CN116638720A - Plastic mold and injection molding method thereof - Google Patents

Abstract

The invention discloses a plastic mold and an injection molding method thereof, comprising a fixed plate and a moving plate, a first formwork is arranged at the bottom of the fixed plate, a supporting plate is arranged above the moving plate, and a supporting plate is arranged above the supporting plate A receiving plate is provided, a second formwork is provided above the receiving plate, a first core is provided in the first formwork, a second core is correspondingly provided on the second formwork, and the first core A cavity is formed between the second core and the top of the second core is provided with a mounting hole, the mounting hole is provided with a pressure sensor, the pressure sensor is flush with the top of the second core, the The side of the second template is provided with an air injection device. The invention can detect and calculate the pressure in the plastic mould, and speed up the demoulding time.

Description

Plastic mold and injection molding method thereof

technical field

The invention belongs to the technical field of moulds, and in particular relates to a plastic mold and an injection molding method thereof.

Background technique

Now, the injection molding process of plastic products is developing towards shortening the injection molding cycle and improving production efficiency. Generally, in order to improve production efficiency, in the injection molding process of injection molds, the plasticizing capacity is increased, the injection time is shortened, and the template moving speed is accelerated. In addition, Improvements to injection mold injection methods, mold clamping methods, and cooling efficiency methods have also been adopted to save time, shorten production cycles, and increase output.

The Chinese patent application number 2022109723710 discloses an injection molding production process for industrial injection molded parts, which includes the following steps: S1. Mold pretreatment: cleaning the injection mold of the injection molded parts, brushing the mold release agent and preheating; S2. Raw materials Selection and processing: select the raw materials of injection molding parts, mix them, and extrude them through a screw extruder for use; S3. Raw material injection: inject the raw materials processed by S2 into the mold pretreated by S1 through the nozzle, and the injection pressure is 60 -150Mpa, maintain for 20-30s; S4. Holding pressure: the nozzle of the injection molding machine continuously feeds material to the cavity, continuously applies pressure, and compacts the melt. The pressure in the holding stage is 75-95% of the maximum filling pressure, and the pressure is maintained 40-80kg/cm3, holding pressure time 30-60min; S5. Demolding; S6. Cleaning of injection molded parts and molds; S7. Spraying of injection molded parts. By pretreating the mold, this solution can not only increase the cleanliness of the mold and reduce the impact of dust and impurities on the injection molded parts, but also facilitate the demoulding of the injection molded parts after the raw materials are injection molded, which is conducive to increasing work efficiency.

The above patent can achieve the effect of increasing the demoulding rate, but it needs to wait for a certain period of time when demoulding. This period of time is waiting for the cavity temperature in the mold to cool to the specified temperature and the cavity pressure in the mold to stabilize. Only when the temperature cools down Demoulding can only be carried out when the cavity pressure inside the mold tends to be stable, otherwise it will cause difficulty in demoulding. The temperature factor can be detected by the temperature sensor, and it takes a long time to wait for the internal pressure to be close to the external pressure when the pressure is stable. To be considered stable, this will increase the demoulding time.

Contents of the invention

In order to solve the above problems, the present invention provides a plastic mold, including a fixed plate and a moving plate, the bottom of the fixed plate is provided with a first template, the top of the moving plate is provided with a support plate, and the top of the support plate is provided with There is a receiving plate, a second formwork is provided above the receiving plate, a first core is provided in the first formwork, a second core is correspondingly provided on the second formwork, the first core and A cavity is formed between the second cores, the top of the second core is provided with a mounting hole, and a pressure sensor is arranged in the mounting hole, the pressure sensor is flush with the top of the second core, and the first core is flush with the top of the second core. The side of the second template is provided with an air jet device.

Preferably, the first template is provided with a first cavity, the first cavity is provided with a first core plate, and the first core plate is provided with a plurality of first cores, and the second The template is provided with a second cavity, the second cavity is provided with a second core plate, and the second core plate is provided with a plurality of second cores corresponding to the first cores.

Preferably, an ejection mechanism is provided on the moving plate, and the ejection mechanism includes an ejection cylinder, a top plate and a thimble, the output end of the ejection cylinder is connected to the top plate, and an thimble is connected above the top plate, The thimble passes through the receiving plate and the first template to abut against the second template.

Preferably, the air injection device includes an air source and an air nozzle, the air nozzle protrudes from the surface of the second template, the first template is provided with a guide hole in conjunction with the air nozzle, and the air nozzle is provided with an air injection hole , the air injection hole is set towards the second core, and the air source is connected with the air injection nozzle.

Preferably, a circulation channel is provided in the receiving plate, one end of the circulation channel is connected to the air nozzle, the other end of the circulation channel is connected to the air source, and the end of the circulation channel close to the paint spray nozzle is provided with a sealing ring.

An injection molding method for a plastic mould, comprising the following steps;

S1. Injection filling, injecting plastic raw materials into the cavity of the mold until the inside of the mold cavity is injected to 90%-95%, and then stop the injection molding;

S2. Maintaining pressure, continuously applying pressure to the mold until the gate is cooled and closed;

S3, cooling and shaping, open the cooling water pipe, pour water into the circulating cooling water pipe on the first template and the second template to cool until the mold temperature drops to the specified temperature;

S4. Calculate the cavity pressure and wait for the pressure in each cavity to stabilize;

S5. The plastic is demoulded, and the mold is separated by the thimble mechanism.

Preferably, the method for measuring the pressure of each cavity in the step S4 tends to be stable is as follows:

A. Collect the internal pressure value of each cavity;

B. Calculate the average value of each pressure value;

C. Make a difference between the internal pressure value of each cavity and the average value to obtain the difference; if all the differences are less than the specified threshold, then it is determined that the pressure of each cavity tends to be stable; if there is a certain difference greater than the specified threshold, then Perform step A again.

Preferably, the specified threshold in step C is 2.0.

Preferably, step S6 is also included, and the step S6 is to use a blowing device to blow air on the demoulded mold to cool down the residual heat of the demolded mold.

Preferably, the temperature of the mold is lowered to 50-65° in the step S3.

The advantages of the present invention are:

1. In this solution, by detecting the pressure inside the cavity, it is convenient for the operator to know the internal pressure information of the mold cavity. When the internal pressure of the cavity is stable, the demoulding can be performed in time, reducing the waiting time for demoulding and improving the molding efficiency of the product.

2. This solution is equipped with an air injection device, which can spray air on the products after demoulding, quickly reduce the product preheating and clean the mold, and facilitate the rapid injection molding of the next batch of products.

2. In this scheme, a specific method can be used to calculate the moment when the pressure inside the cavity is stable and reduce the demoulding time.

Description of drawings

Fig. 1 is a mold structural diagram of the present invention;

Fig. 2 is a demoulding state diagram of the present invention;

Fig. 3 is the structure diagram of the second formwork of the present invention;

Fig. 4 is a flow chart of the method of the present invention.

In the figure: 1 fixed plate, 2 moving plate, 3 first template, 4 supporting plate, 5 receiving plate, 6 second template, 7 first core, 8 second core, 9 installation hole, 10 pressure sensor, 11 First cavity, 12 First core plate, 13 Second cavity, 14 Second core plate, 15 Ejection cylinder, 16 Top plate, 17 Ejector pin, 18 Air source, 19 Air nozzle, 20 Guide hole, 21 Air injection hole, 22 circulation passages, 23 sealing rings.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention.

In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "both ends", "one end", "another end" ” and other indicated orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, with a specific configuration and operation, and therefore should not be construed as limiting the invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and should not be understood as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise specified and limited, the terms "installed", "set with", "connected", etc. should be understood in a broad sense, such as "connected", which may be a fixed connection , can also be detachably connected, or integrally connected; can be mechanically connected, can also be electrically connected; can be directly connected, can also be indirectly connected through an intermediary, and can be internal communication between two components. Meanwhile, when an element is referred to as being “fixed on” or “disposed on” another element, it can be directly on the other element or there may be intervening elements at the same time. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or intervening elements may also be present. When an element is said to be "fixedly connected" to another element, it may be by the usual fixed methods such as welding or bolting or gluing. In a word, those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention in specific situations.

Example 1

A plastic mold, as shown in Figure 1-3, includes a fixed plate 1 and a moving plate 2, the bottom of the fixed plate 1 is provided with a first template 3, the first template 3 is provided with a first cavity 11, the first cavity A first core plate 12 is provided in the cavity 11, and several first cores 7 are arranged on the first core plate 12, and a positioning plate is connected to the top of the fixed plate 1 by bolts, and a feed port, that is, a gate, is provided on the positioning plate. , The feeding port runs through the positioning plate, the fixed plate 1 and the moving plate 2.

The top of the mobile plate 2 is provided with a support plate 4, the top of the support plate 4 is provided with a receiving plate 5, the top of the receiving plate 5 is provided with a second template 6, the second template 6 is provided with a second cavity 13, and the second cavity A second core plate 14 is provided in the cavity 13, and a plurality of second cores 8 corresponding to the first core 7 are arranged on the second core plate, and there is formed between the first core 7 and the second core 8 The mold cavity, the plastic raw material enters the mold cavity from the feed port and is cooled and formed. The movable plate 2 is provided with an ejection mechanism, and the ejection mechanism includes an ejection cylinder 15, a top plate 16 and a thimble 17, and the output end of the ejection cylinder 15 is connected with the top plate 16, and several thimbles 17 are connected above the top plate 16. Through the receiving plate 5 and the first template 3 and the second template 6, when demoulding, the top plate 16 is driven upward by the ejector cylinder 15, and the top plate 16 drives the thimble 17 to lift up, so that the first template 3 and the second template The template 6 is phase-separated to complete the demoulding work.

The top of the second core 8 is provided with a mounting hole 9, the mounting hole 9 is provided with a pressure sensor 10, the pressure sensor 10 is flush with the top of the second core 8, and the pressure sensor 10 is used to sense the internal pressure in the cavity, The time when the pressure tends to be stable can be detected through the internal pressure data, which can demould the mold faster and improve the efficiency of product injection molding.

The side of the second template 6 is provided with an air injection device, in conjunction with Fig. 3, the air injection device includes an air injection nozzle 19, and the air injection nozzle 19 is a protruding columnar structure, and the first template 3 is provided with a corresponding air injection nozzle 19. The guide hole 20, the air nozzle 19 and the guide hole 20 can play a guiding role on the one hand. On the other hand, two air injection holes 21 are provided on the air injection nozzle 19 , and the two air injection holes 21 respectively face different second cores 8 . In this embodiment, there are at least two air nozzles 19 located on both sides of the second template 6 . The air injection device also includes an external air source 18, and the receiving plate 5 is provided with a circulation passage 22, one end of the circulation passage 22 is connected with the air nozzle 19, and the other end of the circulation passage 22 is connected with the air source 18, and the air source 18 passes through the circulation passage 22. The high-speed airflow is sprayed to the second mold core 8 after demolding through the air injection holes 21 . The end of the circulation channel 22 close to the spray nozzle is provided with a sealing ring 23, which can improve the sealing effect.

In this embodiment, before demoulding, the mold is first cooled, and a circulating water channel is provided on the first core plate 12 and the second core plate 14, and the cooling water is injected into the cooling water, and the internal pressure of the cavity is controlled at the same time. Detection, when the injection molding is stopped and the gate is cooled and closed, the internal pressure of the cavity will gradually decrease until the internal air pressure is the same as the external air pressure. In order to increase the demoulding efficiency, the pressure sensor 10 is used to detect the internal pressure of the mold cavity, and when the pressure tends to be stable, the demoulding can be performed. After demoulding, referring to Figure 2, the air injection device can spray air on the demoulded product, which can quickly reduce the product preheating and clean the mold, so that the next batch of products can be injection molded quickly.

Example 2

An injection molding method for a plastic mould, comprising the following steps;

S1, injection mold filling, plastic raw materials are injected into the cavity of the mould, until the inside of the mold cavity is injected to 95%, and the injection molding is stopped;

S2. Maintaining pressure, continuously applying pressure to the mold until the gate is cooled and closed;

S3, cooling and shaping, open the cooling water pipe, pour water into the circulating cooling water pipe on the first template 3 and the second template 6 for cooling, until the mold temperature drops to a specified temperature of 50°;

S4, calculate cavity pressure, wait for each cavity pressure to become stable; Eight cavity are provided in the present embodiment, the measuring method that each cavity pressure tends to be stable is;

A. Collect the internal pressure value of each cavity;

B. Calculate the average value of each pressure value;

C. Make a difference between the internal pressure value of each cavity and the average value to obtain the difference; if all the differences are less than the specified threshold, then it is determined that the pressure of each cavity tends to be stable; if there is a certain difference greater than the specified threshold, then Perform step A again.

This embodiment monitors the cavity pressure in different time periods after the pressure holding is completed, and the data table is shown in Table 1. The unit is Mpa

In this embodiment, T1 is recorded after the pressure holding stage is completed, the flow front of the plastic melt reaches the pressure sensor 10, and the pressure curve starts to be obtained. The filling phase pressure increases linearly with time. The filling phase ends and the mold is filled. After the mold is filled, the melt is compressed to ensure that the profile of the injection molded part is formed. The compression phase is followed by a pressure holding phase. In view of the fact that the plastic heat shrinks significantly after cooling, the volume will decrease, and it will shrink greatly when cooling, so it is necessary to maintain the pressure. During the packing phase, to compensate for thermal shrinkage, a maximum of 10% of the injection molding volume is pressed into the cavity. After cooling, the holding pressure is transmitted, and as the melt hardens, the runner narrows, and it becomes more difficult for the melt to flow from the screw front chamber into the mold cavity. Continued heat shrinkage with decreasing melt flow causes the pressure in the mold cavity to drop, eventually reaching normal atmospheric pressure levels.

As shown in Table 1, in the T1 stage, the average value of each pressure is about 38.8Mpa. By making a difference between the average value and the pressure value of each cavity, it is found that the difference between the pressure value of the first cavity and the average value is 5.8 , which is greater than the specified threshold 2.0. In the T2 stage, the average value of each pressure is about 29.8Mpa. By making a difference between the average value and the pressure value of each cavity, it is found that the difference between the pressure value of the first cavity and the average value is 2.2, In the T3 stage, the average value of each pressure is about 15.3Mpa. Through the difference between the average value and the pressure value of each cavity, it is found that the difference between the pressure value of each cavity and the average value is less than the specified threshold, so it is judged as each type The pressure inside the cavity tends to be stable, and demoulding can be carried out. In the T4 stage, the pressure in the mold cavity drops to a level close to the normal atmospheric pressure, which is a commonly used demoulding stage. However, after calculation in this embodiment, it can be judged that the internal pressure tends to be stable at the T3 stage, and the demoulding pressure condition is met, and the process is carried out.

The final step S5, the plastic is demolded, and the mold is separated by the thimble 17 mechanism. Compared with traditional demoulding,

Saves demoulding time. After the demoulding is completed, use the air jet device to blow air on the mold after demoulding to cool down the residual heat of the mold after demoulding, and at the same time, it can play a certain role in cleaning the mold.

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications and substitutions can be made to these embodiments without departing from the principle and spirit of the present invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (10)

1. A plastic mold, characterized in that: including fixed plate (1) and movable plate (2), the bottom of fixed plate (1) is equipped with first template (3), the top of movable plate (2) is equipped with backup pad (4), the top of backup pad (4) is equipped with and accepts board (5), the top of accepting board (5) is equipped with second template (6), be equipped with first core (7) in first template (3), correspond on second template (6) to be equipped with second core (8), be formed with the die cavity between first core (7) and second core (8), the top of second core (8) is equipped with mounting hole (9), be equipped with pressure sensor (10) in mounting hole (9), pressure sensor (10) flush with second core (8) top, the side of second template (6) is equipped with jet equipment.

2. A plastic mould according to claim 1, characterized in that: the novel mold is characterized in that a first cavity (11) is formed in the first mold plate (3), a first core plate (12) is arranged in the first cavity (11), a plurality of first cores (7) are arranged on the first core plate (12), a second cavity (13) is formed in the second mold plate (6), a second core plate (14) is arranged in the second cavity (13), and a plurality of second cores (8) corresponding to the first cores (7) are arranged on the second core plate.

3. A plastic mould according to claim 2, characterized in that: the movable plate (2) is provided with an ejection mechanism, the ejection mechanism comprises an ejection cylinder (15), a top plate (16) and an ejector pin (17), the output end of the ejection cylinder (15) is connected with the top plate (16), the ejector pin (17) is connected above the top plate (16), and the ejector pin (17) passes through the bearing plate (5) and the first template (3) to be abutted against the second template (6).

4. A plastic mould according to claim 3, characterized in that: the air injection device comprises an air source (18) and an air nozzle (19), wherein the air nozzle (19) protrudes out of the surface of the second template (6), a guide hole (20) is formed in the first template (3) in cooperation with the air nozzle (19), an air injection hole (21) is formed in the air nozzle (19), the air injection hole (21) faces towards the second mold core (8), and the air source (18) is connected with the air nozzle (19).

5. The plastic mold of claim 4, wherein: the paint spraying device is characterized in that a circulating channel (22) is arranged in the bearing plate (5), one end of the circulating channel (22) is connected with the air nozzle (19), the other end of the circulating channel (22) is connected with the air source (18), and a sealing ring (23) is arranged at one end, close to the paint spraying nozzle, of the circulating channel (22).

6. An injection molding method of a plastic mold is characterized in that: comprises the following steps of;

s1, injecting and filling a mold, namely injecting a plastic raw material into a cavity of the mold until the interior of the mold cavity is injected to 90% -95%, and stopping injection;

s2, maintaining pressure, and continuously applying pressure to the die until the pouring gate is cooled and closed;

s3, cooling and shaping, namely opening a cooling water pipe, and injecting water into the circulating cooling water pipes on the first template (3) and the second template (6) for cooling until the temperature of the die is reduced to a specified temperature;

s4, calculating the cavity pressure, and waiting for the stability of the cavity pressure;

s5, demolding the plastic, and separating the mold through a thimble (17) mechanism.

7. The injection molding method of a plastic mold according to claim 6, wherein: the measuring method for the pressure of each cavity in the step S4 is that the pressure tends to be stable;

A. collecting the internal pressure value of each cavity;

B. calculating the average value of each pressure value;

C. the internal pressure value of each cavity is differed from the average value to obtain a difference value; if all the differences are smaller than the specified threshold, the pressure of each cavity is considered to be stable, and if a certain difference is larger than the specified threshold, the step A is executed again.

8. The injection molding method of a plastic mold according to claim 7, wherein: the specified threshold in step C is 2.0.

9. The injection molding method of a plastic mold according to claim 8, wherein: the method further comprises a step S6, wherein the step S6 is to blow the demoulded die by using a blowing device and cool the demoulded die waste heat.

10. The injection molding method of a plastic mold according to claim 8, wherein: and in the step S3, the temperature of the die is reduced to 50-65 degrees.