Development of Thermoplastic Composites for Fdm-Type 3d Printers

Аннотация

FDM – type 3D printing has greatly increased in recent years but there is still a demand for stronger and stiffer materials. The objective of this work is to extrude and test various types of thermoplastic composite filament to be used for 3D printing. ABS thermoplastics was combined with various lengths of fiberglass. Using these thermoplastic composites several specimens were prepared per ASTM D638 by compression molding and tested. The fiberglass was introduced to increase mechanical strength and stiffness of the thermoplastic filament. Three types of fiber sizing were evaluated, the original epoxy-based sizing, an alkoxysilane Gelest sizing, and a water-based Michelman sizing. One hundred specimens were fabricated from composite material. Specimens varied by sizing, by fiberglass lengths, and by fiberglass volume fraction. Out of all the specimens tested, those with Michelman sizing produced the most consistent and overall best bonding. The Gelest sizing produced the highest and lowest values. Epoxy sizing produced almost as good results, and no sizing was worst. FDM thermoplastic filament of 1.75 mm diameter was extruded, and was used on a ROBO 3D FDM printer to 3D print objects. Mechanical strength and stiffness were not improved as expected because fiber lengths were much shorter than advertised. Other possible reasons include incomplete mixing of materials, processing errors, voids in specimens, and improper treatment of fibers with sizing. Key words: FDM 3D Printer – Fused Deposition Modeling type 3D printer, 3D printer Filament, Thermoplastic Material, ABS Fiberglass, Extrusion, Sizing. 1. Introduction Extruders are used to produce plastic products such as flexible pipes and plastic sheets. They can also be used to mix materials. Basically, extrusion is a process of applying heat and pressure to melt a polymer and force it through an orifice in a continuous process. It is used to produce polymer products of uniform shape and density. Extruder used to mix different polymers with additional materials like pigment, fillers, reinforcers etc. Melting is accomplished by frictional heating within barrel as material undergo shearing between screw barrel set up. Because the barrel is generally heated with heaters mounted around it. The barrel section temperature is optimized so that the viscosity of the melt is low enough to allow conveying down the barrel and proper mixing. Figure 1 shows a general extruder setup with single screw. Most extruders are electrically heated with either band-type resistance heaters, cast-in block heaters or tubular resistance heaters wrapped around the barrel. An efficient barrel cooling system is important to control the tendency for mechanical shear heat developed in the melt to override the electrical heater controls. The optimal extruder barrel length for extruder is 30-32 times its internal diameter (30:1 L/D, 32:1 L/D). Although shorter barrels can be used, mixing efficiency and melt uniformity are not optimal. Cooling to the extruder feed throat is critical to prevent surging or bridging. Internal cooling to the screw is not needed [1]. The objective of this paper is to study mechanical properties of thermoplastic material used in 3D printer and https://www.academicpublishers.org/journals/index.php/ijme 24 A MERICAN ACADEMIC PUBLISHER enhanced its Mechanical properties by adding various filling material as well as sizing materials to make it much more stronger and cost effective. 2. Discussion And Comparison Figure 1. Components and features of an extruder for plastics and elastomers [2]. Material flow in single screw extruders is driven by the properties of the material. Depending on the material being fed, a different screw can be used to handle the new material. Single screw extruders are popular and can handle some of the toughest materials. The single screw extruder pictured as shown in Figure 1 comes with a flame- hardened screw for handling abrasion and corrosion. In single screw extruders, a screw mixer melts the entering plastic materials, pushes the material through the extruder, and forms the plastic into the desired shape [3]. Extruders have three key components [3], (a) The hopper, where material is fed to the extruder. (b) The screw, which runs along the length of the machine. (c) The optional static mixers at the end. Figure 2. Single screw extruder [3]. https://www.academicpublishers.org/journals/index.php/ijme 25 A MERICAN ACADEMIC PUBLISHER Figure 2 shows single screw extruder set up. Single screw extruders rely on the friction between the material and the barrel for flow: the greater the friction, the slower the flow. One way to increase friction is to increase the length of the barrel, but this could result in a change in viscosity with position. The extruder temperature can be adjusted to control the viscosity [3]. Figure 3. Twin screw extruder [3]. Figure 3 shows the setup of twin screw extruder. Not all extruders with two screws are twin screw ext