Rattan Chair, Wicker Chair, Garden Chair Ningbo Jiangbei Xiangyuan Leisure Products Co., Ltd. , http://www.china-outdoorfurniture.com
One, steel drum printing is easy to block (blocking the net)
Sealing refers to the phenomenon that the screen printing plate graphic can not transfer ink to the steel drum during printing. This phenomenon will affect the quality of the drum screen printing, because the text and graphics will appear incomplete, so that it can not be identified. There are several reasons for this phenomenon:
(I) Effects of temperature, humidity, and ink properties at the production site Screen printing has certain temperature and humidity requirements for the production site of the printing. If the production site has high temperature and low relative humidity, volatile solvents in the ink will quickly Volatilize, the viscosity of the ink becomes high, thus blocking the mesh; In addition, if the residence time is too long, it will produce a paste blocking phenomenon, the longer the paste is more serious; secondly, if the ambient temperature is low, the ink flows Poor sex, but also easy to produce paste version, block version. Most steel drum manufacturers use screen printing, their work sites are open air, and the temperature and humidity of their production sites must be affected by the local natural climatic conditions. In particular, in the northwest region of China, the natural climate is dry, the solvent in the ink evaporates quickly, and the plate-closing phenomenon is prone to occur. Therefore, attention should be paid to the occurrence of such problems during operation.
(B), the impact of the screen version of the body made of a good version of the screen washed with water before use, and can be used after drying. If printing is not performed for a long time after making a good version, dust will adhere to more or less during the preservation process, and if it is not cleaned at the time of printing, it will result in a cover plate.
(C), the reasons for the pressure during printing Screen printing of steel drums, sometimes due to smaller batches, frequent changes, so generally use manual printing. In manual printing, the operator's arm is mainly used to adjust the embossing force. If the imprinting force is small, the printing plate cannot touch the surface of the drum and printing cannot be performed. Excessive embossing force will cause the squeegee to bend and deform. The contact between the squeegee and the wire mesh and the steel drum is not in line contact but surface contact. In this way, each squeegee will not be able to scrape the ink and leave it. Residual ink, after a certain time, it will cause conjunctival closure.
(4) Improper clearance between screen plate and steel drum The gap between the screen plate and the steel drum should not be too small. The gap is too small. After the squeegee printing, the screen version cannot be separated from the steel drum, but it is bonded to the steel drum. When the screen plate is lifted, a certain amount of ink adheres to the bottom of the plate, which is also likely to cause the plate closure.
(e), the impact of ink Screen printing ink is not high, it can be applied to all types of ink. Such as oil, water, synthetic resin type, powder and other inks can be used. Therefore, the size of the pigments and other solid materials in the ink is uneven. When the particles are large, the phenomenon of the seal is liable to occur. In addition, the number of screen meshes to be used and the area of ​​the through-holes are smaller than those of the ink, making it difficult for coarser particles of ink to pass through the mesh and causing screen closure. Due to the large size of the ink particles caused by the seal, can be selected by better quality, small particle size, fine ink to solve.
The ink is dried too quickly during the printing process, and it is also likely to cause a seal. In order to print graphics on the surface of steel drums, the most prominent feature of their requirements is drying faster. Therefore, it is best to use a volatile drying ink when scraping the graphics for steel drums. In order not to seal the ink, it is necessary to select an appropriate solvent to control the drying speed during printing. In the selection of ink to take into account the impact of climatic conditions, under normal circumstances, the use of fast-drying ink in winter; in the summer should be added to the ink in the drying agent, if the use of late drying agent also occurs in the phenomenon of plate closure, you must replace other Type ink.
In the printing process of steel drums, the viscosity of the ink cannot be too high, because the viscosity is too high, and the ink has poor flowability, which can easily cause the plate closure. The graphics on the steel drums are generally small, and the screen plates are relatively small. Ink consumption is correspondingly small. If the ink is over-prepared at one time, the ink solvent evaporates, resulting in increased viscosity of the ink, and it is also prone to netting. Therefore, the amount of ink used for each preparation should be appropriate.
After the failure of the sealing network, according to the nature of the ink on the screen plate, scrub with an appropriate solvent. The method of scrubbing is to start with the printing surface first, gently wipe from the middle to the periphery, check the printing plate after wiping, if there is a defect, it should be promptly repaired, and can be reused after being repaired. It should be noted that the screen plate can not be used for multiple generations of the plate, because the plate becomes thinner each time it is scrubbed. If the plate is damaged due to a large amount of defects, the plate has to be replaced with a new one.
Second, the adhesion of ink on the drum is poor When the graphics are printed on the surface of the drum, the steel drum is generally coated with paint. Since the surface of the drum has been coated with paint, there is even a certain amount of dust and oil, which can cause ink. Poor adhesion to the steel drum; the poor adhesion of the ink itself will also directly lead to poor adhesion of the graphic image on the drum surface. If the user has special requirements in terms of graphic adhesion, it is better to replace the ink with strong adhesion for printing. Improper use of thinner can also cause poor adhesion of the ink film. Therefore, when selecting the drum ink dilution solvent, it is necessary to consider the nature of the ink, so as to avoid the ink and steel drum bond is not strong.
3. After the printing of steel drums, the edges of the graphics are not neat. After the steel drums with burrs and incomplete phenomena are printed, serrated burrs on the edges of the graphics and texts often appear, including incomplete or broken wires. There are many factors that cause such problems, but mainly due to the quality of the screen version. We analyze from the following aspects:
1. The quality of the sensitized adhesive on the screen is poor and the resolution is not high, resulting in broken or incomplete lines.
2. When the exposure time is insufficient or the exposure time is too long in the plate making process, the development is not sufficient, and the edge of the screen printing artwork is not neat, and there will be sawtooth. A good screen version, the edges of the graphic should be smooth and tidy.
3. The surface of the screen plate is not smooth. When printing is performed, there is still a gap between the screen plate and the steel drum. Due to the ink penetrating into the air, a burr occurs on the edge of the printing ink.
4. In the printing process, due to swelling of the printing film after exposure to the solvent, and the degree of swelling in the latitude and longitude is different, the surface of the printing film is uneven. During the printing, the gap between the screen plate and the steel drum partially appears. When the ink is suspended, the ink film will have burrs.
To prevent the appearance of jagged burrs, when making screen plates and screen plates, you should:
1. When making a plate, you should choose the screen with a higher mesh number as much as possible.
2. When making plates, the best quality and high resolution photosensitive materials should be selected.
3, to the screen version of the plastic coating, we must pay attention to the thickness of the film, if the thickness of the film is thin, the expansion of deformation is large.
4, as much as possible using diagonal stretch law stretching net, under normal circumstances, the angle of 22 .5 ° is the best.
5. If the printed artwork lines are fine, the indirect plate making method should be used as much as possible, because indirect legal plates generally do not have burrs.
6, in the plate making and printing process, try to control the temperature expansion factor, the use of a small thermal expansion coefficient of the photosensitive material.
7. Improve the quality of plate-making to ensure that the surface of the screen plate is smooth and smooth, and the edges of the screen lines must be neat.
8, the use of spray guns spray screen version to improve the development effect.
9. The distance between the screen plate and the steel drum, the angle of the scraper and the pressure of the stamp should be appropriate.
IV. Ink thickness on the surface of the drum The unevenness of the ink film thickness printed on the surface of the drum is different. The reasons for this phenomenon are various. In terms of ink, it is mainly because the ink is improperly blended, or the ink is blended in the normally formulated ink. When printing, the solvent expands and softens due to the effect of the solvent, and the ink is blocked by the mesh opening so that the ink cannot pass through.
In order to prevent such failures, the ink after dispensing (especially the ink that has not been used up for the last time) must be filtered before use and then used again. Every time the printing is completed, the printing plate must be washed with thinner and dried before it can be stored in the warehouse. When keeping the screen printing plates, be sure to pay attention to dust, moisture and hard, sharp object collisions and scratches.
In screen printing, the main function of the squeegee is to fill ink, evenly ink, scrape ink and imprint. Therefore, when the scraper scribes images on the steel drum, under the effect of the imprinting force, the ink can not only be printed on the steel drum through the screen plate, so that the ink is fully filled into the mesh of the screen, and Under the effect of the imprinting force, the squeegee squeezes the ink and scrapes from one end of the printing plate to the other. However, due to uneven application of force or damage to the cutting edge of the front end of the squeegee, an uneven thickness of the ink layer or a trace along the direction of movement of the squeegee may occur during the squeegee printing process. Therefore, the edge of the scraper must be well protected so that no damage occurs. If there is damage, it is necessary to grind it with a grinder or a surface grinder.
Fifth, the size of the graphic image on the steel drum. After the screen printing, sometimes the size of the picture on the steel drum is enlarged. The main reason for this phenomenon is the low viscosity of the ink and the excessive flowability; The enlargement of the size at the time of manufacture is also one of the factors causing the enlargement of the printed image and text.
In order to avoid the ink flowability caused by the overflow of the ink after printing, resulting in increased size of the graphic after printing, can be added to a certain amount of thickening agent in the ink flow is too large, in order to reduce the flow of ink, also Fast-drying inks can be used to speed up the drying of the ink after printing and reduce the flow of ink. When making a screen layout, the quality of the screen plate must be strictly guaranteed.
6. After the printing of the graphic ink on the surface of the steel drum, the cracking and splitting of the ink on the graphic surface are printed. The cracking phenomenon of the graphic and text is mainly caused by the effect of the solvent and the large temperature change. In addition, when using the scraper to scribble graphics on the steel drum, if the scraper pressure is insufficient, the ink sticky and the flow is not smooth, the printing ink layer will be false, and the white dot phenomenon will occur; if the scraper pressure is too large, When the fluidity is high and the viscosity is low, the ink will permeate between the edge of the plate and the steel drum, and ink inward tends to occur. Under the pressure of the squeegee, when the ink is transferred to the surface of the steel drum, the ink is pulled between the steel drum and the stencil plate at the moment of separation, and is transferred to the surface of the steel drum and adhered to the screen plate. In part, the following situations will occur:
1. The ink fills the gap in the screen plate.
2. The ink is under pressure from the squeegee and is in a contracted state.
3, off the plate, the ink was dragged between the wire mesh and steel drums.
After the ink is broken, the viscoelasticity is restored to its original shape. This splitting phenomenon depends on the viscoelasticity, the off-plate speed, the interfacial tension between the ink and the screen plate, and the absorbability of the ink on the drum. The splitting phenomenon is an important factor in the formation of ink ink layers.
In order to prevent the occurrence of cracking and splitting of the ink layer, it is necessary to consider the nature of the ink and the solvent resistance of the drum surface after coating, and pay attention to the temperature and humidity at the printing site to effectively prevent the ink. Cracking and splitting of the membrane occur.
Talking about Several Technical Problems in Screen Printing of Steel Barrels
In recent years, with the rapid development of the packaging industry, users have become increasingly demanding for metal drums for metal packaging containers. For this reason, steel drum packaging companies have also begun to adopt new technologies in the manufacture and coating of steel drums. , new technology, in order to improve product quality. In addition to paint on the surface of steel drums, users are now advertising on the surface of steel drums in order to promote their own products. The traditional production process can not meet the user's requirements, so beautiful, generous, easy plate making, cheap, printing methods are diverse, flexible, easy to grasp the technology of screen printing technology, soon to be applied in the steel barrel enterprises, and Has become a beautiful scenery on the steel barrel. However, because most steel drum companies lack the screen printing technology, some technical problems often occur in the actual production operations. The following analysis of several common problems.
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