DIGITAL PRINTING MACHINE Digital Textile Printing, Often Referred to As
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1 | P a g e DIGITAL PRINTING MACHINE Digital textile printing, often referred to as direct to garment printing, DTG printing, and digital garment printing is a process of printing on textiles and garments using specialized or modified inkjet technology. Inkjet printing on fabric is also possible with an inkjet printer by using fabric sheets with a removable paper backing. Today major inkjet technology manufacturers can offer specialized products designed for direct printing on textiles, not only for sampling but also for bulk production. Since the early 1990s, inkjet technology and specially developed water-based ink (known as dye-sublimation or disperse direct ink) has offered the possibility of printing directly onto polyester fabric. This is mainly related to visual communication in retail and brand promotion (flags, banners and other point of sales applications). Printing onto nylon and silk can be done by using an acid ink. Reactive ink is used for cellulose based fibers, such as cotton and linen. Using inkjet technology in digital textile printing allows for single pieces, mid-run production and even long-run alternatives to screen printed fabric. PRINCIPAL Digital printing is an invention that involves art work being process by a computer, and then printed directly on to the surface of fabric. Digital printing is not a heat transfer, as the ink is directly adhered to the fabric. 2 | P a g e Digital printing is an easier process than screen printing. A customer can get a multiple colour design without having to have a screen made for each colour. Digital printing does not use screen allows for a photographic print, with much more details than traditional screen printing. This provides significant saving in both time and money. Digital printing is often used for design with a lot of detail, colour and high resolution. As the ink isapply thinner, Digital printing is best used on lighter coloured ground, to allow the design to shine through The fact the design is processed and printed digitally allows for a quantity one, since there are no screens or physical set up. MECHANISM Digital Textile Printing delivers the ability to print designs on fabric, directly from a PC or Mac.Inkjet printing is done on fabric in the same manner as it‟s done on paper, and just as easily. Printed textiles can be used for a vast range of applications including flags and banners, exhibition signage, Clothing etc. Digital textile printing is a process of printing on garments and textiles using specialized or modified inkjet technology. 3 | P a g e The two keyrequirements of a digital textile printer are a transport mechanism for the garment andspecial inks that are applied to the textile directly to be absorbed by the fibres. Direct to garment Visual communication The predominant textile media used in visual communication is a polyester based fabric. the type of ink chemistry needs to fit requirements for the media (such as polyester, nylon, cotton, silk). Based on the media and ink combination, the choice comes for infra- red fixation, heat-press sublimation or steaming. The structure of the fabric also needs attention, for example whether it is woven, non-woven or knitted. Polyester fabric is printed mostly with dye-sub or disperse direct ink, although UV and solvent inks (including HP‟s latex formulation) can also be used. The great benefit of sublimation ink is the fact that the colorants will bond with the fibre during sublimation or fixation. The biggest advantage of direct to media is drastically reduced waste. This method doesn‟t need printing on transfer paper first before calendering (or heat- pressing) it onto the media. Waste is both an economical and an ecological factor in print production. Print speed doesn‟t account for much if a large portion is being thrown 4 | P a g e away as waste due to incompatibility of media, ink, treatment or lack of know-how. CONSTRUCTION AND WORKING The origin of DTP System Digital Textile Printing System was first started to develop from the Inkjet type of plotter for sample development and with day to day improvements in resolution & speeds, now it has become a standalone shop. Also applications of these printers are varied with fast developing printing skills, media, ink etc. it is used to produce big size of photos and hanging banners that hang on the buildings to a small multicoloured designer silk handkerchief & Ties. ▶ Construction of DTP System Printer Head : A 'Printer Head' is the most important part of the DTP system. Mostly these are PIEZO drop on demand print heads. Piezo Head - A 'Head' of 'Piezo type' was developed by 'Epson' for Inkjet printers and this type of head is used for DTP system. There are many other head manufacturers now trying to adopt to textile inks &industrial textile printing. Normally the resolution used for textile printing is 720 dpi. Body : The construction Digital Textile Printing system currently being sold, depends mainly on the kind of fabric 5 | P a g e being used for printing and the purpose. There are various constructions depending on printing being used for Flags & banners, direct disperse, sublimation paper printing or printing on fashion textiles using Reactive / Acid inks. Also it depends if you want to print directly on fabric or transfer. Fabric feeding system : There are several types of the 'fabric feeding system', 'Cylinder' or 'Blanket type' etc. and again the choice is dependent on the kind of printing & fabric used. Ink supplying System: An 'Ink supply system' can be varied depending on which DTP System is used. This has developed over the years and is a very important area for the performance & run-ability of the inks. The “bulk ink” systems over a “cartridge type” system makes the inks to run better and also coupled with a degassing system helps to remove the unwanted bubbles in the ink, hence giving a better ink performance and lower maintenance and down time of the machine Inks : Types of ink that can be used for DTP system are ' Reactive Inks ' , ' Acid Inks ' , ‘ Disperse inks ‘ and ' Pigmented Inks '. ① Reactive Ink - This ink is the mostly used ink in general textile industry. It has almost the same color density as screen print colors and it is especially suitable for home textiles & fashion fabrics. It is used for cotton , 6 | P a g e silk or even wool. Post printing, it has to be steamed at +/- 102℃ for achieving high quality of colors & fastness. ② Acid Ink - It is used for general sportswear such as swimming suits etc made out of NYLON LYCRA or fabrics from Animal fibre such as wool & silk. Though it offers bright and fresh colors like reactive inks, but due to higher flexibility of Reactive inks, they are preferred more over acid inks until unless the production is restricted to only exclusive fabric like silk or nylon. Also high 'ultraviolet light resistance' can be obtained by steaming process like in case of reactive inks. ③ Disperse Dye Ink - It is used for polyester and good for Home textiles, fashion wear, sportswear & also flag printing. There are various ways for post printing process for Disperse inks depending on the purpose of use. ④ Pigmented Ink - It is used mostly for textile design printing & T-shirt printing. Thin fabric such as polyester, georgette, polyester-georgette, chiffon etc. can be also suitable fabric for this ink. Needs high temperature for fixing the inks, but no steam is required. Properties Required of Ink-Jet Dyes: The two major classes of colorants, namely dyes and pigments. The choice of dye depends upon the ink used, whether it is aqueous, solvent or hot-melt and on the type of printer (thermal or non thermal). However irrespective of the solvent system, all ink-jet dyes have to satisfy a number of stringent criteria. 7 | P a g e 1. Color: Though Black is the predominant color, for full color printing the three subtractive primary colors of yellow, magenta and cyan are also required. The key parameters are the absorption maxima (peak wavelength), and the shape of the absorption curve, in particular its broadness and the presence (or absence) of unwanted secondary absorption. Ideally, bright dyes (which have narrow absorption curves) are required in order to produce a comprehensive balanced color gamut because bright dyes can be made duller (e.g. by adding a shading color such as a black), but dull dyes cannot be made bright. 2. Color Strength: The color strength of the dye should be as high as possible for several reasons. One reason is to enable prints having high optical densities to be produced, Other one is the increased flexibility possible in the ink formulation. The ink staprecipitation and also kogation on thermal ink-jet systems. 3. Solubility: A dye for ink-jet should have as high solubility as possible to minimize any tendency for the dye to crystallize and cause problems such as nozzle blockage. Generally greater the number of sulfonic acid groups per molecule, the greater the water solubility. Carboxylic acid groups, especially in the form of salts, also confer water solubility on dyes. 4. Electrolytes / Metals: 8 | P a g e Anion such as sulfate and especially chloride are undesirable in ink-jet inks due to the corrosion problem they cause to the metal print heads. Certain metal cations particularly divalent cations such as calcium, need to be removed, since these can precipitate with certain anions such as sulfate and with dye itself so the permissible amount is 100 ppm. Which is generally accomplished by dialysis or ukrafihration8 5. Light Fastness: The final printed document must have reasonable light fastness (resistance to fading by light) if it is to serve any useful purpose.