Screen quality is the premise of printing quality. Without good quality screens, it is impossible to print high quality works. In the process of screen making, selection of webs, stretching nets, cleaning to sizing, exposure, and development are important. However, the screen shape is also one of the factors affecting the print quality. This article discusses the problem of screen plane shape selection before plate making.
The screen shape is also the plane shape of the frame. The version selection box is generally based on the net content of the manuscript plus the width of the ink zone to determine the size of the frame, and then consider what material and how much material the frame will use. The shape of the frame is mostly rectangular, and only select rare shapes when encountering special substrates.
For example: the handkerchief printing uses square; the printed advertisement on the finished umbrella is affected by the ribs; it adopts triangular or isosceles trapezoid; large-scale color printing is used to strengthen the carrying capacity of the frame and prevent the inward deformation from being selected as hexagon; the concave bottom, The pelvic floor is rounded. In fact, the special screen shape is not only suitable for special printing, but also in the aspects of tension force, tension uniformity, screen printing resolution, and ink volume, especially when producing fine lines and high-mesh screens. Face, but also practical for ordinary planes. The following are elaborated from the following three aspects: force analysis, screen printing experiment, and practical application.
First, the screen plane force analysis screen printing plate is a kind of elastic version, stretching and squeegee both cause the screen to be deformed and require the screen to restore the original state, the frame withstands the restoring force of the screen. This restoring force can be regarded as the sum of the stretching tension and the squeegee force and the shear force generated by the stencil friction during operation of the squeegee. Since the movement force is an instantaneous value, the squeegee force can be manually controlled and the frame can be subjected to force. Can be seen as close to the tension under static conditions. From the viewpoint of 90° stretch net, the higher the tension of the stretch net, the tighter the screen, the more uniform the tension, and the better the quality of the screen. However, the tension of the stretch net will not be transferred to the screen by 100%. The main loss of the tension loss is in the deformation of the frame and the fatigue of the screen. In response to this contradiction, the high-strength wire mesh and the trapezoidal cross-section net frame have come into being. Screen quality. However, if you increase the material of the frame indefinitely, it will increase the weight and affect the actual operation. The deformation of the frame is proportional to its length. The longer the frame is, the larger the deformation is, and the greater the tension loss is. Therefore, the shape of the frame of the frame varies from frame to frame.
On the circular net frame, each point of action is subjected to a screen restoring force in both vertical and horizontal directions, and the resultant force of the restoring force is directed toward the center of the circle to reach equilibrium, and thus no inward deformation occurs. The joints on the hexagonal frame are subjected to the same force, and the six sides are relatively short and are subjected to vertical forces to minimize deformation. The length of the square net frame is equal, which is the smallest deformation in the rectangular net frame, and the best tension evenness after deformation. The smaller the ratio of the short side to the long side of the rectangular net frame is, the larger the deformation is, and the greatest influence on the uniformity of the whole screen plate tension is.
Second, screen printing experiment steps:
1. Use a 2cm x 2cm metal square tube to bend into a 40cm diameter semicircular box on a round bender and then weld together. The same material is again made of hexagonal, square and rectangular mesh frames.
2. Grind the mesh frame and grind it, stick the net glue twice, select a 300 mesh screen to stretch the net on the same stretcher, the tension is about 8kg. The screen plate is left to stand for 3 to 4 days after being stretched.
3. The empty version scraped four pieces of the ground.
4. Use the 60 lines of 1-9 meshes to adjust the picture of the sun. Make the same version of the plate on each of the four types of screen frames. Use each plate to print the two clearest tone charts on the 3mm white glass. Comparing samples printed on screens of various shapes.
Experimental results: The rectangular screen has a slightly poorer uniformity of the ink and the uniformity of the dots. The dots are distorted and incomplete. The quality of Other screen samples is nearly the same.
Third, the actual use of the shape of the screen, round, hexagonal frame stretched tight, even tension, printing effect is good, but in practical applications, the circular mesh frame production using curved machine bending, the process is complex, The printing area is inscribed rectangle and the material is wasted. Although the hexagonal frame is welded with straight edges, it has many welding spots and the angle is difficult to control. There are also problems with the round frame and lack of practicality. Only the square version has the advantages of the above layout, and the processing technology is the same as that of the rectangular version. Therefore, it is better to select a square with a side length of 1:1 when making a net frame or to select a rectangle with a ratio of side length close to 1:1 as much as possible.
When I was just engaged in screen printing, I used 13 large, medium and small screens in different shapes to produce batches of large-scale maps. In order to be faithful to the manuscript and meet the mathematics accuracy of the map, the criss-crossing square-finish net with no jagged edges and the contours as dense as the hairline are printed on the screen, clearly reflecting the rivers, beaches, roads, and residential areas. Heap, all night long.
Turn over the print records in less and more losses, and count the success rate of each numbered screen. The highest success rate and best quality were found in the square prints. After analysis and testing, the layout was changed to 80cm×80cm, 90cm×90cm, and 100cm×120cm. Three groups of 12 screen printing plates were used for recycling. When typography, as many pieces of content as possible together, or a content lined up several times to form a layout, overprinting can not be spliced ​​pattern using a large version of the system, as long as the success is worth it.
Due to the change in the shape of the screen, there were as many as 80 screen printing jobs in the last month, and 3,000 sheets of paper were opened. The success rate was 100%. The screen printing accuracy has a positive error of 2%, and the negative error is zero. The contents of the map are clear, the lines are smooth, and the characters are full. They are submitted to the provincial bureau and ministerial level for acceptance and are in compliance with the standard. Later, the author used a nearly square screen to produce a four-screen bird's-eye screen effect, which also laid the foundation for large-scale color screen printing in the future.
The screen shape is also the plane shape of the frame. The version selection box is generally based on the net content of the manuscript plus the width of the ink zone to determine the size of the frame, and then consider what material and how much material the frame will use. The shape of the frame is mostly rectangular, and only select rare shapes when encountering special substrates.
For example: the handkerchief printing uses square; the printed advertisement on the finished umbrella is affected by the ribs; it adopts triangular or isosceles trapezoid; large-scale color printing is used to strengthen the carrying capacity of the frame and prevent the inward deformation from being selected as hexagon; the concave bottom, The pelvic floor is rounded. In fact, the special screen shape is not only suitable for special printing, but also in the aspects of tension force, tension uniformity, screen printing resolution, and ink volume, especially when producing fine lines and high-mesh screens. Face, but also practical for ordinary planes. The following are elaborated from the following three aspects: force analysis, screen printing experiment, and practical application.
First, the screen plane force analysis screen printing plate is a kind of elastic version, stretching and squeegee both cause the screen to be deformed and require the screen to restore the original state, the frame withstands the restoring force of the screen. This restoring force can be regarded as the sum of the stretching tension and the squeegee force and the shear force generated by the stencil friction during operation of the squeegee. Since the movement force is an instantaneous value, the squeegee force can be manually controlled and the frame can be subjected to force. Can be seen as close to the tension under static conditions. From the viewpoint of 90° stretch net, the higher the tension of the stretch net, the tighter the screen, the more uniform the tension, and the better the quality of the screen. However, the tension of the stretch net will not be transferred to the screen by 100%. The main loss of the tension loss is in the deformation of the frame and the fatigue of the screen. In response to this contradiction, the high-strength wire mesh and the trapezoidal cross-section net frame have come into being. Screen quality. However, if you increase the material of the frame indefinitely, it will increase the weight and affect the actual operation. The deformation of the frame is proportional to its length. The longer the frame is, the larger the deformation is, and the greater the tension loss is. Therefore, the shape of the frame of the frame varies from frame to frame.
On the circular net frame, each point of action is subjected to a screen restoring force in both vertical and horizontal directions, and the resultant force of the restoring force is directed toward the center of the circle to reach equilibrium, and thus no inward deformation occurs. The joints on the hexagonal frame are subjected to the same force, and the six sides are relatively short and are subjected to vertical forces to minimize deformation. The length of the square net frame is equal, which is the smallest deformation in the rectangular net frame, and the best tension evenness after deformation. The smaller the ratio of the short side to the long side of the rectangular net frame is, the larger the deformation is, and the greatest influence on the uniformity of the whole screen plate tension is.
Second, screen printing experiment steps:
1. Use a 2cm x 2cm metal square tube to bend into a 40cm diameter semicircular box on a round bender and then weld together. The same material is again made of hexagonal, square and rectangular mesh frames.
2. Grind the mesh frame and grind it, stick the net glue twice, select a 300 mesh screen to stretch the net on the same stretcher, the tension is about 8kg. The screen plate is left to stand for 3 to 4 days after being stretched.
3. The empty version scraped four pieces of the ground.
4. Use the 60 lines of 1-9 meshes to adjust the picture of the sun. Make the same version of the plate on each of the four types of screen frames. Use each plate to print the two clearest tone charts on the 3mm white glass. Comparing samples printed on screens of various shapes.
Experimental results: The rectangular screen has a slightly poorer uniformity of the ink and the uniformity of the dots. The dots are distorted and incomplete. The quality of Other screen samples is nearly the same.
Third, the actual use of the shape of the screen, round, hexagonal frame stretched tight, even tension, printing effect is good, but in practical applications, the circular mesh frame production using curved machine bending, the process is complex, The printing area is inscribed rectangle and the material is wasted. Although the hexagonal frame is welded with straight edges, it has many welding spots and the angle is difficult to control. There are also problems with the round frame and lack of practicality. Only the square version has the advantages of the above layout, and the processing technology is the same as that of the rectangular version. Therefore, it is better to select a square with a side length of 1:1 when making a net frame or to select a rectangle with a ratio of side length close to 1:1 as much as possible.
When I was just engaged in screen printing, I used 13 large, medium and small screens in different shapes to produce batches of large-scale maps. In order to be faithful to the manuscript and meet the mathematics accuracy of the map, the criss-crossing square-finish net with no jagged edges and the contours as dense as the hairline are printed on the screen, clearly reflecting the rivers, beaches, roads, and residential areas. Heap, all night long.
Turn over the print records in less and more losses, and count the success rate of each numbered screen. The highest success rate and best quality were found in the square prints. After analysis and testing, the layout was changed to 80cm×80cm, 90cm×90cm, and 100cm×120cm. Three groups of 12 screen printing plates were used for recycling. When typography, as many pieces of content as possible together, or a content lined up several times to form a layout, overprinting can not be spliced ​​pattern using a large version of the system, as long as the success is worth it.
Due to the change in the shape of the screen, there were as many as 80 screen printing jobs in the last month, and 3,000 sheets of paper were opened. The success rate was 100%. The screen printing accuracy has a positive error of 2%, and the negative error is zero. The contents of the map are clear, the lines are smooth, and the characters are full. They are submitted to the provincial bureau and ministerial level for acceptance and are in compliance with the standard. Later, the author used a nearly square screen to produce a four-screen bird's-eye screen effect, which also laid the foundation for large-scale color screen printing in the future.
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