Method and apparatus for facilitating the cooling and setting of a polylactic acid formed article

Abstract

The present disclosure provides a device and method for facilitating cooling and setting of a polylactic acid molded product, such as an electric energy metering box. The device includes a fixed mold, a movable mold arranged to be movable relative to the fixed mold and defining a mold cavity with the fixed mold for accommodating a polylactic acid material, a mold opening and closing mechanism operatively connected with the movable mold for moving the movable mold to perform mold opening or closing, a displacement sensor arranged on the movable mold for detecting an opening displacement amount, a gas cooling pipeline including a nozzle arranged on at least one molding surface of the fixed mold and a solenoid valve arranged in a gas path in communication with the nozzle, and a controller communicatively connected with the displacement sensor and the solenoid valve and configured to control the gas cooling pipeline to cool the molded product using gas according to the opening displacement detected by the displacement sensor.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of polylactic acid material processing, and more particularly to a method and device for promoting cooling and setting of a polylactic acid formed product. BACKGROUND

[0002] Polylactic acid (PLA) is a polymer material with good mechanical properties, environmental friendliness and biocompatibility, and is currently widely used in many fields, including for manufacturing electric energy metering boxes.

[0003] Generally, polylactic acid material is used to manufacture electric energy metering boxes by injection molding process. In order to make polylactic acid meet the heat resistance requirements of electric energy metering box products, the polylactic acid needs to be annealed first. The temperature of the polylactic acid electric energy metering box injection molding workpiece is high at the moment of mold opening after annealing, and the workpiece has not yet completely cooled and set. At present, natural cooling and setting is usually used, but natural cooling takes a long time, which seriously affects production efficiency. At the same time, this cooling stage will directly affect the degree of product deformation and affect product quality. SUMMARY

[0004] In order to improve production efficiency and reduce deformation to ensure product quality, the present disclosure provides a device and method for promoting cooling and setting of a polylactic acid formed product such as an electric energy metering box.

[0005] One embodiment of the present disclosure provides a device for promoting cooling and setting of a polylactic acid formed product, comprising: a fixed mold; a movable mold arranged to be movable relative to the fixed mold and defining a cavity with the fixed mold for accommodating a polylactic acid material; a mold opening and closing mechanism operatively connected with the movable mold for moving the movable mold to open or close the mold; a displacement sensor arranged on the movable mold for detecting an opening displacement amount; a gas cooling pipeline comprising a nozzle arranged on at least one forming surface of the fixed mold and an electromagnetic valve arranged in a gas path in communication with the nozzle; and a controller communicatively connected with the displacement sensor and the electromagnetic valve and configured to control the gas cooling pipeline to cool the formed product with gas according to the opening displacement detected by the displacement sensor.

[0006] In some embodiments, the controller is configured to send an opening instruction to the electromagnetic valve when the opening displacement detected by the displacement sensor reaches a set threshold, so that the nozzle blows out gas for cooling the formed product. By blowing gas to the polylactic acid formed product immediately after mold opening, deformation caused by uneven heat dissipation and slow heat dissipation during mold opening is reduced, thereby effectively improving the quality of the product; and the cooling time is reduced, thereby improving the production efficiency.

[0007] In some embodiments, the nozzle comprises: an upper nozzle arranged on the molding surface of the fixed mold and on the upper side; a lower nozzle arranged on the molding surface of the fixed mold and on the lower side; and a middle nozzle arranged on the middle part of the molding surface of the fixed mold between the upper nozzle and the lower nozzle.

[0008] By arranging the upper, middle and lower nozzles, the gas can be uniformly blown to the polylactic acid molded product, the heat dissipation tends to be uniform, the deformation caused by uneven heat dissipation is inhibited, and the molding quality is improved.

[0009] In some embodiments, the upper nozzle and the middle nozzle are configured to spray columnar gas flow, and the lower nozzle is configured to spray conical gas flow. By columnar gas flow, the residual heat at the bottom of the molded product can be quickly removed, and the side wall structure can be uniformly cooled; by conical gas flow, the complex curved surface of the molded product can be covered.

[0010] In some embodiments, the upper nozzle comprises a first columnar gas flow nozzle and a second columnar gas flow nozzle, and the first columnar gas flow nozzle and the second columnar gas flow nozzle are aligned in the horizontal direction and spaced apart by a predetermined distance; and / or, the middle nozzle comprises a third columnar gas flow nozzle and a fourth columnar gas flow nozzle, and the third columnar gas flow nozzle and the fourth columnar gas flow nozzle are aligned in the vertical direction and spaced apart by a predetermined distance; and / or, the lower nozzle comprises a first conical gas flow nozzle and a second conical gas flow nozzle, and the first conical gas flow nozzle and the second conical gas flow nozzle are aligned in the horizontal direction and spaced apart by a predetermined distance.

[0011] By configuring the nozzle in this way, the bottom, side wall and reinforcing rib area of the molded product can be covered. The blown gas flow can quickly and uniformly cover the surface of the molded product, achieving the purpose of uniform cooling and rapid cooling.

[0012] In some embodiments, a pressure regulating valve is provided in the gas cooling pipeline corresponding to each nozzle. And the controller is configured to: when the mold opening displacement detected by the displacement sensor reaches a first threshold, send an opening instruction to the electromagnetic valve and a first pressure regulating instruction to the pressure regulating valve to spray gas flow at a first gas pressure; when the mold opening displacement detected by the displacement sensor reaches a second threshold (which is greater than the first threshold), send a second pressure regulating instruction to the pressure regulating valve to spray gas flow at a second gas pressure, which is lower than the first gas pressure.

[0013] In some embodiments, the controller is configured to: when the mold opening displacement detected by the displacement sensor reaches a third threshold (which is greater than the second threshold), send a third pressure regulating instruction to the pressure regulating valve to spray gas flow at a third gas pressure, which is less than the second gas pressure.

[0014] In some embodiments, the controller is configured to: only enable the upper layer nozzle to blow gas when the mold opening displacement detected by the displacement sensor is between the first threshold value and the second threshold value; further enable the middle layer nozzle to blow gas when the mold opening displacement detected by the displacement sensor reaches the second threshold value; further enable the lower layer nozzle to blow gas when the mold opening displacement detected by the displacement sensor reaches the third threshold value.

[0015] In some embodiments, the device further comprises a temperature sensor for detecting the temperature of the molded product, and the controller is configured to send a closing instruction to the electromagnetic valve to close the gas flow of the nozzle when the temperature detected by the temperature sensor reaches a preset threshold value.

[0016] The above embodiments, by means of multiple directions and multiple layers of gas blowing, enable the various parts of the molded product to be uniformly cooled at approximately the same cooling rate, thereby avoiding deformation of the molded product caused by uneven cooling.

[0017] Another embodiment of the present disclosure provides a method for facilitating the cooling and shaping of a polylactic acid molded product using the device of any one of the embodiments of the present disclosure, which comprises: detecting the mold opening displacement of a moving mold relative to a fixed mold by a displacement sensor, wherein the displacement sensor is arranged on the moving mold, at least one molding surface of the fixed mold is provided with a nozzle and a gas path connected to the nozzle, and an electromagnetic valve is arranged in the gas path; and controlling the gas cooling path to use gas to cool the molded product according to the mold opening displacement detected by the displacement sensor by means of a controller.

[0018] In some embodiments, the controller sends an opening instruction to the electromagnetic valve when the mold opening displacement detected by the displacement sensor reaches a set threshold value, so that the nozzle blows gas for cooling the molded product.

[0019] In some embodiments, the nozzle comprises: an upper layer nozzle arranged on the molding surface of the fixed mold and close to the upper side; a lower layer nozzle arranged on the molding surface of the fixed mold and close to the lower side; and a middle layer nozzle arranged in the middle of the molding surface of the fixed mold between the upper layer nozzle and the lower layer nozzle.

[0020] In some embodiments, a pressure regulating valve is arranged in the gas cooling path corresponding to each nozzle. The processing performed by the controller comprises: sending an opening instruction to the electromagnetic valve and a first pressure regulating instruction to the pressure regulating valve to blow gas at a first gas pressure when the mold opening displacement detected by the displacement sensor reaches a first threshold value; and sending a second pressure regulating instruction to the pressure regulating valve to blow gas at a second gas pressure when the mold opening displacement detected by the displacement sensor reaches a second threshold value, the second gas pressure being lower than the first gas pressure, and the second threshold value being greater than the first threshold value.

[0021] In some embodiments, the processing performed by the controller further includes: sending a third pressure regulating instruction to the pressure regulating valve to spray a gas flow at a third gas pressure when the mold opening displacement detected by the displacement sensor reaches a third threshold value, the third gas pressure being less than the second gas pressure, and the third threshold value being greater than the second threshold value.

[0022] In some embodiments, the processing performed by the controller includes: only enabling the upper nozzle to spray a gas flow when the mold opening displacement detected by the displacement sensor is between the first threshold value and the second threshold value; further enabling the middle nozzle to spray a gas flow when the mold opening displacement detected by the displacement sensor reaches the second threshold value; and further enabling the lower nozzle to spray a gas flow when the mold opening displacement detected by the displacement sensor reaches the third threshold value.

[0023] In some embodiments, the method further includes: detecting the temperature of the formed product by a temperature sensor, and sending a closing instruction to the electromagnetic valve by the controller to close the gas flow of the nozzle when the temperature detected by the temperature sensor reaches a preset threshold value.

[0024] In embodiments, the above method of promoting the cooling and setting of a polylactic acid formed product is applied to the molding of a polylactic acid electric energy metering box, and the following beneficial effects can be obtained:

[0025] 1. Improving cooling efficiency

[0026] Compared with natural cooling, blowing promotes the cooling and molding of a polylactic acid electric energy metering box, and the speed is faster. Under the same temperature conditions, the cooling time can be reduced to 70% of that of natural cooling by this method.

[0027] 2. Reducing deformation of the electric energy metering box

[0028] By uniformly blowing and cooling the polylactic acid electric energy metering box at each part through multi-branch gas flow, deformation of the box caused by uneven cooling is avoided; and after promoting the cooling and molding of the electric energy metering box, deformation caused by uneven force during demolding can be effectively avoided.

[0029] 3. Reducing production cost

[0030] By accelerating the cooling rate, the utilization rate of the mold per unit time is improved; and the deformation of the electric energy metering box is greatly reduced, and the yield of the product is increased. Therefore, the production cost of the polylactic acid electric energy metering box is reduced from multiple angles.

[0031] 4. Promoting industry development

[0032] Promote high-precision injection molding manufacturing standards, accelerate the large-scale production of smart grid equipment (such as electric energy metering boxes), provide reliable technical solutions for polymer product fields such as automobile electronics and electronic products, promote industrial innovation, and promote industry development. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a schematic diagram showing the structure of the device for promoting the cooling and setting of a polylactic acid molded product according to an embodiment of the present application.

[0034] Figure 2 is a schematic diagram showing Figure 1 is a layout diagram of the nozzle of the device shown.

[0035] Figure 3 shows Figure 1 shows an example of the processing flow performed by the controller in the device shown.

[0036] Figure 4 is a picture schematically showing the stress results of a polylactic acid electric energy metering box front cover.

[0037] Figure 5 is a chart showing the stress of a polylactic acid electric energy metering box at different cooling endpoint temperature collection points. DETAILED DESCRIPTION

[0038] The exemplary embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be noted that the present application can be implemented in various forms and is not limited to the specific examples described herein or shown in the accompanying drawings.

[0039] The descriptions herein regarding the positions of elements (such as “top”, “bottom”, “above”, “below”, “left side”, “right side”, etc.) are only used to indicate the relative directions of the elements in the drawings. These descriptions are only examples and are not limiting. In other embodiments, the directions of the elements can be different, and these changes are also included in the scope of the present disclosure.

[0040] In addition, the terms “substantially”, “approximately”, “generally”, and other similar terms are used herein as descriptive terms, not as precise limitations. These terms are intended to cover a reasonable error range that a person skilled in the art can identify in measurement, calculation, manufacturing, etc. The terms “comprise”, “include” and “have” are used herein to indicate the presence of certain features, steps, operations, elements and / or components, but do not exclude the presence or addition of other features, steps, operations, elements, components or combinations thereof. In addition, unless the context clearly dictates otherwise, the terms “first”, “second” and the like similar terms do not indicate any priority or order, but are only used to distinguish different objects in the description.

[0041] Further, as used herein, the term "connected" and its derivatives refer to any connection, direct or indirect, between two components. Such connection can be mechanical, electrical, or fluidic, among others.

[0042] The present disclosure provides a solution to promote the cooling and setting of a polylactic acid molded product, such as a polylactic acid electricity metering box, to address the low cooling efficiency and the deformation during the cooling process of the existing polylactic acid electricity metering box. Specifically, when the polylactic acid electricity metering box is molded, the temperature of the mold and the molded product is maintained at about 120°C, and the temperature remains high after the mold is opened. The molded product is not fully set, and therefore deformation occurs when the mold is removed. If the molded product is allowed to cool naturally, the production efficiency is severely affected.

[0043] Figure 1 An example structure of the device for promoting the cooling and setting of a polylactic acid molded product is schematically shown. As shown in the figure, the device includes a fixed mold 100, a movable mold 200 arranged to be movable relative to the fixed mold 100 and defining a cavity with the fixed mold 100 for accommodating a polylactic acid material, an opening and closing mechanism 300 operatively connected with the movable mold 200 for moving the movable mold 200 to open or close the mold, a displacement sensor 400 arranged on the movable mold 200 for detecting the opening displacement, a gas cooling pipeline 500 including a nozzle 510 arranged on at least one molding surface of the fixed mold 100 and an electromagnetic valve 520 arranged in a gas path in communication with the nozzle, and a controller 600 communicatively connected with the displacement sensor 400 and the electromagnetic valve 520 and configured to control the gas cooling pipeline 500 to cool the molded product using gas according to the opening displacement detected by the displacement sensor 400.

[0044] In some embodiments, the displacement sensor 400 can be a magnetostrictive displacement sensor or a laser ranging sensor, among others, or other sensors known in the art that can measure displacement. In some embodiments, the displacement sensor 400 is installed in a position substantially parallel to the movement direction of the movable mold 200 to ensure that the measured value is consistent with the actual opening stroke. In some embodiments, the displacement sensor 400 has a range of 0-2000mm, and mechanical vibration interference is reduced by sliding average filtering (5-point window).

[0045] In some embodiments, the controller 600 comprises a memory storing computer readable instructions or programs and a processor executing the computer readable instructions or programs to perform any one of the operations or processes described in the embodiments of the present disclosure. For example, the processor executes the computer readable instructions to control the gas cooling pipeline 500 to cool the formed product with gas according to the mold opening displacement detected by the displacement sensor 400. In some embodiments, the controller 600 can be a PLC (Programmable Logic Controller). It should be understood that the present application is not limited thereto, and the controller can be a device known in the art capable of executing computer readable instructions or programs. The communication connection includes wired connection through a line and wireless connection through a wireless link (e.g., Bluetooth, WiFi, cellular communication, etc.).

[0046] In some embodiments, the controller 600 is configured to send an opening instruction to the electromagnetic valve 520 when the mold opening displacement detected by the displacement sensor 400 reaches a set threshold value, so that the nozzle 510 blows out gas for cooling the formed product. For example, the set threshold value can be 5 mm, so that by blowing gas to the polylactic acid formed product immediately after mold opening, the deformation caused by uneven heat dissipation and slow heat dissipation speed during mold opening is reduced, thereby effectively improving the quality of the product; and the cooling time is reduced, thereby improving the production efficiency. It should be understood that the present application is not limited thereto, and the set threshold value can be set according to the needs of actual application. In an alternative embodiment, the controller 600 is set to close the electromagnetic valve 520 after a predetermined time (e.g., 0.5 s) after the mold is opened to position.

[0047] In some embodiments, as shown in Figure 2 The nozzle comprises: upper layer nozzles, illustrated as a first columnar gas flow nozzle 511 and a second columnar gas flow nozzle 512, arranged on the molding surface of the fixed mold and close to the upper side; lower layer nozzles, illustrated as a first conical gas flow nozzle 515 and a second conical gas flow nozzle 516, arranged on the molding surface of the fixed mold and close to the lower side; and middle layer nozzles, illustrated as a third columnar gas flow nozzle 513 and a fourth columnar gas flow nozzle 514, arranged in the middle of the molding surface of the fixed mold, between the upper layer nozzles and the lower layer nozzles. In some embodiments, the upper layer nozzles and the middle layer nozzles are configured to spray columnar gas flow, and the lower layer nozzles are configured to spray conical gas flow. The columnar gas flow can quickly remove the residual heat at the bottom of the formed product and uniformly cool the side wall structure; and the conical gas flow can cover the complex curved surface of the formed product.

[0048] In some embodiments, as shown in Figure 2As shown, the first and second columnar airflow nozzles 511 and 512 are aligned in the horizontal direction and spaced apart by a predetermined distance. The third and fourth columnar airflow nozzles 513 and 514 are aligned in the vertical direction and spaced apart by a predetermined distance, for example, with the injection port 101 therebetween. The first and second conical airflow nozzles 515 and 516 are aligned in the horizontal direction and spaced apart by a predetermined distance. In this way, the multi-stage airflow nozzles are arranged along the deep cavity structure of the electric energy metering box, covering the deep cavity bottom, sidewall and rib area. As shown, Figure 1 As shown, the main gas path of the gas cooling pipeline 500 is connected to a high-pressure gas source (not shown), and an electromagnetic valve 520 and a pressure regulating valve 530 are connected in series in the gas path.

[0049] When the mold opening command is issued, the displacement sensor 400 collects the displacement data of the movable mold 200 in real time and transmits it to the controller 600. When the mold opening displacement detected by the displacement sensor 400 exceeds the set threshold value, the controller 600 sends an opening command (for example, a pulse signal) to the electromagnetic valve 520, thereby opening the gas valve. Further, the controller 600 can be configured to send an opening command to the electromagnetic valve 520 and a first pressure regulating command to the pressure regulating valve 530 when the mold opening displacement detected by the displacement sensor 400 reaches a first threshold value (for example, 50 mm), so as to spray gas at a first gas pressure (for example, 0.6 MPa). When the mold opening displacement detected by the displacement sensor 400 reaches a second threshold value (for example, 100 mm), the controller 600 sends a second pressure regulating command to the pressure regulating valve 530, so as to spray gas at a second gas pressure (for example, 0.5 MPa). Alternatively, the controller 600 can be further configured to send a third pressure regulating command to the pressure regulating valve 530 when the mold opening displacement detected by the displacement sensor 400 reaches a third threshold value (for example, 200 mm), so as to spray gas at a third gas pressure (for example, 0.4 MPa). In this case, the first threshold value, the second threshold value, the third threshold value, the first gas pressure, the second gas pressure and the third gas pressure are exemplified, but those skilled in the art should understand that the present application is not limited thereto, and appropriate changes can be made according to actual application requirements.

[0050] In some embodiments, the controller 600 can be configured to only enable the upper nozzles (i.e., nozzles 511 and 512) to spray gas when the mold opening displacement detected by the displacement sensor 400 is between the first threshold value and the second threshold value, to further enable the middle nozzles (i.e., nozzles 513 and 514) to spray gas when the mold opening displacement detected by the displacement sensor reaches the second threshold value, and to further enable the lower nozzles (i.e., nozzles 515 and 516) to spray gas when the mold opening displacement detected by the displacement sensor reaches the third threshold value.

[0051] Thus, in the above exemplary embodiments, the device of the present application performs hierarchical pressure control: in the first stage (50-100 mm stroke of mold opening), the upper layer nozzles are enabled, high pressure pulse mode (0.6 MPa) is adopted, and the residual heat of the formed product such as the bottom of the electric energy metering box is quickly purged; in the second stage (100-200 mm stroke of mold opening), the middle layer nozzles are enabled, and the mode is switched to medium pressure mode (0.5 MPa), and uniform cooling of the side wall structure is continued; in the third stage (200 mm to fully open), the lower layer nozzles are enabled, and the mode is switched to low pressure mode (0.4 MPa), and the complex curved surface is covered. Thus, uniform blowing cooling can be performed on each part of the formed product such as the electric energy metering box, deformation caused by uneven cooling of the box body is avoided, and after the electric energy metering box is cooled and formed, deformation caused by uneven force during mold removal can be effectively avoided.

[0052] In some embodiments, the device further comprises a temperature sensor (not shown) for detecting the temperature of the formed product, and the controller 600 is configured to send a closing instruction to the electromagnetic valve 520 to close the air flow of the nozzle when the temperature detected by the temperature sensor reaches a preset threshold value (i.e. the cooling end cooling temperature). In some embodiments, the temperature sensor can be a thermocouple, a thermistor, a resistance temperature detector (RTD), an integrated temperature sensor, etc., or other sensors known in the art that can detect the temperature of the formed product. In some embodiments, the temperature sensor has a range of 0-200°C.

[0053] In the exemplary embodiments, when the temperature sensor detects that the temperature of the injection molded workpiece has decreased to 60°C, the controller 600 sends a closing instruction, the electromagnetic valve 520 is powered off, and the air valve is closed. That is, in the exemplary embodiments, the cooling end temperature of the polylactic acid injection molded product is accurately controlled at 60°C. This is because the glass transition temperature of polylactic acid is about 60°C. When the temperature is higher than the glass transition temperature, the polylactic acid is in a high-elastic state, and the molecular chain segments can move relatively freely. At this time, the material is soft and prone to deformation. When the temperature decreases below the glass transition temperature, the movement ability of the polylactic acid molecular chain segments is greatly reduced, and the material becomes hard and brittle, and is not prone to deformation.

[0054] During the injection molding process, the polylactic acid material is rapidly cooled from high temperature, and there are differences in cooling rates at different parts, resulting in thermal stress inside the material. For example, the area close to the surface of the mold will preferentially cool and shrink, while the internal area will still be at a higher temperature and the shrinkage will be limited, resulting in tensile stress, while the internal area will generate compressive stress. The formula for calculating thermal stress is shown in formula (1-1):

[0055] σ=E·α·ΔT (1-1)

[0056] In the formula:

[0057] σ - thermal stress;

[0058] E - elastic modulus;

[0059] a - thermal expansion coefficient;

[0060] ΔT - temperature gradient;

[0061] For example, polylactic acid, its elastic modulus E is 3 x 10 9 Pa, thermal expansion coefficient a is 6 x 10 - 5 / ℃. The injection temperature is 120℃, if the cooling end temperature is 50℃, 60℃, 70℃, 80℃ respectively, then the corresponding ΔT is 70℃, 60℃, 50℃, 40℃. Through the analysis and calculation of different cooling end temperature stress as shown in Table 1.

[0062] Table 1: Stress calculation results of different cooling end temperature

[0063]

[0064] Through the finite element analysis software COMSOL to simulate the stress and strain of polylactic acid electric energy metering box model, through the combination of temperature field and force field to carry out multi-physical field simulation, set different cooling end temperature in the model, respectively 56℃, 58℃, 60℃, 62℃, 64℃, and calculate and analyze the corresponding internal stress distribution and size. For the actual deformation serious situation, focus on the deformation serious data collection and analysis. Figure 4 The polylactic acid electric energy metering box front cover stress result graph is shown.

[0065] Using origin software to draw point line graph (as Figure 5 shown) of different cooling end temperature and stress data and analysis. From Figure 4 it can be seen that the maximum internal stress value at 60℃ is significantly lower than other temperatures, and the stress distribution is more uniform.

[0066] Therefore, from the internal stress calculation, experimental verification and simulation analysis, it can be seen that by setting different cooling end point temperatures, the internal stress distribution in the electric energy metering box is calculated and compared. When the cooling end point temperature is 50°C, the internal stress is relatively large, mainly concentrated in the stress concentration areas such as the corners and reinforcing ribs of the electric energy metering box, and the maximum internal stress value can reach more than 20MPa. When the cooling end point temperature is 70°C or 80°C, the internal stress is relatively small, but the electric energy metering box has not yet been fully shaped, and size instability may occur in the subsequent use process. When the cooling end point temperature is 60°C, the internal stress distribution is relatively uniform and within a reasonable range, and the maximum internal stress value is controlled at about 10MPa. It can not only ensure the dimensional stability and mechanical properties of the material, but also avoid the brittleness problem caused by excessive cooling, and also ensure the cooling efficiency and meet the production efficiency demand. Therefore, the exemplary embodiment adopts 60°C as the cooling end point temperature, which is the choice made by the inventors after comprehensive consideration.

[0067] According to the above embodiment, a method for promoting the cooling and shaping of a polylactic acid molded product is obtained, which comprises: detecting the mold opening displacement of a movable mold relative to a fixed mold by a displacement sensor, wherein the displacement sensor is arranged on the movable mold, at least one molding surface of the fixed mold is provided with a nozzle and a gas path communicating with the nozzle, and an electromagnetic valve is arranged in the gas path; and controlling the use of gas in the gas cooling pipe for cooling the molded product by a controller according to the mold opening displacement detected by the displacement sensor.

[0068] In some embodiments, the controller sends an opening instruction to the electromagnetic valve when the mold opening displacement detected by the displacement sensor reaches a set threshold value, so that the nozzle blows out gas for cooling the molded product.

[0069] In some embodiments, the method comprises: when the mold opening displacement detected by the displacement sensor reaches a first threshold value, sending an opening instruction to the electromagnetic valve and a first pressure regulating instruction to the pressure regulating valve by the controller to blow out gas flow at a first gas pressure; when the mold opening displacement detected by the displacement sensor reaches a second threshold value, sending a second pressure regulating instruction to the pressure regulating valve by the controller to blow out gas flow at a second gas pressure, the second gas pressure being lower than the first gas pressure, and the second threshold value being greater than the first threshold value.

[0070] In some embodiments, the method further comprises: when the mold opening displacement detected by the displacement sensor reaches a third threshold value, sending a third pressure regulating instruction to the pressure regulating valve by the controller to blow out gas flow at a third gas pressure, the third gas pressure being less than the second gas pressure, and the third threshold value being greater than the second threshold value.

[0071] In some embodiments, the method includes: when the mold opening displacement detected by the displacement sensor is between the first threshold and the second threshold, only enabling the upper nozzle to spray airflow through the controller; when the mold opening displacement detected by the displacement sensor reaches the second threshold, further enabling the middle nozzle to spray airflow through the controller; when the mold opening displacement detected by the displacement sensor reaches the third threshold, further enabling the lower nozzle to spray airflow through the controller.

[0072] In some embodiments, the method further includes: detecting the temperature of the molded product by a temperature sensor, and sending a closing instruction to the solenoid valve by a controller to close the airflow of the nozzle when the temperature detected by the temperature sensor reaches a preset threshold.

[0073] In some embodiments, the method further comprises: forcibly closing the solenoid valve when the temperature is greater than 120° C. to prevent thermal degradation of the material. In some embodiments, the method further comprises: determining a hardware failure when the detection signal of the displacement sensor is less than 4 mA, triggering an alarm and shutting down the machine.

[0074] In some embodiments, the controller is programmed to execute a program to perform any one of the operations or processes in the above method. Figure 3 As shown, in an exemplary embodiment, the processing performed by the controller includes: S301, reading the current absolute position of the movable mold through the displacement sensor; S302, judging whether the mold is in the mold opening state based on the current absolute position, if not, recording the absolute position (S304) and returning to processing S301, if yes, proceeding to processing S303 and S305: recording the absolute position and measuring the temperature of the current workpiece (i.e., the polylactic acid molded product); S306, judging whether the workpiece temperature is lower than 60°C, if not, setting the air valve switch (i.e., the solenoid valve) to the open state (S308), thereby dispensing cooling gas through the nozzle for cooling, if yes, entering processing S307 and S309: setting the air valve switch to the closed state and reading the current absolute position; S310, judging whether the absolute position is zero, if not, returning to S309 to continue reading the current absolute position, if yes, entering S311, recording the absolute position.

[0075] Although the present invention is specifically described in this disclosure using a polylactic acid electric energy metering box as an example, it should be understood that the present invention can also be applied to the cooling and shaping of other polylactic acid molded products.

[0076] Those skilled in the art should understand that the above disclosure is only an example of the embodiments of the present application, and the scope of the right claimed by the present application is not limited thereto. Various modifications, changes, replacements and other changes can be made to the embodiments of the present disclosure without departing from the spirit of the present disclosure, and these changes are also within the scope covered by the claims of the present application.

Claims

1. An apparatus for facilitating the cooling and setting of a polylactic acid molded article, the molded article being an electrical energy metering box, characterized by, The injection molding machine comprises: a fixed mold; a movable mold arranged to be movable relative to the fixed mold and defining a cavity with the fixed mold for accommodating a polylactic acid material; an opening and closing mechanism operatively connected with the movable mold for moving the movable mold to open or close the mold; a displacement sensor arranged on the movable mold for detecting an opening displacement amount; a gas cooling pipeline comprising a nozzle arranged on at least one molding surface of the fixed mold and an electromagnetic valve arranged in a gas path in communication with the nozzle; and a controller communicatively connected with the displacement sensor and the electromagnetic valve and configured to control the gas cooling pipeline to cool the molded product with gas according to the opening displacement detected by the displacement sensor; wherein the controller is configured to send an opening instruction to the electromagnetic valve when the opening displacement detected by the displacement sensor reaches a set threshold value, so that the nozzle blows out gas for cooling the molded product; wherein the nozzle comprises: an upper nozzle arranged on the molding surface of the fixed mold and close to the upper side; a lower nozzle arranged on the molding surface of the fixed mold and close to the lower side; and a middle nozzle arranged on the molding surface of the fixed mold and between the upper nozzle and the lower nozzle; and the upper nozzle and the middle nozzle are configured to blow out columnar gas flow, and the lower nozzle is configured to blow out conical gas flow; wherein a pressure regulating valve is arranged in the gas cooling pipeline corresponding to each nozzle; the controller is configured to: send an opening instruction to the electromagnetic valve and a first pressure regulating instruction to the pressure regulating valve when the opening displacement detected by the displacement sensor reaches a first threshold value, so that the gas flow is blown out at a first gas pressure; send a second pressure regulating instruction to the pressure regulating valve when the opening displacement detected by the displacement sensor reaches a second threshold value, so that the gas flow is blown out at a second gas pressure, the second gas pressure being lower than the first gas pressure, and the second threshold value being greater than the first threshold value; send a third pressure regulating instruction to the pressure regulating valve when the opening displacement detected by the displacement sensor reaches a third threshold value, so that the gas flow is blown out at a third gas pressure, the third gas pressure being lower than the second gas pressure, and the third threshold value being greater than the second threshold value; and the controller is further configured to: only open the electromagnetic valve corresponding to the upper nozzle when the opening displacement detected by the displacement sensor is between the first threshold value and the second threshold value, so as to enable the upper nozzle to blow out the gas flow; further open the electromagnetic valve corresponding to the middle nozzle when the opening displacement detected by the displacement sensor reaches the second threshold value, so as to further enable the middle nozzle to blow out the gas flow; further open the electromagnetic valve corresponding to the lower nozzle when the opening displacement detected by the displacement sensor reaches the third threshold value, so as to further enable the lower nozzle to blow out the gas flow. the upper nozzle comprises a first columnar gas flow nozzle and a second columnar gas flow nozzle, and the first columnar gas flow nozzle and the second columnar gas flow nozzle are aligned in the horizontal direction and spaced apart by a predetermined distance; and / or 2. The apparatus of claim 1, wherein, ​ The middle layer nozzle comprises a third columnar gas flow nozzle and a fourth columnar gas flow nozzle, and the third columnar gas flow nozzle and the fourth columnar gas flow nozzle are aligned in a vertical direction and are spaced apart by a predetermined distance; and / or The lower layer nozzle comprises a first conical gas flow nozzle and a second conical gas flow nozzle, and the first conical gas flow nozzle and the second conical gas flow nozzle are aligned in a horizontal direction and are spaced apart by a predetermined distance.

3. The apparatus of claim 1, wherein, The device further comprises a temperature sensor for detecting the temperature of the molded product, and the controller is configured to send a closing instruction to the electromagnetic valve to close the gas flow of the nozzle when the temperature detected by the temperature sensor reaches a preset threshold.

4. A method of facilitating the cooling and setting of a polylactic acid molded article using the apparatus according to any one of claims 1 to 3, characterized by, Comprise: Detecting the mold opening displacement of the movable mold relative to the fixed mold through a displacement sensor, wherein the displacement sensor is arranged on the movable mold, and at least one forming surface of the fixed mold is provided with a gas cooling pipeline; Controlling the gas cooling pipeline to cool the molded product with gas according to the mold opening displacement detected by the displacement sensor through the controller.

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