In order to attract more attention from consumers, more and more corrugated box manufacturers choose offset printing or pre-printing (flex printing, gravure printing) to make corrugated boxes. However, due to the purchase of "disease" paper, the increase in the rate of rejection of printing equipment, the increase in the rejection rate of corrugated boxes, and the increase in customer complaints have caused the corrugated box manufacturers to pay a terrible price. Then, what are the causes of these paper diseases in the production of corrugated cartons (mainly gray-white board, coated kraft paper, etc.)? 7 What are the reasons for the purchase of these diseases? The impact of the author 7 in the article on the common causes of corrugated paper for a one-on-one analysis, hope to corrugated cartons production enterprises to identify the pros and cons of the procurement of paper to help.
Corrugated paper common disease diagnosis
Symptom 1: Static electricity
cause:
(1) In papermaking process, the content of rosin is too much and the filler such as aluminum sulfate and other electrolytes and kaolin is less. After drying and high-temperature and high-pressure treatment, high-voltage static electricity is generated.
(2) During the printing process, if the paper itself contains less moisture, static electricity may also be generated during the mutual friction.
(3) The paper stacks up in the paper store. And for a short time, the moisture in the paper is too late to reach equilibrium.
(4) The paper temperature (related to the ambient temperature of the paper store) is significantly different from the temperature of the printing shop. Causes the paper to shrink. Produce physical static electricity.
harm:
Paper with static electricity will be difficult to separate, offset printing process will form multiple sheets of paper at the same time into the press. In the web printing due to the same charge repulsion. Drifting of prints, overprinting, or paper feeding difficulties may occur.
In addition, paper with static electricity is also easy to absorb dust and paper dust in the air, making it adhere to the prints and directly polluting the prints. Sparks are generated when static electricity accumulates to a certain intensity. Bury fire hazards. When it's dry in winter. It is especially prone to such accidents.
Symptom 2: Hair loss. Flake
cause:
(1) Improper slurry proportioning or filling may weaken the fiber binding force.
(2) The degree of beating does not meet the requirements.
(3) The paper leaf on the Internet fluctuates widely and the formation is not good.
(4) Pressing roller set pressure is not enough.
(5) Adhesive on the dryer surface.
(6) The temperature in the dryer section is too high.
(7) The paper cutter has dust. The knife is too blunt.
(8) The moisture content of the finished paper product is too low.
harm:
Paper and fillers jam the plate, affecting the normal production of the press.
Symptom 3: Fluctuation in paper ration and uneven quantitation of paper web
The fluctuation of paper quantification includes quantitative fluctuations in the longitudinal direction of the paper and quantitative fluctuations in the paper web direction. These fluctuations can be divided into periodic fluctuations and irregular fluctuations.
The main causes of cyclical fluctuations:
(1) The feed system of the paper stock to the headbox is periodically vibrated.
(2) Vibration of the rotor screen or slurry pump in front of the headbox.
The main reason for irregular fluctuations:
(1) Inappropriate production process or improper operation.
(2) The concentration of raw slurry changes and the slurry concentration fluctuates.
(3) Improper slurrying operation of the beater resulted in poor mixing of the pulp tank.
(4) The air mixed in the slurry resists the paper stock.
(5) The speed of the paper machine has changed.
The uneven quantification of the web direction refers to the quantification inconsistency in the direction of the width of the paper machine, that is, the web half thickness. Half thin or thick. Thin.
main reason:
(1) The paper stock is in the entire width of the headbox. The flow speed at each point is inconsistent.
(2) Uneven lip opening or lip accompanied with defects.
(3) The edger causes folding of web materials.
(4) There is a "ditch beam" in the longitudinal direction of the copper mesh.
harm:
Inhomogeneous web sizing can cause uneven printing pressure, resulting in inconsistent ink reproducibility and dot reversal.
Longitudinal non-uniformity, in addition to the above-mentioned hazards, can also cause the impact between the printing cylinder and the impression cylinder, shortening the mechanical and plate life.
Carton manufacturer when purchasing raw paper. You can use a simple method to check whether the paper is uniform or not: observe whether the paper's wet line is neat. If the wet line is neat, it means that the paper is evenly quantified. If the wet line is severely misaligned, the quantitative change of the paper may be large. Generally, the elongation of the wetline has a higher quantitative value. The area where the wet line is shortened is quantitatively low.
Symptom 4: Dust spot hard block
(1) Dust: refers to the surface exposed to cardboard or paper. Can be seen at any angle, with other parts of a variety of impurities with obvious color differences. Divided into black dust and other dust.
(2) Spot: The difference between spots and dust is not significant. It is mainly due to the inconsistent light and darkness of the paper surface gloss and reflection. According to the characteristics of spots can be divided into wet spots. Cylinder spot. Calendered dark spots, spotted and bubble spots, filler spots, paint spots, bright spots and white spots. Spots on paper have poor ink repellency. Ink does not easily absorb printed colors or the writing is inconsistent with other parts.
(3) Rigid blocks: Rigid blocks refer to the hard and bulky materials that occasionally appear on paper, such as knots of wood, pulp blocks, and raw material blocks. Hard blocks are a great hazard to printing. They can ruin plates and blankets, and even cause serious damage to the press. Once a large hard block appears on the paper, it can cause serious printing problems.
Symptom 5: Poor formation
main reason:
(1) During the beating process, the slurry of the long fibers is insufficiently pulped, cutting is less during the beating process, and the fibers in the fibers are interwoven into a group.
(2) The vibration of the front net box and the net case of the paper machine will also lead to poor formation of the fibres.
(3) During the printing process, the poorly formed paper will cause stress concentration under the tension of the printing machine, especially the curling paper printing machine, resulting in the phenomenon of high paper breakage rate.
An easy way to check for poor formation is to place the paper against a strong light source. Poor formation of paper will appear flocculent.
Symptom 6: Rift
Rifts are cracks or breaks in the middle or edge of the paper. These cracks or broken 1:3 are easily enlarged or broken during the printing process, resulting in breaks and downtime. Influencing production efficiency. Increase paper loss.
Symptom 7: Inconsistent color tone
The phenomenon of inconsistent whiteness and hue appeared in the same batch of paper and even the same color paper.
This phenomenon often occurs in some small and medium-sized papermaking companies. Because the whiteness of the paper is different. There is a clear difference between the depth and depth of printed patterns. Customers are easily rejected.
Symptom 8: Flounce
The lotus leaf is on the edge of the paper. In particular, the paper loses its original straightness in the longitudinal direction. By looking at the side of the paper, it can be easily seen that the side of the paper with the flounces has irregular honeycomb-like pores. When printing on flossed paper. Overprinting will not occur, folds. Fine folding phenomenon. Paper with severe ruffles cannot be printed on the machine. The above 8 kinds of paper diseases are problems that corrugated cartons manufacturing enterprises may encounter during the procurement of raw paper. If you can understand the causes of paper diseases and how to identify them, you can identify them in the procurement process and reduce unnecessary losses.
Source: Print Technology Liu Qing
A blackboard (also known as a chalkboard) is a reusable writing surface on which text or drawings are made with sticks of calcium sulphate or calcium carbonate, known, when used for this purpose, as chalk. Blackboards were originally made of smooth, thin sheets of black or dark grey slate stone.
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The chalk marks can be easily wiped off with a damp cloth, a sponge or a special blackboard eraser usually consisting of a block of wood covered by a felt pad. However, chalk marks made on some types of wet blackboard can be difficult to remove. Blackboard manufacturers often advise that a new or newly resurfaced blackboard be completely covered using the side of a stick of chalk and then that chalk brushed off as normal to prepare it for use.
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