high speed digital printing in textiles

High Speed Digital Printing : Latest Trends : A write-up

Multi-arrayed Carriage with More than 30 heads turn out to be RAVANA :

There have been many attempts by leading manufacturers of digital printing machines to induce speed. In fact, some manufacturers claim productivity of as much as 1200 sq. meters per hour, but at a much lower resolution...

Does it justify such investment?

Some major technical issues do occur while running a digital printer at that amount of speed, which includes force and equilateral drop size of the ink.

In a machine with 36/90 heads, there is a lot of wind generated with the force of so many heads when moving together and combined with the equilateral drop size and speed, the machine is bound to miss one of the dots and in this case if all the dots do not register, the print will lack its sharpness.

Imagine 90 heads lined up together and with thousands of nozzles firing at that speed at the same spot, if the lines waver a bit, go a little left or right, it will produce a blurred image.

Hence to give such machines a sharp design to print, their speed will have to be drastically dropped to maintain sharpness.

Though the concept of speed is good, a lot of work still needs to be done to make it workable before it is brought on to the shop floor. Putting bigger and more heads to increase speed is not the solution.

From a practical angle it should have been the head manufacturers making faster heads rather than the machine manufacturers making faster machines. Also for fashion we need sharper heads, but in reality few companies have that type of head.

Moral : Please donot rush for 30 heads or 90 heads concept : give time & see.

Another important element that should technically support faster machines is ink, most important is consistency and run-ability of an ink. Many inks clog at a speed of 100 metre per hour. It is important for users to first test the ink for at least 5 days before buying the brand as each ink has its own applicability and it is important that it matches to the requirement of the machine to give clean sharp images.

Manish Kapadia, JISL India [email protected] 9825246352 , 93774 60765. Visit us @ INDIA ITME, Dec.2-7, 2012, Bombay Exhibition Center, Mumbai.

.

www.jayinst.com O:91-79-30022792 TeleFax:26463981.

Besides the print head and ink, the RIP (Raster Image Processor) is the most important and also the most error prone software solution in the printing process. The RIP facilitates speed and transmits reliable information for creation and management of priority orders. But does it do this efficiently and seamlessly... Does it match colour easily and accurately, allow creation, view, edit, and with multiple colour ways do these features that synchronize with the machine speed... these are critical posers that need to be addressed.

The real challenge is to provide cost-effective machines not high-speed machines. And that is why replacement of rotary printing, which has a linear speed of 20 meters/minute, is impossible in India because it is just too cost- effective. Clearly, India needs machines which will give value for money, delivering cost-effective products with good maintenance, though high-end, high- speed machines are still a long way off for Indian users in the textile industry.

The global market for fabric printing is considered to be in the region of 27 billion sqm with positive prospects for growth although the recovery from economic recession is still fragile in some markets. According to a Global Industry Analysts, Inc (US) forecast an annual increase in the order of 3% would lift the print market to around 30-32 billion sqm by 2015.

Currently the textile print market is dominated by the Far East, with rotary screen printing the preferred method for long production runs of the same colorway. However the trend in the print market to shorter print runs does not favour rotary screen printing, nor does the continuing desire for fresh innovative designs with a rapid production turnaround. The latter approach favors digital inkjet printing where the digitalized designs are stored electronically making printing on demand a reality with rapid response to market requirements.

The current breakdown of the global market share of the 27 billion sq m traditional textile printing sector is divided geographically as follows:

China (30%), India (17.5%), Other Asian Countries (18.8%), Europe, Russia and CIS (11.1%), Americas (12.9%) and Middle East / Africa (9.7%).

Large textile printing firms in the Far East thus hold a dominant position in the global print market.

However China s leading position will come under pressure from India and other Asian countries, especially if the labor costs in China continue to rise faster than other Asian countries.


.


Another factor that could contribute further pressure from the fast fashion apparel market is the lead-time for printed garments to appear in the large retail markets of the USA and Europe. For example, printed goods from Turkey can be transported to the UK in five to seven days by road, whereas deliveries from China and Bangladesh can take four weeks by sea.

Such considerations clearly favor the digital inkjet printing method and this printing method seems likely to increase in importance as the range of inkjet printing end products continues to rise.

Back in 1991 the first textile inkjet printer could only produce 6sq m/hour.

Dramatic improvements in print head design, ink formulation and fabric pre- treatments since then have meant that speeds of 300sq m/hour and more can now be achieved, and direct to garment (DTG) printing using inkjet technology is also increasing in importance.

Irrespective of the textile printing technology used there is now increasing pressure upon dyestuffs, pigments and chemical auxiliary manufacturers to incorporate sustainability and concern for the environment into their products. In particular by producing more eco-friendly products for both screen printing and digital inkjet printing that decrease waste and / or can be recycled.

Many dye-makers have invested heavily in research and development into ink formulations for specific head technologies both for textiles and many other substrates because such products can be more profitable in comparison with the global pressure on dyestuff prices in which price competition has been relentless, and raw materials and energy costs have soared decreasing profit margins.

Digital inkjet printing is making inroads into garments, household textiles, technical textiles and display (e.g. soft signage), as well as flags and banners and the market continues to diversify with automotive textiles an interesting area for digital printing.

At present the total market for digital printing of textiles is only around 200 million sq m per year but a joint study by Pira International and FESPA has forecast that the market for digital prints could grow to about US$1.3 billion by 2014.

A major development in print head technology has been the introduction of the Kyocera KJ4B print head which is leading to a new generation of digital printing machines for textiles that will reach the speeds per hour currently attained by automatic flat screen printing machinery in Europe.


.


The Kyocera KJ4B has 2656 nozzles offering a 600 x 600 dpi (dots per inch) resolution and operates on the DOD (drop-on-demand) piezoelectric principle. The Reggiani ReNOIR and the MS-JPK series, the MS-Rio, and the Stork Sphene, La Meccanica Qualijet K series machines are based upon the Kyocera KJ4B aqueous system which uses an ink viscosity of 5.5-6.5 mPas.

Fiber pretreatment for inkjet printing is also critical

The digital textile printing technology has moved out of its initial phase of bringing stability to the technology, and now is focusing its energies on production speeds. The majority of the digital textile machine manufacturers are targeting higher production rates per hour.

Digital textile printing versus rotary printing in near future

Digital printing focuses on

- savings on sampling - Savings of hidden costs - Environment friendly : needs no cloth screens to be discarded & too little water to wash. - No big/small sreeens needed : No SCREENS for digital printing. - Small batch sizes are never a problem - Changeover of matchings or whole designs over a split-second; on the fly. - Neat & clean job : No screens to be washed ! No stains on m/c, groud, environment or people : PLEASE FIND COLOR ONLY WHERE IT HAS TO BE PRESENT. that is CLOTH.

Right drop at right place !

- Save on labour ; work with a small team.

- Dont worry about big repeatless designs & exclusive onetime multi million colors...!

Digital textile print production is now capable of matching flat screen-printing performance, and is fast approaching the rotary screen-print production rates for some European countries. In a couple of years, it will definitely begin to affect the market share of rotary printing machines. However, it’s not the time to press the panic button, as looking at the current technology available today, we are of the opinion that both technologies can and will co-exist together in the near future. Both have their advantages and disadvantages.


.


Trend in ink development

Recently, dyestuff/pigment companies in India and other countries that see the potential of digital textile printing have included digital textile ink in their development pipeline. However, the ink approval process and manufacturing reliable inks is a tedious process. In addition, the companies also have to alter their inks to keep in tune with the fast changing head and equipment technology. New development in inks include fluids which are compatible with the new high production machines and are able to give optimum performance for ensuring correct positioning of the drops fired at high speeds from the print heads.

Ink Pricing Prices of inks have seen reduction with the technology being widely accepted by many textile mills and printers across the world. We feel that ink prices will be stable in this year owing to increase is cost of raw materials and labour. Additionally, continuous development of the printing machines leads to ink companies investing in R&D to manufacture inks, which are compatible with the printing speeds. However, we will always see a range of ink products depending on the budget of the end user as we see in all technologies across industries.

Price of inks is not the real motivator for growth of the digital textile printing industry. The emphasis should be more on the long-term advantages the complete package of digital textile printing technology offers. The cost advantages it offers to the end user in the form of value addition, short runs, minimal wastage, very low turnaround times and low inventories adds much more to the revenues.

Running a digital textile printer at optimum production level is a combination of the following factors:

Correct choice of the machine, inks and RIP software to suit your production volume, quality and fabrics

Appropriate training from the machine manufacturers, RIP software suppliers, ink manufacturers and allied service providers to the end users to optimally use the entire digital textile printing package

Accurate feedback and documentation from the end user to the technology suppliers to resolve issues efficiently

Timely follow up of maintenance schedule by end user and use of approved spares, inks to avoid downtime

Continuous interaction between suppliers and end users


.


From Our JAYSYNTH Pavellion :

La Meccanica ITALY has wide-format textile production printer QualiJet K8 and K16 based on the Kyocera KJ4B print head, has shown at both FESPA Digital and ITMA, equipped with either a single row of 8 heads or a double row of 16. In the 16-head version it will have a maximum speed of 560 sqm/hour, at 600x600dpi, or 490sqm/hour in quality mode. Ink set-up may be either 8 colours or 4 x 4 colours. The machine comes with a driven unwinding system as standard and fabric transport by adhesive belt, with a double-brush washing system. The in-line dryer can be specified with a choice of heat sources. An open bulk ink system offers a total capacity of 20 litres per colour, in double 10-litre talks with automated switching.

The Jaysynth group formulates Digital Inks inks in 8-color sets that have the right concentration and color build as well as good jetability on these Kyocera heads. The fact that we are dye manufacturers since last 4 decades, gives us an additional advantage because we know dyes to make them fit for formulating into inks. The inks for industrial machines have to be robust and of high quality, and pass through the very small nozzles of the print head even after hours and hours of industrial production.

Pre-treatment for digital-textile printing (Write-up given in our earlier email)

The initial cloth preparation and the subsequent pre-treatment for digital-textile printing are among the most critical steps in ensuring that the final print delivers the required design aesthetics –not only in terms of print definition, colour and brightness, but also in terms of the colour-fastness performance. The chemicals are normally added to conventional textile-printing pastes to promote dye fixation, satisfactory colour fastness and – importantly – print definition cannot be added to inkjet-ink formulations. These additives can be of a wide range of chemical types (thickeners, urea, acid donors, and alkalis) and there are many reasons why they cannot be used, not least the rheology properties of the print thickeners, which have viscosity levels many times higher than can be jetted from print heads. Also, many of the chemicals used in conventional textile printing have damaging effects on the manufacturing materials used in the print head.

Therefore, the general process route in digital inkjet printing of textiles is to run the fabric though a chemical bath (padder) in order to fix necessary chemicals on the fabric before the printing stage. One of the key requirements is the addition of a thickener agent or other propriety chemicals to ‘hold’ the deposited inkjet ink on the fabric and prevent it from ‘wicking’ and ‘flushing’ before it dries and during the fixation stage.

To prepare your own fabric for digital printing; many digital-textile printers have to follow this route, particularly if they are processing a wide range of different fabrics and cloth constructions for their customers.


.

Here it starts to get a little more complicated!

In the conventional, analogue, screen textile-printing industry, there is a well- known term ‘RFP’, which means ‘Ready for print’ ; this is either done ‘in-house’ by the textile printer or is commissioned to a 3rd -party textile producer. Whichever method is used, the grey fabric must be efficiently prepared to controlled test parameters that the digital-textile printer and fabric producer have agreed. For example, for a cotton fabric to be printed with reactive dyes, the process route consists of ‘Singeing-De sizing-Scouring-Bleaching-Mercerisation- Wash-off-Controlled dried’. There are different cloth-preparation routes for the wide range of fabrics that can be printed.

To differentiate the initial cloth preparation from the pre-treatment required for digital-textile printing, a new term, RFDP, should be used: RFDP stands for ‘Ready for digital printing’

Some of the main points to watch inthe RFDP (Ready for digital printing ) stage are the follows:

•Pad liquor should be made up ‘fresh’ prior to padding and mixed well

•Pad liquor application should be uniform across the fabric width, and efficient padmangles such as the Küsters ‘swimming-roller’ types should be used

•Pad liquor pick-up should be as low as possible

•Drying temperature should be controlled across the width of the fabric and‘face-to-back’, preferably using a modern multi-bay stenter.

•After the fabric is pre-treated, the processed fabric should be covered and kept in controlled conditions, particularly to avoid problems of moisture absorption and exposure to light.

As we have said, the initial fabric preparation (RFP) stage is just as important as the digital-textile pre-treatment stage and should have been carried out efficiently, as many of the problems that are claimed to be the fault of poor digital-textile pre- treatment (RFDP) are in fact caused by poor initial fabric preparation (RFP), or a messed up yarn fiber quality just put in the selvedges.


.


T-shirts Printer

One of the digital-textile printing sectors that is growing significantly is DTG (Direct to Garment) printing. In the main, this means digital textile pigment printing of T-shirts.

The DTG printer must be aware that the garment preparation of his T–shirt can have a significant effect on his final print, although in the majority of cases, the knitted-yarn quality, garment manufacture, cloth preparation and ‘finishing’ (usually a pre-shrinkage stage) are really out of his control.

Also, for the DTG printer, control of the exhaust-dyeing stage (for dark grounds) is equally out of his hands. However, some printing faults can be caused by poor yarn quality, inadequate singeing and the application of ‘softening’ agents after the garment manufacture, and the DTG printer must be able to recognize some of these faults.

In the best-case scenario, the sourcing and quality of the T-shirt should be controlled and monitored, although in reality this is only possible for the largest T- shirt print producers. The application of the DTG pre-treatment is normally a propriety chemical mixture (usually a textile acrylic polymer and an inorganic acid catalyst – for example, reference 3), and is applied by one of three different methods:

•Manual spray system prior to DTG printing

•Automatic ‘off-line’ spraying system (controlled-nozzle systems)

•In-line system – integrated into the print stage(‘wet-on-wet’)Again, as with dye- based digital-textile systems described earlier in this article, whichever method is used, it must be repeatable under controlled conditions and periodically monitored by a defined quality-control technique. In conclusion, pre-treatment is a critical stage in both dye and pigment digital-textile printing systems, and there are no ‘shortcuts’ to ensuring quality textile prints.

The initial cloth-preparation stage, termed RFP, is just as important as the RFDP stage, and whichever textile fabric is being processed, the initial processing trials and final established production method have to be controlled and continuously monitored to ensure optimum textile prints.

References :

1. ‘Chemistry & Technology of Fabric Preparation & Finishing’,Dr Charles Tomasino, College of Textiles, NC State University,USA, 1992 (http://www.p2pays.org/ref/06/05815.pdf -

2. The Küsters DyePad


.


high speed digital printing in textiles

Documents