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Evolution of Garment Printing
T-shirt printing or garment printing is very different from fabric printing or panel printing as a garment is three dimensional and care needs to be taken regarding the transfer of the color on the lower panel. The machinery involved in garment printing essentially includes a frame in which the garment is inserted so that only the top layer is exposed to the printing head. Digital printing has enabled manufacturers to increase their production more than three fold as compared to screen printing.
T-Shirt screen printing machines are the rotary type with a specified number of screens ranging from 4 to 18. Various models of manual, as well as automatic printers, are available in the market. While manual models have features like indexing pin, multi-directional micro registration etc, the automatic models have servo driven index system, control panels for each station, pneumatic screen clamping, and automatic start-finish, multiprint etc feature making the process easier and more automated.
Screen printing for T-shirt printing works on the same principle as the traditional screen printing process. In the first stage, the screens are prepared according to the design and the number of colours used. For each colour, a separate screen has to be made. There are various processes of preparing the screen, but generally, for the industrial purpose the screen is coated with the photosensitive emulsion and the artwork is made using the lightbox method.
The screen is then loaded. Meanwhile, the t-shirts also need to be prepped for better absorption of colour. Colour recipes are prepared to get the desired hue and dispensed on the screens. The t-shirt is then mounted and the colour is squeezed through the screen and the screen is lifted up. The process is repeated with all the specified number of screens until the design is completed and contains all the desired colours. The t-shirt is then cured for making the prints long lasting.
Automatic machines start from Rs 10 Lakh and can go up to Rs 40 Lakh. The maximum print area is 16” x 18” which is more than the size of A3 paper. The maximum screen size it can accommodate is 23” x 33”. Three types of specifications are available i.e.
- AAA=air lift, air index, air heads
- ASA=air lift, servo index, air heads
- ASE=air lift, servo index, electric heads.
Technologies like touchscreen control panel, servo lift, indexing, electric print head give perfect results. But the drawback inherent to the screen printing always remains. The process becomes repetitive, there is a limitation of colours and the machines become bulky to accommodate all the screens and workstations.
Figure 1: Anatol Titan-M
Figure 2: M&R Gauntlet III
Machines and their brands
Model : Titan 10/9M
Work Stations : 10
Pneumatic and servo indexer in clockwise and anticlockwise direction
-Skip Shirt function
-Smash button halt
-Pneumatically driven print heads
-True three-point micro registration.
Working : Automatic
Model : Gauntlet III Colors: 18
Work Stations : 22
Angle and calibrated pressure adjustments are independently set
Electronically adjustable ink retrieval system keeps ink in the print area
Automatic Pallet Preheat Mode™ with built-in pallet temperature sensor
Compatible with M&R’s Tri-Loc® Rapid Registration System
Working : Automatic
Model : DR-6C6S
Work Stations : 6
Micro-Registration system for precise alignment of Screens
High precision colour registration
With one IR Flasher for Immediate curing
Working : Manual
Heat Transfer (Sublimation)
Sublimation printing eliminates the need of making a separate screen for each colour and the process time is reduced as all the colours are transferred to the garment in one application as opposed to the screen printing where each colour has to be squeezed through a separate screen.
The principle behind sublimation printing is the chemical bonding of the colour with the substrate. Hence it is more durable than the screen prints provided right pressure, temperature and time is used. Sublimation transfer simplifies and reduces the process to just two steps.
- Printing on the transfer paper
- Heat pressing colour on the garment
First step is to print the design by an inkjet printer on a transfer paper. The second step is to transfer the design from the paper to the garment using a heat press machine. Heat press machine consists of a nonstick coated heat plate and a frame in which the t-shirt is inserted and the handle is pressed to bring down the heat plate on to the t-shirt. The pressure of 40 psi is applied at 400o F for 45 seconds so completely transfer the pigments to the fabric. The paper is then peeled off while it is warm. Initially, sublimation printing was used only for polyester fabric but now it is used for a wide variety of fiber contents and blends. (Grifford, 2016)
The machine used to transfer the sublimation print on the t-shirt is called sublimation heat press. It starts from as low as Rs 15000 and goes up to Rs 3 Lakh depending upon the level of automation. Manual machines may have a handle to press down the heat plate while the automatic one operates pneumatically. In automatic presses, there is an option of auto opening but often this leads to a fault called “ghosting” due to the shifting of the garment. Three important factors are considered in a machine i.e. Platen configuration, Platen size and mode of operation (manual or pneumatic). (Lamb, 2017)
Platen configuration specifies how the press opens and closes. Clamshell is the most common type of heat press. Swing away and drawer type is less common. Platen size determines the maximum size of the print. Commonly used sizes are 20” x 24” and 14” x 20”. The heat press is operated either manually or may be pneumatically controlled wherein its air pressure is used to open and close the press and also for applying the pressure.
The major drawback of the heat press printing process is the wastage of transfer paper. For each print, one sheet is required and can’t be reused for more prints like screens in screen printing.
Figure 3: Single Station Heat Transfer Machine
Figure 4: Double Station Heat Press
Digital Printing (DTG)
Digital printing on T-shirts is also called Direct –to- Garment printing. DTG printing eliminates the woes of multiple screens of screen printing and n number of transfer papers of sublimation printing. The process is simplified to the highest degree. Printing directly on the t-shirt is as simple as taking a paper printout owing to this machine. Colour options are limitless (over 16 million colours) and time is significantly reduced as compared to other two technologies. Also, minimum order quantity is not a constraint as in screen printing.
The process of digital printing starts with curing of the t-shirts to attain maximum colour penetration. Then the artwork is prepared using GTX Graphics Lab Software or related software to get a high-resolution file. Then the platen is loaded with t-shirts and the artwork is printed. The printed t-shirt is cured for optimum result. (Brother, 2017)
The only machine required for digital printing is a DTG inkjet printer which can print a high-resolution image on the t-shirt. The artwork should be of resolution 300dpi and higher. The formats accepted for printing are jpeg, png, ai, pdf, psd etc. The essential parts of the printer are cartridge holder, platen, and print head. Platen size can be up to 16” x 20”. Up to 25 mm thick fabric can be printed. (Epson, 2017)
Digital printing enables the production to increase 4 folds and reduces the printing cost by 30 to 60%. Industrial DTG printers like Kornit Avalanche can print up to 150 T-shirts per hour. It is easier to set and the payback period is very less. Hence these days the T-shirt printing companies willing to invest in Digital Direct –To- Garment Printing. (Kornit, 2017)
Figure 5: Epson SC-F2000
Figure 6: Kornit Avalanche DC Pro- Industrial DTG Printer
Machines and their brands
Model : Avalanche 1000
Integrated pretreatment, No need for pretreatment fluids and heat press
Eco-friendly process and biodegradable ink
Integrated humidity system
Printing area up to 23.5” x 35”
NeoPigment™ process- Bulk ink system
Up to 220 t-shirts per hour
24 height-adjustable industrial Spectra Piezo Polaris™ print heads for printing over zippers, buttons and raised objects
Printable substrates- Cotton, Polyester, Cotton- Polyester Blends, Lycra, Viscose, Silk, Leather, Denim, Linen, Wool and more
Model : SURECOLOR SC-F2000
Prints on a wide range of textiles up to 25mm thick on a choice of platen sizes. White ink circulation system and automatic printhead cleaning prevent nozzle blockage and quality variations. USB slot prints repeat order jobs directly. Recommended Substrate Cotton 100%, up to cotton and blend 50%
Although different technology serves different purposes as the quality delivered varies. The technology must be chosen considering all the parameters like the industry, product, MOQ, customer requirement etc. For example, if the requirement never increases above 5 to 6 colours then screen printing can be considered, although if the customer wants to go for multiple colours then digital printing serves best for this purpose. For low investment and new start-up usually, heat press is the most favorable option as the machine cost is minimum and the payback period is very less.