Proceedings of the
9th International Conference of Asian Society for Precision Engineering and Nanotechnology (ASPEN2022)
15 – 18 November 2022, Singapore
doi:10.3850/978-981-18-6021-8_OR-01-0036
Fin Design for Passive Cooling in Screw Extrusion Additive Manufacturing (SEAM)
Department of Mechanical Engineering, Indian Institute of Technology (IIT) Bombay, Powai, Mumbai, Maharashtra 400076, India
ABSTRACT
Additive manufacturing (AM), also called 3D printing (3DP), is a state-of-the-art, non-conventional manufacturing process, that enables solid physical realization of a given CAD (computer-aided-design) model, via layer-by-layer deposition. Over the years, various AM techniques have been developed, for various choices of feed materials and forms. Thermoplastics are one of the most commonly used material choices for AM applications which are 3D printed using the technique of fused deposition modeling (FDM) or fused filament fabrication (FFF). FDM is based on pinch-wheel extrusion where the thermoplastic material in filament/wire form, is pinch fed into a liquefier. The material is melted, continuously extruded, and selectively deposited over the built platform, to get the desired geometry. Although being one of the most widely used AM techniques, FDM suffers from various bottlenecks such as low part strength, high material cost, huge printing time, poor surface finish, and non-conformal slicing, which limit its usage for prototyping purposes only. Screw extrusion-based additive manufacturing (SEAM) is a material-extrusion technique that also employs continuous extrusion and selective deposition via a single-screw extruder. It is commonly applied for thermoplastic materials in granular form and is hence, also called fused granular fabrication (FGF). The use of granular feed form, instead of the typical wire, reduces the material cost by almost 90% and manufacturing cost by almost 50%. Screw extrusion also provides escalated outputs and flow metering, which helps in reducing the overall printing time. The liquefier region in SEAM is much larger than FDM, thus providing better heating conditions, which has a direct consequence on the part strength. Because of the before mentioned reasons, SEAM is explored as an alternative for FDM. SEAM set-ups typically have a liquefier zone, for melting and phase change of the thermoplastic material; and a cooling zone, which is placed near the throat area. Granular material feeding happens at the throat area and should be maintained well below the softening point of the thermoplastic material to avoid blockage and choking of the set-up. Active cooling devices such as water jackets and cooling fans are commonly employed but add up to the cost and additional maintenance. In this research, passive cooling devices such as fins, are designed, developed, and fabricated for a single screw extrusion-based additive manufacturing set-up for 3D printing applications using thermoplastic ABS (Acrylonitrile Butadiene Styrene) material. Circular-shaped fins are designed for aluminum, considering the availability and ease of manufacturability. Iterations are made for the number of fins required with limiting conditions on the peak temperature near the throat area, for a given liquefier temperature. Steady-state heat transfer simulations are carried out using the thermal simulations module on Solid Works 2021. The final design is then fabricated and tested on a SEAM set-up. The current design presents a fin-based passive cooling approach for SEAM set-up and doesn't require any additional assembly or control.
Keywords: Additive Manufacturing (AM), Single Screw Extrusion, Passive Cooling, Fin Design, Heat Transfer Simulation.
Department of Mechanical Engineering, Indian Institute of Technology (IIT) Bombay, Powai, Mumbai, Maharashtra 400076, India
ABSTRACT
Additive manufacturing (AM), also called 3D printing (3DP), is a state-of-the-art, non-conventional manufacturing process, that enables solid physical realization of a given CAD (computer-aided-design) model, via layer-by-layer deposition. Over the years, various AM techniques have been developed, for various choices of feed materials and forms. Thermoplastics are one of the most commonly used material choices for AM applications which are 3D printed using the technique of fused deposition modeling (FDM) or fused filament fabrication (FFF). FDM is based on pinch-wheel extrusion where the thermoplastic material in filament/wire form, is pinch fed into a liquefier. The material is melted, continuously extruded, and selectively deposited over the built platform, to get the desired geometry. Although being one of the most widely used AM techniques, FDM suffers from various bottlenecks such as low part strength, high material cost, huge printing time, poor surface finish, and non-conformal slicing, which limit its usage for prototyping purposes only. Screw extrusion-based additive manufacturing (SEAM) is a material-extrusion technique that also employs continuous extrusion and selective deposition via a single-screw extruder. It is commonly applied for thermoplastic materials in granular form and is hence, also called fused granular fabrication (FGF). The use of granular feed form, instead of the typical wire, reduces the material cost by almost 90% and manufacturing cost by almost 50%. Screw extrusion also provides escalated outputs and flow metering, which helps in reducing the overall printing time. The liquefier region in SEAM is much larger than FDM, thus providing better heating conditions, which has a direct consequence on the part strength. Because of the before mentioned reasons, SEAM is explored as an alternative for FDM. SEAM set-ups typically have a liquefier zone, for melting and phase change of the thermoplastic material; and a cooling zone, which is placed near the throat area. Granular material feeding happens at the throat area and should be maintained well below the softening point of the thermoplastic material to avoid blockage and choking of the set-up. Active cooling devices such as water jackets and cooling fans are commonly employed but add up to the cost and additional maintenance. In this research, passive cooling devices such as fins, are designed, developed, and fabricated for a single screw extrusion-based additive manufacturing set-up for 3D printing applications using thermoplastic ABS (Acrylonitrile Butadiene Styrene) material. Circular-shaped fins are designed for aluminum, considering the availability and ease of manufacturability. Iterations are made for the number of fins required with limiting conditions on the peak temperature near the throat area, for a given liquefier temperature. Steady-state heat transfer simulations are carried out using the thermal simulations module on Solid Works 2021. The final design is then fabricated and tested on a SEAM set-up. The current design presents a fin-based passive cooling approach for SEAM set-up and doesn't require any additional assembly or control.
Keywords: Additive Manufacturing (AM), Single Screw Extrusion, Passive Cooling, Fin Design, Heat Transfer Simulation.
