JP2004160690A - Method and apparatus for injection molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding method which secures high transfer properties of a transfer surface and obtains a high precision molding with deformation during mold release reduced and an apparatus for the method. <P>SOLUTION: In the injection molding method which forms an empty portion on a non-transfer surface not needing precision, after the suction 15 of the empty portion, the molding 12 is taken out. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an injection molding method and an injection molding apparatus for transferring a surface requiring transfer accuracy with high accuracy by inducing sink marks in portions where accuracy is not required. The present invention relates to a molding method and an injection molding device.
[0002]
[Prior art]
The most common method of molding a plastic molded product is to inject a molten resin into the cavity of a mold and then solidify it by cooling to obtain a molded product. However, in the above-described conventional technology, when molding an uneven molded product, the resin temperature becomes uneven between the thick portion and the thin portion during cooling, and residual pressure is generated in the thin portion, or the thick portion is formed. There was a problem that sink marks occurred.
In the case of thick-walled molded products, shrinkage is likely to occur due to the large volume shrinkage during the resin cooling process. On the other hand, if the filling pressure is increased to prevent the occurrence of shrinkage, residual strain increases, resulting in high precision. There was a drawback that a molded article could not be obtained.
In such a case, the above problem is reduced by increasing the mold temperature during molding to a temperature higher than the softening point of the resin, and gradually cooling the temperature of each part of the molded product as much as possible in the cooling process. There is a problem that the molding cycle becomes longer.
As means for solving such a problem, Japanese Patent Application Laid-Open No. 6-304973 discloses that a ventilation port or a porous member communicating with a compressed gas source is provided on a mold surface in contact with a non-transfer surface of a molded product. Injection molding dies have been proposed which solve the above-mentioned problems by pressing the non-transfer surface with the gas flowing in through the vent or the porous member. According to this technique, a surface requiring transfer accuracy can be transferred with high accuracy by inducing sink marks in a portion that does not require accuracy. Since the molding conditions are low-pressure molding, the adhesion between the molded article and the mold is small, and the mold release is easy.
[Patent Document 1] JP-A-6-304973
[Problems to be solved by the invention]
However, when the mold is opened, a molded product is more likely to be lifted off from the parting surface (tolerance), and when the above technique is applied to the molding of a helical gear having a tooth portion which is a transfer portion on the outer peripheral surface, the end of the tooth surface is required. There is a problem that deformation, scratches, etc. occur in the part.
Therefore, an object of the present invention is to solve the above-mentioned problems, to ensure high transferability of the transfer surface, and to obtain an injection molding method and an injection molding apparatus capable of obtaining a high-precision molded product with little deformation upon release. Is to provide.
[0004]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, according to the invention of claim 1, in the injection molding method for forming a space on a non-transfer surface that does not require accuracy, injecting a molded product after sucking the space, The molding method is the most important feature.
According to the second aspect of the present invention, the space portion is formed by providing a ventilation hole in the mold member constituting the non-transfer surface and applying air to the resin from outside the mold. Is the main feature.
The main feature of the invention according to the third aspect is the injection molding method according to the first aspect, wherein the space is formed by separating a part of the mold member constituting the non-transfer surface from the resin.
According to a fourth aspect of the present invention, the main feature of the injection molding method according to the first aspect is that the space is formed by injecting a gas into a part of the resin constituting the non-transfer surface.
In the invention according to claim 5, the injection molding method according to any one of claims 1 to 4, wherein the space is suctioned within an arbitrary time from after the formation of the space to immediately before the molded product is ejected. Main features.
In the invention according to claim 6, in an injection molding apparatus that injects a molten resin into a mold and takes out a molded product after cooling, a space portion forming means for forming a space portion on a non-transfer surface that does not require accuracy, The most main feature of the injection molding apparatus is provided with suction means for sucking the space and switching control means for switching and controlling the two means.
In the invention according to claim 7, the space forming means is provided with a ventilation hole provided in a mold member constituting the non-transfer surface, and an air supply device provided outside the mold and connected to the ventilation hole. The main feature of the present invention is the injection molding apparatus according to the sixth aspect.
According to an eighth aspect of the present invention, the main part of the injection molding apparatus according to the sixth aspect is that the space forming means is constituted by a separating device for separating a part of the mold member constituting the non-transfer surface from the resin. And
According to a ninth aspect of the present invention, the space forming means is constituted by a gas injection device for injecting a gas into a part of the resin constituting the non-transfer surface. And
According to a tenth aspect of the present invention, the main feature of the injection molding apparatus according to the sixth aspect is that the switching control means is constituted by a solenoid valve controlled by a timer.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing an embodiment of an injection molding apparatus according to the present invention. As shown in FIG. 1, the injection molding apparatus according to the present embodiment includes a fixed mold 1 and a movable mold 2.
A cavity insert 3 is provided inside the fixed mold 1, and a core insert 4 having a transfer surface for forming a toothed portion (for example, a helical shape) on a molded product is provided inside the movable mold 2. Is provided. The cavity insert 3 and the core insert 4 define a molding cavity having a predetermined volume.
The cavity nest 3 is formed with a plurality of gates (pin gates) 5 for injecting and filling molten resin from the injection section of the injection molding machine into the molding cavity. A first temperature adjusting means 7 having a temperature detecting means 6 is provided above the plane of FIG. 1, and a second temperature adjusting means 8 is provided below the plane of FIG.
A core plate 9 is arranged in the movable mold 2, and a cavity plate 10 is arranged in the fixed mold 1. Between the cavity insert 3 and the core insert 4, a gear piece 11 for forming a resin gear molded product 12 is placed. A center core pin 13 is fitted into the center of the resin gear molded product 12.
The injection molding die shown in FIG. 1 includes a space portion forming means (air supply device) 14 for forming a space portion on a non-transfer surface which does not require further accuracy, and a suction means (vacuum pump) 15 for sucking the space portion. And switching control means (electromagnetic valve) 16 for switching and controlling the two means.
FIG. 2 is a schematic perspective view showing a helical gear formed by the injection molding apparatus of FIG. FIG. 3 is a sectional view of the helical gear of FIG. 2 and 3, the helical gear includes a tooth portion 17 (transfer surface), a rim 18, a web (non-transfer surface) 19 and a boss 20, and is formed by injection molding a crystalline resin such as polyacetal. It is integrally molded.
[0006]
FIG. 4 is a schematic view showing an embodiment (side surface of a molded product) of a space portion forming means for forming a space portion on a non-transfer surface. The space forming means is constituted by a vent 21 provided in a mold member constituting the non-transfer surface (web) 19 and an air supply device 14 provided outside the mold and connected to the vent 21. .
The vent hole 21 is formed in a ring shape and has a predetermined area on a surface adjacent to the inner peripheral surface of the rim 18 which is a non-transfer surface in the cavity nest 3 and the core nest 4, and the vent hole 21 is connected to the air supply device 14. Have been. The compressed air is supplied to the molding cavity in response to a control signal from the injection molding machine.
FIG. 5 is a schematic diagram showing an embodiment of the space forming means. The space forming means includes a ventilation hole 21 provided in a mold member constituting the non-transfer surface (web) 19, an air supply device 14 provided outside the mold and connected to the ventilation hole 21, a vacuum pump 15, It is constituted by an air supply device 14 and an electromagnetic valve 16 for controlling switching of the vacuum pump 15.
Also, the air to be applied is not limited to compressed air. For example, a high-pressure nitrogen gas cylinder may be provided to supply the compressed nitrogen gas to the vent.
After the space is formed on the non-transfer surface by the above-described means, suction is performed by a vacuum pump (suction means) 15, and the switching is performed by on / off control by an electromagnetic valve 16 by timer control. This allows the space formed on the non-transfer surface to be reliably and effectively sucked when desired.
[0007]
FIG. 6 is a schematic diagram showing a modification of the space portion forming means. The space forming means for forming a space on the non-transfer surface is constituted by a separating device 22 for separating a part of the mold member constituting the non-transfer surface (web) 19 from the resin. According to this, the means for forming the space portion on the non-transfer surface in the injection molding device is constituted by the separating device for separating a part of the mold member constituting the non-transfer surface from the resin, so that the non-transfer surface is formed. A space (a sink mark) can be reliably generated.
FIG. 7 is a schematic view showing another modified example of the space forming means. The means for forming the space on the non-transfer surface is constituted by a gas injection device 23 for injecting a gas into a part of the resin constituting the non-transfer surface (web) 19. By injecting a gas into a part of the resin constituting the non-transfer surface to form the space, it is possible to surely generate a space (a sink mark) on the non-transfer surface.
In the gas injection molding method of FIG. 7, examples of the gas include an inert gas such as nitrogen, helium, neon, or argon. However, any gas can be used as long as it is inert to the resin.
FIGS. 5, 6 and 7 show the gate 5, the space forming means (air supply device) 14, the suction means (vacuum pump) 15, the switching control means (electromagnetic valve) 16, the teeth (transfer surface) 17, A web (non-transfer surface: a space forming portion) 19, a separation device 22, a gas injection device 23, and a movable piece 24 are shown.
After the space is formed on the non-transfer surface by the above-described means, suction is performed by a vacuum pump (suction means) 15, and the switching is performed by on / off control by an electromagnetic valve 16 by timer control. This allows the space formed on the non-transfer surface to be reliably and effectively sucked when desired.
FIG. 8 is a diagram showing the relationship between air supply, suction, and time. The suction is performed within an arbitrary time from after the formation of the space to immediately before the molded product is ejected, and thereafter, the molded product is ejected.
As a result, it is possible to remove the molded product from the parting surface when the mold is opened without lifting (movement) from the parting surface, and obtain a highly accurate molded product with little deformation during mold release while maintaining high transferability. be able to. In the description, the helical gear has been described as an embodiment, but the present invention is also effective for molding a component having a mirror surface and a fine uneven pattern.
[0008]
【The invention's effect】
As described above, according to the first aspect, in the injection molding method for forming a space on a non-transfer surface that does not require accuracy, the mold is opened by removing the molded product after sucking the space. The floating of the molded product from the parting surface at the time can be prevented, and as a result, a highly accurate molded product with little deformation at the time of mold release can be obtained. According to the second aspect, the mold member constituting the non-transfer surface is provided with a ventilation hole, and air is applied to the resin from outside the mold to form a space portion. A part (a sink mark) can be generated.
According to the third aspect, the space is formed on the non-transfer surface by forming the space by separating a part of the mold member constituting the non-transfer surface from the resin. be able to.
According to the fourth aspect, the space is formed by injecting a gas body into a part of the resin constituting the non-transfer surface, thereby reliably generating a space (a sink mark) on the non-transfer surface. Can be.
According to the fifth aspect, by suctioning the space within an arbitrary time from after the formation of the space to immediately before the protrusion of the formed product, the formed product emerges from the parting surface when the mold is opened (trailing). The phenomenon can be prevented, and as a result, a high-precision molded product with little deformation at the time of mold release can be obtained.
According to the sixth aspect, an injection molding apparatus has a space forming means for forming a space on a non-transfer surface that does not require precision, and a suction means for sucking the space, and switches between both means. Since the switching control means for controlling is provided, it is possible to reliably suck the space formed on the non-transfer surface when desired.
As a result, floating of the molded product from the parting surface when the mold is opened (trailing) is prevented, and a highly accurate molded product with little deformation at the time of mold release is obtained.
According to claim 7, the means for forming a space in the non-transfer surface of the injection molding apparatus is provided with a vent provided in a mold member constituting the non-transfer surface, and a vent provided outside the mold. And an air supply device connected thereto, a space portion (a sink mark) can be easily generated on the non-transfer surface.
According to the eighth aspect, the means for forming the space on the non-transfer surface in the injection molding apparatus is constituted by a separating device for separating a part of the mold member constituting the non-transfer surface from the resin. A space (a sink mark) can be reliably generated on the transfer surface.
According to the ninth aspect, the means for forming the space on the non-transfer surface of the injection molding apparatus is constituted by a gas injection device for injecting a gas body into a part of the resin constituting the non-transfer surface. A space (a sink mark) can be reliably generated on the transfer surface.
According to the tenth aspect, since the switching control means is constituted by the solenoid valve controlled by the timer, it is possible to reliably suck the space formed on the non-transfer surface when desired, and as a result, when the mold is opened. The floating of the molded product from the parting surface can be prevented, and a highly accurate molded product with little deformation at the time of release can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an embodiment of an injection molding apparatus according to the present invention.
FIG. 2 is a schematic perspective view showing a helical gear formed by the injection molding apparatus of FIG. 1;
FIG. 3 is a sectional view of the helical gear of FIG. 2;
FIG. 4 is a schematic view showing an embodiment of a space portion forming means for forming a space portion on a non-transfer surface.
FIG. 5 is a schematic diagram showing an embodiment of a space forming means.
FIG. 6 is a schematic diagram showing a modification of the space forming means of FIG. 5;
FIG. 7 is a schematic diagram showing another modified example of the space portion forming means.
FIG. 8 is a diagram showing the relationship between air supply, suction, and time.
[Explanation of symbols]
1 fixed mold 2 movable mold (mold member)
4 core nesting (mold member)
12 Molded product (resin gear molded product)
14 Space part forming means (air supply device)
15 Suction means (vacuum pump)
16 Switching control means (solenoid valve)
18 Rim 19 Web (non-transfer surface: space formation location)
21 Vent (slit)
22 Separation device 23 Gas injection device

Claims (10)

An injection molding method for forming a space on a non-transfer surface that does not require precision, wherein a molded product is taken out after sucking the space. 2. The injection molding method according to claim 1, wherein a ventilation hole is provided in a mold member constituting a non-transfer surface, and the space is formed by applying air to the resin from outside the mold. 2. The injection molding method according to claim 1, wherein the space is formed by separating a part of the mold member constituting the non-transfer surface from the resin. 2. The injection molding method according to claim 1, wherein the space is formed by injecting a gas into a part of the resin constituting the non-transfer surface. The injection molding method according to any one of claims 1 to 4, wherein the space is sucked within an arbitrary time period after the space is formed and immediately before the molded product is ejected. In an injection molding apparatus in which a molten resin is injected and filled in a mold and a molded product is taken out after cooling, a space portion forming means for forming a space portion on a non-transfer surface which does not require accuracy, and a suction means for sucking the space portion And a switching control means for switching between the two means. The space forming means is constituted by an air hole provided in a mold member constituting the non-transfer surface, and an air supply device provided outside the mold and connected to the air hole. The injection molding apparatus according to claim 6, wherein 7. An injection molding apparatus according to claim 6, wherein said space forming means is constituted by a separating device for separating a part of a mold member constituting a non-transfer surface from the resin. 7. The injection molding apparatus according to claim 6, wherein the space forming means is constituted by a gas injection device for injecting a gas into a part of the resin constituting the non-transfer surface. 7. The injection molding apparatus according to claim 6, wherein said switching control means is constituted by a solenoid valve controlled by a timer.

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