Introduction to Inkjet Digital Printing

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The newest printing method for textiles is digital ink-jet printing. This is process in which a special inkjet printer with special ink is used to print directly on fabric from the computer directly. The artwork and the dye is heat set with a heat press or tunnel dryer From a technical standpoint, this process is identical to the ink-jet printer used with nearly every desktop computer. However, for fabrics, these machines are 60-84 inches wide. Digital printing offers tremendous design capabilities. Designs of photographic image quality are possible with this technique. Of course, the method uses a CAD system with digitized image data. It presents the opportunity to change from one design to another immediately without any printed fabric waste. This method has been used in conjunction with body-scan data to produce printed fabrics that are custom fitted for the individual. It has also been used to rapidly produce trial prints for sale or evaluation. Many individuals foresee this method as a technique for the future.

There are technological shortcomings associated with thismethod. The current top printing speeds range from 60-90 yards per hour forflat fabrics compared with a rotary screen machine output of 50-120 yards perminute. The limiting factor on printing speed is the technology of the printingheads. Reports indicate that these production speeds will not increase unlessthere is a breakthrough in the mechanics of the printing heads. Other printerhardware limitations include cost of the printer heads, ink jet nozzleclogging, ink recycle, reuse systems, and machine width limitations.In addition to these hurdles, there are color depth and colorfastness issues with many of the dye systems currently available. Generally,the fabric to be printed must be pretreated with a material such as sodiumalginate and alkali, so the printed dye will not bleed and smear beforefixation. Ink-jet pigment inks have been developed, but from a commercialviewpoint, ink viscosity, pigment colorant particle size, and print durabilityare limiting factors. Regardless of the technical limitations, digital ink-jetprinting is a viable commercial alternative technique for small runs (50 yardsand under) of highly styled premium fabrics as are used in scarves and ties.


Currently, numerous organizations are researching ways toovercome the problems of ink jet printing of textile fabrics. The most commonlyused digital printing technology for textile printing is ink jet. The ink jetprocess is a computer to print technology in which ink is sprayed from nozzles,which means that no printing master is needed and the imaging is done directlyonto the substrate.

Within the digital textile printing for visual communication a division has to be made in 
• Low-volume dye-sub printers (e.g. ATPColor,Roland, D-Gen, Mimaki, Mutoh)
 • Mid-volume wide format printers (e.g. Atexco, ATPColor,Roland, Durst, Hollanders Printing Systems, Vutek)
 • High-volume industrial printers (e.g. Atexco, Reggiani, MS, Osiris, Stork, Konica-Minolta, Zimmer)

How Ink-Jet Digital Textile Printing Done?


So,how does the process work? Well, like any design project, digital textileprinting begins with the art. An artist creates an image in any type of graphicdesign program (Adobe Illustrator, for example) and formats it as a TaggedImage File Format, otherwise known as a TIFF file. Designers useTIFF files because the format stores images without losing details (they tendto be much larger than JPEG files, which you might use when you take pictureswith a digital camera). If the design is original, hand-done artwork, it'sscanned and converted to digital format. Designs tend to be those without firmborders or seams so they can be repeated many times.
Nowit's time to transfer the image to fabric. Digital textile printing uses inkjettechnology and ink (in this case, dye) cartridges like a printer you may haveat home, just on a much larger scale. The first step is to pretreat thefabric with liquid solutions that prepare it to accept the dye and betterabsorb the color. Then it's fed through the printer, which sprays the dye ontothe textile with tiny droplets. The final step is fixing thefabric, a process that ensures the permanency of the design. Depending on thetype of textile and type of dye, fixing may involve steam, dry heat, orpressure. Sometimes it requires a combination of two or more of those.

Advantages of  Ink-Jet Digital Printing


• Quick reaction
With its fast proofing, digitalprinting machine can enhance the response speed of the    enterprise to the order, step by step inthe shopping mall, enhance the competition of  printing enterprises, reduce the processing price and reduce the profitspace. Customers put forward higher requirements for printing enterprises fromaspects of cost, response speed, quality, service and so on. Improving thespeed of proofing will undoubtedly make the enterprise win in the hands of manycompetitions.
 
• Cost reduction
The use of digital printing machinecan replace some of the original work that must be done on the circular andflat screen printing machines without taking up the time of the machine.Usually a sample often takes up 3-4 hours of a machine. If the customer is notsatisfied, it will be modified again and again, resulting in a great waste ofproduction capacity.
 
• The effect is good and thecustomer's approval rate is High
 Digital printing and traditional printingbelong to different systems. Many professional and technical personnel areworried that the effect of proofing with digital printing machine is too good.Traditional printing can not achieve this effect. In fact, this worry isunnecessary. At present, in order to solve this problem, domestic companieshave organized the best technicians in China to carry out in-depth research andfind out the solutions. This scheme uses software to adjust the effect ofdigital printing, so that the traditional printing machine can fully achievethe effect in production. From the perspective of color, because the colorrange of traditional printing paste is wider than that of digital printing ink,the color effect produced by digital printing machine can also be simulated bytraditional sizing agent.
 
• Wide range of application                 
The ink that can be used for proofing has active ink, acidink, dispersed ink (transfer printing), and the use of dispersed ink is used tofind the right ink. In the customer's sample, if it's paper manuscript orelectronic manuscript, it can be directly printed with digital printing machineafter color separation. The traditional printing machine can complete massproduction according to the proofing effect.
 
·      Eliminates the issuesthat were resulting from the use of rotary screens.
·      Reduces time to introducenew designs and make modifications.
·      Reduces costs tointroduce new designs.
·      Lowers energy, water andmaterial consumption.
·      Makes less important lowcost location for production.
·      Reduces environmentalimpact.

Disadvantages of Ink-Jet Digital Printing


• Thespeed of printing is slow
Efficiency is money, the speed of printing isto a large extent the benefit  of theenterprise. At present, the speed of the fastest digital ink jet  printing machine can reach 150m2/h, but it isstill far behind the  traditionalprinting machine, and it needs to be further improved.
 
• The problem of the combination of new and old  technology
Digital printing technology continues to improve, the speedof printing is also accelerating, but to catch up with the speed of thetraditional printing machine still has a long way to go. Therefore, the use oftime-saving digital printing machine for proofing or small quantity production,combined with traditional printing machine for mass production, will be a basiccombination mode of textile printing industry for a period of time. And thecombination of new and old technology and difficult problems, we need to makefurther breakthroughs.
 
• The ink cost is high
 Although digital ink-jet printing withoutmaking screen, a small amount  ofproduction total cost than traditional printing, dye and pigment ink  which is cheaper than traditional printing ismuch higher, so more than a  certainlength after printing, digital printing ink prices will boost the cost  of making more than traditional printing. Theprice of the ink in the  future needs tobe adjusted reasonably to promote the development of  digital ink-jet printing.
 
• Color accuracy
Compared with the traditional printing of spot colorprinting, namely, each set of colors individually adjust the color paste,through the computer color matching system, we can achieve high color accuracy,even if a color paste deviate, it only affects one color. The digital printingis CMYK mixed color printing, all colors are mixed by four color ink. A littlebit of external influence, such as ink difference, printhead difference andtiny change in printing process, will affect the accuracy of a series of colorsafter blending. Therefore, the color accuracy of digital printing is a littleworse than that of traditional printing.
 
·       Digitaltextile printing is prone to banding.
·       Contact of print head with fabricmay cause image distortion or printer damage.
·       Thereare problems in reproducing half-tones.
·       There are problems in color repetition, especially in side-by-side printing.
·       Digitaltextile printers use expensive inks.
·       Digitaltextile printers run with limited speed.
·       Digital textileprinting is currentlyeconomical only for short runs.


 
 Inks Used As per Fabric
     
Cellulosics Fabric - Reactive Inks
Polyster Fabric - Disperse Inks
Polyamide Fabric - Acid / Metal Complex Inks
Wool Fabric - Acid / Metal Complex Inks
Silk Fabric - Acid / Metal Complex Inks


Conclusion


Digital printing provides a multidisciplinary environment for the development and production of innovative textile and apparel products. The sector is characterised by a large number of companies that have been exploiting available technologies and extending the boundaries of commercial application. It is emerging as a significant industry and as the employer of professionals who are competent in their chosen field of technology.

The work of designers is significantly affected. This is not just because of the skills they need to create designs for digital printing. The lead times for digitally printed products can be very short, because production batches can be as long or as short as the market will take. Consequently, designers exploiting the potential of the technology will be working close in time to the point of sale: for garments, this is the domain of ‘Fast Fashion’.

Product development also needs to be short and streamlined in order to respond to market demand. The traditional sequential processes will not suffice: concurrent practices are needed (Tyler, 2008) with teamwork across the relevant disciplines. The core skills to manage the production technologies are to be found in the supply chain, and these skills also need to be utilised in the product development process. The opportunity exists for marketing and buying staff to be effective team members, with the goal of responding to market demand and surprising the market with innovative products.

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