JP2002067113A - Mold for injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold for injection molding capable of easily preventing occurrence of a flash or a decrease in a dimensional accuracy by reducing an influence of a bending deformation of a mold mounting platen only by a constitution of a mold without changing a constitution of a mold clamping unit side. SOLUTION: The mold for injection molding comprises a force transmitting section 71c corresponding to a projecting surface of a molding space 75 in a mold clamping direction between the mold 70 and a mold mounting plate 72 so that a mold clamping force is transmitted to the mold 70 only via the transmitting section 71c.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for injection molding, and more particularly, to a mold main body having a concave or convex portion for forming a molded product at a joining surface at one end for forming a space for forming a molded product. And a mold mounting plate having an area larger than the joining surface of the mold body and being bolted to the other end face of the mold body.

[0002]

2. Description of the Related Art Heretofore, it has been mounted on a fixed or movable mold plate which obtains a mold clamping force by a plurality of tie bars arranged on an outer peripheral portion, and a space for forming a molded product is formed at a joining surface at one end. A mold body having a concave or convex portion for forming a molded article, and having an area larger than a joining surface of the mold body,
Various injection molding dies have been proposed which include a mold mounting plate which is connected to the other end surface of the mold body by bolts.

FIGS. 5 to 9 show a conventional injection molding machine using such an injection molding die. The injection molding machine shown in FIGS. 5 to 8 is a mold clamping device 10, a base 11 for supporting the mold clamping device, and fixed to one end of the base 11, and has a substantially square shape when viewed from the front. A fixed plate 12, two rails 13 fixed on the base 11,
The movable plate 14 slides on the rail 13 to move forward and backward with respect to the fixed plate 12, and one end thereof is movable by a nut 16 with a movable plate 14 having a substantially square shape when viewed from the front. 14, four tie bars 15 fixed at the four corners and having a threaded portion 15a at the other end, and two small-diameter, large-stroke mold opening / closing cylinders 17 mounted between the fixed board 12 and the movable board 14. A large-diameter, small-stroke mold clamping cylinder 18 incorporated in four corners of the board 12,
(Ram) (piston) 19. The ram 19 of the mold clamping cylinder 18 has a sleeve 19a protruding out of the fixed platen 12 and a hole at the center through which the tie bar 15 can be inserted.

Further, in these figures, reference numeral 20 denotes a half nut which can be opened in the radial direction, and when closed, meshes with the threaded portion 15a of the tie bar 15;
0 is a support rod that slidably supports the nut 22.
23, which constantly urges in the direction of the mold clamping cylinder 18,
Is an injection device installed in an injection port 12a formed at the center of the fixed platen 12, 30 is a fixed mold composed of a fixed mold body 31 and a fixed mold mounting plate 32, and 31a is a fixed mold body 3
The molded product forming recess 33 provided in 1 is a movable mold composed of a movable mold body 34 and a movable mold mounting plate 35, 34a
Denotes a convex part for forming a molded product provided on the movable mold body 34.

[0005] The fixed mold body 31 includes a fixed mold mounting plate 32.
And is attached to the mounting surface of the fixed plate 12 by bolts or clampers. Similarly, the movable mold body 34
It is mounted on the mounting surface of the movable platen 14 by bolts or clampers via a movable mold mounting plate 35. Fixed board 12
The mounting surface of the movable platen 14 is formed on a surface having a high flatness. Although not shown, the mounting surfaces of the fixed platen 12 and the movable platen 14 are provided with female threads for bolts for mounting a mold mounting plate and T-grooves for mounting clampers.
Also, the molded product forming concave portion 31a and the molded product forming convex portion 34 are formed.
In a, a space (cavity) 36 (see FIG. 7) for forming a molded product is formed when the fixed mold body 31 and the movable mold body 34 are joined.

Next, the operation of the mold clamping device 10 of the injection molding machine shown in FIGS. 5 to 8 will be described. First, the movable platen 14 is moved in the direction of the fixed platen 12 at high speed by using the mold opening / closing cylinder 17 to close the mold so that the movable mold body 34 and the fixed mold body 31 come into contact with each other. At this time, the tip of the tie bar 15 penetrates through the center hole of the ram 19 of the mold clamping cylinder 18, and the screw portion 15 a enters the opened half nut 20. Here, the half nut 20 is closed, meshed with the screw portion 15a of the tie bar 15, and the two are joined. Next, when the ram 19 of the mold clamping cylinder 18 is moved to the right in FIG. 5, the sleeve 19a pushes the half nut 20, and the half nut 20 pulls the tie bar 15 to the right in FIG. In response, the movable platen 14 is pushed toward the fixed platen 12. Thereby, the fixed mold 30 and the movable mold 33 are strongly clamped.

In this state, the molten resin is injected into the molded product forming space 36 from the injection port 12a using the injection device 23. After the resin in the space 36 has been cooled and solidified, the mold clamping device 10 is operated in the reverse operation to take out the molded product in the mold.

FIG. 7 shows a state in which the mold clamping device 10 is clamped and an injection pressure is applied to the space 36 for forming a molded product. As shown in the figure, the high resin pressure in the molded product forming space 36 acts in a direction to separate the fixed mold body 31 and the movable mold body 34. Here, the states of the forces applied to the fixed platen 12 and the fixed die 30 and the movable plate 14 and the movable die 33 are substantially symmetrical.
The following description focuses on the fixed mold 30 side. Pressing force (distributed load) by the movable mold body 34 from the left side to the fixed mold 30
p1 and the pressing force (distributed load) p2 of the injection resin are applied. On the other hand, a concentrated force P1 (4P1 as a whole) is applied to the fixed plate 12 via the four half nuts 20 from the right side. Are balanced. Here, the pressing force p1 is large immediately after the mold clamping, but the distributed load is reduced by the injection of the resin, and the pressing force p2 is the distributed load applied to the projection surface of the molded product forming space 36 in the mold clamping direction. .

The fixed platen 12 and the fixed mold 30 are bent three-dimensionally by the bending moments generated by the pressing forces p1 and p2, as shown in an exaggerated manner in FIG. As a result, the fixed platen 12 is deformed so that the four corners are fixed and the central portion is concave in cross section.
The fixed mold mounting plate 32 in contact with 2 receives large forces at the four corners and similarly deforms the central portion into a concave cross section, and similarly, the fixed mold body 31 also deforms the central portion into a concave cross section. Therefore, the pressing force p1 between the fixed mold 31 and the movable mold body 34 is reduced at points m and n at the center of the four sides of the fixed mold body 31, and a gap is generated near the points m and n. As a result, there is a problem that a problem that burrs occur in the molded product occurs.

FIG. 9 shows another example of a conventional injection molding machine using the above-mentioned injection mold. The injection molding machine includes a mold clamping device 40 and a base 4 supporting the mold clamping device.
1, a fixed platen 42 fixed to one end of a base 41, a base 4
1 is an end plate 43 fixedly mounted opposite the fixed plate 42 at the other end.
And four tie bars 44 connecting the four corners of the fixed plate 42 and the end plate 43 with the mounting bracket 45, and are disposed between the fixed plate 42 and the end plate 43, and the four corners are slidably pulled by the tie bars 44. A movable plate 46 that moves forward and backward on the base 41, a mold clamping cylinder 47 fixed to the end plate 43, and a movable plate 46
, A fixed mold 48, a fixed mold body 49 and a fixed mold mounting plate 50, a movable mold 51, a fixed mold body 52 and a fixed mold And a mold mounting plate 53.

Next, the operation of the mold clamping device 40 shown in FIG. In addition, this apparatus is different from that shown in FIG. 5 only in that the mold opening / closing and the mold clamping operation are performed by one mold clamping cylinder 47, and the other operations are almost the same. Only the operation of will be described.

First, the load state of the fixed platen 42, the fixed die 48, the movable platen 46, and the movable die 51 when the mold clamping device 40 is in the mold closed state will be described. Therefore, this load state will be described with reference to FIG. 9 showing the mold open state. The pressing force from the movable mold body 52 is applied to the fixed platen 42 and the fixed mold 48 from the left side in FIG. p3 (distributed load) and pressing force p4 (equally distributed load) from the injection resin are applied, and a concentrated force P2 (4P2 in total) is applied from the tie bar 44 from the right side in FIG. The pressing force p3 from the fixed die main body 49 and the pressing force p4 from the injection resin are applied to the mold 51 from the right side in the figure, and the mounting portion of the rod 47a of the mold clamping cylinder 47 from the left side in the figure. Pressing force p5 (4P in total)
2) is applied, and the left and right pressing forces are balanced with each other.

In the mold clamping device 40, the mold clamping cylinder 4
Since the center portions of the movable platen 46 and the movable mold 51 are pressed by the rod 47a of No. 7, in the state where the pressing forces from the left and right sides are balanced as described above,
There is no gap at the center of the mold. However, the same bending deformation problem as in the case of the mold clamping device 10 shown in FIG. 5 occurs on the fixed platen 42 and the fixed mold 48 side. Therefore, also in the mold clamping device 40, similarly to the case of the fixed plate 12 and the movable plate 14 of the mold clamping device 10 shown in FIG. The bending deformation reduces the mold clamping force in the vicinity of the center of the four sides of the mold, causing burrs on the molded product and causing problems of poor dimensional accuracy.

Under such circumstances, various methods have conventionally been proposed for solving the problem of bending deformation caused by using a tie bar. For example, Tokuho 6
In -41160 and Japanese Utility Model Application Laid-Open No. 7-35020, a fixing plate of a device having a configuration such as the above-described mold clamping device 40 includes a member for attaching a die but not connected to a tie bar, It has been proposed that a mold clamping device be constituted by three members of a force transmitting member having a small area connecting the both. Also, in JP-A-7-88913,
The method of clamping the fixed platen and movable platen does not matter, but the mold mounting plate is reduced to a size close to the projection surface of the molding space (cavity) to increase the clamping force at the center of the mold. A mold has been proposed.

[0015]

However, in practice, in order to solve the problems of burrs and reduction in dimensional accuracy caused by the method of obtaining a mold clamping force using a tie bar as described above, Japanese Patent Application Publication No. It is necessary to change the configuration of the mold clamping device in the proposal of JP-A-41160 and Japanese Utility Model Application Laid-Open No. 7-35020. There were inconveniences such as difficulty in mounting, and implementation was not easy.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and only by changing the shape or configuration of the mold without changing the configuration of the mold clamping device.
Provided is an injection molding die capable of preventing large bending deformation from occurring in a die, thereby easily preventing burrs from being generated on a molded product and reducing dimensional accuracy thereof. The purpose is.

[0017]

According to the present invention, in order to achieve the above object, a mold body having a molded product forming concave or convex portion for forming a molded product forming space at a joining surface at one end. And a mold mounting plate having an area larger than the joining surface of the mold body and being bolted to the other end surface of the mold body. The end face is brought into contact with the mold mounting plate via a portion corresponding to a projection surface of the molded product forming space in the mold clamping direction.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an injection mold according to the present invention will be described in detail with reference to the drawings. In addition,
The mold for injection molding of the present invention can be employed in the mold clamping devices 10, 40 and the like of the conventional injection molding machine shown in FIGS. The configuration shown in FIGS. 5 to 9 and the like will be referred to for the configuration, and the description thereof will not be repeated. In addition, the fixed mold or the movable mold, and the fixed platen or the movable platen, both have almost the same structure, so that regardless of whether it is fixed or movable, hereinafter, these are referred to as a mold and a movable platen. This will be described with reference to a mold plate.

(First Embodiment) FIGS. 1 and 2 show a first embodiment of an injection mold according to the present invention. In particular, the mold of an injection molding machine to which the mold is applied. 3 shows a main part of the fastening device. The injection mold (fixed mold or movable mold) 70 of the present embodiment has a mold plate (fixed plate or movable plate) 60 in which tie bars (not shown) are arranged at four corners, similarly to the conventional example. To the mold plate 6 with tie bars.
A tightening force is applied via the zero. The mold 70 includes an injection port provided when the mold is a fixed mold, an ejection pin device for removing a molded product provided when the mold is a movable mold, and the like, but these are not shown. I have.

The mold 70 includes a mold body 71 having a substantially square shape when viewed from the front, and a mold mounting plate 72 on which the mold body is integrally mounted. The mold main body 71 is disposed so as to face a counterpart mold body (not shown) (see part of FIG. 5), and has a good flatness joint surface 71a to be joined to the counterpart mold body at the time of mold clamping. have. The joint surface 71a is provided with a concave part for forming a molded article (when the mold body is a fixed mold) or a convex part for forming a molded article (when the mold body is a movable mold). Mold body 71
Is a space (cavity) for forming a molded product by using a concave portion (or a convex portion) for forming a molded product and a convex portion (or a concave portion) for forming a molded product of the partner when they are bonded to each other.
75 are formed. In FIG. 1, a solid product forming concave portion is shown by a solid line, and a mating product forming convex portion is shown by a two-dot chain line.

On the other end surface of the mold body 71 opposite to the joining surface 71a, a peripheral portion thereof is removed by an appropriate thickness c to form a step-like removal processed portion 71b. In the center of the other end surface of the mold body 71, a force transmitting portion 71c protruding from the removal processing portion 71b is formed. An end surface of the force transmitting portion 71c is a mounting surface 71d of the mold mounting plate 72, and is provided with a plurality of female screws 71e. The mounting surface 71d is formed in a shape (square in this embodiment) substantially equal to or slightly smaller than the projection surface of the molded product forming space 75 in the mold clamping direction as shown in FIG.

The mold mounting plate 72 has a plurality of counterbored bolt holes 72a. The mold mounting plate 72 is inserted into the female screw 71 of the mold body 71 through the plurality of bolt holes 72a.
e, is fixed to the mold body 71 by a plurality of hexagon socket head bolts 73 screwed into the mold body 71. Also, the mold mounting plate 7
2, a plurality of mounting bolt holes 72 for mounting a mold.
b is provided. The die mounting plate 72 is attached to the die plate 60 by a plurality of mounting bolts 74 passed through the mounting bolt holes 72b, or is formed on the die plate 60 by using a plurality of clampers 76 as shown by two-dot chain lines in FIG. Mounted.
As a result, the mold clamping force applied to the mold 70 is
From the mold mounting plate 72 and the mounting surface 71d of the force transmitting portion 71c.
Is transmitted to the mold body 71 through

Next, the operation of the mold 70 having the above configuration will be described. In the mold body 71, a pressing force p6 from a partner mold body (not shown) is applied to the joining surface 71a from the left side in FIG. Pressure p7 is applied. In the mold body 71, a pressing force p8 from the model number 60 is applied to the mounting surface 71d of the force transmitting portion 71c from the right side in FIG. In this state, these left and right pressing forces are balanced.
Here, the pressing force p8 applied from the right side in FIG. 1 is a distributed load whose magnitude varies depending on its position, and its working range is the mounting surface 71d of the mold body 71, that is,
It is limited within the force transmitting portion 71c that forms a portion corresponding to the projection surface of the molded product forming space 75 in the mold clamping direction. Therefore,
Even if the force on the outer peripheral side increases due to the bending deformation of the mold mounting plate 72, a large bending moment does not occur in the mold body 71 due to these pressing forces.
Bending deformation hardly occurs in the mold body 71.

In the present embodiment, since the system including the mold plate 60, the mold mounting plate 72, and the mold body 71 which receives the mold clamping force from the tie bar has an indeterminate structure, the external force applied to each part is Although the deformation is complicated, it has been found by finite element analysis that the bending deformation of the mold body 71 can be suppressed to a sufficiently small value. Since the gap formed between the removal processing surface 71b of the mold body 71 and the mold mounting plate 72 is extremely small even in the outer peripheral portion where the change is large, the removal processing thickness c
(Same as the height of the force transmitting portion 71c) is sufficient if 0.2 mm or more, and c = 0.2 to reduce the removal processing.
It is preferably 0.5 mm.

(Second Embodiment) FIG. 3 shows a second embodiment of the injection mold according to the present invention. Note that, in FIG. 3, elements having the same functions and functions as those shown in FIG. 2 are denoted by the same reference numerals as those shown in FIG. Mold 70 'of the present embodiment
Has substantially the same structure as that of the first embodiment, and only the differences from the first embodiment will be described.
The difference is that the shape as viewed from the front is formed as a horizontally long rectangle (rectangle). In the mold 70 ', the bending deformation in the horizontal direction is easy to occur, but the bending deformation in the vertical direction is hard to occur. Therefore, in the present embodiment, the removal processing surface 71b 'is
0 'is provided only at both ends in the horizontal direction.

(Third Embodiment) FIG. 4 shows a third embodiment of the injection mold according to the present invention. The structure of the mold 80 of this embodiment is almost the same as that of the first embodiment, and therefore only the differences from the first embodiment will be described. The mold 80 includes a mold body 81, a joining surface 81a of the mold body, a back surface 81b, a plurality of female screws 81c provided on the back surface 81b, and a force transmitting portion 82, It is almost the same as the mold 70 shown in FIG. The other elements are given the same numbers as the elements shown in FIG. 1, and the description thereof is omitted.

The mold 80 of the present embodiment has the force transmitting portion 8
2 is different from the mold 70 of the first embodiment in that the mold 2 is formed using a polished steel plate having an appropriate thickness and an appropriate thickness. The force transmitting portion 82 is provided with a bolt hole 82a, and is clamped and fastened together by the hexagon socket bolt 73 screwed into the female screw 81c of the mold body 81 through the bolt hole 82a. Is fixed. The shape of the force transmitting portion 82 as viewed from the front is the mold body 71 of FIG.
By attaching this force transmitting portion 82 to the mold body 81, the rear surface 81b of the mold body 81 is formed in the same manner as the mold 70 without processing the mold body 81 itself. A gap can be formed between the mold mounting plate 72 and the mold mounting plate 72. The operation of the mold 80 is similar to that of the mold 70 shown in FIG.
Since this is the same as the case described above, the description thereof is omitted.

It should be noted that the mold 7 in the embodiment described above is used.
Although 0, 70 ', and 80 were formed in a square or a rectangle such as a square or a rectangle when viewed from the front, the present invention is not limited to this, and a polygon, an ellipse, or any other shape may be used. Can be applied. In addition, the third
In the embodiment, the steel plate is attached to the mold body 81 side, and the force transmitting portion 82 is provided on the mold body side. However, the present invention is not limited to this. Of course, it is also possible to provide the force transmitting portion 82 on the mold mounting plate side by mounting.

[0029]

As described above, according to the injection molding die according to the present invention, the die main body is provided with a portion of the other end surface corresponding to the projection surface of the space for forming a molded product in the direction of clamping. Since the configuration is such that it is brought into contact with the mold mounting plate through the intermediary, the following effects can be obtained. (1) The mold clamping force is transmitted to the mold body only through a portion of the other end surface of the mold body corresponding to the projection surface of the space for forming a molded product in the mold clamping direction. Bending deformation is prevented as much as possible on the mold body. Thus, the tightening force is reduced at the center of the four sides of the joining surface of the mold to form a gap, thereby preventing occurrence of burrs and reduction in dimensional accuracy. (2) Since it can be manufactured by adding a slight change to the conventional mold and can be attached to and removed from the mold plate in the same manner as in the conventional case, the implementation is easy. Therefore, the mold can be processed and improved after the occurrence of a defect such as burr. (3) Since there is no need to make changes on the mold clamping device side, no extra cost is required for implementation.

[Brief description of the drawings]

FIG. 1 is a side view showing a first embodiment of an injection molding die according to the present invention in a partial cross section.

FIG. 2 is a sectional view taken along line BB in FIG.

FIG. 3 is a view showing a second embodiment of an injection mold according to the present invention in correspondence with FIG. 2;

FIG. 4 is a side view showing a third embodiment of the injection molding die according to the present invention in a partial cross section.

FIG. 5 is a side view showing an example of a mold clamping device in a conventional horizontal injection molding machine, particularly showing a mold open state thereof.

FIG. 6 is a sectional view taken along line AA in FIG.

FIG. 7 is a side view showing a mold clamping state of the mold clamping device shown in FIG. 5;

FIG. 8 is an exaggerated perspective view showing a state where bending deformation has occurred in the fixed platen and the fixed mold.

FIG. 9 is a side view showing another example of the conventional injection molding machine, particularly showing a state in which the mold clamping device is in a mold open state.

[Explanation of symbols]

 15 Tie bar 60 Mold plate 70, 70 ', 80 Injection mold 71, 71', 81 Mold body 71a, 81a Joining surface 71c, 71c ', 82 Force transmitting unit 71d, 71d' Mounting surface 72 Mold mounting plate 73 Bolts (Hexagon socket head bolts) 75, 85 Molded product forming space 76 Clamper c Removal thickness

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Minoru Otsuka 1F, Takamichi, Iwazuka-cho, Nakamura-ku, Nagoya-shi, Aichi F-term in Nagoya Research Laboratory, Mitsubishi Heavy Industries, Ltd. 4F202 AM33 CA11 CB01 CL01 CL50

Claims (7)

[Claims] 1. A mold body having a molded product forming concave or convex portion for forming a molded product forming space at a joining surface at one end, and having an area larger than a joining surface of the mold body. An injection mold comprising: a mold mounting plate connected to the other end surface of the mold body by bolts; a projection surface of the other end surface of the space for forming a molded product in a mold-clamping direction. A mold for injection molding, wherein the mold is brought into contact with the mold mounting plate via a portion corresponding to the above. 2. A portion of the other end surface of the mold body corresponding to a projection surface of the molded product forming space in the mold clamping direction is substantially equal to a projected surface of the molded product forming space in the mold clamping direction. The injection mold according to claim 1, wherein the mold is formed to be slightly smaller. 3. A removal processing portion is formed by removing a peripheral edge portion of the other end surface of the mold main body by an appropriate thickness, thereby forming the molded product substantially at the center of the other end surface of the mold main body. The injection mold according to claim 1 or 2, wherein a force transmitting portion as a portion corresponding to a projection surface of the forming space in the mold clamping direction is provided. 4. The injection molding according to claim 3, wherein the mold body is formed in a horizontally long shape, and the removal processing portion is provided only at both lateral ends of the mold body. Mold. 5. The injection device according to claim 1, wherein the force transmitting portion is formed by attaching a steel plate having an appropriate thickness to a center portion of the other end surface of the mold body. Mold for molding. 6. The force transmitting portion is formed by attaching a steel plate having an appropriate thickness to a portion of the mounting surface of the mold mounting plate corresponding to a projection surface of the space for forming a molded product in a mold clamping direction. The injection mold according to claim 1 or 2, wherein: 7. The projecting height of the force transmitting portion is set to 0.2 to 0.5.
The injection mold according to any one of claims 3 to 6, wherein the diameter is 5 mm.