JPH06328535A - Method for injection compression molding and mold for injection compression molding - Google Patents

Abstract

PURPOSE:To provide molds for injection compression molding wherein a reinforcing fiber can be prevented from breaking at a gate part of the molds and sink marks and strain of a molded item in the neighborhood of the gate part are prevented from occurring. CONSTITUTION:Molds 1 and 2 for injection compression molding can be positioned at a slightly opened position A and a completely closed position B. In addition, a molded item part 4, a gate part 5 opening the molded item part 4 and a runner part 6 which is communicated with the gate part 5 and can be connected with a nozzle part 3 of an injection molding machine are provided. A freely switchable dividing means 7 separating the molded item part 4 and the runner part 6 is provided in this gate part 5 to shut the influences of cooling, back-flow, etc., of a molding material in a gate part 5 with a large cross-section of a path for the material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection compression molding method and an injection compression molding die suitably used for a molding material containing reinforcing fibers such as glass fibers and carbon fibers.

[0002]

2. Description of the Related Art The mechanical properties of a molded product made of a molding material containing reinforcing fibers such as glass fibers and carbon fibers have a strong correlation with the state of the reinforcing fibers in the molded product. That is, the longer the reinforcing fiber, the higher the mechanical strength.

Needless to say, the length of the reinforcing fiber in the molded product is related to the fiber length when mixed in the molding material.
Since it breaks during molding, it is also related to the molding method. A compression molding method is a molding method that minimizes breakage of reinforcing fibers. However, the compression molding method has drawbacks in that the accuracy of measuring the molding material is poor and molding of a complicated shape cannot be performed.
In contrast to this compression molding method, the injection molding method has good weighing accuracy and can mold a complicated shape. However, in the injection molding method, breakage of the reinforcing fiber is unavoidable as follows.

First, there is breakage due to the shearing effect in the screw portion of the injection molding machine. Second, there is a breakage due to a sudden change in pressure due to the molding material from the runner portion being squeezed at the gate portion that opens to the molded portion of the mold. Third,
There is breakage due to a sudden change in pressure when the molding material is press-fitted into the molded product part of the mold. The following measures are adopted as measures against breakage of the reinforcing fiber due to these factors.

With respect to the first factor, there is one that adopts a screw design modified so that large shear does not act. The second factor is that the material passage cross-sectional area in the gate portion is increased. As for the third factor, the mold is opened a little before injection to enlarge the space of the molded product part, and immediately after the injection of the molding material, the mold is closed to perform compression molding to the space of the regular molded product part. There is one that adopts the injection compression molding method. By these measures, it became possible to prevent the breakage of the reinforcing fiber to some extent even by the injection molding method.

[0006]

However, if this injection compression molding method is adopted and the cross-sectional area of the material passage in the gate portion is increased, the amount of molding material accumulated in the gate portion increases, and the molding product portion communicating with the gate portion is formed. The continuous part becomes thicker. Therefore, when the molding material of the gate portion cools and shrinks, the molding material of the molded product portion is pulled, and there is a problem that a sink mark, a distortion, or the like occurs in the vicinity of the gate portion opening of the molded product. Therefore, if the cross-sectional area of the material passage in the gate portion is reduced, the above-mentioned breakage of the reinforcing fiber occurs, and the mechanical strength of the molded product decreases.

The present invention has been made in view of such problems of the prior art, and an object thereof is to prevent breakage of the reinforcing fiber at the gate portion of the mold,
Another object of the present invention is to provide an injection compression molding method and an injection compression molding die that can prevent sink marks and distortion of a molded product near the gate portion.

[0008]

According to an injection compression molding method for solving the above-mentioned problems, a mold which can be opened and closed is opened a little, and a molding material containing a reinforcing fiber is molded into a molding part from a nozzle part of an injection molding machine. After injection through the runner part and gate part of
This is a method in which the mold is closed and compression molding is performed in a state where the molded product part and the runner part of the mold are separated.

The injection compression molding die can take a slightly opened open position and a fully closed position, and has a molded product part, a gate part opened to the molded product part, and the gate part. It has a runner portion to which a nozzle portion of a communication injection molding machine can be connected, and the gate portion is provided with openable and closable partitioning means for separating the molded product portion and the runner portion.

[0010]

[Operation] At the time of injection, if the mold is opened a little and the partition means is opened, the runner portion and the gate portion having a material cross section large enough to prevent breakage of the reinforcing fiber are opened, The molding material is introduced into the molded part where the volume is increased. In the compression process where injection is completed and the mold is fully closed, if the gate part is closed by the partitioning means and the molded product part and runner part are separated, cooling or backflow of the molding material in the gate part with a large material passage cross section will occur. The influence of the above is cut off from the molded part.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. First, a mold used in the injection compression molding method of the present invention will be described with reference to FIG. 1, and then the injection compression molding method will be described with reference to FIG.

In FIG. 1, 1 is a fixed mold, 2 is a movable mold, 3 is a nozzle part of an injection molding machine, 4 is a molded product part, 5 is a gate part, and 6 is a runner part.

The movable mold 2 can be pressed against the fixed mold 1 by the pressure cylinder 11, and the balance cylinder 12 having a larger force than the pressure cylinder 11.
Can be stopped in the open position A, which is slightly open, and by the controlled stroke of the balancing cylinder 12, the fully closed position B
Can be gradually closed until.

Between the movable mold 2 and the fixed mold 1, a molded product part 4 and a gate part 5 opening to the molded product part 4 are molded. Further, the fixed mold 1 has a gate portion 5
Is provided with a runner portion 6, and the inlet of the runner portion 6 is a receiving portion 6a to which the nozzle portion 3 can be connected.

A shut-off valve 7 (partitioning means) is provided at a portion corresponding to the gate portion 5 of the movable mold 2. The shut-off valve 7 is driven by a cylinder 13 so as to be able to advance and retreat, and its tip end 7a abuts a portion corresponding to the gate portion 5 of the fixed mold 1 to close the gate portion 5 or retract as shown. The gate part 5 can be opened. Further, the shutoff valve 7 is provided at the opening position of the gate portion 5 facing the molded product portion 4.

Next, the injection compression molding method using the above-mentioned mold will be described with reference to FIG. In FIG. 1A, the movable mold 2 is in an open position where it is slightly open, and a molded product 4 having a large space volume is formed. At this time, the shutoff valve 7 is retracted, and the gate portion 5 is open. In this state, the nozzle portion 3 of the injection molding machine abuts on the runner portion 6 to inject the molding material M as shown in the figure, and passes through the runner portion 6 and the gate portion 5 to the molding product portion 4 in a predetermined amount. Is filled. Here, the material passage cross-sectional area of the gate portion 5 has a space width equal to or longer than the length of the reinforcing fiber, and when the material passes, the reinforcing fiber can smoothly flow without a sudden change in pressure. .

In FIG. 2B, when the injection is completed,
The shut-off valve 7 advances and closes the gate part 5.
The shut-off valve 7 is provided at the opening position of the gate portion 5, and the side surface 7 b of the shut-off valve 7 is a portion that partitions the molded product portion 4. That is, the molded product part 4 is separated from the gate part 5 and becomes an independent space.

In FIG. 1C, the movable mold 2 is gradually pressed toward the fixed mold 1, and the molding material M is compressed and spreads in the molded product portion 4 to a predetermined shape. It is cooled and solidified. At this time, the shut-off valve 7 is retracted with the gate portion 5 closed, and the independent space of the molded product portion 4 is maintained. Therefore, the effect of cooling and solidifying the material in the gate portion 5 does not affect the molded product portion 4, and even when the material passage cross-sectional area of the gate portion 5 is large, the molded product is free from sink marks and distortion. Further, backflow of material from the molded product portion 4 to the gate portion 5 during compression molding is also prevented.

Since the gate part 5 is formed between the fixed mold 1 and the movable mold 2, the gate part 5 becomes large at the open position where the molds 1 and 2 are slightly open, and the mold 1 , 2 is completely closed in the fully closed position, the gate portion 5 is also small, which is advantageous, but the gate portion 5 is provided independently of the fixed mold 1 and the shut-off valve 7 is provided on the fixed mold 1 side. You can also Further, the shut-off valve 7 is not limited to being provided at the opening position of the gate portion 5 with respect to the molded product portion 4, but may be provided in the middle of the gate portion 5.

Further, an example of the present invention will be specifically described. Polypropylene containing glass fiber having a length of 13 mm is used as a reinforcing fiber in the molding material, and the gate portion 5 is 13 mm × 3.
A molded product having a 0 mm square cross section was obtained in the manner shown in FIG.
When checking the molded product, the remaining fiber length is about 10 mm
No sink mark or distortion was found in the vicinity of the opening of the gate portion.

[0021]

INDUSTRIAL APPLICABILITY In the injection compression molding method and the injection compression molding die of the present invention, a gate portion having a material passage cross section that is large enough to prevent breakage of the reinforcing fibers is provided, so that a rapid change in pressure occurs in the passing molding material. It does not occur, and the reinforcing fiber in the gate portion can reduce breakage. Further, when entering the compression molding step, the gate portion is closed and the molded product portion is separated, so that sinking or distortion of the molded product due to the cooling and solidification of the material accumulated in the gate portion is prevented.

Further, if the gate portion is closed during the compression molding process, the molded product portion becomes an independent space, the backflow of the material to the runner portion through the gate portion is prevented, and the predetermined molding is performed with the predetermined material. It becomes possible and is particularly suitable for molding a thin product.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of an injection molding die of the present invention.

FIG. 2 is an operation diagram showing an injection compression molding method of the present invention.

[Explanation of symbols]

 1, 2 Mold 3 Nozzle part 4 Molded product part 5 Gate part 6 Runner part 7 Shut-off valve (partitioning means)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuya Tanaka 2-3-1, Niihama, Arai-cho, Takasago, Hyogo Prefecture Takasago Works, Kobe Steel, Ltd. (72) Takeshi Nagaoka 2-chome, Niihama, Arai-cho, Takasago, Hyogo Prefecture No. 1 Kobe Steel Works, Takasago Works (72) Inventor Takao Yumoto 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Kobe Steel Works, Kobe Research Laboratory

Claims (4)

[Claims] 1. A mold which is openable and closable is slightly opened, and a molding material containing reinforced fibers is injected into the molded product part from a nozzle part of an injection molding machine through a runner part and a gate part of the mold. In the injection compression molding method of closing and compression molding, the compression molding is performed in a state in which the molded product part and the runner part of the mold are separated. 2. The injection compression molding method according to claim 1, wherein a cross section of the material passage of the gate portion at the time of injection has a space width equal to or larger than the length of the reinforcing fiber. 3. A molded product part, a gate part that opens to the molded product part, and a runner part that is in communication with the gate part and is connectable to a nozzle part of an injection molding machine. An injection compression molding die capable of being in a fully closed position, characterized in that the gate portion is provided with a partition means that separates a molded product portion and a runner portion from each other and can be opened and closed. Type. 4. The injection compression molding mold according to claim 3, wherein the partitioning means is provided at an opening position of the gate portion with respect to a molded product portion.