For some time now, the growth of inkjet technology for printing on textiles has stolen the limelight from screen and rotary printing technologies. There are many well-known reasons for this: sustainability; design flexibility; and machinery footprint, to name only a few. However, analogue printing techniques still account for around 95% of all fabric printed globally and countless print service providers have committed to a combined analogue and digital business model, choosing the most appropriate technology for each application. Analogue methods are here to stay, with rotary printing alone occupying around 65% of the market. It is therefore useful to look at where advances are being made in this area, particularly with ITMA Asia + CITME and then ITMA Barcelona on the horizon.

For screen print houses whose main advantage is cost, margins are tightly controlled, and this makes it difficult for printers to make the decision to invest in new technology, as capital investment into new machinery can be expensive. However, it often pays to adopt new technology where process efficiency gains can be made and print quality enhanced, thus bringing the printer new and regular business.

Machinery developments

When it comes to technology, the essential principles of rotary and flatbed operations have not developed much in the last 20 years. However, many OEMs in this area have introduced significant upgrades to their machines, including one of the most prominent technology providers, SPGPrints. The addition of interactive touch screens for control and monitoring of machinery and quick changing of printing screens have been two of the most notable developments.

Horst Ros, managing director, Zimmer Austria comments: “Digital screen printing is the future of textile printing. Certain process technologies still must be improved, production costs to be reduced to be more competitive, but this is a normal step in revolutionising a new technology. In the meantime, the conventional screen-printing market enjoys a revival on a very high level. Full order books for high-end machine manufacturers.

“In this field, Zimmer Austria takes the leadership in quality, precision and reliability. The increasing demand for very precise rotary printing machines has been taken by Zimmer Austria. Different machine types have been vastly upgraded with more precise screen-printing heads, new software for more economic operation. In this case, the rise of digital print was the driving force behind the new demands. It was no question at all for the Zimmer team, to bring the rotary screen machine execution to a new, very high, level.”

With patents expiring on Zimmer Austria’s invention of the magnetic squeegee system though – a technology that allows for enhanced levelness and fabric penetration by creating a magnetic field that draws the dyes through the fabric or carpet pile – many manufacturers now also offer both steel blade and rotary magnetic systems.

Magnetic systems have been a key area of development, particularly for carpet printing. For example, Chinese finishing technology provider Fujian Jinjiang Jeeone Printing and Dyeing Machinery (Jeeone) recently filed a textile printer patent describing a ‘Wide intelligent carpet circular screen printer’ which it says incorporates a “printing mechanism [that] comprises a circular screen, a magnetic table and a dye pipe; the circular screen is horizontally placed above the magnetic table […] dye is attracted through the magnetic table, is sucked out of the circular screen, and is attracted on a carpet, and the printing aim is achieved.”

Incorporating robotics

Perhaps the most innovative development in the analogue printing area comes from Japan’s Ichinose. The company has introduced the Ichinose X, a textile flat-screen printing robot.

The aim of the robot is to recreate the skills of an artisan printer. It incorporates independently moving robotic arms, complete with unique gripping tools to handle the screens, printing paste containers and squeegees. This is the first instance of a digital technology in the textile printing sector that is not inkjet-centric yet is being used to automate printing production.

The Ichinose X robot can handle heavy objects up to 20kg in weight, in each arm. It is mounted on a swivelling axis to allow the same degree of movement as a human and each arm has a ‘7 axis configuration’, the company says.

Software developments

Software is another critical area of development for analogue print houses. Jeeone has launched the eighth edition of its Davinci rotary printing machine, the DV-08, which it says includes cloud-based remote control and monitoring technology for real-time maintenance. This is a primary area of development for rotary technology providers. A major benefit seen with inkjet printing for textiles is the ability to digitally control the printer and gain efficiency from data analytics and workflow management. If some of this can be achieved in the rotary space, and perhaps the data shared in a common platform, then end users of the technology will benefit and the overall printing process will become more efficient.

This leads neatly on to CAD software developments at the print design creation stage. Whilst, again, these systems are often focused on inkjet printing, software is now being developed to enable designers to see separations and create colourways that are aligned with whichever technology will be used to print the final fabric.

For example, software provider Pointcarré, traditionally a technology supplier to the weaving industry, recently launched its ColorSep software, which provides the designer with colourway options depending on whether their design is to be rotary printed or inkjet printed. In both cases, the work process is complex due to colour separation. There is an innate affinity between the digital design process and the digital inkjet printing process; however due to cost, many digital designs end up being screen printed. Pointcarré’s software provides the opportunity for the designer to see the analogue and digital options for the final print, to ensure they are content with each option.

Recycling resources

In addition to efficiency and quality gains that come from hardware and software developments, progress is also being made towards a more sustainable analogue printing process. For dye-based printing there is a necessary washing stage in the production process, which is water intensive. Recycling of wastewater is therefore increasingly in focus in an effort to limit both fresh water and energy use.

Multiple technologies are being employed by print houses for the treatment of wastewater. A recently published research paper in the academic journal Dyes and Pigments evaluated the use of membrane filtration in order to clean water contaminated by reactive dye waste at a screen-printing facility. The treatment was carried out at a pilot wastewater treatment plant in Slovenia using ultrafiltration (UF) and reverse osmosis (RO). Whilst it was concluded that the water could not be cleaned enough to allow its discharge into other water sources, it was cleaned to a standard where it could be used again to wash printed textiles.[i]

In June, the ZDHC Roadmap to Zero programme also published a new ZDHC Wastewater Treatment Technologies document, a guide to improve the quality of wastewater discharge in the apparel, textile and footwear industries. Like the aforementioned research, it notes that printing process waste contains a high level of pollutants, from pastes to urea, binders, film forming substances and more, and highlights the use of membranes for printing wastewater treatment. The document recommends the use of UF tubular membranes that it says “are best suited for this application to remove colour and the binder. The clean permeate has a 90% reduction in BOD and 100% reduction in colour. The water is recycled back to the print machine for reuse.”[ii] Companies such as Dynatec Systems and Cellab offer UF industrial wastewater treatment systems for this purpose.

Automatic colour kitchens

Another area where efforts are being made to minimise waste is in the development and adoption of automated printing paste mixing. Many printers use the term ‘colour shops’ to describe this step in the manufacturing process. Making conventional printing pastes for analogue printing, which have very high viscosities, has become increasingly automated at progressive print houses. This is, to an extent, a fallout from the negative public exposure of unclean colour kitchens in many textile regions.

Japanese and Italian OEMs have led the way in automation of analogue print paste manufacture. Italy-based ColorService offers its Neutral Paste Preparation Unit which automatically prepares the paste thickener, starting from powder and liquid auxiliaries. The preparation unit is fitted with a mixer. It is then dispensed using an Automated Dosing System, eliminating waste. The complete system can be managed by one operator, ColorService says.

Vanwyk Systems also developed the Direct Compact Dispenser (DCD) which enables automatic dispensing of printing paste for production as well as for sampling purposes. The system’s modular construction is said to combine ease of operation with precision dispensing, high capacity and low investment. Vanwyk says that whether used as a stand-alone dispenser, or integrated with automatic mixing and transport modules, the DCD provides fast dispensing with great reproducibility. The DCD system is offered with Vanwyk’s Camelot software, which was initially launched in 2003 and offers re-use return colours optimally, to reduce material costs and pollution problems.

Future improvements in the automated printing paste area are likely to be led by software developments. For example, dispensing equipment and software provider GSE recently launched its Ink Manager software for the label industry. This is said to provide print houses with the control and information required to run ‘lean and smart’ ink and printing operations. Though the software is not specified to be used in the textile industry at the moment, GSE is active in this market with its Textile Management Software (TMS) and textile paste dispensers. The current Ink Manager provides label printers with formula preparation tools, production run scheduling, tracking of ink recycling, and search, reporting and connectivity functions.

Printing paste developments

When it comes to printing pastes, minimising process steps in pre- and post-processing and improving vibrancy, handle and fastness are always going to be the main focus of OEMs.

Back in 2012, BASF launched its Helizarin Soft System, which was marketed as producing pigment prints with similar brilliancy and handle, and equal or better fastness properties, than reactive prints. The company subsequently sold its textile pigment business to Archroma where binder developments have continued, aiming to reduce chemical use, including formaldehyde reduction and elimination in cross linking additives.

Just before it sold its textile business to Archroma, BASF updated the Helizarin system in 2014, which became Helizarin EcoSafe. This was described as a ‘benchmark printing solution’ and BASF said: “Helizarin Ecosafe ‘zero add-on’ formaldehyde pigment printing system offers the highest level of consumer safety available in the market today. It complies with the strict Japanese Law 112, which requires non-detectable limits of formaldehyde for infant clothing.”

Others have followed this direction. Pigment printing dominates the textile printing industry, with a 40-50% market share, and whilst fashion still depends on the achievement of bright colours and good wash fastness and this has led most recent analogue printing research to focus on further development of pigments.

“Rotary screen printing will be in the bulk market for many more years to come. This not only in the bulk production markets such as China, Bangladesh, India, Indonesia, etc., but with recent sales in Europe and the USA underpinning the revival of this long-time technology,” Ros concludes.

References

[i] Šostar-Turk, Sonja & Simonič, M & Petrinic, Irena. (2005). Wastewater treatment after reactive printing. Dyes and Pigments. 64. 147-152. 10.1016/j.dyepig.2004.04.001.

[ii] ZDHC Wastewater Treatment Technologies https://www.roadmaptozero.com/fileadmin/pdf/Files_2018/Wastewater_Treatment_Technologies_for_the_Textile_Industry-FINAL.pdf