JPH0667583B2 - Injection molding apparatus and method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an injection molding apparatus and method, and more particularly, to an injection molding apparatus and method.
The present invention relates to a mold clamping structure and method of an injection molding apparatus for molding an optical lens.

(Prior Art) As a conventional injection molding apparatus of this type, one shown in FIGS. 5 to 10 is known.

In FIGS. 5 and 6, a mold piece 2 having a mirror surface 2a is fitted and inserted into a movable mold plate 1 which is driven to move in the A-axis direction, and a cavity 3 has a movable mold plate 1 and a mold. It is defined by a piece 2 and a fixed-side template 4. The movable side mold plate 1 and the mold piece 2 are supported by a movable side die plate 6 via a receiving plate 5, and the fixed side mold plate 4 is supported by a fixed side die plate 7. Movable mold plate 1, mold piece 2, fixed mold plate 4
The die 8 including the receiving plate 5 is clamped by the tension generated in the tie bar 9 via the fixed side die plate 7 and the movable side die plate 6, that is, the die 8 is clamped by the clamping force in the A-axis direction. It is supposed to be done.

(Problems to be Solved by the Invention) However, in such a conventional injection molding apparatus and method, since the mold 8 is clamped only by the mold clamping force in the moving direction of the movable side die plate 6, There is a problem that the precision of the molded product is lowered, or the cost of the molded product is increased as the die 8 is enlarged.

That is, when the molten resin is injected and filled into the cavity 3, an injection pressure is applied to the mold 8 and the mold 8 tends to deform. Deformation of the mold 8 in the moving direction of the movable die plate 6 is prevented by the mold clamping force.
The deformation in the direction orthogonal to the moving direction of the mold cannot be prevented, and the mold 8 is deformed as shown from the phantom line in FIGS. 7 to 10 to the solid line. However, since the deformation of the mold 8 is minute in the cross section shown in FIG. 7, an imaginary line is not shown. For this reason,
The precision of the molded product formed in the cavity 3 decreases. In particular, when the mold piece 2 is used, the clearance between the mold piece 2 and the movable-side mold plate 1 is expanded due to the deformation of the mold 8, and as shown in FIG. The molten resin enters and causes burrs. The burr remains after the molded product is taken out, and the mold 8 is deformed in the direction of increasing the clearance, so that the burr tends to become thicker every shot. Due to the occurrence of burrs, the vicinity of the edge of the mirror surface 2a of the mold piece 2 is elastically deformed, and the mirror surface accuracy of the molded product deteriorates. However, the elastic deformation near the edge of the mirror surface 2a is restored by cleaning the inside of the mold.

Further, in order to prevent the above-mentioned deterioration of the precision of the molded product, it is conceivable to increase the strength of the mold 8, but in this case, the mold 8 is enlarged or the mold 8 is made of a highly rigid material. It is necessary to configure the mold, and it is inevitable that the mold 8 becomes large and the cost of the molded product increases.

The deformation of the die 8 due to the resin pressure described above is such that the greater the resin pressure, the larger the projected area of the cavity 3 in the direction orthogonal to the mold clamping direction, and the less the rigidity of the die 8 (of the mold material). The smaller the Young's modulus, the smaller the mold dimension in the direction orthogonal to the mold clamping direction.

(Object of the Invention) Therefore, the present invention prevents deformation of the mold in a direction orthogonal to the mold clamping force direction by pressing the mold in a direction orthogonal to the moving direction of the movable side die plate, The purpose is to improve the precision of the molded product while reducing the cost of the molded product and downsizing the mold.

(Structure of the Invention) In order to achieve the above object, the injection molding apparatus according to the present invention has a mold plate, and a mold piece is fitted to at least one mold plate, and a cavity is defined by the mold plate and the mold piece. A pair of molds, a mold clamping mechanism for clamping the pair of molds, and a pressing mechanism for generating a pressing force in the pair of molds in a direction orthogonal to the mold clamping direction. In addition, a pair of molds are brought into contact with each other to clamp the molds, a cavity is formed between the molds, and then the molds in the clamped state are pressed in a direction orthogonal to the mold clamping direction. The invention is characterized by injecting and filling resin into the cavity after pressing with pressure. Furthermore, a cavity unit mold is attached to the injection molding machine, and the resin is injected into the cavity by the injection molding machine.
After the filling, the cavity unit mold is removed from the injection molding machine and moved to another place, where the molded product in the cavity unit mold is cooled, in the injection molding method, Before injection and filling, the cavity unit mold is clamped, a cavity is formed between the molds, and then a pressing force is applied in a direction orthogonal to the mold clamping direction, and then resin is injected into the cavity. It is characterized by injection and filling.

Hereinafter, the present invention will be described based on examples.

1 to 3 are views showing a first embodiment of an injection molding method according to the present invention and an injection molding apparatus for achieving the method,
The projected area of the cavity in the K-axis direction in FIG. 2 is M in FIG.
This is an example applied to a die larger than that in the axial direction.

First, the configuration will be described.

In FIGS. 1 and 2, 11 is a fixed-side die plate supported by a molding machine body (not shown), and 12 is a movable-side die plate supported by the molding machine body. The movable die plate 12 is driven by a drive mechanism (not shown) to
It moves in the P-axis direction in the figure, that is, moves toward and away from the stationary die plate 11. Fixed side die plate 11
One mold 13 of the pair of molds 13 and 14 is supported by, and the other mold 14 is supported by the movable die plate 12. The mold 13 comes into contact with and separates from the mold 14 by the movement of the movable side die plate 12, and the cavity 15 is formed by the contact between the pair of molds 13 and 14. The mold 13 is composed of a fixed-side mold plate 16, and the mold 14 is a movable-side mold plate 17 and a movable-side mold plate.
A mold piece 18 and a receiving plate 19 each having a mirror surface 18a inserted into the 17
Consists of. Cavity 15 has fixed side template 16 and movable side template 17
And the mold piece 18, the projected area of the cavity 15 in the K-axis direction in FIG. 2 is larger than the projected area in the M-axis direction in FIG. 20 is a pair of molds that abut each other
A mold clamping mechanism for clamping the molds 13 and 14 through the fixed side die plate 11 and the movable side die plate 12 (details not shown).
The mold clamping mechanism 20 has a plurality of tie bars 20a. The tie bar 20a surrounds the molds 13 and 14 and extends in the moving direction of the movable die plate 12. The dies 13 and 14 are fixed side die plate 1 by the tension generated in the tie bar 20a.
The die is clamped by being pressed along the P-axis direction in FIG. 1 via the 1 and the movable die plate 12.

Here, 21 and 22 are a pair of support brockes, both ends of the support block 21 are respectively supported by a pair of tie bars 20a on the right side of FIG. 2, and both ends of the support block 22 are on the left side of FIG. Each is supported by a tie bar 20a. Pressing bolts 23 and 24 are threaded and penetrate through the support blocks 21 and 22, respectively, and the tips of the pressing bolts 23 and 24 are in contact with the left and right surfaces of the molds 13 and 14 in FIG. There is. That is, when the pressing bolts 23 and 24 are screwed in, the molds 13 and 14 are pressed by the pressing bolt 23 from the right direction in FIG. 2 along the K axis direction, and the pressing bolts 24 and 24 along the K axis direction. Is pressed from the left side.

Therefore, the support blocks 21, 22 and the pressing bolt 23,
The numeral 24 constitutes a pressing mechanism 25 for pressing the molds 13 and 14 in the K-axis direction orthogonal to the moving direction of the movable die plate 12. Further, one end of the pressing mechanism 25 is engaged with the tie bar 20a, and the other end is in contact with the molds 13 and 14.

According to such a configuration, when the cavity 15 is injected and filled with the molten resin, the projected areas of the molds 13 and 14 in the K-axis direction are large, so that the molds 13 and 14 are phantom lines of FIG. 2 due to the injection pressure. However, the deformation is prevented by the pressing mechanism 25. Therefore, the deformation of the cavity 15 at the time of injection filling can be prevented, and the precision of the molded product can be improved. The molds 13 and 14 try to deform so as to expand in the P-axis direction and the M-axis direction by the injection pressure, but the deformation in the P-axis direction is prevented by the mold clamping force of the tie bar 20a, and the deformation in the M-axis direction occurs. Has a small projected area and therefore is very small, and does not affect the accuracy of the molded product without particularly preventing deformation. Needless to say, the tightening force of the pressing bolt 23 is increased / decreased according to the magnitude of the resin pressure. Further, in this embodiment, since the mold piece 18 is fitted on the movable side mold plate 17 and the fixed side mold plate 16 and the mold piece 18 are in contact with each other to define the cavity 15, the mold piece is formed. If only 18 is replaced, a pair of molds
Different molded products can be easily molded with 13 and 14.
Further, when manufacturing the mold 14, the mirror surface 18a can be easily processed. That is, it is very difficult to mirror-finish the cavity surface of the mold because the cavity is concave, but by making the mold piece 18 a separate body,
The mirror surface 18a can be easily processed. Further, since the highest resin pressure is applied to the mirror surface 18a, it is very easily damaged, but since this part is used as the mold piece 18, the mold 14 can be repaired very easily only by replacing the mold piece 18. The effect is that you can.

Further, when the present embodiment is carried out by a so-called gate seal injection molding method, that is, after the molten resin is injected into the cavity 15, the gates provided in the sprues of the molds 13 and 4 are closed and the molten resin is injected into the cavity 15. In the case of molding so that the pressure in the cavity 15 is kept at a predetermined value until the molten resin is solidified, the pressure in the cavity 15 changes as shown in the graph of FIG. Cavity 15
Immediately after closing the gate, the internal pressure is 1200 kg f / cm
More than ² (300-800 kg f / cm ^{2 in} normal injection molding)
Therefore, the pressing mechanism 25 exerts an effect even against such a high pressure, and the deformation of the molds 13 and 14 can be prevented. The pressure inside the cavity 15 is 300kgf / cm ² or more 2 ~
Since the resin in the cavity 15 has high temperature and low viscosity for 3 minutes, if the molds 13 and 14 are deformed during this period, the mold piece
Burrs are likely to occur between 18 and the template 17. Therefore, by providing the pressing mechanism 25 as in the present embodiment and operating for only 2 to 3 minutes so that the pressure in the cavity 15 becomes 300 kgf / cm ² or more, the design strength of the molds 13 and 14 themselves is 300 kgf. / C
Even if it can handle m ² , it is possible to prevent deformation of the molds 13 and 14. In other words, after a lapse of 2 to 3 minutes when the pressure becomes 300 kgf / cm ² or more, the dies 13 and 14 are moved to the tie bar 20a.
The mold may be clamped by. With this configuration, the mold can be downsized and the cost of the mold can be reduced.

Further, although not shown, a mold clamping self-holding mechanism such as bolt tightening may be adopted as the pressing mechanism instead of the pressing mechanism 25. That is, even when using a so-called cavity unit mold in which the molds 13 and 14 near the cavity are detachably unitized, it is possible to take out the mold from the injection molding machine and prevent deformation and burrs of the mold. .

In this case, a large number of cavity unit dies are prepared, the cavity unit dies are mounted on the injection molding machine, the cavity is injected and filled by the injection molding machine, and then the cavity unit dies are injected. It is removed from the molding machine and moved to another place where the molded product in the cavity unit mold is cooled. In this case, the cavity unit mold is clamped and a cavity is formed between the molds before the resin is injected and filled by the injection molding machine, and then the cavity unit mold is pressed in a direction orthogonal to the mold clamping direction. After pressing with pressure, resin may be injected and filled in the cavity.

In this way, even if the cavity unit mold is not left attached to the injection molding machine for a long time (for example, several tens of minutes) for cooling, it is removed within 2-3 minutes after injection filling and the molded product is removed. Therefore, there is an effect that the molding cycle can be shortened.

FIG. 4 is a view showing a second embodiment of the injection molding apparatus for achieving the injection molding method according to the present invention. In the mold shown in FIG. 4, the projected areas of the cavities in the L-axis direction and the N-axis direction are almost the same. This is an example of application. In addition, in FIG.
The same components as those in the first embodiment shown in the drawings are designated by the same reference numerals as those in the first embodiment shown in FIGS. 1 and 2, and the description of the components will be omitted.

In FIG. 4, 31 is a pair of molds having a cavity 31a, and the mold 31 is the same as the fixed side mold plate 16, the movable side mold plate 17, the mold piece 18 and the receiving plate 19 of FIGS. The cavity 31a is formed in the L axis direction and the N direction.
The projected areas in the axial direction are almost equal. A support block 32 and a hydraulic cylinder 33 are provided between the die 31 and each tie bar 20a, and the support block 32 is supported by the tie bar 20a. The hydraulic cylinder 33 is supported by the support block 32 and is in contact with the mold 31, and when each hydraulic cylinder 33 operates, the mold 31 is pressed by the reaction force of the tie bar 20a via the support block 32. That is, the die 31 is pressed from four directions, that is, both sides in the L-axis direction and both sides in the N-axis direction. Therefore, the support block 32 and the hydraulic cylinder 33 constitute a pressing mechanism 34 for pressing the die 31 from the L-axis direction and the N-axis direction orthogonal to the moving direction of the movable die plate 12.

Here, when the molten resin is injected and filled in the cavity 31a, the projected areas of the cavity 31a in the L-axis direction and the projected area in the N-axis direction are almost the same, so that the mold 31 is deformed as shown by the phantom line in FIG. However, the pressing mechanism 34 prevents the deformation. Therefore, this embodiment can obtain the same effects as those of the first embodiment shown in FIGS.
The same great advantages as those of the first embodiment can be obtained by applying the same method to the injection molding by the gate seal injection molding method as in the embodiment and by using both the gate seal injection molding method and the cavity unit mold. You can

It should be noted that the number and arrangement of the pressing mechanisms 25 and 34 are not specified, and the required number of pressing mechanisms 25 and 34 may be provided at a place where the mold is easily deformed.

Further, the pressing mechanisms 25 and 34 may have a structure driven by a cam or an electromagnetic drive, for example.

(Effect) According to the present invention, since the mold is pressed in the direction orthogonal to the mold clamping direction, even if the mold strength is weak,
The deformation of the mold in the direction orthogonal to the mold clamping force direction can be prevented, and the accuracy of the molded product can be improved while reducing the size of the mold and reducing the cost of the molded product. In addition to this, since the mold is configured such that the mold piece is fitted to at least one of the mold plates and the mold plate and the mold piece are in contact with each other to define the cavity, only the mold piece is provided. By exchanging, it is possible to easily mold different molded products with the mold. Further, when manufacturing the mold, the mirror surface can be easily processed. That is, it is very difficult to mirror-finish the cavity surface of the mold because the cavity is concave, but the mirror surface can be easily processed by using a separate mold piece. Further, since the highest resin pressure is applied to the mirror surface, it is very easily damaged, but since this part is used as a mold piece, the mold can be repaired very easily only by replacing the mold piece.

Further, according to the present invention, the cavity unit mold is clamped and the cavity is formed between the molds before the injection and filling of the resin by the injection molding machine, and then the mold is orthogonal to the mold clamping direction. After pressing with a pressing force in the direction, resin is injected and filled in the cavity, then the cavity unit mold is removed from the injection molding machine and moved to another place,
Therefore, the molded product in the cavity unit mold is cooled, so even if the cavity unit mold is not attached to the injection molding machine for a long time for cooling, it is removed in a short time after injection filling and the molded product is removed. It can be cooled in the state and the formation cycle can be shortened.

[Brief description of drawings]

1 to 3 are views showing a first embodiment of an injection molding apparatus according to the present invention, FIG. 1 is a front view of a main part thereof including a partial cross section, and FIG. 2 is XX in FIG. FIG. 3 is a sectional view taken in the direction of the arrow, FIG. 3 is a graph showing a change in resin pressure in the cavity after the injection and filling, and FIG. 4 is a sectional view of the essential parts showing a second embodiment of the injection molding apparatus according to the present invention. 5 to 10 are views showing a conventional injection molding apparatus, FIG. 5 is a front view of a main part including a partial cross section, FIG. 6 is a cross sectional view taken along the line YY in FIG.
7 is a sectional view of the main part of the die, FIG. 8 is a sectional view taken along the line ZZ in FIG. 7, FIG. 9 is a sectional view taken along the line VV in FIG. 8, and FIG. It is a principal part expanded sectional view of a metal mold | die. 11 …… Fixed side die plate, 12 …… Movable side die plate, 13, 14, 31 …… Pair of molds, 15, 31a …… Cavity, 16 …… Fixed side template (template), 17 …… Movable mold plate (mold plate), 18 ... Mold piece, 20 ... Mold clamping mechanism, 20a ... Tie bar, 25, 34 ... Pressing mechanism.

Claims (3)

[Claims] 1. A pair of molds each having a mold plate, a mold piece being fitted to at least one mold plate, and defining a cavity by the mold plate and the mold piece, and the pair of molds. An injection molding apparatus comprising: a mold clamping mechanism for clamping the mold and a pressing mechanism for generating a pressing force in the pair of molds in a direction orthogonal to the mold clamping direction. 2. A pair of molds are brought into contact with each other to clamp the molds, a cavity is formed between the molds, and then the molds in the clamped state are pressed by a pressing force in a direction orthogonal to the mold clamping direction. After that, the injection molding method is characterized in that the resin is injected and filled in the cavity. 3. A cavity unit mold is attached to an injection molding machine, resin is injected and filled in the cavity by the injection molding machine, and then the cavity unit mold is removed from the injection molding machine and moved to another location. Then, in the injection molding method in which the molded product in the cavity unit mold is cooled, the cavity unit mold is clamped before the injection and filling of the resin by the injection molding machine, and An injection molding method, characterized in that a cavity is formed between them, and then a pressing force in a direction orthogonal to the mold clamping direction is applied, and then a resin is injected and filled into the cavity.