JP7589008B2 - Injection compression molding method, injection device, and injection molding machine - Google Patents

Description

The present invention relates to an injection compression molding method that obtains a molded product through an injection process in which injection is performed with the mold open and a compression process in which the mold opening is narrowed, as well as a mold clamping device and an injection molding machine in which the injection compression molding method is performed.

One injection method for obtaining a molded product by injecting an injection material into a mold is the injection compression molding method described in Patent Document 1, for example. In the injection compression molding method, an injection process is carried out in which the injection material is injected with the mold open, and then a compression process is carried out in which the clamping device is driven to narrow the mold opening. Injection of the injection material may be continued during the compression process, or injection may be stopped. In either case, by carrying out the compression process with the injection material injected into the cavity, the cavity is efficiently filled with the injection material.

JP 2012-144042 A

The injection process in the injection compression molding method is carried out with the mold open, but in order to maintain the mold open, the mold clamping device must maintain 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. In other words, the mold clamping servo motor that drives the crosshead is controlled to maintain a constant motor position. This type of control keeps the mold opening amount constant during the injection process, which should result in stable injection and consistent quality of molded products. However, there are cases where the mold opening amount changes during the molding cycle or for each molding shot, resulting in unstable molding.

Other objects and novel features will become apparent from the description of this specification and the accompanying drawings.

In this disclosure, a position sensor that directly detects the mold opening amount of a mold is provided on a mold platen or mold in an injection molding machine. When performing an injection compression molding method consisting of a mold opening and injection process in which the mold is opened and injection material is injected, followed by a compression process in which a mold clamping device is driven to narrow the mold opening amount, the mold clamping device is controlled in the mold opening and injection process so that the mold opening amount detected by the position sensor is constant.

According to this disclosure, the mold clamping device is controlled so that the mold opening amount is constant during the mold opening injection process, so the mold opening amount does not change with each molding cycle, and injection is stable, resulting in molded products of consistent quality.

1 is a front view showing an injection molding machine according to an embodiment of the present invention; 2 is a flowchart showing steps of an injection compression molding method according to the present embodiment. FIG. 2 is a front cross-sectional view showing a part of the injection molding machine and a mold at the start of the injection compression molding method according to the present embodiment. FIG. 2 is a front cross-sectional view showing a part of an injection molding machine and a mold in a mold closing step of the injection compression molding method according to the present embodiment. 1 is a front cross-sectional view showing a part of an injection molding machine and a mold in a first mold opening and injection step of an injection compression molding method according to an embodiment of the present invention. FIG. FIG. 2 is a front cross-sectional view showing a part of an injection molding machine and a mold in a first-stage compression step of the injection compression molding method according to the present embodiment. FIG. 2 is a front cross-sectional view showing a part of an injection molding machine and a mold in a second mold opening and injection step of the injection compression molding method according to the present embodiment. FIG. 2 is a front cross-sectional view showing a part of an injection molding machine and a mold in a second-stage compression step of the injection compression molding method according to the present embodiment. 4 is a graph showing changes in the screw position, injection pressure, mold opening amount, mold clamping servo motor position, and mold clamping force when carrying out the injection compression molding method according to the present embodiment. 1 is a graph showing the changes in screw position, injection pressure, mold opening amount, mold clamping servo motor position, and mold clamping force when a conventional injection compression molding method is performed. 6 is a graph showing changes in the screw position, injection pressure, mold opening amount, mold clamping servo motor position, and mold clamping force when performing an injection compression molding method according to another embodiment of the present invention. 1 is a graph showing the changes in screw position, injection pressure, mold opening amount, mold clamping servo motor position, and mold clamping force when a conventional injection compression molding method is performed. FIG. 11 is a front view showing a part of an injection molding machine and a mold according to a second embodiment of the present invention. FIG. 11 is a front view showing a part of an injection molding machine and a mold according to a third embodiment of the present invention.

Specific embodiments will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments. To clarify the explanation, the following description and drawings have been simplified as appropriate. In each drawing, the same elements are given the same reference numerals, and duplicate explanations are omitted as necessary. In addition, hatching has been omitted in some areas to avoid cluttering the drawings.

<Injection molding machine>
1, an injection molding machine 1 according to this embodiment is generally composed of a clamping unit 2 and an injection unit 3 provided on a bed B. The clamping unit 2 is composed of a fixed platen 7, a movable platen 8, a clamping housing 9, tie bars 10, 10, ... connecting the clamping housing 9 and the fixed platen 7, and a toggle mechanism 11. A clamping servo motor 13 is provided in the clamping unit 2, which rotates a ball screw mechanism 16 via a transmission mechanism 15 to drive a crosshead 17 of the toggle mechanism 11.

The injection device 3 is generally composed of a heating cylinder 19 and a screw 20 inserted in the heating cylinder 19. The injection molding machine 1 according to this embodiment is provided with a controller 22, which controls the clamping servo motor 13 of the clamping device 2 and the injection device 3.

<Mold>
In this embodiment, a feature is the mold provided in the mold clamping device 2. The mold includes a fixed side mold 24 provided on the fixed platen 7 and a movable side mold 25 provided on the movable platen 8.
It is composed of a mold for injection compression molding.

The parting line of the fixed side mold 24 is flat, but the periphery of the movable side mold 25 is set back from the parting line to form a step 27, which forms a convex part 28 in the center. A frame 31 is attached to this step 27 via multiple springs 30, 30. The frame 31 is pushed forward by the springs 30, 30, but retreats when pushed by the fixed side mold 24. A cavity is formed by the parting line of the fixed side mold 24, the convex part 28 of the movable side mold 25, and the frame 31, and the volume of the cavity is reduced by closing the mold and retracting the frame 31. This makes it possible to compress the injection material injected into the cavity.

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

<Position sensor>
The injection molding machine 1 according to this embodiment is characterized in that it is provided with a position sensor 36 that directly detects the mold opening amount of the molds 24, 25. The position sensor 36 may be provided on the mold platen, i.e., the fixed platen 7 or the movable platen 8, but in this embodiment it is provided on the molds 24, 25. In this embodiment, the position sensor 36 is a contact sensor equipped with a pin 38. The position sensor 36 is fixed to the movable mold 25, and a detection piece 39 that the pin 38 abuts is provided on the frame 31. Therefore, when the molds 24, 25 are closed and the frame 31 moves backward, the mold opening amount decreases and is detected by the position sensor 36. This 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 the present embodiment>
The injection compression molding method according to this embodiment will be described.
At the start of the molding cycle, the molds 24, 25 are in a completely mold-open state as shown in Fig. 3A. As shown in Fig. 2, the controller 22 first executes the mold closing step S1. That is, the mold clamping servo motor 13 is driven to drive the movable platen 8 in the mold closing direction to bring the fixed mold 24 and the frame 31 of the movable mold 25 into contact with each other. That is, the molds are closed until they are opened by a predetermined mold opening amount. That is, they are brought to a position where a cavity is formed. This state is shown in Fig. 3B.

<First stage mold opening and injection process>
With this cavity formed and the mold open, the first stage mold opening and injection step S2 is carried out. That is, the controller 22 drives the screw 20 of the injection device 3 to advance at a constant speed. As a result, the cavities of the molds 24 and 25 are filled with the injection material, as shown in FIG. 3C.

When the injection material is injected into the cavity, the injection pressure acts on the molds 24, 25. This injection pressure causes the tie bars 10, 10 to stretch slightly, slightly increasing the mold opening amount. However, in the injection compression molding method according to this embodiment, the mold opening amount is controlled to be constant in the first mold opening injection process S2. Specifically, the controller 22 controls the motor position of the mold clamping servo motor 13 so that the mold opening amount detected by the position sensor 36 is constant. This suppresses changes in the mold opening amount in the first mold opening injection process S2.

Referring to the graph in Figure 4, in the first stage mold opening and injection process S2, the mold opening amount is controlled to be constant as indicated by reference symbol 51. At this time, the motor position of the mold clamping servo motor 13 changes little by little during the first stage mold opening and injection process S2 as indicated by reference symbol 52 in order to keep the mold opening amount constant. This is because the extension of the tie bars 10, 10 is offset to control the mold opening amount to be constant. In addition, since the tie bars 10, 10 extend slightly, the mold clamping force increases little by little in the first stage mold opening and injection process S2 as indicated by reference symbol 53.

The first stage mold opening injection process S2 is completed when the injection material filled into the cavity reaches a reference filling rate, for example 50%. Whether or not the reference filling rate has been reached can be detected by the position of the screw 20, i.e., the screw position, or by the elapsed time from the start of the first stage mold opening injection process S2.

<First stage compression process>
After the first stage mold opening injection step S2 is completed, the controller 22 executes the first stage compression step S3. That is, as shown in FIG. 3D, the mold clamping servo motor 13 is driven to compress the molds 24, 25 in the mold closing direction. The mold opening amount becomes narrower as shown by reference numeral 55 in the graph of FIG. 4. When the mold opening amount reaches a reference amount, the first stage compression step S3 is completed. In the first stage compression step S3, the injection of the injection material may be stopped or may be continued. In this embodiment, the screw 20 is advanced to continue the injection of the injection material even during this step. Therefore, the screw position continues to advance as shown by reference numeral 56 in the graph of FIG. 4. The first stage compression step S3 increases the mold clamping force as shown by reference numeral 57.

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

The mold opening amount is also controlled to be constant during the second stage mold opening and injection process S4. In other words, the controller 22 controls the motor position of the mold clamping servo motor 13 so that the mold opening amount detected by the position sensor 36 is constant. This suppresses changes in the mold opening amount during the second stage mold opening and injection process S4.

Even in the second mold opening injection process S4, the mold opening amount is controlled to be constant as shown by reference number 59 in the graph of FIG. 4, so the motor position of the mold clamping servo motor 13 changes little by little as shown by reference number 60. Also, during this process, the tie bars 10, 10 extend slightly, so the mold clamping force increases little by little as shown by reference number 61.

The second mold opening injection process S4 is completed when the injection material filling the cavity reaches a standard filling rate, for example 80%.

<Second stage compression process>
After the second stage mold opening injection process S4 is completed, the controller 22 executes the second stage compression process S5. That is, the mold clamping servo motor 13 is driven to clamp the molds 24 and 25. As shown in FIG. 3F, the injection material is filled into the entire cavity. In this second stage compression process S5, the injection of the injection material may be stopped or may be continued. In this embodiment, the screw 20 is advanced to continue the injection of the injection material even during this process. Therefore, the screw position continues to advance as shown by the reference numeral 63 in the graph of FIG. 4. When the screw position reaches the completion position, the injection is stopped. When the injection material is cooled and solidified, the second stage compression process S5 is completed.

<Mold opening process, ejection process>
As shown in Fig. 2, a mold opening step S6 is carried out. That is, the mold clamping servo motor 13 is driven to open the molds 24 and 25. Then, an ejection step S7 is carried out to eject the molded product. The molding cycle is completed. Then, the process returns to the mold closing step S1 and the molding cycle is repeated.

<Conventional injection compression molding method>
Conventional injection compression molding methods also include an injection process in which injection is performed with the mold open, and a compression process in which the mold clamping device is driven to narrow the mold opening. However, when injection is performed with the mold open in the injection process, conventionally the motor position of the mold clamping servo motor 13 is 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. As a result, the mold opening opens little by little, as shown by reference numeral 71. This is because even if the position of the crosshead 17 is constant, the tie bars 10, 10 are slightly extended by the injection pressure. This also causes the mold clamping force to increase slightly, as shown by reference numeral 72.

After the first injection process is completed, the first compression process is carried out. Then, when the second injection process is carried out, the conventional control method prevents the motor position of the mold clamping servo motor 13 from changing, just like the first injection process. Therefore, the mold opening amount opens little by little, as shown by reference number 75. This also causes the mold clamping force to increase slightly, as shown by reference number 76.

As described above, with conventional injection compression molding methods, the mold opening gradually widens during the injection process, making it impossible to stabilize the injection. As a result, the mold opening during the injection process varies for each molding cycle, causing variations in the quality of the molded product.

In contrast, in the injection compression molding method according to the present embodiment, the mold opening amount is controlled to be constant in the mold opening and injection steps S2 and S4, so the injection is stable. This has the effect of maintaining a constant quality for the molded product obtained.

<Injection compression molding method according to another embodiment of the present invention>
In the above embodiment of the injection compression molding method, the compression steps S3 and S5 are described as driving the clamping servo motor 13 to clamp the molds 24 and 25. In other words, the compression steps S3 and S5 are described as simply driving the molds 24 and 25 in a direction narrowing the mold opening amount. However, the compression steps S3 and S5 may be composed of a mold opening stage in which the mold opening amount is temporarily widened, and a compression stage performed after the mold opening stage in which the mold opening amount is narrowed. Figure 6 shows the changes in the screw position, injection pressure, mold opening amount, mold clamping servo motor position, and mold clamping force when an injection compression molding method is performed in which the second compression step S5' is composed of a mold opening stage 81 and a compression stage 82.

As shown in the graph of FIG. 6, in the second compression step S5', it is necessary to perform the mold opening stage 81 to widen the mold opening amount as indicated by reference numeral 84. Therefore, the motor position of the mold clamping servo motor 13 is temporarily driven in the mold opening direction as indicated by reference numeral 85. This inevitably reduces the mold clamping force as indicated by reference numeral 86.

In the second compression step S5', the mold opening stage 81 is followed by the mold clamping stage 82. That is, the mold clamping servo motor 13 is driven as shown by the reference numeral 87. This narrows the mold opening amount as shown by the reference numeral 88, and the mold clamping force increases as shown by the reference numeral 89. This compresses the injection material filled in the cavity.

In this embodiment, the first compression step S3 does not include a mold opening stage and a compression stage, but the first compression step S3 may also include a mold opening stage and a compression stage. Furthermore, in the first compression step S3 and the second compression step S5', the screw 20 is advanced to continue injecting the injection material, but the screw 20 may be stopped to stop the injection.

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

In the second compression step of this conventional injection compression method, a mold opening step is performed and the mold clamping servo motor 13 is driven as shown by reference numeral 92 to widen the mold opening amount as shown by reference numeral 91. After that, a mold clamping step is performed and the mold clamping servo motor 13 is driven as shown by reference numeral 93 to narrow the mold opening amount as shown by reference numeral 94. Therefore, the mold clamping force temporarily decreases and then increases as shown by reference numerals 95 and 96.

Therefore, it appears that the injection compression molding method is being carried out properly. However, as the motor position of the mold clamping servo motor 13 is controlled to be constant in the first and second injection steps as shown by reference numerals 101 and 102, the mold opening amount is slightly increased by the injection pressure as shown by reference numerals 103 and 104, and the mold clamping force also changes as shown by reference numerals 105 and 106. Therefore, the mold opening amount in the injection step differs for each molding cycle, which causes variations in the quality of the molded product.

<Another embodiment of the present invention>
Various modifications are possible to the injection molding machine 1 and molds 24, 25 according to this embodiment. A second embodiment is shown in Fig. 6. In this embodiment, the movable mold 25' has a frame 31 pushed up by hydraulic cylinders 41, 41. In this embodiment as well, when the molds 24, 25' are closed to reduce the mold opening amount, the frame 31 is pushed in against the pressing force of the hydraulic cylinders 41, 41.

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

Figure 7 shows a third embodiment. In this embodiment, the fixed mold 24'' and the movable mold 25'' are so-called spigot-type molds. In other words, the fixed mold 24'' has a shape with a relatively high protruding periphery, and the movable mold 25'' has a shape with a recessed periphery. The molds 24'' and 25'' are joined like a spigot, allowing the mold opening injection process and compression process to be carried out.

In the injection compression process according to this embodiment, the mold opening injection process and the compression process are each performed twice. In other words, they are performed in two stages. However, they may be performed in only one stage, or in three or more stages. Regardless of the number of stages, the mold clamping servo motor 13 should be controlled so that the mold opening amount detected by the position sensor 36 is constant in the mold opening injection process.

The invention made by the inventor has been specifically described above based on the embodiments, but the present invention is not limited to the embodiments already described, and it goes without saying that various modifications are possible without departing from the gist of the invention. The multiple examples described above can also be implemented in appropriate combinations.

REFERENCE SIGNS LIST 1 injection molding machine 2 mold clamping device 3 injection device 7 fixed platen 8 movable platen 9 mold clamping housing 10 tie bar 11 toggle mechanism 13 mold clamping servo motor 17 crosshead 19 heating cylinder 20 screw 22 controller 24 fixed mold 25 movable mold 30 spring 31 frame 36 position sensor 38 pin 39 detection piece 41 hydraulic cylinder

Claims (24)

a mold opening and injection process in which the mold is opened by a mold clamping device and an injection material is injected;
a compression process of driving the mold clamping device to narrow the mold opening amount of the mold after the mold opening and injection process,
In the mold opening and injection step, a mold opening amount of the mold is detected by a position sensor provided in the mold, and the mold clamping device is controlled based on the detection result of the position sensor so that the mold opening amount is constant;
The compression process includes a mold opening stage in which the mold clamping device is driven to increase the mold opening amount of the mold, and a compression stage in which the mold clamping device is driven after the mold opening stage to decrease the mold opening amount of the mold. The injection compression molding method according to claim 1, wherein the injection of the injection material is continued during the compression step. The injection molding method according to claim 1 or 2, wherein the clamping mechanism of the clamping device is a toggle mechanism. The injection compression molding method according to any one of claims 1 to 3, wherein the clamping device is driven by a servo motor. The injection compression molding method according to any one of claims 1 to 4, in which one mold opening injection step and one compression step constitute one injection compression step, and the injection compression step is repeated two or more times. The injection compression molding method according to any one of claims 1 to 5, wherein the position sensor is a contact sensor. The injection compression molding method according to any one of claims 1 to 6, wherein the position sensor is a non-contact sensor. The injection compression molding method according to any one of claims 1 to 7, wherein the mold has a built-in spring that rebounds against the closing of the mold. a platen on which a die is provided;
a position sensor provided in the mold to detect an amount of opening of the mold;
A control unit,
When injection compression molding is performed, the control unit includes a mold opening and injection process in which an injection material is injected while the mold is in an open state, and a compression process in which the mold opening amount of the mold is narrowed after the mold opening and injection process,
In the mold opening and injection step, a mold opening amount is controlled to be constant based on the detection result of the position sensor,
The clamping device is adapted to control, in the compression process, a mold opening stage in which the mold platen is driven to increase the mold opening amount of the mold, and a compression stage in which the mold platen is driven after the mold opening stage to decrease the mold opening amount of the mold.
The clamping device according to claim 9, wherein the injection of the injection material is continued during the compression process. The clamping device according to claim 9 or 10, wherein the clamping mechanism of the clamping device is a toggle mechanism. The clamping device according to any one of claims 9 to 11, wherein the clamping device is driven by a servo motor. The clamping device according to any one of claims 9 to 12, in which one mold opening injection process and one compression process constitute one stage of injection compression process, and the injection compression process is repeated two or more stages. The clamping device according to any one of claims 9 to 13, wherein the position sensor is a contact sensor. The clamping device according to any one of claims 9 to 14, wherein the position sensor is a non-contact sensor. The clamping device according to any one of claims 9 to 15, wherein the mold has a built-in spring that repels the closing of the mold. a mold clamping device in which a mold is provided;
an injection device for injecting an injection material;
a position sensor provided in the mold to detect an amount of opening of the mold;
A control unit,
When injection compression molding is performed, the control unit includes a mold opening and injection process in which an injection material is injected while the mold is in an open state, and a compression process in which the mold opening amount of the mold is narrowed after the mold opening and injection process,
In the mold opening and injection step, a mold opening amount is controlled to be constant based on the detection result of the position sensor,
an injection molding machine that controls a mold opening stage in which the mold clamping device is driven to increase the mold opening amount of the mold, and a compression stage in which the mold clamping device is driven after the mold opening stage to decrease the mold opening amount of the mold, in the compression process. The injection molding machine according to claim 17, wherein the injection of the injection material is continued during the compression process. The injection molding machine according to claim 17 or 18, wherein the clamping mechanism of the clamping device is a toggle mechanism. An injection molding machine according to any one of claims 17 to 19, wherein the clamping device is driven by a servo motor. An injection molding machine according to any one of claims 17 to 20, in which one mold opening injection process and one compression process constitute one stage of an injection compression process, and the injection compression process is repeated two or more stages. The injection molding machine according to any one of claims 17 to 21, wherein the position sensor is a contact sensor. An injection molding machine according to any one of claims 17 to 22, wherein the position sensor is a non-contact sensor. An injection molding machine according to any one of claims 17 to 23, wherein the mold has a built-in spring that repels the mold when it is closed.

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