Dry goods sharing | Collection of label printing issues

Plate making problem

1. Overprinting is not allowed

1) When imposition, if the position of the graphic or the rule line is improperly matched, it is very difficult to achieve accurate overprinting during printing. Therefore, it is necessary to maximize the accuracy of imposition, especially the use of high magnification magnification.

2) There are many printing times, which may cause poor overprinting. In general, inaccurate overprinting rarely occurs when only one exposure is made, but it is not the case when printing multiple times. If you have to perform multiple exposures, you must use exposure paper to perform zone exposure.

2. Virtual Edition

If the PS plate is not tightly attached to the photosensitive layer of the film, it will cause a virtual version (virtual network), and the printed plate may have problems such as ghosting and blurring. In this case, you can turn the PS version to an angle, and then pad a few sheets of paper under it, and extend the exposure time.

3. Shrinkage of outlets

Generally, it is caused by overexposure, developer concentration is too high, development time is too long, and development temperature is too high, and the corresponding treatment method can be adopted.

The loss of small dots and poor field density are generally caused by insufficient image density and overexposure. The corresponding processing method is to recopy the film and shorten the exposure time.

4. The printed matter is sticky and dirty

It is generally caused by underexposure, underdevelopment or overexposure, developer failure, film yellowing or fogging. The corresponding processing method is to increase the exposure time, select the appropriate developing conditions, replace with a new developer or copy the film again.

Ink problem

1. Flying ink

The ink is scattered like mist from the ink rollers.

Cause: The viscosity of the ink is too large: the ink filament is too long and too soft; the ink stores static electricity and attracts the opposite charges in the dry air.

Solution: reduce the viscosity of the ink, add an appropriate amount of debonding agent; reduce the fluidity of the ink; reduce the printing speed: install a static eliminator on the printing machine to reduce the effect of static electricity.

2. Sticky

The back side of the printed matter is smeared by the ink on the front side of the next printed matter, or the ink on the impression cylinder is transferred to the back side of another printed matter.

Causes: The penetrability of the ink is poor, or the curing is too slow; the amount of ink is too large; the paper surface has poor adsorption. Solution: Improve the penetration, drying and solidification of the ink: reduce the amount of the ink appropriately; choose paper with strong absorption.

3. Paper brushing

During printing, the paper fluffs when it leaves the blanket.

Cause: Mainly because of the high viscosity of the ink, the paper reaches or exceeds the critical drawing speed.

Solution: Add thinner or remove adhesive properly to reduce ink viscosity.

4. Block version

The ink and paper powder are blended into a scum form and attached to the surface of the printing plate, blanket and printed matter.

Causes: The amount of ink is too large: the viscosity of the ink is too small or too large, and the dispersion of resin and pigment is uneven: the proportion of the pigment is large: the strength of the paper surface is poor, and the paper powder is easy to fall off.

Solution: reduce the amount of ink; appropriately adjust the viscosity of the ink: replace the pigment: control the shedding of paper powder; frequently clean the blockage on the printing plate.

5. Powdering

Gently wipe the surface of the printed matter, the ink on it falls off in powder form.

Causes: Insufficient film-forming agent in the ink: too much powder in the ink and thick ink quality: the ink film is soft but not firm. The dustiness on the paper surface is large, and the amount of ink absorption is large.

Solution: Add an appropriate amount of gloss paste containing more film-forming resin and an appropriate amount of desiccant to the ink to speed up the drying of the ink: mix with an appropriate amount of hard ink to polish the printed matter.

Blanket problem

1. Plastic deformation of the blanket

The pressure on the blanket in use is different, and the plastic deformation of the thickness is also different, which will cause the uneven thickness of the blanket.

The greater the pressure, the greater the pressure on the blanket where there is paper, and the more likely to be uneven plastic deformation. Therefore, when printing, when the ink can be transferred well, the printing pressure should not be too large, and the best pressure should be used for printing; the tightness of the blanket should be moderate, and the tighter the tighter. The thinner the rubber layer of the blanket, the worse the sensitive elasticity, the more likely to be uneven plastic deformation; long-term mass printing of a certain size of paper will cause large local plastic deformation: after a period of printing, the surface of the blanket Because of physical adsorption, many paper wool and paper powder are adhered. If not cleaned in time, the thick paper wool and paper powder will increase the local printing pressure, and will also cause greater plastic deformation locally: when printing cardboard, the trailing edge Paper scraps due to cutting are easy to accumulate under the action of water and ink on the blankets outside the pattern edge near the trailing edge of the cardboard. Due to the uneven cutting of the cardboard, when printing some longer cardboard, The accumulated paper scraps can cause the blanket to sag there. Therefore, when printing paper and paperboard that are prone to lint and powder, the rubber blanket should be cleaned in time: the ink with dry oxidized conjunctiva adheres to the impression cylinder, and the uneven layout of the rubber during printing will cause the rubber layout to sag, so different After the product of the specifications is printed and when it is handed over every day, the blanket and impression cylinder should be cleaned in time.

2. The tightness of the blanket

If the blanket is stretched too loosely, during imprinting, the blanket will be displaced under the action of squeezing force and cannot be reset in time, which will cause ghosting failure. If it is stretched too tightly, there will be many disadvantages, such as the thinning of the rubber layer and the reduction of elasticity, which will cause uneven printing pressure, affect the synchronous rolling state, and accelerate the creep and aging of the blanket. For the newly changed blanket, due to the stress relaxation of the blanket, it cannot be stretched too tight at once. It should be stretched again after a certain period of pressure printing. After repeated three or four times, the stretch of the blanket can be made longer. Remain stable for a period of time.

3. Torsion deformation of the blanket

During the imprinting process, if the surface of the blanket is subjected to different directions or different magnitudes of force on the surface of the blanket, the shape of the blanket will be twisted and deformed, resulting in the accuracy of overprint transfer of the graphic shape ink and the use of the blanket Adverse effects such as lifespan. In this regard, the first is to adjust the axis of the roller parallel: the second is to standardize the operation when installing the blanket, so that the blanket is inserted into the plate clamp at the same depth, and all the screws clamping the plate clamp should be tightened.

Substrate issues

Paper is the basic raw material used in packaging and printing, and its quality directly affects the quality of printed matter. The characteristics of the paper used are different, and there is a clear difference in its printability. In the printing process, the paper characteristics that affect the printing quality are paper whiteness, ink-absorbing surface smoothness, acidity and alkalinity, paper size stability, and paper surface strength.

Changes in the paper's moisture content will not only cause the paper to swell or shrink, but due to the change in the water content, the paper's local size will change, and other forms of deformation, such as curling and wrinkling, will also occur. For this reason, the paper should be adjusted in humidity before printing (if it is a gravure press, it can be dried with a gravure press). For the paper that has been cut and deformed greatly, the curled paper can be folded in the opposite direction, but the force should be appropriate, and the paper should be flat.

The higher the number of screen lines, the smaller the dots, and the tiny pits on the paper may distort or miss the fine dots. Therefore, for fine prints with a high screen count, the smoothness of the selected paper is high. In actual work, this characteristic of paper can also be adapted by appropriately adjusting certain properties of the ink or changing process parameters.

The influence of the pH value of the paper surface on the gloss of the printed matter cannot be ignored. The high pH value is conducive to the drying of the ink, and thus is conducive to improving the gloss of the printed matter.

Printing press problem

At present, mainstream printing presses are highly intelligent. As long as the operator is familiar with the operating procedures of the printing press and the setting of printing process parameters, and basically understands the internal structure of the printing press, beautiful products can be printed. of course. The age of the aircraft can not be ignored. Generally speaking, it mainly controls the three aspects of water-ink balance, printing pressure and printing speed.

The water-ink balance is a relative balance, not an absolute balance during the high-speed operation of the equipment. According to the actual situation, the viscosity of the ink and the pH value of the fountain solution should be grasped, and the amount of ink and water should be controlled, as long as the printing plate is not pasted or dirty.

If the printing pressure is too low, the ink is not easy to transfer, and the ink trace is light and faint; when the printing pressure is too large, the ink expands to the non-graphic part, which makes the dots increase seriously and the image is distorted. . Therefore, the mechanical pressure must be adjusted correctly. Different amounts of paper require different printing pressures, and only suitable printing pressures can ensure uniform ink color and consistency.

If the printing speed is too fast, it is easy to cause peeling and roughening. Comprehensive factors such as the performance of the substrate, the size of the substrate, and the viscosity of the ink should be considered. When printing substrates with large format, large thickness and low surface strength, the printing speed is lower; the greater the viscosity of the ink, the lower the printing speed. The printing speed is determined based on the complete reproduction of graphics and the highest production efficiency.

For many problems in label printing, if we encounter problems, we will avoid the heavy ones and dare not face them. Our printing quality is difficult to guarantee. Only when we find problems and solve problems can we make better progress in continuous summary. Label printing is the same as what we do. Only one step at a time can we have a better future.