Treatment of printing process problems such as die

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Processing of printing process problems such as die cutting

I. synchronization of die cutting and printing

self adhesive label printing generally needs to be cut into a certain shape before it can be used. On the printing machine with one-time molding of printing die cutting, the synchronization of die cutting and printing is very important. The up and down movement of the die cutting and the up and down movement of the printing workbench are jointly driven by the main drive shaft, so there is synchronization, but the cutting position is determined by the rotation distance of the traction roller controlled by the double crank structure, so it is very critical to adjust the crank radius and the pressure of the paper pressing wheel

II. Plate cracking

at present, photosensitive resin relief plates are mostly used in self-adhesive label printing in China, and this kind of plate often has the problem of plate cracking. The reasons are analyzed below, and the corresponding solutions are put forward

1. The diameter of the plate roller is too small

the smaller the diameter of the plate roller, the greater the tensile force on the printing plate, and the greater the outward tensile force at the printing plate interface, so that the interface of the printing plate is tilted upward, making it not stick firmly on the plate roller. After printing on the machine, the pressure here is greater than that in other places, which is easy to cause the printing plate to crack. In this regard, double-sided adhesive tape with strong adhesion can be used to paste the plate, and the non graphic part of the plate interface can be sealed with adhesive tape

2. Plate material is too hard

plate material is too hard, which will cause the surface of the printing plate to be too brittle, resulting in plate cracking. For this, you can choose a softer plate. Our factory once printed a full plate live part with excellent interlaminar shear and tight shear strength. At first, the plate of Japanese Toyo textile brand kf-95gc was used, and the plate cracked before long. Later, the plate of relatively soft ef-95gc was used for troubleshooting

in addition, dry weather and low temperature in winter also tend to harden the plate, so in winter, the printing plate should be used and made as soon as possible; The temperature in the plate making room is maintained at about 25 ℃ and equipped with humidification equipment; The prepared printing plate is sealed and stored in a plastic bag; Maintain a certain temperature and humidity in the printing workshop. If the printing plate becomes hard after being left unused for a long time, you can rinse the back of the printing plate with hot water to make it soft. However, if the resin version is used, because it can dissolve in water, it must be avoided that water contacts with the technical standards of TPJ series mechanical spring fatigue testing machine of Jinan new era Gold Testing Instrument Co., Ltd. now we will introduce the graphic part on the front of the version one by one, otherwise it is easy to damage the graphic

3. Excessive printing pressure

excessive printing pressure is also easy to lead to the rupture of the printing plate. This phenomenon is particularly easy to occur when there are field graphics and texts at the printing plate interface. Therefore, in the process of printing, we should try to reduce the printing pressure on the premise of ensuring the authenticity of pictures and texts

4. The layout of the layout is unreasonable

some layouts are on the ground from beginning to end. In addition, the diameter of the plate roller is too small, so the plate mouth is easy to be cocked up when printing, and it is easy to crack the plate when printing. If you choose a plate roller that is a little larger than the actual step distance, and leave a small plate base at the edge of the plate during plate making, the plate can be attached to the plate roller more easily, which greatly reduces the occurrence of plate cracking

III. glue return shadow

in the relief printing process, the graphic part of the printing plate is higher than the non graphic part. When the ink on the plate roller is transferred to the plate, the non graphic part of the printing plate is not inked, and the ink on the plate roller relative to the non graphic part has no place to transfer. Due to the small number of ink rollers in relief printing machine, the residual ink on the plate roller cannot be evenly opened in time, resulting in local imbalance of ink volume. The local ink volume is larger than the ink volume required for printing, so that the local image and text color of the print is deeper than that of other parts, resulting in glue back shadow

it can be seen that the generation of adhesive return shadow is closely related to the rationality of the ink path design of self-adhesive printing machine. There are several ways to solve the glue back shadow

1. Increase the number of inking rollers in the unit

add several more inking rollers in the printing unit, so that the ink layer on the plate roller can be more evenly transferred to the printing plate on the basis of different fixtures, so as to greatly reduce the depth of glue return

2. Transform the master roller

for some long version activities, change the diameter of the master roller to be as thick as the master roller, which can also greatly reduce the depth of the glue back shadow. The principle is: the relative position of the ink area on the plate roller is consistent with that on the plate roller, and the thickness of the ink layer is relatively stable. This method is suitable for satellite self-adhesive label printing machine

3. Adjust the ink feeding method

the specific method is to release the ink teeth and adjust the ink nails to control the amount of ink. In this way, the ink can be transferred to the inking roller as evenly as possible while ensuring the amount of ink required for printing, so as to facilitate the ink to be transferred to the plate roller more evenly, so as to reduce the glue back shadow

IV. ink does not dry

there are many reasons for ink to dry, mainly reflected in the following aspects

1. Too much ink supply

too much ink supply leads to too thick ink layer and the UV lamp cannot dry the ink in time. This phenomenon mainly occurs when printing live parts. In this case, you can try to reduce the ink supply without affecting the printing quality. If you can't get good results, you can consider moving the field to the first few groups of printing units for printing. In this way, after baking with multiple UV lamps, the fault will be reduced

the power of the lamp is insufficient

uv lamp aging or other reasons cause insufficient power of the UV lamp, which will also cause the ink to dry. In this regard, adjust the power of the UV lamp to the maximum gear. If it is not dry, solve it by changing the UV lamp tube

3. Printing speed is too fast

printing speed is too fast will lead to UV lamp too late to dry ink. This can be solved by changing the printing unit or reducing the printing speed. When printing live parts, the printing speed should be kept at about 20 meters/minute

v. dirty printing

there are often some unobvious dirty phenomena in the printing process. The following is an analysis of this problem

1. Fixed hanging dirty

this situation is mainly caused by dirty things on the surface of the printing plate or the edge of the plate upturned, which shows that there are dirty spots at the fixed position of the printed text. If it is caused by the warping of the plate, there is a line in the graphic part, and its color is consistent with the printing color of the warped printing plate. The problem can be solved by cleaning the plate or pressing the warped part on the edge of the plate

2. Unfixed hanging is used in the construction of power transmission and transformation. The dirty tensile testing machine is mainly caused by dirt or hard injuries on the backup roller, which is manifested as periodic unfixed hanging dirty. The solution is to carefully check and replace the rubber roller with a hard injury or clean up the dirt on the plate roller

3. Rubbing the paper causes a similar phenomenon of hanging dirty.

in the process of moving the paper, the paper rubs against the edge of the UV lamp, or there is a foreign matter rubbing the paper on the paper pressing roller of the machine, which will cause the surface of the paper to be scratched, and the ink printed on it will produce a similar effect of hanging dirty. Especially when printing thick film self-adhesive labels, due to the irradiation of UV lamp, the material will deform and bulge when heated, which is more likely to happen. In this regard, you should carefully observe to find out where the paper is rubbed, and eliminate the dirt by adjusting the angle of the UV lamp or cleaning the paper pressing roller

4. Large amount of ink causes dirty hanging or paste up phenomenon

letterpress printing is a water-free printing method, and large amount of ink is easy to cause dirty hanging or paste up of graphic and text parts. In addition, too thin ink is also easy to paste the version and cause the image and text to paste. The solution is to minimize the amount of ink or increase the viscosity of the ink according to the requirements of live parts

above, we have analyzed several common problems in self-adhesive label printing, hoping to help you in your daily work. Of course, in addition to the reasons I mentioned, there are many factors that cause the poor printing quality of self-adhesive labels. I hope you can carefully summarize in your future work, draw lessons, and constantly improve product quality

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