During the duration of the Glazetile project, the achieved results were even higher than expectations. In this period, experimental activities were carried out aimed at verifying the critical points in the construction of the two printers (DigiGlaze and DigiGraphic), as envisaged in the Glazetile project (WP1, T 1.3 definition of the final layout). Feedback from clients of beta test printers and the analysis of failures (FMEA) were helpful for the enhancement of the printers’ performance. CFD simulations were also carried out for the accomplishment of this task.
DigiGlaze is for the continuous deposition of engobes/glazes to obtain full coverage of the tiles. DigiGraphic is for the deposition of engobes/glazes for decorative purposes through structuring the surface of the ceramic tile with three-dimensional features that can reproduce the appearance of natural materials, as stones, woods, marble, etc. TI divided the development into two areas: one was focused on DigiGlaze operation mode definition, by comparing Continuous Jetting Mode (CJT) and Drop on Demand (DoD) technologies. In particular, significant efforts were addressed to the development of the DoD print-head bar. The work on DigiGraphic was mainly to verify the functionality and durability of the electrovalves (Evs) employed and to individuate alternative routes for the digital structuring of tiles. In particular, a new technological solution emerged for the structuring of tile surfaces during the period.
DoD technology demonstrated to be the most flexible, permitting to obtain a very precise and uniform deposition of smaltobbi, glazes and engobes having very different compositions and rheological behaviors. Compared to spraying technology, the most consolidated in the sector, immediate advantages are obtained as very high savings in terms of glazes, water, energy and plant engineering and the elimination of atomized ceramic materials and other organic-based contaminants, dramatically reducing the problems of health of operators and environmental contamination in a broad sense. The basic structure of the machine consists in a patented electro-mechanical drop dispenser system forming the DoD print-head bar, in which numerous nozzles are inserted, controlled by a specific numerical control. In the case of DigiGraphic, the initial design idea, a bar consisting of a series of nozzles and solenoid valves controlled singularly by the control system, was replaced by a system consisting of two application bars. By doing this, the resolution of the printer was enhanced from 25 to 200 DPI.
Furthermore, during the first 14 months, three important additional auxiliary equipment were designed to complement the printers. A double tank was designed to control the glaze feeding to the printer. It receives the raw glaze and it adjusts their rheological conditions and make them suitable for the printer. For doing this, a viscometer was designed, able to tune in real-time the density and viscosity of the as-received glazes in the production lines. In addition, a vision control system to perform in real time the quality inspection of the yield tiles was also studied and implemented. Both additional instruments can be controlled in place and on-remote and are integrated with the main printer following the protocols of Industry 4.0 most used in ceramic tile manufacturing lines (Modbus TCP).
