CN107589154A - Melt sensor and Mo Nei melt sensor-based systems in a kind of mould - Google Patents

Abstract

The invention discloses an in-mold melt sensor and an in-mold melt sensing system. The in-mold melt sensor includes: an in-mold capacitor (1) and a capacitance measuring device (2), wherein the in-mold capacitor (1) is composed of an electrode plate arranged on the fixed plate of the mold and a movable plate of the mold, and the electrode plate There is an insulating layer between the fixed template, and the electrode plate is in contact with the cavity of the mould; the capacitance measuring device (2) is used to convert the capacitance signal in the in-mold capacitor into a corresponding voltage signal, and the voltage signal is used for online detection of the entire The state of the melt in the mold cavity during injection molding. The in-mold melt sensor provided by the present invention can use the capacitance change brought about by melt injection to detect the state of the melt on-line during the entire injection molding process, and the detected melt state information is continuous and abundant. Moreover, after the in-mold melt sensor is installed, the mold cavity is still a metal cavity, which does not reduce the strength of the mold cavity and has a wide range of applications.

Description

An in-mold melt sensor and an in-mold melt sensing system

technical field

The invention relates to the technical field of mold detection, in particular to an in-mold melt sensing system and an in-mold melt sensing system.

Background technique

With the sublimation of fierce competition in the product market, advocating high efficiency, energy saving, environmental protection, and low cost has become the magic weapon and foundation for enterprises to win in the competition. One of the key links is the efficiency and quality monitoring of the production process of injection molding products. High intelligence of control and control, low cost expenditure, effective resource utilization and other aspects put forward higher, more competitive, smarter and more automated requirements.

During the entire injection molding process, the state of the melt in the cavity changes greatly, and these changes have a decisive impact on the quality of the product. Therefore, the detection of the melt state, especially the detection of the state in the cavity, plays a vital role in predicting and controlling product quality.

At this stage, the technology of shooting glass cavity with camera and ultrasonic pulse reflection method are generally used to detect the state of the melt during the injection molding process. However, in the technology of shooting glass cavity with camera, the melt needs to pass through the glass cavity instead of the traditional one. The metal mold cavity reduces the strength of the mold cavity, which seriously affects the application of this technology; while in the ultrasonic pulse reflection method, the installation position of the sensor is limited, and the melt state information provided is very limited and discrete.

Contents of the invention

In order to solve the problem that the existing technology of capturing glass mold cavity with a camera is limited in scope and the information collected by the ultrasonic pulse reflection method is limited, an embodiment of the present invention provides an in-mold melt sensor and an in-mold melt sensing system. Described technical scheme is as follows:

On the one hand, an embodiment of the present invention provides an in-mold melt sensor, including:

The in-mold capacitor is composed of an electrode plate arranged on the fixed template of the mold and a movable template of the mold, an insulating layer is arranged between the electrode plate and the fixed template, and the electrode plate and the mold of the mold Cavity contact;

A capacitance measuring device, connected to the in-mold capacitor, is used to convert the capacitance signal in the in-mold capacitor into a corresponding voltage signal, and the voltage signal is used for online detection of melting in the mold cavity during the entire injection molding process. state of the body.

In the above-mentioned in-mold melt sensor in the embodiment of the present invention, the capacitance measuring device includes:

A capacitance-to-voltage converter, connected to the in-mold capacitor, used to convert the capacitance signal on the in-mold capacitor into a corresponding analog voltage signal during the entire injection molding process;

An analog-to-digital conversion device, connected to the capacitive voltage converter, for converting the analog voltage signal collected by the capacitive voltage converter into a corresponding digital voltage signal;

The data acquisition device is respectively connected with the analog-to-digital conversion device and the processor, and is used to collect the digital voltage signal generated by the analog-to-digital conversion device and transmit it to the processor for the processor to detect online during the entire injection molding process. Describe the state of the melt in the cavity.

In the above-mentioned in-mold melt sensor in the embodiment of the present invention, the electrode plate is in contact with the end of the mold cavity away from the injection port, and the injection port communicates with the mold cavity and is used for supplying the mold to the A hole through which melt is injected into the mold cavity.

In the above-mentioned in-mold melt sensor in the embodiment of the present invention, the electrode plate is made of mold steel.

In the above-mentioned in-mold melt sensor in the embodiment of the present invention, the insulating layer is made of alumina ceramics or zirconia ceramics.

In the above-mentioned in-mold melt sensor in the embodiment of the present invention, the capacitance measuring device is connected to the electrode plate through an antistatic induction wire.

On the other hand, an embodiment of the present invention provides an in-mold melt sensing system, including:

The in-mold capacitor is composed of an electrode plate arranged on the fixed template of the mold and a movable template of the mold, an insulating layer is arranged between the electrode plate and the fixed template, and the electrode plate and the mold of the mold Cavity contact;

a capacitance measuring device, connected to the in-mold capacitor, for converting the capacitance signal in the in-mold capacitor into a corresponding voltage signal;

A processor, connected to the capacitance measuring device, is used for online detection of the state of the melt in the mold cavity during the entire injection molding process according to the voltage signal provided by the capacitance measuring device.

In the above-mentioned in-mold melt sensing system in the embodiment of the present invention, the capacitance measuring device includes:

A capacitance-to-voltage converter, connected to the in-mold capacitor, used to convert the capacitance signal on the in-mold capacitor into a corresponding analog voltage signal during the entire injection molding process;

An analog-to-digital conversion device, connected to the capacitive voltage converter, for converting the analog voltage signal collected by the capacitive voltage converter into a corresponding digital voltage signal;

The data acquisition device is respectively connected with the analog-to-digital conversion device and the processor, and is used to collect the digital voltage signal generated by the analog-to-digital conversion device and transmit it to the processor for the processor to detect the entire injection molding process online. The state of the melt in the mold cavity during the molding process.

In the above-mentioned in-mold melt sensing system in the embodiment of the present invention, the insulating layer is made of alumina ceramics or zirconia ceramics.

In the above-mentioned in-mold melt sensing system according to the embodiment of the present invention, the capacitance measuring device is connected to the electrode plate through an antistatic induction wire.

The beneficial effects brought by the technical solution provided by the embodiments of the present invention are:

The in-mold melt sensor is formed by an in-mold capacitor and a capacitance measuring device, wherein the in-mold capacitor is composed of an electrode plate arranged on the fixed template of the mold and a movable template of the mold, an insulating layer is arranged between the electrode plate and the fixed template, and the electrodes The plate is in contact with the mold cavity of the mold, so that when the melt is injected into the mold cavity, the capacitance signal of the in-mold capacitor will change accordingly, and the capacitance measuring device converts the capacitance signal in the in-mold capacitor into a corresponding voltage signal, the voltage The signal can be used to detect the state of the melt in the mold cavity online during the entire injection molding process. In this way, the in-mold melt sensor can use the capacitance change brought about by melt injection to detect the state of the melt online during the entire injection molding process, and the detected melt state information is continuous and rich. Moreover, after the in-mold melt sensor is installed, the mold cavity is still a metal cavity, which will not reduce the strength of the cavity as in the technology of taking pictures of the glass cavity with a camera, and has a wide range of applications.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained based on these drawings without creative effort.

Fig. 1 is the structural representation of a kind of mold that the embodiment of the present invention provides;

Fig. 2 is a schematic structural diagram of an in-mold melt sensor provided in Embodiment 1 of the present invention;

Fig. 3 is a diagram of detection results of voltage signals in an injection molding process provided by Embodiment 1 of the present invention;

4 is a schematic structural diagram of a capacitance measuring device provided in Embodiment 1 of the present invention;

Fig. 5 is a schematic structural diagram of an in-mold melt sensing system provided by Embodiment 2 of the present invention;

FIG. 6 is a schematic structural diagram of a capacitance measuring device provided in Embodiment 2 of the present invention.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the implementation manner of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Before introducing the embodiment of the present invention in detail, first introduce the application scenario of the present application, referring to Fig. 1, the in-mold melt sensor is applied in an injection molding mold, referring to Fig. 1, the injection molding mold may include: a fixed template 100 , the movable template 200, and the mold cavity 300 between the fixed template 100 and the movable template 200 for forming products. The fixed module 100 is generally provided with an injection port (not shown in the drawings) communicating with the mold cavity 300 for evenly injecting non-conductive melt into the mold cavity 300 , such as plastic.

Embodiment one

An embodiment of the present invention provides an in-mold melt sensor, which is suitable for various non-conductive melts, as shown in FIG. 2 , including: an in-mold capacitor 1 and a capacitance measuring device 2 .

Wherein, referring to FIG. 1 , the in-mold capacitor 1 is composed of an electrode plate 11 arranged on the fixed template 100 of the mold and a movable template 200 of the mould, an insulating layer 12 is arranged between the electrode plate 11 and the fixed template 100, and the electrode plate 11 In contact with the cavity 300 of the mould. In this embodiment, the two poles of the in-mold capacitor 1 are the electrode plate 11 and the movable template 200 , one side of the electrode plate 11 is in contact with the mold cavity 300 and the other side is isolated from the fixed template 100 by the insulating layer 12 .

The capacitance measuring device 2 is connected with the in-mold capacitor 1, and is used to convert the capacitance signal in the in-mold capacitor 1 into a corresponding voltage signal, and the voltage signal is used for online detection of the state of the melt in the mold cavity 300 during the entire injection molding process . In practical applications, the voltage signal collected by the capacitance measuring device 2 can be transmitted to a processor or a computer for it to calculate the state of the melt according to a preset algorithm.

In this embodiment, the entire injection molding process generally includes: mold closing (or called mold clamping), injection molding, pressure maintaining, cooling, mold opening and other stages. That is, the polymer particles are heated in the barrel to reach a fluid state (melt) and have excellent plasticity, and are filled with the mold cavity 300 under the push of the screw, and the melt is released from the mold after cooling and shaping. Although the above process takes a short time, the state of the melt in the mold cavity 300 changes greatly, and these changes have a decisive impact on the quality of the product. Therefore, the detection of the state of the melt, especially the detection of the state in the cavity 300, plays a vital role in predicting and controlling product quality.

In this embodiment, the in-mold capacitor 1 is formed by the electrode plate 11 arranged on the fixed template 100 of the mold and the movable template 200 of the mould. The fixed template 100 and the movable template 200 are respectively the two poles of the capacitor 1 in the mold. The capacitance C of 1 can be calculated according to the following formula:

Among them, ε is the dielectric constant of the medium between the two poles of the capacitor, A is the relative area of the two poles of the capacitor, and d is the relative distance between the two poles of the capacitor.

After the mold is closed, the A and d of the capacitance of the in-mold capacitor 1 are both constant values, and the state of the mold cavity 300 changes from air to a part of the air and a part of the melt until the mold cavity 300 is completely melted. During the above process , the dielectric constant of the medium in the capacitance of the in-mold capacitor 1 has been changing, and the capacitance C of the in-mold capacitor 1 changes linearly with the dielectric constant. Therefore, according to the entire injection molding process, at different stages, the in-mold The change of the capacitance of the capacitor 1 is used to obtain the state of the melt in the mold cavity 300 .

Specifically, during the entire injection molding cycle, the voltage signal measured by the capacitance measuring device 2 varies with time as shown in FIG. 3 .

In the injection phase, as the melt is injected into the mold cavity 300, the air medium between the capacitor poles of the in-mold capacitor 1 is quickly replaced by the melt, and the voltage signal increases significantly. Through this in-mold melt sensor, the flow position x _t of the melt in the mold cavity 300 at the current sampling time t is detected, and the difference calculation Among them, x _t-1 is the melt position at the last sampling time t-1, and ΔT is the sampling period. From this, the melt flow velocity v _t at the current sampling time t can be obtained, which provides a basis for closed-loop control of a uniform and constant flow velocity. Measurement basis.

In the pressure-holding stage, the slope of the voltage signal changes significantly and rises slowly. This is because only a small amount of melt continues to be pressed (injected) into the cavity 300 after the cavity 300 is filled to supplement the solidification and shrinkage of the melt formed. space (holding pressure). In practical applications, the total mass of the melt can be calculated through the voltage signals of the injection stage and the pressure holding stage. Specifically, when just entering the injection stage, take the voltage signal U0; when the pressure holding stage ends, take the maximum voltage signal U1 (because when the voltage signal reaches the maximum, the melt will not be injected, and the cooling stage , the voltage signal will have a slight downward trend), calculate the difference ΔU between U1 and U0, and weigh the total mass of the melt used in this injection molding. Count the relationship between the ΔU of multiple annotations and the total mass of the melt, and simulate the corresponding model. In the subsequent detection process, only need to calculate ΔU, and then calculate the corresponding total mass of the melt according to the preset model. quality up.

In addition, the pressure holding time can also be detected during the holding pressure stage. The setting of the holding pressure time is to control the time when the holding pressure takes effect. If the holding time is not enough, the size and weight of the product will be unstable. But if the holding time is too long, energy will be wasted. In practical applications, ΔU can be used to set the holding time. Specifically, firstly, in a comment, without setting the holding time, a ΔU is obtained, and then the holding time is gradually increased at preset intervals (for example, 1 second). By obtaining multiple ΔU, when the obtained ΔU value remains unchanged, the total increased time at this time is the dwell time.

During the cooling phase, the voltage signal changes more smoothly with a slight downward trend. The reason is that the melt becomes solid after cooling and solidification on the one hand, and on the other hand, a tiny air layer is formed in the mold cavity 300 . Due to the output voltage signal of the in-mold melt sensor, it also changes with the progress of the solidification process. Therefore, based on the output voltage signal of the in-mold melt sensor, the solidification model of the melt in the cooling stage can be established, the solidification rate can be detected, the end time of the solidification process can be determined, and then the optimal cooling time can be estimated to improve injection molding efficiency and save energy.

Optionally, referring to FIG. 4, the capacitance measuring device 2 may include:

The capacitance-to-voltage converter 21 is connected with the in-mold capacitor 1 and is used for converting the capacitance signal on the in-mold capacitor 1 into a corresponding analog voltage signal during the whole injection molding process.

The analog-to-digital conversion device 22 is connected with the capacitive voltage converter 21, and is used for converting the analog voltage signal collected by the capacitive voltage converter 21 into a corresponding digital voltage signal.

The data acquisition device 23 is connected with the analog-to-digital conversion device 22 and the processor (also can be a computer) respectively, and is used to collect the digital voltage signal generated by the analog-to-digital conversion device 22, and transmits it to the processor for online detection of the entire The state of the melt in the mold cavity 300 during the injection molding process.

In this embodiment, the capacitance measuring device 2 has a simple structure and strong practicability.

Optionally, the electrode plate 11 is in contact with an end of the cavity 300 away from the injection port, and the injection port is a through hole communicating with the cavity 300 and used for the mold to inject melt into the cavity 300 .

In this embodiment, the melt of the cavity 300 is generally injected from the injection port, and flows in the cavity 300 until the entire cavity 300 is filled, and the end of the cavity 300 away from the injection port is the last part of the cavity 300 When the melt reaches the last filling point of the cavity 300, the injection phase is over. Since the capacitance increase rate is very different between the injection stage and the pressure holding stage, the electrode plate 11 is set to be in contact with the end of the cavity 300 away from the injection port, that is, it covers the last filling point of the cavity 300, which can be used to detect the injection stage The transition time node between the pressure-holding phase and the pressure-holding phase.

Optionally, the electrode plate 11 can be made of mold steel material, that is, made of the same material as the fixed platen 100 and the movable platen 200 , thereby reducing the adverse effect on the mold caused by the installation of the melt sensor in the mold.

Optionally, the insulating layer 12 can be made of alumina ceramics or zirconia ceramics, so that the insulating effect is better, thereby ensuring the detection effect of the sensor.

Optionally, the capacitance measuring device 2 is connected to the electrode plate 11 through an antistatic induction wire, which can effectively reduce the interference of external static electricity on the measurement results of the sensor.

In the embodiment of the present invention, an in-mold melt sensor is constituted by an in-mold capacitor and a capacitance measuring device, wherein the in-mold capacitor is composed of an electrode plate arranged on the fixed platen of the mold and a movable platen of the mold, and a gap is arranged between the electrode plate and the fixed platen The insulating layer and the electrode plate are in contact with the cavity of the mold, so that when the melt is injected into the cavity, the capacitance signal of the in-mold capacitor will change accordingly, and the capacitance measuring device converts the capacitance signal in the in-mold capacitor into a corresponding voltage Signal, the voltage signal can be used to detect the state of the melt in the mold cavity online during the entire injection molding process. In this way, the in-mold melt sensor can use the capacitance change brought about by melt injection to detect the state of the melt online during the entire injection molding process, and the detected melt state information is continuous and rich. Moreover, after the in-mold melt sensor is installed, the mold cavity is still a metal cavity, which will not reduce the strength of the cavity as in the technology of taking pictures of the glass cavity with a camera, and has a wide range of applications.

Embodiment two

An embodiment of the present invention provides an in-mold melt sensor system, which uses the in-mold melt sensor described in Embodiment 1, see FIG. 5, the system may include: an in-mold capacitor 1, a capacitance measuring device 2, and Processor 3.

Referring to Fig. 1, the in-mold capacitor 1 is composed of an electrode plate 11 arranged on the fixed template 100 of the mold and a movable template 200 of the mold, an insulating layer 12 is arranged between the electrode plate 11 and the fixed template 100, and the electrode plate 11 and the mold The mold cavity 300 is in contact. In this embodiment, the two poles of the in-mold capacitor 1 are the electrode plate 11 and the movable template 200 , one side of the electrode plate 11 is in contact with the mold cavity 300 and the other side is isolated from the fixed template 100 by the insulating layer 12 .

The capacitance measuring device 2 is connected with the in-mold capacitor 1, and is used to convert the capacitance signal in the in-mold capacitor 1 into a corresponding voltage signal, and the voltage signal is used for online detection of the state of the melt in the mold cavity 300 during the entire injection molding process .

The processor 3 is connected with the capacitance measuring device 2 and is used for online detection of the state of the melt in the mold cavity 300 during the entire injection molding process according to the voltage signal provided by the capacitance measuring device 2 .

In this embodiment, the entire injection molding process generally includes: mold closing (or called mold clamping), injection molding, pressure maintaining, cooling, mold opening and other stages. That is, the polymer particles are heated in the barrel to reach a fluid state (melt) and have excellent plasticity, and are filled with the mold cavity 300 under the push of the screw, and the melt is released from the mold after cooling and shaping. Although the above process takes a short time, the state of the melt in the mold cavity 300 changes greatly, and these changes have a decisive impact on the quality of the product. Therefore, the detection of the state of the melt, especially the detection of the state in the cavity 300, plays a vital role in predicting and controlling product quality.

In this embodiment, the in-mold capacitor 1 is formed by the electrode plate 11 arranged on the fixed template 100 of the mold and the movable template 200 of the mould. The fixed template 100 and the movable template 200 are respectively the two poles of the capacitor 1 in the mold. The capacitance C of 1 can be calculated according to the following formula:

Among them, ε is the dielectric constant of the medium between the two poles of the capacitor, A is the relative area of the two poles of the capacitor, and d is the relative distance between the two poles of the capacitor.

After the mold is closed, the A and d of the capacitance of the in-mold capacitor 1 are both constant values, and the state of the mold cavity 300 changes from air to a part of the air and a part of the melt until the mold cavity 300 is completely melted. During the above process , the dielectric constant of the medium in the capacitance of the in-mold capacitor 1 has been changing, and the capacitance C of the in-mold capacitor 1 changes linearly with the dielectric constant. Therefore, according to the entire injection molding process, at different stages, the in-mold The change of the capacitance of the capacitor 1 is used to obtain the state of the melt in the mold cavity 300 .

In this embodiment, how the processor 3 obtains the state of the melt through the voltage signal has been described in detail in Embodiment 1, and will not be repeated here.

Optionally, referring to FIG. 6, the capacitance measuring device 2 may include:

The capacitance-to-voltage converter 21 is connected with the in-mold capacitor 1 and is used for converting the capacitance signal on the in-mold capacitor 1 into a corresponding analog voltage signal during the whole injection molding process.

The analog-to-digital conversion device 22 is connected with the capacitive voltage converter 21, and is used for converting the analog voltage signal collected by the capacitive voltage converter 21 into a corresponding digital voltage signal.

The data acquisition device 23 is connected with the analog-to-digital conversion device 22 and the processor 3 respectively, and is used to collect the digital voltage signal generated by the analog-to-digital conversion device 22 and transmit it to the processor 3 for the processor 3 to detect the entire injection molding process online The state of the melt in the middle mold cavity 300.

In this embodiment, the capacitance measuring device 2 has a simple structure and strong practicability.

Optionally, the electrode plate 11 is in contact with an end of the cavity 300 away from the injection port, and the injection port is a through hole communicating with the cavity 300 and used for the mold to inject melt into the cavity 300 .

In this embodiment, the melt of the cavity 300 is generally injected from the injection port, and flows in the cavity 300 until the entire cavity 300 is filled, and the end of the cavity 300 away from the injection port is the last part of the cavity 300 When the melt reaches the last filling point of the cavity 300, the injection phase is over. Since the capacitance increase rate is very different between the injection stage and the pressure holding stage, the electrode plate 11 is set to be in contact with the end of the cavity 300 away from the injection port, that is, it covers the last filling point of the cavity 300, which can be used to detect the injection stage The transition time node between the pressure-holding phase and the pressure-holding phase.

Optionally, the electrode plate 11 can be made of mold steel material, that is, made of the same material as the fixed platen 100 and the movable platen 200 , thereby reducing the adverse effect on the mold caused by the installation of the melt sensor in the mold.

Optionally, the insulating layer 12 can be made of alumina ceramics or zirconia ceramics, so that the insulating effect is better, thereby ensuring the detection effect of the sensor.

Optionally, the capacitance measuring device 2 is connected to the electrode plate 11 through an antistatic induction wire, which can effectively reduce the interference of external static electricity on the measurement results of the sensor.

In the embodiment of the present invention, an in-mold melt sensing system is constituted by an in-mold capacitor, a capacitance measuring device, and a processor, wherein the in-mold capacitor is composed of an electrode plate arranged on the fixed platen of the mold and a movable platen of the mold, and the electrode plate and the movable platen of the mold are formed. There is an insulating layer between the fixed templates, and the electrode plate is in contact with the cavity of the mold, so that when the melt is injected into the cavity, the capacitance signal of the in-mold capacitor will change accordingly, and the capacitance measuring device will measure the capacitance of the in-mold capacitor The signal is converted into a corresponding voltage signal, which can be used to detect the state of the melt in the mold cavity online during the entire injection molding process. In this way, the in-mold melt sensing system can use the capacitance change brought about by melt injection to detect the state of the melt online during the entire injection molding process, and the detected melt state information is continuous and rich. Moreover, after the in-mold melt sensing system is installed, the mold cavity is still a metal cavity, which will not reduce the strength of the cavity as in the technology of taking pictures of the glass cavity with a camera, and has a wide range of applications.

The serial numbers of the above embodiments of the present invention are for description only, and do not represent the advantages and disadvantages of the embodiments.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (10)

1. An in-mold melt sensor, characterized in that, comprising: The in-mold capacitor (1) is composed of an electrode plate (11) arranged on the fixed template (100) of the mold and a movable template (200) of the mold, and the electrode plate (11) and the fixed template (100) An insulating layer (12) is arranged therebetween, and the electrode plate (11) is in contact with the mold cavity (300) of the mould; Capacitance measuring device (2), connected to the in-mold capacitor (1), used to convert the capacitance signal in the in-mold capacitor (1) into a corresponding voltage signal, and the voltage signal is used for online detection of the entire injection molding The state of the melt in the mold cavity (300) during the molding process. 2. in-mold melt sensor according to claim 1, is characterized in that, described capacitance measuring device (2), comprises: A capacitance-to-voltage converter (21), connected to the in-mold capacitor (1), used to convert the capacitance signal on the in-mold capacitor (1) into a corresponding analog voltage signal during the entire injection molding process; An analog-to-digital conversion device (22), connected to the capacitive voltage converter (21), for converting the analog voltage signal collected by the capacitive voltage converter (21) into a corresponding digital voltage signal; The data acquisition device (23) is connected with the analog-to-digital conversion device (22) and the processor respectively, and is used to collect the digital voltage signal generated by the analog-to-digital conversion device (22), and transmits it to the processor for processing The device detects the state of the melt in the mold cavity (300) online during the entire injection molding process. 3. The in-mold melt sensor according to claim 1, characterized in that, the electrode plate (11) is in contact with the end of the mold cavity (300) away from the injection port, and the injection port is connected to the mold cavity. The cavity (300) communicates and is used as a through hole for the mold to inject melt into the cavity (300). 4. The in-mold melt sensor according to any one of claims 1-3, characterized in that the electrode plate (11) is made of mold steel. 5. The in-mold melt sensor according to any one of claims 1-3, characterized in that the insulating layer (12) is made of alumina ceramics or zirconia ceramics. 6. The in-mold melt sensor according to any one of claims 1-3, characterized in that the capacitance measuring device (2) is connected to the electrode plate (11) through an antistatic induction wire. 7. An in-mold melt sensing system, characterized in that it comprises: The in-mold capacitor (1) is composed of an electrode plate (11) arranged on the fixed template (100) of the mold and a movable template (200) of the mold, and the electrode plate (11) and the fixed template (100) An insulating layer (12) is arranged therebetween, and the electrode plate (11) is in contact with the mold cavity (300) of the mould; a capacitance measuring device (2), connected to the in-mold capacitor (1), for converting the capacitance signal in the in-mold capacitor (1) into a corresponding voltage signal; A processor (3), connected to the capacitance measuring device (2), is used to detect the melt in the mold cavity (300) online during the entire injection molding process according to the voltage signal provided by the capacitance measuring device (2). status. 8. system according to claim 7, is characterized in that, described capacitance measuring device (2), comprises: A capacitance-to-voltage converter (21), connected to the in-mold capacitor (1), used to convert the capacitance signal on the in-mold capacitor (1) into a corresponding analog voltage signal during the entire injection molding process; An analog-to-digital conversion device (22), connected to the capacitive voltage converter (21), for converting the analog voltage signal collected by the capacitive voltage converter (21) into a corresponding digital voltage signal; A data acquisition device (23), connected to the analog-to-digital conversion device (22) and the processor (3) respectively, for collecting the digital voltage signal generated by the analog-to-digital conversion device (22), and transmitting to the processing In the device (3), the processor (3) is used to detect the state of the melt in the mold cavity (300) online during the entire injection molding process. 9. The system according to claim 7 or 8, characterized in that the insulating layer (12) is made of alumina ceramics or zirconia ceramics. 10. The system according to claim 7 or 8, characterized in that the capacitance measuring device (2) is connected to the electrode plate (11) through an antistatic induction wire.