Development of a Reconfigurable Multi-Material Polymer Based-Extrusion System

Abstract

Fused deposition modelling has become one of the most prominent additive manufacturing processes for the fabrication of thermoplastic polymers. It is generally used for rapid prototyping and industrial batch production, and due to its capabilities to fabricate a wide range of materials, FDM is gaining high popularity, especially for producing complex geometries using multi-material 3D printing. Extensive research has been done on optimizing and improving the mechanical properties of thermoplastic materials, but its relationship linking the equipment itself with multi-materials and part designs leads to a gap between different stages of this extrusion technology. From this viewpoint, this thesis focuses on the FDM technique and presents a system developed at the Laboratory of Intelligent Manufacturing, Design, and Automation (LIMDA) for multiple material thermoplastic polymers. The system is capable of depositing in any given layer or geometry, up to three different types of materials. This system is intended to handle a variety of multi-material print head nozzles based on the AM process requirement. Multi-material 3D printing and process parameters optimization using multiple extruders are considered one of the main challenges for the FDM technique; therefore, a comparison of two modes: multi-material single mixing nozzle and multi-material multiple nozzles, linking the technology with the mechanical properties is presented. Tensile testing specimens were printed in two different scenarios to validate the comparison: (1) multi-material multi-layered section printed using a multi in-out single mixing nozzle and (2) multi-material multi-layered section printed using a multiple extrusion nozzle within the same carriage. Both modes followed a rectilinear infill pattern and different material combinations. The material combinations implemented included ABS-HIPS, ABS-PLA, PLA- HIPS, and PLA-HIPS-ABS. A behavioural study is evaluated on the mechanical properties of these materials. The results provide a tool for selection on which type of mode is considered suitable for maximizing efficiency and performance to fabricate a multi-material 3D printed product. Besides, the mechanical properties of materials produced through FDM lack of strength, which restricts the production of high-level multi-functional components. Standard 3D printing materials are typically used for conceptual parts rather than functional parts. The fabrication of a specimen with a sandwich material combination using PLA, ABS, and HIPS through the filament-based extrusion process can demonstrate an improvement in its properties. This thesis also aims to assess among these common thermoplastic materials, the best material sandwich-structured arrangement design, to enhance the mechanical properties of a part and to compare the results with the homogeneous materials selected. The samples were subjected to tensile testing to identify the tensile strength, elongation at break, and Young’s modulus of each material combination. The experimental results demonstrate that applying the PLA-ABS-PLA sandwich arrangement leads to the best mechanical properties between these material combinations. This study enables users to consider sandwich structure designs as an alternative to manufacture multi-material components using conventional and low-cost materials.