Filament development for laser assisted FDM 3D printing

Abstract

In laser assisted FDM 3D printing, the previously extruded layer can be heated again using laser energy just before the next layer is deposited on it in order to increase the layer bonding quality. In this case, the 3D printing filaments must have a high absorption of near infrared light. Therefore, the main aim of this project is to determine the most suitable polymer additives for the most commonly used materials for filament FDM 3D printing, namely PLA and ABS. To achieve this aim, several project objectives were set. Relevant literature was reviewed in order to find the most suitable polymer additives which can be added to PLA and ABS to increase the near infrared light absorption. From literature, the chosen polymer additives were; graphite, CNT and luniri1. a filament maker was used to produce PLA and ABS filaments with these chosen additives. These filaments were characterised using polymer characterisation technique in order to fully understand the effects of the additives on the filament. NIR testing was also done to determine which additives are suitable for promoting NIR absorption. The most suitable additive was chosen to be graphite due to its high NIR absorption properties and price. The produced filaments with graphite additives were used to 3D print shear and tensile specimen for testing with the aim of investigation the resulting material properties, mainly the inter-layer bonding strength of the printed parts. A fibre couple laser diode was integrated within the printing head to heat up the previously extruded layer. With the laser heating, the inter-layer bonding showed direct increase in the mechanical properties. With the addition of localised laser heating, an increase of 14.5% in the elastic modulus and an increase of 27.8% in the tensile strength of the printed parts were noticed. An increase in the crystallinity degree of 14.7% was also observed. This showed that laser heating is an effective method of increasing the inter-layer bonding within FDM 3D printed parts. This method significantly increases the inter-layer bonding strength, and therefore the strength and durability of the printed part. Hence, this 3D printing technology can be adopted by various sectors, such as aerospace and healthcare.