Additive Manufacturing (AM) is the best choice to fulfill the fourth industrial revolution, as it delivers complex and customized products with great freedom in design in a very short time, reducing the production cost and shortening the development cycle[1]. Stereo-lithography (SLA) is the first technique that AM had started with, which is a liquid-based raw material technique. Later on, many techniques had been invented varying in the raw material from liquid to powder and solid[2]. All AM techniques use three-dimensional computer-aided designs (CAD) to produce –layer by layer– three-dimensional products by selectively adding materials, with variety in the materials being used. FDM, solid-based AM technique, is the most common and widely used technique due to its simplicity and modesty in price as it utilizes low-cost polymers only[2, 3]. FDM feeds thermoplastic filament into a heating chamber until it reaches a semi-liquid state, extrudes it through a nozzle above its melting point, then depositing it on the printing platform in specified positions according to the G-code generated by the machine’s software[4]. FDM printed parts have been in use in many fields like rapid prototyping, building, healthcare devices and tools, motor drives, and aerospace components[5]. But due to the nature of the FDM technique, it experiences some drawbacks; one of them is the limitation in mechanical properties. This limitation is due to the weak and non-homogenous bonding between the corresponding layers building up the part and also between the roads building the layer itself. Also since the cooling and heating rates in the FDM process are unstable there would be uncontrolled shrink and defects in the microstructure[2, 6].
Many studies had been performed to overcome the pre-mentioned problems, covering different materials that are currently used in FDM (ABS, PLA, PA, NYLON, etc.). Many studies have considered printing parameters as important indices for product quality. They studied the influence of printing orientation, speed, raster angle, infill pattern, nozzle temperature and layer height on the mechanical properties of the printed parts[7, 8]. Table 1, summaries the studies done by researchers on 3D printed ABS parts applying different printing parameters.
Table 1
Previous work on ABS printed specimens
Authors | Parameters and (levels) | Outputs |
Samykano et al. [9] | Printing speed (30 mm/s), printing temperature (220\(℃\)), bed temperature (110\(℃\)), infill pattern (lines), layer height (0.35, 0.4, and 0.5 mm) and raster angle (45\(^\circ\), 55\(^\circ\), 65\(^\circ\)). | \(\sigma\)t Et Toughness |
Rangisetty et al. [10] | Layer height (0.2 mm), extruder temperature (240\(℃\)), bed temperature (90\(℃\)), print speed (55 mm/s) and infill pattern (line, Concentric, Triangular, and Honeycomb). | \(\sigma\)t Et \(\sigma\)f Ef |
Bamiduro et al. [11] | Orientation (0\(^\circ\)/90\(^\circ\), -45\(^\circ\)/45\(^\circ\)) | \(\sigma\)t |
Meng et al. [6] | Layer height (0.1 mm), orientation (vertical, ,horizontal) ,printing speed (40 mm/s), extruder temperature (235\(℃\)), bed temperature (80\(℃\)), composition (ABS,ABS/SiO2, ABS/MMT, ABS/MWCNTs, ABS/CaCO3 ) | \(\sigma\)t \(\sigma\)f Ef |
Coogan et al. [12] | Bed temperature (100\(℃\), 125\(℃\), 150\(℃)\), print speed (1000, 2000, 4000) mm/min, layer height (0.15,0.3,0.45 mm), nozzle temperature (230 \(℃\), 255\(℃\), 280\(℃\))\(\), fiber width (0.4, 0.6, 0.8 mm) | Bond strength Longitudinal strength |
Huang et al.[13] | Layer thickness(0.1, 0.2, 0.3 mm), raster angle (45\(^\circ\)/-45\(^\circ\),30\(^\circ\)/-60\(^\circ\),0\(^\circ\)/90\(^\circ\)), printing speed (20, 40, 60 mm/s), building orientation (horizontal, lateral, vertical), bed temperature (80\(℃\)), printing temperature (235\(℃)\) | \(\sigma\)t \(\sigma\)f Impact strength |
Koch et al.[14] | Print temperature (250\(℃\)), bed temperature (210\(℃\)), layer height (0.2 mm), raster angle (0\(^\circ\),-45\(^\circ\)/45\(^\circ\),90\(^\circ\)), travel speed (2000 mm/min), solidity ratio (0.6-1) | \(\sigma\)t |
Cantrell et al. [15] | Layer height (0.1 mm), printing temperature (235\(℃\) ), bed temperature (105\(℃\)), orientation (Horizontal, lateral, vertical ), raster angle (-45\(^\circ\)/45\(^\circ\),0\(^\circ\)/90\(^\circ\), 30\(^\circ\)/-60\(^\circ\),15\(^\circ\)/-75\(^\circ\)) | \(\sigma\)t |
Rayegani and. Onwubolu [16] | Orientation (0\(^\circ\),90\(^\circ\)), raster angle (0\(^\circ\),45\(^\circ\)), raster width (0.2032,0.558 mm), air gap (0.558,−0.00254 mm) | \(\sigma\)t |
Other studies adopted the potential of improving physical and mechanical properties of the raw material itself. Nanoparticles were prepared and mixed with the printing filament to produce a new one[6, 17–19]. Some research focuses on improving the overall mechanical properties of the 3D printed part by decreasing its anisotropy or increasing its isotropic behavior[20, 21].They replaced the thermoplastic polymers that results in poor chemical and thermal properties by two-component epoxy resin[20],epoxy resin poses good chemical and physical properties and gives high-strength bonding, with light weight structures withstanding high static loads[22, 23]. Filippova et al. [21] impregnated ABS 3D printed samples in epoxy resin compound with different hardeners. 142% and 133% were achieved as an improvement in ultimate tensile strength depending on the hardener type. Instead of impregnation, Belter and Dollar [24] injected epoxy resin through ABS flexural specimens. This results in improving the overall part stiffness and strength by up to 25% and 45% respectively. Moreover, Jiang et al. [20] used epoxy as the main raw material in FDM technique to get the best use of its mechanical properties and print products can be used in harsh conditions. Tensile specimens were printed of a mixture of only epoxy and CNT giving a tensile strength of 55 MPa.
In this paper, ABS tensile specimens are printed with printing parameters based on the survey presented in Table1. A comparison between the results of many previous studies is held to decide on the best parameters to print with. Also using these printing parameters, another tensile specimens are printed to test a new filling technique. This technique is a post processing technique aims to improve the mechanical properties, reduce cost and weight. Hence the parts are printed with inner voids which reduces the part weight, time and cost of printing in turn. Then these voids are injected with low-cost, less dense resin which poses higher mechanical properties. To make the part sparse inside, voids could be designed and located precisely during design stage by CAD software, or slicing software manage these process through infill density parameter [25]. In this study, the parts are sparse by slicing software, three infill density are printed (20%, 40% and 60%) and injected by epoxy resin that is less in price by 91%. The infill pattern chosen is gyroid pattern to let the resin to spread entire the whole part. Tensile tests and morphology analysis are performed to investigate the improvement of this technique.