Induction Heating Based 3D Metal Printing of Eutectic Alloy Using Vibrating Nozzle

摘要

Induction heating has been used widely for heating and melting of metal workpieces. We have designed and developed a low-power, high-frequency electromagnetic Induction heater (IH) for metal 3D printing using a zero-voltage switching (ZVS) circuit. During this process, an alternating current pass through inductor and capacitor tank circuit at its resonating frequency and creates an alternating magnetic field inside the helical induction coil. Alternating magnetic field leads to the generation of eddy currents in the workpiece. Due to Joule heating, these eddy currents heat and melt the workpiece in a short time. A real-time monitoring and control of the workpiece temperature were implemented for lead-free solder (Sn99Cul) using a metal-oxide-semiconductor-field-effect transistor (MOSFET) based control circuit driven by Data Acquisition (DAQ) module and Lab VIEW. To demonstrate the 3D metal printing, molten solder was deposited drop-by-drop using a lead-screw based computer-controlled positioning system. Solder was melted inside the aluminium tube attached with the brass nozzle. The nozzle diameter and distance between the nozzle head to the bed surface was 0.4 mm and 7 mm respectively. The droplets were generated by vibrating the whole nozzle filled with molten solder using a vibration motor attached to the nozzle tube. The vibration motor frequency and relative speed of the bed surface were ≈130 Hz and 25 cm/min respectively. A study of varying molten solder temperatures to print multi-layer structures with controlled CNC movement was conducted for printing 3D metal structures. The solder was printed in the form of individual droplets at temperatures close to the melting point (227 °C) while at higher temperatures (235 °C) the molten droplets fused before solidifying.