Enhancement of mechanical properties in large-object additive manufacturing through local halogen heat treatment

Abstract

Extrusion-based additive manufacturing makes products by continuously stacking melted filaments vertically. The 3D printing market has been consistently growing based on application in various fields like automotive, marine structure, and building. As extrusion-based additive manufacturing advances, the maximum build size has increased, leading to Large Object Additive Manufacturing (LOAM) that can produce meter-scale products. LOAM has advantages such as reduced manufacturing time and part merge. Currently, LOAM is being utilized in industries that require large components, such as automotive and aerospace. However, LOAM has limitation in mechanical properties compared to traditional methods. Weak interlayer adhesion from vertical stacking, internal voids, and printing environment causes the shortage of mechanical properties. Various research has been attempted to resolve this limitation, such as short fiber addition, process parameter optimization and adopting simulations and machine learning. However, these methods resulted improvement in specific direction or validation in their own equipment and structures. Auxiliary heat supply is another resolution to enhance properties. By supplying additional heat through various heat sources in manufacturing, thermal gradient and plastic deformation can be reduced. Improvements in mechanical properties were achieved using various heat sources such as infrared heater, substrate heater and lasers. However, auxiliary heat supply methods have issues of long preheating time and energy wastage. In this experiment, halogen lamp heat treatment method is proposed with short preheating time and local heating of specific areas. The halogen lamp heats the surface of layer before or after the PC-CF20 filament extrusion. Tensile tests were conducted to validate halogen lamp heat treatment. Microstructure of fracture surface, dimensional accuracy and layer temperature were observed. Tensile test results showed up to a 69 percent increase in tensile properties and 19 percent decrease in anisotropy due to low thermal gradient and high layer temperature. Especially, the timing of auxiliary heat supply causes different enhancement on mechanical properties. Mitigation in internal voids, irregular fiber arrangements contributed to mechanical properties enhancement. Interestingly, No significant changes in dimensional accuracy of LOAM product. The proposed halogen lamp heat treatment method holds academic value as it allows selective property enhancement and improvement in specific direction through halogen lamp control. Additionally, halogen lamp heat treatment costs less power by comparing infrared heaters and substrate heat sources, indicating more efficient energy utilization. By special halogen lamp capable of local heating, we achieved an improvement in the mechanical properties, addressing the issue with the extrusion method. Active adoption of halogen lamp heat treatment method is expected in industries with LOAM.