Piezoelectric inkjet printing has revolutionised ceramic tile decoration over a short period of time – an amazing achievement for an industry that had seen little use of computers. Requirements for shorter product lifecycles, increased production efficiency and unique aesthetic appearance fit well with the benefits of piezoelectric inkjet printing and application to ceramic tile glazing. Despite boasting several advantages over the traditional spraying technique, piezoelectric digital glazing has not been successfully implemented by any ceramic tile factory so far.
Particle size and inkjet ink composition matter
Factories that massively produce ceramic tiles typically use drop-on-demand printing systems based on piezoelectric printheads. The tiles are printed using inks that are chemically engineered to be compatible with the post-processing process – firing. The downsides come in the form of two pretty substantial issues. “Current piezoelectric printhead technology can handle glazes of small particle sizes less than 2 microns. A micro-milling technique must be applied to avoid blocking of the printhead nozzle, but the process demands more energy use and creates material waste,” explains Ormes Corradini, project coordinator of the EU-funded Glazetile project. Another critical issue is the odour and polluting emissions stemming from the firing ceramic process, which is attributed to the chemical composition of the digital inks. These typically contain organic solvents. In such cases, suction cabins and aspiration systems are used to safeguard operators’ health.
Glazing and decorating with water-based inks
The Glazetile project enabled companies SCE and Tecno Italia to develop a novel family of digital machines that addresses the downsides of current inkjet printing for ceramic tile glazing and decoration. “Our solutions which outclass state-of-the-art technology have the potential to transform digital ceramic glazing in the industry. They help create smoother surfaces, while use of water-based inks eliminates harmful emissions during the firing process and reduces waste glaze by 40 %,” notes Dr Dino Boccaccini, Head of R&D at Tecno Italia. The new innovative digital printers allow operators to streamline the full digital glazing line. The DigiGlaze machine is designed for the first step of the glazing process prior to decoration; it produces a uniform surface coating that covers the whole tile surface. Using cutting-edge electromechanical drop-on-demand dispensers, it enables printing to fragile materials. “Importantly, our machine can handle cheap water-based glazes with particle sizes of up to 60 microns, similar to those of traditional glazes,” notes Dr Boccaccini. DigiGraphic is a more complex machine, designed for the final step of the glazing production line. Depending on the tile size, the digital system utilises a high number of micro-valves to apply the final enamel to the surface. “Glazetile printers apply the coating not only for protecting the tile piece, but also for creating high-quality unique patterns of the finest detail. The capability to draw through a glaze is unique to the sector,” explains Corradini.
Compliance with Industry 4.0 standards
Italian companies are working tirelessly to assure interconnectivity of their digital printing machines with the fourth industrial revolution. “Our digital printers will be equipped with auxiliary systems that will enable automatic preparation of the glazing process. Their integration in the manufacturing line will allow operators remotely manage machinery and system assembly, installation and maintenance, as well as tile production,” adds Corradini.
Glazetile, glazing, ceramic tile, decoration, inkjet printing, SCE, Tecno Italia, DigiGraphic, DigiGlaze, Industry 4.0