A three-dimensional (3D) printer includes an ejector and a heating element configured to heat a solid printing material in the ejector, thereby causing the solid printing material to change to a liquid printing material within the ejector. The 3D printer also includes a coil wrapped at least partially around the ejector. The 3D printer also includes a power source configured to supply one or more pulses of power to the coil, which cause one or more drops of the liquid printing material to flow out of the ejector through a nozzle of the ejector. The 3D printer also includes a gas-controlling device configured to control a gas in the 3D printer.