Additive manufacturing, as an innovative manufacturing technology compared to traditional subtractive manufacturing, offers greater design freedom and rapid prototyping capabilities. Material Extrusion (MEX), the most widely applied branch within additive manufacturing (AM), operates on the core principle of heating thermoplastic polymers or composite materials to a molten state, then depositing them layer by layer through a nozzle to form the final shape. However, the inherent contradiction between printing speed and build quality remains the key bottleneck limiting its widespread adoption. Desktop Material Extrusion techniques like Fused Filament Fabrication (FFF) offer high precision but require extended printing times. Meanwhile, industrial-scale Big Area Additive Manufacturing (BAAM) processes achieve high deposition rates yet suffer from insufficient accuracy. This paper systematically reviews the primary application domains of additive manufacturing technologies, elucidating their process flows and classification systems. Building upon this foundation, it systematically analyzes the contradiction and coupling relationship between high precision and high deposition speed in Material Extrusion technologies from aspects including hot-end flow, system thermal management, vibration, and printing parameters. It provides a reference for the subsequent design and optimization of high-precision, high-speed Material Extrusion (MEX) printers.

The fuel cell vehicle is one of the essential directions for developing new energy vehicles. But heat dissipation is a critical technical difficulty that needs to be solved urgently. Nano-coolant is a promising coolant that can potentially replace the existing coolant of a fuel cell. However, its thermal conductivity has a significant impact on heat dissipation performance, which is closely related to nanoparticles’ thermal conductivity, nanoparticles’ volume fraction, and the nano-coolant temperature. Many scholars have created the thermal conductivity models for nano-coolants to explore the mechanism of nano-coolants’ thermal conductivity. At present, there is no unified opinion on the mechanism of the micro thermal conductivity of the nano-coolant. Hence, this paper proposed a novel model to predict the thermal conductivity of ethylene glycol/deionized water-based nano-coolants. A corrected model was designed based on the Hamilton & Crosser model and nanolayer theory. Finally, a new theoretical model of nano-coolant thermal conductivity suitable for fuel cell vehicles was constructed based on the base fluid’s experimental data.