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The importance of the screen printing network from its network of selected adjustment method from discomfort

Addtime：2015/7/4 11:11:40 Hits：1672

The importance of the screen printing network from its network of selected adjustment method from discomfort
As we all know, the quality of the screen printing is affected by a number of variable factors, net from one of the most important factors. In most cases, the print quality and registration issues are to blame for the network from inappropriate or to compensate for the net from the discomfort and make some adjustments.
Network distance, i.e. from the network printing plate surface and the substrate surface (see FIG. 1). In screen printing, in order to avoid stencil stick to the substrate, the network must maintain a certain distance between the plate and the substrate. Once the stencil stick to the substrate, it will seriously affect the printing quality, the role of network distance is effectively overcome this problem, so that the net version only contact with the substrate at the squeegee blade, once scraper scratched, screen Rebound , screen and substrate instant detachment, to avoid dragging and smearing ink and so on.
In addition, you should also understand the "spring from the" concept, in the screen printing it is closely related with the network distance, but unlike network distance.
"Rebound distance" refers to the squeegee blade after halftone slow upward bounce distance, it occurs to start printing, and only in the squeegee blade process, which ensures screen to quickly bounced back, out of the substrate .
Screen Printing in general net distance of 9.5-12.7mm, but more reasonable and more used is 1.5-3.0mm. Too distance network to the print quality and register a lot of problems, so the net from as small as possible. When printing a number of high precision products, the allowable amount stencil deformation directly determine the size of the network distance. Printing electronic products, stainless steel mesh screen from the often smaller, about 0.1-0.2mm.
Therefore, whether or textile printing graphics, network distance is an argument worthy of special attention. Once the network from inappropriate or inconsistent, would cause unnecessary damage to the printer, it needs to be carefully controlled.
A quasi-significant relationship with the positioning sleeve
In the multi-color and four-color network printing, you must work well with color registration problems, while net from the pair of registration and plays a vital role. Strictly speaking, there is a network it is impossible to make prints from exactly the same with the original, which is due to screen in the printing process of stretching deformation due. Net from larger blade pressure will be greater, the larger the screen is stretched, resulting in an offset pattern on the substrate. Net from small, to a certain extent, can improve the situation. Therefore, in order to reduce the image shift, the network requires the smallest possible pitch selected. Registration for some high precision prints, recommended that the network distance of 1.5mm, maximum and do not exceed 3mm.
With the increase of network distance, there will be many problems. First, in order to ensure contact with the screen substrate, to achieve the transfer of ink, squeegee pressure must increase the force applied to the ends of the blade inevitably larger. The frame is relatively speaking, the longer the blade, the more prominent this phenomenon. This not only increases the degree of deformation of the pattern, but also seriously affect the quality of printing.
Also, sometimes the printed pattern pulled oblique and elongated, causing part of the reason for this situation is the network from problems, but also the pattern of location, direction and length of the blade scraper to run about.
To maintain a uniform distance network in screen printing is quite important. If the front screen of the net from about four inconsistent image will appear on the corresponding position offset. In this case, no matter how the operator effort, the second color will never be the first phase of a color registration. Obviously, if printed in a variety of colors can not register the whole job will be scrapped.
It is worth mentioning that, in printed electronic circuits, some pattern deformation can be calculated at the time of pre-compensation did not count pattern. In addition, some manufacturers have introduced equipment has overcome these problems function.
Second, critical to image quality
Net margin setting is not appropriate, in the printing process, the blade pressure to increase or decrease, this will affect the quality of printing, copying will cause poor accuracy, blur, bubbles, ghosting, dot loss, poor edge sharpness, moire the pattern of incomplete and so on.
Net from not set too large, will cause other problems. For example, the need to increase the squeegee blade pressure, so that the screen can come into contact with the substrate, but prior to contacting the substrate with the screen, the ink had been squeezed into the printing screen surface, if such a serious case, bound It will rub dirty substrates or printed pattern on the substrate. Squeegee pressure, but also damage to the printed image, resulting in network deformation or dot gain.
The larger blade pressure, screen printing in the rebound after the faster speed, the ink can not be completely transferred to the substrate, followed cause a moire pattern is not complete, drawing, bubbles, and poor edge definition printing flaws.
Resulting in poor printing quality is another reason for the low screen tension, mesh distance is too small. In this case, in the course of the squeegee blade screen will wrinkle, ripple in print form, eventually leading to severe image distortion and ghosting.
Third, determine the thickness and color ink adhesion
Ink adhesion may be caused by non-uniform thickness due to the following factors: (l) screen is not parallel with the substrate; (2) the net margin, scraper and screen tension volatile; (3) Net result from excessive blade deformation. Any one of these factors may result in uneven ink adhesion, the final print color shades.
Network from small to ensure uniform ink adhesion, network distance is too large, it is likely to cause uneven ink adhesion, especially at both ends of the blade, and more uneven ink adhesion.
Fourth, the impact of network version and blade durability
Screen, screen printing process and scratch month are using flexible, in the course of repeated use, if the force is too large, will lead to their elastic damping even disappear. Net away from the big, squeegee pressure is bound to increase, in such conditions, screen and squeegee durability will be greatly weakened.
Fifth, related to the production rate and labor intensity
Network distance is too large, it will reduce the production rate. This is because prior to the printing process, the ink in the extrusion blade passes through the mesh to facilitate their arrival substrates, but also squeeze screen, into contact with the substrate surface. In this process, the tongue can be consumed and the pressure of the knife transfer, in largely reducing the production speed. In the manual printing, printers must consume more force printing, so will be particularly tired, and sometimes vulnerable to injuries.
Sixth, how to reduce the net from
To reduce the network from the first light needs to improve screen tension. Screen tension high, it can reduce network distance, increase printing speed. However, increasing the degree of screen tension is restricted by other factors, but the minimum required to meet the printing.
Keep in mind that the larger the screen, the screen is not easy to achieve high tension, therefore, in consideration of the network from the screen, the need to consider screen size and screen tension. In general, the tension should be within 18-25N / cm range, so blindly increase screen tension is not desirable. In addition, each screen in each screen tension to be consistent. In fact, the screen tension agreement itself is more important than the tension, so that not only ensure the overprint between color and color accuracy, but also to ensure consistent squeegee pressure.
In addition to the network version of tension, another noteworthy that ink. Ink viscosity and rheology of the ink, the ink composition, size of the ink particles, the surface tension and the storage time, and if the viscosity of the ink is large, you can add some of the aid to the ink or switch to other ink. Under the same premise screen tension, reducing the viscosity of the ink, you can make the net from the smaller.
Screen technical specifications is an important factor ink transfer effect. The smaller the area of the mesh screen (such as a mesh diameter 27-31μm), the smaller the ink and substrate surface peeling force required. Less force required, the net can be smaller distance.
Surface substrates and also affect the ink transfer from the version factors. Halftone and ink absorption intensity from the substrate surface more easily. Absorption capacity of the textile surface is strong, so it is easy to screen out with the substrate, which is the textile printing network from the network than any other graphic printed from small causes. Substrate surface tension will affect the surface energy of the ink, so India from version also has some influence.
Distance network decided to also screen size and other factors, blade length (as opposed to screen), the printed pattern size (relative to the screen), and type (solid pattern and requires a large network from non-field pattern) pattern and so on.
Some of these factors can be changed, while others can not be changed. Every print has its specific printing conditions, we must understand that in different printing conditions necessary to make the appropriate adjustments distance network, which is very important. Through standard operating procedures and test new materials to buy, in order to ensure the successful completion of the fastest on the version and debugging.
Seven network distance measurement method
There are two ways to regulate and determine the net margin. Many automatic printing and some manual network printer with the appropriate network from regulation, the problem is that most can only be a rough adjustment, only a few high-end device is equipped with readable dial, digital display network can pitch. Therefore, in most cases, you have to rely on the operator to adjust their own.
In practice, the operator has worked out a number of methods and techniques to measure and control the network from which, the easiest way is to make use washer, the washer on the four corners of the printing station, and then flat on the fourth screen On a washer, a different network from the use of different washers. To do this, you can also make a number of different thickness shims to accommodate a variety of needs from different networks, ensuring the accuracy of the network from the set. Another relatively simple method is to distance the table or vacuum table with the bottom surface of the wedge ruler or tape measure to screen
If you have a printer with a readable dial, and can be read directly from the value of the network, of course, this is the most convenient. However, as mentioned above, most of the cases rely on manual adjustment, if the net from the tone set properly, trouble is relatively large. Screen printing operator last option is to use the machinery from the side of the meter. The meter on the screen surface, the table zero, then slowly push down firmly until the halftone exposure to the substrate surface, the meter value minus stencil thickness value, the resulting difference is the from the department's network. Distance measuring net measurement, as long as the right way, the result is more accurate. Using this gauge, the requirements before each measurement must be reset at the same time, it has limited movement on the screen range. So, in this sense, the use of this gauge is not very convenient in some press. However, to date, screen printing industry is the only method of measuring tools.
The US Screen Printing Technology Foundation (SYTF) recently introduced a more efficient network of distance measuring tools - electronic measuring instrument, capable of faster and more accurately measure the net at any distance on screen. The gauge is easy to use, can be displayed at any time from the value network, to facilitate the operator to quickly complete work on a version of the debugger.
On textile printing network from a few points require special instructions. Textiles is a particularly strong absorbent substrates, it is usually better than other network from the network by printing a small distance.
Ideal network distance should be 0.8-1.6mm. However, the specific set shall be based on an integrated screen tension, screen size, and the ink used and other factors. Net from the small, attached to the network can also reduce the amount of ink printing press.
Since the textile printing in multiple printing stage using multiple print heads is completed, therefore, consistency from each print station network is particularly important to ensure a consistent registration for each color ink thickness and color. In addition, if you want to print the same pattern on some clothing, along with changes in the thickness of clothing, net distance must be adjusted accordingly.

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