Textiles special report
Ironing out digital textiles
There are man misconceptions about digital textile printing. Sophie Matthews-Paul explains the why's and wherefore's.
All the talk surrounding digital textile printing seems to confirm that this is a growing market, and one which is open to display producers and print service providers who want to take up the challenge of printing to fabrics as well as to their existing ranges of flexible and rigid materials. But this sector of the inkjet market is still steeped in confusion for the many who feel that the processes involved are complicated and expensive. The businesses who have moved into digital print from a traditional textile background have found, not surprisingly, the move to be relatively straightforward as they are already appreciative of the different type of handling and production required when working with textiles. However, for the first-time investor in this market sector, with little or no former knowledge of the machines and technologies involved, there can be a sharp learning curve. If global figures and forecasts are to be believed, and there's no reason why they shouldn't be, the overall value of the digital textile printer market four years ago was estimated to be some $2 billion dollars with growth planned at 25 percent by 2010. Some countries have been far more accepting of this technology than others and, within Europe, Britain has seen to be lagging behind in its use of printing to fabrics. No longer merely linked to fashion, sampling and few exclusive furnishings and wall-coverings, more output onto fabrics should be hitting the mainstream in digital output but, in the UK, this isn't happening. Specialist print service providers concentrating on this area have found themselves in a secure market niche but many of these are names with a longstanding in textiles and expertise formerly in analogue techniques which has now been adapted to encompass digital print. In terms of the types of machine being used to print direct to textiles, the best-known technology in our sector is dye sublimation, particularly in wider-format applications. This technique has been used with success for many smaller products, including gifts and garments, and is not necessarily restricted to polyester based fabrics when used in larger formats. In principle, material which has a polyester coating can be used via this process, but it is subjective; in addition to being suitable for the sublimation process it relies also upon the heat resistance of the end substrate. With stronger environmental efforts and greener practices now coming into effect, many conventional display materials, such as PVC based media, can now be printed onto those with a polyester content. Sublimation is an obvious way to produce a wealth of signs and displays in addition to furnishings and wall coverings. Many of these fabrics are beneficial for recycling purposes and other logistical advantages can also be factored in, such as reduced weight which lowers delivery costs and simplifies handling. Many can be washed without significant degradation and the likelihood of textiles creasing or tearing is also reduced.Textile printing machines within the display market have been dominated by dye sublimation units, either direct to the material or as part of a configuration which involves printing onto a transfer sheet before being applied, via heat press or calendering unit, onto the final material. This latter process has the advantage of extending the range of materials that can be used, dependent only on the capabilities of the transfer system; the carrier method means that the final media is not involved with the printing machine.
The engines of many of today's machines have been used as the basis for textile printers, both direct and for using the transfer method of dye sublimation. In addition, there are systems which use other types of inks or dyes for outputting onto natural and man-made materials. Acid dyes are used primarily for printing onto silks, nylon and wool whilst, for cottons, linen and cellulose fabrics, reactive dyes are needed. Generally, pre- and post-processing of materials is involved, such as steaming and washing as part of their fixation. Particularly in the lower price bracket for textile printing machines, direct printing systems have evolved from existing wideformat inkjet printers, such as models from Roland or Mutoh, which have been modified to handle both disperse inks and the sublimation within a single unit. But the convenience of this has often been let down by the lack of colour density in the finished job and difficulties in controlling the density of the dyes and the colour accuracy required. Most of these converted solutions use Epson-based printhead technologies but, although sign-makers and display producers show an interest in printing direct to fabrics, the complexities of working with alien inks and materials tend to restrict their choices of machine, particularly if these potential users have no prior knowledge of digital textile production. Within the UK there are specialist suppliers who concentrate on the digital textile sector such as iSub, now a specialist in the educational sector as well as to mainstream print service providers. This company has a range of printers starting with smaller format Epson units through to Mutoh, Mimaki, Roland and ATP Colour machines for dye sublimation, and it also offers heat presses and other peripherals. Other suppliers include DCP Systems, which offers textile printing units, along with inks, carrier papers and heat presses, and RA Smart, a well-known for being a supplier of all types of digital textile printers as well as a producer of broad range of output for different end uses. The structure of textiles is such that they do not contain stable properties during printing. A printing machine will require tensioning and a specially designed feed plus holding belts to prevent unwanted stretch and distortion during processing. Because of the absorbency in fabrics, there can be considerable waste of ink or dye which soaks through the material being printed and needs to be drained away to avoid unwanted staining of colorant on the reverse side of the fabric. As with many flexible media, when printing direct to textiles, the wider the printing machine the more critical the handling of the fabrics to gain even and accurate coverage across the entire width. Dividing the market into the types of textile printer available puts the process into three distinct categories. High-end machines which can handle throughput at up to 150m2/hr include options such as the Regianni Dream, which uses HP's Aprion printheads, and the Osiris Isis and Imaje which feature drop-on-demand and continuous inkjet technologies respectively. Within the middle bracket in terms of machine capabilities are printers from HP Scitex and EFI Vutek which can be converted to provide dual capabilities with solvent-based inks and dye sublimation. An interesting turnkey solution is found in the Hollanders Colorbooster system which comes in a choice of options depending on the type of end application being printed, covering furnishings, fashion, sampling and soft signs and flags. Other specialist examples include the Robustelli Monna Lisa, which uses specialEpson printheads, and machines like the Konica Minolta Nassenger.
Probably of most relevance to digital display producers wanting to venture down the textile route are the machines which look familiar in that they're adapted from existing units but have been modified for dye sublimation. Although Roland and Mutoh also produce their own units for this type of printing, with Mutoh's range including both two-stage and direct printing with its Viper models, there are many third-party manufacturers and suppliers offering their own versions, such as Flex-Europa, D-gen, BeDigital and ATP Color. If a machine resembles a Mutoh ValueJet, for example, there's every chance that the original engine is exactly that but, from a modification point-of-view, it makes perfect sense to use an existing, successful chassis from which to effect conversion into a textile printing unit.
The situation with Mimaki is slightly different. Fewer of this company's printers are modified by third parties into dye sublimation versions. Although the company has a good selection of textile printers which are designed purely for that purpose, it's interesting that it also has success with its own conversion of its popular JV series to bring to market a greater choice of wider machines for fabric output. Mimaki has the lion's share of digital textile printer sales in the UK, with colleges and fashion houses tending to use its solutions - which also include printers using acid and reactive dyes as well as sublimation. The majority of lower end printers seem to be based on existing bodies; Seiko's Color Textiler 64DS is based on a chassis which is familiar to ColorPainter and HP DesignJet 8000 users and is a 1.6m printer using oil-based sublimation inks as part of a two-step process using a heat press. Seiko I Infotech was one of few companies originally offering an oil-based wide-format inkjet printer and, thus, its experience of this ink type has made it a logical step to modify it for sublimation printing. Another departure from the ranks of Epson-based printers in the textile category is the Konica Minolta Nassenger which, not surprisingly, features KM printheads and can be used with disperse, reactive and acid dyes with additional dark and light options aimed at improving gradations in tones. This machine is unusual in that it has an electrostatic holding system instead of a belt drive which keeps the material in place, claiming it gives stability without complicated tensioning, and making it suitable for thin and stretchable fabrics. As its name suggests, Robustelli is an Italian company, based in the Como region which is the heart of the country's textile printing industry. As such, it's responsible for producing one of the more established ranges of wide-format textile printers; its Monna Lisa machines are a combination of its own technologies and acquired elements from other manufacturers. This machine range uses Epson printheads; in these printers it is the Type-M variable dot printhead head which is specifically configured to produce a constant resolution with output quality varying according to the numbers of nozzles incorporated into the machine. The Genesta inks used in this printer come in acid, reactive, disperse/sublimation and pigmented versions.
Again, for dedicated textile printing companies, Hollanders is an interesting manufacturer as it has divided the market up into relevant applications and designed its solutions accordingly. For example, as well as catering for soft signs and the display sectors, industrial versions of its equipment are also available for people want to print to heavyweight materials, such as polyester carpet. Where this machine range differs is that it is supplied complete with every element needed for the production and finishing of printed fabrics, including sublimation/fixation units, washing machines and heat cutters. Hollanders isn't tied to any specific ink supplier, and machines can be used with acid, reactive and disperse/sublimation inks. These are serious systems and, as the company stresses, a controlled environment is essential for unattended printing - so climate control, optimised media transport and tension control systems are complemented by its own workflow and colour management. Working with textiles not only opens new revenue streams, but can add an element of creativity and bring environmental benefits. In the garment sector, sportswear has been an obvious contender for the short-run and personalisation benefits able to be gained from digital print; soft signs, flags and banners can also benefit from the move away from screen-printing when low volumes and versatility of output are both required. However, within the UK, greater levels of education are required to explain and outline that many of the conceptions about the complexity of digitally printed textiles are myths and not fact. Not surprisingly, this country has a few dedicated suppliers of machines in this category and these are the companies whose in-depth knowledge of printed fabrics is ready to be passed on to new customers.
There are many reasons why print service providers and display producers have not adopted digital textile printing to the extent hoped for by manufacturers and resellers. For the average wideformat printer user who is using one of the other ink formulations, there's the admission that although the idea of production to fabric appeals as an end application the deterrent is that production is complex, expensive and difficult to learn. Businesses which have used smaller machines for dye sublimation, such as for the production of gift items, mugs and mouse mats, are also wary about the additional learning curve and expense of printing direct-to-textiles. From the perspective of the end-user, such as brand owners, there is little awareness of the ability to print onto fabrics for signs and displays although greener practices these days cannot be ignored by anyone. Additionally, cost, delivery times and quality are the leading considerations between customer and print service provider. However, there is a definite change within the end-user market segment which is seeking more environmentallyfriendly solutions - and digital textile printing can certainly fall into this category