Article 2. 1 st Digital Printing Workflow in Surat - Impressions. 1. Introduction

Transcription

1 Article 2 1 st Digital Printing Workflow in Surat - Impressions 1. Introduction The 1th digital printing workshop was held on 2-3 August in Surat India, the heart of textile business in India. The workshop focussed on both commercial and technical topics dealing with the market potential and challenges of DP in this sector. Digital printing experts from USA, Belgium, China, UK, Korea, Japan, India and Italy covered the different aspects of digital printing during a two days workshop. Discussed topics dealed with RIP software, digital inks, print head technology, equipment, chemical aspects as well as industrial experiences. With the growth of DP printing, the DP-market has become a dizzying array of the different components, each of which individually and collectively affects the results. The DP-output is a reflection of the design and colour management software, RIP software providing the interface between the design software and the DP-printer, the printing environment, the inks, the fabric, including pre- and post treatments and last but not least the operator. All these variables must be tuned to each other in order to obtain an optimal and reproducible print result. In addition, the agenda of the workshop was designed to provide the participants (number: 156) with a comprehensive assessment of technology, market trends that will determine the role of inkjet in the textile printed market. The formal presentations, informal networking sessions and table top products provided a unique interactive environment for delegates to network, developed an improved understanding of inkjet technology and its capabilities. It assisted also local printers to make an informed future choice on which printing technology is suitable for their respective applications.

2 m2 * liters ink * The technical workshop was organised by the Indian World Textile and invited a few foreign speakers specialised in the different components of digital printing such as software (RIP), hardware, inks and textile. Lectures were given by S. Smith - DPinnovations (RIP software), Prof. Dr. M. Van Parys TO2C (chemical aspects of digital printing, pre-and post treatments), J. Gill Fujifilm Dimatix and D. Torp Global Inkjet Systems Ltd (a comprehensive overview of different DP-print heads and maintenance) and V. Guo Chinese National Engineering Research Centre (DP-technologies). Testimonials came from a few Indian digital printers and technical contributions from MS (IT), Reggiani (IT), Seiko (JP), Atexco (CN), Jaysynth (IN), DGI Corporation (KR), TTP Meteor (UK). The machine manufactures and inks suppliers presented during technical sessions their view over the future of digital printing. 2. General remarks actual situation Stork Prints Inkjet India 2012 The digital printing market is booming although it only grabs a small piece of the big printing cake. It is estimated that the actual printing market is around 33 billion m 2, digital printing accounts for only 1,3% (460 million m 2 ). The total market of dyes and pigments is estimated 9 mio tons. Only 0,04% tons is used in DP-inks. Around tons are used for apparel and World household textiles. market digital textile printing Digital Textile Printing market display m2 technical m2 household m2 clothing m2 inks liters November 30, 2012 Derived from data from The future of Digital Textile Printing to 2017, Dr JD Hayward, Smithers Pira 2012 Figure 1: Market evolution of DP-printing worldwide 4

3 The digital printing is progressively growing (figure 1). During the workshop it becomes clear that in the so-called emerging countries such as China, Pakistan, India, Brazil, Turkey and (to a lesser extend) India (figure 2) the investments in digital printers are huge and progressive! During the period ca high-productivity printing units were implemented worldwide, mainly in the mentioned countries. During the next year (period September 2013 till September 2104) one expect that more than industrial printers will be sold. According to DGI (Digital Graphics Incorporation Korea) DP-printers are registered in Turkey of which about 4500 transfer printers. Recently MS (I) sold world s highest speed printer MS LaRio to a Turkish company. The industrial printer is a single-pass printer (Kyocera print heads) with a width of 3,2 m and a production capacity of (read well) m 2 /h and surpasses the production of conventional screen printing machines, taken in account that more than 40% of the time traditional printing units stands still (changing and cleaning procedures for screens). Figure 2: Annual growth/market share of DP-printing in India compared to other countries (Source: J. Notermans, Stork Prints B.V. (Nl)). 3. Trends to high-speed printers However the landscape has now changed considerably, with the availability of high-speed machines, with the inevitably of requiring more water, energy and effluent disposal, as well as higher generating CO 2 emissions. The participating machine manufacturers (MS, Regianni, Atexco (CN), DGI (KR), Dimatix) and ink suppliers (Huntsmann, Jaysynth) are looking for ways to bring greater flexibility to their

4 ink price per kg capabilities without committing to ever-greater equipment costs and increased resources. Two most-often-quoted disadvantages of digital printing until recently were production speeds and ink costs (figure 3). However on both levels there have been considerable technological changes in recent times. This include in overall output (metres per hour) and a clear significant reduction in Inkjet India 2012 the prices of (water-based) digital inks. The former higher cost of inks was the result of on the one hand the increased investment required for the ink development and on the other hand the relative small volumes required at the time. Indeed, a new generation e high-speed machines has significantly counteracted this situation. Stork Prints Ink prices , ,00 100,00 10,00 Worldwide average digital textile ink prices , , ,00 60, , Inks can never get as cheap as printing paste or conventional dyes 23,00 20, , November 30, 2012 Worldwide ink consumption '000 kgs Figure 3: Cost evolution of DP Source: J. Notermans, Stork Prints B.V. (Nl) (Indian Digital conference 2012) 7 Indeed, the business landscape is a fast changing world. Mostly based on new generation of print engines every 3 years a new generation printers comes out. The new generation of high output digital printers are based on high-speed print heads (Ricoh Gen 4, Seiko 508GS, Konica 1024i and Kyocera KJ4B) and has rebalanced the equation compared to conventional printing. The new industrial printers have a production performance approaching the levels per hour achievable with flat screen-printing machines, and even productions levels of short-run rotary screen printers. Also the cost and greater pallet of available waterborne inks (reactive, acid, disperse, latex) has considerably decrease production costs and decrease further. These benefits swing the pendulum more and more from traditional screen-printing to DPprinting. In other words: even in Far-East countries on mid-long term DP-printing will become textile printer s first choice when looking for a new capacity or replacements traditional printing machines (flatbed- rotation screen). Today the crossover point (few hundreds of meters) where DP printing becomes more favourable in cost per square meter varies for different countries and individual factories.

5 4. Ecological considerations a change is IMMINENT One of the main advantages of DP printing is the environmental benefit, in terms of reduced energy, emissions, water and effluent costs. Traditional printing is one of the largest users of chemicals and despite source reduction strategies the industry has still the challenge or obligation to reduce its ecological footprint. Environmental consideration is one of the prime motivators of a switch to digital technologies. A detailed European study published some time ago compared screen with DP-printing. Wastewater was reduced to 60%, thermal energy savings were 80% and usage electricity fell 30%. In addition there was a reduction of 70 % in space required for machinery and a nearly 100% reduction in excess dye (figure 4). Figure 4: Digital printing compared to conventional printing Source: EU-project TIEPRINT-technology transfer of low environmental impact inkjet printing for the production of textile products (source: MS) Digital printing is currently getting a lot of attention because of the urgent need for further innovations, the search for new printing applications and more (lucrative) high added value niche markets.

6 Although very impressive the results were still based on small production printers with output below 20 m 2 /hour. 5. Digital textile and Fashion the wind of Change Recent years have been breakthrough years for digital prints for apparel and inspiring instruments for fashion designers. DP printing is rapidly evolving to fulfil an ever-increasing role in the fashion supply chain and bring value and new opportunities for our European textile industry. Digital printing has opened new areas for design, chiming in with the search for an individual look. In line with the increasing T-shirt printing also big digital prints boom and boost fashion s enthusiasm for personalized designs. Often big picture prints covering a whole garment or garment panel are dominant and contribute to the high-street trends. In addition, the many brilliant colours achievable with reactive, acid and disperse inks and the high variety of chemical and mechanical finishes - used to improve handle, performance and creating special effects - are a constant in the fashion world. In return, this key trend will becomes a massive opportunity for the sector s machinery and chemical producers. Today, prints are seen a seasonal update for apparel and accessories, even in menswear. Now it is almost impossible to distinguish which patterns have been produced by traditional methods and which digitally, unless there is a photographic element in the design. In addition, environmental awareness has become an integral of every part of our lives: personal, commercial and industrial. Some brands as Puma, H&M, Lacoste, Nike, Adidas were all identified and publicly criticized as being connected to water polluting dyeing and printing facilities. Important is that some of the brands as Levi s, Wal*Mart, Adidas, Gap, H&M, Burberry have already established regular and active environmental screening mechanisms in their supply chain. Also sport clothing is based mainly on PES and to a lesser extends on PA. DP-printing can be done via DDP (direct) or IDDP (indirect digital printing transfer). Cons and pros for both approaches were discussed and are summarized in table 1. Table 1: Pros and cons for direct and transfer printing

7 According to DTG in Korea the outdoor wear market (3th biggest in the world) is also dominated by polyester. The clothing is mainly digital printed using transfer printing for two main reasons: lower initial investments and production costs compared to direct printing as illustrated in tables 2 and 3. Table 2-3: Korean companies choose for transfer printing (source: DGI - Korea)

8 Also in other countries transfer printing is not only used for sport clothing but also for other casual and technical clothing. However, as can seen from table 4 the quality of the used transfer paper differs from country to country. Table 4: transfer paper quality in different countries Counrty india Turkey Brazil Korea Paper Weight g Length Weight roll kg

9 Furthermore is becomes clear that digital technologies will also become important for interior textiles (curtains, wall covering, upholstery, bed clothing, pillows, table clothing, attributes ) and for the often-esoteric field of technical textiles (sailings, balloons ). The three biggest machine constructors namely Zimmer (Au), Reggiani (I) and MS (I) are responding to these trends by the introduction of high productivity printers. Finally, digital technologies will not be stopped for printing but also digital finishes and coatings come more and more in the picture. 6. Discussion on different parameters of DP-printing a) RIP-software (Raster Image Processing) Choosing the RIP must be based on the printer s workflow requirement. Understanding and managing workflow and colour space are critical items for a successful DP-business. Today there are several RIP and Colour management software available. Digital textile printing production is primarily focused on two types of workflow: a) Separated (Traditional) and/or b) Composite (Consumer) A traditional textile printing process is based on having separations for each printed color. A consumer textile print process is based on printing images where hundreds to millions of colors are in a single layer. Using the layers/channels capability of an image file format, or the separation capability of the RIP, allows the digital printing workflow to be used similarly to a traditional printing process, where one color is specified per separation (black/white or greyscale). This Separated workflow allows for easy creation of color variations, better simulation of a traditional printing process, but can t easily be used to print photographic (Perceptual) type images. When all colors (hundreds to millions) exist within a single layer, this is a Composite image. A Composite workflow is optimized for photographic (Perceptual) printing, but can t easily be

10 used to create selective color variations or simulate a traditional printing process. RIP s focus solely on using ICC s for optimum perceptual (Consumer) workflows. Some RIP s have optimized their profiling, including development of unique profiling technology, to ensure superior color matching for absolute (Traditional) workflows. Understand Workflow requirements and evaluate printer s RIP-options based on the type of workflow that is most important to the printer. Steve Smith (DPInnovations, UK) stated: using a profile that is not created using your printer, your settings, your fabric and your ink will result in INFERIOR printed results. b. High-speed Print heads At the ITMA 2011 print heads for industrial printers were almost from Kyocera. However, during the last two years the situation is changed and according to J. Gill (Dimatex) one notice a big shift to other suppliers as illustrated in figure 5. The most dominant print head technology is piezo-based (figure 6). Figure 5: Different high-speed print heads market share

11 Figure 6: Print head technologies Table 5: Some print heads and characteristics The different parameters in table 5 are not directly related to performance; ink flow, ink droplet stability and other factors need to be considered. Concerning ink circulation, print heads can be divided in two systems: a) single ended and b) through or continuous ink flow heads (figure 7).

12 Ink Flow Pressure chamber End shooter/single ended Ink in Ink flows into the channel and exits only through the nozzle Recirculating/through flow Ink flows continuously through the channel and exits the nozzle only when required Pressure chamber Ink in Ink out Figure 7: Print heads DOD PIEZO (source: XAAR) Advantages linked to the continuous flow across nozzles are: 18 Diagrams source: Xaar web site Global Inkjet Systems 2006/13 - Nozzle self recovery - Low maintenance/less cleaning cycles - Suitable for difficult inks (e.g. pigment inks) - Production cost is reduced due to: o Decreasing downtime reflecting in more production o Less replacement of the print head required. c. Textile materials specific treatments One reason for the comparatively slow growth of digital printing on textiles may be related to the extreme demands of the textile applications. Although ink-jet printing onto fabric works in fundamentally the same way as any office type ink-jet prints onto paper, fabric has always been inherently more difficult to print due to its flexible nature. The level of flexibility varies from warp to weft and with each degree around the bias, so guiding the fabric under digital printer heads has proven to be very challenging. Other challenges: o There are many types of synthetic and natural fibers, each with its own ink compatibility characteristics

13 In addition to dealing with a fabric that is stretchable and flexible, it is often a highly porous and textured surface (including, smoothness, spun or filament yarns) o Dust, debris, loose fibres must be avoided. They are cause of blocking nozzles, or semi-blocking nozzles causing drop deviation, scratches during maintenance and as a consequence cause drop deviation and misplacement of missing jets. o The fabric has much greater absorbency, requiring many times the ink volume compared with printing on papers. Use requirements include light fastness, water fastness (sweat, too) through finishing operations and often outdoor use, heavy wear, abrasion, and cleaning The fabric not only has to look good but to feel good too; Except for transfer printing direct DP-printing require a specific chemical pretreatment mostly done off-line in house or at a commission. The specific treatment must be adapted in function of the textile substrate (type, texture), digital inks and wanted print quality. Specific treatment is required: o Apply chemicals needed for fixation (alkaline for reactive inks, acid spender for acid inks) o Controlled ink penetration (reduction of capillary behavior) o Better levelness, quality image (resolution) o Higher colour build-up, colour gamut o Less bleeding o Better fastness properties Frequently overlooked factor is the initial fabric preparation (desizing, scouring, bleaching, mercerization ) And finally, pre-treated materials must be stored in controlled optimal conditions (read: light, temperature, humidity) Prof. Dr. Marc Van Parys UNITEX University College Ghent info@unitex.be