JPH08142145A - Injection mold and injection compression molding method using the same - Google Patents

Abstract

PURPOSE: To provide resin molded product reduced in molding strain by enabling molding due to an injection compression molding method without generating burr on a runner even if a mold having a runner is used. CONSTITUTION: In an injection compression molding method preliminarily performing injection in a slight mold opening state and performing mold clamping operation on the way of injection or after the completion of injection, a three-plate injection mold having a structure applying force to a fixed template 2 so as not to open the fixed template 2 and a fixed attaching plate 3 at the time of the slight mold opening state between a movable template 1 and the fixed template 2 and at the time of injection is used to obtain a molded product reduced in molding strain.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a mold used in an injection compression molding method and an injection compression molding method using the same.

[0002]

2. Description of the Related Art There are two types of injection molds.
There are plate mold and 3 plate mold. The two-plate mold is divided into a stationary mold plate and a movable mold plate at a parting line. The fixed side template has sprue and the parting surface has runners, gates, and cavities. The resin material is injected into the cavity through the sprue, runner and gate.

In the three-plate mold, a runner is arranged on another plane different from the parting surface on which the cavity is processed, and each time the mold is opened, this surface is opened and the runner is taken out. The resin material is distributed to the runner through the sprue and injected into the cavity through the pin gate.

The characteristic of the three-plate mold is that the position of the gate can be arbitrarily selected, so that the gate can be arranged at an ideal position in consideration of the flow of the resin material, and in the case of a multi-cavity mold, the gate is located at the center of the molded product. It is possible to dispose them, and since a pin gate can be adopted, it is possible to make the gate into a small size and eliminate the need for the gate processing of the gate.

Conventionally, disks such as compact disks and laser disks have been molded by the following injection compression molding method. That is, in the injection compression molding method,
As shown in FIG. 4, the concave portion 11 of the fixed-side template 11 on the right side of the drawing
A cavity 16 having a shape of a molded product is provided by a and the convex portion 12a of the left movable mold plate 12. The outer peripheral surface of the movable convex portion 12a and the inner side of the fixed concave portion 11a are sliding surfaces. A gate 15 is opened in the cavity 16. There is no runner in such a simple disk mold.

A resin material is injected into the cavity 16 through the sprue 13 and the gate 15 with the movable side mold plate 12 being separated from the fixed side mold plate 11 side by a predetermined amount. Next, movable side template 1
2 is moved to the fixed-side mold plate 11 to clamp the mold, and the resin material 17 in the cavity 16 is compressed (see FIG. 5). After the resin material has cooled, the mold is opened and the molded product is taken out to obtain an annular disk. The disc formed by this injection compression molding method has a small molding strain.

[0007]

Since the injection compression molding method is a molding method with a small molding strain, it is conceivable to mold a resin molded product having a complicated shape by the injection compression molding method like a disk.

However, in the case of a molded product having a complicated shape, the gate position must be determined in consideration of the flow of the resin material, and therefore, unlike the disc, the mold requires a runner for connecting the sprue and the gate. In addition, a runner is also required in the case of multiple production.

The problems that occur when the injection compression molding method is performed using a mold having a runner will be described below with reference to FIGS. 6 and 7.

In the case of a two-plate mold, since the mold is opened at the time of injection in injection compression molding, the runner 14 has a flash 1
9 occurs, the mold cannot be completely clamped, and the resin material 17 in the cavity cannot be sufficiently compressed (see FIG. 6).

In the case of a three plate mold, the cavity 16
Before the resin material is filled in, the space between the fixed-side mold plate 11 and the fixed-side mounting plate 18 is opened by the resin pressure, and the cavity 16 is not filled with the resin material. Even if the cavity 16 is filled with the resin material, burrs 19 are generated in the runner 14 to damage the mold.

Therefore, when the shape of a molded product requiring a runner in the mold is complicated or when a large number of molds are taken, it is impossible to use the injection compression molding method for providing a molded product with a small molding strain.

An object of the present invention is to provide a resin molded product having a small molding strain, which enables molding by an injection compression molding method without causing flash in the runner even in a mold having a runner. .

[0014]

In order to achieve the above object, a force is applied to a fixed-side mold plate in a three-plate mold even when the parting surface on which the cavity is processed is slightly opened. A mold for injection molding having a structure in which the fixed-side mold plate and the fixed-side mounting plate do not open when the resin material is injected is used for injection compression molding.

That is, the gist of the present invention is that the movable side mold plate 1 and the fixed side mold are used in the injection compression molding method in which injection is performed in advance from a slight mold opening state and the mold clamping operation is performed during or after the injection. For 3-plate injection molding of a structure in which a force is applied to the fixed-side mold plate 2 so that the space between the fixed-side mold plate 2 and the fixed-side mounting plate 3 does not open when the molds are slightly opened and when the mold is injected. It is in a mold and an injection compression molding method using it.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will be given below with reference to FIGS. The resin molded product is a plate with a slightly complicated shape. An explanation will be given using an injection molding die for molding this plate.

FIG. 1 is a sectional view of the mold, showing a slight mold opening state immediately before injection. FIG. 2 is a plan view of the movable side template. The movable mold plate 1 has a movable block 4 and a spring 5 that applies a force so that the fixed mold plate 2 and the fixed mounting plate 3 do not open when the mold is slightly opened. In FIG. 2, eight sets of springs and movable blocks are used.
And the spring coefficient are determined so that the force applied to the fixed-side template 2 via the movable block 4 is larger than (runner projected area × resin pressure).

A molding example in injection compression molding will be described with reference to FIGS. Polymethylmethacrylate resin was used as the resin material. The space between the movable mold plate 1 and the fixed mold plate 2 is slightly opened, and the resin material 10 is injected. FIG. 1 is a diagram immediately before injection of a resin material. In this state, since the movable block 4 exerts a force on the fixed-side mold plate 2, even if the resin material is injected, the fixed-side mold plate 2 and the fixed-side mounting plate 3
Since there is no opening between the cavity and the runner, it is possible to fill the cavity with the resin material without generating flash in the runner.

A mold clamping operation is performed during injection, and the cavity 9
The resin material 10 inside is compressed. Since the runner 7 has no flash, the resin material 10 can be reliably compressed.

Clamping is performed during or after the injection of the resin material 10. The mold clamping force at this time is (cavity 9
(Projected area x resin pressure + force of spring 5)). As the mold is clamped, the spring 5 contracts and the movable block 4 is stored in the movable mold plate 1.

After cooling is completed, the mold is opened and the molded product is taken out. When the molded product is taken out, the sprue and runner are separated from the molded product. Since the molded product is molded by the injection compression molding method, the molding strain is small.

The present invention is not limited to the above embodiment, but may be embodied as follows.

(1) The spring and the movable block may not be attached to the movable template, but may be attached to the fixed template.

(2) Instead of a spring, a hydraulic mechanism may be used as a means for applying a force to the fixed mold plate.

(3) The movable block may be arranged so as to frame the cavity.

(4) As the resin material, a general thermoplastic resin such as polymethylmethacrylate resin, ABS, polystyrene, and PC can be used.

[0027]

Since a mold having a runner can be molded by the injection compression molding method, a resin molded product having a small molding distortion can be obtained even when the molded product has a complicated shape or a large number of molded products are obtained. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a mold of the present invention, showing a slight mold opening state before injection of a resin material.

FIG. 2 is a plan view of a movable side template.

FIG. 3 is a cross-sectional view of the mold of the present invention in a state in which the resin material is completely injected from the state of FIG. 1 and the mold is clamped.

FIG. 4 is a cross-sectional view of a mold used for conventional injection compression molding, showing a slight mold open state before injection of a resin material.

5 is a cross-sectional view of the mold in a state where the resin material is completely injected and the mold is clamped from the state of FIG.

FIG. 6 is a cross-sectional view of a mold on the way of injection when an injection compression molding method is performed in a conventional two-plate mold.

FIG. 7 is a cross-sectional view of a mold during injection when an injection compression molding method is performed in a conventional three-plate mold.

[Explanation of symbols]

 1 movable side template 2 fixed side template 3 fixed side mounting plate 4 movable block 5 spring 6 sprue 7 runner 8 gate 9 cavity 10 resin material 11 fixed side template 12 movable side template 13 sprue 14 runner 15 gate 16 cavity 17 Resin material 18 Fixed side mounting plate 19 Burr

Claims (2)

[Claims] 1. A slight mold between a movable mold plate 1 and a fixed mold plate 2 in an injection compression molding method in which injection is performed in advance from a slight mold opening state and a mold clamping operation is performed during or after injection. A three-plate injection molding mold having a structure in which a force is applied to the fixed-side mold plate 2 so that the space between the fixed-side mold plate 2 and the fixed-side mounting plate 3 does not open in the open state and during injection. 2. An injection compression molding method using the injection molding die according to claim 1.