DropWatcher 2.0

A key element of digital printing machines are the piezo-based print heads. In order to assess the influence of the individual parameters on the droplet quality of the printhead, a fully automatic DropWatcher was developed on the basis of previous studies.

Factsheet

Institute(s) Institute for Intelligent Industrial Systems (I3S)
Duration (planned) 18.08.2014 - 26.01.2015
Head of project Karl-Heinz Selbmann
Project staff Brian von Gunten
Ramon Felder
Michael Schmid

Project description

A key element of digital printing machines are the piezo-based print heads. These print heads are capable of jetting over 100 million droplets per second with a diameter of 20 μm. In order to assess the influence of the individual parameters on the droplet quality of the printhead, a fully automatic DropWatcher was developed on the basis of previous studies. Here, the droplets are imaged immediately on leaving the printhead with a rapid illumination unit and a camera. Different image processing algorithms are used to analyse these images and measure droplet properties such as volume and velocity. Figure 1 depicts the diagrammatic structure of the rig.

In order to be able to evaluate the quality of the droplets from all nozzles of the printhead, the DropWatcher is equipped with a lens and two linear axes, which make it possible to capture all nozzles one after the other. Figure 2 shows such a droplet photo: automatically detected droplets are marked with a cross.

Result

The DropWatcher is an efficient tool created by the institute to support the industry with precise analyses and proposals for optimising process stability. The high flexibility of the rig and the direct access to all print parameters make it possible to carry out a multitude of tests fully automatically.

Areas of application

The Process Optimisation in Manufacturing research group supports companies in optimising the parameters of an existing system, checks ink for its suitability for printing or helps in the selection of suitable components for a reliable printing process.

The customer-specific design of such a system would also be possible, whether for ink development or for the quality improvement/assurance of an existing printing process. With the DropWatcher, fluctuations in ink production can be detected and quantified early on to guarantee better quality.

Further areas of application of the DropWatcher: