural Integrity Procedia 00 (2019) 000–000

1. Introduction Additive manufacturing technologies (AM) have the potential to transform industries and reshape manufacturing. By shortening product development steps and considerably reducing components time to market, they impose a need to rethink distribution channels and manufacturing supply chains. In opposition, the design freedom allowed by the additive processes, endogenous of AM conceptual methodology, results in increased product customization and product variability, enforcing, at times, an increased process complexity [1-4]. These disruptive characteristics are being limited by surface roughness and geometrical accuracy of parts, manufacturing speed, scalability, and low interlaminar strength (ILS), among others [2-5]. Material extrusion affordability, relative process simplicity and practicality make it a common tool in experimental mechanics, here, heated feedstock plastic filament passes through a nozzle tip and is then deposited in a build platform, creating tailored structures layer by layer [1, 3, 6]. The manufacture of parts through multiple independent and collaborative extrusion modules emerges as a potential solution to overcome the limitations of speed, cost, and scalability of the established AM processes [7, 8]. By allowing a collaborative manufacturing between extrusion modules, the size of built parts can increase without compromising production time and maintaining geometrical accuracy [9-11]. The existence of multiple independent extrusion modules imposes the existence of intersections areas in parts and these intersections can be better understood as seams. In this work, authors take advantage of a dedicated manufacturing apparatus [9] and slicer software [10] to evaluate the influence of seams in the mechanical properties of PLA dog bone type samples produced with two independent extrusion modules. 2. Materials and Methods 2.1. Materials The material chosen for the study is poly-lactic acid (PLA), a biodegradable thermoplastic polymer which derives from renewable biomass and is used in numerous fields of application from packaging and prototypes to prosthesis and medical devices [1, 5]. Literature reports state that, when processed by material extrusion, its tensile strength can vary between 10 and 60 MPa depending on process parameters, namely build orientation, layer height and extrusion temperature [4, 5]. Two spools of white PLA filament were used in this study. The spools have a consecutive manufacturing lot number and their diameter is 1.75.

2.2. Manufacturing

Fig. 1. Material extrusion apparatus with two modules manufacturing a specimen.