Trapping is not allowed not allowed a special case of overlay, first analyze their relationships and characteristics. First, the definition of chromatography allowed No overlay is not printed on different color graphic overlay together by the phenomenon of the original requirements. According to the causes of the different set of rules can be divided into tw o kinds of prohibited and trapping are not allowed. Set of rules is not allowed to graphic printed on paper Inconsistent position on, Zhang and Zhang not a straight line between the phenomena of regulation. Monochrome overlay multicolor products are not allowed if the set of rules will produce the phenomenon are not allowed to overprint, set of rules is not allowed to overprint color offset press appeared the main reason for the phenomenon are not allowed. Trapping is not allowed no matter what the school does not make multi-color version of the phenomenon of graphic register, the school colors and the color version can not make the phenomenon between the register is not allowed in special circumstances overprint. Multi-color offset printing press allowed the phenomenon often appears chromatic, chromatic is not allowed to multi-color printing machine failures often appear overprint one. Second, the classification of chromatography allowed Chromatography allowed under actual production conditions are the following forms. 1. Chromatic closed down Trapping is not allowed to associate finger up and down can not register drag seams, shoot, shoot or register can not register drag the phenomenon of seams, that can only register one end up and down direction. 2. Not allowed to come and go trapping Trapping is not allowed to come and quasi-finger can not register by the body outward, outward register or not register by the phenomenon of the body, which can only register one by the end of the body or outward. 3. No single angle chromatic Trapping is not allowed a single angle of the four corners of the paper there in a corner or two corners of the phenomenon are not allowed to set, regardless of how the school version will always be allowed to set an angle, also known as rejection angle. 4. Local color printing not allowed Local trapping is not allowed in a local paper sets are not allowed, but all rules can register from the line of the phenomenon. Third, the chromatic causes of inaccurate Trapping may be allowed or not allowed by the spell printing down version of deformation caused by tensile loading version, these are caused by human factors. No make-up are generally not allowed a single map while others figure there is no problem, pull the version to come and go the direction of deformation generally occurs in the formation of a local phenomenon of the upper and lower chromatic allowed. With the CTP automatic plate changing technology and the popularity of these reasons is no longer a priority. Analysis of other aspects of the following reasons: 1. Paper stretching deformation Elongation of the paper with water, dehydrated shortening characteristics, completed the first color in the printing paper after the absorption (or prolapse) of water will stretch (or shortening), when printing the second chromatic color are not allowed when the phenomenon occurs. If the paper is uneven irregular stretching, then allowed to produce the type of chromatography is also not fixed. Multicolor overprint monochrome and color because of color and a longer time interval between the printing, paper stretching between the deformation of the colors may be large, so the resulting trapping are not allowed to be obvious. Color and color multi-color machine for printing the time interval between the short, paper is generally absorbent elongation, elongation, and will not be too much color sequence by gradually decreasing, it is generally not allowed to have too much trapping. Paper stretching deformation is inevitable, we can only try to reduce paper deformation and deformation caused by the remedies paper chromatography are not allowed to question. 2. Roller bag lining thickness is inconsistent Lining thickness of the plate cylinder package will cause inconsistencies in the direction of chromatic closed down, the same way, the impression cylinder can lead to inconsistencies in the thickness of the upper and lower chromatic allowed. Inconsistent with the thickness of the main reasons led to the impression cylinder has a sticky surface of the impression cylinder of paper or ink layer, the thickness of printing paper is inconsistent, the impression cylinder wear. In addition, the local non-bag lining formed may also be allowed to rise to the phenomenon of local trapping. 3. Roller pressure is too large Ambassador blanket cylinder pressure produced large deformation, if the paper would have greater flexibility, paper prone to extrusion, that is, the longer the time for the paper to both sides of the more extended deformation, resulting in trapping are not allowed. 4. Drum inadequate bite force of a bite Fourth, preventive measures and solutions Through the above analysis, resulting in trapping are generally not allowed after a fault more difficult, so prevention is very important. 1. Preventive measures Monochrome printing main preventive measures are as follows: ① need to continue trapping in the semi-printed closed to save the plastic film after use to prevent India or moisture due to drying caused by deformation. ② prepress processing or paper over the water to dry compressed air treatment, let the paper printing the full absorption of the water to reduce the deformation. ③ When printing a small amount of water to reduce the deformation of printing paper. ④ multicolor overprint time interval should not exceed 1 day. The longer the interval the more difficult control of deformation of paper, usually a one-time multi-color overprint overprint to finished product, do not stay overnight and then printed. Long single product to be divided into two batches with monochrome printing or cross-overlay (to register as a precondition.) ⑤ Do not adjust the printing process generally bite and packings, in case parameters are not allowed to cause trapping. ⑥ method of loading the correct version and the school version, and pull tight version of an adult version of the cause can not be forced off the plate tensile deformation. ⑦ maximize the use of cross wire feeding the printing paper. Wang silk paper and paper feeding wire to the vertical direction, the direction of the paper to come and go less deformation in the vertical direction is relatively large. Allowed for easy to adjust up and down direction of chromatic correction, not easy to adjust the correct direction to come and go, so it is better cross printed silk paper. Multi-color printing machine main preventive measures are the following: ① pre-press processing or compressed air drying of paper processing, printing paper in order to reduce deformation. ② When printing a small amount of water absorbent paper to reduce the deformation. ③ reasonable package lining of the drum to compensate for elongation of the paper. Decreasing the plate cylinder packings, arranged in four-color machine packings were generally decreasing the amount of 0.1mm, 0.05mm, 0.03mm. ④ school version with the correct version installed to prevent the plate tensile deformation. ⑤ control roller pressure, to prevent the extrusion of paper. Rigid packings, the greatest pressure of not more than 0.25mm. ⑥ hard to make use of packings, in order to reduce the package printing lining compression deformation. ⑦ bite the bite force to ensure compliance standards, to prevent slip of paper. 2. Solution When generating chromatic failure, but also take the following measures to remedy and treatment, the following were listed by type of solution. ① No upper and lower chromatic. Packings to adjust the value of plate length to achieve change in graphics, the following formula. ΔL / ΔR = Lp / Rp △ L is the circumferential length of the printed graphic variation, ΔR is the change in the radius of the plate cylinder, ie ΔR = R, after pre-R, Lp is the length of the plate on the graphic, Rp is the radius of the plate cylinder freedom. When △ L is negative, reducing the length graphic, △ L is positive, the length graphic growth, that is when the plate cylinder packings increase or decrease the radius of embossing rollers, printing graphic length will be reduced, otherwise On the contrary. Either monochrome or multicolor printing machine, any faults are not allowed to appear up and down trapping method can be used for this calibration. When the upper and lower chromatic allowed amount is very small, can be corrected by pulling the version of method can also be printed by changing the method to adjust the pressure, the specific relationship is as follows: only increased the plate cylinder and blanket cylinder between the pressure to shorten the length graphic; only increase between the blanket cylinder and impression cylinder pressure, graphic length growth. ② chromatography allowed to come and go. Monochrome printing the second chromatic color are not allowed to come and go can be found in two first revision through the overlay or overlay. Multi-color printing machine when there are not allowed to come and chromatic changes in the first wire to the printed paper to test whether or not caused by the paper to the wire, because the silk printing papers come to the right direction will cause the paper to expand significantly. If you change the wire can be resolved after the printing would be best to change the wire to the print paper, if not, should not be allowed in which to adjust chromatic color drum pressure. Another version of the method can be applied to the top of the adjusted version of human deformation. ③ No single angle chromatic. Pull with the top version and edition of the ways in which version of local regulation of human deformation. ④ local trapping are not allowed. Check the corresponding parts of the drum situation, identify the reasons are not allowed at the pad level chromatic. Check the color printing paper are not allowed to bite at the bite force, bite force alignment of the teeth. For products with a higher precision chromatic or multi-color text overlay (especially hollow words and text overlay network), it is recommended by multi-color printing machine, do not use monochrome overlay, and the make-up fight as far as possible they are concentrated in seams around, do not fight to drag at the tip, so help to improve the quality of such products, overprint. Either monochrome or multicolor machines are not allowed to occur trapping phenomenon. No chromatic monochrome machine with multi-color multi-color chromatography allowed the major difference is that the printing machine, paper colored groups in a very short delivery time, the deformation of paper is generally expanding, while the monochrome situation is quite different, in paper between the different deformation of India plays a very complex and may also reduce the possibility of expanding, the change may vary. Therefore, the monochrome overlay accuracy of overlay multi-color products is difficult to control, so the general overlay of products with high precision multi-color printing machine.

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