Large format digital printing technologies have been serving multiple markets for over thirty years. They were conceived to work in the field of visual communication and graphics. Over time, thanks to the evolution of inks and performance, they have also reached the textile industry . Large format plotters soon made inroads in the fabric flags and banners market, to then reach fashion and the most extreme fashion.
This was possible thanks to two technologies:
- print heads with piezoelectric technology
- sublimatic inks with special formulations, with nanodispersed dyes.
Sublimatic printing is particularly in demand today because today there are fabrics rich in polyester on the market but very similar to the touch to natural fibers, more complex to print. Sublimatic ink, in fact, binds well to polyester fabric, pure or with percentages not lower than 40% (mixed-polyester).
Why is it called “sublimation printing” or “sublimation printing”? Definition
Let’s start with the basics. It’s called ” sublimation printing ” or ” sublimation printing ” because the inks attach themselves to the polyester fabric through a sublimation process . When a solid transforms straight into a gaseous form, this process is called sublimation. If you want sublimation printing in Dallas then you can contact us as we provide the best sublimation printing services.
How do sublimation inks work?
Sublimation inks , or sublimation inks , are a type of “disperse” inks. It means that they chemically bond to the polyester. They are used in sublimation inkjet printers.
Through the application of heat and pressure they pass from a solid to a gaseous state and then return to a solid state on the polyester fabric. This particular process serves to keep the sublimatic dye inside the fiber of the fabric, where it is fixed by heat and pressure. The heat and pressure is exerted by a calender or heat press (heat press) .
Sublimatic inks are “alive” inks, in the sense that they contain components that tend to oxidize and “degrade” rapidly when exposed to light, air and sudden changes in temperature. This can lead to fungal growth in the hydraulics of the printers. These characteristics have made this technology the exclusive preserve of plotters equipped with piezoelectric inkjet heads. In fact, the thermal heads as they are conceived today would cause the “self-sublimation” of the ink even before it is sprayed.
How is thermal sublimation printing done?
Sublimation printing on polyester fabric can take place in two ways:
- direct sublimatic printing on the fabric , with subsequent thermofixing of the ink in a calender or hot press
- indirect sublimation printing , by printing on a special paper designed for transferring the ink onto the fabric through a calender or heat press ( transfer paper ).
As you can see, all these processes take place hot. In fact, printing with digital sublimation ink requires the aid of heat and pressure in order to be transferred and maintained in the fiber of the fabric. Pressure and heat are generated by the calender or heat press.
Each of the two manufacturing methods has pros and cons. In general, sublimation digital textile printing is well suited to both cases.
Direct sublimation printing
Direct is the simplest type of sublimation printing from the point of view of the process. The sublimation large format digital printer prints the graphics directly on the polyester or polyester-blend fabric . At the end of printing, the fabric reel is passed through a calender or heat press to heat-fix the sublimation ink to the fabric fiber.
Indirect sublimation printing with transfer paper
The indirect sublimation inkjet printing process requires that the plotter does not print the fabric directly, but a specific paper. This is called ” transfer paper “.
The graphics are printed on the paper in a mirror image . In this way, once the paper is coupled to the fabric , the ink will transfer from one to the other, returning a straight, legible image. The transfer of the ink from the paper to the fabric takes place thanks to the heat and pressure generated by the calender or heat press.
From plotter to transfer paper, the ink solidifies and dries quickly. Once the paper is coupled to the fabric, the ink held up to there by the paper sublimates, transferring onto the fabric.
How is a sublimation printer made and how does it work?
A dye-sublimation printer is, of course, a roll-to-roll printer . There are printers of various sizes, from 1.6 to 5 meters . Rolls of polyester or polyester mix cloth may be used with any sublimation printer.
Some dye-sublimation printers have an inline or even built-in calender . A calender or even a flat heat press is often used as a separate ink fixing device in sublimation printing systems.
Press or calender for direct or indirect sublimation
As we have said, there are two possibilities to actually make sublimation ink:
- the thermal calender
- the heat press (or heat press ).
The rotary type thermal calender for sublimation
The rotary type thermal calenders allow the thermal transfer of the ink from the paper to the fabric. This process is called calendering. To provide the greatest possible outcome, modern equipment enable precise regulation of both temperature and pressure. They are obviously ideal for reel processing. The size of the operating light must be, for obvious production reasons, equal to or greater than the printing reel.
The rotary type thermal calenders also allow the sublimated ink to be fixed directly on the fabric (instead of passing through transfer paper). This ensures a better hold over time, in the case of roll-to-roll printing.
There are different types of rotary type calenders, with different types of options, to best adapt according to the type of application produced:
- visual communication
- sports products and sportswear
- fashion industry.
The evolution of calenders for thermal transfer of sublimatic ink was seen during the years 2000 and 2010. Today it is difficult to find real innovation or witness a revolution in this market. Few manufacturers have been able to successfully meet the growing demand for sublimation printers equipped with superwide format inkjet printers with 3.2 and 5m printing light. Currently the market leader in the sector of superwide format digital textile sublimation calenders is Monti Antonio, a historic manufacturer from Vicenza.
Sublimation heat press for both direct and indirect use
Two distinct kinds of thermal transfer presses exist:
- without vacuum table for the vacuum effect; of this type are usually format presses for T-shirts or larger ones for the fashion and soft signage sector
- with the vacuum hob : these guarantee the best possible result in any condition. They are mainly used for applications in the fashion and soft signage sector.
For the fashion sector, some manufacturers have introduced specific options to reduce manual interaction when handling transfer paper from reel to piece of fabric.
As with calenders, there was an evolution in the world of fixed platen heat presses in the early 2000s . Here the advent of the vacuum (vacuum) has significantly increased the possibilities of working in the piece. And bifaciality has had interesting application developments in sport and in textile graphics for communication.
Double-sided sublimation printing: myth or reality?
Penetration of the ink on the back of the fabric is absolutely possible. It is controlled by several variables:
- specific pre-treatments
- amount of ink deposited on the substrate. In this case, a good “push” is needed, deriving from the pressure exerted by the calender, which must be of the vacuum type . In other words, it must be able to generate the vacuum effect to allow the ink to pass very rapidly to the back of the support.
Obviously the back will never be as perfect from an aesthetic point of view as the front, but very similar. Observed from a distance of a couple of meters it will be difficult to see the difference. The thicker the fabric, the lower the quality of the double-sided effect is usually.
The transfer paper for sublimation printers
Transfer paper is a particular type of paper used in indirect sublimation digital printing . It is treated on the surface to accept the sublimation water-based ink without altering its characteristics until it is transferred onto the fabric.
In the past years all the main paper mills specializing in coated paper for inkjet printing have been able to produce and offer the market ever better substrates. Transfer papers capable of maintaining dimensional stability at any speed and ink load and capable of maintaining the writing quality intact after sublimation on fabric.
Sublimation paper weights vary a lot . To be selected:
- depending on the final result or the application to be created
- depending on the type of fabric on which the ink will be transferred
- in relation to the quality and type of calender present in the company.
Fabrics composed mostly or primarily of polyester that may be used in both direct and indirect sublimation printers
A small introduction to the world of fabrics. We can divide them according to the fiber they are made of, but also the type of weaving . The most common ones are precisely the “fabrics”, produced by weaving perpendicular threads. They can have a simple weave, but also more complex weaves, so as to produce particular designs or figures with yarns: there is a practically infinite number of ways to weave warp and weft.
The weave determines not only the look of the fabric (such as sheen) but also its hand (the feel when you touch a fabric), permeability, drape, dimensional stability, stretch, strength, and weather resistance. ‘abrasion. That’s why it’s critical to have a firm grasp on how to choose fabric for a certain application. In particular, the last five characteristics (drape, dimensional stability, elasticity, strength and abrasion resistance) are very important when it comes to digital textile printing and media handling throughout the entire printing process, especially if industrial.
Polyester is a polymer synthetic fiber . It can also be used mixed with other natural fibers (cotton) or synthetic fibers (nylon, polypropylene, Lycra).
Choosing the best polyester or polyester blend fabric for your sublimation printers is critical. This choice results in:
- print speed
Not only. Each sector of use of finished products has different characteristics. For example, a polyester backing used in the soft signage industry needs to be lightweight and wrinkle-free so that it can be easily folded and unfolded, thus saving money on shipping.
Is there anything you could use instead of a sublimation printer?
To date, the only non-piezo inkjet head technology that has partially replaced direct-to-textile dye-sublimation is HP Latex Thermal Technology . The alternative is possible only for some specific applications in the graphics and visual communication market. There are still no known developments regarding the application of sublimation with own thermal inkjet technology. This is because the thermal shock necessary for the formulation of the drop would damage the ink itself directly in the print head.
What are the evolutions of sublimation printing today?
To date, sublimation printing has arrived everywhere . It’s hard to find a digital textile printing market where it hasn’t established itself. In the same way, the sublimatic thermal transfer of the ink has also been used in other industrial markets , where the surface to be decorated is provided with a polyester coating.