JPH0158048B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a mold for molding a synthetic resin, and particularly to a mold used for molding a synthetic resin that involves heating.

Conventional technology A synthetic resin mold has an upper mold and a lower mold.
Both of the upper mold and the lower mold include a molding plate forming a cavity, a pressure plate disposed behind the molding plate at a certain distance and almost parallel to the molding plate, and a pressurizing plate that is connected to the molding plate. Provided between the pressure plate,
Some are configured to include a frame body that transmits the pressure applied to the pressure plate to the forming plate. This frame body is supposed to have sufficient rigidity (compression rigidity) to transmit the above-mentioned pressing force, but members with high bending rigidity are provided especially around the mold, and the molded plate and Relative movement with the pressure plate in a direction parallel to the plate surface is prevented.

Problems to be solved by the invention These molds are made of synthetic resin (hereinafter referred to as
When used for molding (simply referred to as resin), the temperature change of the molding plate is larger than that of the pressure plate or frame, and the amount of thermal expansion is also large. is restrained by a member with high bending rigidity, which prevents the molded plate from expanding in the direction along the cavity-forming surface (cavity surface), which causes a waving phenomenon in which the cavity surface wrinkles, causing the molding to deteriorate. Irregularities may occur on the surface of the product,
There was a problem in that the molded plate was warped as a whole, resulting in poor dimensional accuracy of the molded product.

Means for Solving the Problems In order to solve the above-mentioned problems, the synthetic resin molding die according to the present invention has an upper mold and a lower mold that each include a molding plate forming a cavity and a molding plate for the molding plate. a pressure plate disposed substantially parallel to the molded plate at a certain distance behind the molded plate; A main column with high compression rigidity and bending rigidity is fixed to a pressure plate, and the main column is arranged almost parallel to the main column around the main column, and both ends are fixed to a forming plate and a pressure plate, respectively, and a forming plate is formed from the pressure plate. Although it has sufficient compressive rigidity to transmit pressure to the plate, its bending rigidity is lower than that of the main column, and the molded plate expands and contracts in a direction perpendicular to the main column around the part fixed to the main column. It is configured to consist of a plurality of sub-pillars that allow the support.

In addition, the expression "consisting of a forming plate, a pressure plate, a main column, and a sub-column" is used here because
This is to clarify that a frame with high bending rigidity is not provided around the mold as in the past, and that auxiliary parts that do not hinder the expansion and contraction of the molded plate in the direction parallel to the plate surface are used. It is not our intention to exclude installation.

Effects of the Invention As described above, in the synthetic resin molding die according to the present invention, the sub-struts allow the molded plate to expand and contract in the direction perpendicular to the main support, and the molded plate expands and contracts as it is heated. Because it can easily extend in the above direction during thermal expansion, the surface that forms the cavity will not wrinkle or the molded plate will warp as a whole, and the surface will be smooth and the molding will have good dimensional accuracy. You can get the goods.

In addition, since the main support is designed to have high bending rigidity, it effectively prevents relative movement between the forming plate and the pressure plate in the direction parallel to the plate surface due to imbalance of cavity internal pressure or external force. The support column is fixed approximately at the center of the cavity-forming part of the molded plate in both the upper and lower molds, and the molded plates of each mold expand and contract to the same extent in the same direction, so thermal expansion is prevented. As a result, there is no misalignment between the molding plates of the upper and lower molds, and molded products with high precision can always be obtained.

Embodiments Hereinafter, two or three embodiments of the present invention will be described in detail based on the drawings.

Fig. 1 shows a synthetic resin molding die that is an embodiment of the present invention, and this mold is attached to a resin injection machine (not shown) to form a resin molded product containing reinforcing material such as glass fiber. It is used for molding. In the figure, 10 is an upper mold, and 12 is a lower mold.
18, and pressure plates 20, 22 arranged in parallel behind the forming plates 16, 18 with a certain distance between them.
and the forming plates 16, 18 and the pressing plates 20, 22 at both ends.
It consists of one main support 24 and a plurality of sub-support pillars 26, which are fixed to the molding plates 16 and 18, respectively, and transmit the pressing force applied to the pressure plates 20 and 22 to the forming plates 16 and 18.

The molded plates 16 and 18 are both manufactured by electroforming nickel, and have a plurality of passages 28 formed therein that extend along the plate surface. A resin injection port 30 is further formed in the center of the molding plate 16 of the upper mold 10, and either one of the pressure plates 20 and 22 of the upper mold 10 and the lower mold 12 is connected to the movable platen of the resin injection and extraction machine. , the remaining one is attached to a fixed plate and can be opened and closed.

The main support 24 is a hollow member with a rectangular cross section formed of a section steel, and the pressure plates 20, 22
It has sufficient compressive rigidity and high bending rigidity to transmit pressing force from the molded plates 16 and 18 to the molded plates 16 and 18. One end thereof is fixed approximately at right angles to the surface of the molded plates 16, 18 at approximately the center of the portion forming the cavity 14, and the other end is attached to the pressurizing plates 20, 22.
is fixed. The main support 24 of the upper mold 10 is fixed at a position slightly away from the center of the molding plate 16 in order to avoid the resin injection port 30 provided at the center of the molding plate 16. The main support 24 is also fixed at a position offset from the center of the molded plate 18 by the same amount in the same direction, and the molded plates 16 and 18
The parts facing each other are firmly fixed.

In addition, the sub-pillar 26 is made of a round bar with a diameter of 10 mm and a length of 200 mm.
The molded plate 1 has sufficient compression rigidity to transmit the pressing force to the main support 18, but its bending rigidity is significantly lower than that of the main support ²⁴ .
Approximately 10 to keep the deformation of 6 and 18 within the allowable range.
They are arranged on grid points with cm spacing.

When molding a product made of a thermoplastic resin such as unsaturated polyester or epoxy resin reinforced with glass fiber using the mold configured as described above, first, the molding plate 18 of the lower mold 12 is After placing the glass fiber mat, the mold is closed. The mold can be heated to the curing temperature of the resin before injection, or the mold can be kept at a certain temperature lower than the curing temperature during resin injection and then heated to the curing temperature after injection. The resin is injected at a pressure of 5 to 10 kg/cm ² , and the mold is heated by flowing high-temperature oil through passages 28 formed in the molding plates 16 and 18. This causes the temperature of the molded plates 16 and 18 to rise and thermal expansion to occur.
Since the main strut 24 has high bending rigidity, it does not bend in a direction perpendicular to the direction of pressurization, whereas the auxiliary strut 26 easily bends as shown in an exaggerated manner in FIG. Therefore, the molded plate 16,
18 can expand in the radial direction centering on the part where the main support 24 is fixed as shown by the arrow in FIG. Molded plates 16, 18
The surface forming the cavity 14 will not be wrinkled or warped, and a molded product with a smooth surface and high dimensional accuracy can be obtained.
In conventional molds in which the periphery of the molded plate was supported by a member with high bending rigidity to restrict thermal expansion, the thickness error in the molded product was ±1.0 mm. According to the example mold, ±0.4mm
That's all there is to it. Then, during cooling, the forming plate 1
6 and 18 contract toward the center as shown by arrows in FIG. 3, and the sub-pillar 28 also returns to its original state.

Furthermore, since the molded plates 16 and 18 are fixed to the pressure plates 20 and 22, respectively, by the main struts 24 with high bending rigidity, there is an imbalance in the internal pressure of the cavity (for example, the height of the side wall of a container-shaped product is different from left to right). The molded plates 16 and 18 do not move relative to the pressure plates 20 and 22 in the direction parallel to the plate surfaces due to external forces (which occur when different cases occur) or external forces, and thermal expansion of both molded plates 16 and 18 is also prevented. Since the same amount is generated in the same direction around the portion fixed to the support column 24, the dimensional accuracy of the side wall of the container-shaped product will not deteriorate.

Further, since the main support 24 is provided adjacent to the resin injection port 30, the support rigidity is particularly high in the portion where the cavity internal pressure is high, and the occurrence of deflection of the molded plate 16 due to the cavity internal pressure is effectively prevented.

It should be noted that if the sub-pillar 26 is made of a round bar as in the above embodiment, it is advantageous in that there is no directionality in bending rigidity and there is no need to consider the installation direction. It may also be in the form of an elongated flat plate.
The plate thickness and length of this sub-post 32 are determined to have sufficient rigidity to transmit the pressure applied to the pressure plates 20, 22 to the forming plates 16, 18, similar to the sub-post 26. , the main columns 24 are at the same intervals as the secondary columns 26, but as shown in FIG.
The plate surface is fixed in a position perpendicular to a straight line extending radially from the plate, which has the advantage of being difficult to buckle and easy to bend. Moreover, the main support 34 is the main support 2
4 and has a wide inner space, and is fixed to the center of the portion of the molded plate 16 that forms the cavity 14, and is provided with a resin injection port 36 inside.

Although two embodiments of the present invention have been described above, the present invention can be implemented in various modifications and improvements based on the knowledge of those skilled in the art.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a synthetic resin molding die according to an embodiment of the present invention, cut at the center.
FIG. 2 is a diagram showing the expanded state of the mold during heating, and FIG. 3 is a diagram showing the expanded state of the mold returned to its original size. FIG. 4 is a front sectional view showing a resin molding mold according to another embodiment of the present invention, and FIG. 5 is a sectional view taken along the line VV in FIG. 4. 10: Upper mold, 12: Lower mold, 14: Cavity,
16, 18: Molding plate, 20, 22: Pressure plate, 2
4: Main pillar, 26: Secondary pillar, 28: Passage, 30:
Resin injection port, 32: Sub-prop, 34: Main post, 3
6: Resin injection port.

Claims (1)

[Scope of Claims] 1. An upper mold and a lower mold are provided, and both of the upper mold and the lower mold are arranged on a molding plate forming a cavity and approximately on the molding plate at a certain distance behind the molding plate. A pressure plate arranged in parallel, and a main body having high compression rigidity and bending rigidity, one end of which is fixed substantially at right angles to the center of the cavity-forming portion of the molded plate, and the other end fixed to the pressure plate. a column and a column arranged approximately parallel to the main column around the main column, fixed at both ends to the forming plate and the pressure plate, respectively, and having sufficient compressive rigidity to transmit pressing force from the pressure plate to the forming plate; but has lower bending rigidity than the main support, and a plurality of sub-support supports that allow the molded plate to expand and contract in a direction perpendicular to the main support around the part fixed to the main support. Molding mold. 2. The composition according to claim 1, wherein the molded plate has an internal passage along the plate surface, and can be heated and cooled by a heat medium flowing through the passage. Resin molding mold. 3. Claim 1, wherein the sub-support pillar is a round bar.
Synthetic resin molding mold according to item 1 or 2. 4. Claim 1 or 2, wherein the sub-support struts have an elongated flat plate shape, and each sub-support strut is arranged in a posture such that the plate surface is perpendicular to a straight line extending radially from the main support struts. Synthetic resin molding mold described in .