JP2022068921A - Injection compression molding method, injection device and injection molding machine - Google Patents

Abstract

To provide an injection compression molding method that ensures consistent quality of a molded product.SOLUTION: In an injection molding machine (1), a position sensor (36) that directly detects a mold opening amount of a mold (24, 25) is provided on a molding machine (7, 8) or the mold (24, 25). When implementing an injection-compression molding method consisting of a mold opening and injection process in which the mold (24, 25) are opened and injection material is injected and a compression process to narrow the mold opening amount of the mold (24, 25) by driving a mold clamping device (2) afterwards, the mold clamping device (2) is controlled so that the mold opening amount detected by the position sensor (36) is constant during the mold opening and injection process. This eliminates a problem of unstable injection due to a slight widening of the mold opening amount caused by injection pressure during the mold opening and injection process, thereby stabilizing a quality of the molded product.SELECTED DRAWING: Figure 1

Description

The present invention relates to an injection compression molding method for obtaining a molded product by an injection step of injecting with the mold open, a compression step of narrowing the mold opening amount, a mold clamping device in which the injection compression molding method is carried out, and injection. It is about a molding machine.

As an injection method for injecting an injection material into a mold to obtain a molded product, there is an injection compression molding method as described in, for example, Patent Document 1. In the injection compression molding method, an injection step of injecting an injection material with the mold opened is carried out, and then a compression step of driving a mold clamping device to narrow the mold opening amount is carried out. In the compression process, the injection material may be continuously injected, or the injection may be stopped. In any case, by carrying out the compression step in a state where the injection material is injected into the cavity, the injection material is efficiently filled in the cavity.

Japanese Unexamined Patent Publication No. 2012-144042

The injection process of the injection compression molding method is carried out with the mold open, but in order to keep the mold open, the mold clamping device needs to have a constant mold opening amount. For example, in the case of a toggle type mold clamping device, the position of the crosshead of the toggle mechanism is controlled to be constant. That is, control is performed to keep the motor position constant for the mold clamping servomotor that drives the crosshead. By such control, the mold opening amount in the injection process should be kept constant, the injection should be stable, and the quality of the molded product should be constant. However, there is a problem that the mold opening amount may change during the molding cycle or for each molding shot, and the molding is not stable.

Other issues and novel features will become apparent from the description and accompanying drawings herein.

In the present disclosure, a position sensor that directly detects the mold opening amount of a mold in an injection molding machine is provided on the mold plate or the mold. When carrying out an injection compression molding method consisting of a mold opening injection step of injecting an injection material with the mold open, and then a compression step of driving a mold clamping device to narrow the mold opening amount of the mold. In the mold opening injection process, the mold clamping device is controlled so that the mold opening amount detected by the position sensor is constant.

According to the present disclosure, since the mold clamping device is controlled so that the mold opening amount is constant in the mold opening injection process, the mold opening amount does not change in each molding cycle, the injection is stable and the quality is constant. A molded product is obtained.

It is a front view which shows the injection molding machine which concerns on this embodiment. It is a flowchart which shows the process of the injection compression molding method which concerns on this embodiment. It is a front sectional view showing a part of an injection molding machine and a mold at the start of the injection compression molding method which concerns on this embodiment. It is a front sectional view which shows a part of an injection molding machine and a mold in the mold closing process of the injection compression molding method which concerns on this embodiment. It is a front sectional view which shows a part of an injection molding machine and a mold in the 1st stage mold opening injection process of the injection compression molding method which concerns on this embodiment. FIG. 3 is a front sectional view showing a part of an injection molding machine and a mold in the first-stage compression step of the injection compression molding method according to the present embodiment. It is a front sectional view which shows a part of an injection molding machine and a mold in the 2nd stage mold opening injection process of the injection compression molding method which concerns on this embodiment. FIG. 3 is a front sectional view showing a part of an injection molding machine and a mold in the second stage compression step of the injection compression molding method according to the present embodiment. It is a graph which shows the change of the screw position, the injection pressure, the mold opening amount, the mold clamping servomotor position, and the mold clamping force when the injection compression molding method which concerns on this embodiment is carried out. 3 is a graph showing changes in screw position, injection pressure, mold opening amount, mold clamping servomotor position, and mold clamping force when a conventional injection compression molding method is carried out. 3 is a graph showing changes in screw position, injection pressure, mold opening amount, mold clamping servomotor position, and mold clamping force when the injection compression molding method according to another embodiment of the present embodiment is carried out. 3 is a graph showing changes in screw position, injection pressure, mold opening amount, mold clamping servomotor position, and mold clamping force when a conventional injection compression molding method is carried out. It is a front view which shows a part of the injection molding machine which concerns on 2nd Embodiment of this invention, and a mold. It is a front view which shows a part of the injection molding machine which concerns on 3rd Embodiment of this invention, and a mold.

Hereinafter, specific embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. The following description and drawings have been simplified as appropriate to clarify the description. In each drawing, the same elements are designated by the same reference numerals, and duplicate explanations are omitted as necessary. In addition, there is a part where hatching is omitted so that the drawing is not complicated.

<Injection molding machine>
As shown in FIG. 1, the injection molding machine 1 according to the present embodiment is roughly composed of a mold clamping device 2 and an injection device 3 provided on the bed B. The mold clamping device 2 includes a fixed plate 7, a movable plate 8, a mold clamping housing 9, tie bars 10, 10, ... That connect the mold clamping housing 9 and the fixing plate 7, and a toggle mechanism 11. Has been done. The mold clamping device 2 is provided with a mold clamping servomotor 13 so as to rotate the ball screw mechanism 16 via the transmission mechanism 15 to drive the crosshead 17 of the toggle mechanism 11.

The injection device 3 is roughly composed of a heating cylinder 19 and a screw 20 housed in the heating cylinder 19. The injection molding machine 1 according to the present embodiment is provided with a controller 22 to control the mold clamping servomotor 13 and the injection device 3 of the mold clamping device 2.

<Mold>
In this embodiment, the mold provided in the mold clamping device 2 is characteristic. The molds are the fixed side mold 24 provided on the fixed plate 7 and the movable side mold 25 provided on the movable plate 8.
It is composed of and, but it is a mold for injection compression molding.

The parting line of the fixed-side mold 24 is flat, but the peripheral portion of the movable-side mold 25 is recessed from the parting line to form a stepped portion 27, whereby the central portion thereof is formed. A convex portion 28 is formed on the surface. A frame body 31 is provided on the step portion 27 via a plurality of springs 30 and 30. The frame 31 is pushed forward by the springs 30 and 30, but retracts when pushed by the fixed mold 24. The cavity is composed of the parting line of the fixed side mold 24, the convex portion 28 of the movable side mold 25, and the frame body 31, but when the mold is closed and the frame body 31 retracts, the cavity is formed. The volume becomes smaller. This makes it possible to compress the injection material injected into the cavity.

The fixed-side mold 24 is provided with a sprue 33 and a runner 34, and an injection nozzle 35 provided in the heating cylinder 19 is in contact with the sprue 33.

<Position sensor>
The injection molding machine 1 according to the present embodiment is characterized in that a position sensor 36 that directly detects the mold opening amount of the molds 24 and 25 is provided. The position sensor 36 may be provided on the mold plate, that is, the fixed platen 7, or the movable platen 8, but in the present embodiment, the position sensor 36 is provided on the molds 24 and 25. In this embodiment, the position sensor 36 comprises a contact sensor provided with a pin 38. The position sensor 36 is fixed to the movable mold 25, and the detection piece 39 to which the pin 38 hits is provided on the frame 31. Therefore, when the molds 24 and 25 are closed and the frame 31 is retracted, the amount of mold opening is reduced and the position sensor 36 detects it. The position sensor 36 is also connected to the controller 22, and the mold opening amount is input to the controller 22.

<Injection compression molding method according to this embodiment>
The injection compression molding method according to this embodiment will be described.
At the start of the molding cycle, the molds 24 and 25 are in a completely open state, as shown in FIG. 3A. As shown in FIG. 2, the controller 22 first performs the mold closing step S1. That is, the mold clamping servomotor 13 is driven to drive the movable platen 8 in the mold closing direction so that the fixed side mold 24 and the frame body 31 of the movable side mold 25 are in contact with each other. That is, the mold is closed until the mold is opened by a predetermined amount of mold opening. That is, the position where the cavity is formed is set. This state is shown in FIG. 3B.

<First stage mold opening injection process>
The first-stage mold opening injection step S2 is performed in a state where this cavity is configured and the mold is opened. That is, the controller 22 drives the screw 20 of the injection device 3 to move forward at a constant speed. As a result, as shown in FIG. 3C, the cavities of the molds 24 and 25 are filled with the injection material.

When the injection material is injected into the cavity, the injection pressure acts on the molds 24 and 25. Due to this injection pressure, the tie bars 10 and 10 are slightly extended and the mold opening amount is slightly increased. However, in the injection compression molding method according to the present embodiment, the mold opening amount is controlled to be constant in the first-stage mold opening injection step S2. Specifically, the controller 22 controls the motor position of the mold clamping servomotor 13 so that the mold opening amount detected by the position sensor 36 becomes constant. As a result, the change in the mold opening amount in the first-stage mold opening injection step S2 is suppressed.

Referring to the graph of FIG. 4, in the first-stage mold opening injection step S2, the mold opening amount is controlled to be constant as indicated by reference numeral 51. At this time, the motor position of the mold clamping servomotor 13 is gradually changed during the first stage mold opening injection step S2 as shown by reference numeral 52 in order to keep the mold opening amount constant. This is because the elongation of the tie bars 10 and 10 is offset and the mold opening amount is controlled to be constant. Further, since the tie bars 10 and 10 are slightly extended, the mold clamping force is gradually increased in the first-stage mold opening injection step S2 as indicated by reference numeral 53.

The first-stage mold opening injection step S2 is completed when the injection material filled in the cavity reaches a reference filling factor, for example, 50%. Whether or not the reference filling factor has been reached may be detected at the position of the screw 20, that is, at the screw position, or may be detected by the elapsed time from the start of the first-stage mold opening injection step S2. ..

<First stage compression process>
After the completion of the first-stage mold opening injection step S2, the controller 22 carries out the first-stage compression step S3. That is, as shown in FIG. 3D, the mold clamping servomotor 13 is driven to compress the molds 24 and 25 in the mold closing direction. The mold opening amount is narrowed as shown by reference numeral 55 in the graph of FIG. When the mold opening amount reaches the reference amount, the first-stage compression step S3 is completed. The injection of the injection material may be stopped or continued in the first-stage compression step S3. In the present embodiment, the screw 20 is advanced to continue the injection of the injection material even during this process. Therefore, the screw position continues to move forward as indicated by reference numeral 56 in the graph of FIG. The mold clamping force is increased by the first-stage compression step S3 as indicated by reference numeral 57.

<Second stage mold opening injection process>
The second-stage mold opening injection step S4 is carried out. That is, the controller 22 drives the screw 20 of the injection device 3 to move forward at a constant speed. As a result, as shown in FIG. 3E, the cavities of the molds 24 and 25 are additionally filled with the injection material.

Also in the second-stage mold opening injection step S4, the mold opening amount is controlled to be constant. That is, the controller 22 controls the motor position of the mold clamping servomotor 13 so that the mold opening amount detected by the position sensor 36 becomes constant. As a result, the change in the mold opening amount in the second-stage mold opening injection step S4 is suppressed.

Also in the second-stage mold opening injection step S4, the mold opening amount is controlled to be constant as shown by reference numeral 59 in the graph of FIG. 4, so that the motor position of the mold clamping servomotor 13 is indicated by reference numeral 60. It is changing little by little as it is. Also, during this step, the tie bars 10 and 10 are slightly stretched so that the mold clamping force is slightly increased as indicated by reference numeral 61.

The second-stage mold opening injection step S4 is completed when the injection material filled in the cavity reaches a reference filling factor, for example, 80%.

<Second stage compression process>
After the completion of the second-stage mold opening injection step S4, the controller 22 carries out the second-stage compression step S5. That is, the mold clamping servomotor 13 is driven to mold mold 24 and 25. As shown in FIG. 3F, the injection material fills the entire cavity. In the second stage compression step S5, the injection of the injection material may be stopped or the injection may be continued. In the present embodiment, the screw 20 is advanced to continue the injection of the injection material even during this process. Therefore, the screw position continues to move forward as indicated by reference numeral 63 in the graph of FIG. When the screw position reaches the completion position, the injection is stopped. When the injection material is cooled and solidified, the second stage compression step S5 is completed.

<Mold opening process, protrusion process>
As shown in FIG. 2, the mold opening step S6 is carried out. That is, the mold clamping servomotor 13 is driven to open the molds 24 and 25. Then, the projecting step S7 is carried out to project the molded product. Complete the molding cycle. The process returns to the mold closing step S1 and the molding cycle is repeated.

<Conventional injection compression molding method>
The conventional injection compression molding method also includes an injection step of injecting in the mold open state and a compression step of driving the mold clamping device to narrow the mold opening amount. However, in the injection process, when the injection is performed in the mold open state, the motor position of the mold clamping servomotor 13 is conventionally controlled so as not to change. In other words, as shown by reference numeral 70 in the graph of FIG. 5, the position of the crosshead 17 is controlled so as not to change. Then, the mold opening amount gradually opens as indicated by reference numeral 71. This is because even if the position of the crosshead 17 is constant, the tie bars 10 and 10 are slightly extended by the injection pressure. As a result, the mold clamping force is also slightly increased as indicated by reference numeral 72.

After completing the first-stage injection process, the first-stage compression process is performed. Then, when the second-stage injection process is carried out, the motor position of the mold clamping servomotor 13 is prevented from changing by the conventional control method as in the first-stage injection process. Therefore, the mold opening amount gradually opens as indicated by reference numeral 75. As a result, the mold clamping force is also slightly increased as indicated by reference numeral 76.

As described above, in the conventional injection compression molding method, the mold opening amount gradually increases in the injection process, so that the injection cannot be stabilized. Therefore, the mold opening amount in the injection process differs for each molding cycle, which causes variations in the quality of the molded product.

On the other hand, in the injection compression molding method according to the present embodiment, since the mold opening amount is controlled to be constant in the mold opening injection steps S2 and S4, the injection is stable. Therefore, the effect that the quality of the obtained molded product can be maintained constant can be obtained.

<Injection compression molding method according to another embodiment of this embodiment>
In the injection compression molding method according to the above embodiment, the compression steps S3 and S5 have been described so as to drive the mold clamping servomotor 13 to mold the molds 24 and 25. That is, it was explained that the molds 24 and 25 are only driven in the direction of narrowing the mold opening amount. However, the compression steps S3 and S5 may be composed of a mold opening step for temporarily expanding the mold opening amount and a compression step for narrowing the mold opening amount performed after the mold opening step. FIG. 6 shows the screw position, injection pressure, mold opening amount, and mold clamping servo when the injection compression molding method including the mold opening stage 81 and the compression stage 82 is carried out in the second stage compression step S5'. Changes in motor position and mold clamping force are shown.

As shown in the graph of FIG. 6, in the second stage compression step S5', it is necessary to carry out the mold opening step 81 to expand the mold opening amount as indicated by reference numeral 84. Therefore, the motor position of the mold clamping servomotor 13 is temporarily driven in the mold opening direction as indicated by reference numeral 85. Then, the mold clamping force is inevitably reduced as shown by reference numeral 86.

In the second stage compression step S5', the mold clamping step 82 is carried out after the mold opening step 81. That is, as indicated by reference numeral 87, the mold clamping servomotor 13 is driven. Then, the mold opening amount is narrowed as shown by reference numeral 88, and the mold clamping force is increased as shown by reference numeral 89. This compresses the injection material filled in the cavity.

In this embodiment, the first stage compression step S3 is not composed of the mold opening stage and the compression stage, but the first stage compression step S3 is also composed of the mold opening stage and the compression stage. You may do it. Further, in the first-stage compression step S3 and the second-stage compression step S5', the screw 20 is advanced to continue the injection of the injection material, but the screw 20 is stopped to stop the injection. May be good.

<Conventional injection compression molding method>
FIG. 7 shows the screw position, injection pressure, mold opening amount, mold clamping servomotor position, when the conventional injection compression method in which the second stage compression process is composed of a mold opening stage and a compression stage is carried out. And the change of the mold clamping force is shown.

In the second stage compression step of this conventional injection compression method, a mold opening step is performed to drive the mold clamping servomotor 13 as indicated by reference numeral 92, and the mold opening amount is indicated by reference numeral 91. It is spreading as if it were. After that, a mold clamping step is carried out to drive the mold clamping servomotor 13 as shown by reference numeral 93, and the mold opening amount is narrowed as shown by reference numeral 94. Therefore, as indicated by reference numerals 95 and 96, the mold clamping force is temporarily reduced and then increased.

Therefore, it seems that the injection compression molding method has been properly implemented. However, as shown by reference numerals 101 and 102, since the motor position of the mold clamping servomotor 13 is controlled to be constant in the injection process of the first stage and the second stage, the mold opening amount is indicated by reference numeral 103 depending on the injection pressure. , 104 will open slightly and the mold clamping force will also change as indicated by reference numerals 105 and 106. Therefore, the mold opening amount in the injection process differs for each molding cycle, which causes variations in the quality of the molded product.

<Other Embodiments of the present invention>
The injection molding machine 1 and the molds 24 and 25 according to the present embodiment can be deformed in various ways. FIG. 6 shows a second embodiment. In this embodiment, the movable side mold 25'is such that the frame body 31 is pushed up by the hydraulic cylinders 41 and 41. Also in this embodiment, if the molds 24 and 25'are closed to reduce the mold opening amount, the frame 31 is pushed against the pushing force of the hydraulic cylinders 41 and 41.

In this embodiment, the position sensor 36'is also different from the previous embodiment. The position sensor 36'consists of a non-contact sensor that measures the position by a laser. The position sensor 36'is designed to detect the mold opening amount by measuring the distance from the marker 42.

FIG. 7 shows a third embodiment. In this embodiment, the fixed side mold 24 ″ and the movable side mold 25 ″ are so-called inlay molds. That is, the fixed-side mold 24 ″ has a shape in which the peripheral portion protrudes relatively high, and the movable-side mold 25 ″ has a shape in which the peripheral portion is retracted. The molds 24 ″ and 25 ″ are combined like an inlay so that the mold opening injection process and the compression process can be performed.

In the injection compression step according to the present embodiment, the mold opening injection step and the compression step are carried out twice each. In other words, it is carried out for two stages. However, it may be carried out in only one step, or may be carried out in three or more steps. The mold clamping servomotor 13 may be controlled so that the mold opening amount detected by the position sensor 36 becomes constant in the mold opening injection process regardless of the number of stages.

Although the invention made by the present inventor has been specifically described above based on the embodiments, the present invention is not limited to the embodiments already described, and various changes can be made without departing from the gist thereof. It goes without saying that it is possible. The plurality of examples described above can be carried out in combination as appropriate.

1 Injection molding machine 2 Mold clamping device 3 Injection device 7 Fixed plate 8 Movable plate 9 Mold clamping housing 10 Tie bar 11 Toggle mechanism 13 Mold clamping servo motor 17 Cross head 19 Heating cylinder 20 Screw 22 Controller 24 Fixed side mold 25 Movable side metal Mold 30 Spring 31 Frame 36 Position sensor 38 Pin 39 Detection piece 41 Hydraulic cylinder

Claims (27)

The mold opening injection process in which the injection material is injected with the mold opened by the mold clamping device,
A compression step of driving the mold clamping device to narrow the mold opening amount of the mold after the mold opening injection step is provided.
In the mold opening injection step, the mold opening amount of the mold is detected by a position sensor, and the mold clamping device is controlled so that the mold opening amount becomes constant based on the detection result of the position sensor. Method. The injection compression molding method according to claim 1, wherein the injection of the injection material is continued in the compression step. The compression step includes a mold opening step of driving the mold clamping device to expand the mold opening amount of the mold, and compression for driving the mold opening device after the mold opening process to narrow the mold opening amount of the mold. The injection molding method according to claim 1 or 2, which comprises steps. The injection compression molding method according to any one of claims 1 to 3, wherein the mold clamping mechanism of the mold clamping device is a toggle mechanism. The injection compression molding method according to any one of claims 1 to 4, wherein the mold clamping device is driven by a servomotor. The injection compression according to any one of claims 1 to 5, wherein one injection compression step and one compression step are one-stage injection compression steps, and the injection compression steps are repeated two or more steps. Molding method. The injection compression molding method according to any one of claims 1 to 6, wherein the position sensor comprises a contact sensor. The injection compression molding method according to any one of claims 1 to 7, wherein the position sensor comprises a non-contact type sensor. The injection compression molding method according to any one of claims 1 to 8, wherein the mold has a built-in spring that repels the closing of the mold. A mold with a mold and
A position sensor that detects the amount of mold opening and
With a control unit,
The control unit
When injection compression molding including a mold opening injection step in which an injection material is injected with the mold opened and a compression step for narrowing the mold opening amount of the mold after the mold opening injection step is performed. ,
A mold clamping device that controls the mold opening amount to be constant based on the detection result of the position sensor in the mold opening injection step. The mold clamping device according to claim 10, wherein the injection of the injection material is continued in the compression step. In the compression step, the mold opening step is driven to increase the mold opening amount of the mold, and the mold opening process is driven to narrow the mold opening amount of the mold. The mold clamping device according to claim 10 or 11, which comprises a compression step. The mold clamping device according to any one of claims 10 to 12, wherein the mold clamping mechanism of the mold clamping device is a toggle mechanism. The mold clamping device according to any one of claims 10 to 13, wherein the mold clamping device is driven by a servomotor. One of claims 10 to 14, wherein one injection compression step and one compression step are one-step injection compression steps, and the injection compression steps are repeated in two or more steps. The mold clamping device described in the section. The mold clamping device according to any one of claims 10 to 15, wherein the position sensor comprises a contact type sensor. The mold clamping device according to any one of claims 10 to 16, wherein the position sensor comprises a non-contact type sensor. The mold clamping device according to any one of claims 10 to 17, wherein the mold has a built-in spring that repels the closing of the mold. A mold clamping device equipped with a mold and
An injection device that injects injection material and
A position sensor that detects the amount of mold opening and
With a control unit,
The control unit
When injection compression molding including a mold opening injection step in which an injection material is injected with the mold opened and a compression step for narrowing the mold opening amount of the mold after the mold opening injection step is performed. ,
An injection molding machine that controls the mold opening amount to be constant based on the detection result of the position sensor in the mold opening injection step. The injection molding machine according to claim 19, wherein the injection of the injection material is continued in the compression step. In the compression step, the mold opening step is driven to expand the mold opening amount of the mold, and the mold opening process is driven to narrow the mold opening amount of the mold. The injection molding machine according to claim 19 or 20, which comprises a compression step. The injection molding machine according to any one of claims 19 to 21, wherein the mold clamping mechanism of the mold clamping device is a toggle mechanism. The injection molding machine according to any one of claims 19 to 22, wherein the mold clamping device is driven by a servomotor. One of claims 19 to 23, wherein one injection compression step and one compression step are one-step injection compression steps, and the injection compression steps are repeated in two or more steps. The injection molding machine described in the section. The injection molding machine according to any one of claims 19 to 24, wherein the position sensor comprises a contact sensor. The injection molding machine according to any one of claims 19 to 25, wherein the position sensor comprises a non-contact type sensor. The injection molding machine according to any one of claims 19 to 26, wherein the mold has a built-in spring that repels the closing of the mold.

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