JPH1024461A - Injection molding method and injection mold apparatus used therein - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the waste of a molding material in injection molding performing in-mold weighing, to shorten a molding cycle and to reduce restrictions to a product shape or a gate position. SOLUTION: A mold apparatus changed in the vol. of a cavity accompanied by the opening and closing of a fixed mold 1 and a movable mold 2 is used. A spring 42 applies force in the direction opening the fixed mold 1 and the movable mold 2. Mold clamping is performed by relatively weak mold clamping force and, in such a state that the fixed mold 1 and the movable mold 2 are not perfectly closed, the cavity 3 is filled with a resin being a molding material. Thereafter, mold clamping force is increased to finally close the fixed mold 1 and the movable mold 2 but, during this period, a gate 21 is closed by a valve device 22. Until the gate 21 is closed, the resin in the cavity 3 returns to a passage 24. After the gate 21 is closed, the resin in the cavity 3 is compressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method called high-pressure injection molding (in-mold measurement compression molding) and an injection molding die apparatus used in this method.

[0002]

2. Description of the Related Art In so-called high-pressure injection molding, which has recently been adopted, first, a molding material such as a thermoplastic resin is filled in a cavity while a fixed mold and a movable mold are closed with a weak mold clamping force. After that, the mold clamping force is strengthened to finally close the fixed mold and the movable mold, and during this final mold closure, the resin is returned from the cavity through the gate to the molding material supply device such as a cylinder device. After that, the gate is closed, and thereafter the resin in the cavity is compressed.
Thereby, the weighing is performed in the mold.

In the conventional high-pressure injection molding, for example, a movable plate is supported on a fixed die so as to be movable in the opening and closing directions of the fixed die and the movable die, and the movable plate is attached to the movable die relative to the fixed die. The mold device is used. Then, a runner communicating with the fixed type sprue is formed between the moving plate and the movable mold, while a cavity is formed between the fixed mold and the movable mold, and the convex portion provided on the fixed mold is formed in the movable mold. The gate from the runner to the cavity is closed by fitting into the concave portion provided in the cavity.

In molding, resin is injected from an injection molding machine to a sprue with the movable plate and the movable die closed while the fixed die and the movable plate are slightly opened. This resin is filled into the cavity through the runner and the gate (filling step). In the subsequent final mold clamping step, the mold clamping force is increased, and the fixed mold and the movable mold are closed. At this time, excess resin in the cavity returns from the gate to the runner side. Then, the gate is closed in the middle of the final mold clamping step, but thereafter, the resin in the cavity is compressed. Then, after the resin in the cavity, runner and sprue is cooled and solidified, the mold is opened, and the resin solidified in the cavity, that is, the product and the resin solidified in the runner and sprue are taken out.

[0005]

However, in the conventional high-pressure injection molding, the resin in the sprue and the runner, which is a material passage, is also solidified, so that there is a problem that the molding material is wasted. Also, unlike the resin in the cavity, the resin in the runner is not compressed, and no pressure is applied, so that cooling and solidification are delayed. Therefore, while the resin in the cavity to be compressed solidifies quickly, there is a problem that the molding cycle is restricted by the solidification of the resin in the runner, and the productivity is deteriorated. In order to increase the pressure of the resin in the runner due to the reflux of the resin in the cavity, at least a part of a material passage such as a sprue or a runner may be narrowed, but this takes a long time for filling.

On the other hand, high pressure injection molding using a hot runner type mold apparatus has also been proposed. in this case,
Since it is necessary to keep the gate closed even when the mold is open, the fixed mold requires gate opening / closing means such as a valve for opening and closing the gate provided in the fixed mold. But,
In the conventionally proposed high-pressure injection molding, when closing the gate in the final mold clamping process, for example, the convex portion provided on the movable die is fitted to the fixed die gate, so that the product shape and gate position that can be molded Had the problem of being restricted.

An object of the present invention is to solve such a problem and to reduce waste of molding material and shorten the molding cycle in high-pressure injection molding. Another object of the present invention is to reduce restrictions on a product shape and a gate position.

[0008]

According to a first aspect of the present invention, in order to achieve the above objects, a gate formed between a molding material supply device and a material passage and a cavity is provided in a cavity formed between molds that open and close to each other. A filling step of filling a thermoplastic molding material through the mold, and a final clamping step of finally closing the mold bodies together after the completion of the filling step. After returning the molding material to the material passage side, in the injection molding method of closing the gate and thereafter compressing the molding material in the cavity, the molding material in the material passage is always kept in a molten state by heating, Before the gate is finally closed, the gate is closed by gate opening / closing means that operates independently of opening and closing of these molds.

In the final mold clamping step, the molding material in the cavity returns to the material passage side through the gate, so that the in-mold measurement is performed. After the gate is closed, the molding material in the cavity is compressed. Is done. This compression also compensates for the shrinkage of the molding material in the cavity due to cooling.
The opening and closing of the gate is performed by gate opening and closing means that operates independently of the opening and closing of the mold. Therefore, the opening and closing of the gate does not restrict the product shape and the gate position. Further, the molding material in the material passage is always kept in a molten state by heating, so that the molding material is not wasted, and the molding material in the cavity smoothly returns to the material passage side during the in-mold measurement.

According to a second aspect of the present invention, there is provided an injection molding die apparatus used in the injection molding method according to the first aspect of the present invention, wherein the first mold body is opened and closed with each other to form a cavity therebetween when the mold is closed. And a second mold, wherein the volume of the cavity is made variable according to the opening and closing operations of the two molds, and the first mold has a material passage located inside the first mold;
A gate for opening the material passage to the cavity;
A heating means for always keeping the molding material in the material passage in a molten state, and a gate opening / closing means for operating the gate independently to open and close the gate are provided.

In the final mold clamping step, the volume of the cavity is reduced as the two molds are closed, so that the molding material in the cavity returns to the material passage, and the gate opening / closing means is provided. After closing the gate,
The molding material in the cavity is compressed.

According to a third aspect of the present invention, in order to achieve the first object, a thermoplastic molding is carried out by passing a gate from a molding material supply device to a material passage and a cavity into a cavity formed between molds that open and close to each other. A filling step of filling the material; and a final clamping step of finally closing the mold bodies after completion of the filling step. During the final clamping step, molding is performed from the cavity to the material passage side through the gate through the gate. After the material is returned, the gate is closed and the molding material in the cavity is then compressed, and one of these molds is closed between the molds which close before the filling process and do not move during the final clamping process. In an injection molding method for forming a subsequent material passage communicating with a preceding material passage in a body via an injection port, a gate from the latter material passage to the cavity is used in a final mold clamping step. Closed by the operation of the mold, the molding material in the former material passage is always kept in a molten state by heating, and before the gate is closed, the injection port is opened and closed by the injection port opening / closing means which operates independently of opening and closing of the mold. Close.

Then, in the final mold clamping step, first,
The molding material in the cavity returns through the gate into the downstream material passage, and the molding material in the downstream material passage returns through the inlet into the preceding material passage. Thereafter, the inlet is closed by an inlet opening / closing means that operates independently of opening and closing of the mold,
The molding material in the downstream material passage will not return to the upstream material passage. Therefore, when the molding material is recirculated from the cavity, the pressure of the molding material in the subsequent material passage increases, and thereby the solidification of the molding material in the subsequent material passage is accelerated. In this way, the molding material in the cavity is returned to the material passage, whereby the in-mold measurement is performed.
After the inlet is closed and the gate is closed, the molding material in the cavity is compressed. This compression also compensates for the shrinkage of the molding material in the cavity due to cooling. Also, the molding material in the former material passage is always kept in a molten state by heating, and the waste of the molding material is reduced.
At the time of the in-mold measurement, the reflux of the molding material is smoothly performed.

According to a fourth aspect of the present invention, there is provided an injection molding die apparatus used in the injection molding method according to the third aspect of the present invention, wherein the first and second molds are opened and closed with each other to form a cavity therebetween when the mold is closed. And a second mold, a movable body that is movably supported by one of the molds in the opening and closing direction of the two molds, and forms a subsequent material passage between the other mold and a movable body. Biasing means for biasing the one mold toward the other mold, while varying the volume of the cavity with the opening and closing operations of the two molds, from the post-stage material passage Opening and closing a gate to the cavity, the first mold body, a pre-stage material passage located inside the first mold body, an injection port for opening the pre-stage material passage to the post-stage material passage, Heating means for always keeping the molding material in the material passage in a molten state; The opening and closing of the is provided with a an inlet closing means for opening and closing the inlet actuated independently.

In molding, the movable body is closed with respect to the other mold body, and the movable body and one mold body are slightly opened, and the former material passage, the inlet, and the movable body in the first mold body are moved. The molding material is filled into the cavity through a subsequent material passage and a gate formed between the body and the other mold body (filling step). In the subsequent final mold clamping step, the moving body and one of the mold bodies are closed, but the volume of the cavity is reduced accordingly, so that the molding material in the cavity returns to the subsequent material passage, and The molding material in the second material passage returns to the first material passage, and after the gate is closed, the molding material in the cavity is compressed.
Before the gate is closed, the inlet is closed by the inlet opening / closing means.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. First, the configuration of the injection molding die apparatus will be described. Reference numeral 1 denotes a fixed mold serving as a first mold, and 2 denotes a movable mold serving as a second mold. The fixed mold 1 and the movable mold 2 move up and down (in the mold opening and closing direction) to open and close with each other. A plurality of product-shaped cavities 3 are formed between each other when the mold is closed.

The fixed mold 1 has a fixed mold plate 6 having a concave portion 5 for forming the cavity 3 and a fixed receiving plate 7 fixed to the back side of the fixed mold plate 6 (opposite to the movable mold 2).
And a spacer block 8 on the back side of the fixed receiving plate 7.
And a fixed-side mounting plate 9 which is fixed through the base plate. The fixed side mounting plate 9 is mounted on a fixed side platen (not shown) of the injection molding machine. And
A fixed ring 9 and a sprue bush 13 to which a nozzle 12 of a heating cylinder device which is a molding material supply device of an injection molding machine is connected are fixed to the fixed side mounting plate 9. The inside of the sprue bush 13 is a sprue 14 which is a material passage. Also, a sprue bush
13 is provided with a heater 15 which is a heating means for heating the sprue 14 and always keeping the thermoplastic resin as a molding material in the sprue 14 in a molten state. In addition, a manifold 16 is provided between the fixed-side receiving plate 7 and the fixed-side mounting plate 8. Inside the manifold 16, a runner 17 is formed as a material passage for branching the sprue 14 into each cavity 3. Also manifold
The heater 16 is a heating means for heating the runner 17 to keep the thermoplastic resin in the runner 17 in a molten state at all times.

The fixed type 1 has a direct gate 21.
A valve device 22 is provided as a gate opening / closing means for opening / closing the gate. The valve device 22 includes a cylindrical valve casing 23 embedded and fixed in the fixed-side mold plate 6 and the fixed-side receiving plate 7, and the valve casing 23 also abuts against the manifold 16. The inside of the valve casing 23 is a flow passage 24 which is a material passage, and one end of the flow passage 24 communicates with the final branch of the runner 17 of the manifold 16. The other end of the flow passage 24 opens to the cavity 3 through the gate 21 formed in the fixed mold plate 6. Further, the valve casing 23 has a heater 25 as a heating means for heating the flow passage 24 and keeping the thermoplastic resin therein in a molten state at all times.
Is provided. Further, a valve pin 26 that fits in the gate 21 so as to be freely inserted and removed and closes the gate 21 is supported in the valve casing 23. This valve pin 26
Is driven by a driving device 27 such as a hydraulic cylinder provided on the fixed-side mounting plate 9 and moves in the mold opening / closing direction. That is, opening and closing of the gate 21 is performed independently of opening and closing operations of the fixed mold 1 and the movable mold 2.

The movable mold 2 includes a movable mold plate 31, a movable receiving plate 32 fixed to the back side of the movable mold plate 31 (the side opposite to the fixed mold 1), and a movable receiving plate 32. A movable-side mounting plate (not shown) fixed to the back side. This movable side mounting plate is mounted on a movable side platen (not shown) of the injection molding machine. A core 33 sandwiched and fixed between the movable mold plate 31 and the movable receiving plate 32 protrudes toward the fixed mold 1. This core 33
Is to form the cavity 3 by slidably fitting in the concave portion 5 of the fixed mold plate 6. The side surfaces of the core 33 and the concave portion 5 are parallel to the mold opening / closing direction, so that the cavity 3 is maintained in a closed state while maintaining the hermetically sealed state.
In addition, the volume changes with the opening and closing operation of the movable mold 2. That is, as the fixed mold 1 and the movable mold 2 close, the volume of the cavity 3 becomes smaller. In addition, in the movable mold 2,
Product push-out pins 34 are also provided.

The movable mold plate 31 includes the movable mold plate 31.
A movable plate 41 as a movable body that opens and closes with respect to the fixed mold plate 6 and the fixed mold plate 6 is movably supported in the mold opening and closing direction. The movable plate 41 is urged toward the fixed mold 1 with respect to the movable mold plate 31 by a spring 42 as urging means. In addition,
The core 33 slidably penetrates the movable plate 41.

Next, an injection molding method using the mold apparatus will be described. The mold clamping device of the injection molding machine first closes the fixed mold 1 and the movable mold 2 with a relatively weak fixed clamping force. At this time, as shown in FIG.
41 and the fixed mold 1 abut and close. On the other hand, the movable mold 2
The movable side mold plate 31 and the movable plate 41 are opened with a predetermined opening amount A1. That is, the mold clamping force and the force of the spring 42 are balanced. Also, the movable mold 2 is provided in the recess 5 of the fixed mold 1.
The core 3 is fitted to form the cavity 3. In this state, pull out the valve pin 26 from the gate 21 and
At the same time, the molten thermoplastic resin is injected into the sprue 14 from the nozzle of the heating cylinder device. This resin is filled into the cavity 3 from the sprue 14 through the runner 17, the flow passage 24 and the gate 21 (filling step).

In the filling step, the movable mold 2 is retracted by the pressure of the resin, and the movable mold plate 31 and the movable plate 41 are moved.
May be opened. As a result, the error in the amount of resin injected from the injection molding machine is absorbed, and the pressure of the resin in the cavity 3 is kept substantially constant by the balance between the force of the spring 42 and the mold clamping force. On the other hand, if there are problems such as the opening between the movable plate 41 and the fixed mold plate 6 or the retreat of the movable mold 2 continuing and the entire cavity 3 is not filled with the resin due to the conditions such as the product shape, By making the mold clamping force large enough to withstand the pressure of the resin in the mold apparatus, the movable mold 2 does not recede during the filling process, and the opening amount A1 between the movable mold plate 31 and the movable plate 41 is reduced. May be kept constant.

After the completion of the filling step, the mold clamping device increases the clamping force, and the fixed mold 1 and the movable mold 2 are finally closed (final mold clamping step). In the final mold clamping step, the fixed mold 1 and the movable plate 41 and the movable mold 2 are closed. Accordingly, the excess resin in the cavity 3 is removed from the gate 21 which is still open.
From the flow path 24, the resin in the mold apparatus returns to the heating cylinder apparatus. Then, as shown in FIG. 2, when the opening amount between the movable mold plate 31 and the movable plate 41 reaches a predetermined amount A2, the valve pin 26 moves and fits into the gate 21, and this gate 21
Closes. At this point, a certain amount of resin remains in the cavity 3 and the in-mold measurement has been performed (a measurement step). Thereafter, as the fixed mold 1 and the movable plate 41 and the movable mold 2 close, the resin in the cavity 3 is compressed (compression step). FIG. 3 shows a state where the fixed die 1 and the movable plate 41 and the movable die 2 are finally closed. The compression step increases the density of the product and compensates for shrinkage due to solidification due to cooling of the resin. Therefore, it is not necessary to perform the pressure holding step on the heating cylinder device side for this compensation.

After the resin in the cavity 3 is sufficiently cooled and solidified, the fixed mold 1 and the movable mold 2 are
Is opened. Accordingly, the resin in the cavity 3, that is, the product, first separates from the fixed mold 1. Next, the product ejection pin 34 projects the product and releases the product from the movable mold 2. Further, after the product is taken out, the mold is closed again, and the above steps are repeated. Throughout the entire process, the resin in the sprue 14, the runner 17 and the flow passage 24 is always kept in a molten state by heating the heaters 15, 18 and 25.

As described above, according to the structure of the first embodiment, the movable mold plate is used in the final mold clamping process after the filling process.
The in-mold measurement is performed by refluxing the resin in the cavity 3 until the opening amount between the moving plate 41 and the moving plate 41 reaches the predetermined amount A2 and the gate 21 closes, so that the amount of resin charged in the cavity 3 can be accurately determined. In combination with the subsequent compression step of compressing the resin in the cavity 3, it is possible to mold a high-precision product with stable quality.

In the mold apparatus, the cavity 3
Since the resin in the sprue 14, the runner 17 and the flow path 24 other than those in the flow path 24 are always kept in a molten state by heating, there is no waste of the resin. It returns smoothly to the side, and the in-mold measurement can be performed well.

Further, as described above, the compression step performed on the mold apparatus side eliminates the need for performing the pressure holding step on the injection molding machine side, so that the molding cycle can be greatly shortened.
Of course, the fact that the resin in the sprue 14, the runner 17 and the flow passage 24 of the fixed mold 1 is always kept in a molten state means that these and the cavity 3 are provided in the valve apparatus provided in the fixed mold 1.
Because it is blocked by 22, it does not become a factor to lengthen the molding cycle.

Further, since the gate 21 is opened and closed by the valve device 22 which operates independently of the opening and closing of the fixed mold 1 and the movable mold 2, the product shape and the position of the gate 21 are changed to open and close the gate. You will not be restricted. Therefore, high-pressure injection molding can be applied to products of various shapes, and the position of the gate 21 can be freely set so that good molding can be performed in terms of mold design.

Next, a second embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. First, the configuration of the injection molding die apparatus will be described. Reference numeral 51 denotes a fixed mold as a first mold, and 52 denotes a movable mold as a second mold.
The movable mold 52 moves up and down in the figure (mold opening and closing direction) to open and close with each other, and forms a plurality of product-shaped cavities 53 therebetween when the mold is closed.

The fixed mold 51 includes a fixed mold plate 56 having a concave portion 55 forming a cavity 53, and a fixed-side receiving plate 57 fixed to the back side (opposite to the movable mold 52) of the fixed mold plate 56.
And a spacer block 58 on the back side of the fixed side receiving plate 57.
And a fixed-side mounting plate 59 that is fixed through the fixing member. The fixed side mounting plate 59 is mounted on a fixed side platen (not shown) of the injection molding machine. And
A locating ring 61 and a sprue bush 63 to which a nozzle 62 of a heating cylinder device which is a molding material supply device of an injection molding machine is connected are fixed to the fixed side mounting plate 59. The inside of the sprue bush 63 is a sprue 64 which is a material passage in the preceding stage. Further, the sprue bush 63 is provided with a heater 65 as heating means for heating the sprue 64 to keep the thermoplastic resin as a molding material in the sprue 64 in a molten state at all times. Also, fixed-side receiving plate 57
A manifold 66 is provided between the fixed side mounting plate 58 and the fixed side mounting plate 58. Inside the manifold 66, a runner 67, which is a former material passage for branching the sprue 64 into each cavity 53, is formed. Further, the manifold 66 is provided with a heater 68 as heating means for heating the runner 67 to keep the thermoplastic resin in the runner 67 in a molten state at all times.

Further, the fixed mold 51 is provided with a valve device 72 as an inlet opening / closing means for opening / closing the inlet 71.
The valve device 72 includes a fixed mold plate 56 and a fixed receiving plate.
Tubular valve casing 73 embedded and fixed in 57
The valve casing 73 has a manifold
It also hits 66. And the valve casing
The inside of 73 is a flow passage 74 which is a preceding material passage,
One end of the flow passage 74 communicates with the last branch of the runner 67 of the manifold 66. The other end of the flow passage 74 communicates with the inlet 71 formed in the fixed mold plate 56. Further, the valve casing 73 is provided with a heater 75 as heating means for heating the flow passage 74 and keeping the thermoplastic resin in the flow passage 74 in a molten state at all times. Further, in the valve casing 73, a valve pin 76 that is fitted to the inlet 71 so as to be freely inserted and removed and closes the inlet 71 is supported. The valve pin 76 penetrates the manifold 66, and is driven by a driving device 77 such as a hydraulic cylinder provided on the fixed-side mounting plate 59 to move in the mold opening / closing direction. That is, opening and closing of the injection port 71 is performed independently of opening and closing operations of the fixed mold 51 and the movable mold 52.

The movable mold 52 includes a movable mold plate 81, a movable receiving plate 82 fixed to the back side of the movable mold plate 81 (the side opposite to the fixed mold 51), and a movable receiving plate 82. A movable-side mounting plate (not shown) fixed to the back side. This movable side mounting plate is mounted on a movable side platen (not shown) of the injection molding machine. A core 83 sandwiched and fixed between the movable mold plate 81 and the movable receiving plate 82 protrudes toward the fixed mold 51. This core 83
Are slidably fitted in the concave portions 55 of the fixed mold plate 56 to form the cavities 53. The movable mold 52 is also provided with a product protrusion pin 84 and a sub-runner protrusion pin 85.

The movable mold plate 81 includes the movable mold plate 81.
A moving plate 91 as a moving body, which is another type body that opens and closes with respect to the 81 and the fixed side mold plate 56, is movably supported in the mold opening and closing direction. The moving plate 91 is provided with a spring as an urging means.
92 urges the movable mold plate 81 toward the fixed mold 51. The core 83 slidably penetrates a through hole 93 formed in the moving plate 91. In a filling step to be described later, the cavity 53 is formed by the side surface of the through hole 93 of the moving plate 91.
83, the side surfaces of the through hole 93 and the concave portion 55 are parallel to the mold opening / closing direction, so that the volume of the cavity 53 changes with the opening / closing operation of the fixed mold 51 and the movable mold 52 while maintaining the sealed state. I do. That is, as the fixed mold 51 and the movable mold 52 close, the volume of the cavity 53 decreases.
Further, between the closed moving plate 91 and the fixed mold plate 56, a sub-runner 96 which is a subsequent material passage in which the injection port 71 of the fixed mold plate 56 is opened, and the sub-runner 96 and the cavity 53 A side gate 97 having an opening is formed. The gate 97 is opened and closed by the side surface of the core 83 as the fixed mold 51 and the movable mold 52 open and close.

Next, an injection molding method using the mold apparatus will be described. The mold clamping device of the injection molding machine first closes the fixed mold 51 and the movable mold 52 with a relatively weak fixed clamping force. At this time, as shown in FIG.
91 and the fixed mold 51 abut and close. On the other hand, movable mold 52
The movable side mold plate 81 and the movable plate 91 are opened with a predetermined opening amount B1. That is, the mold clamping force and the force of the spring 92 are balanced. Then, a sub-runner 96 and a gate 97 are formed between the closed movable plate 91 and the fixed die 51, and the concave portion 55 of the fixed die 51, the core 83 of the movable die 52, and the movable plate 91.
A cavity 53 is formed therebetween. However, the core 83 has not yet been fitted into the recess 55, and the gate 97 is open.
In this state, the valve pin 76 is pulled out from the injection port 71, and the injection port 71 is opened, and the molten thermoplastic resin is injected from the nozzle of the heating cylinder device to the sprue 64. This resin flows from the sprue 64 to the runner 67,
4. The cavity 53 is filled through the inlet 71, the sub-runner 96 and the gate 97 (filling step).

In the filling step, the movable mold 52 is retracted by the pressure of the resin, and the movable mold plate 81 and the movable plate 91
May be opened. As a result, errors in the amount of resin injected from the injection molding machine are absorbed, and the balance between the force of the spring 92 and the mold clamping force allows the cavity to be removed.
The pressure of the resin in 53 is kept almost constant. On the other hand, from the conditions such as the product shape, if there is a problem such as opening between the movable plate 91 and the fixed-side mold plate 56, or if the entire cavity 53 is not filled with resin following the retreat of the movable mold 52, By making the mold clamping force large enough to withstand the pressure of the resin in the mold apparatus, the movable mold 52 does not recede during the filling process, and the opening amount B1 between the movable mold plate 81 and the movable plate 91 is increased. May be kept constant.

After the filling step is completed, the mold clamping device increases the clamping force, and the fixed mold 51 and the movable mold 52 are finally closed (final mold clamping step). In the final mold clamping step, the fixed mold 51, the movable plate 91, and the movable mold 52 are closed. Along with that, the extra resin in the cavity 53
From the sub-runner 96, the resin in the sub-runner 96 returns to the flow passage 24 from the still open inlet 71, and the resin in the mold apparatus returns to the heating cylinder apparatus.

Then, as shown in FIG.
When the opening amount between the moving plate 91 and the moving plate 91 decreases to a predetermined amount B2, the valve pin 76 moves and fits into the inlet 71, and the inlet 71
Closes. At this point, gate 97 is still open. Therefore, as the movable mold plate 81 and the movable plate 91 close, the resin in the cavity 53 returns from the gate 97 into the sub-runner 96, but the resin in the sub-runner 96 returns to the flow passage 24 side. Since there is no resin, the pressure of the resin in the sub-runner 96 increases. As a result, the subsequent solidification of the resin in the sub-runner 96 is accelerated.

Thereafter, as shown by a chain line in FIG. 6, when the opening amount between the movable mold plate 81 and the movable plate 91 is further reduced to a predetermined amount B3, the movable mold fitted into the concave portion 55 of the fixed mold plate 56. Type 52
The gate 97 is closed by the core 83. At this point, a certain amount of resin remains in the cavity 53, and the in-mold measurement has been performed (measuring step). Thereafter, as the fixed mold 51 and the movable plate 91 and the movable mold 52 close, the cavity
The resin in 53 is compressed (compression step). The state in which the fixed mold 51 and the movable plate 91 and the movable mold 52 are finally closed is shown by a solid line in FIG. The compression step increases the density of the product and compensates for shrinkage due to solidification due to cooling of the resin. Therefore, it is not necessary to perform the pressure holding step on the heating cylinder device side for this compensation.

Then, the cavity 53 and the sub-runner
After the resin in 96 is sufficiently cooled and solidified, the fixed mold 51 and the movable mold 52 are opened by the mold clamping device. Accordingly, the resin in the cavity 53, that is, the product and the resin solidified in the sub-runner 96 are separated from the fixed mold 51 first. Then
The product projecting pin 84 projects the product and releases it from the movable mold 52, and the sub-runner projecting pin 85 releases the resin solidified in the sub-runner 96 from the movable mold 52. Further, after the product and the resin solidified in the sub-runner 96 are taken out, the mold is closed again, and the above steps are repeated. Throughout the process, sprue 64, runner
The resin in the passage 67 and the flow passage 74 is always kept in a molten state by the heating of the heaters 65, 68, 75.

As described above, according to the configuration of the second embodiment, the movable mold plate is used in the final mold clamping process after the filling process.
In-mold measurement is performed by refluxing the resin in the cavity 53 until the opening amount between the moving plate 91 and the moving plate 91 reaches the predetermined amount B3 and the gate 97 closes, so that the amount of the resin filled in the cavity 53 can be accurately determined. In combination with the subsequent compression step of compressing the resin in the cavity 53, a high quality product with stable quality can be formed.

In the mold apparatus, the cavity 53
The resin in the sprue 64, the runner 67, and the flow passage 74 other than the sub-runner 96 is always kept in a molten state by heating, so that the resin is less wasted and the resin in the cavity 56 is It returns smoothly to the flow path 74 side via the runner 96, and the in-mold measurement can be performed satisfactorily.

Further, in the final mold clamping step, since the injection port 71 is closed before the gate 97 is closed, the pressure of the resin in the sub-runner 96 increases due to the reflux of the resin from the cavity 53, and the subsequent sub-runner 96 is closed. The resin in 96 can be quickly solidified. Of course, the resin in the cavity 53 that is compressed due to the mold clamping solidifies quickly. Therefore, as described above, the compression step performed on the mold apparatus side eliminates the need to perform the pressure-holding step on the injection molding machine side, and can greatly shorten the molding cycle.

Needless to say, unlike the case where the pressure of the resin in the sub-runner is increased by circulating the resin from the cavity by narrowing the material passage itself, the filling step does not take much time and the resin from the cavity is not filled. The required reflux is not hindered.

It should be noted that the present invention is not limited to the above embodiment, and various modifications can be made. For example,
In the above embodiment, the moving body (moving plates 41 and 91) is
Although provided on the 52 side, it may be provided on the fixed type side. In the above embodiment, injection molding of a thermoplastic resin has been described as an example. However, the present invention is not limited to injection molding of various molding materials, such as injection molding of ceramics using a thermoplastic resin as a binder and injection molding powder metallurgy. Applicable to molding.

[0045]

According to the first aspect of the present invention, the final mold clamping step is performed after the filling step, and the molding material in the cavity is compressed after the in-mold measurement is performed during the final mold clamping step. In the injection molding method, since the molding material in the material passage is always kept in a molten state by heating, it is possible to eliminate the waste of the molding material and to smoothly return the molding material in the cavity to the material passage at the time of in-mold measurement. . Further, since the gate opening / closing means that operates independently of the opening / closing of the mold is used to close the gate during the final mold clamping step, restrictions on the product shape and the gate position can be reduced. Further, the molding cycle does not become long because of waiting for the molding material to solidify in the material passage.

According to the injection molding die apparatus of the second aspect of the present invention, the volume of the cavity is made variable in accordance with the opening and closing operations of the first and second mold bodies, and the first mold body has: 2. The injection molding method according to claim 1, further comprising a material passage, a gate, a heating means for heating the material passage, and a gate opening / closing means for opening / closing the gate by operating independently of opening / closing of the two molds. And the effect can be obtained.

According to the third aspect of the present invention, after the filling step, the final mold clamping step is performed. During the final mold clamping step, after the in-mold measurement is performed, the molding material in the cavity is compressed. An injection molding method for forming, between molds that are closed before the filling step and do not move at the time of the final mold clamping step, a later-stage material passage that communicates with an earlier-stage material passage in one of these molds through an injection port. Since the molding material in the former material passage is always kept in a molten state by heating, the waste of the molding material can be reduced, and the molding material in the cavity can be smoothly returned to the material passage at the time of in-mold measurement. Also, since the injection port is closed before the gate closes during the final mold clamping process,
By increasing the pressure of the molding material in the downstream material passage due to the reflux of the molding material from within the cavity, the subsequent solidification of the molding material in the downstream material passage is accelerated, and therefore the molding cycle can be shortened.

According to the mold apparatus for injection molding of the fourth aspect of the present invention, the first mold and the second mold which form the cavity, and the other of the first mold and the second mold which are movably supported by one of the molds. And a biasing means for biasing the movable body toward the other mold body. In addition to making the volume variable, opening and closing the gate from the post-stage material passage to the cavity, the first mold body includes a pre-stage material passage, an inlet, a heating means for heating the pre-stage material passage, and an inlet. Since the injection port opening / closing means for opening / closing is provided, the effect can be obtained by implementing the injection molding method according to the third aspect of the present invention.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of an injection molding die apparatus of the present invention, showing a filling step.

FIG. 2 is a sectional view at the start of a compression step in the latter half of the last mold clamping step.

FIG. 3 is a sectional view at the end of the compression step.

FIG. 4 is a cross-sectional view showing a second embodiment of the injection molding die apparatus of the present invention, showing a filling step.

FIG. 5 is a cross-sectional view when the injection port is closed in the same final mold clamping step.

FIG. 6 is a cross-sectional view at the end of the compression step.

[Explanation of symbols]

 Reference Signs List 1 fixed mold (first mold) 2 movable mold (second mold) 3 cavity 14 sprue (material passage) 15 heater (heating means) 17 runner (material passage) 18 heater (heating means) 21 gate 22 valve Device (gate opening / closing means) 24 Flow passage (material passage) 25 Heater (heating means) 51 Fixed mold (first mold) 52 Movable mold (second mold) 53 Cavity 64 Sprue (pre-material passage) 65 Heater (Heating means) 67 Runner (previous material passage) 68 Heater (heating means) 71 Inlet 72 Valve unit (inlet opening and closing means) 74 Flow passage (previous material passage) 75 Heater (heating means) 91 Moving plate (moving body, Type) 92 Spring (biasing means) 96 Subrunner (subsequent material passage) 97 Gate

Claims (4)

[Claims] 1. A filling step of filling a cavity formed between mold bodies that open and close with each other with a thermoplastic molding material through a gate from a molding material supply device to a material passage and a cavity, and a final step after completion of the filling step. A final mold closing step of closing the mold bodies together, and during this final mold closing step, after returning the molding material from the cavity to the material passage side through the gate, the gate is closed and thereafter the inside of the cavity is closed. In the injection molding method for compressing the molding material, the molding material in the material passage is always kept in a molten state by heating, and before the mold body is finally closed, a gate which operates independently of opening and closing of these mold bodies. An injection molding method, wherein the gate is closed by opening / closing means. 2. An injection molding die apparatus used in the injection molding method according to claim 1, wherein the first and second dies are opened and closed to form a cavity therebetween when the dies are closed. And the volume of the cavity is made variable in accordance with the opening and closing operations of these two molds.
A material passage located inside the mold, a gate for opening the material passage to the cavity, a heating means for keeping the molding material in the material passage in a molten state at all times, and independent of the opening and closing of the molds. And a gate opening / closing means for operating the gate to open and close the gate. 3. A filling step of filling a cavity formed between the mold bodies that open and close with each other with a thermoplastic molding material through a gate from a molding material supply device to a material passage and a cavity, and a final step after completion of the filling step. A final mold closing step of closing the mold bodies together, and during this final mold closing step, after returning the molding material from the cavity to the material passage side through the gate, the gate is closed and thereafter the inside of the cavity is closed. Between the molds which are compressed before the filling process and which do not move during the final mold clamping process, and which communicate with the preceding material passage in one of the molds via the inlet. In the injection molding method to be formed, the gate from the subsequent material passage to the cavity is closed by the operation of the mold in the final mold clamping step, and the molding material in the preceding material passage is added. An injection molding method, characterized in that the injection port is kept in a molten state by heat, and the injection port is closed by an injection port opening / closing means that operates independently of opening and closing of the mold before the gate is closed. 4. An injection molding die apparatus used in the injection molding method according to claim 3, wherein the first die and the second die are opened and closed with each other to form a cavity therebetween when the die is closed. A movable body that is movably supported by one of the molds in the opening and closing direction of the two molds and forms a post-stage material passage between the other mold and the one of the molds; Biasing means for biasing the other mold toward the other, while making the volume of the cavity variable with the opening and closing operation of the two molds, and a gate from the subsequent material passage to the cavity. A first material passage which is opened and closed, and a first material passage located inside the first mold member, an inlet for opening the first material passage to the second material passage, and a molding in the first material passage; The heating means for keeping the material in a molten state at all times and the opening and closing of the two molds are independent. An injection opening / closing means for operating the injection opening to open and close the injection opening.