Ink printing with variable drop volume separation

摘要

An ink drop ejecting printhead (16) includes a substrate (42) having an ink drop emitting opening (46); a heater (50) on the substrate (42) surrounding the opening; and an ink supply communicating with the opening to supply ink, whose surface tension decreases inversely with its temperature, to the opening under positive pressure relative to ambient. A variable-energy electrical power supply connected to the heater, whereby application of an electrical pulse of sufficient energy to the heater will cause separation of an associated ink drop from the ink supply. A power supply control is adapted to regulate the energy of electrical pulses applied to the heater from the power supply, whereby the volumes of separated ink drops are proportional to the energy of the associated electrical pulses.