M.T. Mastura - Implementation and Evaluation of Green Materials in Technology Development: Emerging Research and Opportunities

A Review

• Mastura Mohammad Taha
  Universiti Teknikal Malaysia Melaka, Malaysia
• Ridhwan Jumaidin
  Universiti Teknikal Malaysia Melaka, Malaysia
• Nadlene M. Razali
  Universiti Teknikal Malaysia Melaka, Malaysia
• Syahibudil Ikhwan Abdul Kudus
  Universiti Teknikal Malaysia Melaka, Malaysia

ABSTRACT

Fused filament fabrication (FFF) has been developed in additive manufacturing technology as a fast and simple manufacturing process in product design. Advantage of the process such as flexibility in terms of the materials employment has attracted many researchers to develop new materials for the feed stock filament in the heat extrusion process of FFF. Green materials or bio-composites materials have been found in FFF and successfully commercialized in the market. However, a deep research should have been performed prior the application because of the unique characteristics of the material itself. The challenge for the researchers to develop bio-composite materials as the filament in FFF technology is to determine the right composition of the composites with the right thermal, mechanical, and rheological properties. Therefore, in this study, a review has been conducted to highlight the important requirements of the process and materials. Green materials such as bio-composites have a great potential in the FFF technology and could improve the sustainability impact.

INTRODUCTION

Dematerialization is defined as reduction in quantity of materials used and/or the quantity of waste generated (Cleveland & Ruth, 1998). This principle included in sustainable development where it could reduce waste materials and environmental effects. Technology in manufacturing process has been developed into several techniques that support sustainability with dematerialization principle. One of the current manufacturing process technologies that optimize the usage of materials is additive manufacturing. Additive manufacturing technologies process the 3D model data and joining the materials layer upon layer according to the desired shape and geometry. This technique is opposed the principle in traditional machining where the materials are removed part upon part for desired shape and generates material waste after the process. Consequently, waste management technologies are required and consume more energy and cost. Hence, additive manufacturing is considered as one of the initiative for supporting sustainable product development.

Additive manufacturing technologies include powder bed fusion (polymers and metals, e.g.: Laser Sintering, Laser Melting), binder jetting, vat polymerization (e.g.: Stereolitography), material jetting and material extrusion (e.g.: Fused Filament Fabrication). Among these technologies, Fused Filament Fabrication or FFF (commonly referred to as Fused Filament Fabrication or FFF by Stratasys) is found to be compatible with composite materials that filled with natural s (Bikas, Stavropoulos, & Chryssolouris, 2016). The process utilizes materials with lower melting point by extruding the molten filament through movable circular nozzle. Generally, the filament is heated up to 1oC above its melting point and solidifies right after extrusion. In comparison with the other types of additive manufacturing technologies, FFF requires less cost with high speed of production due to its simplicity (Fril & Rotaru, 2017). However, poor surface finish is produced and secondary manufacturing process is needed for the good quality of product finishing.

What Is Fused Filament Fabrication (FFF)?

Fused Filament Fabrication (FFF) is a type of material extrusion technology, in which, a process where a string of thermoplastic filament is dispensed through a heated nozzle or orifice and melting it in the process, in X, Y and Z (ISO/ASTM International, 2016). The principle of FFF is based on chemistry, thermal energy and layer manufacturing technology (Chua & Leong, 2015). The FFF printer deposits the filament material on a horizontal build platform, where the material cools down, and the material laying process repeats layer-by-layer until it forms a solid, three-dimensional part. The first commercialised FFF system that used material extrusion process was developed and trademarked by Stratasys Ltd. (Caffrey et al., 2016). Figure 1 shows a diagrammatic illustration of FFF process.

Figure 1. Principle of FFF (Additively, 2017)

FFF machines are operated automatically by the printers hardware and firmware. There are four primary stages of how FFF works, they are (a) the generation of digital 3D model from computer-aided design (CAD) software, (b) converting the 3D model to a tetrahedral mesh file, generally Standard Triangle Language (STL) format were used, (c) splitting the tetrahedral mesh into layers and producing the tool-path using a program known as a slicer, and (d) using computer numerical control (CNC) to move the extrusion head to produce parts (Steuben et al., 2015). Figure 2 illustrates the steps of FFF printing process.

Figure 2. The FFF printing process (Steuben et al., 2015)

To get an accurate printed part, FFF system, where they are also known as desktop 3D printers, allow users to adjust several process parameters such as layer height, shell thickness, part infills, print speed, temperature of the nozzle and the build platform, and the control of the cooling fan. The most important printer characters that one need to know is the size of build platform and layer height. FFF system offers variety of build platform size, ranging from 100x100x100 to 1000x1000x1000 mm. However, on average, desktop 3D printers usually offer around 200x200x200 mm build size. Layer height has significant effects on the printed part where it will determine the smoothness of part surface. A typical layer height is generally between 50 to 400 microns (0.05 to 0.4 mm). Different printers offer different maximum resolutions of layer height. Smaller layer height and nozzle diameters produces smoother surfaces and make the part produced more precise.

Printed part sometimes is at risk of warping and shrinkage. This is due to temperature variations surrounding the build part. To prevent this from happen, some of the solution is to print raft and brim at the base layer of the part to make the printed part more stable and has strong foundation during build up process. Thermoplastic materials such as ABS, PLA and PA are widely used because it has good mechanical properties, good temperature resistance, easy to print with, and suitable for end-use prints (Redwood et al., 2018). Users also need to consider support structure when there is overhangs and bridges in the part design. Design features like angled walls and vertical edges are some of the examples of overhangs. Any design features that overhangs is below than 45 degrees require support structures.

Application of FFF system for industrial and public use has been raised dramatically in past years as the rapid production of physical models is the key driven for the FFF market. Study shows that majority of 3D printing users, including business and individuals, owned FFF 3D printers, which contributes 75% of total market purchases and ownership (see Figure 3). The reason behind is mainly due to the price of FFF system because it is cheaper as well as easier to handle to compare with other type of 3D printing machines. On the other hand, with the usage trends of metal 3D printing increasing, the use of plastic materials remained in the lead as the most material used by the users (see Figure 4). Plastic still have a lot of advantages as it is the most convenient material for making prototypes and part production. Based on this, it can be seen that FFF system is still the first 3D printing technology that users mostly used.