The pursuit of high quality screen printing, as screen printing workers, should first have the right quality concept. Second, we should have the correct quality concept. Second, there should be good work habits. For example, the work environment is of good quality and clean, and all appliance tips are well maintained. If there is no vacuum cleaner, do not use a brush when cleaning the work environment to avoid flying dust. Cleaning of the floor, cleaning of tables and utensils requires the use of a damp cloth. Clean working conditions can improve the quality of work, improve the working environment, and help achieve high-quality printing.
Negatives Before we start printing, we need positive negatives. What are the requirements for a good negative?
* Base film and polyester film should be highly transparent.
* The film surface should be below the film. We often find that some users use the film side is the negative side of the film, used for offset printing positive film, the use of this negative film printing quality will not be guaranteed. Because the screen printing screen printing plate requires the image of the film surface should be close contact with the plate of the photosensitive layer quality.
* Density (density = darkness) needs to be greater than D3. Offset printing uses less than D3 positive film to help measure the density of the positive film with a densitometer.
* The density of images and texts on the negatives needs higher values. Hand carved masks should not be used as screen printing plates. The film should be made of a high hardness photographic film.
* Before using a negative plate, clean it with a detergent or dust roller.
Wire Mesh Screen printing is not a flexible fabric but a high-strength material with very tight tolerances. For example, we may all know that in the silk wind of 120 mesh/cm, there are 24,000 meters of silk per square meter, or 14400 holes per square centimeter, but in fact there is much more to knowledge about silk screens.
SEFAR PET1000 mesh has:
1, high tension 2, low tension loss 3, high tension stability 4, good etching performance while the screen weaving structure is also very important for screen printing, you can find in the technical information The required technical specifications. What is the benefit of knowing all these data? Let us look at the relevant data:
1. Wire diameter: It is an index that determines the final imaging capability.
2. Web/CM: The strength and possible tension of the screen can be determined because the effective cross-section and wire diameter per cm of screen determines the relative stability of the screen. Both of these factors also determine all other parameters. Such as the thickness of the screen, the size of the opening of the screen, the open area ratio of the screen.
3. The thickness of the screen and the area of ​​the weapon determine the underside of ink and the theoretical volume of ink penetration.
Frame We all know very well that only a solid frame can control the entire printing process. For example, the magnitude of tension loss and the degree of tension stability.
Stretching is as explained before. According to the average effective cross-section of the screen, each different screen has its maximum tension. Only use a well-maintained stretching machine to reach this maximum tension. Sometimes it is regrettable that some stretching machines are covered with a layer of dry adhesive mesh. The rubber pads are harder than stones and cannot be closed horizontally. Obviously, it is impossible for a device like this to draw a good screen, and there is a danger of damaging the screen. Therefore, we should scrape off the residual glue on the fixture and stick it with peelable tape to protect it. It is recommended to check every time. It is possible to draw a line on the screen with a copper pen in front of all fixtures that grip the wire mesh. After a moderate tension stretch, if this line is still parallel to the fixture, everything is normal. If not, the fixture needs to be carried out. Adjustment, overhaul.
The stretch net can be stretched according to the tension required by its own production, but it should not exceed the technical parameters promoted by the wire mesh manufacturer. At the same time, it should be noted that the screens in the four corners of the stretching machine need to be in the form of a middle bag to avoid pulling too much tension and breaking the screen. The size of the pocket should be based on the size of the stretched frame and the required tension. At the same time, the gaps between the clamps in the four corners need to remain at least with the width of the cross-section of the frame material, so that the wire mesh is stretched to the specified tension without breaking the net.
On each stretched screen plate, the following data should be written on the edge of the frame: number of meshes, wire diameter, initial tension, screen number, stretch date, and the name of the person in charge. Stretch the screen for at least 24 hours before using it, so that we can get a stable, qualified screen.
Conditions required for the best screen 1. The quality tool is clean and ready for use. The plate room should be free of dust.
2. Check the screen tension. All multicolored overlays need the same tension.
3. Fully degreasing: Use a brush and a water source with a certain pressure for cleaning.
4. Dry at a temperature below 40°C.
5. According to the method suggested by the manufacturer, the sensation glue should be prepared 12 hours in advance.
6. Use a clean, slightly rounded edge sizing machine for gluing. The gluing area is at least 10% smaller than the inner diameter of the frame.
7. When gluing, start with the printing surface first. The number of times of gluing depends on the solid content of the emulsion, the viscosity, the screen, and the desired screen thickness.
8. When drying the screen, the printed surface should be placed face down (avoiding the flow of photosensitive glue back to the ink surface).
9. For screen printing with fine lines and halftone printing, apply one or more photoresists on the printed surface after each drying until the photosensitive layer on the printing surface is flat.
10. The durability of the glass cleaner vacuum cleaner. Check the film is correct? Does the film surface fit on the screen? Does blackness meet the requirements and is it placed correctly? And make the exposure machine has enough time to reassure.
11. Set the correct exposure time and keep a record. Every three months or when the exposure decreases, the exposure time should be tested and adjusted to correct.
12. Keep the exposed screen away from the light source (daylight, incandescent light).
13. Use water with proper pressure for development and development during development. In particular, the ink surface should be fully cleaned and cannot be washed until the surface is not slippery. After the underexposure film is washed, the film will be peeled off.
14. Use a soft, clean paper, a clean cloth or a vacuum cleaner to remove excess moisture.
15. Use a suitable make-up material to repair the screen.
16. Write all parameters to the mesh: thickness, exposure time, date, name.
Reasons for Printing Accuracy Deviation 1. When making multi-color overprint (halftone printing) screens, the screens are dried at different temperatures, causing errors in the printing accuracy.
2. The screen has low tension or overprint (halftone) screen tension.
3. Use a hair dryer to dry the screen dry unevenly.
4. The use of too old, unsturdy, and distorted mesh-plate making results in deviation of the printed image due to poor stability of the frame (these problems can be detected with the film)
5. When using multi-color overlay, the used net distance is inconsistent.
6. Squeegee deformation.
7. Caused by some influence on the size of substrates introduced to change the production of moiré • Mismatches in the number of meshes of halftone printing screens and screens (the number of screen meshes should be 2.5, 3.75 or 6.25 times that of the screen).
• The halftone printing screen and the screen line have an incorrect angle.
The RZ value is too high (should be less than 8).
· The template is too thick or too thin.
· Compared with the wire diameter, too small dots will be lost (net coverage should be 5-95%).
Causes of Color Change 1. The ink consistency changes (different viscosities) due to evaporation of the solvent.
2. Change the squeegee angle during printing.
3. Change the scratch hardness in the printing process.
4. Change the speed during printing.
5. The adhesive edge is damaged.
Causes the template to lose the ring prematurely. 1. Insufficient rubber grease.
2. Insufficient drying before exposure.
3. The exposure time is insufficient.
4. The net distance is too high.
5. The ink blade is too sharp and the pressure is too great.
6. Use a cleaning solvent for cleaning (including a small amount of water).
Tensiometers For screen printers, tensiometers are foods that measure and monitor the screen level during the stretching stage or when re-used, measured in newtons per centimeter and simplified to N/CM.
Note: 1 Newton is the force measured by accelerating the 1 kilogram of material to an area of ​​one square meter.
Thickness Gauge This instrument score applies to the following areas:
Printed circuit board (PCB);
Glass ornament
Ceramic ornament
Ceramic applique.
The print quality will depend on the control loop of each factory condition during actual printing. Thickness gauges are increasingly being used by all screen printing manufacturers certified by quality certification bodies.
Surface Roughness Measuring Instrument This instrument has been used for many years in the engineering field and the screen printing industry was in the late 80's. The tester can show the flatness of the stencil surface. The sign of the surface roughness value is RZ, and an RZ value of 0 indicates that the template is very smooth.
Surface Humidity Meters For best results, the stencils must be fully dried before exposure. If not completely overjoyed, the moisture contained in the emulsion will cause my agent to be insufficiently sensitive, resulting in underexposure of the template, and even worse, there will be a phenomenon of release. The dryness of the screen is not easy to judge. The contact humidity meter is an ideal test instrument. It can eliminate people's concerns about the moisture content of the plate to be exposed.
In the stencil exposure process, the ray detector needs to control two important parameters: the energy of the UV light and the distribution of light in the stencil area. Although most high-quality exposure machines are now equipped with an optical integrator as a compensation for the UV output of the wave, it is not easy to measure the value of the incident light and the state of the UV light radiation density.
When the center of the exposure frame and the density of the light in the farthest corner are at the same level, the desired distance is achieved.
When using this measurement, wear UV-proof glasses and do not prolong unnecessary exposure. (Ackerman) (From "China Packaging Newspaper and Print Weekly")
Negatives Before we start printing, we need positive negatives. What are the requirements for a good negative?
* Base film and polyester film should be highly transparent.
* The film surface should be below the film. We often find that some users use the film side is the negative side of the film, used for offset printing positive film, the use of this negative film printing quality will not be guaranteed. Because the screen printing screen printing plate requires the image of the film surface should be close contact with the plate of the photosensitive layer quality.
* Density (density = darkness) needs to be greater than D3. Offset printing uses less than D3 positive film to help measure the density of the positive film with a densitometer.
* The density of images and texts on the negatives needs higher values. Hand carved masks should not be used as screen printing plates. The film should be made of a high hardness photographic film.
* Before using a negative plate, clean it with a detergent or dust roller.
Wire Mesh Screen printing is not a flexible fabric but a high-strength material with very tight tolerances. For example, we may all know that in the silk wind of 120 mesh/cm, there are 24,000 meters of silk per square meter, or 14400 holes per square centimeter, but in fact there is much more to knowledge about silk screens.
SEFAR PET1000 mesh has:
1, high tension 2, low tension loss 3, high tension stability 4, good etching performance while the screen weaving structure is also very important for screen printing, you can find in the technical information The required technical specifications. What is the benefit of knowing all these data? Let us look at the relevant data:
1. Wire diameter: It is an index that determines the final imaging capability.
2. Web/CM: The strength and possible tension of the screen can be determined because the effective cross-section and wire diameter per cm of screen determines the relative stability of the screen. Both of these factors also determine all other parameters. Such as the thickness of the screen, the size of the opening of the screen, the open area ratio of the screen.
3. The thickness of the screen and the area of ​​the weapon determine the underside of ink and the theoretical volume of ink penetration.
Frame We all know very well that only a solid frame can control the entire printing process. For example, the magnitude of tension loss and the degree of tension stability.
Stretching is as explained before. According to the average effective cross-section of the screen, each different screen has its maximum tension. Only use a well-maintained stretching machine to reach this maximum tension. Sometimes it is regrettable that some stretching machines are covered with a layer of dry adhesive mesh. The rubber pads are harder than stones and cannot be closed horizontally. Obviously, it is impossible for a device like this to draw a good screen, and there is a danger of damaging the screen. Therefore, we should scrape off the residual glue on the fixture and stick it with peelable tape to protect it. It is recommended to check every time. It is possible to draw a line on the screen with a copper pen in front of all fixtures that grip the wire mesh. After a moderate tension stretch, if this line is still parallel to the fixture, everything is normal. If not, the fixture needs to be carried out. Adjustment, overhaul.
The stretch net can be stretched according to the tension required by its own production, but it should not exceed the technical parameters promoted by the wire mesh manufacturer. At the same time, it should be noted that the screens in the four corners of the stretching machine need to be in the form of a middle bag to avoid pulling too much tension and breaking the screen. The size of the pocket should be based on the size of the stretched frame and the required tension. At the same time, the gaps between the clamps in the four corners need to remain at least with the width of the cross-section of the frame material, so that the wire mesh is stretched to the specified tension without breaking the net.
On each stretched screen plate, the following data should be written on the edge of the frame: number of meshes, wire diameter, initial tension, screen number, stretch date, and the name of the person in charge. Stretch the screen for at least 24 hours before using it, so that we can get a stable, qualified screen.
Conditions required for the best screen 1. The quality tool is clean and ready for use. The plate room should be free of dust.
2. Check the screen tension. All multicolored overlays need the same tension.
3. Fully degreasing: Use a brush and a water source with a certain pressure for cleaning.
4. Dry at a temperature below 40°C.
5. According to the method suggested by the manufacturer, the sensation glue should be prepared 12 hours in advance.
6. Use a clean, slightly rounded edge sizing machine for gluing. The gluing area is at least 10% smaller than the inner diameter of the frame.
7. When gluing, start with the printing surface first. The number of times of gluing depends on the solid content of the emulsion, the viscosity, the screen, and the desired screen thickness.
8. When drying the screen, the printed surface should be placed face down (avoiding the flow of photosensitive glue back to the ink surface).
9. For screen printing with fine lines and halftone printing, apply one or more photoresists on the printed surface after each drying until the photosensitive layer on the printing surface is flat.
10. The durability of the glass cleaner vacuum cleaner. Check the film is correct? Does the film surface fit on the screen? Does blackness meet the requirements and is it placed correctly? And make the exposure machine has enough time to reassure.
11. Set the correct exposure time and keep a record. Every three months or when the exposure decreases, the exposure time should be tested and adjusted to correct.
12. Keep the exposed screen away from the light source (daylight, incandescent light).
13. Use water with proper pressure for development and development during development. In particular, the ink surface should be fully cleaned and cannot be washed until the surface is not slippery. After the underexposure film is washed, the film will be peeled off.
14. Use a soft, clean paper, a clean cloth or a vacuum cleaner to remove excess moisture.
15. Use a suitable make-up material to repair the screen.
16. Write all parameters to the mesh: thickness, exposure time, date, name.
Reasons for Printing Accuracy Deviation 1. When making multi-color overprint (halftone printing) screens, the screens are dried at different temperatures, causing errors in the printing accuracy.
2. The screen has low tension or overprint (halftone) screen tension.
3. Use a hair dryer to dry the screen dry unevenly.
4. The use of too old, unsturdy, and distorted mesh-plate making results in deviation of the printed image due to poor stability of the frame (these problems can be detected with the film)
5. When using multi-color overlay, the used net distance is inconsistent.
6. Squeegee deformation.
7. Caused by some influence on the size of substrates introduced to change the production of moiré • Mismatches in the number of meshes of halftone printing screens and screens (the number of screen meshes should be 2.5, 3.75 or 6.25 times that of the screen).
• The halftone printing screen and the screen line have an incorrect angle.
The RZ value is too high (should be less than 8).
· The template is too thick or too thin.
· Compared with the wire diameter, too small dots will be lost (net coverage should be 5-95%).
Causes of Color Change 1. The ink consistency changes (different viscosities) due to evaporation of the solvent.
2. Change the squeegee angle during printing.
3. Change the scratch hardness in the printing process.
4. Change the speed during printing.
5. The adhesive edge is damaged.
Causes the template to lose the ring prematurely. 1. Insufficient rubber grease.
2. Insufficient drying before exposure.
3. The exposure time is insufficient.
4. The net distance is too high.
5. The ink blade is too sharp and the pressure is too great.
6. Use a cleaning solvent for cleaning (including a small amount of water).
Tensiometers For screen printers, tensiometers are foods that measure and monitor the screen level during the stretching stage or when re-used, measured in newtons per centimeter and simplified to N/CM.
Note: 1 Newton is the force measured by accelerating the 1 kilogram of material to an area of ​​one square meter.
Thickness Gauge This instrument score applies to the following areas:
Printed circuit board (PCB);
Glass ornament
Ceramic ornament
Ceramic applique.
The print quality will depend on the control loop of each factory condition during actual printing. Thickness gauges are increasingly being used by all screen printing manufacturers certified by quality certification bodies.
Surface Roughness Measuring Instrument This instrument has been used for many years in the engineering field and the screen printing industry was in the late 80's. The tester can show the flatness of the stencil surface. The sign of the surface roughness value is RZ, and an RZ value of 0 indicates that the template is very smooth.
Surface Humidity Meters For best results, the stencils must be fully dried before exposure. If not completely overjoyed, the moisture contained in the emulsion will cause my agent to be insufficiently sensitive, resulting in underexposure of the template, and even worse, there will be a phenomenon of release. The dryness of the screen is not easy to judge. The contact humidity meter is an ideal test instrument. It can eliminate people's concerns about the moisture content of the plate to be exposed.
In the stencil exposure process, the ray detector needs to control two important parameters: the energy of the UV light and the distribution of light in the stencil area. Although most high-quality exposure machines are now equipped with an optical integrator as a compensation for the UV output of the wave, it is not easy to measure the value of the incident light and the state of the UV light radiation density.
When the center of the exposure frame and the density of the light in the farthest corner are at the same level, the desired distance is achieved.
When using this measurement, wear UV-proof glasses and do not prolong unnecessary exposure. (Ackerman) (From "China Packaging Newspaper and Print Weekly")
The samples confirmed by both parties shall prevail; the buyer shall be responsible for the verification of all pictures, texts, and samples and confirmed by both parties, and the seller shall take this as the production standard. If the buyer still needs to modify the product in part or in whole, it should notify in advance; if the loss caused by the modification is borne by the buyer, including the responsibility for the time delay caused by the modification. If the seller does not produce according to the standards of pictures, texts, materials and samples provided by the buyer, the buyer may request the seller to re-produce.
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