JP2005035140A - Injection molding machine and injection molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding machine constituted so as to reduce the deformation of the molded product by ensuring the highly precise transfer properties of a transfer surface and suppressing a taken-out phenomenon at the time of mold release to enable highly precise molding, and an injection molding method using it. <P>SOLUTION: On the assumption that the injection molding machine has a space part forming means for inducing a sink at the predetermined position of a non-transfer surface requiring no high precision due to a movable mold or a fixed mold so as to form a space part, a mold constituted so that an air sealing means is provided to the region surrounding the space part on a movable or fixed side and a suction means for sucking the space part on the movable side or a pressure means for pressurizing the space part on the fixed side are provided. The suction means or a pressure means is allowed to communicate with the space part through a changeover control means. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
[Industrial application fields]
The present invention relates to an injection molding apparatus and an injection molding method that perform high-precision transfer molding of a surface that requires high accuracy by forming a space in a portion that does not require high transfer accuracy and inducing sinks there. The present invention relates to an injection molding apparatus and an injection molding method capable of transferring a fine uneven pattern or the like with high accuracy, and can effectively prevent a decrease in molding accuracy of a molded product caused by a “tray” at the time of mold opening. It can be used for precision molding of optical parts such as precision gears and lenses.
[0002]
[Prior art and its problems]
The most common method for molding a plastic molded product is to inject and fill a molten resin into a cavity of a mold, and then cool and solidify the molded product to mold the molded product.
However, in this method, when molding an uneven molded product, the resin temperature becomes uneven in the thick and thin portions during cooling, and residual pressure is generated in the thin portion or the thickness is reduced. There is a problem that sink marks occur in the meat part.
In addition, in thick molded products, sinking is likely to occur due to large volume shrinkage during the resin cooling process, and if the filling pressure is increased to prevent this sinking, the residual strain increases, There is a disadvantage that a highly accurate molded product cannot be obtained. In such a case, the above-mentioned problems are reduced by increasing the mold temperature to be higher than the softening point of the resin at the time of molding and gradually cooling so that the temperature of each part of the molded product becomes as constant as possible in the cooling process. However, in this case, there is a problem that the time required for cooling is increased by the amount of the higher mold temperature, and therefore the molding cycle becomes longer. As a means for solving the problem that the molding cycle becomes long in this way, a molding port is provided by providing a vent hole communicating with a compressed gas source on the mold surface in contact with the non-transfer surface of the molded product or by disposing a porous member. There has been proposed an injection mold that solves the above problem by introducing gas into the non-transfer surface of a product through the vent or a porous member (Japanese Patent Laid-Open No. 6-304973). In the case of this injection mold, gas is introduced, and a space due to sink marks is formed where sink marks occur.
[0003]
In the above prior art, it is possible to avoid sink marks on surfaces that require high transfer accuracy by inducing sink marks in parts that do not require high accuracy. Therefore, the adhesive force between the molded product and the mold is small, and the mold release is easy. However, on the other hand, because of the low-pressure molding, when the mold is opened, the molded product is easily taken up by the fixed core insert and lifted from the molding surface of the movable core insert (so-called “Trare phenomenon”). There is a high possibility that the molded product moves with respect to the molding surface of the movable core container and is separated from the molding surface before it is protruded from the movable core container.
Therefore, when the conventional molding technique is applied to, for example, a Hasuba gear molding having a tooth portion whose outer peripheral surface is a transfer portion, the tooth surface of the molded product moves and separates from the tooth forming shape surface of the movable core insert. As a result, there is a problem that deformation, scratches, etc. occur at the end of the tooth surface.
[0004]
[Patent Document 1] Japanese Patent Application Laid-Open No. 6-304973
[Problems to be solved by the invention]
For the purpose of solving the above problems, the present invention secures high-precision transferability of the transfer surface and suppresses the deformation phenomenon at the time of mold release, thereby reducing the deformation of the molded product. The object is to devise an injection molding apparatus and an injection molding method capable of molding.
[0006]
[Measures taken to solve the problem]
[Solution 1] (Corresponding to Claim 1)
The means 1 of the present invention for solving the above problem is such that sinks are induced at a predetermined position of the non-transfer surface that does not require high precision by the movable side mold and the fixed side mold, and a space portion is formed. On the premise of an injection molding apparatus having a space forming means, the following (A) and (B) are used.
(A) Add a mold provided with a gas sealing means in a region surrounding the space part on the movable side or the fixed side, a suction means for sucking the space part on the movable side, or a space part on the fixed side. It has a pressurizing means to press.
(B) The suction means or the pressurizing means is communicated with the space through the switching control means.
Further, the above-mentioned “space portion forming means” is a gas introducing means for introducing a gas regulated to the predetermined position in order to induce sink at a predetermined position, causing a sink at the predetermined position. As a result, the space is formed in that portion.
[Action]
Gas is introduced into a predetermined position by the space portion forming means on the non-transfer surface of the mold (a surface that is not a transfer molding surface with high transfer accuracy) by the space portion forming means, and sinks are induced to the predetermined position. A space portion due to sink marks is formed between the molded product and the mold surface.
The space portion on the movable side or the fixed side is surrounded and sealed by the gas sealing means, and a suction means or a pressure means is communicated with the space portion sealed by the gas sealing means. Therefore, if the switching control means controls the space portion to be sucked or pressurized by the suction means or pressurizing means (the above requirement (I)), the molded product is sucked into the movable mold (core insert). Or pressed from the fixed side and brought into close contact with the movable mold, and this state is maintained until the mold is opened.
Therefore, the molded product does not move with respect to the movable mold (core insert) until the mold is opened, and does not move away from the movable mold. Therefore, deformation and damage of the precision transfer surface of the molded product due to the trail phenomenon are prevented.
[0007]
[Solution 2] (Corresponding to claim 2)
Solution 2 is based on the premise of Solution 1 that the gas sealing means is a convex portion formed integrally with a molded product by an annular groove on the mold forming surface.
[Action]
The annular groove provided on the mold molding surface so as to surround the space portion forms a convex portion integrally with the molded product, and is in a state of being fitted into the annular groove, so that the space The part is sealed by the convex part. Therefore, the gas sealing means is configured easily and easily.
[0008]
[Solution 3] (Corresponding to claim 3)
Solution 3 is based on the premise of Solution 1 that the gas sealing means is composed of a sealing member embedded in the groove of the mold forming surface.
[Action]
Since the sealing member is embedded in the groove of the mold molding surface so as to surround the space portion, a part of the sealing member bites into the non-transfer surface of the molded product. The part is sealed.
Since the said space part is sealed by the sealing member, the sealing performance is more reliable.
In addition, a groove is left in the molded product taken out from the mold by the sealing member, but unlike the case of the solving means 2, no unnecessary protrusions are left in the molded product.
[0009]
[Embodiment 1] (Corresponding to Claim 4)
Embodiment 1 is that the pressurizing means is provided together with the suction means for the solution means 1.
[Action]
Since the pressing force by the pressure means acts on the molded product together with the suction force by the suction means, the adhesive strength of the molded product to the movable mold is strong, and therefore the molded product is more reliably attached to the movable mold until the mold is opened. Retained.
[0010]
Second Embodiment (Corresponding to Claim 5)
Embodiment 2 is that the switching control means for switching between the suction by the suction means or the pressurization by the pressurization means in the solution means 1 is constituted by an electromagnetic valve by timer control.
[Action]
Since the switching control means for switching the suction by the suction means or the pressurization by the pressurizing means is constituted by an electromagnetic valve by timer control, the start timing and stop timing of the suction or pressurization are automatically and accurately set. Therefore, the molded product can be reliably held in the movable mold until the mold is opened, and the delay of the molding cycle due to the suction operation or the pressure operation can be prevented as much as possible.
[0011]
[Solution 4] (Corresponding to claim 6)
The solution means 4 includes a space portion forming means for forming a space portion on a non-transfer surface that does not require high accuracy, a mold provided with a gas sealing means in a region surrounding the space portion, and the space portion on the movable side. On the premise of an injection molding method using an injection molding apparatus having a suction means for sucking the suction means, and the suction means is configured to communicate with the space portion via a switching control means,
After the space part is formed on the non-transfer surface, the space part on the movable side is sucked by the suction means at an arbitrary time from before the molding product is ejected, and then the molded product is ejected from the mold. It is to take out.
[0012]
[Solution 5] (Corresponding to claim 7)
The solution means 5 includes a space portion forming means for forming a space portion on a non-transfer surface that does not require high accuracy, a mold having a gas sealing means in a region surrounding the space portion, and a space portion on the fixed side. Assuming an injection molding method using an injection molding apparatus having a pressurizing means for pressurizing, and the pressurizing means communicates with the space via a switching control means, the non-transfer surface By pressing the fixed-side space with the above-mentioned pressurizing means within an arbitrary period of time after the space is formed and immediately before the molded product is ejected, and then the molded product is ejected from the mold and taken out. is there.
[0013]
[Solution 6] (Corresponding to Claim 8)
The solution means 6 includes a space portion forming means for forming a space portion on a non-transfer surface that does not require high accuracy, a mold having a gas sealing means in a region surrounding the space portion, and a movable space portion. A suction means for sucking and a pressurizing means for pressurizing the space portion on the fixed side, and the suction means and the pressurizing means communicate with the space portion forming means via switching control means provided individually. Assuming an injection molding method using an injection molding device that is supposed to be
The space formed in the movable mold is sucked by the suction means within an arbitrary time after the space is formed on the non-transfer surface and immediately before the molded product is ejected, and the fixed mold is formed. The pressurizing means pressurizes the space, and then the molded product is ejected from the mold.
[Action]
The holding force necessary to securely hold the molded product in the movable mold is ensured by both suction and pressurization, so even if the trare phenomenon is strong, the suction force due to the negative pressure in the space part, due to the positive pressure It is reduced that the applied pressure is concentrated on the local part of the molded product, and therefore local distortion of the molded product due to the suction and pressurization is reduced.
[0014]
Embodiment
Next, an embodiment in which the present invention is applied to gear forming will be described.
As shown in FIG. 1, the injection mold of this embodiment is composed of a fixed mold and a movable mold. The fixed mold has a cavity insert 31 inside, and the movable mold has a gear molding inside. The product has a core insert 21 provided with a transfer surface for forming a tooth shape portion having a Hasuba shape. The cavity insert 31 and the core insert 21 define a molding cavity having a predetermined volume. This gear molded product (Hasuba gear) is composed of a tooth portion 1, a rim 2, a web 3 and a boss 4, and is made of a crystalline resin such as polyacetal, or an amorphous resin such as polycarbonate. Are integrally formed by injection molding.
The cavity nest 31 is provided with a plurality of gates 12 for injecting and filling molten resin from the injection part of the injection molding machine into the molding cavity (see gate trace 12a in FIG. 2).
The cavity insert 31 and the core insert 21 have a ring-shaped ventilation groove on the surface facing the web 3 which is a non-transfer surface, and the ventilation groove forms a space portion S (a space portion generated by sink marks). 8 is connected. By this means 8, a predetermined amount of compressed air adjusted to a predetermined low pressure (for example, 0.6 megapascal) is introduced at a predetermined speed. As a result, sink marks are guided to a predetermined position, and a space portion S is formed.
[0015]
5 to 7 show an embodiment of the means 8 for forming the space S on the non-transfer surface. a) In FIG. 5, the means 8 for forming the space S on the non-transfer surface is provided on the mold member constituting the non-transfer surface and on the outside of the mold. The air supply device 62 is connected to the groove and the air holes 21p and 31p.
Note that the air for inducing sink (compressed air) is supplied to the molding cavity in response to a control signal from the injection molding machine.
b) In FIG. 6 and FIG. 7, the means 8 for forming the space S on the non-transfer surface is constituted by an air supply device 62 for injecting air into a part of the resin constituting the non-transfer surface. It is.
[0016]
In the case of FIG. 5, low pressure air (for example, 0.6 megapascal) is introduced from the air supply device for sink induction on both sides of the movable type and the fixed type, and then the solenoid valve is switched to move the space on the movable side. S is communicated with a vacuum source 61 such as a vacuum tank and sucked with a negative pressure (for example, about 10 kilopascals).
In the case of FIG. 6, low pressure air (for example, 0.6 megapascal) is introduced from the air supply device 62 for sink induction on both sides of the movable type and the fixed type, and then the electric valve is switched and fixed. A high-pressure inert gas (for example, 10 megapascal N ₂ gas) is injected into the space portion S from the gas injection device 63 to pressurize the space portion S of the molded product.
Further, in FIG. 7, sinks are induced on both sides of the movable type and the fixed type to form the space S, and then the electromagnetic valve is switched so that the movable side S is communicated with the vacuum source 61. For example, suction is performed with a negative pressure of about 10 kilopascals, and the fixed-side space portion S is communicated with the gas injection device 63 so that it is pressurized with a high-pressure (for example, 10 megapascal) inert gas (for example, N ₂ gas). Pressurize.
Note that the inert gas is used as the pressurized gas in consideration of the influence on the molded product. If there is no problem even with air, the compressed air from the air supply device 62 can be adjusted to a predetermined pressure to obtain a pressurized gas.
[0017]
About suction or pressurization of the space S by introduction of gas such as air or inert gas, since gas leaks from between the mold and the molded product, sufficient suction effect or pressurization effect is stably maintained, It cannot be secured. For this purpose, the gas sealing means 11 is provided so as to surround the space S. Examples of the gas sealing means 11 are shown in FIGS.
FIG. 3 is an enlarged view of a part of the example of FIG. 1, and an annular groove is provided on the web forming surface (non-transfer surface) of the mold on the movable side and the fixed side so as to surround the space portion. The annular groove is filled with molten resin, whereby two annular convex portions 11a as the gas sealing means 11 are formed integrally with the web 3 of the molded product. The thickness and height of the annular projection 11a in the radial direction must be as much as necessary for sealing between the web and the mold surface, and a general guideline is a thickness of 1.5 mm and a height of 2. It is about 0 mm, and depending on the size of the molded product, the overall shape, and the size of the pressure for suction or pressurization, it is desirable that the size is as small as necessary. In addition, the radial interval between the two annular protrusions 11a and 11a generates a suction holding force or a pressure holding force that can securely hold the molded product by the movable mold to such an extent that the trailing phenomenon can be surely prevented. It must be a thing. In this example of forming a helical gear, the required holding force of the molded product by the movable mold depends on the outer diameter of the gear, the tooth width, the inclination angle of the helical gear, the injection filling pressure of the molten resin, the cooling rate, etc. Different for each molded product.
In FIG. 4, the gas sealing means 11 is composed of O-rings 11b and 11b made of a fluorine-based heat-resistant resin. In this, an annular groove is formed on the molding surface of the movable side mold and the fixed side mold, and an O-ring 11b is fitted into the annular groove, and a part of the O-ring 11b is attached. It is designed to be in a state of being bitten into the web surface of the molded product.
Both of the example of FIG. 3 and the example of FIG. 4 have a very simple structure, which can prevent gas leakage and ensure a predetermined suction force or applied pressure in the space.
[0018]
In this injection molding apparatus, the means for forming the space S on the non-transfer surface 3 is provided in both the fixed mold and the movable mold, the suction means in the space formed on the movable mold side, Pressurizing means are respectively communicated with the space formed on the fixed mold side. Depending on the strength of the torrent phenomenon of the molded product, it is sucked from the movable side (FIG. 5), pressurized from the fixed side (FIG. 6), or sucked from the movable side and fixed from the fixed side. This is because pressure is used in combination (FIG. 7). In the case of suction force, the suction force acts locally on the molded product to cause internal distortion, so there is a limit to strongly sticking the molded product to the movable mold only by moving side suction In addition, when pressure is applied, since the applied pressure acts locally on the molded product and causes internal distortion, the molded product is strongly pressed against the movable mold only by pressing on the fixed side. There may be a limit to adhesion.
Whether the suction means or the pressurizing means is used is selected as appropriate in consideration of the merit of the pressurization, or the suction means and the pressurizing means may be used in combination.
[0019]
Further, switching between the formation operation of the space portion S of the non-transfer surface 3 and the suction operation or pressurization operation of the space portion S is automatically performed by the switching control means 7, and specifically, an electromagnetic valve by timer control This is performed by ON / OFF control of the device. Thereby, the space S formed on the non-transfer surface 3 can be accurately sucked or pressurized at a predetermined time.
The control of suction, pressurization, or a combination of both of the space S is such that the required suction force and pressure are generated at least immediately before the mold opening from the time after the space is formed until just before the molded product is ejected. The process is started within an appropriate time, and is performed until the mold opening is completed, and then the molded product is ejected (see FIG. 8).
In addition, although this Example is a helical gear shaping | molding apparatus, it is the same also about the shaping | molding apparatus which shape | molds articles | goods which have a mirror surface and a fine uneven | corrugated pattern. The suction force, the applied pressure, the start time of suction or pressurization, and the end time thereof are appropriately set according to the individual molded product and depending on the intensity of the Toray phenomenon.
[0020]
【The invention's effect】
The effects of the present invention are summarized for each invention of the claims as follows.
(1) According to the invention of claim 1, the injection molding apparatus comprises a space portion forming means for forming a space portion on the non-transfer surface, and a mold provided with a gas sealing means in a region surrounding the space portion, There is a suction means for sucking the space portion on the movable side and a pressure means for pressurizing the space portion on the fixed side, and the suction means and the pressure means are communicated with the space portion via the switching control means. As a result, the space formed on the non-transfer surface can be reliably sucked or pressurized as a result, so that the so-called trail phenomenon can be prevented and the molded product can be accurately transferred due to the trail phenomenon. Surface deformation and damage can be prevented.
[0021]
(2) According to the invention of claim 2, since the gas sealing means provided in the region surrounding the space portion is formed of a convex portion integrally projecting from the molded product, it has a very simple structure. Gas leakage can be prevented, and suction or pressurization of the space can be performed efficiently.
[0022]
(3) According to the invention of claim 3, since the gas sealing means provided in the region surrounding the space portion is composed of the sealing member embedded in the mold groove shape portion, with a very simple structure, Gas leakage can be prevented, and suction or pressurization of the space can be performed efficiently.
[0023]
(4) According to the invention of claim 4, suction means for sucking the space portion on the non-transfer surface on the movable side and pressure means for pressurizing the space portion on the fixed side are provided in the movable mold and the fixed mold, respectively. Therefore, suction, pressurization, or a combination of both can be selected as appropriate for the space formed on the non-transfer surface.
[0024]
(5) According to the invention of claim 5, the switching control means for switching between the means for forming the space on the non-transfer surface and the suction means and the pressure means is constituted by a solenoid valve by timer control. Therefore, suction or pressurization with respect to the space formed on the non-transfer surface can be accurately controlled at a predetermined time.
[0025]
(6) According to the invention of claim 6, the space portion forming means for forming the space portion on the non-transfer surface and the gas sealing means for the region surrounding the space portion are provided, and the space portion on the movable side is sucked. In an injection molding method using an injection molding apparatus having a suction means, wherein the suction means communicates with the space through a switching control means, and then the molded product is ejected after suctioning the space on the movable side. Therefore, the so-called trailing phenomenon when the mold is opened can be prevented, and deformation and damage due to the trailing phenomenon of the high-precision transfer surface of the molded product can be prevented, thus ensuring a highly accurate molded product with little deformation and damage. Can be molded.
[0026]
(7) According to the invention of claim 7, the space portion forming means for forming the space portion on the non-transfer surface and the gas sealing means in the region surrounding the space portion are provided, and the space portion on the fixed side is pressurized. In an injection molding method using an injection molding apparatus having a pressurizing means, wherein the pressurizing means communicates with the space portion via a switching control means. Because it is ejected and taken out, the so-called trailing phenomenon when the mold is opened can be prevented, and deformation and damage due to the trailing phenomenon of the high-precision transfer surface of the molded product can be prevented, so a highly accurate molded product with little deformation and damage can be obtained. It can be reliably molded.
[0027]
(8) According to the invention of claim 8, the space portion forming means for forming the space portion on the non-transfer surface and the gas sealing means in the region surrounding the space portion are provided, and the space portion on the movable side is sucked. Injection molding using an injection molding apparatus having pressurizing means for pressurizing the suction means and the space on the fixed side, wherein the suction means and the pressurizing means are respectively communicated with the space via the switching control means In the method, after using the suction of the movable side space part and the pressurization of the fixed side space part together, the molded product is ejected and taken out. Therefore, a highly accurate molded product can be reliably molded.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing Example 1. FIG.
FIG. 2 is a front view of a molded product in Example 1.
FIG. 3 is a partially enlarged view showing a gas sealing means in the embodiment of FIG. 1;
FIG. 4 is a partially enlarged view showing another example of the gas sealing means.
FIG. 5 is a cross-sectional view schematically showing the relationship between the space portion on the movable side and the suction means.
FIG. 6 is a cross-sectional view schematically showing the relationship between the space portion on the fixed side and the pressurizing means.
FIG. 7 is a cross-sectional view showing a state in which suction of the movable space portion and pressurization of the fixed space portion are used in combination.
FIG. 8 is a diagram showing a temporal relationship between space formation control and suction or pressurization control.
[Explanation of symbols]
1: helical gear tooth portion 2: helical gear rim 3: helical gear web 4: helical gear boss 5: gear piece 6: resin gear molded product 7: switching control means 8: space portion forming means 9: suction means 10 : Pressurizing means 11: gas sealing means 11a: annular projection 11b: O-ring 12: gate 12a: gate trace 21: core insert 21p: vent hole 22: core plate 31: cavity insert 33: center core pin 61: vacuum source 62: Air supply device 63: Gas injection device

Claims (8)

In an injection molding apparatus having a space portion forming means for allowing sink marks to be formed in a predetermined position of a non-transfer surface that does not require high accuracy and to form a space portion by a movable side mold and a fixed side mold.
A mold provided with a gas sealing means in a region surrounding the space portion on the movable side or the fixed side, a suction means for sucking the space portion on the movable side, or a pressurization for pressurizing the space portion on the fixed side Having means,
An injection molding apparatus characterized in that the suction means or pressurizing means is communicated with the space through a switching control means. 2. The injection molding according to claim 1, wherein the gas sealing means provided in the region surrounding the space is a convex portion formed integrally with the molded product by the annular groove on the molding surface. apparatus. 2. The injection molding apparatus according to claim 1, wherein the gas sealing means provided in the region surrounding the space portion is formed of a sealing member embedded in the mold groove shape portion. 2. The movable mold and the fixed mold are respectively provided with a suction means for sucking the movable space portion of the non-transfer surface and a pressurizing means for pressurizing the fixed space portion. The injection molding apparatus according to 1. 2. The injection according to claim 1, wherein the means for forming the space on the non-transfer surface and the switching control means for switching between the suction means and the pressurizing means are constituted by timer-controlled solenoid valves. Molding equipment. Space portion forming means for forming a space portion on a non-transfer surface that does not require high accuracy, a mold provided with a gas sealing means in a region surrounding the space portion, and suction means for sucking the space portion on the movable side In an injection molding method using an injection molding apparatus, wherein the suction means is adapted to communicate with the space via a switching control means.
After the space is formed on the non-transfer surface, the space on the movable side is sucked by the suction means within an arbitrary period of time after the space is formed, and then the molded product is ejected from the mold. And injection molding. Space portion forming means for forming a space portion on a non-transfer surface that does not require high accuracy, a mold provided with a gas sealing means in a region surrounding the space portion, and pressurization for pressurizing the space portion on the fixed side In an injection molding method using an injection molding apparatus, wherein the pressurizing unit is communicated with the space via the switching control unit,
After a space is formed on the non-transfer surface, the space on the fixed side is pressurized with the above-mentioned pressurizing means at an arbitrary time between before the molded product is ejected, and then the molded product is ejected from the mold. And injection molding. A space portion forming means for forming a space portion on a non-transfer surface that does not require high precision, a mold provided with a gas sealing means in a region surrounding the space portion, and a suction means for sucking the space portion on the movable side And a pressurizing unit that pressurizes the space portion on the fixed side, and the suction unit and the pressurizing unit are respectively communicated with the space unit via a switching control unit provided individually. In an injection molding method using an injection molding apparatus,
The movable-side space portion is sucked by the suction means and the fixed-side space portion is added to the non-transfer surface within an arbitrary time after the space portion is formed and immediately before the molded product is ejected. An injection molding method characterized by pressurizing with a pressure means, and then ejecting a molded product and taking it out of a mold.

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