Analysis and Countermeasures of corrugated board w

2022-08-09
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Analysis of the causes of corrugated board warpage and Countermeasures

first, with regard to corrugated board warpage

in today's increasingly detailed social division of labor, important technical parameters and functions of equipment, corrugated board has become a carton factory whose products are sold to later processing, and their requirements for corrugated board warpage are becoming stronger and stronger; In addition, due to social development, the degree of mechanization of carton back processing is getting higher and higher. In order to facilitate mechanical feeding and ensure printing quality, corrugated board is also required to be flat. Therefore, the flatness of corrugated board has become an important indicator to measure the quality of corrugated board

internationally, the warpage degree of paperboard is usually measured based on American or Japanese standards

American standards are as follows: (based on the chord height of the curvature of one meter long corrugated board)

very slight -- less than 5mm

slight --10mm

moderate --15mm

serious --20mm

very serious --30mm

Japanese standards are as follows (the calculation method is the same as above):

they are the requirements for the partition of paperboard. Generally, the maximum allowable warpage for paperboard above 1.2m wide is 20mm; 6mm is the maximum allowable limit below 600mm; The width is 1000mm, and MM is the allowable limit

according to the national standard of China, the warped chord height of one meter long corrugated board is not more than 20mm. In contrast, Japanese standards should be the most reasonable

the warpage of corrugated board can be measured with a special warpage gauge, or the chord height of the side arc of the warped surface of the board can be measured by placing the board on a platform

generally speaking, when the paperboard comes out of the double-sided machine, because the pressure and moisture have not reached the balance, the paperboard is generally flat. With the extension of storage time, the warpage of the paperboard will appear. To judge whether the corrugated board is warped, place the newly produced single board in the air for three minutes to see whether it is warped, and then detect the moisture and temperature of the finished board and the semi-finished products of all classes of the production line according to the specific situation, analyze the causes, and find out the methods to correct the warpage

second, the main causes of corrugated board warpage and its influencing factors

the most fundamental reason for the good stability of corrugated board warpage is the difference in the size of the surface and the inside of the corrugated board. This size change is due to the different water content of the paper on the surface of the corrugated board. In order to achieve water balance after the corrugated board leaves the double-sided machine, the paper with high water content releases water, causing the paper to shrink, The paper with low water content absorbs water, which causes the paper on this side to stretch, resulting in the size difference and the warpage of the paperboard

the factors that cause the above water content changes can be analyzed from the following factors:

(1) the nature, type and moisture content of the lining paper

generally speaking, if the water content of the lining paper is 3% higher than that of the lining paper, 92% of the paperboard is upward warped

if the moisture content of the face paper is 3% higher than that of the inside paper, 75% of the paperboard is down warped

if the moisture distribution in the full width of the base paper is uneven, it is easy to cause S-shaped warpage

in addition, due to the different types of base paper, such as the elasticity of kraft vermicelli and tea paper, due to the difference in fiber composition. Different manufacturing methods vary, and warpage is easy to occur when corrugated board with two grades such as grade A and grade C is combined

if there is a great difference in the quantitative gram weight of the face paper, it is also easy to cause warpage

(2) ambient temperature and tension

the ambient temperature of the workshop also has an impact on the warpage of the paperboard. For example, in summer, because the moisture in the air is higher than that in winter, the paperboard is easy to absorb the moisture in the air in order to achieve water balance in such an environment, resulting in the difference in the size of the paper and causing warpage

the tension of the brake of the paper holder of the outside lining base paper and the tension of the preheater also cause the tendency of the transverse contraction of the paperboard

(3) mechanical equipment and operation

due to the difference in operation, the paper moisture content in the paper board surface is different, resulting in warpage

(4) characteristics of glue and adhesion of glue liquid

the difference of adhesion of glue liquid can cause the difference of water content of paperboard and warpage

III. types of corrugated board warpage

the types of corrugated board warpage are as follows:

(1) longitudinal warpage

(a) longitudinal upward warpage

(b) longitudinal downward warpage

(2) transverse warpage

(a) transverse upward warpage

(b) transverse downward warpage

(3) S-shaped warpage

(a)(4) bidirectional warping

IV Correction methods for different warpage types

although the warpage of corrugated board is inevitable for various reasons, we can control the warpage of corrugated board within the range of standard requirements through the adjustment of operation methods. These adjustments are carried out under certain conditions, that is, on the premise that the glue production process is stable and the base paper has been put into use

(I) lateral warping

control the operation of lateral upward warping:

1 Increase the preheating angle of the lining paper

2. Reduce the preheating angle of the face paper

3. Improve the production and operation speed on the premise of ensuring the quality of paperboard

4. Reduce the gluing amount of single-sided machine

5. Increase the accumulation of single-sided paperboard on the overpass (if possible, increase the blowing device to reduce its water content)

6. Increase the winding degree of single-sided paperboard in the triple preheater, heat the inner paper to reduce warpage, and heat corrugated to facilitate bonding

7. On the premise of no impact on the quality of paperboard, increase the amount of glue on the double gluing machine

8. Under the premise of not affecting the bonding, appropriately reduce the hot plate temperature of the double-sided machine

9. If steam is sprayed on the core paper before adjustment, it should be properly or stopped

10. If the paper in the face is the same, the paper can also be interchanged

11. Spray water mist on the inside paper when leaving the double-sided machine

control the operation of lateral downward warping:

1 Increase the preheating angle of the face paper

2. Reduce the preheating angle of the lining paper

3. Reduce the production speed on the premise of ensuring the quality of paperboard

4. Reduce the accumulation of single-sided paperboard on the overpass

5. Reduce the winding degree of single-sided paperboard in triple preheater

6. On the premise of not affecting the quality of paperboard, reduce the amount of glue on the double gluing machine

7. Increase the tension in the forward direction of the single-sided corrugated board machine

8. The paper inside the surface is interchangeable

9. Spray the lining paper

10. Increase the gluing amount of single-sided machine

11. Reduce the speed appropriately

12. Slowly increase the hot plate temperature of the double-sided machine (by increasing the steam pressure or increasing the number of hot plates through steam)

(II) longitudinal warping

control the operation of longitudinal upward warping:

1 Reduce the drag force that unqualified components at the outlet of the overpass cannot be installed into the system to use the friction plate

2. Check the overpass tube guide plate of the control paper gap

3. If there is too much accumulation on the overpass, the accumulation amount that Professor gangarao plans to carry out on-site test under real working conditions such as towers, lattice structures and water structures on the overpass should be reduced

4. Reduce the friction force of the brake on the preheater

5. Correct the preheater and idler gear to make them rotate freely

6. Use base paper with high tension

control the operation of longitudinal downward warping:

1 Under the condition that the quality of paperboard is not affected, use base paper with low tension

2. Increase the pressure of the cotton ribbon on the paperboard to increase the force of the paperboard on the hot plate

3. Reduce the drag force of preheater brake

4. Increase the drag force of single-sided corrugated board on the overpass

(III) S-shaped warpage

1 The moisture distribution of the base paper is uneven, and the moisture content of each section of the paper can be adjusted by the spray device of the single-sided machine

2. Sometimes due to the long-term use of base paper with different widths, the corrugating roller is worn unevenly

(IV) bidirectional warpage

1 Due to uneven moisture of base paper, the adjustment method is the same as three (1)

2. The transverse tension of the belt is uneven, resulting in uneven tension

3. The base paper holder is not horizontal, and the center line of the paper guide wheel, base paper holder or preheater is not aligned

4. The paper guide frame on the overpass is uneven, incorrect or sideways

5. The glue dispenser or its leveling roller is not level

6. The paper roll in the face is too loose or tight

7. There is uneven or diagonal stress in the base paper roll

the adjustment of two-way warping is relatively complex. Generally, it is first adjusted to one-way (horizontal or vertical) warping, and then adjusted accordingly

v. remedial measures for warped paperboard

1 Press the warped cardboard forward and backward

2. Humidify the storage environment of warped cardboard

3. Apply external mechanical force

in a word, there are many reasons for the warpage of corrugated board. In order to reduce the warpage, only by analyzing the reasons in detail according to the specific situation and carefully adjusting, can we find out the correct correction method

(xubaoqing, Hefei Meiling packaging products Co., Ltd.)

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