JP2004358886A - Method for molding resin molded product having hole, and mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for molding a molded product having a hole, constituted so as not only to reduce a hole cutting and forming process but also to reduce a production cost by performing the formation of a hole and gate cutting at the same time while forming the resin molded product having good appearance. <P>SOLUTION: In the method for molding the resin molded product having the hole, a ring-shaped protruded wall is provided on at least one of a first mold and a second mold, and a gate is provided on the protruded wall on the inner peripheral side thereof. The peripheral edge part of the hole is formed by allowing the protruded wall to approach the mold surface of the other mold, and gate cutting and the formation of the hole are performed at the same time. Further, the mold for molding the resin molded product having the hole is constituted so that the ring-shaped protruded wall is provided on at least one of the first and second molds and the gate for injecting a molten resin is provided on the protruded wall on the inner pheripheral side thereof of either one of the first and second molds on the inner pheripheral side thereof. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a molding method and a molding die for a resin molded product, and more particularly to a molding method and a molding die for molding a resin molded product having holes by injection press molding.
[0002]
[Prior art]
Various types of resin molded products having holes are known. For example, a fuel tank is provided with holes for disposing a fuel pump or the like.
[0003]
Conventionally, molding of a resin molded product having such a hole has been generally performed by forming a main body by blow molding and then cutting off the hole.
[0004]
However, when the holes are formed by cutting, since cutting is generally performed manually, there is a problem in that a manufacturing loss occurs due to a variation in cutting accuracy and a manufacturing cost is increased. In addition, there is a problem that the manufacturing cost is increased because the number of steps is increased due to the necessity of the cutting step, and a special device for cutting is required.
[0005]
Furthermore, when forming using blow molding, for example, when forming a resin molded product having an uneven shape, it is difficult to form the thickness to be constant, so it is necessary to perform molding by a method such as injection press molding. Has been proposed.
[0006]
Here, when a resin molded product is formed by injection press molding, a molten resin remains in a portion to be a gate at the time of injection, and the molten resin is cooled and solidified to form a gate portion. Therefore, in order to improve the shape of the obtained resin molded product, it is necessary to perform a so-called gate cut for cutting the gate portion. For this reason, there is a problem that the number of manufacturing steps is further increased due to the gate cut and the manufacturing cost is increased, and a problem that a trace of the gate portion remains on the surface of the resin molded product. For this reason, a method of performing gate cutting simultaneously with molding has been developed (for example, Patent Document 1).
[0007]
According to the method described in Patent Literature 1, a gate is provided in a traveling path of a forming die (hereinafter, referred to as a moving die) that proceeds in a pressing step, so that a gate is cut by the moving die. Therefore, molding and gate cutting can be performed simultaneously.
[0008]
However, according to the method described in Patent Literature 1, it is necessary to arrange the position of the gate on the side wall that is the end of the mold. For this reason, for example, when molding a large molded product, it becomes difficult to spread the resin to the end farthest from the end where the gate is disposed in the molding die, and a short shot or the like occurs. There's a problem.
[0009]
On the other hand, a method has been developed in which holes are pressed and cut during a press step of injection press forming (for example, Patent Document 2). According to the method described in Patent Document 2, it is possible to form a hole at the same time as shaping, but a protrusion for forming the hole is arranged in the cavity, and the molten resin removes the protrusion. Once it is divided into two parts to surround it, it flows so that it joins. At this time, since the molten resin joins in a state where the surface temperature is slightly lowered, there is a problem in that weld is generated in the obtained resin molded product. Further, the increase in the number of steps and the generation of a trace of the gate caused by performing the gate cut after the molding have not been solved by this method.
[0010]
Further, a method has been developed in which a gate is provided in a molding die (hereinafter, referred to as a fixed die) which does not proceed in a press step of injection press molding, and a hole is formed and a gate cut is simultaneously formed in the press step. (For example, Patent Document 3). The injection press molding method described in Patent Document 3 is a method in which a gate is provided in a fixed mold and a gate cutter is provided in a movable mold, and is a method for manufacturing a small disk molded product. However, according to the method described in Patent Literature 3, the gate cutter is provided so as to operate independently of the movable die, and the pressing process includes a process of performing a movable press and a process of performing a gate cut. Since the process is performed in two steps, there is a problem that a molding die to be used is complicated, and there is also a problem that a manufacturing cost is increased.
[0011]
[Patent Document 1]
JP 2000-108180 A
[Patent Document 2]
JP 05-269805 A
[Patent Document 3]
JP 2002-018918 A
[0012]
[Problems to be solved by the invention]
The present invention has been made in consideration of the above circumstances, and reduces or reduces the number of steps of cutting and forming holes, and simultaneously performs the formation of holes and gate cutting to reduce the cost required for manufacturing. An object of the present invention is to provide a method and a mold for forming a resin molded article having holes, which form a resin molded article having an appearance.
[0013]
[Means for Solving the Problems]
The method for molding a resin molded article having holes according to the present invention for solving the above-mentioned problems is a method for injection press-molding a resin molded article having holes communicating between a front surface and a back surface of a wall surface. An injection step of injecting a molten resin into a cavity formed by the mold and the second molding die; and a mold surface of at least one of the first molding die and the second molding die of the other molding die. A pressing step for moving in the direction, and at least one of the first mold and the second mold protrudes in the mold surface direction of the other mold at a position to be a peripheral portion of the hole. A ring-shaped projecting wall is provided, and a gate for injecting the molten resin is provided on one of the first mold and the second mold on an inner peripheral side of the projecting wall, and the pressing step is performed. The protruding wall is brought close to the mold surface of the other mold so that The edge is formed, characterized in that performing the formation of the gate cut the hole at the same time.
[0014]
According to this configuration, the hole can be formed by bringing the ring-shaped protruding wall close to the mold surface of the other mold, and the injection press molding and the hole can be simultaneously performed. Further, by providing a gate on the inner peripheral side of the protruding wall, a gate portion is formed on a portion located on the inner peripheral side of the protruding wall, which is a portion cut when forming a hole in the obtained molded product. This means that the gate can be cut at the same time when the hole is formed.
[0015]
In the method for molding a molded article having holes according to the present invention, it is preferable that the gate is provided in a molding die provided with the protruding wall, of the first molding die and the second molding die.
[0016]
Further, a mold for molding a resin molded article having a hole according to the present invention that solves the above-mentioned problem is an injection mold for injecting a molten resin into a cavity formed by a first mold and a second mold. A step of pressing at least one of the first mold and the second mold in the mold surface direction of the other mold by an injection press forming method. A molding die for molding a resin molded product having a hole communicating between a front surface and a back surface of a wall surface, the molding die having the first molding die and the second molding die disposed opposite to each other, At least one of the first mold and the second mold is provided with a ring-shaped projecting wall projecting in the direction of the mold surface of the other mold at a position to be a peripheral portion of the hole. A gate for injecting the molten resin is provided on the inner peripheral side of the protruding wall. And it is provided on either one of the first mold or the second mold.
[0017]
According to this configuration, the hole can be formed by the ring-shaped projecting wall, and the injection press molding and the formation of the hole can be performed simultaneously. Further, by providing the gate on the inner peripheral side of the protruding wall, the gate can be cut at the same time when the hole is formed.
[0018]
In the molding die for molding a molded product having a hole according to the present invention, the gate is provided on a molding die provided with the protruding wall among the first molding die and the second molding die. Is preferred.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
The method for molding a resin molded article having holes according to the present invention is a method for injection press molding a resin molded article having holes communicating between the front surface and the back surface of a wall surface.
[0020]
The molding method of the present invention can be applied to the molding of resin molded products having various holes irrespective of the shape and the like, for example, from a large one such as a resin tank for fuel to a small one such as a disk molded product. It can be used to form various types of resin molded products.
[0021]
The molding method of the present invention includes an injection step of injecting a molten resin into a cavity formed by a first molding die and a second molding die, and a step of forming the first molding die and the second molding die. A pressing step of causing at least one of them to advance in the direction of the mold surface of the other molding die.
[0022]
The first mold is a mold for forming either the front surface or the back surface of the wall surface. The second mold is a mold for forming a surface of the wall surface that is not formed by the first mold. The injection press molding in the present invention will be described below.
[0023]
First, a first molding die and a second molding die are arranged so as to face each other so as to be slightly apart from each other, and a cavity is formed from the molding surface of the first molding die and the molding surface of the second molding die. . Further, in addition to the first mold and the second mold, for example, a mold surface of another mold such as a slide core for forming an undercut shape may be a mold forming a cavity. You can also.
[0024]
Next, a predetermined amount of molten resin is injected into the cavity by an injection step. Next, at least one of the first mold and the second mold is advanced in the direction of the mold surface of the other mold by a pressing step. As the molding die advances, the cavity is compressed in the traveling direction of the molding die, and the molten resin injected into the cavity is filled in the entire cavity.
[0025]
In the molding method of the present invention, at least one of the first molding die and the second molding die is provided with a ring-shaped projecting wall projecting in the direction of the mold surface of the other molding die at a position to be a peripheral portion of the hole. In addition, a gate for injecting the molten resin to the inner peripheral side of the protruding wall is provided on one of the first molding die and the second molding die.
[0026]
The ring-shaped protruding wall serves as a mold surface for forming a hole portion of the resin molded product having a hole, and the protruding wall is brought close to the mold surface of the other molding die in a pressing step, thereby forming a peripheral portion of the hole. Can be formed. Here, the protruding wall may form all of the peripheral edge portion of the hole in the plate thickness direction, or may form a part in the plate thickness direction. In other words, when the protruding wall is brought close to the position in contact with the mold surface of the other molding die in the pressing step, the molten resin filled in the part on the inner peripheral side of the hole and the part on the outer peripheral side of the hole The filled molten resin is cut off by the protruding wall, and the entire peripheral portion of the hole in the thickness direction is formed. Therefore, in this case, a hole is formed by this pressing step. Also, in the pressing step, when the protruding wall is brought close to the mold surface of the other mold so as not to be in contact with the mold surface, the molten resin filled in the inner peripheral portion of the hole and the outer peripheral side of the hole are The filled molten resin is partially continuous at the gap between the projecting wall and the mold surface of the other mold. Therefore, in this case, in the pressing step, only a part of the peripheral portion of the hole in the thickness direction is formed. In this case, the portion formed by the protruding wall has a ring-shaped groove shape including the peripheral portion of the hole. Therefore, after the molten resin is cooled and solidified and the molded product is released from the mold, the hole can be easily formed manually as a guide groove for forming a hole by breaking or cutting the groove. This hole can be formed, for example, by manually breaking and removing the inner peripheral portion of the hole, or by cutting with a known cutting means such as a jig or a cutter. In any case, since the peripheral portion of the hole is positioned by the guide groove, the hole can be formed easily and with high precision without requiring a special device.
[0027]
Here, the fluidity of the molten resin is affected by the distance between the mold surfaces during injection (clearance). That is, if the clearance is large, the fluidity is high, and if the clearance is small, the fluidity is low. When the clearance is small and the fluidity is low, depending on other factors that affect the fluidity such as the melt viscosity of the resin material and the molding temperature, the molten resin may be placed in the cavity at a position relatively close to the gate in the cavity during the pressing process. May solidify. In this case, there is a case where the molten resin does not spread into the cavity and a resin product having a desired shape cannot be formed. Therefore, in the molding method of the present invention, it is preferable to control the clearance, that is, the distance between the protruding wall and the mold surface of the molding die facing the protruding wall in consideration of the fluidity of the molten resin in the cavity. For example, when the fluidity of the molten resin is low, a good molded product can be formed by setting the distance between the projecting wall and the mold surface of the molding die facing the projecting wall to be relatively large. . In the case where the flowability of the molten resin is high, the entire peripheral portion of the hole is formed by bringing the projecting wall close to a position in contact with the mold surface of the molding die facing the projecting wall. That is, the hole can be cut and formed by the protruding wall, and the hole can be formed simultaneously in the pressing step.
[0028]
In the molding method of the present invention, a gate for injecting the molten resin is provided on one of the first molding die and the second molding die on the inner peripheral side of the protruding wall. As a result, the gate portion to be formed is disposed on the inner peripheral side of the portion to be a hole in the resin molded product, and the gate portion is removed at the same time when the hole is formed. Can be formed simultaneously.
[0029]
Further, in the method for molding a resin molded article having holes according to the present invention, it is preferable that the gate and the protruding wall be provided in the same mold. Here, depending on the shape of the desired resin molded product, the type of the resin material used, and the like, the projection wall may slightly hinder the flow of the molten resin when the molten resin is injected into the cavity. Therefore, particularly when a large molded product is formed, since the flow distance of the molten resin is large, there is a possibility that a slight weld may occur in the obtained resin molded product due to the inhibition of the flow of the molten resin. . However, by providing the gate and the protruding wall in the same mold, the flow of the molten resin injected from the gate is less likely to be hindered by the protruding wall. Therefore, even when forming a large-sized resin molded product as described above, it is possible to more easily and reliably form a resin molded product having a good shape without weld.
[0030]
In the present invention, the width of the ring-shaped protruding wall in the ring radial direction can be large or small. For example, when the width dimension in the ring radial direction is small, it is suitable for performing high-precision cutting as a guide hole for guiding cutting by the above-described cutter. When the width in the radial direction of the ring is increased, the portion of the resin that is discarded when the hole is cut and formed can be minimized. For example, when a protruding wall is provided with a width dimension close to the gate, the gate portion is formed in the obtained resin molded product, but the portion on the inner peripheral side of the hole is not formed or is extremely formed. It is only formed to be thin. Therefore, only the gate portion needs to be substantially discarded at the time of forming the hole, so that the cost required for the material can be reduced.
[0031]
Further, depending on the desired shape of the resin molded product, the material of the molten resin, the fluidity of the molten resin depending on the molding temperature, etc., it is also possible to provide the protruding walls on both the first molding die and the second molding die. . In this case, the two protruding walls come close to each other in the pressing step, and guide grooves are formed on both the front and back surfaces of the resin molded product. Therefore, the hole can be cut and formed more easily and suitably.
[0032]
In the molding method of the present invention, the flow of the molten resin is performed from the inner peripheral side to the outer peripheral side of the protruding wall by disposing the gate on the inner peripheral side of the protruding wall. Therefore, since the flow of the molten resin is not hindered by the protruding wall or is performed in a direction substantially perpendicular to the protruding wall, unlike the case where the molten resin flows so as to merge once after branching, the occurrence of weld is prevented. You. It is preferable that the inner wall surface of the protruding wall be formed in a tapered shape inclined toward the center. By forming the tapered shape, the shape of the protruding wall can be made to be a shape that does not hinder the flow of the molten resin, and the flow of the molten resin can be made more favorable, so that a more favorable shape is formed. An article can be formed.
[0033]
A molding die for molding a resin molded product having a hole according to the present invention includes: an injection step of injecting a molten resin into a cavity formed by a first molding die and a second molding die; A press step of advancing at least one of the molding die and the second molding die in the direction of the mold surface of the other molding die. This is a molding die for molding a resin molded product having a hole communicating with.
[0034]
The mold of the present invention is a mold used in the above-described molding method of the present invention. Therefore, the molding die of the present invention can be used to form various resin molded products as described above.
[0035]
A molding die for molding a resin molded product having a hole according to the present invention includes the first molding die and the second molding die arranged to face each other.
[0036]
A cavity is formed by the mold surface of the first molding die, the second molding die, or another molding die, and the molten resin is injected into the cavity by the injection step in the same manner as in the molding method described above. A resin molded product having holes is formed by an injection press molding method.
[0037]
Either one or both of the first mold and the second mold are connected to the driving means so as to be able to advance and retreat in the direction of another mold.
[0038]
In the molding die for a resin molded product having a hole according to the present invention, at least one of the first molding die and the second molding die has a surface of the other molding die at a position to be a peripheral portion of the hole. A ring-shaped protruding wall protruding in the direction is provided, and a gate for injecting the molten resin is provided on one of the first molding die and the second molding die on the inner peripheral side of the protruding wall. I have.
[0039]
In the molding die of the present invention, similarly to the molding method described above, one or both of the first molding die and the second molding die are provided with a ring-shaped projecting wall, and the projecting wall forms a resin molded product. Part or all of the peripheral edge of the hole in the thickness direction is formed. Further, since a gate for injecting the molten resin is provided on the inner peripheral side of the ring-shaped protruding wall, the gate cut and the formation of the hole can be performed at the same time. It is possible to perform well.
[0040]
Furthermore, it is preferable to provide the gate and the protruding wall in the same mold as in the molding method described above. In this case, similarly to the above, the flow of the molten resin injected from the gate is further prevented from being hindered by the protruding wall, and it is possible to easily and reliably form a resin molded product having a good shape without weld. Become.
[0041]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0042]
(Example 1)
Example 1 of the present invention is an example of a method of molding a resin molded article having a hole, and is a method of performing molding by bringing a protruding wall close to and slightly away from a mold surface of a first molding die in a pressing step. is there. FIG. 1 is a schematic cross-sectional view of a resin molded product having holes formed by the molding method of the first embodiment, and FIGS. 2 to 6 are schematic diagrams illustrating the molding method of the second embodiment.
[0043]
The method for molding a resin molded article having holes according to the first embodiment is a method for molding a fuel tank 3 having an upper shell 1 and a lower shell 2 formed separately. A hole 6 for arranging a fuel pump (not shown) is formed in the upper wall portion 5 of the upper shell 1, and the upper shell 1 and the lower shell 2 are welded and integrated by a known hot plate welding. Since the lower shell 2 does not have the holes 6, it can be formed by ordinary injection press molding. Since the upper shell 1 has the holes 6, the method of the present invention for forming a resin molded article having holes is used. Molded. The method of manufacturing a resin molded product having holes according to the first embodiment is performed as follows.
[0044]
First, as shown in FIG. 2, a first molding die 7 and a second molding die 8 are arranged to face each other, and a mold surface 10 of the first molding die 7 and a mold surface of the second molding die 8 are arranged. 11 and a cavity 12 is formed. At this time, the first mold 7 and the second mold 8 are arranged so as to be slightly separated from each other.
[0045]
The first molding die 7 is a molding die for molding the surface 13 of the upper shell 1, and includes a mold surface 17 for forming an inner peripheral side 16 of the peripheral edge 15 of the hole 6 of the upper shell 1 and a peripheral edge of the hole 6. The mold surface 20 for forming the outer peripheral side 18 of 15 is a surface that is continuous without any step. The first molding die 7 is connected to driving means (not shown), and is a movable die that advances in the direction of the second molding die 8 in a pressing step described later.
[0046]
The second forming die 8 is a forming die for forming the back surface 21 of the upper shell 1, and has a ring-shaped projecting wall 22 formed at a position to be the peripheral portion 15 of the hole 6. The protruding wall 22 is formed such that the width dimension in the ring radial direction a is thin, and the inner wall 23 of the protruding wall 22 is formed in a tapered shape inclined toward the center. In addition, a gate 25 for injecting the molten resin is disposed substantially at the center of the inner peripheral side 16 of the ring-shaped protruding wall 22. The gate 25 is connected to a nozzle of an injection device (not shown) arranged toward the outside of the second mold 8.
[0047]
{Circle around (1)} Injection step: FIG. 3 is a diagram showing the injection step. The injection process of the first embodiment is performed by injecting the molten resin 28 injected from an injection device (not shown) into the cavity 12 through the gate 25. The molten resin 28 injected into the cavity 12 is injected into the gate 25 and a part of the cavity 12 in a substantially circular shape around the gate 25.
[0048]
{Circle around (2)} Pressing process; FIG. 4 is a diagram showing the pressing process. In the pressing step of the first embodiment, an injection device (not shown) is set in a pressurized state after the injection step. The pressing step is performed by clamping the first molding die 7 by a driving means (not shown) and moving the first molding die 7 in the direction of the mold surface 11 of the second molding die 8 (the direction of arrow b in the drawing). By this pressing step, the cavity 12 is reduced from the direction of the first mold 7 to the direction of the second mold 8, and the molten resin 28 injected into the cavity 12 is moved from the gate 25 to the end 30 of the cavity 12. Flowed and filled.
[0049]
At this time, the mold surface 10 of the first mold 7 approaches the protruding wall 22 provided on the mold surface 11 of the second mold 8. In the first embodiment, the distance between the protruding wall 22 and the mold surface 10 of the first molding die 7 was reduced to 0.3 mm by the pressing process. The protruding wall 22 serves as a mold surface for forming the peripheral portion 15 of the hole 6, and the portion of the molten resin 28 that contacts the outer wall 31 of the protruding wall 22 serves as the peripheral portion 15 of the hole 6. In the first embodiment, the protruding wall 22 is brought close to the mold surface 10 of the first molding die 7 in the pressing step, so that the obtained resin molded product has a ring corresponding to the shape of the protruding wall 22. A guide groove 32 is formed.
[0050]
{Circle around (3)} Solidification step: After the pressing step, the molten resin 28 is cooled and solidified by the first molding die 7 and the second molding die 8 and solidified after the first molding die 7 is opened. 35 was taken out to obtain a first molded body 36 of the upper shell 1 shown in FIG. At this time, the molten resin 28 remaining in the gate 25 is also solidified at the same time, so that the first molded body 36 has the gate portion 37 formed integrally with the upper shell 1. As described above, since the gate 25 is disposed on the inner peripheral side 16 of the ring-shaped protruding wall 22, the gate portion 37 is formed on the inner peripheral side 16 of the guide groove 33.
[0051]
(4) Cutting step: As shown in FIG. 6, a cutter knife 38 is inserted into the guide groove 32 of the first molded body 36 of the upper shell 1, and the inner peripheral side 16 of the guide groove 32 is manually formed. The hole 6 was formed by cutting and removing the pre-hole portion 40 which is the portion of the above, and the upper shell 1 was formed. At this time, since the gate portion 37 is formed on the inner peripheral side 16 of the guide groove 32 as described above, the gate portion 37 is integrated with the planned hole portion 40. Therefore, when cutting and removing the planned hole portion 40 in the cutting process, the gate portion 37 is also removed at the same time, and the formation of the hole 6 and the gate cutting are performed simultaneously.
[0052]
According to the method of molding a resin product having a hole according to the first embodiment, a part of the peripheral edge 15 of the hole 6 is formed in the pressing step by providing the ring-shaped projecting wall 22 in the second molding die 8. In addition, it is possible to easily form the cut of the hole 6 in the cutting step. At this time, since the hole 6 is cut and formed not by a special cutting means or a separately provided mold but by a normal cutter knife 38, the cost required for manufacturing is greatly reduced. Since the cutting step is performed along the guide groove 32 formed by the protruding wall 22, the precision of forming the hole 6 is extremely high.
[0053]
Further, by providing the gate 25 on the inner peripheral side 16 of the protruding wall 22, the gate can be cut at the same time when the hole 6 is formed. The product 35 can be easily obtained. Further, in the first embodiment, since the protruding wall 22 and the gate 25 are both provided in the second mold 8, the flow of the molten resin 28 in the injection step and the pressing step is hindered by the protruding wall 22. Is more reliably reduced. Since the gate 25 is provided on the inner peripheral side 16 of the protruding wall 22, the molten resin flows from the inner peripheral side 16 of the protruding wall 22 toward the outer peripheral side 18. Unlike the case of flowing while welding, the formation of weld is suppressed.
[0054]
(Example 2)
Example 2 of the present invention is an example of a molding die used for molding a resin molded article having holes. The molding die of the second embodiment is formed such that the protruding wall is in contact with the die surface of the first molding die in the pressing step. FIG. 7 is a schematic diagram showing a pressing step using the molding die of the second embodiment.
[0055]
The molding die 41 of the second embodiment has the same first molding die 42 as that of the first embodiment. The second molding die 43 has the same gate 45 as that of the first embodiment, and is formed so that the protruding wall 46 comes into contact with the die surface 47 of the first molding die 42 in the pressing step. Therefore, when injection press molding is performed using the molding die 41 of the second embodiment, the molten resin 52 disposed on the inner peripheral side 51 of the protruding wall 46 and the molten resin 52 disposed on the outer peripheral side 53 of the protruding wall 46 in the pressing step. The molten resin 52 is cut off by the ring-shaped projecting wall 46, and the entire peripheral portion 50 of the hole 48 is formed by the projecting wall 46. Therefore, when the molding die 41 of the second embodiment is used, in addition to the effect of the molding die described in the first embodiment, the formation of the hole 48 and the gate cutting are simultaneously performed by the pressing step, and the favorable shape is obtained. It is possible to easily form a resin molded product having the above holes.
[0056]
(Example 3)
Example 3 of the present invention is an example of a molding die used for molding a resin molded article having holes. The molding die of the third embodiment has the same shape as that of the first embodiment except that the thickness of the protruding wall in the ring radial direction is formed to be a thick width. FIG. 8 is a schematic diagram showing a pressing step using the molding die of the second embodiment.
[0057]
The molding die 55 of the third embodiment has the same first molding die 56 as that of the first embodiment. The second mold 57 has the same gate 58 as in the first embodiment, and is formed in the same manner as in the first embodiment except for the protruding wall 60. In the third embodiment, the thickness of the protruding wall 60 in the ring radial direction c is formed so as to be close to the gate 58. Therefore, when performing the injection press molding using the molding die 55 of the third embodiment, the inner peripheral side 63 of the hole is formed in the pressing step in addition to the effect of the molding die 55 described in the first embodiment. The mold surface 64 is almost entirely occupied by the protruding wall 60, and the obtained resin molded product only needs to discard the gate portion 65. Therefore, the cost of the material can be reduced. It becomes possible. Further, in this case, the pre-hole portion 66 formed on the inner peripheral side 63 of the hole is very thin. For this reason, the cutting process can be performed by holding the gate portion 65 by hand and squeezing the gate portion 65 and the planned hole portion 66, and the cutting process can be performed more easily and accurately.
[0058]
【The invention's effect】
As described above, according to the method for manufacturing a resin molded product having holes according to the present invention, it is necessary to reduce or reduce the number of steps of forming holes, and to separately prepare a special cutting device and a cutting die. In addition, the cost required for manufacturing can be reduced by simultaneously performing the formation of the hole and the gate cut. Further, since the gate portion is formed on the inner peripheral side of the peripheral portion of the hole and cut at the same time as the hole is formed, it is possible to form a resin-formed product having a good appearance without gate marks with high precision and ease. Become. In addition, since molding can be performed without obstructing the flow of the molten resin, it is possible to form a resin molded product without weld.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a fuel tank formed by a molding method according to a first embodiment of the present invention.
FIG. 2 is a schematic view illustrating a molding method according to a first embodiment of the present invention.
FIG. 3 is a schematic view illustrating a molding method according to a first embodiment of the present invention.
FIG. 4 is a schematic view illustrating a molding method according to a first embodiment of the present invention.
FIG. 5 is a schematic view illustrating a molding method according to Example 1 of the present invention.
FIG. 6 is a schematic view illustrating a molding method according to Example 1 of the present invention.
FIG. 7 is a schematic diagram illustrating a pressing step using a mold according to Example 2 of the present invention.
FIG. 8 is a schematic diagram illustrating a pressing step using a mold according to a second embodiment of the present invention.
[Explanation of symbols]
1: Upper shell 2: Lower shell 3: Fuel tank 5: Upper wall portion of upper shell 6: Hole 7: First molding die 8: Second molding die 10: Mold surface 11 of first molding die 11: Second molding Mold surface 12: Cavity 13: Surface of upper shell 15: Peripheral portion of hole 16: Inner peripheral side 17: Mold surface 18 for forming inner peripheral side of peripheral portion 20: Outer peripheral side 20: Outer peripheral side of peripheral portion Mold surface for forming 21: Back surface of upper shell 22: Projecting wall a: Ring radial direction 23: Inner wall of projecting wall 25: Gate 28: Molten resin 30: End side of cavity 31: Outer wall of projecting wall 32: Guide groove 35 : Resin molded product 36: First molded body 37: Gate section 38: Cutter knife 40: Expected hole section
41: Mold 42: First Mold 43: Second Mold 45: Gate 46: Projecting Wall 47: Mold Surface of First Mold 48: Hole 50: Perimeter of Hole 51: Peripheral Peripheral side 52: Molten resin 53: Outer peripheral side of peripheral part
55: molding die 56: first molding die 57: second molding die 58: gate 60: projecting wall c: ring radial direction 63: inner peripheral side of hole 65: gate portion 66: scheduled hole portion

Claims (4)

A method for injection press-molding a resin molded product having a hole communicating the front surface and the back surface of the wall surface,
An injection step of injecting a molten resin into a cavity formed by the first mold and the second mold, and forming at least one of the first mold and the second mold into the other mold Press process to advance in the mold surface direction of the mold,
At least one of the first mold and the second mold has a ring-shaped projecting wall projecting in the direction of the mold surface of the other mold at a position to be a peripheral portion of the hole. A gate for injecting the molten resin is provided on one of the first mold and the second mold on an inner peripheral side of a wall,
Forming a peripheral portion of the hole by bringing the protruding wall close to the mold surface of the other mold in the pressing step, and simultaneously performing gate cutting and forming the hole; Molding method. The method of molding a molded article having holes according to claim 1, wherein the gate is provided on a molding die provided with the protruding wall, of the first molding die and the second molding die. An injection step of injecting a molten resin into a cavity formed by the first mold and the second mold, and forming at least one of the first mold and the second mold into the other mold A molding step for molding a resin molded product having a hole communicating with the front and back surfaces of the wall surface at a part of the wall surface by an injection press forming method having a pressing step of moving the mold in a mold surface direction. ,
Having the first mold and the second mold arranged to face each other,
At least one of the first mold and the second mold is provided with a ring-shaped projecting wall projecting in the direction of the mold surface of the other mold at a position to be a peripheral portion of the hole. A gate on the inner peripheral side of the protruding wall, wherein a gate for injecting the molten resin is provided in one of the first molding die and the second molding die. Mold for molding molded products. 4. The gate according to claim 3, wherein the gate is provided on a mold of the first mold and the second mold on which the protruding wall is provided. 5. Mold.

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