Fast production, high quality, unlimited customisation options and ease of use are just some of the benefits of direct to garment digital printing. Here Niki Tait looks at a range of flexible systems and processes that are available to manufacturers of short clothing runs.

Digital printing technology has come a long way since its introduction in the early 90s, and today high quality, durable, multi-colour prints can now be achieved even on dark fabrics, and digitally-printed garments are breathable and comfortable to wear.

Digital printing is not intended to replace high production screen printing, but is aimed at flexible, fast moving, shorter runs ranging from a single garment up to 2,000 pieces, though upwards of 6,000 have been claimed efficient.

It eliminates the need for screens, with negligible set-up times. And unlike other forms of print the images can be scaled to match the garment size, from a child's extra small to a full size XXXL, without adding cost.

Digital inks can be used on a wide variety of fabrics including cotton, Lycra, 100% polyester and blends, though print calibrations need to be set for different fabrics.

And, as with traditional transfer printing, the equipment needed depends on production scale, from a single bed to multiple bed printers. Different units use different types of ink: water based, solvent based and dye based.

Digital printing machines
Kornit Digital Ltd claims to have been the first company to introduce industrial digital printing machines which print directly onto garments, and it now offers a range of high speed units developed for short and medium runs, as well as personalised and variable data printing with a resolution up to 630 dpi (dots per inch).

Kornit has also developed pigmented solvent based textile ink for vivid colours and high image resolution. The inks are machine washable as well as UV resistant and prints are cured in conventional hot air or infrared dryers.

The mass production model Kornit 931D can print at up to 630 x 630 dpi and at speeds ranging from 172-295 light coloured garments per hour and 35-100 for dark colours depending on resolution.

Piezoelectric drop on demand ink jet print heads are used, each with 256 nozzles. Four heads print the CMYK colours (cyan, magenta, yellow and black) and two others print Kornit's new white solvent ink which allows printing on dark substrates.

Shima Seiki, famous for its 'WholeGarment' knitting systems, addressed the problem of printing a seamless garment some years ago with its SIP 100F direct ink jet garment printer. This recognises the edges of a garment laid flat and prints the whole area.

This is a small machine suitable for T shirts, but Shima Seiki recently introduced the much SIP 160F for larger items such as dresses and coats.

Both the SIP 100F and SIP 160F enable full colour printing on a variety of fabrics, using design data created on the Shima Seiki SDS ONE apparel design system. SIP uses advanced piezo inkjet technology and divides the basic CMYK colours into light and dark tones.

Prior to printing, the garment is treated in the SUM100 Pretreatment Unit which sprays the fabric with a special pre-treatment formula that improves colour quality and enables saturation without bleeding.

Twin rows of printing heads
The US Screen Printing Institute has introduced a new Fast T Jet Pro HV T shirt printing machine where twin rows of eight Seiko heads print five shirts simultaneously.

There are two carts so whilst one set of five shirts is being printed, the other can be reloaded ready to feed straight in. The effect is a continuous production system capable of printing more than five shirts a minute.

It is based on the Artistri 2020, from DuPont Ink Jet, which US Screen has gained exclusive rights to modify for T shirts.

The Texjet by Polyprint prints directly on T shirts and cut fabrics using washable textile pigment inks and Piezo ink jets. Images of 20 x 25cm at 720 dpi can be printed at speeds of up to 60 T shirts per hour. Inks are then set at 150ºC for 2-5 minutes using a heat press or dryer.

The GT 541 inkjet garment printer from Brother International has a printable area of 14 x 16 inches and uses CMYK water based pigment inks to print on cotton and poly/cotton at speeds of under a minute per garment for many designs.

MS Italy offers the Ms Zero and Ms Zero White Edition ink jet piezo printing machines which are suitable for T shirts, shirts and trousers. The inks need fixing for 90 seconds at 170º using a heat press or drier.

The Mimaki GP-604 is a direct to garment flatbed printer for T-shirts, scarves, aprons, bags, towels, etc, using Mimaki's pigmented textile ink for full graduated colour on dark T shirts. A4 size images, in high resolution, can be printed in about a minute.

The machine is equipped with a piezo drop on demand print head and is capable of a print area of 60 x 42cm, with resolution up to 720dpi. The GP 604 has a single print station, but Mimaki also manufactures a three station printer.

Vibrant effect
Impression Technology Europe offers the DTG range of ink jet garment printing machines. When printing in standard colour mode, seven inks are used which include light versions of cyan, magenta and black.

However, with its latest technology, white ink replaces these light inks. Using specially developed software the machine lays down a white base onto which the CMYK inks are printed to give a vibrant effect.

The Kiosk, the Bullet and the Xpress make up the machine range with different print areas. Print Pro works with Adobe Photoshop files and is able to work out the placement and density required for the white ink.

ATPColor's ATP M 54 has been developed for printing garments such as T-shirts and objects with a thickness up to 4cm. The piezo technology enables the use of pigmented, subliming, reactive and acid based inks. Productivity can be as high as 50 T-shirts per hour, and a resolution of 1440 x 1440 dpi can be achieved.

The 2800 x 1440 dpi resolution T-Jet from CADlink Integrated Solutions uses special pigmented textile dyes requiring a short heating time to achieve a full colour fast cure.

Maximum printing size for the T-Jet Standard is 12.5" x 19" and it takes 2-2.5 minutes to print a full-size image on a T-shirt.

Niki Tait, C.Text FTI, FCFI heads Apparel Solutions which provides independent assistance to the apparel industry in the areas of manufacturing methods, industrial engineering, information technology and quick response.