Paper uniformity, paper forming, these seemingly simple and practical are the most important and basic factors in the nature of paper. Let's take a look with the editor.
1. If the dewatering capacity of the forming screen is allowed, reduce the concentration of the headbox
2. If other aspects of paper quality permit:
(A) Change the paper stock to shorter fibers
ï¼For coated base paper or low double glue, use more hardwood
ï¼For grinding wood pulp paper, reduce the freeness of grinding wood pulp, or increase the quantity of grinding wood pulp
(B) If appropriate, increase beating
-Controllable shut-off is better than excessive hydration
3. Operate under the most ideal net tension
ï¼Do not let the forming wire sag on the dewatering element or loosen at the breast roller
ï¼Don't let the net change direction drastically in the forming plate and case roller area
4. Use the following methods to improve the dehydration capacity of the online case:
(A) Move the vacuum box to the direction of the roll, and add more dehydration elements
(B) Add a chopping board or preferably a humidified vacuum box
(C) Install vacuum box with low friction coefficient
ï¼In this way, the forming wire can be operated in a tighter way at the breast roller, and in addition to the dehydration of the wire at the vacuum box, the previous part can also fully exert the dehydration function.
(D) If the stability of the slurry on the forming net permits, the angle of the chopping board can be increased, and the vacuum degree of the wet vacuum box can be increased.
(E) Reduce initial dehydration to avoid paste net
5. The setting of the forming net can be improved in the following ways:
(A) Correctly set the distance between the previous roller and the baffle so that there is no large water flow between them
(B) All baffles are properly positioned for the forming wire so that no water passes through the baffles to form a water flow
(C) Confirm that all dehydration elements are aligned
ï¼The chopping board should make its tip contact with the forming net correctly
ï¼This means that all chopping boards must be ground simultaneously
(D) All rollers rotate freely
6. For the existing headbox, always maintain the best quantitative distribution
7. Lip slurry discharge should be as uniform and even as possible
-Try to avoid flocculation
8. Set the pulp speed to speed ratio to the best state
ï¼Actually use the meter to read the value
ï¼For advanced paper machines, this value is automatically controlled
9. The following states are better:
-Upper lip
-Lower lip
ï¼Forming plate
ï¼Breast roller relationship
ï¼The lower part of the slurry sprayed from the lip plate should fall on an important part of the forming plate
ï¼Avoid backflow of forming plates
ï¼Except for special circumstances, avoid slurry discharge at the breast roller
10. Under special circumstances, serious effects that must cause vigilance are observed: chest roller pulping may be beneficial because the first 15 ~ 20% of the paper sheet has been formed to avoid large bright spots
ï¼When the slurry distribution in the headbox is not good, it is beneficial to make the slurry on the net lean towards the back of the net case
11. Avoid forming board pulping
ï¼The forming head is slightly lower
ï¼Working experience is that the speed is 5 mm lower per 1000 meters / minute, so that the forming net can avoid a rapid upward acceleration when forming the forming plate
12. The impact of the slurry on the net should not cause damage
13. Check the homogenizing roller:
(A) Ensure that the design of the lip homogenizing roller does not cause fibers to gather under the headbox and cause flocculation
(B) Avoid hanging fibers at the homogenizing roller
(C) The lip homogenizing roller can be modified as follows:
ï¼Keep the opening rate of 48%, the pore size should be as small as possible under the condition of slurry permission
ï¼If the reason for poor forming is that the hole is too small, increase the hole (by increasing the thickness of the blind face)
-For long fibers and slurries with an average concentration of 0.4 to 0.6%, the opening ratio is changed to 43 to 44% to obtain a blind area of ​​sufficient area and the hole size required by the fiber type
ï¼Ensure that the design of the end of the homogenizing roller and the shaft shoulder do not affect the edge of the web
ï¼Check that the interlacing of the solid parts of the homogenizing roller will not cause the paper strip marks
14. Make sure there is enough microturbulence on the Internet, especially in the paper forming stage
ï¼This can ensure proper flocculation and better forming
15. Removal of one or more dehydration elements to cause delayed dehydration can disrupt the formation.
16. There is always a compromise between dehydration speed and forming.
17. Running watermark roller
ï¼3 ~ 5 meters faster than internet speed
ï¼Special structure for higher speed rollers
ï¼The watermark roller also rotates when not in use
ï¼Always have a spare watermark roller for replacement in case of damage.
18. If a shaking device is used and the shaking speed does not meet the effective requirements:
(A) Increase shaking energy
ï¼The effectiveness of shaking is basically proportional to the square of the vibration frequency and the amplitude
ï¼Mechanical limitation of the forming section can prevent this
(B) If the structure of the forming section is suitable for low-speed paper machines, you can use the cross bar to extend the shaking further behind the wire and achieve good results
19. Quantify forming effect with forming detector
ï¼Ensure that there is no excessive forming change in the horizontal direction
20. Using speed forming (slightly pulled back), the angle of the first case is slightly smaller to improve the retention on the first trip
twenty one. Reduce the dehydration capacity at this point
ï¼If the paper sheet is formed too fast, you need to increase the angle of the chopping board to improve the role of the net
twenty two. Consider using forming nozzles to increase turbulence in the early stages of dehydration
twenty three. If the wet-end chemicals cause flocculation, the online slurry activity and beating will be more necessary
ï¼It is better to improve the addition of wet end chemicals
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