Gravimetric calibration for optical measurements of droplets-in-flight

R.M. Verkouteren, C.J. Zeissler, J.R. Verkouteren
National Institute of Standards and Technology, US

Keywords: calibration, gravimetry, inkjet, metrology, optics, traceability

Summary:

We report gravimetric measurements of droplets, traceable to the SI, that enable the correction and calibration of optical measurements routinely used to monitor and control the dispensing of droplets from inkjet printers. This innovation results in improvement of uncertainty in droplet size from 10% to 1%, enablng current and future applications in inkjet-based additive manufacturing requiring this level of control. The work employs a novel inkjet control system, state-of-the-art gravimetric and optical measurement systems, as well as advanced image evaluation systems. Mounted standard polystyrene spheres are utilized for comparison with the droplets. Differences in optical biases are noted between opaque and translucent droplets-in-flight; these biases are explained using ray diagram models.