Coating die head for closed-loop control and control method

Abstract

The invention relates to a coating die head for closed-loop control and a control method, which belong to the technical field of coating, and are characterized in that on the basis of dry film detection, a wet film thickness gauge is further adopted to measure surface density distribution data of a coating which is just output by the coating die head and is not dried. In this way, quick pre-control adjustment can be achieved before closed-loop adjustment of the dry film. And secondly, the structure of the lower die is improved, and the choked flow block and the driving motor for controlling the choked flow block to move are arranged at the bottom of the lower die, so that double-layer fine adjustment of the coating die head is realized, and through the design, the thickness and distribution of the coating can be more accurately controlled, and the coating quality is improved. In addition, the coating die head can adapt to coatings of different types and viscosities, and has good universality and flexibility. In practical application, the coating die head can remarkably improve production efficiency, reduce material waste and save cost.

Description

Technical Field

[0001] The invention relates to the technical field of coating, and in particular to a coating die head for closed-loop control and a control method. Background Art

[0002] With the development of the times, new energy technology has gradually grown and become the focus of attention in all walks of life. In the development of new energy, lithium batteries have become the key to promoting the advancement of new energy technology due to their high energy density and long life. Among them, the slit coating die head achieves a high-precision and high-efficiency coating process by accurately controlling the flow, pressure and gap size of the coating liquid. As a result, it has been widely used in the lithium battery field.

[0003] At present, the closed-loop control die head mainly performs dry film closed-loop according to the dried film after baking, which has the problems of time lag and slow closed-loop adjustment speed; and the current double-layer coating often only adjusts the upper baffle block to achieve closed-loop adjustment, while ignoring the coating of the lower layer. Although this closed-loop adjustment method can adjust the overall surface density, it cannot achieve fine adjustment of the upper and lower layers, which has a serious impact on the coating quality. Therefore, the present invention proposes a coating die head and control method for closed-loop control. Summary of the invention

[0004] The present invention provides a coating die head for closed-loop control and a control method thereof to solve the problems mentioned in the above background technology.

[0005] The object of the present invention is achieved in the following ways:

[0006] A coating die head for closed-loop control comprises an upper die and a lower die, a discharge slot communicating with the outside being arranged between the upper die and the lower die, a plurality of adjustment components for cooperating with the discharge slot being arranged on the upper die, the plurality of adjustment components being arranged in sequence along the longitudinal extension direction of the discharge slot, the adjustment components comprising a driving motor and a baffle block, a positioning groove for accommodating the baffle block being arranged in the discharge slot, and the driving motor drives the baffle block to move up and down along the positioning groove through a coupling.

[0007] Furthermore, a middle die is arranged between the upper die and the lower die, and discharge slots are formed between the upper die and the middle die and between the middle die and the lower die respectively, and forming gaskets are arranged in the discharge slots.

[0008] Furthermore, the discharge slot is provided with a first slow flow cavity and a second slow flow cavity in sequence from the inside to the outside, and the volume of the first slow flow cavity is greater than the volume of the second slow flow cavity.

[0009] Furthermore, the baffle block is provided with a connecting shaft for connecting with the coupling, and the connecting shaft is sequentially sleeved with a plurality of sealing rings from top to bottom.

[0010] Furthermore, the baffle blocks are tightly embedded in the positioning grooves, and two adjacent baffle blocks are tightly fitted to each other, so that the positioning grooves are sealed.

[0011] Furthermore, a lip for connecting with the outside is embedded outside the discharge slot, and the upper die, middle die, lower die and lip are all made of ceramic or glass materials.

[0012] A control method for a coating die head for closed-loop control, the method is used to control the coating die head, the method comprising the following steps:

[0013] Step 1, using a wet film thickness gauge arranged at the output end of the coating die head to measure the thickness distribution data of the double-layer coating in an undried state;

[0014] Step 2, dividing the thickness distribution data of the double-layer coating into regions along the longitudinal extension direction of the discharge slot, each of the regions corresponding to one or more sequentially arranged flow blocks;

[0015] Step 3: When the wet film thickness gauge measures that the coating thickness of one of the areas is different from the set standard, the coating thickness of the area is increased or decreased by adjusting the lifting amount of the baffle block corresponding to the area.

[0016] Furthermore, the wet film thickness gauge in step 3 needs to calculate the average thickness of the coating in the abnormal area, and the coating die head adjusts the lifting amount of the baffle block according to the average thickness of the coating in the abnormal area.

[0017] Furthermore, it also includes:

[0018] Step 4: After the coating die head has completed a certain amount of coating operation, the flow blocking blocks of the upper die and the lower die need to be benchmarked. The steps of benchmarking are as follows:

[0019] The discharge slots of the upper die and the lower die sequentially output a single layer of coating, and the wet film thickness gauge measures the thickness of the two single layers of coating respectively to determine whether the thickness of the single layer of coating output by the upper die and the lower die meets the set standard. If the thickness of the single layer of coating output by the upper die or the lower die does not meet the set standard, the lifting amount of the baffle block in the corresponding area is adjusted to meet the set standard.

[0020] Step 5, setting the lifting amount of the baffle blocks of the upper and lower molds that meet the set standards as the benchmark, and starting the next round of coating operation. During the coating operation, the thickness of the double-layer coating is divided into areas for measurement using steps 1-2. When the wet film thickness gauge measures that the coating thickness of one of the areas is different from the set standard, the lifting amount of the baffle blocks of the upper and lower molds corresponding to the area is synchronously adjusted to increase or decrease the coating thickness of the area.

[0021] Furthermore, it also includes:

[0022] Step 4: After the coating die head has completed a certain amount of coating operation, the flow blocking blocks of the upper die and the lower die need to be benchmarked. The steps of benchmarking are as follows:

[0023] The discharge slots of the upper die and the lower die stop outputting the coating to the outside in turn, so that a single layer of coating is formed at the end of the product which is only output by the discharge slot of the lower die, and the wet film thickness gauge measures the thickness of the single layer of coating to obtain the thickness distribution data of the single layer of coating, and adjusts the lifting amount of the flow block of the upper die and the lower die according to the thickness distribution data to meet the set standard;

[0024] Step 5, setting the lifting amount of the baffle blocks of the upper and lower molds that meet the set standards as the benchmark, and starting the next round of coating operation. During the coating operation, the thickness of the double-layer coating is divided into areas for measurement using steps 1-2. When the wet film thickness gauge measures that the coating thickness of one of the areas is different from the set standard, the lifting amount of the baffle blocks of the upper and lower molds corresponding to the area is synchronously adjusted to increase or decrease the coating thickness of the area.

[0025] On the basis of dry film detection, the present invention further uses a wet film thickness gauge to measure the surface density distribution data of the coating just output and not dried by the coating die head. This enables us to achieve rapid pre-control adjustment before the dry film closed-loop adjustment. Secondly, the present invention also improves the structure of the lower die, arranges the baffle block and the drive motor that controls the movement of the baffle block at the bottom of the lower die, thereby achieving double-layer fine adjustment of the coating die head. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of a coating die head for closed-loop control of the present invention;

[0027] Figure 2 It is a first partial exploded schematic diagram of a coating die head for closed-loop control of the present invention;

[0028] Figure 3 A second partial exploded schematic diagram of a coating die head for closed-loop control according to the present invention;

[0029] Figure 4 A third partial exploded schematic diagram of a coating die head for closed-loop control according to the present invention;

[0030] Figure 5 A cross-sectional view of a coating die head for closed-loop control according to the present invention;

[0031] Figure 6 for Figure 5 A is an enlarged schematic diagram;

[0032] The reference numerals in the figure are: 1-coating die head, 101-discharge slit, 102-positioning groove, 103-first slow flow cavity, 104-second slow flow cavity, 2-upper die, 3-middle die, 4-lower die, 5-lip, 6-adjustment component, 61-drive motor, 62-blocking block, 621-connecting shaft, 63-sealing ring, 64-coupling. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0034] In this embodiment, refer to Figure 1-Figure 6 A coating die head for closed-loop control is specifically implemented, comprising an upper die 2, a middle die 3 and a lower die 4, wherein the upper die 2 and the lower die 4 are respectively arranged at the upper and lower ends of the middle die 3, and a discharge slot 101 connected to the outside is correspondingly arranged between the upper die 2 and the middle die 3 and between the lower die 4 and the middle die 3, and a plurality of adjustment components 6 for cooperating with the discharge slot 101 are respectively correspondingly arranged on the upper die 2 and the lower die 4, and the plurality of adjustment components 6 are arranged in sequence along the longitudinal extension direction of the discharge slot 101, and the adjustment component 6 comprises a driving motor 61 and a baffle block 62, and a positioning groove 102 for accommodating the baffle block 62 is arranged in the discharge slot 101, and the driving motor 61 drives the baffle block 62 to move up and down along the positioning groove 102 through a coupling 64.

[0035] Furthermore, molding gaskets are correspondingly arranged between the upper mold 2 and the middle mold 3, and between the lower mold 4 and the middle mold 3. A discharge port is arranged on the molding gasket. The width of the product size determines the width of the discharge port. Therefore, different products can be produced by replacing different molding gaskets, thereby reducing the mold opening cost. In addition, the molding gasket can protect the die head from wear and tear, thereby extending the service life of the die head. When replacing or repairing the die head, the molding gasket can be replaced separately, thereby reducing maintenance costs.

[0036] Furthermore, in order to adapt to slurries of different viscosities, the height of the discharge slot 101 can be adjusted according to actual needs. By adjusting the height of the discharge slot 101, the flow of the slurry can be effectively controlled to ensure the uniformity and consistency of the coating process. This design makes the coating equipment more flexible and can meet a variety of production needs.

[0037] Furthermore, the discharge slot 101 is provided with a first slow flow chamber 103 and a second slow flow chamber 104 in sequence from the inside to the outside, and the volume of the first slow flow chamber 103 is larger than the volume of the second slow flow chamber 104. This structure can slow down the flow rate of the slurry and reduce the impact force on the die. This design not only improves the smoothness of the discharge, but also helps to extend the service life of the die. In addition, the slow flow treatment of the slurry by the first slow flow chamber 103 and the second slow flow chamber 104 helps to reduce bubbles and streaks during the coating process and improve the coating quality. The design that the first slow flow chamber 103 is larger than the second slow flow chamber 104 can further optimize the flow characteristics of the slurry and ensure the smoothness and uniformity of the coating process.

[0038] In practical applications, in order to ensure smooth discharge process, the first slow flow chamber 103 and the second slow flow chamber 104 are usually set to be semicircular. The semicircular shape can effectively prevent the slurry from being retained in the corner for a long time, improve the circulation efficiency of the slurry in the slow flow chamber, reduce the probability of the slurry adhering to the chamber wall, reduce maintenance costs, and improve production efficiency. At the same time, the wear resistance of the coating also ensures the long-term stable operation of the equipment.

[0039] Furthermore, the baffle block 62 is provided with a connecting shaft 621 for connecting with the coupling 64. The driving motor 61 drives the baffle block 62 to move up and down through the coupling 64 and the connecting shaft 621 in turn to achieve the function of adjusting the lifting amount of the baffle block 62. The connecting shaft 621 is sequentially sleeved with multiple sealing rings 63 from top to bottom, which can improve the sealing of the die cavity and avoid slurry leakage.

[0040] Furthermore, the baffle block 62 is tightly fitted in the positioning groove 102, and the two adjacent baffle blocks 62 are tightly fitted to each other, so that the positioning groove 102 is sealed. The tight fit between the baffle block 62 and the positioning groove 102 ensures the sealing during the coating process and effectively prevents the leakage of slurry. In this embodiment, in order to ensure the service life of the coating die 1, the baffle block 62 is finely ground with high precision to ensure the size and assembly accuracy (the gap between two adjacent baffle blocks 62 does not exceed 0.5um), so that the baffle block 62 can be seamlessly installed in the positioning groove 102, thereby avoiding the accumulation of slurry in the gap of the baffle block 62 and reducing the probability of slurry dark marks in the coating die 1.

[0041] Furthermore, the discharge slot 101 is externally fitted with a lip 5 for connection with the outside, and the upper die 2, middle die 3, lower die 4 and lip 5 are all made of ceramic or glass materials. In the prior art, the coating die 1 and the lip 5 are generally made of metal materials (for example, the model with excellent corrosion resistance is sus630 or 316l stainless steel). In this embodiment, in order to improve the overall service life of the coating die 1, the upper die 2, middle die 3, lower die 4 and lip 5 are replaced with ceramic or glass materials. The excellent wear resistance, chemical inertness and weak conductivity of the ceramic material are used to improve the service life of the coating die 1. Compared with the die made of metal, the service life is increased by more than 3 times, and the generation of metal particles can be significantly reduced, thereby avoiding affecting the safety performance of the subsequent battery.

[0042] In this embodiment, the coating die head 1 adopts the following control method to perform production operations, and the method includes the following steps:

[0043] Step 1, the coating die head 1 applies a double layer of coating on a substrate moving forward at a uniform speed, and then a wet film thickness gauge arranged at the output end of the coating die head 1 measures the thickness distribution data of the double layer of coating in an undried state;

[0044] Step 2, dividing the thickness distribution data of the double-layer coating into regions in sequence along the longitudinal extension direction of the discharge slot 101, each region corresponding to one of the baffle blocks 62;

[0045] Step 3, when the wet film thickness gauge measures that the coating thickness of one of the areas is greater than or less than the set standard, the coating thickness of the area is reduced or increased by adjusting the lifting amount of the baffle block 62 corresponding to the area, thereby achieving the purpose of accurately controlling the coating thickness and avoiding affecting the coating accuracy;

[0046] Step 4: Before the coating die head 1 finishes coating a roll of substrate, the flow block 62 of the upper die 2 and the lower die 4 needs to be benchmarked. The steps of benchmarking are as follows:

[0047] The discharge slots 101 of the upper mold 2 and the lower mold 4 sequentially output a single layer of coating of a fixed length on the substrate, and the wet film thickness gauge divides the thickness of the two sections of the single layer of coating into regions for measurement, so as to determine whether the thickness of the single layer of coating output by the upper mold 2 and the lower mold 4 respectively reaches the set standard. If the thickness of the single layer of coating output by the upper mold 2 or the lower mold 4 does not reach the set standard, it is necessary to calibrate the lifting amount of the flow block 62 in the corresponding region so that the thickness of the single layer of coating output by the upper mold 2 and the lower mold 4 can reach the set standard. Compared with the process method of only calibrating the total thickness of the double layer of coating in the prior art, adding the benchmark debugging step can effectively avoid the situation of uneven thickness of the upper and lower layers, and regular benchmark debugging can significantly improve the balance of the thickness of the double layer of coating. The present invention divides the thickness distribution data into regions and adopts the structure of the flow block 62 independently controlled by the drive motor 61, so that the coating die head 1 can efficiently and accurately complete the calibration and adjustment of the abnormal area. The benchmark debugging step improves the coating accuracy while ensuring the production efficiency.

[0048] Step 5, set the lifting amount of the baffle block 62 of the upper mold 2 and the lower mold 4 that reaches the set thickness as the benchmark, and start the next round of double-layer coating production. During the production of double-layer coating, implement the steps 1-2 to measure the thickness of the double-layer coating in divided areas. When the wet film thickness gauge measures that the coating thickness of one of the areas is different from the set standard, it is necessary to synchronously adjust the lifting amount of the baffle block 62 of the upper mold 2 and the lower mold 4 corresponding to the area to increase or decrease the coating thickness of the area. Synchronously adjusting the baffle block 62 of the upper mold 2 and the lower mold 4 can reduce the uneven thickness of the upper and lower layers.

[0049] Furthermore, in step 3, the wet film thickness gauge needs to first calculate the average thickness of the coating in the abnormal area, and the coating die head 1 then adjusts the lifting amount of the baffle block 62 according to the average thickness of the coating.

[0050] The height of the discharge slot 101 of the coating die head 1 directly affects the thickness of the coating. In this embodiment, the discharge slots 101 of the upper mold 2 and the lower mold 4 are respectively provided with baffles 62 that can be independently lifted and lowered. The baffles 62 controlled in real time by the drive motor 61 can timely adjust the height of the discharge slot 101, thereby adjusting the thickness of the coating output from the discharge slot 101. In step 5, when the coating thickness of a certain area of ​​the double-layer coating is less than the set standard, the baffles 62 of the corresponding areas of the upper mold 2 and the lower mold 4 are synchronously moved outward by a certain distance, so that the height of the discharge slot 101 in the area is increased, thereby increasing the coating thickness of the local area; when the coating thickness of a certain area is greater than the set standard, the baffles 62 are pushed in the opposite direction, thereby reducing the height of the discharge slot 101 in the area, so that the coating thickness of the area is reduced, thereby achieving precise control of the coating thickness. On the basis of dry film detection, the present invention further uses a wet film thickness gauge to measure the surface density thickness distribution data of the coating just output and not dried by the coating die head 1. This enables us to achieve rapid pre-control adjustment before the dry film closed-loop adjustment. Secondly, the present invention also improves the structure of the lower mold 4, arranging the baffle block 62 and the drive motor 61 that controls the movement of the baffle block 62 at the bottom of the lower mold 4, thereby achieving double-layer fine adjustment of the coating die head 1.

[0051] The wet film thickness gauge described in this embodiment adopts a laser thickness gauge commonly used in the art or other commonly used non-contact optical measuring instruments.

[0052] Embodiment 2:

[0053] The difference between this embodiment and embodiment one lies in the benchmark debugging method of step 4. Compared with embodiment one, the benchmark debugging of step 4 in this embodiment requires less substrate, and the coating thickness output during the benchmark debugging process is more consistent with the coating thickness output during normal production, which is more conducive to improving calibration accuracy.

[0054] The steps of the benchmark debugging of this embodiment are as follows (the premise of the following benchmark debugging is that the thickness of the double-layer coating produced before the benchmark debugging can reach the set standard):

[0055] Before the coating die head 1 finishes coating a roll of substrate, the discharge slots 101 of the upper die 2 and the lower die 4 stop outputting coating in turn, so that a single layer of coating with a fixed length is formed at the end of the product and is only output by the discharge slot 101 of the lower die 4. The wet film thickness gauge measures the thickness of the single layer of coating to obtain the thickness distribution data of the single layer of coating and divides the thickness distribution data into regions. According to the following formula:

[0056] H1+H2=H3;

[0057] Among them, "H1" is the standard thickness of a single layer of coating output by the upper mold 2, "H2" is the standard thickness of a single layer of coating output by the lower mold 4, and "H3" is the standard thickness of a double layer of coating.

[0058] In the above-mentioned measurement process, when the thickness of a single-layer coating in a certain area output by the lower mold 4 is greater than the set standard, the baffle block 62 in the corresponding area of ​​the lower mold 4 is pushed inward to reduce the height of the discharge slot 101 of the lower mold 4 in this area (the coating thickness is reduced), and the baffle block 62 in the corresponding area of ​​the upper mold 2 is simultaneously pushed outward to increase the height of the discharge slot 101 of the upper mold 2 in this area (the coating thickness is increased), thereby balancing the thickness distribution of the double-layer coating so that the thickness of the double-layer coating output by the upper mold 2 and the lower mold 4 can reach the set standard.

[0059] The benchmark debugging method first calibrates the height of the baffle block 62 of the lower mold 4 according to the single-layer coating thickness data of the lower mold 4, and then calibrates the height of the baffle block 62 of the upper mold 2 according to the difference between the single-layer coating thickness data and the double-layer coating thickness data of the lower mold 4, thereby achieving accurate calibration of the height of the upper and lower double-layer baffle blocks 62. If the thickness of the double-layer coating produced before the benchmark debugging fails to meet the set standard, it is necessary to increase the variable of abnormal thickness.

[0060] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention is disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes by using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent changes and modifications made to the above embodiments according to the technology of the present invention are within the scope of the technical solution of the present invention without departing from the content of the technical solution of the present invention.

Claims

1. A coating die head for closed-loop control, comprising an upper die (2) and a lower die (4), wherein a discharge slot (101) communicating with the outside is provided between the upper die (2) and the lower die (4), characterized in that: The upper die (2) is provided with a plurality of adjustment components (6) for cooperating with the discharge slot (101); the plurality of adjustment components (6) are arranged in sequence along the longitudinal extension direction of the discharge slot (101); the adjustment components (6) include a drive motor (61) and a baffle block (62); a positioning groove (102) for accommodating the baffle block (62) is provided in the discharge slot (101); the drive motor (61) drives the baffle block (62) to move up and down along the positioning groove (102) via a coupling (64).

2. A coating die head for closed-loop control according to claim 1, characterized in that: A middle die (3) is arranged between the upper die (2) and the lower die (4), and discharge slots (101) are formed between the upper die (2) and the middle die (3) and between the middle die (3) and the lower die (4), respectively, and a forming gasket is arranged in the discharge slots (101).

3. A coating die head for closed-loop control according to claim 1, characterized in that: The discharge slot (101) is provided with a first slow flow chamber (103) and a second slow flow chamber (104) in sequence from the inside to the outside, and the volume of the first slow flow chamber (103) is greater than the volume of the second slow flow chamber (104).

4. A coating die head for closed-loop control according to claim 1, characterized in that: The baffle block (62) is provided with a connecting shaft (621) for connecting with the coupling (64), and the connecting shaft (621) is sleeved with a plurality of sealing rings (63) in sequence from top to bottom.

5. A coating die head for closed-loop control according to claim 1 or 4, characterized in that: The baffle blocks (62) are tightly embedded in the positioning groove (102), and two adjacent baffle blocks (62) are tightly fitted to each other, so that the positioning groove (102) is sealed.

6. A coating die head for closed-loop control according to claim 1, characterized in that: The discharge slot (101) is fitted with a lip (5) for connection with the outside, and the upper die (2), the middle die (3), the lower die (4) and the lip (5) are all made of ceramic or glass materials.

7. A method for controlling a coating die head for closed-loop control, the method being used to control a coating die head for closed-loop control according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: Step 1, using a wet film thickness gauge arranged at the output end of the coating die (1) to measure the thickness distribution data of the double-layer coating in an undried state; Step 2, dividing the thickness distribution data of the double-layer coating into regions in sequence along the longitudinal extension direction of the discharge slot (101), each of the regions corresponding to one or more of the baffle blocks (62) arranged in sequence; Step 3: When the wet film thickness gauge measures that the coating thickness of one of the areas is different from the set standard, the coating thickness of the area is increased or decreased by adjusting the lifting amount of the baffle (62) corresponding to the area.

8. The control method according to claim 7, characterized in that: In step 3, the wet film thickness gauge needs to calculate the average thickness of the coating in the abnormal area, and the coating die head (1) then adjusts the lifting amount of the baffle block (62) according to the average thickness of the coating in the abnormal area.

9. The control method according to claim 7 or 8, characterized in that: Also includes: Step 4: After the coating die head (1) completes a certain amount of coating operation, the flow blocking blocks (62) of the upper die (2) and the lower die (4) are subjected to benchmark debugging. The steps of the benchmark debugging are as follows: The discharge slots (101) of the upper mold (2) and the lower mold (4) sequentially output a section of a single layer of coating respectively, and the wet film thickness gauge measures the thickness of the two sections of the single layer of coating respectively to determine whether the thickness of the single layer of coating output by the upper mold (2) and the lower mold (4) reaches a set standard. If the thickness of the single layer of coating output by the upper mold (2) or the lower mold (4) does not reach the set standard, the lifting amount of the baffle block (62) in the corresponding area is adjusted so that the thickness of the single layer of coating can reach the set standard; Step 5, setting the lifting amount of the baffle (62) of the upper mold (2) and the lower mold (4) that have reached the set standard as a reference, and starting the next round of coating operation. During the coating operation, the thickness of the double-layer coating is divided into areas for measurement using the steps 1 and 2. When the wet film thickness gauge measures that the coating thickness of one of the areas is different from the set standard, the lifting amount of the baffle (62) of the upper mold (2) and the lower mold (4) corresponding to the area is synchronously adjusted to increase or decrease the coating thickness of the area.

10. The control method according to claim 7 or 8, characterized in that: Also includes: Step 4: After the coating die head (1) has completed a certain amount of coating operation, the flow blocking blocks (62) of the upper die (2) and the lower die (4) are subjected to benchmark debugging. The steps of benchmark debugging are as follows: The discharge slots (101) of the upper mold (2) and the lower mold (4) stop outputting the coating to the outside in sequence, so that a single layer of coating is formed at the end of the product, which is only output by the discharge slot (101) of the lower mold (4); the wet film thickness gauge measures the thickness of the single layer of coating to obtain thickness distribution data of the single layer of coating; and the lifting amount of the flow block (62) of the upper mold (2) and the lower mold (4) is adjusted according to the thickness distribution data, so that the thickness of the single layer of coating can reach a set standard; Step 5, setting the lifting amount of the baffle (62) of the upper mold (2) and the lower mold (4) that have reached the set standard as a reference, and starting the next round of coating operation. During the coating operation, the thickness of the double-layer coating is divided into areas for measurement using the steps 1 and 2. When the wet film thickness gauge measures that the coating thickness of one of the areas is different from the set standard, the lifting amount of the baffle (62) of the upper mold (2) and the lower mold (4) corresponding to the area is synchronously adjusted to increase or decrease the coating thickness of the area.

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