JPS62103109A - Synthetic resin molding die - Google Patents

Abstract

PURPOSE:To obtain a molding whose surface is smooth and dimensional accuracy is good, by a method wherein a plurality of auxiliary supports which are expandable and contractable in the direction meeting at right angles with a main support is provided centering round a part wherein though sufficient compression rigidity for transmitting pressure loading from a pressure plate to a molding plate is possessed along with fixation of both ends respectively to the molding plate and pressure plate, bending rigidity is lower than that of the main support and the molding plate is fixed to the main support. CONSTITUTION:A mold is clamped after a glass fiber mat has been mounted on a molding plate 18 of a bottom force 12. Then resin is cast and heating of the mold is performed by flowing high-temperature oil through a passage 28 formed on the molding plates 16, 18. With this construction, though the temperature of the molding plates 16, 18 is increased and heat expansion is generated, while a main support 24 does not bend in the direction meeting at right angles with a pressurizing direction as the main support 24 has been made higher in bending rigidity, an auxiliary support 26 is bent easily. Therefore, as it becomes that the molding plates 16, 18 can be expanded in a radial direction centering round a part wherein the main support 24 has been fixed and binding force in the direction of heat expansion hardly apply to the molding plates 16, 18, there is no possibility that the surface forming a cavity 14 of the molding plates 16, 18 is wrinkled or warped.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a synthetic resin mold, in particular,
This invention relates to a mold used for molding synthetic resin that involves heating.

Conventional technology Synthetic resin molding molds include an upper mold and a lower mold, and both of the upper mold and the lower mold have a molding plate that forms a cavity and a molding plate that is spaced a certain distance behind the molding plate. The press plate is arranged substantially parallel to the molded plate, and the frame body is provided between the molded plates and the pressure plate and transmits the pressure applied to the pressure plate to the molded plate. There is something. 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 When such a mold is used to mold a synthetic resin (hereinafter simply referred to as resin) that involves heating, the temperature change of the molding plate is caused by the temperature change of the pressure plate and frame. However, since the peripheral part of the molded plate is restrained by a member with high bending rigidity, Expansion in this direction is hindered, which causes a waving phenomenon in which wrinkles form on the cavity surface, causing unevenness on the surface of the molded product, and problems such as the molded plate being warped as a whole and the dimensional accuracy of the molded product becoming poor. Ta.

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

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

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, making it possible to produce molded products with smooth surfaces and good dimensional accuracy. Obtainable.

In addition, the main struts are designed to have high bending rigidity, so
This effectively prevents relative movement between the molding plate and the pressure plate in the direction parallel to the plate surface due to imbalance in the cavity internal pressure or external force, and also prevents the main support from moving the cavity of the molding plate in both the upper and lower molds. It is fixed at approximately the center of the part to be formed, and the molding plates of each mold expand and contract to the same extent in the same direction, so there is no misalignment of the molding plates of the upper and lower molds due to thermal expansion, and the molding plate of each mold is always fixed. It is possible to obtain molded products with high precision.

Embodiments Hereinafter, two or three embodiments of the present invention will be described in detail with reference to the drawings.

Fig. 1 shows a synthetic resin molding mold that is an embodiment of the present invention, and this mold is attached to a resin injection machine (not shown) to mold resin molded products of reinforced materials such as glass fibers. It is used. In the figure, 10 is an upper mold, and 12 is a lower mold, and these upper mold 10 and lower mold 12 each have molding plates 16 and 18 that form the cavity 14, and a certain distance behind these molding plates 16 and 18. Pressure plates 20.22 are spaced apart and arranged in parallel, and both ends are fixed to the molding plate 16.18 and the pressure plate 20.22, respectively, so that the pressing force applied to the pressure plate 20.22 is transferred to the molding plate 16.22. It consists of one main strut 24 and a plurality of sub struts 26 that transmit information to the main strut 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. One of the pressurizing plates 20 and 22 of the lower mold 12 is attached to a movable platen of the resin injection machine, and the other one is attached to a fixed platen, and the pressure plates 20 and 22 are opened and closed.

The main support 24 is a hollow member having a rectangular cross section and is made of shaped steel.
．． It has sufficient compressive rigidity and high bending rigidity to transmit the pressurizing force to 18. One end thereof is fixed approximately at right angles to the surface of the molding plate 16, 18 at approximately the center of the portion forming the cavity 14, and the other end is attached to the pressure plate 20.
．． It is fixed at 22. 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 a molded plate 1
8 in the same direction and by the same amount, and the mutually opposing portions of the molded plates 16 and 18 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+ nm.
It has sufficient compressive rigidity to transmit the pressurizing force to the main strut 24, but its bending rigidity is significantly lower than that of the main strut 24, and the deformation of the molded plate 16.18 under the mold clamping force of 6 kg/cIa is suppressed to an allowable range. The lattice points are arranged at intervals of about 10 CI11 so as to obtain the lattice points.

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 resin 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/cIa, and the mold is heated by flowing hot oil through passages 28 formed in the molding plates 16 and 18. This causes thermal expansion to occur as the temperature of the molded plates 16 and 18 rises, but since the main struts 24 have high bending rigidity, they will not bend in a direction perpendicular to the pressing direction. On the other hand, the sub-pillar 26 is easily bent 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. The surfaces of the molded plates 16 and 18 that form the cavities 14 are not 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 is supported by a member with high bending rigidity and thermal expansion is restricted, the thickness error in the molded product is ±1.0 mm. According to the mold of the example, ±0.4 mm is sufficient. Then, during cooling, the molding plate 16.18 is placed in the third position.
As shown by the arrow in the figure, it contracts toward its center, and the sub-pillar 28 also returns to its original state.

In addition, since the forming plates 16 and 18 are each fixed to the pressure plate 20 and 22 by the main struts 24 with high bending rigidity, there is an imbalance in the cavity internal pressure (for example, the height of the side wall of a container-shaped product is different on the left and right sides). The re-forming plate 16.18 does not move relative to the pressure plate 20.22 in the direction parallel to the plate surface due to external forces or external forces.
Since the thermal expansion of 18 also occurs by the same amount in the same direction centering on the portion fixed to the main support 24, dimensional accuracy does not deteriorate in the side wall portion of the container-shaped product.

Furthermore, 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.

In addition, if the sub-pillar 26 is made into a round bar as in the above embodiment,
Although it is advantageous in that there is no directionality in bending rigidity and there is no need to consider the orientation of the arrangement, it may be in the form of an elongated flat plate as shown in FIG.

The plate thickness and length of this sub-pillar 32 are such that, like the sub-pillar 26, the pressure applied to the pressure plate 20.
．． Although the spacing is the same as that of the sub-pillars 26, the plate surface is perpendicular to the straight line extending radially from the main column 24, as shown in Fig. 5. It has the advantage of being fixed in a posture that is difficult to buckle and easy to bend. The main support 34 is larger than the main support 24 and has a larger inner space, and is fixed to the center of the molded plate 16 forming the cavity 14, and has a resin injection port 34 inside. is provided.

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 mold returning to its original state. 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 1--2 in FIG. 10; Upper mold 12: Lower mold 14; Cavity 16.18: Molding plate 20.22
: Pressure plate 24: Main column 26: Sub-column 28: Passage 30: Resin injection port 32: Sub-column 34: Main column 36: Resin injection port Applicant Tatsu Todoroki, Director of the Agency of Industrial Science and Technology Figure 1

Claims (4)

[Claims] (1) An upper mold and a lower mold are provided, and both the upper mold and the lower mold are arranged approximately parallel to a molding plate that forms a cavity and a certain distance behind the molding plate. a main support having high compression rigidity and bending rigidity, one end of which is fixed substantially at right angles to the center of the portion of the molded plate forming the cavity, and the other end of which is fixed to the pressure plate; It is arranged approximately parallel to the main column around the main column, both ends are fixed to the forming plate and the pressure plate, respectively, and has sufficient compressive rigidity to transmit the pressurizing force from the pressure plate to the forming plate. A synthetic resin molding die comprising a plurality of sub-posts that have lower bending rigidity than the main support and allow the molded plate to expand and contract in a direction perpendicular to the main support around a portion fixed to the main support. (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) The synthetic resin molding die according to claim 1 or 2, wherein the sub-support pillar is a round bar. (4) The sub-support strut has 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. The synthetic resin mold according to item 2.