Printing with mechanically interlocked extrudates using a custom bi-extruder for fused deposition modelling

Abstract

Purpose This paper aims to target to print functionally gradient materials (FGM) devices made of immiscible polymers in multi-material fused deposition modelling (FDM) systems. The design is intended to improve adhesion of dissimilar thermoplastics without the need for chemical compatibilization so that filaments from many different sources can be used effectively. Therefore, there is a need to invent an alternative solution for printing multiple immiscible polymers in an FDM system with the desired adhesion. Design/methodology/approach In this study, the authors have developed a bi-extruder for FDM systems which can print two thermoplastics through a single nozzle with a static intermixer to enhance bonding between input materials. The system can also change the composition of extrudates continuously. Findings The uniqueness of this extruder is in its easy access to the internal channel so that a static intermixer can be inserted, enabling deposition of mechanically interlocked extrudates composed of two immiscible polymers. Without this intermixer, the bi-extruder extrudes with simple side-by-side co-extrusion having no mechanical interlocking. The bi-extruder was characterized by printing objects using pairs of materials including polylactic acid, acrylonitrile butadiene styrene and high impact polystyrene. Microscope images of the cross-sections of the extrudates confirm the ability of this bi-extruder to control the composition as desired. It was also found that the mechanically interlocked extrudates composed of two immiscible polymers substantially reduces adhesion failures within and between filaments. Originality/value In this study, the first-ever FDM extruder with a mechanical blending feature next to the nozzle has been designed and used to successfully print FGM objects with improved mechanical properties.

Review on Additive Manufacturing of Multi-Material Parts: Progress and Challenges

“…The development and advancement of the modern technologies make it possible to manufacture multiple-material parts in a single manufacturing process. Khondoker et al [63] designed a static mixer inside the extrusion nozzle head of the FFF machine, which aimed to help mix the two different polymers during the deposition process. The authors revealed that intermixed specimens could increase the interface strength of FFF-made parts.…”

“…Different materials for fabricating multi-material AM parts have been documented and studied in the literature [61,63,106]. Zhangwei et al [107] provided a review on various ceramic materials and their properties and applications.…”

“…Apart from interface issues, one must consider the material selection, design and manufacturing aspects of MMAM issues. The main challenge is to select appropriate materials, understanding the composition and optimal distribution of materials inside the fabricated parts [63]. Since mixing materials with variable and non-uniform properties are complex, background information related to material characteristics, properties, chemical composition, and manufacturing constraints are necessary prior to processing these materials [181][182][183].…”

Scientometric Analysis and Systematic Review of Multi-Material Additive Manufacturing of Polymers

“…In addition, the SLTAT method can be easily applied to existing multi-material 3D printers without adding additional heating equipment or post-processing steps ( Figure 8 b). For the purpose of improving adhesion of dissimilar thermoplastics without the need for chemical compatibilization, a bi-extruder head for FDM systems capable of printing two filaments through a single nozzle was developed [ 90 ]. This extruder’s unique feature is its convenient access to the internal channel, which allows the insertion of a static inter-mixer, thus enabling the deposition of mechanically interlocked extrusions consisting of two non-combustible polymers.…”

Advances in Coaxial Additive Manufacturing and Applications

“…Khondoker et al. [ 28,29 ] developed a custom‐made thermoplastic tri‐extruder compatible with FFF printers (see Figure a). The printing head has two angled input channels made of a metal alloy (brass – C36000) for feeding thermoplastic materials and a third one in the middle, made of a reusable stainless‐steel dispensing needle (22G) assigned to the extrusion of a central fluid core.…”