JPH11262934A - Stringiness preventing roll for injection molding machine and injection molding machine using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To certainly prevent stringiness by a simple means in injection molding. SOLUTION: A stringiness preventing roll 1 from which a pin 20 is projected is incorporated in the nozzle passage 61 of a nozzle 61 and the pin 20 is partially inserted into a sprue from a nozzle opening part 62. Whereupon, since a resin becomes a hollow state at the inlet part of the sprue to become a thin- walled state, the resin becomes easy to receive the effect of heat. As a result, the resin is cooled rapidly as compared with the molten resin in other sprue and becomes easy to cut because the cross-sectional area becomes small and the stringiness thereof is not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic resin injection molding machine, particularly when an open nozzle is used, and an insert for preventing stringing between the nozzle and the sprue, and using the insert. The present invention relates to an injection molding method.

[0002]

2. Description of the Related Art A fixed cylinder and a movable mold are clamped, and a molten resin is supplied from a heating cylinder to a space (hereinafter referred to as a "cavity") for forming a molded product formed on a joint surface of both molds. Injection injection through a nozzle, sprue, runner, gate, cooling the mold and curing the resin, then opening both molds and taking out the cured molded product is the basic process of injection molding. is there.

[0003] In the above process, when the molded product is taken out of the mold, a stringing phenomenon may occur in which the injected resin extends like a thread between the gate opening and the sprue. In particular, this stringing phenomenon tends to occur when the viscosity of the open gate or the resin is low.

For example, as shown in FIG. 8, a mustache 70 generated by this stringing is removed integrally with the sprue 80. However, if the stringing becomes longer, the mustache 70 is cut off in the middle and the molded product is taken out. Later, a mustache hangs down from the gate opening and a so-called nose drop phenomenon occurs.

[0005] When the next molding is performed in this state, the drooping whiskers are mixed with the newly injected molten resin into the cavity, which has an adverse effect on the molding quality, or causes the next fixed-side mold and the fixed-side mold to be mixed. When the mold is clamped, it is caught in the joint surface, making it impossible to completely clamp the mold, or sometimes causing damage to the mold, so it is necessary to constantly monitor the work, which greatly hinders automation. It is a factor.

As a countermeasure, JP-A-6-190869
In the publication, an injection hole in an open nozzle 3 is divided by a narrow partition portion 1 to open a plurality of injection holes 2 and 2a in close proximity to each other to increase the resistance of resin flowing out through the nozzle to cause a nose drop phenomenon. In addition, since the nozzle hole forming portion is separated into two parts, cooling is facilitated, and the beard can be reduced.

Further, there is a method of changing the temperature of the nozzle by wrapping a heater around the outer periphery of the nozzle or installing an electromagnetic induction coil on the outer periphery of the nozzle, and utilizing the temperature difference of the resin to prevent stringing. In other words, usually, when energizing a heater or an electromagnetic induction coil, the temperature of the molten resin inside the nozzle is maintained at an appropriate temperature, and when trying to prevent stringing between the nozzle and the sprue, the nozzle is locally controlled. Due to the forced cooling and the contact between the nozzle and the mold, the temperature of the resin inside the nozzle is temporarily reduced by stopping the power supply and temporarily lowering the temperature of the nozzle due to the cooling effect of the mold. The lowering is easy to cut to prevent stringing.

[0008] In addition, there is a suck-back method. This means that the injection process into the mold is completed, and during the dwelling state, the solid resin dropped from the hopper for the next filling is supplied between the grooves of the screw, and the screw is retracted while rotating. Along with this, the resin is moved forward while melting, pooled in front of the screw in the heating cylinder, and then, when a set amount of molten resin is accumulated, the back pressure is applied to the molten resin. Is slightly retracted without rotating it to reduce the back pressure on the molten resin, thereby facilitating the cutting of the resin between the nozzle and the sprue.

[0009]

However, each of the above stringing prevention methods has the following disadvantages. First, Japanese Unexamined Patent Publication
In the technique disclosed in Japanese Patent No. 190869, it is difficult to process the nozzle, and since the partition portion is thin, there is a problem in strength in injection molding a composite resin material mixed with glass fiber, carbon fiber, or the like.

[0010] In addition, a measure against stringing for controlling the nozzle temperature is that proper temperature control cannot be performed due to a change in the surrounding temperature, and the temperature of the molten resin becomes too low by lowering the nozzle temperature. There is a possibility that the effect may vary, for example, the injection may not be possible.

In the suck-back method, the suck-back distance is slightly different depending on the viscosity of the resin, the temperature of the molten resin, and the like, and it is difficult to set the suck-back method unless a skilled worker is used. In addition, when sucking back, if air enters the tip of the nozzle, the molten resin may be burned, or the air may enter the cavity during the next injection molding, which may cause defects such as silver.

An object of the present invention is to provide a stringing prevention piece which can reliably prevent stringing, has sufficient strength, and can be manufactured at low cost, and an injection molding method performed using this prevention piece. To provide.

[0003]

In order to achieve the above object, according to the first aspect of the present invention, in a stringing prevention piece for an injection molding machine, a resin flow path is formed around the piece, and a resin flow path is formed from the center of the tip. A pin is protruded, and the resin is filled while partially inserting the pin into the sprue through the nozzle hole, thereby preventing stringing between the nozzle and the sprue.

Further, in the invention according to claim 2,
The invention according to claim 1 is characterized in that the outer peripheral surface of the pedestal body is formed on the same inclined surface as the inclined surface of the flow passage in the nozzle, and the resin passages are formed at equal intervals on this inclined surface. .

Further, in the invention according to claim 3,
In the invention according to claim 1, the outer peripheral surface of the pedestal body is formed on the same inclined surface as the inclined surface of the flow path in the nozzle, and the same inclination angle as the inclination of the flow path in the nozzle is formed on the outer peripheral surface of the pedestal at equal intervals. By mounting the protrusions at equal intervals, a resin flow path is formed between the protrusions.

Further, in the invention according to claim 4,
In the invention according to claim 1, the rear of the pin inserted into the nozzle hole is extended, and spacer blades having the same inclination angle as the nozzle flow path are attached to the extended side at equal intervals, whereby the spacer blade is provided. It is characterized in that a resin flow path is formed therebetween.

Further, in the invention according to claim 5,
In the injection molding method for preventing stringing, a pin is inserted from the tip of the nozzle toward the inside of the sprue inlet, and when the resin is filled, the resin in the sprue inlet is formed into a hollow shape by the action of the pin. The present invention is characterized in that the thickness is reduced, the cooling is accelerated, the cutting is facilitated, and thereby stringing is prevented.

In the invention according to claim 6,
The invention according to claim 5, wherein a resin flow path is formed around the circumference, a stringing prevention piece having a structure in which a pin projects from a tip is inserted into the nozzle flow path, and when the nozzle abuts on a sprue, By filling the sprue side with resin from inside the nozzle while the tip of the pin is partially inserted into the sprue inlet, the resin is formed hollow in the sprue inlet to reduce the wall thickness, and the cooling temperature is reduced. Is characterized by speeding up the curing of the resin between the nozzle and the sprue by making the resin more susceptible to the effects of the above.

[0019]

According to the present invention, the stringing prevention piece of the present invention is inserted into the end of the flow path of the nozzle. Since the outer shape of the pedestal of the stringing prevention piece is formed to have the same shape as the slope in which the flow path of the nozzle gradually narrows toward the nozzle opening, the inner diameter of the nozzle at the desired installation position and the outer diameter of the pedestal of the stringing prevention piece are set. Can be installed at any position.

The installation and fixing method is based on the filling pressure during the resin filling,
Is pressed against the cavity toward the nozzle opening,
During the kneading of the resin by the screw, the molten resin is pushed out to the front of the screw, so that a back pressure is always applied to the stringing prevention piece, and it is not necessary to use a special fixing method.

In the injection molding, after the cavity is filled with the molten resin, a pressure is maintained, but at the contact portion between the nozzle opening and the sprue, the pin of the stringing prevention piece protruding from the nozzle opening is inserted into the sprue inlet. Since it has penetrated, the longitudinal section is hollow, that is, a donut shape, and the transverse section has the shape shown in FIG. Therefore, the following operation occurs.

Since the pin has entered the sprue,
Stagnant molten resin becomes hollow when viewed in cross section,
Since the wall thickness is thin, the temperature of the other sprue portion decreases due to the external influence as compared with the molten resin. Since the pin enters the sprue inlet, the stagnant resin becomes hollow, has a small cross-sectional area, and is easily cut. Therefore, when injection molding is performed using the stringing prevention piece of the present invention, the whiskers formed on the sprue are shortened, and long stringing and nose dripping can be prevented.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1, 2 and 3 show examples of the shape of the stringing prevention piece of the present invention. FIG. 1 is a side view of the stringing prevention piece 1 according to claims 1 and 2, FIG. 2 is a perspective view of the stringing prevention piece 2 according to claims 1 and 3, and FIG. And a spacer blade plate 3 which can be installed so that the pin 31 is located at the center of the nozzle and the sprue.
FIG. 4 is a perspective view of a structure having a plurality of pins 2 at the rear of a pin 31 at equal intervals.

An embodiment of the present invention will be described below with reference to the drawings. In this embodiment, a pedestal portion and a pin portion are separately manufactured so as to easily manufacture a stringing prevention piece, and an embodiment in which the pedestal portion and the pin portion are manufactured in combination is presented. Of course, the pin and the pedestal can be manufactured by cutting from one steel material.

[0025]

[Embodiment 1] This embodiment corresponds to claims 1 and 2,
The thread pulling prevention piece 1 according to the present embodiment shown in FIG. 1 will be described with reference to FIGS. FIG. 4 is a front view (A), a side view (B), and a rear view (C) of the pedestal 10 constituting the stringing prevention piece of the present embodiment. The pedestal 10 has a truncated cone shape when viewed from the side, and the inclination angle of the outer periphery is the same as the inclination angle and the inner diameter of the installation location of the nozzle flow path to be inserted. As for the size, the radius of the bottom surface 11 is 12 mm, and the radius of the top surface 12 is 6 m
m, length is 33 mm. Further, a carbon steel for machine use (S55C) was used as the material, and formed by cutting.

At the center of the pedestal 10, a mounting hole 13 penetrating in the axial direction from the bottom surface 11 to the top surface 12 is formed. And a screw hole 15 thicker than the pin hole 14. The screw hole 15 forms a female screw having the same pitch as the set screw 30 for fixing the pin 20. Pedestal 10
In the outer periphery of the nozzle, grooves (resin flow paths) 16 for flowing the molten resin from the rear surface to the front surface of the pedestal 10 in the nozzle were formed at four locations at equal intervals.

FIG. 5 shows a pedestal 10, a pin 20, and a set screw 3.
0 is an assembly drawing. The material of the pin 20 used in the present embodiment is an alloy tool steel (SKD61).
Is constituted by a pin body 21 having a diameter of 2.5 mm and a mounting portion 22 slightly smaller than the diameter of the mounting hole 13 of the pedestal 10, and has a total length of 57 mm. The diameter of the pin body 21 depends on the diameter of the nozzle opening of the nozzle used for injection molding,
The setting is made in consideration of the injection state of the molten resin, the effect of preventing stringing, and the like. Incidentally, the diameter of the nozzle opening 62 using this embodiment is 5.0 mm.

The set screw 30 has a female screw in the mounting hole 13 of the pedestal and a male screw screwed on the outer periphery. Assembly is
First, the pins 20 are inserted into the mounting holes 13 from the bottom surface 11 of the pedestal 10. When the tip of the pin body 21 penetrates the pin hole 14 and the pin 20 is installed at a position where the mounting portion 22 contacts the pin hole 14, the set screw 30 is screwed into the mounting hole 13, and the pin 20 is attached to the pedestal 10. Fixed to. FIG. 1 shows the thread pulling prevention piece 1 completed by integrating the pedestal 10 and the pin 20.

[0029]

Embodiment 2 This embodiment corresponds to claims 1 and 3,
A stringing prevention piece 2 according to the present embodiment will be described with reference to FIG. This embodiment is basically the same as the configuration of the first embodiment. A feature is that a plurality of grooves 16 are formed on the outer periphery of the pedestal 10 in the thread pulling prevention piece 1 of FIG. 1, but in the thread pulling prevention piece 2 shown in FIG.
Are formed at equal intervals, and a gap between the inner wall of the nozzle formed by the projections 41 and the concave portion 42 on the outer periphery of the pedestal 40 forms a resin flow path. The depth of the concave portion 42 can be determined in consideration of the fluidity of the resin and the like. However, if the number of the protrusions 41 is two or more, preferably three or more,
Any number is acceptable. Pin 20 to pedestal 40 (pin body 21)
Is the same as that of the thread pulling prevention piece 1 described above.

[0030]

Embodiment 3 This embodiment corresponds to claims 1 and 4,
A stringing prevention piece 3 according to the present embodiment will be described with reference to FIG. In this embodiment, four spacer blades 32 are attached to the rear portion of the pin 31 at regular intervals, and the spacer blades 32
Is formed to be the same as the inner diameter of the nozzle flow path, and the space between the spacer blades 32 is used as a resin flow path.

[0031]

Embodiment 4 This embodiment corresponds to claims 5 and 6,
A method of performing injection molding using the thread pulling prevention piece completed as described above will be described with reference to FIGS. As the stringing prevention piece, the stringing prevention piece 1 described in the first embodiment was used. FIG. 6 shows the pedestal 10 in FIG.
FIG. 7 is a cross-sectional view of a position where the sprue bush 50 and the nozzle 60 are in contact with each other at the position of the cross-section A, and FIG.
FIG. 6 is a cross-sectional view of a position where the sprue bush 50 and the nozzle 60 are in contact with each other at the position of the BB cross section of the base 10 in FIG.

In this embodiment, the polystyrene resin (PS560 HB manufactured by PS Idemitsu Petrochemical Co., Ltd.) is used.
Injection molding machine (Model I manufactured by Toshiba Machine Co., Ltd.)
(S450EBW).

First, the string pulling prevention piece 1 is inserted into the nozzle 60 which is an open nozzle. When it is inserted, it is pushed into the direction of the tip of the nozzle 60, and furthermore, the insertion stops at a place where the diameter of the nozzle flow path 61 and the outer diameter of the pedestal 10 having the truncated cone shape of the stringing prevention piece 1 match. As described in the operation, the stringing prevention piece 1 is fixed in the nozzle flow channel 61 because back pressure is always applied to the bottom surface 11, so that there is no need for mechanical fixing. Will stagnate in position.

The length L of the tip of the pin body 21 protruding from the nozzle opening 62 is 2.5 mm in this embodiment.
It is desirable that the length L from which the tip of the pin protrudes is not limited to the above-mentioned dimension, but is set while checking the threading state.

After the nozzle 60 prepared as described above is attached to a heating cylinder (not shown), the fixed-side sprue bush 50 is brought into contact with the nozzle 60. The tip of the pin body 21 protruding from the nozzle opening 62
After entering the sprue flow path, preparation for injection molding is completed.
In a molding process by an injection molding machine, first, a mold is closed, and molten resin is injected into a cavity.

At the first portion of the stringing prevention piece in the nozzle 60, the molten resin passes through the groove 16 of the pedestal 10 shown in FIG. After 1.35 seconds, when the molten resin is completely filled, the molten resin is cooled while maintaining the pressure. However, the molten resin in the sprue bush channel 51 and the nozzle channel 61 in which the pin main body 21 is located is Since the pin main body 21 is located at the center of the area, the thickness of the pin body is thinner than the other parts, so that the temperature drop is increased. The holding pressure cooling time is 18 seconds.

After a predetermined cooling period has elapsed, the tightening force is released, the mold is opened, and the product is taken out. However, the resin temperature differs between the place where the pin 20 is inserted and the place where the pin 20 is not inserted. The portion that is hollow is thin and thin, so it hardens (cools) quickly, and when a detaching force is applied, the resin becomes difficult to expand, and as shown in FIG.
Only by the occurrence of 0, the sprue 80 was separated from the nozzle opening 62, and the so-called nasal dripping phenomenon did not occur. Thereafter, even though many injection moldings were performed, the stringing phenomenon did not occur.

[0038]

Comparative Example 1 Using the same resin material and injection molding machine as in the example, injection molding was performed without inserting a stringing prevention piece into the nozzle. As a result, a stringing phenomenon sometimes occurs, and every time the resin remaining in the nozzle opening has to be removed.

In particular, since the polystyrene resin used in the examples has good fluidity, it is difficult to perform injection molding with an open nozzle, and it cannot be handled without using an expensive dedicated nozzle or the suck-back method as described above.

As described above, by attaching the stringing prevention piece of the present invention to the open nozzle, the stringing can be prevented and the efficiency of injection molding can be improved. In addition, the stringing prevention piece according to claims 1 to 4 of the present invention uses a plurality of grooves and recesses provided on a base of the stringing prevention piece when a resin material of a plurality of colors is mixed and molded. The molten resin extruded from the heating cylinder is split, and when it passes through the pedestal, it reassembles and is injected into the sprue from the nozzle opening, so that the mixing of different color resin materials is further enhanced and evenly dispersed, The effect of eliminating the color unevenness of the molded product was recognized.

The grooves and recesses formed in the pedestal of the stringing prevention piece in the embodiment have a linear shape toward the top surface. The effect can be obtained.

[0042]

As described above, according to the present invention, when the resin is filled,
Inserting the tip of a pin into the sprue inlet, and installing a stringing prevention piece in the nozzle of the injection molding machine that speeds up cooling by thinning the resin into a hollow shape at the sprue inlet, causing a so-called nose drop Can be suppressed, and the following effects can be obtained.

1. Because of the simple structure, a stringing prevention piece can be manufactured at low cost. 2. Can be easily attached to conventional open nozzles. 3. Can reliably prevent nose drops caused by resin stringing,
Improve molding quality and automate molding. 4. Since it is structurally strong, it can be applied to injection molding using a composite resin material. 5. In the case of a different color resin mixed material, the mixing is further enhanced by the presence of the stringing prevention piece.

[Brief description of the drawings]

FIG. 1 is a side view of a stringing prevention piece of the present invention in a first embodiment.

FIG. 2 is a perspective view of a stringing prevention piece having another shape according to the second embodiment.

FIG. 3 is a perspective view of a stringing prevention piece having another shape.

FIG. 4 is a front view, a side view, and a rear view of a pedestal constituting the stringing prevention piece according to the first embodiment.

FIG. 5 is an assembly view of the stringing prevention piece according to the first embodiment.

FIG. 6 is a cross-sectional view of the nozzle and the sprue bush abutting portion taken along the line AA of the pedestal in FIG. 4C.

FIG. 7 is a cross-sectional view of the nozzle and the sprue bush abutting portion at the position of the BB cross section of the pedestal in FIG. 4C.

FIG. 8 shows the shape of a mustache formed on a sprue by a conventional injection molding method.

FIG. 9 is a sectional view of a beard formed on a sprue by injection molding using the stringing prevention piece of the present invention.

[Explanation of symbols]

 1, 2, 3 Stringing prevention piece 10 Pedestal 16 Groove 20 Pin 21 Pin body 40 Pedestal 50 Sprue bush 51 Sprue bush passage 60 Nozzle 61 Nozzle passage 62 Nozzle opening 70 Beard 80 Sprue

Claims (6)

[Claims] 1. A nozzle is formed by forming a resin flow path around the periphery, protruding a pin from the center of the tip, and filling the resin while partially inserting the pin into a sprue through a nozzle hole. Threading prevention piece for injection molding machine that prevents threading between the sprue and sprue. 2. The injection molding machine according to claim 1, wherein the outer peripheral surface of the pedestal main body is formed on the same inclined surface as the inclined surface of the flow passage in the nozzle, and the resin passage is formed on the inclined surface at equal intervals. Stringing prevention piece. 3. An outer peripheral surface of the pedestal main body is formed on the same inclined surface as the inclined surface of the flow path in the nozzle, and projections having the same inclination angle as the inclination of the flow path in the nozzle are formed at equal intervals on the outer peripheral surface of the pedestal. 2. A thread pulling prevention piece for an injection molding machine according to claim 1, wherein said resin flow paths are formed between said projections by being attached at equal intervals. 4. The resin inserted between the spacer blades is extended by extending the rear of the pin inserted into the nozzle hole and attaching spacer blades having the same inclination angle as the flow path in the nozzle at equal intervals on the extension side. 2. The thread pulling prevention piece for an injection molding machine according to claim 1, wherein the flow path is formed. 5. A resin is thinned by inserting a pin from the tip of the nozzle into the sprue inlet and forming the resin in the sprue inlet into a hollow shape by the action of the pin when filling the resin. An injection molding method which accelerates cooling and makes cutting easier, thereby preventing stringing. 6. A resin flow path is formed in the periphery, and a stringing prevention piece having a structure in which a pin protrudes from the tip is inserted into the nozzle flow path. By inserting the resin into the sprue side from inside the nozzle while the resin is partially inserted into the sprue inlet, the resin is formed hollow inside the sprue inlet to reduce the wall thickness, and the effect of cooling temperature is reduced. 6. The injection molding method according to claim 5, wherein the resin is easily received to accelerate the curing of the resin between the nozzle and the sprue, thereby preventing stringing.