Reactive Group
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- Words: 887
- Pages: 12
Group members: Rashed Ahmed -042061041 Md. Shafiur Rahman -042097041 Md.Azad ur Rahman -042073041 Md.Shahadat Hossain -042059041 Sohel Rana -041039041 Mohammad Ali -041062041
PRESENTATION ON ROTARY SCREEN PRINTING
Introduction Preparation of Rotary Screens, Cost analysis of Rotary
Screens.
Rotary Screen Printing Rotary screen printing is so named because it uses a cylindrical screen
that rotates in a fixed position rather than a flat screen that is raised and lowered over the same print location.
The origin of rotary screen printing may be traced to Almarindo
Barros Lisbon, Portugal, who had been experimenting(1956) with a rotary screen of phosphor bronze mesh made, first as a flat screen and then soldered at the repeat joint to form a rotary screen Rotary presses place the squeegee within the screen. These machines are designed for roll-to-roll (web) printing on flexible materials ranging from narrow web films to wide-format roll textiles.
Rotary Screens Rotary screens are classified by their mesh size which is the
number of holes per linear inch, measured in certain angle on the screen. This classification has no relation to some important properties of a screen, which greatly influences the final printing quality. These properties include, 1. Thickness of the screen. 2. Evenness of the thickness over the full width of the screen. 3. Dimension of the wall between two holes. 4. Shape of the perforation hole through the screen. 5. Openness of the screen.
Preparation of Rotary Screens Nickel is found to be suitable as a material of construction since it is resistant to mechanical wear a as chemical attack. In addition, it is flexible.
Methods for preparation of Rotary screen : There are two methods of making the Rotary
screens-
1. 2.
Emulsion Lacquering. Galvano Pasty.
Emulsion Lacquering: Lacquering screens have fineness of 60, 80,or 100 mesh per inch (24,32or 40 dots per cm). The openings are approximately conical or funnel-shaped and have a smaller diameter on the inside of the screen cylinder then on the outside .The patterns are transferred by the photochemical method, with a photosensitive and hardening screen lacquer or according to the method preliminary lacquering.
Flow Chart of Emulsion Lacquering Screen Preparation The process may be described as follows: Degreasing ↓ Suctioning ↓ Stiffening by auxiliary rings ↓ Air drying ↓ Coating with sensitized hardening screen lacquer ↓ Dyeing at 18° c to 20°c and 60% RH ↓ Coating and dyeing (Repeated thrice) ↓ Exposure to light ↓ Developing (washing at 10°c to 25°c for 15 to 30 min) ↓ Drying at 65°C ↓ Application of hardener solution and suctioning off ↓ Retouching (if necessary) ↓ Preliminary hardening at 65°C for 3 hours ↓ Subsequent hardening (at 140°C for 1 hour) ↓ Retouching (if necessary) ↓ Gluing of end rings
PROCESS OF EMULSION LACQUER
SCREENS PREPARATION 3.CLEANING, DEGREASING: First, remove any grease or other residue from the surface
of the rotary screen. For removing the grease, a solution is treated with screen. Solution: Chromic acid – 33% Sulfuric Acid – 7-10% Ammonium dichromate – 7-10% Then the screen is washed with water for 60-90 seconds. The screen is put down for a few minutes and suctiontreated while still wet. This removes any residue of the cleaning solutions from the rinsing water.
1.
COATING:
Photosensitive solution is applied and dried for 5-10 minutes in a drying box in air (28 degree Celsius). The solution contains Autosol and Sensitiliser. The drying box should have a fine air filter in the intake duct. The quality and thickness of the emulsion coating are determined by the squeegee speed, viscosity of the solution, squeegee dia. Squeegees angle, squeegee holder size, and mesh. The drying should be carried out as soon as possible. Normally, the coated screens may be stored for 7-10 hours before exposure.
1.
EXPOSURE:
In the case of heat radiation, the source should be cooled and the screen may be cooled. The temp. of the screen and the negative should not exceed 28 degree Celsius during the exposure. With a xenon lamp, the exposure time is 7 min. at a distance of 150 mm from the screen. With a high-pressure mercury lamp, it is 14 min. at a distance of 180 mm. After exposure, the developing is carried out immediately by immersing the screen horizontally in water for 30-40 degree Celsius. After rinsing, the screen is dried (at 30 degree Celsius in 10-30 min.) and cured at 140 degree Celsius for 1 hour to harden the lacquer.
Cost analysis of Rotary & Flat bed screen printing
Percentage of cost(%)
Rotary Flat bed
60 50 40 30 20 10 0
51.7 49.7 41.6
35.2
6.5 Depriciation & interest
9.1 2.2 Overhead & Labour
4 Printing paste(colour)
Items
Screen
We have seen that the cost of Rotary screen is higher. But screen cost can be reduced by emulsion lacquer method : For example: It is possible to reuse the screens three times . 60% of the 1st time used screens can be re-used for the 2nd time . 60% of the 2nd time used screens can also be re-used for the 3rd time. Process
Screens
1st time
100
2nd time
60 (out of 100)
3rd time
36 (out of 60)
PRESENTATION ON ROTARY SCREEN PRINTING
Introduction Preparation of Rotary Screens, Cost analysis of Rotary
Screens.
Rotary Screen Printing Rotary screen printing is so named because it uses a cylindrical screen
that rotates in a fixed position rather than a flat screen that is raised and lowered over the same print location.
The origin of rotary screen printing may be traced to Almarindo
Barros Lisbon, Portugal, who had been experimenting(1956) with a rotary screen of phosphor bronze mesh made, first as a flat screen and then soldered at the repeat joint to form a rotary screen Rotary presses place the squeegee within the screen. These machines are designed for roll-to-roll (web) printing on flexible materials ranging from narrow web films to wide-format roll textiles.
Rotary Screens Rotary screens are classified by their mesh size which is the
number of holes per linear inch, measured in certain angle on the screen. This classification has no relation to some important properties of a screen, which greatly influences the final printing quality. These properties include, 1. Thickness of the screen. 2. Evenness of the thickness over the full width of the screen. 3. Dimension of the wall between two holes. 4. Shape of the perforation hole through the screen. 5. Openness of the screen.
Preparation of Rotary Screens Nickel is found to be suitable as a material of construction since it is resistant to mechanical wear a as chemical attack. In addition, it is flexible.
Methods for preparation of Rotary screen : There are two methods of making the Rotary
screens-
1. 2.
Emulsion Lacquering. Galvano Pasty.
Emulsion Lacquering: Lacquering screens have fineness of 60, 80,or 100 mesh per inch (24,32or 40 dots per cm). The openings are approximately conical or funnel-shaped and have a smaller diameter on the inside of the screen cylinder then on the outside .The patterns are transferred by the photochemical method, with a photosensitive and hardening screen lacquer or according to the method preliminary lacquering.
Flow Chart of Emulsion Lacquering Screen Preparation The process may be described as follows: Degreasing ↓ Suctioning ↓ Stiffening by auxiliary rings ↓ Air drying ↓ Coating with sensitized hardening screen lacquer ↓ Dyeing at 18° c to 20°c and 60% RH ↓ Coating and dyeing (Repeated thrice) ↓ Exposure to light ↓ Developing (washing at 10°c to 25°c for 15 to 30 min) ↓ Drying at 65°C ↓ Application of hardener solution and suctioning off ↓ Retouching (if necessary) ↓ Preliminary hardening at 65°C for 3 hours ↓ Subsequent hardening (at 140°C for 1 hour) ↓ Retouching (if necessary) ↓ Gluing of end rings
PROCESS OF EMULSION LACQUER
SCREENS PREPARATION 3.CLEANING, DEGREASING: First, remove any grease or other residue from the surface
of the rotary screen. For removing the grease, a solution is treated with screen. Solution: Chromic acid – 33% Sulfuric Acid – 7-10% Ammonium dichromate – 7-10% Then the screen is washed with water for 60-90 seconds. The screen is put down for a few minutes and suctiontreated while still wet. This removes any residue of the cleaning solutions from the rinsing water.
1.
COATING:
Photosensitive solution is applied and dried for 5-10 minutes in a drying box in air (28 degree Celsius). The solution contains Autosol and Sensitiliser. The drying box should have a fine air filter in the intake duct. The quality and thickness of the emulsion coating are determined by the squeegee speed, viscosity of the solution, squeegee dia. Squeegees angle, squeegee holder size, and mesh. The drying should be carried out as soon as possible. Normally, the coated screens may be stored for 7-10 hours before exposure.
1.
EXPOSURE:
In the case of heat radiation, the source should be cooled and the screen may be cooled. The temp. of the screen and the negative should not exceed 28 degree Celsius during the exposure. With a xenon lamp, the exposure time is 7 min. at a distance of 150 mm from the screen. With a high-pressure mercury lamp, it is 14 min. at a distance of 180 mm. After exposure, the developing is carried out immediately by immersing the screen horizontally in water for 30-40 degree Celsius. After rinsing, the screen is dried (at 30 degree Celsius in 10-30 min.) and cured at 140 degree Celsius for 1 hour to harden the lacquer.
Cost analysis of Rotary & Flat bed screen printing
Percentage of cost(%)
Rotary Flat bed
60 50 40 30 20 10 0
51.7 49.7 41.6
35.2
6.5 Depriciation & interest
9.1 2.2 Overhead & Labour
4 Printing paste(colour)
Items
Screen
We have seen that the cost of Rotary screen is higher. But screen cost can be reduced by emulsion lacquer method : For example: It is possible to reuse the screens three times . 60% of the 1st time used screens can be re-used for the 2nd time . 60% of the 2nd time used screens can also be re-used for the 3rd time. Process
Screens
1st time
100
2nd time
60 (out of 100)
3rd time
36 (out of 60)
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