JP2003266480A - Injection-molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection-molding method showing an excellent resin packing performance into a cavity, in the molding method for injecting a resin into the cavity equipped with a gas passage. <P>SOLUTION: A gas passage 83 whose one side communicates with the cavity 34 is formed at the movable half 33 of a mold. A suction means 86 is connected to the other side of the gas passage 83. A molten resin is packed into the cavity 34 through a sprue 41 and a runner 71. Prior to clamping the mold, a gas is sucked by a suction means 86 and the gas passage 83 is opened to the open air before packing the molten resin into the cavity 34. A negative pressure is generated near the cavity 34 and at the sprue 41 and the runner 71 by a suction operation. Further, because of the opening of the gas passage 83 before the packing of the molten resin, the gas in the cavity 34 is discharged from the gas passage 83 by the packing pressure of the molten resin, and consequently, the smooth packing of the molten resin is achieved even in the rapid packing mode. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an injection molding method using a molding material such as resin.

[0002]

SUMMARY OF THE INVENTION In a thermoplastic resin injection molding method, a molded product cavity is formed between a fixed mold and a movable mold which are clamped, and a thermoplastic resin as a molding material is placed in this molded product cavity. It is filled in a molten state, and after cooling and solidification, the mold is opened and the molded product is released from the mold.However, in the molded product having a thin portion, the space between the corresponding cavities is naturally thin and it is difficult to fill the resin. There is a problem.

Further, in the filling step of filling the resin, not only gas such as air exists in the cavity of the molded product, but also gas caused by the molten resin is generated. The gas generated from the molten resin and the air in the molded product cavity before filling are compressed by the molten resin and cause filling failure, but it is easy to cause filling failure because the gas is difficult to escape especially in the thin portion. There's a problem.

Therefore, there is known a method in which a gas passage is provided in the cavity, suction means is connected to the gas passage, and the inside of the cavity is kept at a negative pressure to improve the filling property of the resin in the cavity corresponding to the thin portion. However, in the molding of a molded article having a thin portion, the speed of the resin is higher than the suction speed of the suction means, so that degassing may be insufficient and defective filling may occur.

The present invention is intended to solve such a problem, and in a molding method for injecting a resin into a cavity having a gas passage, an injection molding method excellent in filling the resin into the cavity is provided. The purpose is to provide.

[0006]

The invention of claim 1 is an injection molding method in which suction is performed by the suction means before mold closing and the gas passage is opened to the atmosphere before the cavity is filled with the molding material. is there.

The fixed mold and the movable mold in the mold open state start the mold closing process, and the suction means sucks the gas passage before the mold closing is completed, so that the vicinity of the cavity and the material passage become negative pressure. Furthermore, since the gas passage is opened to the atmosphere before filling the molding material, the gas in the cavity is discharged from the gas passage due to the pressure of the molding material, and smooth filling can be performed even at high speed filling.

According to a second aspect of the present invention, in the first aspect of the present invention, a material supply device connected to the anti-cavity of the material passage is provided, and the suction is stopped almost at the same time when the material supply device starts the material supply. In addition, it is an injection molding method in which the other end of the gas passage is opened to the atmosphere.

Thus, the other side of the gas passage can be surely opened to the atmosphere before the molding material is filled into the cavity from the material supply device.

A third aspect of the present invention is an injection molding method in which the suction is performed substantially at the same time when the mold closing is started.

As a result, even if the mold closing step is carried out in a short time, the vicinity of the cavity before filling can be surely made to have a negative pressure.

[0012]

DETAILED DESCRIPTION OF THE INVENTION A first 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 inline screw type injection molding machine as shown in FIG. In FIG. 4, reference numeral 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 101 such as a computer.

Next, the structure of the die unit 31 will be described in detail with reference to FIGS. In FIGS. 1 to 3, the resin is shown by the thick line hatching. The fixed mold 32 and the movable mold 33, which are a pair of mold bodies, include the movable platen 23.
Are opened and closed by the movement of the molds, and a cavity 34 in the shape of a molded product is formed between them when the mold is closed. As shown in FIG. 7, the molded product P to be molded is provided with a frame portion 202 thicker than the plate-like portion 201 around the plate-like portion 201,
The thin portion 203 is provided at the center of the thin portion 1, and the thickness of the thin portion 203 is about 0.4 to 0.25 mm.

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. 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 material passage inside.
41, which penetrates the through hole 42 of the fixed mold body 37 and projects toward the movable mold 33. Then, the fixed body 37
Forms a cavity 34 when the mold is closed.

The movable die 33 includes a movable side attachment plate 61 attached to the movable side platen 23 and a movable die main body portion fixed to a surface of the movable side attachment plate 61 on the fixed die 32 side via a spacer block 62. With 63 and.

A concave portion 64 corresponding to the shape of the molded product P is formed on the surface of the movable mold main body 63 on the fixed mold 32 side, and this concave portion 64 is one side surface of the molded product P. The surface of the movable die 33 of 37 forms the other side surface of the molded product P.

A runner 71, which is a material passage for communicating the sprue 41 with the cavity 34, is formed between the closed fixed mold body 37 and the movable mold body 63, and the runner 71 is formed in the recess 64. Is in communication with.

Further, a projecting plate 76 is supported between the movable side mounting plate 61 and the movable mold body 63 so as to be movable in the mold opening / closing direction. This protruding plate 76 has a runner
Runner eject pin 77 that ejects the solidified resin in 71
And are fixed.

The movable mold 33 is provided with a nesting portion 81 corresponding to the thin portion 203 of the cavity 34,
A nest 82 made of a breathable mold material is provided in the nest mounting portion 81, one side of the gas passage 83 is provided in communication with the cavity 34 side of the nest 82, and the other side of the gas passage 83 is a movable body part. A connection screw portion 84 is formed on the outer periphery of 63 by a tap screw, and a switching valve using a solenoid or the like is connected to the connection screw portion 84, and a vacuum pump or the like is connected to one of the switching valves 85. The suction means 86 is connected and the other is opened to the atmosphere. The gas passage 83 is a movable main body.
It is formed inside 63, and one side communicates with the cavity 34 through the nest 82, and the other side communicates with the outside of the cavity 34.

The breathable mold material is, for example, low C, low N-.
Form a raw material whose main raw material is Cr-based stainless steel powder,
This compact is sintered in a vacuum or in an atmosphere gas, the obtained sintered body is machined if necessary, and then the sintered body is heated in a nitrogen atmosphere at a temperature range of 800 to 1100 ° C. A porous material or the like is used, which is nitrided by, and has fine continuous ventilation holes throughout. The block-shaped insert 82 made of such a breathable mold material has a cavity side surface.
Grooves 92 are formed on surfaces other than 91, and in this example, a plurality of grooves 92 are formed on the anti-cavity surface 93, the grooves 92 have a circular cross section, and the tip side forms a hemispherical surface 94. A thin portion 95 is formed between the side surface 91 and the cavity side surface 91. For example, the thickness of the insert 82 in the mold opening / closing direction is about 10 mm,
The diameter D of the groove portion 92 is about 4 to 6 mm, which is smaller than the thickness, the thickness S of the thin portion 95 is about 1.5 to 2.5 mm, and the minimum wall thickness of the wall 96 between the adjacent groove portions 92, 92. T is formed to be thinner than half the diameter D. Nest 82
The minimum wall thickness of the peripheral wall 96A is larger than the minimum wall thickness T. Further, the groove 92 and the hemispherical surface 94 are preferably formed by electric discharge machining, and by using electric discharge machining, it is possible to prevent clogging of the air-permeable mold material on the inner peripheral surface of the groove 92 and the hemispherical surface 94. .

Using the heating cylinder device 1, the mold clamping device 21, and the mold device 31 having the above-described configurations, the control device 101 such as a computer performs the following steps.

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 1 is melted and plasticized by heating by the heater 3 and kneading by rotation of the screw 6. With this plasticization, the resin is sent forward by the rotation of the screw 6 and is accumulated on the tip side in the cylinder body 1. Along with that, the screw 6 retracts due to the pressure of the resin. Even during the plasticizing step, the screw 6 is applied with an appropriate back pressure to the front by the hydraulic cylinder 11. When it is detected that the screw 6 has retracted to a predetermined position, the screw 6 is moved forward by driving the hydraulic cylinder 11, the resin on the tip end side in the cylinder body 1 is injected from the nozzle 4, and the sprue 41 of the mold device 31 is ejected. Is supplied to. In this case, the heating cylinder device 1 includes the screw 6
The drive start of the hydraulic cylinder 11 advancing is output to the control means 101 as an injection start (material supply start) signal. When it is detected that the screw 6 has advanced to the predetermined position, or when the screw 6 has advanced to the forward limit, the plasticizing step is started again.

The mold clamping device 21 closes the fixed mold 32 and the movable mold 32 under the control of the drive controller 27. When the mold closing step is started from the mold opening position, the drive control device 27 outputs a mold closing signal of this mold closing start to the control device 101, and the control device 101 starts suction by the suction means 86 by the mold closing signal. To do. After the mold closing process is started and before or after the mold closing process is completed, the heating cylinder device 1 starts injection and outputs a signal for starting the material supply to the control means 101, and the control means 101 causes the suction means to operate. The suction is stopped and the switching valve 85 is switched to open the other side of the gas passage 83 to the atmosphere. The mold closing means that the fixed mold 32 and the movable mold 33 come close to each other from the state where the cavity 34 is opened, and the mold closing is completed when the cavity 34 is fixed.
Shows the state of being blocked by.

On the other hand, when the injection is started, 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 71. In this case, the gas passage 83 communicating with the cavity 34 is closed by the suction means 86 before the mold is closed, and the cavity 34 is closed.
Since the vicinity, the runner 71 and the sprue 41 are kept at a negative pressure, the resin injected from the nozzle 4 of the heating cylinder device 1 smoothly flows through the sprue 41 and the runner 71, and the switching valve 85 switches at almost the same time as the injection. In order to open the other side of the gas passage 83 to the atmosphere, the gas in the cavity 34 is discharged through the nest 82 by the pressure of the injected resin, and the thin portion
203 is surely filled with resin.

Then, in the cavity 34, the resin undergoes a predetermined pressure-holding process, and after the resin is sufficiently cooled and solidified, the mold clamping device 21 opens the fixed mold 32 and the movable mold 33. Along with that, the resin in the cavity 34, that is, the molded product P and the resin solidified in the runner 71 and the sprue 41,
First, leave the fixed mold 32. Then, an unillustrated ejecting rod provided on the mold clamping device 21 side pushes the ejecting plate 76 toward the fixed mold 32, whereby the runner ejecting pin
77 ejects the resin solidified in the runner 71 and the sprue 41 to release it from the movable die 33, and the molded product ejecting pin ejects the molded product P to release it from the movable mold 33. Further, after the resin solidified in the runner 71 and the sprue 41 and the molded product P are taken out, the mold is closed again, and the switching valve 85 is switched to the one communicating with the suction means 86 before the mold closing is started. Therefore, the suction means 86 is driven at the same time as the mold closing signal, and the above steps are repeated.

As described above, in this embodiment, in accordance with claim 1, a fixed mold 32 and a movable mold 33, which are a plurality of mold bodies that open and close each other to form a cavity 34 between them when the molds are closed, and one of the molds. A fixed mold opened by using a mold device provided with a gas passage 83 provided on the movable die 33 as a die body and having one side communicating with the cavity 34, and a suction means 86 connected to the other side of the gas passage 83. In the injection molding method including a mold closing step of closing the mold 32 and the movable mold 33, and a filling step of filling the cavity 34 with the molten resin as the molding material through the sprue 41 as the material passage and the runner 71, suction is performed before the mold is closed. Suction is performed by the means 86, and the gas passage 83 is opened to the atmosphere before the cavity 34 is filled with the molten resin, so that the fixed mold 32 and the movable mold 33 start the mold closing process and before the mold closing is completed. Suction means 86
Sucks the gas passage 83, the negative pressure is generated in the vicinity of the cavity 34, the material passage sprue 41, and the runner 71,
Further, since the gas passage 83 is opened to the atmosphere before the molten resin is filled, the gas in the cavity 34 is discharged from the gas passage 83 by the filling pressure of the molten resin, and smooth filling can be performed even at high speed filling. Therefore, the molded product P having the thin portion 203 can be molded.

Further, as described above, in this embodiment, the anti-cavity of the sprue 41 serving as the material passage corresponds to claim 2.
The heating cylinder device 1 which is a material supply device connected to the heating cylinder device 1 is provided, and the suction is stopped and the other end of the gas passage 83 is opened to the atmosphere almost at the same time when the material supply of the heating cylinder device 1 is started. Therefore, the other side of the gas passage 83 can be surely opened to the atmosphere before the molten resin is filled in the cavity 34, whereby the molding cycle can be shortened.

As described above, according to the third aspect of the present invention, since the suction is performed almost at the same time when the mold closing is started, even if the mold closing step is performed in a short time, the vicinity of the cavity before the filling is closed. A negative pressure can be reliably achieved.

Further, as an effect of the embodiment, a fixed die 32 and a movable die 33, which are a plurality of die bodies that open and close each other to form a cavity 34 when the die are closed, and one movable die 33 that is the die body. A gas passage that is provided to remove gas from the cavity 34
83 and a nest 82 that is a breathable mold material that is provided in the cavity 34 and communicates with the gas passage 83, and in the molding die device that molds a molded product by filling the cavity 34 with resin, the nest 82 is Since the groove portion 92 communicating with the gas passage 83 is provided on the surface other than the cavity side surface 91 and the thin wall portion 95 is provided between the groove portion 92 and the cavity side surface 91, the fixed mold is used at the time of molding.
In the process of forming a cavity 34 inside by closing the mold 32 and the movable mold 33 and filling the cavity 34 with resin, the gas in the cavity 34 is exhausted from the gas passage 83 through the nest 82, especially the nest. In 82, the thin portion due to the groove 92
Since 95 is formed, it becomes excellent in breathability,
The resin is satisfactorily filled even in the thin portion of the cavity 34. Further, even if the resin enters the nest 82 and causes clogging, if the cavity side surface 91 of the nest 82 is cleaned and the clogging of the thin portion 95 is eliminated, the breathability can be secured again and the clogging can be prevented. It can be easily resolved.

8 to 9 show a second embodiment of the present invention, in which the same parts as those in the first embodiment are designated by the same reference numerals and detailed description thereof will be omitted. As described above, in the nest 82 of this example, the groove portion 92 is provided with a predetermined gap K.
To form a row, and the groove portions 92 of the adjacent row are provided with a plurality of rows of groove portions 92 with the interval K shifted by one half.
In addition to being excellent in air permeability, the occurrence of clogging can be suppressed, and even when clogging occurs, the air permeability can be secured by washing the thin portion 95.

10 to 12 show a third embodiment of the present invention, in which the same parts as those in the first embodiment are designated by the same reference numerals,
If you omit the detailed explanation and explain in detail, nesting of this example
In the groove 82A, the cross section of the groove 92A is formed in a long hole shape that is long in the direction crossing the mold opening / closing direction, and a semicircular surface 97 that is a curved surface is formed at the tip of the groove 92A. Also has excellent breathability, can suppress the occurrence of clogging, and even when clogging occurs, the thin-walled part
Breathability can be secured by washing 95.

The present invention is not limited to the above embodiment, and various modifications can be made. For example,
The material supply device is not limited to the one shown in the embodiment, and various types can be used. Further, in the embodiment, the one side of the gas passage is communicated with the cavity by the nest made of the air-permeable mold material, but the one side of the gas passage is communicated with the cavity by the gas vent hole or slit except for the cavity. You may do it.

[0034]

The invention according to claim 1 is an injection molding method in which suction is performed by the suction means before the mold is closed, and the gas passage is opened to the atmosphere before the molding material is filled in the cavity. The movable mold starts the mold closing process, and the suction means sucks the gas passage before the mold closing is completed, so that a negative pressure is generated in the vicinity of the cavity and the material passage, and before the molding material is filled. Since the gas passage is opened to the atmosphere, the gas in the cavity is discharged from the gas passage due to the pressure of the molding material, and smooth filling can be performed even at high speed filling.

In addition to the effect of the invention of claim 1, the invention of claim 2 further comprises a material supply device connected to the anti-cavity of the material passage, and substantially at the same time when the material supply of the material supply device is started, An injection molding method in which suction is stopped and the other end of the gas passage is opened to the atmosphere, and the other side of the gas passage is surely opened to the atmosphere before the molding material is filled into the cavity from the material supply device. You can

In addition to the effect of the invention of claim 1 or 3, the invention of claim 3 is an injection molding method in which the suction is performed almost at the same time when the mold closing is started, and the mold closing step is performed in a short time. Also, the vicinity of the cavity before filling can be surely made to have a negative pressure.

[Brief description of drawings]

FIG. 1 is a cross-sectional view around a cavity showing a first embodiment of the present invention.

FIG. 2 is a sectional view of the mold device in the mold closed state of the above.

FIG. 3 is a sectional view of the movable mold in the mold open state of the above.

FIG. 4 is a side view of the entire device, part of which is a dark surface.

FIG. 5 is a plan view of the nest of the same.

FIG. 6 is a sectional view of the nest of the same.

FIG. 7 is a perspective view of a molded product of the above.

FIG. 8 is a plan view of a nest showing a second embodiment of the present invention.

FIG. 9 is a sectional view taken along line AA of FIG.

FIG. 10 is a plan view of a nest showing a third embodiment of the present invention.

FIG. 11 is a sectional view taken along line BB of FIG.

FIG. 12 is a sectional view taken along line CC of FIG.

[Explanation of symbols]

1 Heating cylinder device (material supply device) 31 Mold equipment 32 fixed 33 movable 34 cavity 41 Spool (material passage) 71 Runner (material passage) 83 gas passage 101 control means P molded products

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4F202 AM32 CA11 CB01 CK06 CK11                       CP01 CP06                 4F206 AM32 JA07 JL02 JM02 JM04                       JN26 JQ03 JQ81

Claims (3)

[Claims] 1. A plurality of mold bodies that open and close each other to form cavities between them when the molds are closed, a gas passage provided in one of the mold bodies and one side of which communicates with the cavity, and another side of the gas passage. Injection including a mold closing step of closing a plurality of mold bodies that have been opened using a mold device provided with a suction means connected thereto, and a filling step of filling a molding material through the cavity into the cavity. In the molding method, suction is performed by the suction means before the mold is closed, and the gas passage is opened to the atmosphere before the cavity is filled with the molding material. 2. A material supply device connected to an anti-cavity of the material passage, wherein the suction is stopped and the other end of the gas passage is opened to the atmosphere almost at the same time when the material supply of the material supply device is started. The injection molding method according to claim 1, wherein: 3. The injection molding method according to claim 1, wherein the suction is performed almost at the same time when the mold closing is started.