JP2004188936A - Injection-compression molding equipment for annular molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control accurately the inner pressure distribution of a resin in the inside of the cavity in the injection molding mold for an annular molded article so as for it to be uniform and to enable to stably produce homogeneous molded articles. <P>SOLUTION: The equipment is provided with: the mold 2 of the stationary side and the mold 3 of the movable side which constitute the cavity 1 for molding the annular molded article; the valve gate 1A for injecting the resin material into the cavity in the direction along the center axial line of the annular molded article; and the valve gate pin 7 which opens and closes the valve gate and at the same time, accompanied by the operation of closing the valve gate, applies a pressure on to the resin material inside the cavity in the direction along the center axial line of the annular molded article. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for forming a hollow annular molded product having a center hole therein.
[0002]
[Prior art]
When a precision annular molded product such as a flange, a roller, a gear, and a disk is obtained by injection molding, injection compression molding has conventionally been employed. In the injection compression molding (injection compression molding), after a resin material is injected into a mold cavity, molding is performed by applying a mold clamping force to a movable mold to compress the resin material in the cavity. . When the resin material is once injected into the cavity and then compressed by moving the mold, an average compressive force acts on the molded product, and the precision is low, the internal stress is small, and there is no burnout or void. A molded article can be obtained.
[0003]
As a method for injection molding the above-mentioned annular molded product, as described in Japanese Patent Application Laid-Open No. 2000-167971, hot annular is formed in an annular cavity formed between a fixed mold plate and a movable mold plate. An injection molding method for supplying a resin through a valve gate of a runner is known. The outer periphery of the annular cavity is formed by nests on the fixed mold plate side and the nests on the movable mold plate side, and the inner periphery of the cavity is formed by support pins provided on the fixed mold plate and core pins provided on the movable mold plate. You. The support pin is slidable with respect to the nest on the fixed mold plate side, and the core pin is slid with respect to the cylindrical movable pin slidably arranged with respect to the nest on the movable mold plate side. It is possible. In molding, first, a molten resin is injected into a cavity through a valve gate in a state where a support pin and a core pin abut against each other. Thereafter, the cylindrical movable pin located on the outer periphery of the support pin slides along its axis to close the valve gate, and then cools and solidifies to form an annular molded product.
[0004]
[Problems to be solved by the invention]
In the conventional general injection molding technology (not injection compression molding), after filling the cavity with resin, a predetermined amount of pressure is applied to the resin to hold the pressure. If there is any variation, the pressure may cause variation in the accuracy of the annular molded product between shots. In particular, it is difficult to make the initial pressure uniform over the entire circumference, and there has been a problem that a molded product cannot be formed stably.
[0005]
Further, in the above-mentioned conventional technique, since the movable mold moves at the time of molding, there is a problem in shortening the molding cycle and how to close the gate seal of the resin material to the mold cavity. .
[0006]
In Japanese Patent No. 3108229, as a compression molding apparatus for disk molding, a die member having an inner hole having the same diameter as the central opening of the disk molded product and having a front end portion facing a mold cavity is fixed to a stationary mold. A movable side mold having a tip facing the die member inner hole, the tip being actuated by a hydraulic cylinder device for opening and closing a gate for the resin material flowing into the mold cavity; A compression molding technique of a cutting method is disclosed.
[0007]
The method of compressing the resin by applying a mold clamping force to the movable mold has a problem that the thickness of the molded product changes because the movable mold moves. Further, a method of adjusting the speed of the flow control valve using a hydraulic cylinder device of a movable mold is disclosed, but the thickness of a molded product often fluctuates.
[0008]
Further, when the internal resin pressure fluctuates partially, it is difficult to accurately control the internal resin pressure, and there is a problem that a molded product cannot be molded stably.
Accordingly, the present invention has been made in view of the above-described problems, and an object of the present invention is to accurately control a distribution of a resin internal pressure in a cavity in an injection molding die of an annular molded product to be uniform, The purpose is to be able to stably produce a homogeneous molded article.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems and achieve the object, an injection-compression molding apparatus for an annular molded product according to the present invention comprises a fixed-side mold and a movable-side mold that form a cavity for molding the annular molded product. A mold, a valve gate for injecting a resin material into the cavity in a direction along a central axis of the annular molded product, and opening and closing the valve gate, and closing the valve gate with the operation of closing the valve gate. And a valve gate pin for applying pressure to the resin material in a direction along the center axis of the annular molded product.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described.
[0011]
First, an outline of the present embodiment will be described.
[0012]
The annular molded product injection compression molding apparatus according to the present embodiment includes a fixed mold and a movable mold that constitute a cavity for molding the annular molded product, and a center axis of the annular molded product in the cavity. A valve gate for injecting the resin material in a direction along the direction along the center axis of the annular molded product in the resin material in the cavity with the operation of opening and closing the valve gate and closing the valve gate. And a valve gate pin for applying pressure to the valve.
[0013]
Also, in the injection compression molding apparatus for an annular molded product of the present embodiment, the valve gate pin is formed in a cylindrical shape, and inside the cylindrical shape, an inner peripheral surface of the annular molded product is formed. Preferably, a columnar member is slidably disposed with respect to the valve gate pin.
[0014]
In addition, the injection compression molding method for an annular molded product according to the present embodiment is characterized in that the resin material is injected through a valve gate into a cavity formed between the fixed mold and the movable mold, thereby forming the annular mold. An injection compression molding method of an annular molded article for molding an article, comprising: an injection step of injecting the resin material into the cavity through the valve gate; and a valve gate pin for opening and closing the valve gate. A compression step of applying pressure to the resin material in the cavity in a direction along a central axis of the annular molded product by the valve gate pin in accordance with the operation of closing the gate.
[0015]
In the present embodiment, in an injection molding die for forming an annular molded product by supplying a resin through a valve gate into a cavity formed between a fixed mold plate and a movable mold plate, a resin is formed in a mold cavity. After the injection, the resin material in the cavity is molded by applying pressure directly and smoothly to the cavity by the cylindrical movable valve gate pin of the fixed mold driven by the hydraulic or pneumatic cylinder device. ing. In a commercially available injection molding machine, the set pressure on the molding machine side in a high-speed and high-pressure specification is about 200 MPa. The pressure can be directly transmitted to the cavity by the cylindrical movable valve gate pin (calculation example / valve cylinder diameter: φ60, surface area: 28.27 cm ²⁾ , and when hydraulic pressure source pressure: 3 Mpa is applied, load F = 85 Mpa, Valve gate diameter tip: outer diameter φ10, inner diameter φ9 surface area: load at 0.14 cm ² F = 606 Mpa), load applied near the gate of the cavity: 606 Mpa, which can be approximately tripled.
[0016]
Hereinafter, one embodiment of the present invention will be specifically described.
[0017]
FIG. 1 is a side sectional view showing the structure of an injection mold for an annular molded product according to one embodiment of the present invention.
[0018]
In FIG. 1, reference numeral 1 denotes a cavity in the shape of an annular molded product. 1A is a valve gate which is a supply port of the molten resin to the cavity 1. The outer peripheral surface of the cavity 1 is formed by abutting a core piece 2 provided on the fixed mold plate side with a mold piece 3 provided on the movable mold plate side. The inner peripheral surface of the cavity 1 is formed by mating a support pin 4 provided on the fixed mold plate side with a core pin 5 provided on the movable mold plate side. The support pin 4 is attached to a valve gate type hot runner body (not shown). Reference numeral 6 denotes a valve body, in which a heater is incorporated to keep the internal resin in a molten state at all times. Reference numeral 7 denotes a cylindrical movable pin which is slidably mounted on the valve body, and a concentric support pin 4 is slidably mounted therein. When the support pin 4 moves down, the valve gate 1A is closed, and the supply of the molten resin to the cavity 1 is stopped.
[0019]
Reference numeral 8 denotes a molten resin flow path surrounded by the valve gate body and the movable pin 7. The molten resin is supplied from a molten resin supply source (not shown), and is injected into the cavity 1 through the molten resin flow path 7. Reference numeral 9 denotes a heat insulating ring for preventing heat of the valve body 6 from being transmitted to the core piece 2. In the figure, reference numeral 10 denotes a resin heat insulating portion located at a lower portion of the valve body 6 and surrounded by the valve body 6 and the core piece 2. The resin heat insulating portion 10 is formed in order to prevent the heat of the valve body 6 from being transmitted to the core piece 2. The resin heat insulating portion 10 is hollow at the start of the first molding, and thereafter is filled with the solidified resin.
[0020]
The core piece 2 provided on the fixed mold plate is provided with a conical convex tapered portion 2A surrounding the cavity 1. Further, the mold piece 3 provided on the movable mold plate is provided with a conical concave tapered portion 3A so as to abut the conical tapered portion 2A of the core piece 2. The convex tapered portion 2A and the concave tapered portion 3A correct the positional accuracy of the core piece 2 and the mold piece 3, so that they can always be abutted at the same position as well as the mechanical accuracy. Thereby, the positional accuracy at the time of abutment of the outer peripheral portion of the cavity 1 is remarkably improved. In addition, it is possible to suppress displacement in a plane perpendicular to the mold clamping direction (vertical direction in the drawing) during molding. Further, since the position accuracy of the core piece 2 and the mold piece 3 is improved, the position accuracy of the support pin 4 attached to the core piece 2 and the core pin 5 attached to the mold piece 3 can be greatly improved. . In this embodiment, the core piece 2 has the convex taper 2A and the mold piece 3 has the concave taper 3A. However, the core piece 2 has a concave taper, and the mold piece 3 has a convex taper. It may be formed.
[0021]
A substantially conical concave tapered portion 4A is provided on a surface of the support pin 4 that abuts with the core pin 5, and a substantially conical convex taper portion 5A is provided on a surface of the core pin 5 that abuts with the support pin 4. Is provided. By abutting the concave taper portion 4A and the convex taper portion 5A, the positional accuracy of the support pin 4 and the core pin 5 is corrected by the taper, and the respective axes can be aligned with the center line in design, and The centering accuracy of the inner peripheral portion of (1) is significantly improved. In addition, it is possible to suppress displacement in a plane perpendicular to the mold clamping direction (vertical direction in the drawing) during molding. In this embodiment, the support pin 4 has the concave taper 4A and the core pin 5 has the convex taper 5A. However, the core pin 5 has the concave taper and the support pin 4 has the convex taper. May be.
[0022]
The shapes of the convex tapered portion 2A and the concave tapered portion 3A, and the shapes of the convex tapered portion 4A and the concave tapered portion 5A require design considerations to prevent meshing at the time of butting. That is, if the mating surface of the step is a right angle or an angle close thereto, it is necessary to match the above-mentioned mating portions with extremely high accuracy. In addition, if the curved surface is not a simple curved shape but a complicated curved surface, desired position accuracy and quick positioning can be ensured, but the processing cost is increased.
[0023]
In the present embodiment, the convex taper 2A and the concave taper 3A, and the convex taper 4A and the concave taper 5A are smoothly and accurately abutted by appropriately rounding each vertex of the taper to the C-plane or lightly. Can be made possible.
[0024]
Next, a process of manufacturing an annular molded product using the above-described injection mold will be described with reference to FIGS.
[0025]
FIG. 2 shows a state before the molten resin is injected into the cavity 1. FIG. 3 is a view showing a state where the valve gate 1A is closed after the molten resin is injected into the cavity 1. 2 and 3, the same members as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.
[0026]
First, the movable mold plate and the mold piece 3 attached thereto are moved toward the fixed mold plate and the core piece 2 attached thereto (up and down directions in the figure), and butted at a predetermined pressure. At this time, the core piece 2 and the mold piece 3 are butted while being aligned smoothly and accurately by the convex tapered part 2A of the core piece 2 and the concave tapered part 3A of the mold piece 3.
[0027]
Next, the support pin 4 is slid with respect to the movable pin 7 so as to abut against the core pin 5 in the vertical direction. At this time, the positions of the support pins 4 and the core pins 5 are within a predetermined range due to the alignment of the core pieces 2 and the mold pieces 3 described above. By the concave tapered portion 4A of the support pin 4 and the convex tapered portion 5A of the core pin 5, the support pin 4 and the core pin 5 are smoothly butted so that their axes coincide with each other. Therefore, even if the axis is shifted by the clearance between the support pin 4 and the movable pin 7 and the clearance between the core pin 5 and the mold piece 3, no step is formed on the inner peripheral surface of the cavity 1.
[0028]
Next, from a resin supply source (not shown), the molten resin is fed into the molten resin flow path 8 and flows into the cavity 1 along the direction of the arrow in FIG. At this time, since the molten resin is continuously heated by the heater built in the valve body 6, a stable molten state can be maintained.
[0029]
During the first molding after the mold is closed by the fixed mold plate and the movable mold plate, the molten resin first fills the resin heat insulating portion 10 and then flows into the cavity 1 because the resin heat insulating portion 10 is hollow. After the first molding, the resin in the resin heat insulating portion 10 is solidified, so that the molten resin flows directly into the cavity 1 without passing through the resin heat insulating portion 10.
[0030]
Next, after the cavity 1 is filled with the resin, the movable pin 7 is moved downward in the drawing while sliding with respect to the core piece 2 and the core pin 4. Thus, the valve gate 1A applies the resin material in the cavity 1 directly (smoothly and uniformly) to the end face of the annular molded product from the resin filling direction. At the same time, the valve gate 1A is closed, and the flow of the molten resin Ryu 8 into the cavity 1 is stopped. Although a force is applied to the support pin 4 and the core pin 5 in a direction perpendicular to the mold clamping direction, the positions of the support pin 4 and the core pin 5 shift due to the concave tapered portion 4A of the support pin 4 and the convex tapered portion 5A of the core pin 5. There is no. Similarly, the positions of the core piece 2 and the mold piece 3 do not shift due to the convex taper portion 2A provided on the core piece 2 and the concave taper portion 3A provided on the mold piece 3.
Next, the resin filled in the cavity 1 is cooled by cooling means (not shown). During cooling, a temperature distribution is often formed in the cavity 1, so that a force is applied to the support pins 4 and the core pins 5 in a direction perpendicular to the mold clamping direction. In the present embodiment, the positions of the support pins 4 and the core pins 5 are shifted. There is no.
[0031]
When the cooling is completed, the movable mold plate is moved to open the mold. As a result, the butt between the mold piece 3 and the core piece 2 and between the support pin 4 and the core pin 5 are released. Further, the molded product is ejected from the cavity 1 by an ejector pin (not shown) to be taken out. Thereafter, the mold is closed again and the above process is repeated.
[0032]
According to the present embodiment, the position accuracy at the time of butting of the support pin 4 and the core pin 5 is improved by the butting of the concave tapered portion 4A provided at the support pin 4 and the convex tapered surface 5A provided at the core pin 5. Can be. In addition, it is possible to suppress a shift in a direction perpendicular to the mold clamping direction with respect to an external force generated due to holding pressure and cooling during molding.
[0033]
In addition, by clamping the convex tapered portion 2A provided on the core piece 2 and the concave tapered portion 3A provided on the mold piece 3, the mold clamping accuracy of the core piece 2 and the mold piece 3 can be improved. In addition, it is possible to suppress a shift in a direction perpendicular to the mold clamping direction with respect to an external force generated due to holding pressure and cooling during molding. Further, by improving the positional accuracy of the core piece 2 and the mold piece 3, the position accuracy of the support pin 4 attached to the core piece 2 and the core pin 5 attached to the mold piece 3 can be set within a predetermined range in advance. Can be.
[0034]
Next, in the present embodiment, since the receiving surface when the valve body 6 is disposed on the core piece 2 is received by the heat insulating ring 9, the heat of the heater embedded in the valve body 6 is applied to the core piece 2. It is hard to get through. Since the heated valve body 6 is a metal body, if it is in direct contact with the core piece 2, the heat of the valve body 6 is radiated through the core piece 2 connected to the outside of the mold, and the temperature control of the molten resin is sufficient. Will not be able to. Further, the heat insulating ring 9 also plays a role of stopping the excess resin from flowing out of the resin heat insulating portion 10 in which the resin is filled at the beginning of the injection molding. The heat insulating ring 9 may be organic or inorganic, but is preferably made of a material having heat resistance and low thermal conductivity.
As described above, the support pin 4 and the core pin 5 are in contact with each other at the concave tapered portion 4A and the convex tapered portion 5A. However, since the support pin 4 is close to the heated molten resin, the core pin 5 which is a metal body is used. Heat escapes via the. Therefore, heat radiation was prevented by providing a heat insulating material layer on the surface in contact with both.
[0035]
This heat insulating layer may be provided on both the support pins 4 and the core pins 5 or may be provided on only one of them. Further, it is a heat insulating material, and any organic or inorganic material may be used as long as appropriate durability can be obtained. Examples of the heat insulating material include those having an air layer, for example, powder, fibrous body, porous body, layered body, honeycomb structure, and the like, and the material is ceramics or high melting point resin, for example. , Silicone and engineering plastics. Further, the material and the structure may be appropriately compounded. Means for installing the heat insulating layer include coating and bonding.
[0036]
Next, FIG. 4 is an enlarged view of the periphery of the valve gate 1A in a state where the valve gate 1A is closed after the resin filling is completed.
[0037]
In FIG. 4, reference numeral 7A denotes a clearance between the movable pin 7 and the core piece 2. The movable pin 7 closes the valve gate 1A, and immediately after the injection of the molten resin into the cavity 1 is completed, the molten resin flows through the clearance 7A. Thereafter, the resin in the clearance 7A is in a solidified state and stays in the clearance 7A. Thereby, the clearance 7 </ b> A functions as a heat insulating layer, and suppresses heat radiation from the valve body 6 to the core piece 2.
[0038]
The pressure for compressing the resin material in the cavity 1 is determined by the volume V for compressing the resin material. The compression volume V is adjusted by the sliding distance dimension L of the movable pin 7. is there.
[0039]
The pressurizing time of the movable pin 7 is set by a timer (not shown). The timing of compressing the resin material by the movable pin 7 is adjusted by setting the timer.
[0040]
According to this embodiment, the heat of the valve body 6 heated by the built-in heater can be suppressed from being transmitted to the core piece 2 and the core pin 5. Therefore, it is easy to control the temperature in the circumferential direction of the annular molded product, and it is possible to provide a manufacturing method for obtaining a product with good quality accuracy.
[0041]
Further, by providing a fitting clearance between the support pin 4 provided on the fixed die plate and the cylindrical movable pin 7 for opening and closing the valve gate, it is possible to reduce sliding resistance, and the support pin In addition, durability can be improved by smoothing the movable operation with the movable pin, and wear of the support pin 4 and the movable pin 7 can be suppressed.
[0042]
Furthermore, since the resin layer of the clearance between the movable pin 7 and the core piece 2 has a heat insulating effect, heat radiation from the mold structure surrounding the cavity 1 can be suppressed.
[0043]
【The invention's effect】
As described above, according to the present invention, it is possible to accurately control the distribution of the internal resin pressure in the cavity in the mold for injection molding of an annular molded product to be uniform. Therefore, the filling balance can be improved, and a homogeneous molded article can be stably manufactured.
[Brief description of the drawings]
FIG. 1 is a side sectional view showing a structure of an injection mold for an annular molded product according to an embodiment of the present invention.
FIG. 2 is a sectional view of a mold when a valve gate is opened.
FIG. 3 is a sectional view of a mold when a valve gate is closed.
FIG. 4 is an enlarged view of a valve gate portion.
[Explanation of symbols]
Reference Signs List 1 cavity 2 core piece 2A convex taper part 3 mold piece 3A concave taper part 4 support pin 4A concave taper part 5 core pin 5A convex taper part 6 valve body 7 movable pin 7A clearance 8 molten resin flow path 9 heat insulating ring 10 resin heat insulating part

Claims (1)

A fixed-side mold and a movable-side mold that constitute a cavity for molding an annular molded product,
A valve gate for injecting a resin material into the cavity in a direction along a central axis of the annular molded product,
A valve gate pin for opening and closing the valve gate and applying pressure to the resin material in the cavity in a direction along a central axis of the annular molded product in accordance with an operation of closing the valve gate. Injection compression molding equipment for annular molded products.

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