A forming process for solving the problem of board edge cracking of gypsum board

Abstract

The present application relates to the technical field of gypsum board processing, and particularly relates to a forming process for solving the problem of board edge cracking of a gypsum board, which comprises the following steps: pre-spraying and humidifying the lower face paper before it contacts the gypsum slurry; making the humidified lower face paper experience a non-linear paper path under controlled tension, taking the passing time length of the path as the soaking time, and controlling the soaking time to make the lower face paper complete a target pre-expansion determined according to the difference between the upper and lower face paper transverse expansion amounts before it contacts the gypsum slurry; synchronously conveying the lower face paper after pre-expansion and the upper face paper to a forming area, pouring the gypsum slurry, and obtaining the paper-faced gypsum board after vibration exhaust, thickness fixing and curing. The present application completes the pre-expansion before the lower face paper contacts the slurry, so that the transverse expansion amounts of the upper and lower face papers in the curing window are basically matched, and the problem of board edge warping is improved.

Description

Technical Field

[0001] This invention relates to the field of gypsum board processing technology, specifically to a forming process for solving edge cracking of gypsum board. Background Technology

[0002] Paper-faced gypsum board, as a lightweight, fire-resistant, and easy-to-construct building material, is widely used in building partitions, ceilings, and other applications. As the market shifts from commercial to residential applications, the end-user market is placing higher demands on the flatness of gypsum board surfaces. Edge warping and cracking have become significant issues affecting product qualification rates.

[0003] During the gypsum board molding process, the upper and lower facing papers absorb moisture from the gypsum slurry upon contact, causing lateral expansion. Due to differences in the fiber orientation, sizing degree, and other structural characteristics of the upper and lower facing papers, their lateral expansion rates are inconsistent, resulting in warping at the edges of the molded gypsum board and affecting the flatness of the board surface. Currently, the main industry solution is to apply a spray of water to the surface of the upper facing paper during the molding process to alleviate the warping caused by the moisture absorption and expansion of the facing paper. However, this method has strict requirements for the amount of water applied; too little water will not have a remedial effect, while too much water will form grooves on the board surface, leading to product scrap.

[0004] In summary, the existing technology of using spray water to alleviate board edge warping requires high precision in controlling the amount of water applied. In actual production, it is difficult to effectively avoid problems such as board surface cracking or insufficient improvement in warping caused by moisture fluctuations. Summary of the Invention

[0005] The purpose of this invention is to provide a molding process for solving edge cracking of gypsum board, in order to improve the problem in the existing paper-faced gypsum board molding process where the edge warping is caused by the inconsistent lateral expansion rate of the upper and lower facing papers, and the existing water replenishment method has high requirements for water accuracy and large fluctuations in effect.

[0006] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution:

[0007] This invention provides a molding process for solving edge cracking of gypsum board, comprising the following steps: S1, pre-humidification: after the lower facing paper is drawn out by the lower paper guide and before it comes into contact with the gypsum slurry, the lower facing paper is pre-sprayed and humidified; S2, pre-expansion: the humidified lower facing paper is subjected to a non-linear paper path under controlled tension, and the passage time of this paper path is used as the wetting time. The wetting time is controlled so that the lower facing paper completes the target pre-expansion amount determined based on the difference in lateral expansion between the upper and lower facing papers before contacting the gypsum slurry; S3, molding and curing: the pre-expanded lower facing paper and the upper facing paper are simultaneously conveyed to the molding area, and gypsum slurry is poured between the upper and lower facing papers. After vibration and degassing, and curing to a fixed thickness, a paper-faced gypsum board is obtained.

[0008] According to one embodiment of the present invention, before step S1, a pre-adaptation measurement step is further included: A1, sampling: taking samples of the upper and lower facing paper from the current production batch; A2, difference measurement: simulating the actual working conditions of the production line, measuring the difference in lateral expansion of the upper and lower facing papers within the gypsum curing window, and determining the difference as the target pre-expansion amount; A3, wetting time measurement: under the same working conditions, applying the same pre-spray humidification as in step S1 to the lower facing paper, and measuring the shortest wetting time required for the lower facing paper to complete the target pre-expansion amount; A4, parameter matching: determining the total path length required for the non-linear paper path in step S2 based on the paper feeding speed of the production line and the shortest wetting time, so that the passage time matches the shortest wetting time.

[0009] According to one embodiment of the present invention, in step S2, the immersion time is controlled within ±10% of the shortest immersion time by adjusting the total length of the non-linear paper path and / or the paper speed.

[0010] According to one embodiment of the present invention, after step A3, a safety verification step is further included: measuring the wet tensile strength of the lower face paper under the shortest impregnation time, and confirming that the wet tensile strength is greater than the minimum safety strength required for production line traction; if the requirement is not met, the humidification amount of pre-spray is reduced, and the impregnation time is re-measured until both the pre-expansion amount and safety strength requirements are met.

[0011] According to one embodiment of the present invention, ultrasonic atomization spray is used in step S1, with the spray direction facing the non-adhesive gypsum slurry side of the lower protective paper, the atomized particle size is 20-50μm, and the spray pressure is set according to the target pre-expansion amount.

[0012] According to one embodiment of the present invention, in step S2, the target pre-expansion amount of the lower protective paper is 100% completed before the lower protective paper comes into contact with the gypsum slurry, so that the difference in lateral expansion amount between the upper and lower protective papers when they enter the gypsum curing window is less than 0.2%.

[0013] According to one embodiment of the present invention, the pre-adaptation measurement step is re-executed and the corresponding process parameters are updated when any of the following situations occur: the batch of the face paper is changed, or the paper feed speed of the production line is adjusted by more than ±10m / min, or the ambient temperature changes by more than ±5℃, or the ambient relative humidity changes by more than ±15%.

[0014] According to one embodiment of the present invention, in step S2, the non-linear paper feeding path is arranged to fold back and forth in the vertical direction to compress the horizontal length occupied by the lead-out section of the cover paper, while the pouring position of the gypsum slurry is moved forward towards the paper receiving area to increase the effective length of the subsequent forming table.

[0015] According to one embodiment of the present invention, in step A2, the working conditions of the gypsum curing window are a temperature of 40-45°C and a relative humidity of 80%-90%, and the actual working conditions are a temperature of 20-30°C and a relative humidity of 40%-70%.

[0016] According to one embodiment of the present invention, step S2 further includes a tension protection step: during the feeding process of the humidified lower cover paper, the paper tension is monitored in real time; when the tension is detected to exceed the preset safety upper limit, the tension is reduced by shortening the soaking time or reducing the paper feeding speed; when the tension is detected to be lower than the preset safety lower limit, the tension is increased by extending the soaking time or increasing the paper feeding speed, so as to prevent paper breakage or paper surface loosening and deviation.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] This invention pre-sprays and humidifies the lower facing paper before it comes into contact with the gypsum slurry, and then allows it to undergo pre-expansion under controlled tension along a non-linear paper path. The amount of pre-expansion is determined based on the difference in lateral expansion between the upper and lower facing papers, ensuring that the lateral expansion of the upper and lower facing papers is basically matched within the curing window, reducing interlayer stress caused by asynchronous expansion. Unlike existing spray-hydration methods that rely on precise control of the amount of water applied, this invention changes the control of expansion from depending on the real-time accuracy of the spray volume to being determined by the matching of the pre-measured difference in expansion and the immersion time. This reduces the sensitivity of the process effect to the precision of moisture control, improves the problem of edge warping, and reduces the risk of cracking. Attached Figure Description

[0019] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0020] Figure 1 This embodiment provides a schematic diagram of the overall process for forming gypsum board with edge cracks.

[0021] Figure 2 This is a flowchart illustrating the pre-adaptation measurement steps.

[0022] Figure 3 This embodiment provides a schematic diagram of a corresponding optional supporting structure for a molding process that solves edge cracking of gypsum board.

[0023] The labels in the diagram represent the following:

[0024] 100. Lower protective paper; 200. Spraying equipment; 210. Spray volume regulating valve; 300. Roller; 310. Anti-slip layer; 320. Water collection tray; 330. Demisting suction device; 340. Protective cover; 350. Humidity sensor; 360. Dehumidifier; 400. Gypsum slurry mixer; 500. Guide roller; 600. Tension sensor; 700. Controller. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] like Figure 1 As shown in the figure, this specific embodiment provides a molding process for solving edge cracking of gypsum board, including the following steps:

[0027] S1. Pre-humidification: After the lower facing paper is drawn out by the lower paper feeder and before it comes into contact with the gypsum slurry, the lower facing paper is pre-sprayed and humidified;

[0028] S2. Pre-expansion: The humidified lower facing paper is subjected to a non-straight paper path under controlled tension. The duration of this paper path is taken as the immersion time. The immersion time is controlled so that the lower facing paper completes the target pre-expansion amount determined based on the difference in lateral expansion between the upper and lower facing papers before contacting the gypsum slurry.

[0029] S3. Molding and curing: The pre-expanded lower and upper protective papers are simultaneously conveyed to the molding area, and gypsum slurry is poured between the upper and lower protective papers. After vibration to remove air and curing to a fixed thickness, paper-faced gypsum board is obtained.

[0030] Through long-term production tracking and testing, the inventor discovered that there are inherent differences in the moisture absorption and lateral expansion characteristics of the upper and lower facing papers. Due to the asynchronous expansion after contact with gypsum slurry, interlayer internal stress will be generated in the cured board, causing the board edges to warp, and in severe cases, it will develop into cracked boards.

[0031] The technical principles of each step are as follows:

[0032] In step one, after the lower facing paper is pre-sprayed and humidified, the hydrogen bonds between the fibers are partially weakened by water molecules, and the paper enters a reversible wet expansion state. The spray direction is directed towards the side of the non-adhesive gypsum slurry, so that the water only acts on the facing paper itself, reducing interference with the subsequent slurry hydration process.

[0033] In step two, the humidified lower sheath paper undergoes controlled immersion time along a non-linear paper path, allowing the fibers to freely expand laterally under unconstrained conditions. The amount of expansion is matched to the target pre-expansion amount through the immersion time. The target pre-expansion amount is determined based on the difference in lateral expansion between the upper and lower sheath papers. This difference is based on years of production testing data: the saturated lateral expansion characteristics of the lower sheath paper are approximately 1% more stable than those of the upper sheath paper. Pre-expansion before contact with the pulp reduces interlayer stress caused by asynchronous expansion.

[0034] This solution pre-sprays and humidifies the lower facing paper, differing from existing technologies that spray water onto the upper facing paper during the molding process. Before contacting the gypsum slurry, the lower facing paper is dry, and its fibers have sufficient moisture absorption capacity. Sprayed water is evenly absorbed by the fibers and converted into effective lateral expansion. However, when spraying the upper facing paper during molding, it has already expanded due to the moisture in the gypsum slurry, and the fibers' moisture absorption capacity is partially or completely occupied. At this point, additional water is difficult for the fibers to absorb effectively and tends to remain on the paper surface as free water. During the extrusion and traction process on the production line, this free water is crushed and dragged, forming grooves. This solution completes the expansion process before the facing paper contacts the slurry, physically avoiding the problem of free water accumulation caused by fiber saturation.

[0035] In step three, the pre-expanded lower protective paper and the upper protective paper enter the molding area simultaneously. After the gypsum slurry is poured, the expansion of the protective paper in the curing window is basically matched. The internal stress caused by the additional expansion and contraction of the protective paper during the hydration and hardening of the gypsum is reduced. Vibration and air venting allow the air bubbles in the slurry to escape. After the thickness is fixed and cured, the flatness of the board surface is improved.

[0036] When production starts, the lower facing paper is pulled out by the lower paper feeder at a constant speed matched with the linear speed, and passes through the spray zone to complete pre-humidification; then it enters the non-linear paper path and completes impregnation and pre-expansion for a set passage time; the pre-expanded lower facing paper and upper facing paper are synchronously transported to the forming area, and the gypsum slurry mixer evenly pours the slurry between the two papers, and the initial forming is completed by the vibration exhaust and extrusion thickness fixation of the forming table.

[0037] According to the inventor's production tracking and testing, the adoption of this method has improved the surface cracking defect rate and reduced the risk of edge cracking. Pre-expansion is completed under unconstrained conditions of the facing paper, which reduces the probability of warping compared to existing mechanical straightening methods that address the problem after the fact.

[0038] like Figure 2 As shown, based on the previous scheme, in order to achieve accurate matching of pre-expansion amount for different batches of face paper and different working conditions, this embodiment designs the preparation steps before pre-humidification as follows:

[0039] Before step S1, a pre-fit determination step is also included:

[0040] A1. Sampling: Take samples of the top and bottom facing paper from the current production batch. When sampling, take samples from the outer, middle, and inner layers of the facing paper roll to ensure that the test results are representative.

[0041] A2. Difference Measurement: Simulating the actual working conditions of the production line, the difference in lateral expansion between the upper and lower facing papers within the gypsum curing window is measured, and this difference is determined as the target pre-expansion amount. The sample is first placed in a static environment consistent with the real-time environment of the production line workshop to reach equilibrium, and then transferred to the environment simulating the gypsum curing window for testing. The lateral expansion change curves of the upper and lower facing papers are recorded, and the stable difference between the two is taken as the target pre-expansion amount.

[0042] A3. Wetting Time Measurement: Under the same operating conditions, apply the same pre-spray humidification as in step S1 to the lower facing paper, and measure the shortest wetting time required for the lower facing paper to achieve the target pre-expansion amount. The humidification conditions are consistent with the actual spray parameters of the production line to reduce the condition deviation between the laboratory and the production line.

[0043] A4. Parameter Matching: Based on the paper feed speed and minimum wetting time of the production line, determine the total path length required for the non-linear paper feed path in step S2, so that the transit time matches the minimum wetting time. The total path length is determined by multiplying the production line speed by the minimum wetting time.

[0044] After the pre-adaptation measurement is completed, the obtained total path length parameter is used as the basis for setting the non-linear paper feeding path in step S2, and then production is carried out according to steps S1 to S3. Through the pre-calibration of parameters, the impact of differences in the expansion characteristics of different batches of face paper and fluctuations in workshop conditions on the pre-expansion effect is improved, and the matching degree between process parameters and the current production scenario is improved.

[0045] Based on the aforementioned effects, in order to further improve the consistency of the pre-expansion effect during continuous production, this embodiment designs the control range of the immersion time as follows:

[0046] In step S2, the impregnation time is controlled within ±10% of the minimum impregnation time by adjusting the total length of the non-linear paper path and / or the paper feed speed. The production line control system collects the operating line speed in real time and calculates the actual impregnation time of the face paper in the non-linear paper path. When the actual impregnation time exceeds the set range, the system adjusts the total length of the paper path or adjusts the paper feed speed to bring the impregnation time back to the set range. This ±10% range can prevent insufficient pre-expansion due to an excessively short impregnation time, and can also prevent excessive water absorption and decreased wet strength of the face paper due to an excessively long impregnation time.

[0047] Building upon the aforementioned effects, to resolve the conflict between the decrease in wet strength of the face paper after pre-humidification and the safety of continuous production, this embodiment adds a safety verification step:

[0048] Following step A3, a safety verification step is also included: measuring the wet tensile strength of the face paper under the shortest impregnation time to confirm that the wet tensile strength is greater than the minimum safety strength required for production line traction; if the requirements are not met, the humidification amount of the pre-spray is reduced, and the impregnation time is re-measured until both the pre-expansion amount and safety strength requirements are met simultaneously. The adjustment range of the humidification amount is limited to not causing the pre-expansion amount deviation to exceed the allowable range.

[0049] By verifying the wet tensile strength in advance, the risk of paper breakage caused by pursuing expansion targets is reduced, and the pre-humidification process can be safely implemented on a continuous production line.

[0050] Based on the pre-humidification function already implemented in the previous scheme, in order to ensure uniform humidification across the entire width and reduce the interference of water on the slurry, this embodiment has made the following design to the spraying method:

[0051] In step S1, ultrasonic atomization spraying is used, with the spray direction directly facing the non-adhesive gypsum slurry side of the facing paper. The spray pressure is set according to the target pre-expansion amount. Ultrasonic atomization can generate uniform micron-sized water particles, allowing water to adhere evenly to the surface of the facing paper and reducing local water accumulation. The spray direction is directly facing the non-adhesive surface, ensuring the water acts on the facing paper itself, reducing the possibility of it seeping into the subsequent gypsum slurry and interfering with the hydration process. The spray pressure is positively correlated with the target pre-expansion amount; adjusting the pressure changes the spray volume per unit time without needing to replace or adjust the nozzle.

[0052] Building upon the aforementioned effects, to further reduce interlayer stress, this embodiment limits the timing of pre-expansion completion and the difference in expansion amount within the curing window:

[0053] In step S2, the target pre-expansion amount of the lower facing paper is 100% completed before the lower facing paper contacts the gypsum slurry, ensuring that the difference in lateral expansion between the upper and lower facing papers when they enter the gypsum curing window is less than 0.2%. The completion point for pre-expansion is before the lower facing paper enters the pouring area of ​​the gypsum slurry mixer. When the difference is controlled within 0.2%, the influence of interlayer internal stress caused by the asynchronous expansion and contraction of the facing paper during curing on the flatness of the board surface can be ignored.

[0054] Building upon the aforementioned effects, to achieve continuous matching between process parameters and operating conditions throughout the entire production cycle, this embodiment adds a parameter retesting mechanism when operating conditions change:

[0055] If any of the following situations occur, the pre-adaptation measurement steps should be repeated to update the corresponding process parameters: changing the cover paper batch, adjusting the paper feed speed of the production line by more than ±10m / min, changing the ambient temperature by more than ±5℃, or changing the ambient relative humidity by more than ±15%. If the cover paper batch is changed, the pre-adaptation measurement and parameter update must be completed before the new paper roll is put into service, so that the process parameters are already matched when the new paper roll is put into service.

[0056] Based on the pre-expansion function already implemented in the previous scheme, in order to reduce the occupation of horizontal space while taking into account the need for optimization of the forming table length, this embodiment has made the following design for the spatial arrangement of the non-linear paper feeding path:

[0057] In step S2, the non-linear paper path is arranged in a reciprocating pattern in the vertical direction to reduce the horizontal length occupied by the facing paper lead-out section. Simultaneously, the pouring position of the gypsum slurry is moved forward towards the paper receiving area to increase the effective length of the subsequent forming platform. As the gypsum slurry mixer moves forward with the pouring position, the effective length of the forming platform increases accordingly, allowing large air bubbles in the slurry more sufficient vibration and degassing time before entering the extrusion plate, thus improving the uniformity of the core cell structure.

[0058] Based on the aforementioned effects, in order to clarify the specific parameter range of the simulated working conditions in the pre-adaptation measurement, this embodiment makes the following limitations:

[0059] In step A2, the conditions at the gypsum curing window are a temperature of 40-45℃ and a relative humidity of 80%-90%, while the actual conditions are a temperature of 20-30℃ and a relative humidity of 40%-70%. The temperature and humidity at the gypsum curing window simulate the exothermic and moisture evaporation environment during the gypsum hydration and hardening process, while the actual conditions are consistent with the conventional environmental parameters of a gypsum board production workshop. The samples are allowed to stand under actual conditions until equilibrium is reached before being tested at the curing window, ensuring that the measurement results correspond to the actual conditions on the production line.

[0060] Building upon the aforementioned effects, to reduce the risk of paper breakage or paper slippage due to tension fluctuations during continuous production, this embodiment adds a tension protection step:

[0061] Step S2 also includes a tension protection step: during the feeding process of the humidified lower liner paper, the paper tension is monitored in real time; when the tension exceeds the preset safety upper limit, the tension is reduced by shortening the wetting time or decreasing the paper feeding speed; when the tension is below the preset safety lower limit, the tension is increased by extending the wetting time or increasing the paper feeding speed to prevent paper breakage or paper loosening and deviation. Tension monitoring points are set at the bends in the non-straight paper feeding path, where tension accumulation is more significant. Through the linkage adjustment of tension and wetting time, the wet strength of the liner paper is ensured to meet the safety requirements of continuous production, while ensuring that the pre-expansion amount meets the standard.

[0062] The following describes the specific implementation of a non-linear paper path through optional embodiments, which do not limit the scope of protection of the present invention.

[0063] Non-linear paper feeding paths can be achieved by adding a multi-roller folding paper feeding mechanism. Each roll surface is treated with an anti-slip coating to increase the coefficient of friction between the roll surface and the humidified lower facing paper, suppressing slippage of the wet paper in the folding path due to decreased wet strength. The distance between the rolls is adjustable, and the wetting time is adjusted by changing the total paper feeding length. This folding paper feeding mechanism uses a vertical, up-and-down arrangement, typically with 6-8 rows of rolls at each end, with an overall installation height of approximately 1.5 meters, increasing the paper feeding distance by 20-30 meters.

[0064] like Figure 3 As shown, this embodiment also provides a pretreatment conveying device for realizing a non-linear paper feeding path in the above-mentioned molding process. The device includes a spraying device 200 and a folding paper feeding mechanism arranged sequentially along the feeding direction of the lower cover paper 100. The spraying device 200 is equipped with a spray volume regulating valve 210 for regulating the spray volume per unit time. The folding paper feeding mechanism includes multiple rollers 300 arranged in an alternating pattern to form an S-shaped folding paper feeding path. The surface of the rollers 300 is covered with an anti-slip layer 310, and a water collection tray 320 and a demisting suction device 330 are provided below the rollers 300. The folding paper feeding mechanism is enclosed within a protective cover 340, which contains a humidity sensor 350 and a dehumidifier 360. A tension sensor 600 is also provided on the paper feeding path and is connected to a controller 700. The discharge end of the folding paper feeding mechanism is aligned with the inlet of the downstream gypsum slurry mixer 400 after being calibrated by a guide roller 500.

[0065] During operation, the lower facing paper 100 is first pre-humidified by the spraying equipment 200 after being drawn out, and then enters the folding paper feeding mechanism. It undergoes pre-expansion in an S-shaped path formed by multiple rollers 300. During this process, the anti-slip layer 310 inhibits slippage of the wet paper, the water collection tray 320 and the demisting suction device 330 handle condensed water mist, and the protective cover 340, in conjunction with the humidity sensor 350 and the dehumidifier 360, controls the ambient humidity. The controller 700 adjusts the rotation speed and / or spacing of the rollers 300 based on the signal from the tension sensor 600 to maintain stable tension. After pre-expansion, the lower facing paper 100 is calibrated by the guide roller 500 and then fed into the gypsum slurry mixer 400 for subsequent forming.

[0066] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within its spirit and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of the present invention.

Claims

1. A molding process for solving edge cracking of gypsum board, characterized in that, Includes the following steps: S1. Pre-humidification: After the lower facing paper is drawn out by the lower paper feeder and before it comes into contact with the gypsum slurry, the lower facing paper is pre-sprayed and humidified; S2. Pre-expansion: The humidified lower facing paper is subjected to a non-straight paper path under controlled tension. The duration of this paper path is taken as the immersion time. The immersion time is controlled so that the lower facing paper completes the target pre-expansion amount determined based on the difference in lateral expansion between the upper and lower facing papers before contacting the gypsum slurry. S3. Molding and curing: The pre-expanded lower and upper protective papers are simultaneously conveyed to the molding area, and gypsum slurry is poured between the upper and lower protective papers. After vibration to remove air and curing to a fixed thickness, paper-faced gypsum board is obtained.

2. The molding process according to claim 1, characterized in that, Before step S1, a pre-fit determination step is also included: A1. Sampling: Take samples of the top and bottom facing paper from the current production batch; A2. Difference Measurement: Simulate the actual working conditions of the production line, measure the difference in lateral expansion of the upper and lower protective papers within the gypsum curing window, and determine this difference as the target pre-expansion amount; A3. Wetting time determination: Under the same working conditions, apply the same pre-spray humidification as in step S1 to the lower face paper, and determine the shortest wetting time required for the lower face paper to complete the target pre-expansion amount. A4. Parameter matching: Based on the paper feeding speed of the production line and the minimum wetting time, determine the total path length required for the non-linear paper feeding path in step S2, so that the transit time matches the minimum wetting time.

3. The molding process according to claim 2, characterized in that, In step S2, the wetting time is controlled within ±10% of the shortest wetting time by adjusting the total length of the non-linear paper path and / or the paper speed.

4. The molding process according to claim 2, characterized in that, Following step A3, a safety verification step is also included: measuring the wet tensile strength of the lower face paper under the shortest impregnation time, and confirming that the wet tensile strength is greater than the minimum safety strength required for production line traction; if the requirements are not met, the humidification amount of the pre-spray is reduced, and the impregnation time is re-measured until both the pre-expansion amount and safety strength requirements are met simultaneously.

5. The molding process according to claim 1, characterized in that, In step S1, ultrasonic atomization spray is used, with the spray direction facing the non-adhesive gypsum slurry side of the lower protective paper. The atomized particle size is 20-50μm, and the spray pressure is set according to the target pre-expansion amount.

6. The molding process according to claim 1, characterized in that, In step S2, the target pre-expansion amount of the lower protective paper is 100% completed before the lower protective paper comes into contact with the gypsum slurry, so that the difference in lateral expansion amount between the upper and lower protective papers when they enter the gypsum curing window is less than 0.2%.

7. The molding process according to claim 2, characterized in that, If any of the following situations occur, the pre-adaptation measurement step shall be repeated and the corresponding process parameters updated: the batch of face paper is changed, or the paper feed speed of the production line is adjusted by more than ±10m / min, or the ambient temperature changes by more than ±5℃, or the ambient relative humidity changes by more than ±15%.

8. The molding process according to claim 1, characterized in that, In step S2, the non-linear paper feeding path is arranged to fold back and forth in the vertical direction to compress the horizontal length occupied by the lead-out section of the cover paper, while the pouring position of the gypsum slurry is moved forward towards the paper receiving area to increase the effective length of the subsequent forming table.

9. The molding process according to claim 2, characterized in that, In step A2, the working conditions of the gypsum curing window are a temperature of 40-45℃ and a relative humidity of 80%-90%, while the actual working conditions are a temperature of 20-30℃ and a relative humidity of 40%-70%.

10. The molding process according to claim 1, characterized in that, Step S2 also includes a tension protection step: during the feeding process of the humidified lower cover paper, the paper tension is monitored in real time; when the tension is detected to exceed the preset safety upper limit, the tension is reduced by shortening the soaking time or reducing the paper feeding speed; when the tension is detected to be lower than the preset safety lower limit, the tension is increased by extending the soaking time or increasing the paper feeding speed to prevent paper breakage or paper loosening and deviation.

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