JP2023146336A - Molding method of molded article and injection molding machine - Google Patents

Abstract

To provide a molding method capable of molding a high-quality molded article regardless of a shape of a molded article.SOLUTION: A pair of metal mold (15, 16) is provided with a core (36), and driving is run by core pressing force means (5, 38). Then, the method includes an injection step of injecting an injection material to the pair of metal mold (15, 16), a mold platen clamping step of clamping the metal mold (15, 16) by driving a clamping apparatus (2) after completion of the injection step or in parallel with the injection step and a core compression step of pressing the core (36) by the core pressing force means (5, 38).SELECTED DRAWING: Figure 3

Description

The present invention relates to a molding method and an injection molding machine for molding a molded article by injection molding.

There are various molding methods for molding a molded product using an injection molding machine equipped with a mold clamping device and an injection device, and compression molding is one of them. Compression molding is a method to prevent the injection material injected into the mold cavity from shrinking due to heat shrinkage as it cools and solidifies, causing sink marks and other phenomena. For example, compression molding using mold platen compression There is. In this compression molding method, the mold is clamped to a small mold clamping force, or the mold is left slightly open, and the injection material is injected into the cavity. Next, the mold platen is driven to apply mold clamping force to the mold. As a result, even if heat shrinkage occurs due to cooling, sink marks can be prevented and a molded product with excellent transferability can be obtained.

Japanese Patent Application Publication No. 05-301261

As a compression molding method, for example, as described in Patent Document 1, there is also a compression molding method using core compression in which a core is provided in a mold and the core is driven. The core in the mold can be driven, for example, by an ejector rod of an ejector device. The mold is clamped and the injection material is injected into the cavity. The core is then driven to compress the injected material. In this way, even if the injection material undergoes thermal contraction, the volume inside the cavity is reduced and sink marks can be prevented.

Both mold compression and core compression can prevent sink marks and the like, and can mold a molded product with excellent transferability. However, depending on the shape of the molded product, for example, there is a problem in that it is difficult to prevent sink marks using any of the methods for molded products that have a mixture of thin-walled areas and thick-walled areas.

In the present disclosure, a molding method and an injection molding machine that can mold a high-quality molded product are provided.

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

In the present disclosure, a core is provided in a pair of molds, and the core is driven by a core pressing means. Then, there is an injection process in which the injection material is injected into a pair of molds, a plate clamping process in which the mold is clamped by driving a mold clamping device after the injection process is completed or in parallel with the injection process, and a core pressing process. A core compression step of pressing the core by a means is configured as a molding method.

According to the present disclosure, it is possible to prevent sink marks and obtain a high-quality molded product.

FIG. 1 is a front view showing an injection molding machine according to the present embodiment. 1 is a front cross-sectional view showing a part of an injection molding machine according to an embodiment and a mold according to an embodiment. It is a flow chart explaining the molding method concerning this embodiment. 1 is a front cross-sectional view showing a part of an injection molding machine according to an embodiment and a mold according to an embodiment. 1 is a front cross-sectional view showing a part of an injection molding machine according to an embodiment and a mold according to an embodiment. 5 is a time chart showing each step when the molding method according to the present embodiment is carried out. 5 is a time chart showing each step when the molding method according to the present embodiment is carried out.

Hereinafter, specific embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. For clarity of explanation, the following description and drawings have been simplified where appropriate. In each drawing, the same elements are denoted by the same reference numerals, and redundant explanation will be omitted as necessary. In addition, hatching is omitted in some parts to avoid cluttering the drawings.

This embodiment will be described.
<Injection molding machine>
An injection molding machine 1 according to the present embodiment includes a toggle-type mold clamping device 2 and an injection device 3, as shown in FIG. The mold clamping device 2 is provided with an ejector device 5. The injection molding machine 1 is provided with a control device 4, and the mold clamping device 2, the injection device 3, and the ejector device 5 are controlled by the control device 4.

<Mold clamping device>
The mold clamping device 2 includes a fixed platen 7 fixed to the bed B, a movable platen 8 slidably provided on the bed B, and a mold clamping housing 9. The fixed platen 7 and the mold clamping housing 9 are connected by a plurality of tie bars 11, 11, . . . , and the movable platen 8 is slidable between the fixed platen 7 and the mold clamping housing 9. A mold clamping mechanism, that is, a toggle mechanism 13 in this embodiment, is provided between the mold clamping housing 9 and the movable platen 8. The fixed platen 7 and the movable platen 8 are provided with a fixed mold 15 and a movable mold 16, which are a pair of molds to be described later. The toggle mechanism 13 is provided with a crosshead 14, and when the crosshead 14 is driven, the toggle mechanism 13 bends and extends to open and close the molds 15 and 16. The movable platen 8 of such a mold clamping device 2 is provided with an ejector device 5.

<Injection device>
The injection device 3 includes a heating cylinder 19, a screw 20 provided in the heating cylinder 19, and a screw drive device 22. The heating cylinder 19 is supported by a screw drive device 22, and the screw 20 is driven by the screw drive device 22 in the rotational direction and the axial direction. The heating cylinder 19 is provided with a hopper 23 and an injection nozzle 24. When the heating cylinder 19 is heated and the injection material is supplied from the hopper 23 and the screw 20 is rotated, the injection material is melted and measured. When the screw 20 is driven in the axial direction by the screw drive device 22, the injection material can be injected into the molds 15 and 16.

<Mold>
The fixed mold 15 and the movable mold 16 according to this embodiment will be explained. As shown in FIG. 2, the stationary mold 15 has a relatively large and shallow recess 26 formed at its parting line. A sprue 27 is provided on the stationary side mold 15, and the injection nozzle 24 of the injection device 3 touches it. The sprue 27 communicates via a runner 28 with a gate 30 opened in the recess 26, so that the injection material can be injected.

On the movable mold 16, a table-shaped convex portion 33 having a large area and a relatively low height is formed at the parting line. This convex portion 33 is adapted to be inserted into the concave portion 26 of the stationary mold 15. A recess 34 is formed in a part of the protrusion 33 to a predetermined depth. A core 36 is placed in this recess 34. This core 36 is driven by a core pressing means and pressed toward the parting line. In other words, the cavity is constituted by the recess 26 of the stationary mold 15, the protrusion 33 of the movable mold 16, and the core 36 of the recess 34. In this embodiment, the core pressing means is an ejector device 5 (see FIG. 1), and the core 36 is driven by an ejector rod 38 provided in the ejector device 5.

<Molding method>
The molding method according to the present embodiment is a so-called compression molding method in which the injection material is injected into the cavities of the molds 15 and 16 and then compressed or molded in parallel. The molding method according to the present embodiment includes so-called mold plate compression, in which compression is performed by driving the mold clamping device 2 to apply mold clamping force, and so-called core compression, in which compression is performed by driving the core 36. The feature is that both compression methods are implemented.

The molding method according to this embodiment will be described below. As shown in FIG. 3, a mold closing/clamping process is started (step S01). That is, the control device 4 drives the crosshead 14 in the mold closing direction in the mold clamping device 2 (see FIG. 1). Note that the mold platen compression performed later is a type of mold clamping, and can also be seen as the mold closing/clamping process being performed continuously after step S01. In FIG. 3, this step S01 only defines the start of the mold closing/clamping process.

Next, the control device 4 executes step S02 to check whether the injection start conditions are satisfied. The control device 4 is set with a plurality of setting data regarding mold closing/mold clamping for controlling the mold clamping device 2 and a plurality of setting data regarding injection/pressure holding for controlling the injection device 3. configuration data are controlled in relation to each other. For example, when the position of the crosshead 14 in the mold clamping device 2 reaches a predetermined position and the pair of molds 15 and 16 touch, or when the pair of molds 15 and 16 reach a predetermined position, When the mold approaches the mold opening amount, stop closing the mold. Next, injection is started, etc., which are set by a plurality of setting data. The injection is set such that the screw 20 is driven at a predetermined screw speed.

The conditions for starting injection in this way are defined by a plurality of setting data. Alternatively, it can also be defined with one piece of setting data. Although the control device 4 does not have specific setting data called "injection start conditions," the control device 4 determines whether to start the injection process based on whether one or more conditions based on the setting data are satisfied. In this specification, this will be referred to as "injection start condition" for convenience. In step S02, if the control device 4 determines that the injection start conditions are satisfied, the process proceeds to step S03. If it is determined that the conditions are not satisfied, step S02 is repeated.

The control device 4 starts the injection process in step S03. That is, the screw 20 is driven at the set screw speed. The injection process can be controlled in various ways by setting a plurality of setting data. For example, control can be performed using only one screw speed, or it can be divided into multiple stages and sequentially controlled at a plurality of different screw speeds. Furthermore, the timing of completion of the injection process can be controlled in various ways. That is, the injection process may be completed before the platen compression, which will be described later, is started, or the injection process may be continued and completed for a while after it has started. In other words, the completion of the injection process is also set by one or more setting data, so there are various patterns. Step S03 in FIG. 3 defines only the start of the injection process.

FIG. 4A shows how the injection material is injected into the cavities 40 within the molds 15 and 16 during the injection process. In the example shown in FIG. 4A, the molds 15 and 16 are closed, that is, they touch each other to the extent that no mold clamping force is generated, and the injection process is started assuming that the injection start condition is satisfied. has been done. Further, the injection process is completed when the cavity 40 is filled with the injection material. The injection material filled in the cavity 40 is thick in the vicinity of the recess 34, but thin in other parts.

Next, the control device 4 executes step S04 shown in FIG. 3 to check whether the mold platen compression start conditions are satisfied. Similar to the injection start conditions, the control device 4 does not have specific setting data for the mold compression start conditions. However, one or more setting data set in the control device 4 constitute a condition as to whether or not it is possible to start mold plate compression. In step S04, the control device 4 checks whether the mold platen compression start conditions are satisfied. If the mold platen compression start conditions are met, the process moves to step S05. If not satisfied, step S04 is repeated.

The control device 4 starts mold platen compression in step S05. That is, the crosshead 14 is driven to push the movable platen 8 toward the fixed platen 7. This increases the clamping force in the molds 15 and 16. With regard to platen compression, compression can be performed in one stage or in multiple stages depending on one or more setting data. By performing the mold plate compression, the injection material filled in the cavity 40 is compressed, and sink marks are prevented, particularly in thin-walled areas.

The control device 4 executes step S06. In the control device 4, an engineer sets a specified crosshead position, which is one of the setting data, in advance. The specified crosshead position is a condition for performing core compression, which will be described next, and is setting data that determines that core compression can be performed when the crosshead 14 is in this position. The prescribed crosshead position is a mold touch position, which is a crosshead position where the molds 15 and 16 are closed together with almost no mold clamping force, or a crosshead position smaller than that. This ensures that the molds 15 and 16 are in a closed state. The control device 4 determines whether the crosshead 14 has reached the specified crosshead position in step S06. If it has been reached, the process moves to step S07; otherwise, step S06 is repeated.

The control device 4 starts core compression in step S07. Specifically, the ejector device 5 (see FIG. 1) is driven to press the core 36 with the ejector rod 38. This prevents the injection material from sinking in the recess 34. In other words, sink marks are prevented in the thick portions.

FIG. 4B shows that platen compression and core compression are performed simultaneously. That is, the movable platen 8 is driven in the direction of the fixed platen 7, the clamping force on the molds 15 and 16 is increased, and the core 36 is driven via the ejector rod 38. By performing platen compression and core compression, sink marks can be appropriately prevented in both thin-walled parts and thick-walled parts. Therefore, high quality molded products can be obtained.

Incidentally, in the flowchart of FIG. 3, there is only one condition for starting core compression, that is, whether or not the crosshead 14 has reached the specified crosshead position. However, one of the conditions for starting core compression is that platen compression has started. In the flowchart of FIG. 3, step S06 is executed after mold platen compression is started in step S05, so one of the conditions for starting mold platen compression, which is one of the conditions for starting core compression, has already been satisfied. become.

There are actually two conditions for starting core compression in this way, and these conditions are provided to prevent damage to the ejector rod 38, the core 36, and the molds 15 and 16. For example, if core compression is started before the molds 15 and 16 are closed, or if core compression is started before the mold platen compression begins, a large force will be generated through the core 36. This may act on the ejector rod 38 and damage the molds 15, 16, etc. In order to prevent such a risk, two conditions are provided for starting core compression. Although one of the conditions for starting core compression is that the injection process has started, this is not a problem. This is because mold platen compression is supposed to be carried out after the injection process has started, so if you confirm that mold platen compression has started, it is guaranteed that the injection process has started. be.

FIGS. 5A and 5B show time charts showing the timing at which each step is performed when the molding method according to this embodiment is performed with various setting data. In the example shown in FIG. 5A, the specified crosshead position set in the control device 4 (see FIG. 1) is set to a crosshead position where the mold is in a closed state where no mold clamping force is generated. Further, the injection process is set to start after the mold is in a closed state. In the example shown in FIG. 5A, the crosshead 14 (see FIG. 1) reaches the specified crosshead position at the same time as the mold is closed. In other words, one of the conditions for starting core compression is satisfied.

As shown in FIG. 5A, the injection/holding process is started soon, and after a slight delay, the first stage of platen compression is started. The first stage of core compression is started simultaneously with the start of the first stage of platen compression. This is because the other one of the conditions for starting core compression, the start of platen compression, has been satisfied. In other words, this is because two conditions are met. In the example shown in FIG. 5A, the mold platen compression is performed in the first and second stages, and the core compression is also performed in the first and second stages. After completing the injection and pressure holding process, the molded product is obtained after cooling.

In the example shown in FIG. 5B, the specified crosshead position set in the control device 4 (see FIG. 1) is set to a crosshead position where a certain amount of mold clamping force is generated. Further, the injection process is set to start before the molds 15 and 16 are closed, that is, when they are opened by a predetermined mold opening amount. In the example shown in FIG. 5B, the injection/holding process is started before the mold closes. The mold platen compression is started some time after the injection/holding process is started. This satisfied one condition for starting core compression. Eventually, the crosshead 14 (see FIG. 1) reaches the prescribed crosshead position. Then, since the other condition for starting core compression is satisfied, the first stage of core compression is started. In this example, there is only one stage of platen compression, and the core compression consists of a first stage and a second stage. A molded article is obtained when the injection material is cooled.

<Modification of this embodiment>
This embodiment can be modified in various ways. For example, the core pressing means for driving the core 36 (see FIG. 2) has been described as being the ejector device 5 (see FIG. 1). However, the core pressing means can also be constituted by a piston cylinder unit or the like or by other devices. Furthermore, although it has been described that only one core 36 is provided in the movable mold 16, two or more cores 36 may be provided, or they may be provided in the fixed mold 15. When a plurality of cores are provided, each core may be independently driven by a different core pressing means.

Although the mold clamping device 2 of the injection molding machine 1 according to the present embodiment is a toggle type mold clamping device, it may be a direct pressure type mold clamping device. In this case as well, in order to prevent damage to the molds 15, 16, etc., the conditions for starting core compression are that the molds 15, 16 are closed, and that the mold platen is compressed, as in this embodiment. It is preferable that the

Although the invention made by the present inventor has been specifically explained based on the embodiments above, 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 explained above can also be implemented in combination as appropriate.

1 Injection molding machine 2 Mold clamping device 3 Injection device 4 Control device 5 Ejector device 7 Fixed platen 8 Movable platen 9 Mold clamping housing
11 Tie bar 13 Toggle mechanism 14 Cross head 15 Fixed side mold 16 Movable side mold 19 Heating cylinder 20 Screw 22 Screw drive device 23 Hopper 24 Injection nozzle 26 Recess 27 Sprue 28 Runner 30 Gate 33 Convex part 34 Recess 36 Core 38 Ejector rod 40 Cavity B Bed

Claims (14)

a mold clamping device equipped with mold plates that can be opened and closed with each other;
an injection device that injects the injection material;
A molding method for molding a molded product using a pair of molds provided on the mold plate,
The pair of molds is provided with a core driven by a core pressing means,
The molding method includes an injection step of injecting an injection material into the pair of molds;
a mold clamping step of driving the mold clamping device to clamp the pair of molds after the completion of the injection step or in parallel with the injection step;
A method for molding a molded article, comprising: a core compression step of pressing the core with the core pressing means. The method for molding a molded article according to claim 1, wherein the core compression step is performed at the same time as or after the start of the mold clamping step. The method for molding a molded article according to claim 2, wherein the core compression step is performed after closing the pair of molds. The mold clamping device opens and closes the mold by a toggle mechanism equipped with a crosshead,
Mold closing of the pair of molds is determined based on whether the crosshead position of the crosshead reaches a prescribed crosshead position, and the prescribed crosshead position is reached when the pair of molds touch each other. 4. The method for molding a molded product according to claim 3, wherein the crosshead position is a preset crosshead position that is below a mold touch position that is a crosshead position. 5. The method for molding a molded article according to claim 1, wherein the core pressing means includes an ejector device, and the core is driven by an ejector rod of the ejector device. The method for molding a molded article according to any one of claims 1 to 4, wherein the injection step is performed after closing the pair of molds. The method for molding a molded article according to any one of claims 1 to 4, wherein the injection step starts before the pair of molds are closed. a mold clamping device equipped with mold plates that can be opened and closed with each other;
an injection device that injects the injection material;
a pair of molds provided on the mold plate;
comprising a control device;
The pair of molds is provided with a core driven by a core pressing means,
The control device includes an injection step of injecting the injection material into the pair of molds;
a mold clamping step of driving the mold clamping device to clamp the pair of molds after the completion of the injection step or in parallel with the injection step;
An injection molding machine configured to mold a molded product by performing a core compression step of pressing the core with the core pressing means. The injection molding machine according to claim 8, wherein the control device executes the core compression step at the same time as or after the start of the mold clamping step. The injection molding machine according to claim 9, wherein the control device performs the core compression step after closing the pair of molds. The mold clamping device opens and closes the mold by a toggle mechanism equipped with a crosshead,
The control device is configured to determine whether or not the crosshead position of the crosshead has reached a prescribed crosshead position regarding mold closing of the pair of molds, and the prescribed crosshead position is determined by the crosshead position of the pair of molds. The injection molding machine according to claim 10, wherein the crosshead position is a preset crosshead position that is below a mold touch position, which is a crosshead position when the molds touch each other. The injection molding machine according to any one of claims 8 to 11, wherein the injection molding machine includes an ejector device, and the core pressing means includes the ejector device and drives the core with an ejector rod. . The injection molding machine according to any one of claims 8 to 11, wherein the control device performs the injection step after closing the pair of molds. The injection molding machine according to any one of claims 8 to 11, wherein the control device starts the injection process before the pair of molds are closed.

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