An apparatus and method of operating a
liquid drop emitter, such as an ink jet device, for emitting liquid drops of different volumes. The
liquid drop emitter comprises a chamber, filled with a liquid, having a
nozzle for emitting drops of the liquid, a thermo-mechanical
actuator having a moveable portion within the chamber for applying pressure to the liquid at the
nozzle, and apparatus adapted to apply heat pulses to the thermo-mechanical
actuator. The method for operating comprises applying a first
heat pulse having a first power P1, first
pulse duration τp1, and first energy E1=P1×τp1, displacing the movable portion of the
actuator so that a drop is emitted having a first
drop volume Vd1, and traveling substantially at the target velocity v0; and applying a second
heat pulse having a second power P2, second
pulse duration τp2, and second energy E2=P2×τp2, displacing the movable portion of the actuator so that a drop is emitted having a second
drop volume Vd2 and traveling substantially at the target velocity v0, wherein Vd2>Vd1, E2>E1, τp2>τp1, and P2<P1. An alternate method for operating causes the emission of drops having different volumes traveling at different velocities wherein all velocities are within a pre-determined drop velocity range, vd min to vd max. Further methods for operating an ink jet printhead cause the emission of drops having different volumes and velocities wherein the triggering of the drop emission is delayed so as to result in synchronized arrival times at a print plane.