Sublimation Printing Process (Heat Transfer Printing)

Transfer printing is the term used to depict textile and related printing forms in which the outline is first imprinted on to an adaptable non-textile substrate and later exchanged by a different procedure to a textile. It might be inquired as to why this shrewd course ought to be picked rather than straightforwardly printing the texture.



Present day sublimation innovation which has made it simple to enter the universe of computerized clothing printing. New advances in sublimation printing frameworks have yielded HD and photographic printing quality, a huge scope of hues choices, quicker printing and drying velocities and basic setups at our clients put.

Sublimation printing is a procedure that requires six principle elements -
  1. Inkjet Printer, 
  2. Sublimation Ink, 
  3. Transfer Paper, 
  4. RIP Software, 
  5. Heat Transfer Machine and 
  6. Fabric
Heat exchange presses have been utilized for the color sublimation printing of polyester and different textures for more than 30 years.

The process is environmentally clean and the vibrant colours and clear images give the process many advantages. Heat Transfer printing is the primary step in apparel manufacturing operations utilizing the increasingly popular agile manufacturing.

Heat Transfer printing is the perfect medium for the demands of today’s marketplace & short run and sample production. Digital-print textile technology and heat transfer processing have the advantages of facilitating the reproduction of several colours, reducing post-processing, and lowering equipment investment and maintenance. Because it is simple, cheap, easy to reproduce colour, and does not need post-treatment, this process has its advantages when looking for a quick and easy way to print on fabrics. Heat transfer temperature and dwell time are the two key factors affecting colour reproduction on polyester fabric. 

Heat presses can heat a transfer up to 218 degrees and can press between 40 and 80 psi (pound per square inch) (0.276 and 0.552 MPa). This value only represents the amount of air pressure brought to the machine and is displayed on the air gauge. The actual applied pressure (2 to 6 psi) is calculated from the cylinder size and the plate area. 

A heat press is a machine used to transfer a design from transfer paper to the object. Transfers done with a heat press permanently adhere to the object. The high pressure and temperature have a considerable effect on the properties of the printed fabrics.

Many scientific papers have dealt with the topic of heat transfer printing or dye-sublimation printing and have tested the quality of printing and researched the dye used. However, it is also necessary to look at the changes in the properties of the fabric (linked to the structure) which have been dye-sublimation printed. It is assumed that the changes in the fabric due to dye sublimation printing are induced by the following parameters: temperature, dwell time and pressure. These changes are reflected especially regarding comfort (air permeability, water vapor permeability) and durability (strength, elongation, thickness).

Image Creation & Preparation


A design room and image preparation
The initial step is to make or set up a picture for sublimation. General, the objective is to make the most elevated quality picture conceivable. Sublimation, like some other type of advanced enrichment, is just a way to create a picture on a substrate (i.e. fabric).

In spite of the fact that sublimation has the capacity of rendering completed pictures with an extremely high level of detail, clarity, and sharpness, the final product will never be better than the initial image.

Think about the PC expression GARBAGE IN = GARBAGE OUT while making your fine art. On the off chance that your underlying picture is low in quality, at that point it's consistent to expect that the sublimated picture will be as well. To get staggering outcomes, you should produce dazzling pictures amid the creation arrange, as the printing and squeezing stages will just copy what is created in the creation organize.

Sublimation Printers

A sublimation printer
Printers fall into two main categories: small and large format. Small format describes all printers under 42” in print width, whereas large format references printers that are capable of printing images wider than 42”. In general, small format printing is also referred to as desktop printing and wide format printing is referred to as industrial printing.

Piezo Electric Heads


Though small format sublimation printing utilizes desktop inkjet printers, it doesn’t mean that just any office style printer will work. Only printers that do not use heat to print are capable of working with sublimation inks. Piezo-electric print heads, a proprietary technology of the Epson Corporation, use a piezo crystal at the back of the ink reservoir. This is rather like a loudspeaker cone - it flexes when an electric current flow through it. Whenever a dot of ink is required, a current is applied to the piezo element causing the element to flex, which in turn forces a drop of ink out of the nozzle. No heat is generated in the process; thus, the sublimation ink is not prematurely turned into a gas, which would happen if using the standard thermal print heads found in most brands of desktop inkjet printers.

There are several advantages to the piezo method.

First, the process allows more control over the shape and size of ink droplet release. The tiny fluctuations in the crystal allow for smaller droplet sizes and hence higher nozzle density. Also, unlike with thermal technology, the ink does not have to be heated and cooled between each cycle. This saves time and the ink itself is tailored more for its absorption properties than its ability to withstand high temperatures. This allows more freedom for developing new chemical properties in inks.

Resolution

Most of today's inkjet printers are capable of well above 720 dpi even as high as 5600 dpi. These super high resolutions are not needed for dye sublimation as you should never print above 1440 dpi and 95% of the time you will only need to use a maximum of 720dpi. Any subtleties you may gain using one of the higher dpi settings will be lost when the ink turns into a gas for the sublimation process.

Resolution is a measurement of image quality. In general, an increased amount of resolution means that an image is sharper and displays more detail. Every raster digital image whether a scanned image, a printed image or an image displayed on your monitor is composed of tiny dots. The more dots in a given space, the greater the resolution will be. When dealing with graphics files there are three properties that go into determining the resolution of an image file: pixels, dpi and inches.
PIXELS - Refers to the total number of 'dots' both horizontally and vertically that make up the file. This is the actual resolution of the file. Once a raster image is created, the total number of pixels is fixed. 

DPI - Refers to the number of 'dots' or pixels per each inch of a printed or scanned document. The more dots, the higher the quality of the image.
INCHES - Inch is a linear measurement that refers to the actual physical size (either printed or scanned) of an image. The following formulas illustrate the relationships between the different parameters that define resolution.

  • Pixels = inches X dpi 
  • Dpi = pixels/inches 
  • Inches = pixels/dpi
An example: An image is created in Photoshop at 300pixels x 300pixels with a dpi of 100. What is the actual size in inches?

Width: 300pixels/100 dpi = 3 inches
Height: 300pixels/100 dpi = 3 inches
Image size will be 3” x 3”

Transfer Papers

A high-quality transfer paper designed to support commercial sublimation. Because the paper is the media that receives the sublimated image and transfers it to the item being decorated, it’s a critical part of the process and can have a detrimental effect when an inferior product is used.

Colden hove Papier presents Digital Transfer Papers, a revolutionary range of papers developed for digital transfer printing - the adaptation of the dye sublimation transfer process to advanced digital printing. Jetcol, the only paper that assures, 97% ink release – that means huge saving to achieve lowest running cost and best quality by transferring maximum ink to get brightest colors on Fabric. Because Jetcol papers increase your performance and offer more quality for lower total costs of use by the unique composition of our patented Jetcol papers differs from regular inkjet paper

Digital dye-sublimation transfer paper


Jetcol HTR1000
  • Substance 66g/m2; 
  • High transfer yield offering a wide colour gamut; 
  • Excellent contour; 
  • Fine detail printing; 
  • Allows for 240% ink coverage; 
  • Maximum resolution 540 x 720 dpi.

Heat Presses

Sublimation without a heat press is like a broken pencil – pointless. There are many types and sizes to choose from depending upon your products and since sublimation requires precise temperature and pressure, it’s imperative that you invest in a good quality unit.

The flat (flat platen) press is available as a clam-shell style or a swing-sway style. The clam-shell version opens and closes like a clam, where the bottom platen is stationary and the top platen moves up and down. The swing-away press opens by lifting up the top platen, but then will move sideways completely out of the way for ease of placement and removal of transferred products. This process is done mainly under a temperature of 1500-1900C at 2-3 bar pressure, and with different time according to the quality of the product mainly from 5 sec- 60 sec.

About the Author
Priyabrata Mondal is a graduate in apparel production. Currently, he is pursuing his master degree in Fashion Technology at NIFT, New Delhi. His interest is in apparel supply chain.

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