CURING PROCESS Curing Chamber

In case of pigment printing the printed fabric has been raised to an adequate temperature for giving the binder enough energy to form a continuous film. This binds the pigment particles and achieves satisfactory adhesion to the fibre surface. At the same time, cross linking of binder molecules is achieved if suitable monomers or agents have been used, and the required pH and the temperature achieved. The equipment for this purpose is the roller baker “curing oven”. It has an arrangement for carrying woven fabrics through hot air, with as many fabric transport rollers as are required to provide sufficient exposure time and fabric speed desired. Treatment time varies from 5 to 8 minutes and the temperature of the treatment ranges from 140 to 160 C.

Loop Ager

Loop ager is continuous process equipment in which the cloth is handled in loop form with least contact and transported in tensionless manner. It is a versatile machine by which hot air curing, saturated steaming water injection along with steam is involved.

Before starting, the inner parts are cleaned and made free of water. The air inside can be expelled by slow injection and closing the manhole door. According to process temperature, heating value lines are kept open and temperature is set. The speed of machine is set as per process time and loop length. Pieces of printed fabric (single or double web) are stitched to the leader fabric and fed into the chamber.

After the process the cloth is drawn out form chamber and is carried to plaiter through top guide rolls.

Advantages

• Continuous process leading to consistency in fixation.

• Higher productivity and facility of process double webs.

• Better temperature control and less scope for variations.

Disadvantages

• Not economical for short runs.

• Consumes time and energy for heating and cooling.

• Risk of loop rods struck up falling and damage to fabric.

MACHINERY

Flat- Screen Printing

Flat- screen and

rotary-screen printing are both

characterized by the

transferred to the fabric through openings in specially designed screens. The openings on each screen correspond to a pattern and when the printing paste is forced through by means of a squeegee, the desired pattern is reproduced on the fabric. A separate screen is made for each colour in the pattern.

Screen printing with automatic squeegee system

Flat-screen printing machines can be

 Manual

 Semi-automatic

 Completely automatic.

One type of machine, which is still commonly found in printing houses, can be described as follows.

• The fabric is first glued to a moving endless belt.

• A stationary screen at the front of the machine is lowered onto the area that has to be printed and the printing paste is wiped with a squeegee.

• Afterwards the belt, with the fabric glued on it, is advanced to the pattern-repeat point and the screen is lowered again.

• The printed fabric moves forward step by step and passes through a dryer.

The machine prints only one colour at a time.

• When the first colour is printed on the whole length of the fabric, the dried fabric is ready for the second cycle and so on until the pattern is completed.

flat-screen printing machine

In other fully mechanized machines all the colours are printed at the same time. A number of stationary screens (from 8 to 12, but some machines are equipped with up to 24 different screens) are placed along the printing machine. The screens are simultaneously lifted, while the textile, which is glued to a moving endless rubber belt, is advanced to the pattern-repeat point. Then the screens are lowered again and the paste is squeezed through the screens onto the fabric. The printed material moves forward one frame at each application and as it leaves the last frame it is finally dried and it is ready for fixation.

Mechanized screen printing machine with stationary screens mounted in a frame In both machines the continuous rubber belt, after pulling away the fabric, is moved downward in continuous mode over a guide roller and washed with water and rotating brushes to remove the printing paste residues and the glue, if necessary. After this, the belt is sent back to the gluing device.

In some cases the glue is applied in liquid form by a squeegee, while in other machines the belts are pre-coated with thermoplastic glues. In this case the textile is heated and then it is squeezed by a roller or simply pressed against the rubber-coated belt, causing the glue to soften and instantly adhere.

After printing, the screens and the application system are washed out. It is common practice to squeeze the color from the screens back into the printing paste mixing containers before washing them. Specially developed Screen printing machine for Flat printing application

Features

These flat screen printing machines are extensively used for printing on flat surfaces like PVC, Metal, Glass, Paper, Board and PCB. These are highly cost effective as these require less power. The salient features are as below:

• Pneumatically drive.

• Low noise

• Printing table with X, Y and Rotation for accurate registration.

• Printing table with powerful Vacuum to hold the substrate on to its position while printing.

• Maximum Substrate height 40 mm.

• Squeegee /coater pressure with fine adjustment.

• Angle can be set as per requirement.