Automatic vacuum system for wind power blade mold and operation method

Abstract

The invention provides an automatic vacuum system for a wind power blade mold and an operation method. The system comprises a vacuum pump unit, a negative pressure detection unit, a control unit and a connecting pipeline unit. The connecting pipeline unit adopts seamless steel pipe welding to replace a traditional steel wire spiral hose to connect a mold and a vacuum pump. The negative pressure detection unit is provided with a plurality of sensors at key positions of the mold. The control unit is based on a PLC, automatically controls starting and stopping of the vacuum pump and opening and closing of the electromagnetic valves of all the pipelines according to a preset program and feedback of the sensors, achieves automatic sequential vacuumizing, pressure maintaining and leakage detection of first vacuum and second vacuum, and prompts the state through an alarm. The problems that in the prior art, manual operation is relied on, connection is prone to leaking, efficiency is low, and errors are prone to occurring are solved, automation of vacuum treatment before filling is achieved, the air exhaust efficiency, the system sealing performance, the product quality stability and the production safety are remarkably improved, and meanwhile the operation and maintenance cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of wind power equipment manufacturing technology, and in particular to an automatic vacuum system and operating method for wind turbine blade molds. Background Technology

[0002] Wind turbine blades, as the core components of wind turbine generators, are primarily manufactured using epoxy fiberglass composite materials, and their service life is typically required to exceed 20 years. Resin vacuum infusion is one of the key processes in blade molding. This process first uses a vacuum pump to remove residual air from the fiberglass cloth and auxiliary materials laid in the mold cavity, creating a negative pressure inside the mold cavity. Then, under the drive of negative pressure, epoxy resin is infused, thereby completing the blade molding process.

[0003] Existing vacuum systems for wind turbine blade molds mostly rely on manual control of vacuum pump start / stop and pipeline opening / closing, which presents the following problems: 1) Manual operation has a slow response time, making it difficult to adjust the vacuum level in real time, resulting in large fluctuations in the vacuum level; 2) Pressure holding detection relies on manual observation, resulting in low detection accuracy and the failure to detect excessive vacuum drop in time, leading to blade defects; 3) During the vacuuming process, the injected adhesive is prone to backflow into the system pipeline, causing pipeline blockage or equipment damage; 4) There is a lack of flexible control modes, and it is impossible to quickly switch operating modes in abnormal situations, affecting production efficiency. Summary of the Invention

[0004] Therefore, it is necessary to provide an automatic vacuum system and operating method for wind turbine blade molds to address the aforementioned technical problems.

[0005] An automatic vacuum system for wind turbine blade molds includes: a vacuum pump unit, a negative pressure detection unit, a control unit, and a connecting pipeline unit;

[0006] The vacuum pump unit is used to provide vacuum power for the mold vacuum system;

[0007] The negative pressure detection unit is used to detect the real-time negative pressure value of the mold vacuum system pipeline;

[0008] The control unit is connected to the vacuum pump unit and the negative pressure detection unit respectively, and is used to receive the detection signal from the negative pressure detection unit and automatically control the start and stop of the vacuum pump unit and the opening and closing of the mold vacuum pipeline according to the preset program.

[0009] The connecting pipeline unit is used to connect the vacuum pump unit to the vacuum system interface of the wind turbine blade mold.

[0010] In one embodiment, the vacuum pump unit includes a vacuum pump and a vacuum pump control box;

[0011] The vacuum pump is electrically connected to the vacuum pump control box, which supports switching between remote control and local control modes to realize the start and stop control of the vacuum power unit.

[0012] In one embodiment, the negative pressure detection unit includes a vacuum pump negative pressure sensor and a mold negative pressure sensor;

[0013] The mold negative pressure sensor is installed on the mold vacuum pipeline, and the vacuum pump negative pressure sensor is installed on the pipeline connecting the vacuum pump unit and the mold.

[0014] In one embodiment, it further includes:

[0015] The mold negative pressure sensor has at least three sets, which are respectively set at the blade root, blade middle and blade tip positions of the trailing edge pipe of the pressure surface and suction surface of the mold.

[0016] In one embodiment, the control unit includes a vacuum system control box;

[0017] The vacuum system control box is used to convert the analog signals output by the sensing unit into digital signals and execute a preset control program.

[0018] In one embodiment, the connecting pipeline unit includes a main pipeline, a first branch pipeline, a second branch pipeline, and a buffer tank;

[0019] The main pipeline is connected to the outlet of the vacuum pump unit, the first branch pipeline is connected to the vacuum interface of mold one, the second branch pipeline is connected to the vacuum interface of mold two, and the buffer tank is installed on the main pipeline;

[0020] Both the first branch pipeline and the second branch pipeline are equipped with solenoid valves controlled by the control unit.

[0021] In one embodiment, the nominal diameter of the first seamless steel pipe is DN80, the nominal diameter of the second seamless steel pipe is DN50, and both the first and second seamless steel pipes are connected by welding.

[0022] In one embodiment, the control system further includes an alarm notification device;

[0023] When the vacuum system control box malfunctions or the vacuum test passes, it controls the alarm notification device to issue a notification signal.

[0024] An automatic vacuum operation method for wind turbine blade molds, used in an automatic vacuum system for wind turbine blade molds as described above, includes:

[0025] S1: System initialization, in the control unit, set the target negative pressure parameters, pressure holding test parameters and automatic timing parameters according to the local atmospheric pressure;

[0026] S2: After the mold is laid up, the automatic program is started in the control unit. The control unit issues a command to open the vacuum pump unit and the solenoid valve of the corresponding mold vacuum pipeline to start evacuating the mold vacuum pipeline.

[0027] S3: The negative pressure detection unit detects the pressure of the vacuum pipeline of the mold in real time and feeds it back to the control unit. When the preset first vacuum target negative pressure value is reached, the control unit controls the vacuum pump unit to stop running.

[0028] S4: According to the preset delay time, the control unit automatically issues a command to open the solenoid valve of the vacuum pipeline of mold two and start the vacuum pump unit to evacuate the vacuum pipeline of mold two.

[0029] S5: When the vacuum line of mold 2 reaches the preset target negative pressure value, the control unit closes the solenoid valve of the vacuum line of mold 1, and the vacuum line of mold 2 enters the pressure holding test procedure.

[0030] S6: During the preset pressure holding time, the pressure change of the vacuum pipeline of the mold is monitored by the negative pressure detection unit. If the pressure drop is less than the preset threshold, the control unit will prompt the inspection to pass through the alarm and the filling process can proceed. If the pressure drop exceeds the threshold or an abnormality occurs, the control unit will sound an alarm through the alarm.

[0031] Compared to existing technologies, the advantages and beneficial effects of this invention are as follows: The automatic vacuum system and operating method for wind turbine blade molds provided by this invention upgrades the traditional, decentralized, and manual steel wire hose connection and operation to a fully automatic closed-loop control system based on seamless steel pipe welding pipelines and centered on a PLC. This fundamentally solves the prominent problems of low efficiency, easy leakage, high quality risk, and high cost inherent in the original technology. This invention significantly improves the air extraction efficiency by over 33%, significantly enhances product quality and stability, eliminates human error through automatic program control, and ensures process consistency through multi-point real-time monitoring; effectively reduces operating and maintenance costs, decreasing hose consumption and valve repair; achieves a high degree of automation and intelligence, reducing labor intensity and improving production efficiency and process reliability; and possesses comprehensive abnormal alarm and status indication functions, further ensuring production safety. This invention not only optimizes the vacuum injection process itself but also provides solid technical support for the high-quality, large-scale, and reliable manufacturing of wind turbine blades. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of an automatic vacuum system for wind turbine blade molds in one embodiment;

[0033] Figure 2 This is a schematic diagram of an automatic vacuum system control for a wind turbine blade mold in one embodiment;

[0034] Figure 3 This is a flowchart illustrating an automatic vacuum operation method for a wind turbine blade mold in one embodiment.

[0035] In the diagram, 1-vacuum pump control box, 2-vacuum pump negative pressure sensor, 3-solenoid valve, 4-first branch pipeline, 5-buffer tank, 6-second branch pipeline, 7-mold negative pressure sensor, 8-vacuum system control box, 9-signal line, 10-alarm device, 11-vacuum pump. Detailed Implementation

[0036] Before describing the specific embodiments of the present invention, the overall concept of the present invention will be explained as follows:

[0037] This invention is mainly about the development of the vacuum injection molding process of resin for wind turbine blades. Currently, the industry generally uses a vacuum system with manual connection of steel wire spiral hose and manual operation for starting and stopping. This system has problems such as low pumping efficiency, easy leakage of pipelines, cumbersome operation and dependence on personnel experience, and high quality risk.

[0038] The inventors, through analysis, discovered that the main reasons for the aforementioned problems are: poor sealing, numerous joints, and significant friction loss in traditional hose connections; reliance on manual operation for starting and stopping all valves and pumps, leading to potential misoperation or omissions; and a lack of real-time, multi-point automatic monitoring and closed-loop control of the system's vacuum level. By replacing hoses with seamless steel pipe welded conduits, installing multi-point negative pressure sensors for real-time monitoring, and implementing automatic program control of the vacuum pump and solenoid valves based on a PLC, these problems can be avoided. Therefore, this invention proposes an automatic vacuum system for wind turbine blade molds, achieving full automation from vacuuming and pressure holding to inspection, significantly improving system reliability, pumping efficiency, and product quality consistency.

[0039] After introducing the overall concept of the present invention, in order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings.

[0040] It should be noted that, unless otherwise defined, the technical or scientific terms used in one or more embodiments of this specification should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in one or more embodiments of this specification do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word covers the element or object listed following the word and its equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0041] For ease of understanding, the terms used in the embodiments of this invention are explained below:

[0042] PLC: Programmable Logic Controller

[0043] PS side: Pressure side

[0044] SS surface: suction surface

[0045] In one embodiment, an automatic vacuum system for wind turbine blade molds is provided, the system including a vacuum pump unit, a negative pressure detection unit, a control unit, and a connecting pipeline unit.

[0046] like Figure 1 The diagram shown is a schematic of an automatic vacuum system for wind turbine blade molds. Figure 2 The diagram shown is a schematic of an automatic vacuum system control for a wind turbine blade mold.

[0047] The vacuum pump unit is the power source of the system, including a vacuum pump 11 and a vacuum pump control box 1, which are electrically connected. The vacuum pump control box 1 can receive remote commands from the control unit 8, or switch to local mode. Through the built-in controller, it controls the start and stop of the vacuum pump according to the signal of the vacuum pump negative pressure sensor 2 and the set threshold, so as to provide stable vacuum power for the entire vacuum system.

[0048] The negative pressure detection unit includes at least one vacuum pump negative pressure sensor 2 and at least three sets of mold negative pressure sensors 7. The vacuum pump negative pressure sensor 2 is installed on the connecting pipeline between the vacuum pump unit and the mold, and is used to detect the negative pressure value at the output end of the vacuum pump. The mold negative pressure sensors 7 are installed on the mold vacuum pipeline, preferably on the trailing edge pipeline of the PS and SS surfaces, with one sensor each at the blade root, blade middle, and blade tip, for a total of multiple sensors, to comprehensively and accurately monitor the vacuum level in various areas of the mold. All sensors communicate with the control unit via signal lines 9.

[0049] The core of the control unit is the vacuum system control box 8, which integrates a PLC. Its panel has an automatic / manual mode button, a start / stop button, a parameter setting interface, and status indicator lights. The PLC receives analog current signals from various sensors through signal line 9 and outputs digital commands to control the opening and closing of the solenoid valve 3, the start and stop of the vacuum pump control box 1, and the status of the alarm device 10.

[0050] The alarm device 10 uses a three-color light alarm, controlled by the control box 8, and issues corresponding prompt signals when the system malfunctions or the vacuum test passes. A solid yellow light indicates that the system is running, a flashing green light with an alarm indicates that the vacuum test has passed, and a flashing red light with an alarm indicates that the system is malfunctioning or the test has failed.

[0051] The connecting pipeline unit is responsible for delivering vacuum, including the main pipeline, the first branch pipeline 4, the second branch pipeline 6, and the buffer tank 5. The main pipeline connects to the outlet of the vacuum pump unit, the first branch pipeline 4 connects to the vacuum interface of mold one, and the second branch pipeline 6 connects to the vacuum interface of mold two. The buffer tank 5 is located on the main pipeline to prevent glue from entering the system pipeline and causing blockage in case of abnormal pouring. The first branch pipeline 4 uses a seamless steel pipe with a nominal diameter of DN80, and the second branch pipeline 6 uses a seamless steel pipe with a nominal diameter of DN50, both connected by welding. Both the first branch pipeline 4 and the second branch pipeline 6 are equipped with solenoid valves 3 controlled by the control unit to realize automatic control of pipeline opening and closing.

[0052] The automatic vacuum system and operating method for wind turbine blade molds provided by this invention upgrades the traditional, decentralized, and manual steel wire hose connection and operation to a fully automatic closed-loop control system based on seamless steel pipe welding pipelines and centered on a PLC. This fundamentally solves the prominent problems of low efficiency, easy leakage, high quality risk, and high cost inherent in the original technology. This invention significantly improves pumping efficiency by over 33%, significantly enhances product quality and stability, eliminates human error through automatic program control, and ensures process consistency through multi-point real-time monitoring. Operating and maintenance costs are effectively reduced, decreasing hose consumption and valve repair. It achieves a high degree of automation and intelligence, reducing labor intensity and improving production efficiency and process reliability. Simultaneously, it possesses comprehensive abnormal alarm and status indication functions, further ensuring production safety. This invention not only optimizes the vacuum injection process itself but also provides solid technical support for the high-quality, large-scale, and reliable manufacturing of wind turbine blades.

[0053] It should be noted that the above description describes some embodiments of the present invention. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims may be performed in a different order than that shown in the above embodiments and still achieve the desired results. Furthermore, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0054] Based on the same inventive concept, corresponding to any of the above embodiments, the present invention also provides an automatic vacuum operation method for wind turbine blade molds.

[0055] refer to Figure 3 The automatic vacuum operation method for wind turbine blade molds includes:

[0056] S1: System initialization, in the control unit, set the target negative pressure parameters, pressure holding test parameters and automatic timing parameters according to the local atmospheric pressure;

[0057] S2: After the mold is laid up, the automatic program is started in the control unit. The control unit issues a command to open the solenoid valve of the vacuum pump unit and the corresponding vacuum pipeline of the mold, and starts to evacuate the vacuum pipeline.

[0058] S3: The negative pressure detection unit detects the pressure of the mold-vacuum pipeline-vacuum pipeline in real time and feeds it back to the control unit. When the preset first vacuum target negative pressure value is reached, the control unit controls the vacuum pump unit to stop running.

[0059] S4: According to the preset delay time, the control unit automatically issues a command to open the solenoid valve of the second vacuum line of the mold and starts the vacuum pump unit to evacuate the second vacuum line of the mold.

[0060] S5: When the vacuum line of mold 2 reaches the preset target negative pressure value, the control unit closes the solenoid valve of the vacuum line of mold 1, and the vacuum line of mold 2 enters the pressure holding test procedure.

[0061] S6: During the preset pressure holding time, the pressure change of the vacuum pipeline of the mold is monitored by the negative pressure detection unit. If the pressure drop is less than the preset threshold, the control unit will prompt the inspection to pass through the alarm and the filling process can proceed. If the pressure drop exceeds the threshold or an abnormality occurs, the control unit will sound an alarm through the alarm.

[0062] Within the preset pressure holding time (10 min), the pressure change of the vacuum pipeline of the mold is monitored by the negative pressure detection unit: if the pressure drop is less than the preset threshold (20 mbar), the control unit controls the alarm to indicate that the inspection has passed and the pouring process can be started;

[0063] If the voltage drop exceeds the threshold or the system malfunctions, the control unit will activate the alarm to send an alarm signal.

[0064] In addition, in case of abnormal situations or special needs, the vacuum pump control box 1 can be switched to the local control mode to manually or automatically control the start and stop of the vacuum pump to adapt to different working conditions.

[0065] The methods described above are used in an automatic vacuum system for wind turbine blade molds in any of the foregoing embodiments, and have the beneficial effects of the corresponding system embodiments, which will not be repeated here.

[0066] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0067] Example 1

[0068] Take a certain type of blade mold in Rudong area of ​​Jiangsu Province (local atmospheric pressure is about 1016 hPa) as an example.

[0069] Parameter settings: On the vacuum system control box 8, set the target negative pressure values ​​of both the primary vacuum and secondary vacuum to 965.2 hPa (95% of 1016 hPa), set the pressure holding test standard to a pressure drop of less than 20 mbar (approximately 20 hPa) within 10 minutes, and set the automatic start delay time of the secondary vacuum to 30 minutes (estimated based on the secondary vacuum membrane laying time).

[0070] Initiating a vacuum: After the vacuum membrane is laid, the operator sets the control box 8 to automatic mode and starts the system. The PLC issues a command to start the vacuum pump 11 and open the solenoid valve of the mold's vacuum pipeline. The system begins evacuation, and the sensors 7 report the pressure.

[0071] Vacuum completion: When the control box 8 detects that the pressure in the mold and vacuum pipeline has reached 965.2 hPa, it issues a command to stop the vacuum pump 11, and the vacuum enters the pressure holding and waiting state.

[0072] Automatic start of secondary vacuum: After waiting 30 minutes (by which time the secondary vacuum membrane should have been laid), the PLC automatically issues a command to restart vacuum pump 11 and open the solenoid valve of the secondary vacuum pipeline of the mold, while keeping the solenoid valve of the primary vacuum pipeline of the mold open (for pressure comparison). The system evacuates the secondary vacuum.

[0073] Second vacuum test: When the second vacuum pressure also reaches 965.2 hPa, the PLC closes the solenoid valve of the first vacuum pipeline of the mold. At this time, only the second vacuum pipeline of the mold is connected to the running vacuum pump 11, and the test enters the 10-minute pressure holding stage.

[0074] Result determination: The PLC continuously monitors the pressure of the vacuum pipeline in mold two. If, after 10 minutes, the pressure increase does not exceed 20 hPa (i.e., the pressure does not exceed 985.2 hPa), the test is considered passed, and the alarm indicator 10 will flash green and sound, indicating to the operator that resin pouring can begin. If the pressure increases beyond this value, the alarm indicator 10 will flash red and sound an alarm, requiring a leak check.

[0075] In case of automatic mode failure or special operation required, the system can be switched to manual mode. Each pump and valve can be controlled individually via the buttons on the control box 8, or the vacuum pump control box 1 can be used for local operation, ensuring the flexibility of the system.

[0076] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the embodiments of the invention as described above, which are not provided in the details for the sake of brevity.

[0077] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0078] While specific details have been set forth to describe exemplary embodiments of the invention, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details or with variations thereof. Therefore, these descriptions should be considered illustrative rather than restrictive. Although the invention has been described in conjunction with specific embodiments thereof, many substitutions, modifications, and variations of these embodiments will be apparent to those skilled in the art based on the foregoing description.

[0079] The embodiments of this invention are intended to cover all such substitutions, modifications, and variations falling within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of this invention should be included within the protection scope of this invention.

Claims

1. An automatic vacuum system for wind turbine blade moulds, characterised in that, The wind power blade mold automatic vacuum system comprises a vacuum pump unit, a negative pressure detection unit, a control unit and a connecting pipeline unit. The vacuum pump unit is used for providing vacuum power for a mold vacuum system. The negative pressure detection unit is used for detecting a real-time negative pressure value of a pipeline of the mold vacuum system. The control unit is respectively connected with the vacuum pump unit and the negative pressure detection unit in signal connection, is used for receiving a detection signal of the negative pressure detection unit, and automatically controls starting and stopping of the vacuum pump unit and opening and closing of a mold vacuum pipeline according to a preset program. The connecting pipeline unit is used for connecting the vacuum pump unit and a vacuum system interface of the wind power blade mold. The vacuum pump unit comprises a vacuum pump and a vacuum pump control box.

2. An automatic vacuum system for wind turbine blade moulds according to claim 1, characterised in that, The vacuum pump is electrically connected with the vacuum pump control box, the vacuum pump control box supports remote control and on-site control mode switching, and is used for realizing starting and stopping control of the vacuum power unit. The negative pressure detection unit comprises a vacuum pump negative pressure sensor and a mold negative pressure sensor.

3. The automatic vacuum system for wind turbine blade moulds according to claim 1, characterised in that, The mold negative pressure sensor is arranged on a mold vacuum pipeline, and the vacuum pump negative pressure sensor is arranged on a connecting pipeline between the vacuum pump unit and the mold. Further comprising:

4. An automatic vacuum system for wind turbine blade moulds according to claim 4, characterised in that, The mold negative pressure sensor has at least three groups, which are respectively arranged at a blade root, a blade middle and a blade tip position of a pressure surface and a suction surface rear edge pipeline of the mold. The control unit comprises a vacuum system control box.

5. The automatic vacuum system for wind turbine blade mold according to claim 1, wherein, The vacuum system control box is used for converting an analog signal output by a sensing unit into a digital signal and executing a preset control program. The connecting pipeline unit comprises a main pipeline, a first branch pipeline, a second branch pipeline and a buffer tank.

6. An automatic vacuum system for wind turbine blade moulds according to claim 1, characterised in that, The main pipeline is connected with an outlet of the vacuum pump unit, the first branch pipeline is connected with a first mold vacuum interface, the second branch pipeline is connected with a second mold vacuum interface, and the buffer tank is arranged on the main pipeline. The first branch pipeline and the second branch pipeline are respectively provided with an electromagnetic valve controlled by the control unit. The first seamless steel pipe has a nominal diameter of DN80, the second seamless steel pipe has a nominal diameter of DN50, and the first seamless steel pipe and the second seamless steel pipe are connected by welding.

7. An automatic vacuum system for wind turbine blade moulds according to claim 6, characterised in that, The control system further comprises an alarm prompting device.

8. An automatic vacuum system for wind turbine blade moulds according to claim 1, characterised in that, The vacuum system control box controls the alarm prompting device to send a prompt signal when the system abnormally operates or vacuum inspection is passed. The wind power blade mold automatic vacuum system comprises the following steps:

9. An automatic vacuum method of operating a wind turbine blade mould, characterised in that, S1: system initialization, setting target negative pressure parameters, pressure maintaining inspection parameters and automatic timing parameters in the control unit according to local atmospheric pressure; S2: after mold layering is completed, starting an automatic program in the control unit, the control unit sends an instruction to start the vacuum pump unit and the electromagnetic valve of the corresponding first mold vacuum pipeline, and starts vacuumizing the first mold vacuum pipeline; S3: the negative pressure detection unit detects the pressure of the first mold vacuum pipeline in real time and feeds back to the control unit, and when a preset first vacuum target negative pressure value is reached, the control unit controls the vacuum pump unit to stop running; S4: according to a preset delay time, the control unit automatically sends an instruction to start the electromagnetic valve of the second mold vacuum pipeline, and starts vacuumizing the second mold vacuum pipeline by the vacuum pump unit. ​ S5: When the mold two vacuum pipeline reaches the preset target negative pressure value, the control unit closes the electromagnetic valve of the mold one vacuum pipeline, and the mold two vacuum pipeline enters the pressure maintaining inspection program; S6: Within the preset pressure maintaining time, the pressure change of the mold two vacuum pipeline is monitored by the negative pressure detection unit. If the pressure drop is less than the preset threshold value, the control unit prompts the inspection passing through the alarm, and the pouring process can be performed; if the pressure drop exceeds the threshold value or an abnormality occurs, the control unit alarms through the alarm.

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