In previous blog posts, I focused on digital printing technology for roll to roll printing of fabric. Digital inkjet systems that support the ability to print on assembled product have also become available and are referred to as Direct-to-Garment or DTG printers. Although it’s possible to use the systems for printing of garment types such as hoodies or small accessory items such as tote bags, DTG technologies are primarily used for t-shirt printing. The last two to three years there has been considerable growth in this technology area and available systems are now being used for direct to consumer applications and by small shops and start-ups for printing of short runs and customized shirts.
Currently available equipment falls into two general categories. The first category includes equipment derived from Epson desktop technologies that have been re-engineered with platens to transport the garment under the printing mechanism. There are numerous vendors for this variety of printer including Anajet, Azon, DTG, Groner, and MS Macchine. The second category includes equipment designed from the ground up. Some of the machines falling into this category make use of more industrial printhead systems to support greater print speed and ensure reliable jetting of the pigment based colorants. This second category of equipment is typically viewed as more robust and there is generally greater cost associated with the purchase of these printers. Vendors of this type of technology include Aeoon, Brother and Kornit Digital.
Both categories of equipment include single and multi-platen technologies. Multi-platen systems offer two or more positions for garment loading. For a dual platen system the machine operator is loading one platen while the second is printing, thus providing increased levels of throughput. To date, most available DTG technologies operate at relatively modest print rates. At the high end of the spectrum, Kornit’s Avalanche printer, a dual platen system, offers a maximum print area of 23.5 x 35 inches and is capable of imaging up to 300 light garments per hour. Brother’s GT-782 model is also a dual platen machine and can print up to 60 light shirts per hour. The larger platen for this device supports a maximum print area of 16 x 18 inches. Aeoon recently joined the ranks with the introduction of a higher speed DTG machine that can be engineered with printhead technology from Fujifilm Dimatix (Spectra) or Kyocera according to customer preference. The Kyocera version supports printing of up to 400 light shirts per hour, offering the highest print rates in the DTG area to date.
Printing of Dark Garments
Unlike their wide format counterparts, the majority of DTG systems in the market have been designed for printing with pigments on both light and dark colored garments. Almost all DTG systems are designed as 4 color devices and most offer the addition of pigment white to block out the foundation color when printing on dark garments. This pigment white is applied in advance of the color and although the method works quite well, it reduces print rates to roughly half that of printing on light shirts. In most instances the dark shirts are pretreated prior to imaging to optimize results and some vendors suggest this operation for printing of light shirts as well. The pretreatment step can be accomplished off-line with a separate machine or spray gun technology or integrated into the printing operation as is the case for Kornit’s printers.
Early adopters of pigment white for Epson based systems found the chemistry inclined to settle out over time and cause clogging of the printhead nozzles. However, experts would suggest that regular cleaning and maintenance of these systems support more reliable performance. In some cases, vendors have also developed on-line ink mixing systems that prevent the settling of the pigment in the ink formulation. An alternate strategy for imaging on dark shirts is offered by Mimaki through the application of a discharge liquid for removing the base color from the shirt. While the use of pigment white produces a shirt with a slightly heavier hand, the discharge method maintains softness and offers a pleasing print effect on it’s own.
Poor color fastness with respect to washing was among the early criticisms of the digital direct-to-garment printing method. Over time, this characteristic seems to have improved assuming correct processing methods have been followed. It has been stated that providing adequate dwell time during the curing procedure is key to achieving fastness properties and conveyer curing systems must be slowed as compared to practices in the screen print environment. In some instances, vendors also suggest drying the print area with a heat press in advance of the printing operation.
To date, best print results have been achieved when printing on 100% cotton garments while printing on blends and synthetics have demonstrated limitations in terms of image quality and color fastness. Given tremendous interest in this application for markets such as team jerseys and athletic garments, shirt pretreatments and ink chemistries will likely evolve to meet needs in this area and some vendors are already advertising this capability for specific fiber types.
Trends in DTG Printing
As I’ve already stated, one of the most important trends in DTG printing is the development of more production oriented systems. The introduction of the Aeoon machine is of particular interest and one of the questions surrounding this device is how the Kyocera KJ4B printhead will perform in conjunction with the pigment based colorants used for DTG. Only time will tell. Additional trends include the introduction of supporting software solutions for enabling print customization, on-line ordering and automation and management of data flow to multiple print machines. These systems are integral to successful adoption of direct-to-consumer and small quantity print strategies that are primary targets for DTG printing.
Ultimately, the development of viable DTG systems will have tremendous impact on production flexibility and sustainability within the garment printing area. Within the current screen print context there can be tremendous color waste associated with over mixing, ink storage and screen cleaning. There is also consumption of water associated with screen engraving and reclamation. The implementation of a digital DTG strategy at the production level will offer an alternative to this scenario and will support small quantity, print-on-demand and rapid replenishment capabilities among traditional volume providers.
For my next blog post I’ll be shifting focus and looking at the topic of product lifecycle management. In the mean time, we welcome your comments and questions regarding DTG and wide format digital textile printing.