Xaar technology can print at 360 dpi with 8 levels of grey; this capability is reaching the market in the form of the XaarJet XJ500S.Xaar achieves greyscale printing by rapid ejection of multiple droplets, which merge to produce a single dot on the paper. The basic piezoelectric operation of the technology is explained, whereby shear mode deformation of shared walls causes acoustic waves in channels, resulting in ejection of droplets. The waveforms used to operate the printhead are explained.The nozzle plate is made of polyimide; the nozzles are ablated, nine at a time, using an excimer laser and special optics. Great care is taken over cleanliness, in order to avoid nozzle blockages; integrated filters are provided to each of the four colour manifolds.The printheads incorporates an RS232 interface for printhead configuration and a 4-bit bus for data communication, a microcontroller, EEPROM for configuration storage, voltage control according to actuator temperature, and special purpose drive chips.The actuator and electronics are mounted on an aluminium chassis to provided good heat sinking, and special waveforms can be used on non-fired channels to maintain temperature uniformity.