Methods of Printing:
a. By hand
b. By machine
a. Metal stencil
b. Screen stencil
a. Hand screen printing
b. Flat screen printing
o Semi-Automatic flat screen
o Fully Automatic flat screen
c. Rotary screen printing
a. Flat bed press transfer printing m/c
b. Continuous transfer printing m/c
c. Vacuum transfer printing m/c
Block printing is the oldest method of printing. But it still exists though the use is limited.
Printing Procedure of Block Printing:
• Generally block is made from pear wood which is cut so that the design is raised in relief. The size of block depends on the design ranges generally 3” X 4” to Max. 36” X 36”.
• Equipment: Long table, Color pad/blanket, Tray, Resilience pad of woolen felt cloth/foam, Gummy cloth, Back grey.
• The fabric for printing is stretched on a flat table covered with resilience substance and then back grey and gummy cloth.
• The printing paste is kept in a color pad/blanket on a tray.
• The block is pressed into the pad and smeared with colour paste. Then it is pressed upon the fabric so that colored pattern transfer to it.
Advantages of Block Printing:
- Simple to operate.
- Don’t require expensive equipment.
- Multi-colors design can be produced.
- There is no limiting factor in repeat unit.
Disadvantages of Block Printing:
- Slow method, low output & Costly.
- It involves manual work and hence quite laborious.
- Not possible to obtain sharp out lines of design.
- Difficult to join up each impression or repeat perfectly.
Direct style of printing is applied in this method by two ways- spraying or brushing.
Procedure of Stencil Printing:
• The stencil is made from Steel, paper, plastic, laminated.
• The stencil is placed on the fabric and color is applied by means of brushing or spraying.
• It is used decorate knitted fabric.
Advantages of Stencil Printing:
- This is much easier handle than the block.
- The cost of production is low, profitable for small scale production.
- Possible to produce various shade effect.
- Any kind of colour can be used in stencil.
Disadvantages of Stencil Printing:
- Complete circular/rings can’t be obtained and designers freedom is limited.
- Complex design is not suitable.
- Not suitable for large scale production.
- It involves manual work and hence laborious.
Roller printing or M/C printing is the most economical and fastest way of printing. Designs with up to 16 colors present no problem in Roller printing.
A- central pressure bowl
B- layers of cloth/lapping
C- woolen blanket
D- back grey
E- the cloth to be printed
F- engraved printing roller of shell
G- furnisher roller
H- colour box
I- printed fabric
J- sharp edged steel blade/colour doctor
K- brass blade lint doctor
L- steel shaft/mandrel
Working Procedure of Roller Printing:
The fabric to be printed is placed on the central pressure cylinder.
The pressure cylinder comes to the contact of engraved roller by rotating forwards.
The engraved roller is supplied with printing paste by the furnishing roller. This paste is deposited in the engravings as well as applied on the smooth surface.
When the engraved roller rotates, the colour doctor scrapes the excess paste from the smooth surface and allows the paste deposited in the engravings. It makes an impression on the fabric by depositing the paste contained in the engraving.
The lint doctor is placed at an angle against the rotation of the engraved roller to remove fibers & faulty materials.
A number of engraved rollers with separate furnishers, colour boxes, colour doctor and lint doctors are placed around the central pressure bowl to print all the colors required in the design are printed, each roller supplying a part of the design.
Advantages of Roller Printing:
- Suitable for large scale production.
- High speed, hence more production.
- Used for fine printing.
- High quality design
- No joint mark.
- Expensive operation.
- May be light printing shade.
- Crush effect produce.
In this method, a mesh is used to apply printing paste/ink directly onto a substrate.
Factors to be considered for good screen printing:
- The fineness of the screen.
- The fraction of open or non-curved area of screen.
- The hardness of the table.
- The viscosity of the printing paste.
- The number of the squeeze strokes.
- The speed of the squeeze strokes.
- The hardness and X-section of the squeeze blade.
Mechanism/Characteristics of Screen Printing:
In screen printing process, hydrodynamic pressure is built up in the print paste between the squeeze and the screen surface.
The hydrodynamic pressure is inversely proportional to the radius of pores ( ).
The open area percentage of screen plays a role. More open screens allows more paste to pass.
The absorbency of the fibers to be printed and penetration capacity between pores also affect the take up of the paste.
The pores are usually hexagonal i.e. larger at the outside of the screen than the inside that results more color deposited in the areas.
Types of Screen Printing:
- Hand screen printing
- Flat screen printing:
(a) Semi-Automatic &
- Rotary screen printing
Hand Screen Printing:
The fabric to be printed is placed on the table in tension and welded with gum.
Then screen is placed on table and printing paste is given on it.
Paste is attached through screen according to design by moving squeeze 2 or 3 times. As a result engraved design on screen is printed on fabric.
Then dried by heat arrangement below table.
Fully Automatic Flat Bed Screen Printing:
M = Fabric to be printed,
S1-4 = Screen
t = Printing table
d = Conveyor belt
W = Washing device for blanket
I = Device for bringing gum.
Working Procedure of Automatic Flat Bed Screen Printing:
The fabric to be printed is feed to the
printing table. There is an arrangement for gumming the fabric on conveyor belt by a driver.
The conveyor draws forward at speed 5-20 m/min. below screen in equal difference and printing paste mechanically supplied is welded by squeeze through screen.
Automatic squeeze system of individual screen is controlled by mechanically or electromagnetic power with individual motor.
By using different colors in different screens, printing effect of different color is made.
By washing device weld glue on belt can be cleared.
Advantage of Automatic Flat Bed Screen Printing:
Easy and cheap to prepare screen.
The colors have a transparency, purity and richness.
Up to 14-16 color in one pattern can be produced.
Faster than block printing.
Wastage of printing paste is less.
Disadvantage of Automatic Flat Bed Screen Printing:
Joint markers at the repeat often precipitated.
For high production a large table have to be used requiring huge space.
Fine mesh screen used for sharp designs are often chocked.
Production is less than roller printing.
Rotary Screen Printing:
M = Fabric to be printed
S1-4 = Screen
t = Printing table
d = conveyor belt
W = Washing device
L = Device for bringing gum.
Working Procedure of Rotary Screen Printing:
The fabric to be printed is feed to the printing table. There is an arrangement for gumming the fabric on conveyor belt by a driver.
The conveyer belt brings the fabric continuously under the series of rotary perforated screen made of metal foil
The printing paste is fed to the screen by pumps & the squeeze inside each rotary screen forces the paste into the fabric.
The conveyer belt is cleared once during each revolution by the washing device.
Advantages of Rotary Screen Printing:
Up to 24 colors in a pattern can be produced.
Suitable for both woven and knitted fabric.
Stripe design can be done in warp.
Disadvantages of Rotary Screen Printing:
Cost is high due to high price of screen.
Not suitable for short runs.
Not possible of fine line design.
Transfer printing is the term used to describe textile and related printing processes in which the design is first printed on to a flexible non-textile substrate and later transferred by a separate process to a textile.
Basic Principle: Transfer printing technology is done by two steps-
• At first step, the definite design is printed on transfer paper by sublimable dyestuff paste.
• In 2nd step, transfer paper is kept contact into the fabric to be printed. As a result design of printing paste is transferred to the fabric from transfer paper under the condition of time, temp and pressure.
• In this method cut piece fabric is printed in flat bed M/C and long fabric is printed by continuous transfer printing M/C.
Types of transfer printing M/C:
01. Flatbed Process Transfer Printing M/C:
This machine is suitable to print the garments. Both side printing of fabric is possible. Number of printed garments per hr. is 50-100. Heating is carried out by electricity or steam.
A = Feeding,
B = Printing,
C = Press,
D = Stacking of printing parts,
E = Conveyor
• At first fabric is fed to endless blanket.
• Fabric comes to the contact of pre-printed paper on press bed at temperature 1800-2200C & 30-40s pressing is given by a pair of cylinder with air.
• The heated plate of press bed is then lifted and printed fabric is stored by moving through blanket. Then another cycle is starts.
02. Continuous Transfer Printing M/C:
In this M/C, design is transferred from printing paper to fabric. After printing by this M/C no need of fixation or wet treatment.
• In this M/C, the cylinder is heated at 2200C. Design is transferred due to the pressure of cylinder & pre-printed paper.
• A tension device is used for pressure of printing paper to fabric.
• Backing paper is used for uniform pressure fabric & transfer paper.
• The speed of m/c varies between 6-15 m/min depending on the diameter of cylinder.
03. Vacuum Transfer Printing:
Both continuous and unit transfer printing machine have been redesigned to provide vacuum assisted transfer.
• Vacuum is produced in a perforated cylinder.
• The composite of fabric & paper is fed around the perforated cylinder.
• Due to vacuum, the paper & fabric are wrapped around the cylinder, ensuring an intimate contact pressure.
• The steel cylinder is covered with a heat resistant padding material.
• Heating is done by infra-red heating, filled in a special reflecting chamber.
Methods of transfer printing:
Sublimation transfer: This method depends on the use of a volatile dye in the printed design. When the paper is heated the dye is preferentially adsorbed from the vapor phase by the textile material with which the heated paper is held in contact. This is commercially the most important of the transfer-printing methods.
Melt transfer: This method has been used since the 19th century to transfer embroidery designs to fabric. The design is printed on paper using a waxy ink, and a hot iron applied to its reverse face presses the paper against the fabric. The ink melts on to the fabric in contact with it. This was the basis of the first commercially successful transfer process, known as Star printing.
Film release: This method is similar to melt transfer with the difference that the design is held in an ink layer which is transferred completely to the textile from a release paper using heat and pressure. Adhesion forces are developed between the film and the textile which are stronger than those between the film and the paper.
Wet transfer: Water-soluble dyes are used to produce a design on paper. The design is transferred to a moistened textile using carefully regulated contact pressure. The dye transfers through aqueous medium. The method is not used to any significant extent at the present time.
Advantages of Transfer Printing:
Standard printing can be done by this printing.
No need of after treatment or washing.
Produced fabric is not stiff.
The degree of wastage is very small.
Suitable in knitted fabric.
The cost of the equipment is comparatively low.
Disadvantages of Transfer Printing:
Only volatile dye can be used.
There is extra step of 1st working on paper.
Once the transfer printing paper has been used it cannot be used.