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SUSTAINABILITY
Why is digital textile printing at the forefront of sustainable production compared to traditional rotary screen printing?
For anyone who has visited a traditional rotary textile printing machine or flatbed screen printer, the answer to this question is blatantly obvious. Add to this the drastic change in market trends and print volumes – and now you are witnessing an industrial sector built for mass production, struggling to flex towards a new era of on-demand manufacturing.
Caption: With the dramatic change in market trends and print volumes within the textile industry, you are now witnessing an industrial sector built for mass production, struggling to flex towards a new era of on-demand manufacturing.
A traditional rotary screen printing machine that prints 12 colors at 3.6 meters wide, with a steam or gas dryer, an automated color kitchen, and a screen washing area, will occupy over 5,000 square feet of factory space. In contrast, a similar digital printing machine, using the same components, will take up less than 400 square feet. Add to this the large amount of warehouse space needed to store rotary printing screens and large drums of bulk color, as well as auxiliary machinery, and the difference in scale between digital and rotary printing operations becomes exponential. About twenty times the space is required for screen printing compared to a high-tech digital textile printing installation.
In the world of sustainability, great importance is given to minimizing resource use. When comparing factory space, digital textile printing machinery drastically reduces the production footprint and sets a new benchmark for sustainability in textile manufacturing, clearly paving the way for more efficient use of the planet's resources.
The second difference, and equally striking, is that of water and ink volumes. In the traditional rotary screen printing plant, water and ink are everywhere, in stark contrast to the digital printing environment. However, it should be noted that many of the analog printing machines in use around the world are workhorses, regularly delivering millions of meters of printed fabric worldwide. There have been many new developments in recent years to successfully improve the environmental impact of high-production analog mills, but above all, the traditional rotary printing factory remains a working environment.
Why does rotary screen printing use large volumes of water and ink? During rotary screen printing, ink is forced through the mesh of the screen by a flexible squeegee and, depending on the mesh size, along with the weight of the fabric, it will use ink at a rate of 35-60 cc per printed meter. In contrast: digital textile printing using piezoelectric printheads that spray micro droplets of ink onto the fabric surface uses between 6 and 9 cc per printed meter.
In simple terms, this means that a run of 10,000 meters on a rotary screen printer will use over 540 kilos of ink compared to the 90 kilos used by the digital printer. Since the main component in aqueous ink dispersions is water, this implies a 600% water saving by the digital textile printer.
But the story of water savings in digital textile printing does not end here. At the end of each print cycle, the rotary screens must be emptied of excess color and then washed before storage. This causes contaminated water to flow into the factory's drainage system, which in many cases consists of a simple river drain, causing serious environmental damage if the textile production effluent is not treated.
In contrast, the digital textile printing process does not involve wastewater or the creation of effluents where post-fabric finishing is a dry process. Pigmented inks, for example, do not generate wastewater.
The differences between the digital and rotary textile production processes are evident when exploring the simplicity of the digital process. The digital inkjet process offers an ecological and clean footprint, combining both ink and printing technology. Rotary printing requires a team of technicians and the support of additional auxiliary resources; ink kitchen, screen engraving, washing, and finishing to name just a few.
By FESPA 28/04/2021
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