JP2012006223A - Injection molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection press molding method or an injection compression molding method which can inject a resin into a mold which is as slightly opened, and can stabilize the weight of a finished product in the case that a finished product is continuously molded.SOLUTION: According to this injection molding method, a resin is circulated between an injection unit and a mold cavity under such a state that a mold clamping force is applied as a load to the resin inside the mold cavity, under specific mold clamping conditions following injection completion, and thereby, to make the resin inside the mold cavity reproduce an identical behavior repeatedly. Thus, it is possible to stabilize the weight of a finished product. In addition, the application of the method to an insert molding of a skin material etc. can ensure a safe operation, because the behavior of the resin inside the mold cavity can hardly be adversely affected, even if the thickness of the skin material changes during molding.

Description

  The present invention relates to an injection molding method in which a resin is injected and filled into a mold, and in particular, an injection molding method with little variation in the amount of resin filled in a mold cavity.

Among injection molding methods, there is a technique for slightly opening and closing the mold during resin injection molding. The injection molding method using this technique is called an injection press molding method or an injection compression molding method. Widely known among contractors.
The former injection press molding method, which is one of the injection molding methods, will be explained. After injecting resin into a mold cavity formed larger than the desired product shape, the movable mold is moved in the direction of the fixed mold side. In this method, the resin in the cavity is caused to flow through the mold closing operation, for example, by moving the resin to reach every corner of the mold cavity.
In some cases, this molding method may gradually reduce the volume of the mold cavity in accordance with the thermal contraction of the molten resin after the molten resin has been spread all over the mold cavity.

The latter injection compression molding method, which is one of the injection molding methods, will be described. Generally, a resin is injected into a mold cavity formed in a desired product shape, and the mold is pressed by the pressure of the molten resin. Once the mold is opened, the movable mold is moved in the direction of the fixed mold, etc., and the resin in the mold cavity is made to flow and expand by the mold closing operation, so that the molten resin reaches every corner in the mold cavity. It is a method to spread.
Also, in some cases, this molding method is similar to the injection press molding method described above, and after the molten resin is spread to every corner in the mold cavity, the volume of the mold cavity is further adjusted in accordance with the thermal shrinkage of the molten resin. May be gradually reduced.

  The difference between the above-described injection press molding method and the injection compression molding method is that the injection press molding method is a state in which the mold is slightly opened in advance at the start of injection (a dimension larger than the mold cavity of the desired product shape). ), While the mold is closed during or after the injection of the resin, the injection compression molding method reduces the mold clamping force of the mold clamping device (the mold opens slightly by the injection pressure of the molten resin). (The mold clamping force) is such that the mold is slightly opened by the injection pressure during resin injection, and then the mold is closed.

The two molding methods described above are common in that they have a step of injecting resin into a mold in a slightly opened state (a state where the volume of the mold cavity is larger than the volume of a desired molded product). Furthermore, it is common in that it has a step of finally filling a resin in every corner of the mold cavity by a mold closing operation (an operation for reducing the volume of the mold cavity).
Explaining the advantages of these two injection molding methods, the resin pressure when injecting the molten resin can be reduced, and as a result, the injection unit and the mold clamping device can be downsized along with the reduction in the injection pressure. Advantages such as averaging resin pressure in the mold by filling the resin with the mold clamping operation can be achieved, and when molding a resin with poor fluidity, or do not want to leave stress strain during molding in the product Widely used for molding precision molded products.

Here, the measurement of the resin in the injection unit is usually performed by the position (retraction amount) of the injection screw. However, it is well known to those skilled in the art that there is a limit to accuracy in measuring by the position of the injection screw, and the variation in the amount of resin is relatively large. For example, relying only on the weighing by the position of the injection screw, for example, when the injection molding method is performed in which the entire amount of resin weighed by the injection screw is driven into the mold cavity and the product is molded, the variation in product weight is large. Become.

  Therefore, in a general injection molding method in which the mold is kept closed at the time of resin injection molding, the resin is once filled in the mold cavity by the injection operation, and then the molten resin is filled in the mold by the pressure holding process. As the resin cools, the resin is further supplemented with resin from the injection unit. This is because in the injection molding method having the pressure holding step described above, the amount of resin to be filled in the mold cavity is determined mainly by the volume of the mold cavity, and therefore the mold is closed at the time of resin injection molding. If the injection molding method as it is, the volume of the mold cavity hardly changes during molding, so than the injection molding method that fills the mold cavity with the entire amount of resin measured by the injection screw described above, This is because it is well known to those skilled in the art that the variation in product weight is small.

  In contrast, when the injection press molding method or the injection compression molding method described above is performed, the mold is slightly opened at the time of resin injection. The whole amount of resin will be cut off. For this reason, it has been difficult to stabilize the weight of a continuously molded product at a level equivalent to a general injection molding level in which a mold is not opened at the time of injection. Therefore, when the injection press molding method or the injection compression molding method is performed, it is necessary to pay attention to the filling amount of the resin injected into the mold cavity.

JP-A-8-318553

Patent Document 1 is a technique for adjusting the volume of a mold cavity by measuring the position of a movable mold and using it as a reference in view of the above-described problems of the prior art.
Then, when the volume of the mold cavity reaches a desired size during molding, the shutoff valve is closed to immediately shut off the resin flow inside and outside the mold, thereby bringing the mold cavity into the mold cavity. We are trying to solve the problem of variations in the resin filling amount.

Here, the injection molding method disclosed in Patent Document 1 can be expected to have a certain effect in terms of suppressing variations in the resin filled into the mold cavity.
However, the method disclosed in Patent Document 1 in which the opening amount of the movable mold and the fixed mold, or the distance between the movable board and the fixed board, etc. must be measured is that the mold opening amount sensor is changed every time the mold is replaced. There is a need to reattach or reconfigure the sensor.

In addition, although it is not restricted to the prior art disclosed by patent document 1, when inserting a skin material in a metal mold | die and carrying out injection molding, the kind and thickness of skin material to the quantity of resin with which a mold cavity is filled. Affects. Especially when inserting and molding naturally derived skin materials such as animal skins and tree skins, the thickness of the skin material is not uniform, so even if the amount of resin is constant, the thickness of the product In some cases, the variation of the above becomes larger.
Such animal skins and tree skins are compressed at the time of molding and their thickness dimensions change, so if the resin pressure in the mold cavity is different, the product dimensions and product weight will be greatly affected. And variations will occur.
The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide an injection molding method that is excellent in the weight stability and the like of continuously molded products.

In order to solve the above problems, the resin injection molding method according to the present invention comprises:
(1) An injection molding apparatus equipped with a mold clamping device capable of measuring the mold clamping force is provided with a shut-off valve capable of blocking the resin flowing between the injection unit and the mold cavity, and attached to the mold clamping device. A resin is injected into a mold cavity formed by both male and female molds via a shut-off valve, and the mold clamping force of the mold is set in advance during or after the resin injection. When the value reached, the shutoff valve was controlled to close.

(2) In the injection molding method according to (1), the mold clamping device is a toggle type mold clamping mechanism, and is attached to the mold clamping device when starting injection of resin into the cavity of the mold. With the mold opened slightly, during or after the injection of the resin, the mold clamping force is increased with the mold not fully closed, and after the resin injection is completed and the mold clamping force is After the completion of pressurization, the shutoff valve was controlled to close when the mold clamping force of the mold decreased to a preset value.

(3) In the injection molding method according to (1), the mold clamping device is a toggle type mold clamping mechanism, and when the resin starts to be injected into the cavity of the mold, the toggle is fully extended. In this state, the mold is clamped with the mold slightly opened by the pressure of the resin to be injected and filled, and the mold clamping force is set to a preset value during the injection of the resin. Control was made to close the shut-off valve when it was raised.

(4) In the injection molding method according to (1), the mold clamping device is a toggle type mold clamping mechanism, and when the resin starts to be injected into the cavity of the mold, the toggle is extended. In this state, the mold is clamped in a state where the mold is slightly opened by the pressure of the resin to be injected and filled, and after the injection of the resin is completed, the mold clamping force opens the mold. The shut-off valve was controlled to be closed when it was lowered from a raised state to a preset value.

(5) In the injection molding method according to any one of (1) to (4), a skin material is disposed in a cavity of a mold before starting injection of the resin.

  According to the injection molding method of the present invention, after the injection is completed, the resin in the mold cavity is loaded with the resin between the injection unit and the mold cavity under a specific mold clamping condition. By making it circulate, it controls so that the resin in a metal mold cavity may reproduce the same behavior repeatedly. Then, by closing the shutoff valve with a preset mold clamping force, the amount and pressure of the resin in the mold cavity are accurately reproduced. Therefore, it is excellent in the weight stability of the product to be continuously formed.

Further, if the method of the present invention is used for insert molding of a skin material, for example, even if the thickness of the skin material changes during molding, the behavior of the resin in the mold cavity is hardly affected, so stable operation Is possible.

1 is an overall configuration diagram of an injection molding apparatus according to an embodiment of the present invention. It is a conceptual diagram explaining the state and behavior of resin in the mold apparatus at the time of shaping | molding of the injection press molding method concerning embodiment of this invention. It is a conceptual diagram explaining the state and behavior of the resin in the metal mold | die apparatus at the time of shaping | molding in connection with embodiment of this invention. It is a flowchart explaining the process of the injection molding method concerning embodiment of this invention.

Several preferred examples of embodiments of the present invention will be described below with reference to the drawings.
1 to 4 relate to an embodiment of the present invention, and FIG. 1 is an overall configuration diagram of an injection molding apparatus according to the present invention. 2 and 3 are conceptual diagrams illustrating the state and behavior of the resin in the mold apparatus according to the embodiment of the present invention. FIG. 2 relates to an injection press molding method, and FIG. 3 is an injection compression molding method. It is about. FIG. 4 is a flowchart for explaining the process according to the embodiment of the present invention.

As shown in FIG. 1, the injection molding apparatus 100 used in this embodiment includes a mold apparatus 10, a mold clamping apparatus 20, an injection unit 30, and a control apparatus 60 that controls the mold clamping apparatus 20 and the injection unit 30. It has.
The mold apparatus 10 attached to the mold clamping apparatus 20 includes a fixed mold 3 that is a female mold and a movable mold 4 that is a male mold, and is formed by combining both male and female molds. The mold has a structure in which a mold cavity 15 is formed inside the mold by fitting with a fitting portion having a shear edge structure, that is, a so-called “squeezing structure”.
Note that the above-described fitting portion (sometimes referred to as a “drilling portion”) having a sharp structure is formed over the entire circumference of the mold cavity 15.

In addition, since the mold apparatus 10 is fitted in the hard part as described above, for example, the resin filled in the mold cavity 15 leaks out of the mold apparatus 10 even if a predetermined distance is opened. There is nothing.
For reference, in FIG. 2 (3) described later, between the fixed mold 3 and the movable mold 4, between the parting surfaces extending in a direction substantially perpendicular to the mold opening / closing direction. This distance is described as a separation distance S, which is a numerical value representing the mold opening amount (also referred to as mold opening dimension) of the mold 10.
In the present invention, slightly opening the mold 10 means a mold opening amount so that the resin in the mold cavity does not leak to the outside during molding. For example, the first embodiment shown in FIG. In the form, the fixed mold 3 and the movable mold 4 refer to mold opening dimensions that do not disengage the fitting portion of the squeaky structure.
In the present invention, the state in which the mold 10 is not completely closed means that the parting surfaces extending in a direction substantially perpendicular to the mold opening / closing direction of the fixed mold 3 and the movable mold 4 are not in contact with each other. For example, in FIG. 2 (3), which will be described later, this means a situation where the separation distance S is not zero.

As shown in FIG. 1, the fixed die 3 is attached to the fixed platen 1, and the movable die 4 is attached to the movable platen 2. Therefore, the movable mold 4 can be freely moved back and forth with respect to the fixed mold 3 by operating the mold clamping device 20 described later.

Next, the mold clamping device 20 used in the present embodiment will be described. The mold clamping device 20 shown in FIG. 1 is a toggle type that operates by driving the movable platen 2, the fixed platen 1, the mold clamping cylinder 22, and the mold clamping cylinder 22. The movable platen 2 includes a mold clamping mechanism 8 (sometimes referred to as a toggle mechanism 8) and a hydraulic pressure source (not shown) that supplies a desired hydraulic pressure to the mold clamping cylinder 22. The toggle mechanism 8 is guided by four tie bars 7 installed between them and driven by a mold clamping cylinder 22 so that the movable mold 4 can move forward and backward.

  Further, in the mold clamping device 20 shown in FIG. 1, a mold clamping force sensor L is attached to the tie bar 7, and when the mold 10 is clamped by the mold clamping device 20, the extension amount of the tie bar 7 is detected. Thus, the mold clamping force of the mold 10 by the mold clamping device 20 can be measured. Then, the signal of the measured value of the mold clamping force sensor L is input to the mold clamping control unit of the mold clamping control device 61 provided in the control device 60.

  The method of measuring the mold clamping force at the time of molding is that the method using the mold clamping force sensor L is simple in structure so as to measure and calculate the extension amount of the tie bar 7 as described in the present embodiment. However, the present invention is not limited to this, and other known methods for measuring the mold clamping force may be used.

Here, the control device 60 of the injection molding apparatus 100 shown in FIG. 1 may be referred to as a mold clamping cylinder control valve (a mold clamping CYL control valve) that supplies hydraulic pressure to the mold clamping cylinder 22 by the mold clamping control device 61. ), The mold apparatus 10 can be freely opened and closed, and the mold can be clamped.
In the embodiment shown in FIG. 1, a hydraulic and toggle type mold clamping mechanism is used as the driving device of the mold clamping device 20. However, the present invention is not limited to this. For example, a ball screw and a servo motor are used. An electric mold clamping device or the like may be used.

  Next, as shown in FIGS. 1 and 2, the injection unit 30 includes a barrel 32, a screw 34 built in the barrel 32, a hopper 38 that supplies resin into the barrel 32, and an injection cylinder 40 that moves the screw 34 back and forth. And a hydraulic motor 42 for rotating the screw 34, a hydraulic source (not shown) for supplying desired hydraulic pressure to the injection cylinder 40 and the hydraulic motor 42, and a heater (not shown) are attached to the outer peripheral surface of the barrel 32. Yes.

The injection unit 30 is configured to supply pellet-shaped resin from the hopper 38 into the barrel 32 when the screw 34 is rotated by the hydraulic motor 42, and the supplied pellet-shaped resin is attached to the barrel 32. It is heated by the heated heater and melted by being subjected to a kneading compression action by the rotation of the screw 34 and sent to the front of the screw 34.
Resin melted (sometimes referred to as molten resin) sent to the front of the screw 34 can be injected from the nozzle 39 at the tip of the barrel 32 by the screw 34 advanced by the injection cylinder 40.

  The control device 60 includes a mold clamping control unit 61 that controls the mold clamping device, a mold clamping condition setting unit that sets mold clamping conditions in the mold clamping control unit, an injection control device 63 that controls the injection unit 30, and the The injection control unit is provided with an injection condition setting device for setting the injection conditions.

Here, in the injection molding apparatus 100 shown in FIG. 1, a hot runner is disposed as a resin passage in the mold apparatus 10, and the hot runner is shut on the front end side in the direction toward the mold cavity 15. The off valve 31 is arranged.
In the injection molding apparatus 100 shown in FIG. 1, the above-described configuration enables the resin to flow between the injection unit 30 and the mold cavity 15 with the shut-off valve 31 open. In the closed state, the resin flow between the injection unit 30 and the mold cavity 15 is blocked.

  In the above-described embodiment, the shut-off valve 31 is arranged in the mold apparatus 10. However, the arrangement is not limited to the above, and the injection unit 30, the mold cavity 15, It suffices if it is provided somewhere in the position where the flow of the resin can be blocked. Therefore, for example, the arrangement of the injection nozzle 39 at the tip of the injection unit, the stationary platen 1, or a separate block disposed between the injection unit 30 and the mold apparatus 10 can be changed without departing from the technical idea of the present invention. Is possible.

Hereinafter, a preferred example of the embodiment of the injection molding method according to the present invention will be described as a first embodiment with reference to FIGS. 2 and 4.
The first embodiment is an injection molding method in which the mold is injected in a slightly opened state in advance, and as described above, the so-called injection press molding method is sometimes referred to as an injection molding method. It is the example which applied the method of this invention.

In the first embodiment, first, the mold opening amount is set to 1.0 mm as the initial mold opening amount in the mold clamping condition setting machine in the mold clamping control device 61, and the first mold clamping force is set to 1000 KN, A second mold clamping force 1200KN is set as a mold clamping force for closing the shut-off valve 31. After the above-mentioned preparation is completed, the molding cycle is started, the process of the flowchart shown in FIG. 4 is entered, the process proceeds from the process 4 (1) to the process of FIG. 4 (2), and the mold disposed in the mold clamping device 20 By operating the clamping cylinder 22 and extending the toggle mechanism 8, the movable platen 2 is moved in the direction of the fixed platen 1 and the mold 10 is closed.

In this state, the process proceeds from the process shown in FIG. 4 (3) to the process shown in FIG. 4 (4). The shutoff valve 31 disposed on the front end side of the hot runner is opened, and the molten resin (this embodiment) In the form, polypropylene) is injected. In addition, the behavior of the resin at the time of the process of FIG. 4 (4) is shown in FIG. 2 (1).
Here, the mold cavity size and volume of the mold 10 with the mold opening amount of 1.0 mm are larger than the desired size and volume of the molded product. Therefore, in the mold 10 having a mold opening amount of 1.0 mm, the amount of resin filled in the mold cavity 15 is larger than the resin amount of the desired product.

  In the present embodiment, even if the mold apparatus 10 is slightly opened, the mold apparatus 10 is sealed by a fitting portion having a sudden structure formed between the fixed mold 3 and the movable mold 4. The molten resin in the mold cavity 15 does not leak out of the mold apparatus 10.

Then, after filling the mold cavity 15 with the molten resin, the process proceeds to the process of FIG. 4 (5) to FIG. 4 (6), and the toggle mechanism 8 is extended to increase the clamping force.
An important point in this case is that the first mold clamping force described in the first embodiment is a set value for extending the toggle mechanism 8 and is not an actual measured value of the mold clamping force. .
Generally, in the mold clamping device 20 of the injection molding apparatus 100 using the toggle mechanism 8, the mold clamping force is adjusted by controlling the extension amount of the tie bar 7 by controlling the extension amount of the toggle.
In other words, the mold clamping device 20 using the toggle mechanism 8 usually has a closed position where the mold 10 is touched with zero mold clamping force as a reference position, and the toggle extension amount from the reference position and the tie bar 7 elongation. The mold clamping force is calculated from the amount of extension of the tie bar 7 by calculating the relationship between the amounts in advance and creating data (sometimes referred to as a mold clamping force data table).
Therefore, setting the mold clamping force may mean setting a distance for extending the toggle mechanism 8 from the reference position to a position necessary for generating the desired mold clamping force. In the present embodiment, setting the first mold clamping force means that the toggle mechanism 8 is extended to a position necessary for generating the first mold clamping force.

In other words, in the present embodiment, the toggle mechanism from the touched state of the mold 10 to the position necessary for generating the first mold clamping force in a state where the resin is filled in the mold cavity 15 in the above-described process. 8 is stretched.
In this embodiment, in this state, the link of the toggle mechanism 8 is locked so that the extended toggle mechanism 8 is not bent by the mold opening force.
In a state where the mold 10 is slightly opened and the resin is filled in the mold cavity 15, the toggle mechanism 8 is extended to a position necessary for generating the first mold clamping force described above. Since the tie bar 7 is stretched by a size corresponding to the mold opening dimension as compared with the state where the mold is not opened, the tie bar 7 is greatly increased from the mold clamping force data table, and the preset first mold clamping force is much higher. It grows beyond. At this time, since it is difficult to calculate an accurate mold clamping force from the mold clamping force data table, it is grasped by measuring using a mold clamping force sensor L (sometimes referred to as a sensor L). .

In the first embodiment, even in this state, the mold 10 is not fully closed so that the mold 10 is slightly opened as shown in FIG. 2 (2). Assuming that the mold clamping force is entirely applied to the resin in the mold cavity 15.
As a result, the resin tends to balance while flowing between the injection unit 30 and the mold cavity 15 through the shut-off valve 31.

When the resin in the mold cavity 15 flows backward to the injection unit 30 side via the shut-off valve 31 and the mold opening amount of the mold 10 is slightly reduced, the mold clamping force generated by the toggle mechanism 8 is reduced. Gradually decreases and the pressure drops.
Then, when the mold clamping force measured by the sensor L decreases to a second mold clamping force set in advance (1200 KN in the present embodiment), the process proceeds from the process of FIG. 4 (7) to FIG. 4 (8). Then, by sending a signal from the shut-off valve control device and closing the shut-off valve 31, the resin flow between the injection unit 30 and the mold cavity 15 is blocked.
It should be noted that the second mold clamping force in the present embodiment is a mold clamping force measured by the sensor L and is different from the definition of the first mold clamping force.

Here, FIG. 2 (3) shows a state where the shut-off valve is closed. In the first embodiment, even when the shut-off valve 31 is closed, between the parting surface extending between the fixed mold 3 and the movable mold 4 in a direction substantially perpendicular to the mold opening / closing direction. The distance is set as a separation distance S, and the mold clamping force is continuously applied to the resin. Then, in this state, the process from FIG. 4 (9) to FIG. 4 (12) proceeds to cool the molded product, and then the mold 10 is opened widely to take out the product.

It should be noted that the important factors in carrying out the method of the first embodiment described above are the opening amount of the mold 10 and the mold clamping force applied to the molten resin filled in the mold cavity.
That is, if the mold cavity 15 is filled with a resin based on a certain amount of mold opening, and then the pressure received by the resin filled in the mold cavity is accurately controlled, The amount of resin can be accurately controlled.

  Therefore, according to the first embodiment of the present invention, a mold clamping force is applied to the resin in the mold cavity 15, and the injection unit 30 and the mold cavity are subjected to a predetermined mold clamping force. The flow of resin within 15 is repeatedly reproduced with high accuracy. Then, by closing the shut-off valve 31 with a preset mold clamping force, it is possible to control the amount and pressure of the resin in the mold cavity 15 to be accurately reproduced.

In the first embodiment described above, the mold clamping pressure increase is started after completion of the resin injection. However, the method applicable to the present invention is not limited to this, and the mold clamping pressure increase may be started during the resin injection. However, when the mold clamping pressure increase is started during the injection of the resin, the injection needs to be completed at least before the mold clamping pressure increase is completed and before the shut-off valve closing operation.
In the first embodiment, the first mold clamping force and the second mold clamping force are set and the pressure drop until the resin balances in the mold 10 is taken into account, but depending on the molding situation, Alternatively, only the second mold clamping force may be set, and the shutoff valve 31 may be closed immediately after completion of the pressure increase.

The mold clamping device used for carrying out the present invention is preferably a mold clamping device having a correlation between the opening amount of the mold and the mold clamping force during molding.
This is because the present invention controls the behavior of the resin filled in the mold based on the mold clamping force, but the behavior of the resin filled in the mold is affected by the opening amount of the mold.
If you use a type of clamping device that has a relationship between the opening amount of the mold and the clamping force, you can detect the opening amount of the mold by measuring the clamping force of the clamping device during molding. Therefore, it is preferable as an apparatus for controlling the behavior of the resin in the mold.
In other words, if a mold clamping device of a type having a relationship between the mold opening amount and the mold clamping force is used, the mold clamping force changes by detecting the mold opening amount change of the mold 10. With the tightening force, the behavior of the resin in the mold can be accurately grasped and controlled.

Here, as a mold clamping device of the type having a correlation between the mold opening amount and the mold clamping force described above, for example, a mold clamping device of a hydraulic toggle mechanism, a mold clamping device of an electric toggle mechanism, and hydraulic pressure Examples thereof include a mold clamping device that uses a toggle mechanism for mold clamping pressure increase with an electric hybrid, and an electric direct pressure type mold clamping device.
For the above-described reason, the first embodiment uses a mold clamping device 20 of a hydraulic toggle mechanism 8 provided with a mold clamping force sensor L for measuring a mold clamping force on the tie bar 7 as one of preferable modes.

Next, as one of preferred embodiments according to the present invention, the second embodiment will be briefly described with reference to FIG.
The second embodiment is an injection molding method in which the mold is slightly opened by injection pressure during resin injection by reducing the mold clamping force of the mold clamping device, as described above. This is an example in which the method of the present invention is applied to an injection molding method called an injection compression molding method.

In the second embodiment, using the mold clamping device 20 having a toggle type mold clamping mechanism, first, the mold clamping condition setting machine in the mold clamping control device 61 is set to 1000 KN as the first mold clamping force. As a mold clamping force of 2, KN is set to 1200KN.
In the second embodiment, the first mold clamping force is set small so that the mold is slightly opened by the injection pressure during resin injection.
In the second embodiment, after the molding cycle is started, the movable cylinder 2 is moved in the direction of the stationary platen 1 by operating the mold clamping cylinder 22 disposed in the mold clamping device 20 and extending the toggle mechanism 8. Then, the mold 10 is closed to generate the first mold clamping force.

Then, in a state where the mold 10 is clamped with the first mold clamping force, the shutoff valve 31 is opened, and molten resin (polypropylene in this embodiment) is injected into the mold cavity 15.
The behavior of the resin in this state is shown in FIG. In the process of resin injection progressing, the first mold clamping force loses the resin injection pressure, and the mold 10 begins to open gradually.
In the second embodiment as well, as in the first embodiment described above, even if the mold apparatus 10 is slightly opened, the desired structure formed between the fixed mold 3 and the movable mold 4 is used. Sealed by the fitting portion, the molten resin in the mold cavity 15 does not leak out of the mold apparatus 10.

Here, as shown in FIG. 3 (2), the mold 10 is in a slightly opened state and cannot be fully closed, and under this state, the mold clamping force is within the mold cavity 15. All the resin is loaded. As a result, the resin flows through the shutoff valve 31 between the injection unit 30 and the mold cavity 15 and tries to balance.
In this state, if the extension state of the toggle mechanism 8 is held, the amount of compression increases as the mold 10 is opened during resin injection, and the mold clamping force applied to the mold 10 increases and increases. To do.

  In the second embodiment, when the measured mold clamping force rises to a preset second mold clamping force, the shutoff valve 31 is closed to block the resin flow inside and outside the mold. .

FIG. 3 (3) shows a state where the shutoff valve 31 is closed.
In the second embodiment, after the shutoff valve 31 is closed, the resin in the mold cavity 15 contracts, so that the mold opening amount of the mold 10 is slightly reduced and the mold clamping force is reduced. There is no change in the amount of resin filled in the mold cavity 15. Thereafter, the sufficiently cooled molded product is taken out from the mold 10 as a product.

  According to the second embodiment, as in the first embodiment, the resin in the mold cavity 15 is subjected to a mold clamping force. Under predetermined mold clamping conditions, the injection unit 30 and The flow of resin between the mold cavities 15 is repeatedly reproduced with high accuracy. Therefore, the amount and pressure of the resin in the mold cavity 15 can be accurately controlled by closing the shutoff valve 31 with a preset mold clamping force.

In the second embodiment, if the shut-off valve 31 is not closed during injection, the mold 10 is allowed to flow slightly back toward the injection unit 30 through the shut-off valve 31 after completion of injection. From the state where the mold opening amount is slightly decreased and the mold clamping force generated by the toggle mechanism 8 is increased, the pressure gradually decreases and the pressure drops.
Therefore, not only when the mold clamping force described above increases, but also when the increased mold clamping force decreases to the second mold clamping force set in advance, the shut-off valve 31 is closed to increase or decrease the mold clamping force. A method of blocking the resin flow may be used.

Next, a third embodiment will be briefly described as a preferred embodiment of the present invention.
The third embodiment is a form in which a skin material (a main sheet in the third embodiment) is arranged in a mold before resin injection, and the rest is basically the same as the first embodiment. The injection molding method was carried out through various processes.
Of course, it is possible to employ the same injection molding method as in the second embodiment as an embodiment in which the skin material is disposed.

According to the third embodiment, for example, even if the thickness of the skin material changes during molding, the resin pressure in the mold cavity 15 is adjusted by the mold clamping force. The pressure is almost unaffected. As a result, also in the third embodiment, it is possible to accurately reproduce the amount and pressure of the resin in the mold cavity 15, and the dimensional accuracy of the product molded integrally with the skin material varies. It has the excellent advantage of being small.

  As described above, some preferred examples have been described as embodiments of the present invention. However, it is needless to say that embodiments to which the present invention can be applied are not limited thereto, and are within the scope not departing from the technical idea of the present invention. Can be changed.

  Although the scope of application of the present invention is not particularly limited, it is preferable when adopting an injection press molding method or an injection compression molding method in which variation in the amount of resin filled in the mold cavity becomes a problem for automobile parts or household appliances. The present invention can be applied particularly preferably to an insert molded product in which a skin material such as leather or bark is inserted into a mold cavity and integrated.

DESCRIPTION OF SYMBOLS 1 Fixed platen 2 Movable platen 3 Fixed type 4 Movable type 5 End plate 7 Tie bar 8 Toggle type clamping mechanism (toggle mechanism)
DESCRIPTION OF SYMBOLS 10 Mold apparatus 15 Mold cavity 20 Clamping apparatus 22 Clamping cylinder 30 Injection unit 60 Control apparatus 100 Injection molding apparatus L Clamping force sensor S Separation distance (die opening amount)

Claims (5)

In the injection molding device equipped with a mold clamping device capable of measuring the mold clamping force, a shut-off valve that can shut off the resin flowing between the injection unit and the mold cavity is arranged,
Resin is injected through a shutoff valve into a mold cavity formed by both male and female molds attached to the mold clamping device, and the mold of the mold is injected during the resin injection or after the resin injection is completed. A resin injection molding method in which the shut-off valve is controlled to close when the tightening force reaches a preset value. The mold clamping device is a toggle type mold clamping mechanism, and when the resin is injected into the cavity of the mold, the mold attached to the mold clamping device is opened slightly when the resin is being injected. Or, after the injection is completed, the mold clamping force is increased in a state where the mold does not fully close,
2. The control according to claim 1, wherein the shutoff valve is controlled to be closed when the mold clamping force of the mold decreases to a preset value after completion of injection of the resin and completion of pressurization of the mold clamping force. Injection molding method. The mold clamping device is a toggle type mold clamping mechanism, and when the resin starts to be injected into the cavity of the mold, the mold is moved by the pressure of the resin to be injected and filled with the toggle fully extended. With the mold open slightly, the mold is clamped,
2. The injection molding method according to claim 1, wherein during the injection of the resin, the shutoff valve is controlled to be closed when the mold clamping force of the mold rises to a preset value. The mold clamping device is a toggle type mold clamping mechanism, and when the resin starts to be injected into the cavity of the mold, the mold is moved by the pressure of the resin to be injected and filled with the toggle fully extended. With the mold open slightly, the mold is clamped,
After the completion of the injection of the resin, the shutoff valve is controlled to be closed when the mold clamping force of the mold is lowered from a state increased by opening the mold to a preset value. 2. The injection molding method according to 1.   The injection molding method according to any one of claims 1 to 4, wherein a skin material is disposed in a cavity of a mold before the injection of the resin is started.

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