Direct-To-Garment Inkjet Devices: Technology Update
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PRODUCT ION Direct-to-Garment Inkjet Devices: Technology Update With average run lengths dropping, having the capability to print small quantity custom designs, at higher margins, is an attractive feature to the thousands who have adopted direct-to-garment inkjet technology in their shops. Fast production times, high-quality, full ink droplet. Siemens introduced the first with producing a four-color process, color images, unlimited customization and drop-on-demand inkjet printer, the PT-80, photographic print that actually looks ease of use are just some of the benefits in 1977. good and generates a profit when using associated with direct-to-garment digital Today, direct-to-garment inkjet printers screen printing. Digital equipment also has printing. This article explores direct- are being used by apparel decorators who less space requirements and is a low-cost to-garment inkjet technology and the are eager to gain additional market share. investment when compared with screen workflow necessary to produce a digitally With average run lengths dropping, having printing, which needs a larger amount of printed garment, discussing highlights of the the capability to print small quantity valuable floor space and potentially tens of technologies embedded in the latest devices custom designs, at higher margins, is an thousands of dollars in equipment costs. and recent trends in their development attractive feature to the thousands who Let’s not forget the labor and material cycle. You’ll find a direct comparison of have adopted direct-to-garment inkjet costs associated with making, cleaning screen versus digital production costs and technology in their shops. and reclaiming screens, not to mention the potential profit margin as well as the next Today’s consumer wants a product that solvent usage and mess that is generated. wave of technological developments that expresses his or her individuality. Fashion Digital produces little mess, requires no will impact digital printing. surveys indicate that a high percentage of screens, uses little solvent and could save Inkjet printing is a non-contact method young adults alter their clothing in some facilities time by avoiding setup delays or of printing, in which droplets of ink are way, reaffirming the notion that everyone downtime caused by screens. jetted through a small aperture (nozzle) to wants to be different. Digital technology Digital also thrives when variable data a specific position on a media to produce thrives in this context because of its ability is a job requirement. Names, numbers and an image. The first inkjet printer was to economically produce one or two prints design variations all are easily handled developed by Siemens in 1951, based on as compared with screen printing, which with digital technology. But as with any the continuous inkjet method whereby a involves the laborious task of making technology, digital has its disadvantages. piezoelectric crystal vibrates and causes a screens and setting up presses to produce For large-run lengths, digital is slower liquid stream to break into droplets. just one print. than screen printing, and can cost a Direct-to-garment inkjet devices use what company more to produce a job. The is known as drop-on-demand piezoelectric Advantages and Disadvantages of break-over between digital and screen technology, which produces ink drops by Direct-to-Garment Inkjet depends on each shop, applying voltage to a piezoelectric crystal Many find the biggest advantage of but reports of printers and causes it to vibrate. The mechanical digital technology is its ease of use in using direct-to-garment motion of the piezoelectric material creates producing vivid, full color photographic devices to produce pressure in the ink reservoir, and ejects an images. Gone are the challenges associated thousands of prints are ▲ By Johnny Shell, Vice President – Technical Services, SGIA Visit SGIA at SGIA.org SGIA Journal ■ Third Quarter 2007 11 becoming quite common. Obviously, the any color of fabric. But the disadvantages lead-time with a high-volume order will include longer print times, increased ink be a considerable factor when choosing a cost as compared with a digital print on printing technology. a light fabric and added workflow and Digitally printed ink costs also are maintenance steps. Another issue with considerably higher than those for screen, white ink is the settling properties. with prices ranging from a few pennies One might think white ink is no different to more than $2 per print. With screen, than any other used in inkjet printers. In average ink costs per print are usually less reality, white ink presents many challenges than 50 cents, with many at 25 cents or less. for developers, especially when printing on Digital also is not capable of producing the fabric. Industry pioneers in the graphics necessary abrasion resistance required industry were the first to use white ink in for athletic printing, nor is it capable of wide-format, UV-curable inkjet printers. printing special effect inks such as glitter Because UV-curable inks are aggressive and or gels. Matching Pantone or custom-spot extremely durable, they do not have media color can also be challenging because restraints other ink systems have. direct-to-garment devices use ink sets Once this realization caught on, we based on cyan, magenta, yellow and black started to see prints on unique substrates (CMYK). While many Pantone colors are such as stone, wood, leather, ceiling tile and achievable in the CMYK color space, a many others. As the saying goes, necessity considerable percentage is not. is the mother of invention. As you can Figure 1: Once printed, the ink must be set using either a heat press or a conveyor dryer. With most available direct to garment imagine, printing an image on stone would not have the same color and brightness as printing an image on white paper. Thus, the need for white ink was born. But developers quickly realized only certain white pigments would provide the necessary performance and opacity needed for their printers. Titanium dioxide is the most widely used white pigment because of its brightness, high-refractive Figure 2: Here we see an encoder strip at 100% (far left). The center image shows a new encoder strip. index and effectiveness as an opacifier. The far right image shows an encoder strip that is contaminated with ink overspray from the nozzles. However, titanium dioxide pigment is This can cause the printer to lose its frame of reference. harder to keep suspended in a solution devices, printing on dark shirts with because of its weight. If the pigment falls out white ink entails additional tasks of pre- of suspension, it is difficult to return the ink treating the garment, extra print passes to its original, homogenized state. The most and more regular maintenance procedures. common cause of this is when a printer is not Pre-treating a garment involves using a operated for quite some time. Most printers solution that is applied through a high- offering white ink have adequate movement volume, low-pressure (HVLP) spray gun that is naturally generated by the machine or via automatic-spray equipment, which is to keep the pigment in suspension. If the included on board the printer or as a stand- machines are not operated for more than a alone unit. The application consistency few days, the pigment will begin to fall out and pretreatment’s repeatability, when of suspension, which can cause problems. applying it manually with a spray gun, is Formulators are regularly introducing very important. Applying too much will newer versions of white ink that inhibit affect how well the image holds up in a pigment separation, so it is a problem every laundry cycle. Applying too little will cause leading company faces. the white ink to fall down into the dark Another obstacle with titanium oxide fibers of the shirt, instead of sitting on top is its aggressiveness on piezoelectric print to build the necessary opacity. The gun’s heads. White ink requires a bit more spray pattern can also affect the resulting involvement from the operator to ensure print, so keep the nozzle properly adjusted the device will function properly. A proper and cleaned to avoid spurts. maintenance schedule should be in place Using white ink will virtually double and followed to extend the life of the print the total print time for each shirt. White head. All inkjet printers will malfunction if ink is printed separately in the initial print they are not maintained and cleaned on a Figure 3: Print heads are the lifeblood of any device. pass, which deposits the under-base. This routine basis, no matter who manufactured Shown here are the print heads from a Brother print pass is followed by a second pass the device. GT541 (top) and an Epson 2200 based unit. All colors are jetted through the Epson head while that deposits the color, and sometimes a As mentioned, many direct-to-garment the Brother unit requires one head per color. highlight white. The big advantage of white devices are capable of printing white ink. ink is having the capability to decorate However, one manufacturer’s approach 12 SGIA Journal ■ Third Quarter 2007 Visit SGIA at SGIA.org was to adopt a technique that has long material deforms under electrical voltage, been used in screen printing. The Mimaki an acoustic-pressure wave is generated, Digital equipment also has GP604D uses discharge ink, which contains which affects the ink volume in the a chemical agent that works to remove the pressure chamber of the head. This wave less space requirements and is dyes in the shirt and return it to its pre- moves through the ink in the reservoir and dyed state. Color can then be printed in the toward the nozzle, eventually causing an a low-cost investment discharge areas.