1、 The poor adhesion between the face paper and the gypsum core results in the problem that the board core is exposed or the paper is not adhered locally. This kind of problem is related to the production process of face protection paper, raw material quality and drying. First of all, the paper's gas injection of the greyer value is too low, water absorption is too high or too low, are easy to cause rapid loss of water, and lead to bad bonding; second, the grade of gypsum in raw materials is too low, impurities or K, Na and other harmful impurities content is too high, affect the paper and gypsum core bonding. Thirdly, the setting time of building gypsum is too slow, and it can not be completely solidified or has false coagulation before entering the drying area, which leads to the incomplete hydration of building gypsum, thus making the dried board out of paper. Fourth, the molding and drying speed can not be adjusted in time with the fluctuation of the face paper or slurry, resulting in the incompatibility between the air permeability and water absorption of the face paper and the drying speed, and the incompatibility between the setting time of the gypsum slurry and the molding speed, resulting in the non bonding between the paper and the gypsum core or the over burning of the board. Fifth, too thin slurry, uneven foam, too large or too concentrated after drying, will cause poor bonding of paper and core. 2、 The surface of the board is wavy and uneven. This kind of problem is related to the paper index, process control and so on. First, the paper factor. The quantity and moisture content of the paper are not uniform, and the air permeability is not uniform, so that the tightness and thickness of the paper are different, and the water absorption is different. In the place with large moisture content, the moisture expansion is small, and in the place with small moisture content, the moisture expansion is large, and the shrinkage is serious in the drying area, while in the place with small moisture content, the dry shrinkage is small, which causes the paper expansion and shrinkage inconsistency, and causes corrugation or raveling. Second, the problem of process equipment. If the flatness of the forming platform is not enough or the adjustment is not in place, the uneven surface can also be caused. The problems caused by this kind of reason are more concentrated and easy to find, but the improvement of the flatness of the plate must be realized through the improvement of the process equipment. Thirdly, the fluctuation of material properties and slurry is also one of the important reasons for uneven board surface. Due to the fluctuation of raw materials and additional materials, as well as the fluctuation caused by the milling process, it is inevitable that the setting time, weight rise and other indicators of powder and slurry will change to a certain extent. However, if the fluctuation is too frequent or large, it will make it difficult for the subsequent process to adjust and control in time, and it can also cause adverse phenomena such as plate groove. 3、 The phenomenon of paper take-up on the surface of the board. The paper take-up on the surface of the board affects not only the appearance quality of the board, but also the strength of the board and other internal quality indicators to a certain extent, which can not be ignored. The main influencing factor of paper take-up on the surface of sheet is face paper. In the process of forming water absorption, the interlayer bonding force of the paper will be further reduced. In the process of relative movement between the plate and the equipment, the paper take-up phenomenon will occur due to mutual friction. In serious cases, the paper ball produced by the paper take-up will scratch the surface of the plate and cause serious quality problems such as easy fracture. Therefore, in the production process of gypsum board, the paper with stable moisture and water absorption should be selected as much as possible. 4、 Low strength, easy to break and crack. The main reason for the broken sheet is transverse fracture, and the longitudinal strength of the paper should be considered. At present, with the development and competition of gypsum board and face paper industry, the weight of face paper is reduced from 230g / m2 ~ 250G / m2 to 180g / m2 ~ 210g / m2, which inevitably leads to the decrease of strength and other indicators. Gypsum as the main raw material of gypsum board, its grade and physical properties are another important factor affecting the strength of gypsum board. For natural gypsum, it is generally required that its grade is not less than 75%, and the 2-hour flexural strength of building gypsum is not less than 1.8 MPa, which is the minimum basic requirement to ensure the strength of gypsum board. In addition, the impurities and acid-base properties of gypsum will also have adverse effects on the strength of gypsum. In the production of gypsum board, glass fiber is often used as reinforcing material to improve the strength of the board. Therefore, if the reinforcing fiber is not enough, the strength of the board will be reduced and the board will be easily broken. At the same time, if the material of the reinforcing fiber can not meet the requirements, its reinforcing effect will be greatly reduced, It has a certain flexibility and high strength, if the use of alkali, or even high alkali fiber, because of the alkali fiber material brittle, low strength can not play the role of reinforcement, resulting in brittle plate. In the production process, if there are hard particles such as rust, sand left on the board, in the relative movement of the board, it is very easy to scratch on the surface of the protective paper of the board, which makes the board easy to break along the scratch. This problem generally does not occur in large quantities, and is easy to be found and removed by careful observation. In addition to the low transverse strength and gypsum strength, another important reason is the edge warping of the board, which makes the board crack at the stress concentration when it is pressed in the process of storage and transportation. There are many reasons for the edge warping of the board, such as the large expansion rate of the face paper or the inconsistent shrinkage rate of the upper and lower paper; If the slurry is too thin or the material property is unstable, the process control is unstable and the operability is poor, which will lead to the plate edge warping. Therefore, in order to improve the strength of the board and reduce the problems such as breakage and cracking, we should try our best to select the protective paper and high-grade gypsum with the strength, gasability and water content suitable for the production requirements, and strictly control the indexes of powder processing and molding process. 5、 The problem of air bubbling and bubbling on the surface of plate. The foaming and bulging on the surface of gypsum board are mainly caused by too thin slurry or improper use of foaming agent in production, poor airing performance of face protection paper, etc. Sometimes the diameter of bubbles is less than 1cm, but almost all over the board. This is mainly because gypsum slurry is too thin or foaming agent has poor foam stability and large bubbles, so that a large number of bubbles are concentrated on the surface to form large bubbles, especially for a period of time. Some bubbles are larger, sometimes more regular, such as a straight line along the edge; some bubbles are less, and it is difficult to determine their regularity, which is related to the low and uneven air injection performance and low interlayer adhesion of face paper. Due to the low permeability of paper, the moisture in the paper is not easy to evaporate, and the interlayer adhesion of the face paper is low. During the production or storage process, there are local poor adhesion or paper delamination, which leads to the bulging of the surface of the board, and the serious performance is large area non adhesion. 6、 The plate is easy to deform. With the development and competition of gypsum board industry and related industries, the unit quality of face paper and gypsum board has been reduced to a certain extent. First of all, the quantitative reduction of the face paper, the paper shrinkage rate is too large, which makes the tightness of the face paper is not enough, resulting in the stiffness of the gypsum board is not enough, after moisture absorption, the machine is easy to deform; second, if the air permeability of the face paper is low, the air permeability is slow, and the drying is slow, the deflection of the dried board after moisture absorption is large; in addition, in the molding process, such as depending on the water consumption to adjust the slurry consistency, so that When the water consumption is large, large voids will appear in the plate after drying and evaporation. The plate is too light or soft, and the deformation and deflection will increase. 7、 Production process interruption