Aug. 23, 2022
The digital textile printing industry has seen rapid growth over the last decade as more & more users shift towards the digitalization of textile printing. The use of digital printers allows one to inculcate ease, simplicity, fabric performance, consistency, and most importantly an enormous variety of colors in textiles thus making the whole process reliable & cost-effective overall. Several processes come under the umbrella of printing textiles digitally. In this article, we will be mainly discussing the DTF printing process (Direct to Film Printing) process.
As its name indicates, DTF printing involves printing an image on a film and then transferring that image, via a heat press, to a fabric.
The requirements for DTF printing do not demand a heavy investment from the user. Be it, someone who is currently engaged in one of the digital textile printing processes mentioned above and wants to shift to DTF printing as an extension of the business, or someone wanting to venture into digital textile printing starting with DTF, one has to invest in the following:
What the films used in DTF printing is called PET film that’s different from screen printing, and the PET film is about 0.75mm, which makes it has good transferring quality. These PET films are also known as DTF transfer films. These films can be cut for pieces and one time usage. It can be classified into two types according to the temperature, which are cold-peel films and hot-peel films.
Consisting of granular, the hot-melt powder is a kind of binding material. With hot melt powder, the color can penetrate into the surface of texture better.
This device helps to transfer the printed image on the film to the desired surface or fabric. You can also use this machine to melt the powder on the DTF film.
Software is an integral part of the DTF printer. This is because the software will affect the color performance, ink printing characteristics and final printing performance. For DTF printing, you will need special RIP software to handle your white and CMYK colors. This is necessary because the software manages the color’s quality, drop size, ink level, and several key factors that contribute to print quality.
The ink used in the printer DTF is a unique pigment designed as cyan, yellow, magenta, white and black. White ink is the basis of your printing, while color pigments print patterns on film.
This is a small industrial oven used to melt the hot-melt powder of the printer and put it on the transfer film. Alternatively, you can use a hot press to perform this function. However, it is helpful if you use the hot press in non-touch mode.
Instead of regular paper, insert the PET film into the printer trays. First, print the entire image in white on the PET film. After this, using the appropriate color settings in the printer, print the required image on the white image layer. The important point to remember is that the print on the film must be a mirror image of the actual image that needs to appear on the fabric.
This step is the application of hot-melt powder on the film that has the printed image on it. The powder is applied uniformly when the ink is wet and the excess powder needs to be removed carefully. The important thing is to ensure that the powder is evenly spread all over the printed surface on the film.
One very common way to ensure this is to hold the film at its short edges such that its long edges are parallel to the floor (landscape orientation) and pour the powder in the middle of the film from top to bottom such that it forms an approximately 1-inch thick heap in the center from the top to the bottom.
Pick up the film together with the powder and slightly bend it inwards such that it forms a slight U with the concave surface facing oneself. Now rock this film from left to right very lightly such that the powder will slowly and evenly spread all across the surface of the film. Alternately, one can use automated shakers available for commercial setups.
As in the name, the powder is melted in this step. This can be done in various ways. The most common way is to put the film with the printed image and the applied powder in the Curing Oven and heat. If the curing oven is unavailable, place the film inside the heat press and bring the top of the press very close to the film but not touching it.
There should be around a 4 to 7 mm gap between the film and heat press top plate. One can use a metal wire to fasten the press top such that it does not close over the film and leaves a necessary gap. For best results, it is highly recommended to go by the manufacturer’s specification for powder melting. Depending upon the powder and equipment, the heating is generally done for 2 to 5 minutes with the temperature around 160 to 170 degrees Celsius.
The step involves pre-pressing the fabric before the transfer of the image by the film. The fabric is kept in the heat press and pressurized under heat for about 2 to 5 seconds. This is done to flatten the fabric and also ensure de-humidification of the fabric. The pre-pressing helps in the proper transfer of the image from the film onto the fabric.
This is the heart of the DTF printing process. The PET film with the image and the melted powder is placed on the pre-pressed fabric in the heat press for a strong adhesion between the film and the fabric. This process is also called ‘curing’. The curing is done at a temperature range of 160 to 170 degrees Celsius for approximately 15 to 20secomds. The film is now firmly attached to the fabric.
The fabric and the now attached film on it must cool down to room temperature before one pulls the film off. Since the hot melt has a nature similar to amides, as it cools down, it acts as a binder that holds the colored pigment in the inks in firm adhesion with the fibers of the fabric. Once the film is cooled, it must be peeled off the fabric, leaving the required design printed in ink over the fabric.
This is an optional step but is very highly recommended for best results and high-performance parameters like wash and rub fastness. In this step, the final fabric with the transferred design is pressed in the heat press for around 10 to 15 seconds.
✓ DTF films are available in the form of cut sheets, which can be used for a small scale use, and rolls, which are typically used in a larger, commercial operation.
✓ The films used in the DTF process allow for the transfer film to be peeled away safely from the heat pressing step a few moments later, after the pressed image has cooled (a cold peel).
✓ DTF printing is also faster than DTG printing when doing multiple prints.
✓ DTF prints result in sharper, vivid detail because the images are printed to a film instead of a fabric.
✓ Software is a key component in the DTF printing process. The software can direct such things as the print characteristics, color performance of the inks, and image sizing, factors which contribute to optimal print results.
✓ The DTF printing process is easy to learn and does not require highly skilled operators.
Let’s talk a little about the DTF printing pros & cons.
Works with almost all types of fabrics
Does not require pre-treatment
The Fabrics thus designed exhibit good wash characteristics.
The fabric has a very slight hand feel the touch
The process is faster and less tedious than DTG printing
The feel of the printed areas is slightly affected when compared to that of fabrics designed with Sublimation printing
As compared to sublimation printing, the color vibrancy is slightly low.
Overall one could say that the DTF process practically lifts all restrictions that are commonly encountered in other textile printing processes especially when it comes to choosing the fabric to print on. Since pretreatment is not essential, in many cases, the overall cost of printing is brought down hence offering a higher profit margin.
The textile printing industry is predicted to see massive growth as more and more fabrics manufactured by DTF will come into the picture. In conclusion, the DTF printing process can be thought of as an effective way to produce fabrics economically.
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