JP2003311790A - Mold device for injection molding and injection molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold device for molding which shortens or dispenses with a dwelling process and can obtain a molding high in dimensional precision. <P>SOLUTION: Runners 61 which are mutually opened/closed and form a material passage between them when a mold is closed and a fixed mold 32 and a movable mold 33 to be mold bodies for forming a cavity 34 communicating with the runners 61 through a gate 62 are provided. A movable cavity forming member 73 which forms the gate 62 between it and the fixed mold 32 and moves toward the fixed mold 32 to close the gate 62 is provided. The gate 62 is cut by the movement of the movable cavity forming member 73, and the cavity 34 is compressed by the portion of the movement of the member 73. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding die apparatus and an injection molding method for molding a resin.

[0002]

For example, in injection molding of a thermoplastic resin, a molten resin is filled in a cavity of a product shape formed in a mold, and this is cooled and solidified to obtain a product. Is to be molded.

In conventional injection molding, a molding machine performs a measuring step, a filling step and a pressure holding step. Taking an in-line screw type molding machine as an example, in a heating cylinder device, a predetermined amount of molten resin is accumulated in the cylinder body while the rotating screw is retracted (metering step). Next, the screw is advanced to inject the resin from the nozzle at the tip of the cylinder body into the mold to fill the cavity with the resin (filling step). After that, an appropriate pressure is applied to the resin in the cylinder main body by the screw to replenish the resin with shrinkage due to cooling into the cavity (pressure holding step).

On the other hand, the volume of the cavity in the mold is constant. Therefore, the pressure and amount of the resin filled in the cavity are basically determined by the control on the molding machine side. Therefore, if there is an error in the control on the molding machine side, an error will occur in the pressure and amount of the resin filled in the cavity as it is. In order to eliminate this error, it is conceivable to make the control of the screw of the molding machine precise, but there are various factors that cause the error, such as temperature and variations in the properties of the resin itself. For example, there is a long resin passage from the screw to the cavity, but if there is an error that occurs in this resin passage, even if the screw control is precise, there will be an error in the pressure and amount of resin filled in the cavity. This affects the dimensional accuracy of the molded product, so that it is necessary to take a long time in the pressure holding step in order to obtain high dimensional accuracy.

The present invention is intended to solve such problems, and provides a molding die apparatus and an injection molding method which can shorten or eliminate the pressure-holding step and obtain a molded article with high dimensional accuracy. The purpose is to provide.

[0006]

In order to achieve the above-mentioned object, the molding die device according to the first aspect of the invention is opened and closed to communicate with each other at the time of mold closing and the material passage and the material passage through a gate. 1 comprises a plurality of molds forming a cavity
One of the mold bodies is a base body, a mold body portion is provided between the base body and the other mold body so as to be movable in a mold opening and closing direction, and a mold body portion that abuts against the other mold body body and closes the mold body portion. A movable cavity for closing the gate by forming a gate between an urging means for urging the base body in a mold opening direction and the other mold body and moving the gate toward the other mold body. And a forming member.

At the time of molding, first, the two molds are closed by a weak mold clamping force, and the mold main body of one mold and the other mold are closed, and the mold main body of one mold and the base body are closed. With the open, the molding material is supplied to the material passage to fill the cavity. Subsequent to this filling, the molding material is continuously supplied to the mold device, and the pressure of the molding material in the cavity is adjusted.
After that, the mold clamping force is increased to bring the base 1 closer to the mold main body,
The gate is cut by the movement of the movable cavity forming member, and the cavity is compressed by the amount of movement of the movable cavity forming member.

According to a second aspect of the invention, in the first aspect of the invention, the gate is formed by a gap between the tip of the movable cavity forming member and the other mold body.

It is possible to separate the molded product from the material passage by forming a gate by separating the tip of the movable cavity forming member from another mold body and closing the gate by hitting the mold tip with the mold body.

Further, the invention of claim 3 is the invention of claim 2, wherein the tip of the movable cavity forming member is formed to be thin toward the other mold body side.

The resistance to the resin when the movable cavity forming member is moved is reduced, and the gate can be cut reliably.

According to a fourth aspect of the present invention, there is provided an injection molding method comprising a plurality of mold bodies which are opened and closed to form a material passage and a cavity communicating with the material passage via a gate when the mold is closed. Is a base, a mold main body provided between the base and the other mold body so as to be movable in a mold opening and closing direction, and abutting against the other mold body to close the base body. A molding apparatus including a biasing unit that biases a mold opening direction and a movable cavity member that constitutes a part of the cavity and is movable in a mold opening / closing direction is used. In the injection molding method of filling, the gate is formed by a gap between the tip of the movable cavity forming member and the other mold body in a state where the mold body and the other mold body are closed, Molded into cavity After filling the charge, by moving the movable cavity forming member toward the other mold elements, as well as closing the gate, a method for compressing a molding material in the cavity.

According to this method, by moving the movable cavity forming member, the gate can be closed to separate the cavity from the material passage, and the molding material in the cavity is compressed, so that the molding material is solidified. The amount of shrinkage is compensated, so that no holding pressure is required, and a highly accurate molded product can be obtained.

[0014]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. The present embodiment is applied to injection molding using a thermoplastic resin as a molding material, and uses an in-line screw type injection molding machine as shown in FIG. In FIG. 6, 1 is a heating cylinder device which is a material supply device. The heating cylinder device 1 includes a cylinder body 2 having a substantially cylindrical shape.
have. A heater 3 for heating is provided on the outer periphery of the cylinder body 2, and a nozzle 4 is provided at the tip portion (left portion in the drawing). A hopper 5 is provided on the upper rear side of the cylinder body 2.
The screw 6 is housed in the cylinder body 2 so as to be rotatable and axially movable (left and right in the drawing). A piston rod 12 of a hydraulic cylinder 11 is fixedly connected to the rear side of the screw 6. That is, the hydraulic cylinder 11 drives the screw 6 in the axial direction. The screw 6 is driven to rotate by an electric servomotor 13. In order to transmit rotation from the servo motor 13 to the screw 6, a gear 15 for rotation transmission is spline-fitted to a spline cylinder 14 fixed to the outer circumference of the piston rod 12. That is, the gear 15 is prevented from rotating with respect to the screw 6, but can freely move in the axial direction.

Further, 21 is a direct pressure type mold clamping device, and this mold clamping device 21 has a fixed side platen 22 and a movable side platen 23. The movable platen 23 is movable in the left-right direction in the drawing along a tie bar 24, and is driven by a hydraulic cylinder 25 via a mold clamping ram 26. The drive of the hydraulic cylinder 25 is controlled by a drive control device 27 including a servo valve and the mold clamping force can be adjusted. Then, the fixed mold 32 of the mold device 31 is attached to the fixed platen 22, and the movable platen
The movable mold 33 is attached to the 23. The mold clamping device 21 and the heating cylinder device 1 are comprehensively controlled by a control device such as a computer.

Next, the structure of the die unit 31 will be described with reference to FIGS.
It will be described in detail based on. It should be noted that FIGS. 1 and 2 for explaining the operation are simplified for easy understanding, and there are some points that do not match other drawings. Moreover, FIG. 3 and FIG.
In the figure, the resin is shown by thick line hatching. The fixed mold 32 and the movable mold 33, which are a pair of mold bodies, open and close each other by the movement of the movable platen 23, and form a product-shaped cavity 34 between them when the molds are closed.
In the present embodiment, the movable mold 33 is one of the claimed molds, and the fixed mold 32 is another claimed mold. Also,
The product P to be molded is a ring member, and its axial direction is aligned with the mold opening / closing directions of the fixed mold 32 and the movable mold 33.

The fixed die 32 has a fixed side attachment plate 36 attached to the fixed side platen 22 and a fixed die body 37 fixed to the surface of the fixed side attachment plate 36 on the movable die 33 side. There is. Further, a locating ring 39 and a sprue bush 40 are fixed to the fixed side mounting plate 36.
The sprue bush 40 is connected to the nozzle 4 of the heating cylinder device 1 and has a sprue 41, which is a material passage, inside. The sprue bush 40 penetrates the through hole 42 of the fixed mold body 37 to move the mold 33 side. Protruding to.

The movable die 33 is provided with a base body 51 attached to the movable side platen 23. The base body 51 is fixed to the movable side attachment plate 51A and the surface of the movable side attachment plate 51A on the fixed die 32 side. The fixed side receiving plate 51B. The base 51 has a movable mold main body 53, which is a mold main body provided on the fixed mold 32 side via a spacer block 52, and the spacer block 52 is fixed to the base 51. With respect to 51, the movable body 53 is movable. Then, the fixed side mounting plate 36
And a plurality of guide pins 47 are fixed to the fixed die main body portion 37, and the guide pins 47 slidably penetrate the movable die main body portion 53 and the base body 51, whereby the fixed side mounting plate is attached to the fixed die 32. 36 and the fixed mold body 37 are supported so as to be movable in the mold opening and closing direction.

Further, a plurality of urging means 54 for urging the base body 51 and the movable die main body portion 53 so as to pull them apart are provided. The urging means 54 inserts a bolt 55 into the movable side receiving plate 51B of the base body 51, fixes the bolt 55 to the movable die main body portion 53, and connects the movable die main body portion 53 and the movable side receiving plate.
With 51B, bolts 55 are fitted with multiple disc springs 56,
A spacer ring 57 is provided between the head portion 55T of 55 and the movable side receiving plate 51B. The head spring 55T, the spacer ring 57, and the movable side receiving plate 51B come into contact with each other by the bias of the disc spring 56, and there is no gap between the head portion 55T and the spacer ring 57. The gap K with the main body 53 is maximized, and the gap K is regulated so as not to open further, and a gate is formed by the gap between the fixed mold 32 and the tip of the cavity forming member described later at the gap K that is the maximum. ,
The predetermined dimension described later is set by the biasing means 54.

Further, the sprue 41 is provided between the fixed mold body 37 of the fixed mold 32 and the movable mold body 53 of the movable mold 33 which are closed.
A runner 61 that is a material passage that connects the
And a gate 62 is formed.

A protruding plate 63 is supported between the base body 51 and the movable mold body 53 so as to be movable in the mold opening / closing direction.
That is, a plurality of guide pins 64 in the mold opening / closing direction are provided on the base body 51, and the tip ends of the guide pins 64 are slidably inserted into the movable die main body 53, and the guide pins 64 and the protruding plate 63 are The runner ejecting pin 65 for ejecting the solidified resin in the runner 61 is fixed. Further, the protruding plate 63 that is movable in the mold opening / closing direction has its anti-cavity side abutted against the base body 51, and its position on the anti-cavity side is restricted.

As shown in FIG. 5, the runner 61 is formed in a substantially cross shape in a plane, and a flat ring-shaped recess 71 is provided between the fixed die 32 and the movable die 33 on the tip side of the runner 61. In the example, as shown in FIGS. 3, 4 and 5, the recess 71 is formed in the movable mold body 53, and the recess 71 and the cavity 34 are formed.
The gate 62 is formed in the shape of a ring between the two, that is, the gate 62 is formed so as to surround the cavity 34, and the recess 71 is formed so as to surround the gate 62. The movable mold 33 side of the cavity 34 is formed by a central protruding pin 72 and a cavity forming member 73 slidably fitted on the protruding pin 72, and a tip 72S of the protruding pin 72 is formed.
And the tip inner peripheral surface 73S of the cylindrical cavity forming member 73 forms the cavity 34. The protrusion pin 72 and the cavity forming member 73 are both provided in the mold opening / closing direction. Further, the outer peripheral surface 74 of the tip of the cavity forming member 73 is formed in a taper shape, whereby the cavity forming member 73 is formed.
Of the cavity forming member 73 is formed with a tip surface 75 in a direction intersecting with the mold opening / closing direction, and the tip surface of the cavity forming member 73 is formed between the tip surface 75 and the fixed die 32. The formed gap forms the gate 62, and the tip surface 75
The gate 62 is closed by contacting the fixed mold 32. A base end 72K of the protrusion pin 72 is fixed to the base body 51, and a base end 73K of the cavity forming member 73 is fixed to the protrusion plate 63.

On the other hand, the fixed mold 32 side of the cavity 34 is
The tip of the pin body 81 and the tip of a tubular pin body 82 slidably fitted on the pin body 81 are provided facing each other. Further, the pin body 81 is biased toward the movable die 33 by the biasing means 83, and the protruding pin 72 contacts the pin body 81 when the die is closed.

A guide pin 91 is fixed to the fixed mold body 37, and a fitting hole 92 into which the guide pin is slidably fitted is formed in the movable mold body 53.

The heating cylinder device 1, the mold clamping device 21, and the mold device 31 having the above-mentioned configurations, together with a control device such as a computer, perform the steps described below.

Next, the injection molding method will be described. In the heating cylinder device 1, the plasticizing step and the injection step are repeated. In the plasticizing step, the thermoplastic resin supplied from the hopper 5 into the cylinder body 2 is melted and plasticized by heating by the heater 3 and kneading by rotation of the screw 6. Along with this plasticization, the resin is sent forward by the rotation of the screw 6, and is accumulated on the tip side inside the cylinder body 2. Along with that, the screw 6 retracts due to the pressure of the resin. Even during the plasticizing process, the hydraulic cylinder 11
A suitable back pressure is applied to the screw 6 in the forward direction. When it is detected that the screw 6 has retracted to a predetermined position, the screw 6 advances due to the driving of the hydraulic cylinder 11, and the resin on the tip end side in the cylinder body 2 moves to the nozzle 4
And is supplied to the sprue 41 of the mold device 31.
When it is detected that the screw 6 has advanced to a predetermined position, or when the screw 6 has advanced to the forward limit,
The plasticizing step is again performed.

The mold clamping device 21 first closes the fixed mold 32 and the movable mold 33 with a weak constant mold clamping force. At this time, the fixed die 32 and the movable die body 53 of the movable die 33 abut against each other and close. On the other hand, in the urging means 54, the head 55T and the spacer ring
There is no gap between the urging means 54 and 57, and the urging means 54 is in the longest state, that is, the distance K between the base body 51 and the movable die main body 53 is maximum, and when resin is filled in this state, the resin pressure causes The protruding plate 63 can be retracted until it hits the base body 51, and a gap of about 0.1 to 0.2 mm, which is a predetermined dimension, is formed between the fixed die 32 and the tip surface 75 of the cavity forming member 73, and this is formed with the gate 62. Become. On the other hand, the protruding pin 72 is 0.
Even when about 1 to 0.2 mm is retracted, the pin body 81 is moved forward by the biasing means 83 provided on the fixed die 32, and the protruding pin 72 and the pin pair are
The condition with 81 is maintained. Then, in this mold clamping state, the mold clamping force and the force of the biasing means 54 are balanced. In this state, the resin is injected from the heating cylinder device 1 to the sprue 41. This resin is filled into the cavity 34 from the sprue 41 through the runner 61 and the gate 62 (filling step).

Subsequent to this filling step, the mold clamping force remains the same, and in the heating cylinder device 1, the screw 6
Is detected to have advanced to a predetermined position, or the injection process is continued until the screw 6 has advanced to the forward limit, and the pressure of the resin in the cavity 34 is adjusted and becomes constant (pressure adjusting process).

Next, the mold clamping device 21 performs mold clamping with a force stronger than the mold clamping force of the urging means 54. This allows the movable type 33
By moving the base body 51 in the mold closing direction and pushing the protruding plate 63 against the base body 51, the urging means 54 contracts by a predetermined dimension, that is, the interval K narrows by a predetermined dimension, and the cavity forming member 73 and The ejector pin 72 moves and the gate
62 is closed, and the resin in the cavity 34 is compressed by the cavity forming member 73.

After the resin in the cavity 34 and the runner 61 is solidified, the mold is opened, and an unillustrated ejecting rod provided on the mold clamping device 21 side fixes the ejecting plate 63 to the fixed mold.
By pushing toward 32, the runner ejecting pin 65 ejects the resin solidified in the runner 71 and the sprue 41 to release it from the movable mold 33, and the ejecting pin 72, which is a molded product ejecting pin, ejects the molded product P. Movable type 33
Release from. In addition, Runner 71 and Sprue 41
After the resin solidified inside and the molded product P are taken out, the mold is closed again, and the above steps are repeated.

As described above, in this embodiment, according to the first aspect, the runners 61 which are opened and closed to each other and which are material passages between the molds when the molds are closed, and the cavities 34 communicating with the runners 61 through the gates 62 are formed. A plurality of fixed molds 32, which are mold bodies, and a movable mold 33, are provided, and the movable mold 33, which is one mold body, has a base 51, and a mold opening and closing between the base body 61 and other fixed molds 32 that are mold bodies. Of the movable die main body 53 that is provided so as to be movable in the direction and that abuts against the fixed die 32 and closes it; Since the gate 62 is formed between the fixed mold 32 and the movable cavity forming member 73 that closes the gate 62 by moving toward the fixed mold 32, the fixed mold 32 and the movable mold 33 are first weakly clamped during molding. And the movable die body 53 of the movable die 33 and the fixed die 32 are closed, In a state in which the parts 53 and the substrate 51 is opened, to supply the molding material into the runner 61 to fill into the cavity 34. Following this filling, the mold equipment
The supply of the molding material to 21 is continued, and the pressure of the molding material in the cavity 34 is adjusted. After that, the mold clamping force is increased to bring the base body 51 closer to the fixed mold side, the gate 62 is cut by the movement of the movable cavity forming member 73, and the cavity 34 is compressed by the movement amount of the movable cavity forming member 73. As a result, the pressure holding step can be shortened, and a molded product P with high dimensional accuracy can be obtained.

As described above, in this embodiment, the gate 62 is constituted by the gap between the tip surface 75, which is the tip of the movable cavity forming member 73, and the fixed die 32, which is the other die body, according to claim 2. Therefore, the front end surface 75 of the movable cavity forming member 73 is separated from the fixed mold 32 to form the gate 62, and the front end surface 75 hits the fixed mold 32 to close the gate 62, thereby forming the molded product P and the runner 61 serving as a material passage. And can be separated.

Further, in this embodiment, as described above, the movable cavity forming member 73 has a distal end side which is formed slender toward the fixed die 32 side which is another die body. The resistance to the resin when the cavity forming member 73 is moved is reduced, and the gate can be cut reliably.

As described above, in this embodiment, according to the fourth aspect, the runners 61 that are opened and closed to each other and are material passages between the molds when the molds are closed, and the cavities 34 that communicate with the runners 61 through the gates 62 are formed. A plurality of fixed molds 32, which are mold bodies, and a movable mold 33, are provided, and the movable mold 33, which is one mold body, has a base 51, and a mold opening and closing between the base body 61 and other fixed molds 32 that are mold bodies. A movable die main body 53 that is movable in the direction and abuts against the fixed die 32 to close it; an urging means 54 that urges the base body 51 toward the die opening direction with respect to the die main body 53;
In the injection molding method of filling a molding material into the cavity 34 through the gate 62, using the mold device 31 that constitutes a part of the mold 34 and is provided with the movable cavity forming member 73 that is movable in the mold opening / closing direction. With the main body 53 and the fixed die 32 closed, the tip of the movable cavity forming member 73 and the fixed die 32 are closed.
After the gate 62 is formed by the gap between them and the cavity 34 is filled with the molding material, the movable cavity forming member 63 is moved toward the fixed mold 32 to close the gate 62 and mold the inside of the cavity 34. Since the material is compressed, according to this method, by moving the movable cavity forming member 73, the gate 62 can be closed to separate the cavity 34 from the material passage, and the molding material in the cavity 34 is compressed. , The shrinkage due to the solidification of the molding material is compensated,
This eliminates the need for holding pressure, and a highly accurate molded product can be obtained.

Further, as an effect of the embodiment, since the concave portion 71 is formed over the entire circumference of the cavity 34, the resin can be uniformly filled in the cavity 34, and the gate is formed by the movable cavity forming member 73. It is possible to cut 62 smoothly.

The present invention is not limited to the above embodiment, and various modifications can be made. For example,
The gate is not limited to the ring shape shown in the embodiment, and various shapes can be used.

[0037]

According to the first aspect of the present invention, a gate is formed between an urging means for urging the base body toward the mold with respect to the mold main body and the other mold body, and the other structure is also provided. Since it has a movable cavity forming member that closes the gate by moving toward the mold body, the gate is cut by moving the movable cavity forming member, and the cavity is compressed by the amount of movement of the movable cavity forming member. can do.

According to the invention of claim 2, in addition to the effect of claim 1, the gate is constituted by a gap between the tip of the movable cavity forming member and the other mold body. It is possible to separate the molded product from the material passage by forming the gate by separating the tip of the forming member from the other mold and closing the gate by hitting the mold with the other tip.

According to the invention of claim 3, in addition to the effect of claim 2, since the tip of the movable cavity forming member is formed thin toward the other mold body side, the movable cavity forming member moves. The resistance to the resin at that time is reduced and the gate can be cut reliably.

According to a fourth aspect of the present invention, the movable cavity forming member is formed after the gate is formed by a gap between the tip of the movable cavity forming member and the other mold body and the cavity is filled with a molding material. Is a method of closing the gate and compressing the molding material in the cavity by moving the mold toward another mold body. Therefore, the movable cavity forming member is moved to close the gate to close the cavity and the material. Since it can be separated from the passage and the molding material in the cavity is compressed, the amount of shrinkage that accompanies the solidification of the molding material is compensated, and thus the holding pressure becomes unnecessary,
It is possible to obtain a molded product with high accuracy.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a mold device showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the mold device of the above.

FIG. 3 is an enlarged cross-sectional view of the vicinity of the gate, showing the state in which the gate is open.

FIG. 4 is an enlarged cross-sectional view of the vicinity of the gate, showing the state in which the gate is closed.

FIG. 5 is a plan view of the same mold body as the above.

FIG. 6 is a side view, partly in section, showing the entire apparatus used for injection molding.

[Explanation of symbols]

31 Mold equipment 32 Fixed type (other type) 33 Movable type (1 type body) 34 cavity 41 Spool (material passage) 51 Base 53 Movable die body (die body) 54 Biasing means 61 Runner (material passage) 62 gates 73 Cavity forming member 75 Tip surface (tip)

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Claims (4)

[Claims] 1. A plurality of mold bodies which are opened and closed to form a material passage and a cavity communicating with the material passage via a gate when the mold is closed, wherein one mold body comprises a base body and the base body. And a mold body which is movable between the mold body and the other mold body in the mold opening / closing direction, and abuts against the other mold body to close the mold body portion, and urges the base body toward the mold opening direction with respect to the mold body portion. An injection characterized by comprising a biasing means and a movable cavity forming member that forms a gate between the other mold body and closes the gate by moving toward the other mold body. Molding equipment for molding. 2. The injection molding die apparatus according to claim 1, wherein the gate is formed by a gap between the tip of the movable cavity forming member and the other die. 3. The tip of the movable cavity forming member,
The injection molding die apparatus according to claim 2, wherein the die apparatus is formed to be thin toward the other mold body side. 4. A plurality of mold bodies that are opened and closed to form a material passage and a cavity communicating with the material passage through a gate when the mold is closed, and one mold body is a base body and the base body is a base body. And a mold body which is movable between the mold body and the other mold body in the mold opening / closing direction, and abuts against the other mold body to close the mold body portion, and urges the base body toward the mold opening direction with respect to the mold body portion. In an injection molding method for filling a molding material through the gate using a mold device including a biasing means and a movable cavity member that constitutes a part of the cavity and is movable in a mold opening / closing direction, With the mold body and the other mold body closed, the gate is formed by the gap between the tip of the movable cavity forming member and the other mold body, and the cavity is filled with a molding material. After that, the movable By moving the cavity forming member toward the other mold, the gate is closed and
An injection molding method comprising compressing a molding material in the cavity.