In the daily printing process of self-adhesive labels , we often encounter some difficult problems. If these problems cannot be solved in a timely and effective manner, it will not only affect normal production, but may even cause certain economic losses. The author has been engaged in self-adhesive label printing for many years, summed up some tips in printing production, and would like to share with you.
Tips in the process of making plates
1. Shorten the exposure time and solve the problem of the transition network's bluntness
I have printed a drug label with a transitional network effect. The effect of the client's request for the transition network is softer. However, the transitional outlets for proofing and printing are relatively blunt and cannot meet the needs of customers. After observing, the author found that the minimum dot size in the transition network is about 3%, which is basically the smallest dot that can be exposed by the embossed resin plate. If the dot is reduced and the film is re-released, the phenomenon of small dot loss is likely to occur after printing, so this problem cannot be solved by re-sending the film. Since the embossed resin plate is imaged by light curing, the author allows the plate-making personnel to shorten the exposure time so that the dots on the resin plate are smaller than the dots exposed during the normal exposure time. After the proofing again, the effect of the transition network becomes Soft, the customer is very satisfied with it, and we have successfully completed this order.
2. Back exposure solves the problem of large-area transition network
Anyone familiar with the flexographic plate making process knows that there is a back exposure process in the flexographic plate making process, the purpose of which is to make the graphic and the book base more firmly combined. However, many people may not know that this back exposure process can also be applied to the plate making process of the embossing resin plate. In daily production, we often encounter jobs with large-area flat nets or large-area transition nets. In the process of printing, the problem of small net points is often lost due to poor exposure time, especially for large areas. The printing plate of the transition network is more demanding on the exposure time: if the time is too long, it may be pasted, and if the time is too short, the network may be dropped. At this time, the back exposure process can be used in the plate making process, that is, the back side of the resin plate is exposed, and the back exposure time is flexibly controlled according to different jobs. Practice has confirmed that the resin plate after the back exposure treatment is not prone to the phenomenon of the dot when the large-area transition point is exposed.
Tips in the printing process
1. Printing remover removes white spots
I have encountered such a problem in the past: When printing a batch of jobs that are in urgent need of delivery, the surface of the raw materials is too dusty, but because there is no time to replace the raw materials, and the dusting cloth is used up, a large area of ​​white spots appears during printing. . In order to solve this problem, the author adopted an uncommon method: make a solid version, print the UV light-removing agent on the surface of the raw material first, and then print the ink according to the normal process. Since the first printed UV eliminator has already removed or covered the dust on the surface of the raw material, there is basically no white spot on the back printing ink. Moreover, since the color of the UV bleaching agent is very light, it does not affect the hue of the printing ink of the back. But doing so will greatly increase production costs, so it can only be used for emergency purposes and cannot be used as a routine solution.
2. Cleverly remove static interference
I have also encountered such a problem: the North quit a brush offset printing plant winter film material, they would often missing material rewinding and printing presses operating system crash phenomenon. The plant uses the Linde LPM300 intermittent sticker press, which has stable performance, but why is the operating system dead? Later, it was discovered that the “culprit†was the large amount of static electricity generated when printing film materials. Due to the interference of static electricity, the operating system of the device often crashes and does not work properly, and also causes the film material to be wound up. At that time, the production task was urgent, and there was no time to install the static elimination device on the equipment. Therefore, the author suggested adding two humidifiers in the workshop to improve the relative humidity of the workshop, greatly eliminating the influence of static electricity on the equipment and materials, and finally the production was smoothly carried out. .
3. Partial adjustment of the double-sided adhesive thickness of the plate to achieve the desired printing effect
In the process of self-adhesive label printing, the printing of the partial area is too dark or too light. In this case, the thickness of the double-sided adhesive can be adjusted by adjusting the thickness of the partial-coated double-sided tape without re-spinning the film. The specific method is: if the partial area printing color is too deep, the double-sided tape under the area printing plate can be removed, which is equivalent to reducing the local printing pressure, and the printing color will be lighter. Similarly, if the partial area printing color is too light, a layer of double-sided tape can be added under the printing plate of the area, which is equivalent to increasing the local printing pressure, and the printing color can be deepened. By adjusting the local pressure of the graphic in this way, it is often able to solve some problems and avoid the trouble of re-selling the film and plate making, and also save the plate.
4. Cleverly remove the paper wheel impression
In the process of self-adhesive label printing, the platen of the delivery part tends to push the material out of the impression. The factory has to widen the material (generally 10 mm more than the actual printing width), so that the platen presses against the edge of the material. To avoid the appearance of marks on the surface of the finished label. However, this method is very wasteful of raw materials. In fact, I recommend attaching a layer of self-adhesive material on the surface of the platen roller (paper or film material can be used, it is recommended to use PET material, the best effect), which can greatly reduce or even eliminate the pressure paper. The impression that the wheel presses on the surface of the material. With this method, we can print labels with the smallest width of raw materials, greatly reducing the waste of raw materials.
5. Solution to the blistering phenomenon of coated paper
Once, when I used a cross-back printing machine to print large-area physical labels, there was a phenomenon of material foaming. At that time, coated paper self-adhesive materials were used. It is strange that bubbles are generated on the surface of the self-adhesive material. In the past, I have encountered the phenomenon of material foaming, but the bubbles appear between the surface material and the adhesive of the self-adhesive material. The phenomenon of bubbles on the surface material is the first time. According to the analysis, the bubble is caused by the separation of the surface material due to the adhesive force. The hatchback label printing machine is prone to sticking paper when printing large-area solid labels, mainly because of the high viscosity of the ink or the printing pressure. However, if the ink is adjusted to the most dilute state and the printing pressure is minimized, the surface layer of the self-adhesive material will occasionally foam. This shows that there are not only problems with ink and printing pressure, but what other reasons are there? In the end, the author found this reason, that is, the resin plate is deformed. Since the resin plate is deformed due to loss of moisture after being left for a while, it usually appears as a middle depression and a wrap around. At that time, an old resin plate was used. If the plate was used without being soaked in warm water, it was flat on the surface, but it was actually low in the middle and high in the periphery. The hatchback label printing machine adopts a flat flattening method, so that the depression of the center of the layout causes a strong adhesive force during printing, thereby stratifying the surface material of the self-adhesive material. After understanding this situation, the author dipped the resin plate in warm water for a period of time, so that the resin plate fully absorbed the water and restored its original shape; then printed on the machine, the foaming phenomenon disappeared.
The above points are some tips that the author has summarized in the production practice for many years, hoping to help the vast number of printing industry peers. The inheritance and development of technology requires communication. Only the same industry personnel can communicate more, learn from each other's strengths, and go to the rough and fine, and the self-adhesive label printing technology can be well developed and innovated. At the same time, we also expect more peers to share some of the experiences and tips summed up in daily production.
The above content is selected from the 4th issue of Keyin Media's " Label Technology " in 2010. For more journal content, please pay attention to the journal channel .
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