JP2000052384A - Injection molding die for molded product with undercut and undercut processing method for injection molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the necessity of post-processing after injection molding by releasing even a through-hole on a plate-shaped section disposed upright on a section forming an undercut after injection molding. SOLUTION: A recessed face section 44 forming an undercut is formed, and a plate-shaped section 45 with a through-hole 46 is disposed in upright on the recessed face 44 in the undercut processing method of an injection molded product, and a mold face forming the recessed face 44 is formed dividedly by molds 7 and 8 respectively forming at least the surface and the back of the plate-shaped section 45, and a protrusion 11 forming the through-hole 46 of the plate-shaped section 45 is formed on one mold 8, and after the recessed face 44 of a molded product 40 is separated from the other mold 7, one mold 8 is moved relatively to the direction of disposing in upright of the plate-shaped section 45 of the molded product 40 to release forcibly the protrusion 11 from the through-hole 46.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for injection molding of a molded article having an undercut, and a method of treating an injection molded article with an undercut.

[0002]

2. Description of the Related Art In many cases, resin molded products such as automobile bumpers have an undercut which hinders release from a molding die. For example, the vehicle bumper 40 shown in FIGS. 4 and 5 has a front wall portion 41, left and right side wall portions 42, and a rear piece 43 extending inward from the rear edge of the side wall portion 42 to the left and right. Due to the presence of the rear piece 43, the inner surface of the side wall portion 42 becomes a concave surface 44, and forms an undercut.

As a molding die capable of undercutting a molded product having such an undercut, a mold provided with a slide core using an angular pin is typical.

FIG. 6 schematically shows a conventional example of an injection mold having a slide core. The mold includes a fixed mold 51 and a movable mold 52, and these molds 51 are provided. , 5
The molten resin is injected into a cavity formed by clamping the mold 2 and cooled and solidified to obtain a molded product having a predetermined shape.

The fixed mold 51 is fixedly mounted on a fixed mounting plate 53. An injection head is provided at an appropriate position of the mold 52, and a molten resin is supplied to the cavity 54 through a sprue, a runner and a gate. It is configured to be able to fill the inside.

The movable mold 52 has a slide core 56 slidable in the left-right direction along a guide rail 55. The slide core 56 is moved right and left by a conventionally known angular pin (not shown) as the mold is opened. It is configured to move inward. Reference numeral 57 denotes an ejector plate (projection plate) to which an ejector pin (not shown) is attached, and reference numeral 58 denotes a stripper plate.

[0007] The step of releasing the molded article formed by the conventional injection mold is as shown in FIG. That is, as shown in FIG. 7A, the movable mold 52 is opened, and the molded product 40 is released from the fixed mold surface. next,
As shown in FIG. 7B, the slide core 56 is slid left and right inward so that the side wall portion 4 serving as an undercut portion is formed.
The undercut process is performed by separating the mold surface of the slide core 55 from the concave portion 44 of the inner surface 2.
After the completion of the undercut processing (see FIG. 7C),
The molded product 40 is projected upward by the ejector pin.

[0008]

On the inner surface (concave portion 44) of the side wall portion 42, which is an undercut portion, a mounting piece 45 (plate-like portion) for mounting on a mounting bracket on the vehicle body side is provided upright. If a through hole 46 for screw attachment is formed in the hole 45 and this through hole 46 is formed at the time of injection molding, the through hole 46 becomes an undercut for the sliding operation of the slide core 56 and cannot be released. Therefore, the above-described through hole 46 is finished by post-processing after injection molding.

However, such post-processing complicates a production line, lowers productivity, and causes an increase in production cost. Therefore, the present invention enables the through-hole of the plate-shaped portion erected in a portion to be an undercut to be released after being formed by injection molding, thereby eliminating the need for post-processing after injection molding. The purpose is to:

[0010]

Means for Solving the Problems In order to solve the above problems, the present invention has taken the following technical means. That is, the injection molding die of a molded product having an undercut according to the present invention is an injection molding die of a molded product in which a plate-shaped portion having a through hole is provided upright in an undercut region. The mold surface forming one side of the portion is provided on a slide mold which is relatively movable with respect to the mold surface forming the other side, and is preferably slidable in the standing direction of the plate-like portion. In this case, a convex portion forming a through hole of the portion is provided.

According to the present invention, even when the plate-shaped portion is provided in the undercut region, the molded product can be released from the mold as described below, and without post-processing after injection molding. The through hole of the plate-shaped portion can be formed at the time of injection molding.

That is, to release a molded product, first,
A mold having a mold surface forming the other side surface of the plate portion is separated from the undercut region of the molded product. Then, by moving the slide mold in a direction away from the molded product, the protrusion provided on the slide mold is forcibly removed from the through-hole of the plate-shaped part and released.

Therefore, even when a plate-shaped portion having a through hole serving as a secondary undercut is provided upright in the undercut region, for example, the concave portion, the molding die of the present invention does not need to be provided. Since the mold can be released, it is not necessary to perform post-processing for forming a through hole after the mold is released, so that the production line is simplified and the cost is reduced.

In the above molding die, a portion of the side surface of the projection provided on the slide die, which is pressed against the inner surface of the through hole when the slide die is slid in a direction away from the molded product, has a draft. It is preferable to form it in a tapered shape. According to this configuration, when the slide die is separated from the concave surface portion, the plate-shaped portion smoothly comes off from the convex portion along the side surface of the tapered convex portion, and excessive stress is generated in the plate-shaped portion. This prevents the plate-shaped portion from being damaged at the time of release.

In the molding die, the first slide die is reciprocally mounted on the die mounting plate, and is disposed on the edge of the molded product, and is engaged with the edge of the molded product. Second
Is disposed adjacent to the first slide die, and is provided so as to be reciprocable in the direction in which the plate-shaped portion is erected with respect to the die mounting plate, and is further urged in a direction for returning the first slide die. Connecting means for connecting the first slide mold and the second slide mold so as to be disconnected when a return force equal to or more than a predetermined force acts on the first slide mold, and a second slide. And a driving unit for driving the mold.

In the molding die according to the present invention, when the second slide die is moved by the driving means against the urging force of the spring, the second slide die is locked to the edge of the molded product. Therefore, the edge portion of the molded product is protruded by the second slide die, so that the molded product can be undercut. At this time, the first slide die is connected to the second slide die by the connecting means, and the first slide die slides along with the protrusion of the edge of the molded product. The provided protrusion does not hinder the above-described undercut processing.
When the undercut processing is completed, a biasing force enough to release the connection by the connecting means is accumulated in the spring, so that the first slide mold is returned by the spring, and the protrusion is formed. Can be forcibly removed from the through hole and released.

Further, the plate-like portion is erected on the concave portion of the molded product to be undercut, and the edge side of the mold surface forming the convex portion on the back side of the concave portion is plate-like with respect to the mold mounting plate. The third slide type is reciprocated in the standing direction of the unit, and the second slide type is linked to the operation of the third slide type, thereby forming the second slide type driving means. be able to.

As described above, if the slide mold has a three-part construction, one part of the third slide mold has a structure in which the undercut is pulled out by a cylinder by forcible removal, and one part of the second slide mold is the third slide mold. A stopper is installed so as to be integrated with the slide mold when the amount of undercut is delayed, and the other first slide mold has a slide mechanism supported by a spring to slide in the return direction after the undercut processing. A molded product having a plate-like portion having a through hole in an undercut region can be released, and further, the first and second slide dies can be reciprocated by moving the third slide die back and forth. Since the slide operation is performed integrally, the number of drive devices such as cylinders is reduced, simplifying the overall structure, and assembling ease of the molding die. Maintainability also becomes good.

Further, the present invention relates to an undercut treatment method for an injection-molded article having a concave portion serving as an undercut and a plate-like portion having a through-hole formed in the concave portion. The mold surface that forms the part is divided by at least the molds that form the front and back surfaces of the plate-shaped part, and one of the molds is provided with a convex part that forms a through-hole in the plate-shaped part. After the concave portion of the mold is separated from the other mold, the mold is forcibly removed from the through hole by moving one mold relative to the molded product, for example, in the direction in which the plate-shaped portion is erected. It is characterized by the following.

According to the method for undercut treatment of an injection-molded article of the present invention, even if the molded article has a through-hole formed in a plate-like portion provided upright in the undercut portion, the through-hole is injected. The molded article can be released after being formed at the same time as molding.

Further, the injection-molded article of the present invention has a concave portion serving as an undercut, and a plate-like portion having a through hole is erected on the concave portion, and a base end of the plate-like portion is provided. On one side surface, a concave groove extending in the plate width direction is formed.

As described above, if a concave groove is provided on one side surface of the base end of the plate-shaped portion provided upright in the undercut portion, the through hole provided in the plate-shaped portion can be formed by injection molding. ,
After that, when the slide mold for forming the concave portion serving as the undercut is slid so as to separate from the concave portion, the base end of the plate portion is relatively easily bent, and the forcible release of the plate portion is performed. It is performed smoothly.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an injection mold 1 according to a first embodiment of the present invention.
The fixed mold 2 and the movable mold 3 are provided, and a cavity 4 formed by clamping these molds 2 and 3 is provided.
A molten resin is injected into the inside, cooled and solidified to form a resin molded product having a predetermined shape, for example, an automobile bumper 4 shown in FIGS. 4 and 5.
0 is obtained.

The bumper 40 has a front wall portion 41, left and right side wall portions 42, and a rear piece 43 extending left and right inward from a rear end edge of the side wall portion 42. The inner surface of the side wall portion 42 becomes the concave surface 44, and forms an undercut. That is, almost the entire inner surface of the side wall portion 42 is an undercut region. On the inner surface (concave surface 44) of the side wall portion 42, which is an undercut area of the bumper 40, a mounting piece 45 (plate-like portion) extending inward in the left and right directions is provided substantially vertically. , A through hole 46 for screw attachment is provided.

The illustrated molding die 1 is configured such that the front side of the bumper 40 is molded on the upper side of the cavity 4 and the rear side of the bumper 40 is molded on the lower side of the cavity 4. In the illustrated example, the fixed mold 2 is a female mold and the movable mold 3 is a male mold. However, the fixed mold may be a male mold and the movable mold may be a female mold, depending on the shape of the molded product and other factors. . In the illustrated example, the fixed mold 2 and the movable mold 3 are arranged vertically, and the movable mold 3 is configured to be movable in the vertical direction with respect to the fixed mold 2. However, the fixed mold and the movable mold 3 are arranged left and right. hand,
The movable mold can be configured to be movable left and right. In addition, one or a plurality of plate-like portions 45 can be provided at appropriate positions of the molded product 40.

The fixed mold 2 is mounted and fixed to a fixed side mounting plate 5. An injection head is provided at an appropriate position of the mold 2, and molten resin is injected into the cavity 4 through a sprue, a runner and a gate. It is configured to be able to be filled.

The movable mold 3 has a core mold 7 fixed to the movable-side mounting plate 6 and a first slide mold 8 and a second slide mold 9 arranged corresponding to each plate-like portion 45. And a third slide die 10.

The first slide die 8 has a die surface constituting the rear side surface (the lower side in FIG. 1) of the plate-like portion 45,
On the mold surface, a convex portion 11 forming a through hole 46 is provided. The mold surface forming the front side surface of the plate portion 45 is provided in the core mold 7. Therefore, the mold surface forming the inner surface of the side wall portion 42 of the bumper 40 is divided by the core mold 4 on the front side of the plate portion 45 and by the first slide mold 8 on the rear side of the plate portion 45. . In other words,
The mold surface forming the concave portion 44 serving as the undercut is divided by the respective molds 7 and 8 located on the front and back of the plate-like portion 45. Thus, the first slide die 8 is disposed on the rear end side of the molded product 40.

Of the side surfaces of the convex portion 11 provided on the first slide die 8, the die surface of the first slide die 8 (the left and right outer surfaces in the illustrated example) that forms the concave surface portion 44 serving as an undercut area of the molded product 40. The portion (the inner left and right sides in the illustrated example) pressed against the inner surface of the through hole 46 when the slider is slid in the direction away from the molded product 40 (in the illustrated example, left and right outwards) is formed in a tapered shape with a draft angle. I have. Further, on the mold surface forming one side surface of the plate-shaped portion 45, a ridge 19 forming a concave groove extending in the plate width direction is provided on one side surface of the base end portion of the plate-shaped portion 45.

The first slide die 8 is provided on the movable mold mounting plate 6 so as to be slidable in the direction in which the plate-shaped portion 11 stands, that is, in the illustrated example, in the left-right direction. More specifically, the first slide die 8 is provided so as to be able to reciprocate left and right outward from a return position (see FIGS. 1, 2A and 2B) constituting the cavity 4.

A first slide die 8 is provided on the mounting plate 6 side.
A gas spring 12 for urging the gas spring in the return direction is provided. The distal end of the piston rod of this gas spring 12 is in contact with the first slide die 8,
The gas springs 12 are compressed as they move outward in the left and right directions, so that an urging force corresponding to the sliding amount is accumulated.

The second slide die 9 is disposed adjacent to the first slide die 8 and has a die surface forming a rear end surface of the bumper 40. Is locked to the rear end edge of the bumper 40 injection-molded in the cavity 4.

The second slide die 9 is provided with a movable mounting plate 6.
Are provided so as to be able to reciprocate in the left-right direction. The mold 9 includes a flat plate portion 9a on which the third slide die 10 is placed, an outer end erected portion 9b erected upward from left and right outer ends of the flat plate portion 9a, and left and right sides of the flat plate portion 9a. And an inner end erected portion 9c erected upward from the inner end. The horizontal distance between the inner end standing portion 9c and the outer end standing portion 9b is
The width of the third slide die 10 is larger than the width in the left-right direction. The upper end of the inner end standing portion 9c constitutes a mold surface forming the rear end surface of the bumper 40.

The third slide die 10 is mounted on the second slide die 9 and connected to a piston rod 14 of a drive cylinder 13 provided on the movable die 6 side. To move the piston rod 14 in the left-right direction, so that the third slide type 10
Can reciprocate in the left-right direction with respect to the mounting plate 6.

The outer end standing portion 9b of the second slide die 9 and the contact portion of the third slide die 10 with the standing portion 9b are spaced by the amount of undercut processing. As shown in FIG. 2 (b), the slide die 10 is forcibly removed to the left and right outwards and released, and after the undercut processing is completed, the second slide die 9 is integrated with the third slide die 10 to move the right and left outwards. Is to be moved to. As described above, the operation of the third slide die 10 driven by the cylinder 13 is the second
A driving means for driving the second slide mold is formed by linking the slide molds.

The first slide die 8 and the second slide die 9 are connected to the third slide die 10 such that the connection is released when a return force greater than a predetermined force by the spring 11 acts on the first slide die 8. Connecting member 15 (connecting means)
Is installed. Specifically, the connecting member 15 includes a support shaft 16 provided on the third slide die 10 so as to protrude downward.
And is urged downward by a spring (not shown) interposed between the connecting member 15 and the third slide die 10. The connecting member 15 is fitted into a recess 17 extending in the left-right direction formed on the upper surface of the first slide die 8. It should be noted that the second slide mold 9 has a third slide mold 10
A long hole 18 in which the connecting member 15 is slidably provided in the left and right direction is formed so as not to hinder the delay operation of the second slide die 9 with respect to the second slide die 9.

The connecting member 15 is connected to the second slide mold 9.
When the first slide die 8 and the third slide die 10 slide together (see FIG. 2B), the first and second slide die 8 are brought into contact with the left and right outer ends of the recess 17. The slide dies 9 and 10 are integrally slid.
The contact surfaces of the connecting member 15 and the concave portion 17 are formed in a tapered shape, thereby forming a cam that pushes the connecting member 15 upward against the urging force of the spring. Therefore, when the gas spring 12 is compressed and an urging force equal to or greater than a predetermined force is accumulated, the return force of the first slide die 8 by the gas spring 12 is increased by the connecting member 1.
The connecting member 15 is pushed up by overcoming the urging force of the spring for urging the connecting member 5 downward, whereby the connecting member 15 is disengaged from the concave portion 17 and the first slide die 8 and the second slide die 9
Is disconnected, and the first slide die 8 is vigorously returned by the gas spring 12.

FIG. 2 shows a step of releasing the molded product 40 from the injection molding die according to the first embodiment. FIG.
In the state before the mold opening shown in (a), first, the movable mold 3 is opened from the fixed mold 2 to release the molded article 40 from the mold surface of the fixed mold 2.

Next, when the third slide mold 10 is pulled out by the cylinder 13, the first and second slide molds 8 and 9 do not slide at the initial stage of the operation, and only the third slide mold 10 is a molded product. The mold 40 is forcibly removed from the mold (see FIG. 2B).

When the third slide die 10 comes into contact with the outer end standing portion 9b of the second slide die 9, the first and second slide die 8, 9 are integrated with the third slide die 10. Will slide. By such a delay operation,
The third slide mold 10 constituting the edge side of the mold surface forming the convex surface portion on the back surface side of the concave surface portion to be undercut
Prior to the operation of the slide die 8 and the second slide die 9, it can be moved by an understroke amount.

When the cylinder 15 is further pulled out, the first, second, and third slide dies 8, 9, and 10 integrally slide right and left outward, and the end of the molded article 40 is moved by the second slide dies 8. The edge is pulled out left and right, and the inner surface (concave surface 44) of the molded product 40 is the core mold 7 (the other mold).
(See FIG. 2C). At this time,
The gas spring 12 in contact with the outer end of the first slide die 8 is gradually compressed, and the urging force corresponding to the sliding amount of the first slide die 8 is accumulated.

When the urging force of the gas spring 12 increases, the connecting member 15 is pushed up by the cam to release the connection between the first slide die 8 and the second slide die 9. 8 is returned.

Then, the first slide die 8 is separated from the concave surface portion 44 of the molded product 40, and the tip of the plate-like portion 45 is bent upward to deform the protrusion 11 from the through hole 46. The undercut processing is completed (FIG. 2
(D)).

Thereafter, the molded product 4 is ejected by an ejector pin or the like.
The molded article 40 may be taken out by projecting 0 upward.

FIG. 3 shows an injection mold according to a second embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted. The operation and effect will be described.

In this embodiment, the connecting member 15 is
Through hole 2 provided in flat plate portion 9a of second slide die 9
A spring (not shown) for urging the connecting member 15 downward is interposed between the connecting member 15 and the third slide die 10.
That is, the connecting member 15 is not integrally formed with the third slide mold 10.

The concave portion 17 provided in the first slide die 8 has a shape substantially along the outer surface on the lower side of the connecting member 15, and unless the connecting member 15 is pushed upward, the first concave portion 17 is formed.
The slide die 8 and the second slide die 9 are connected so as to slide integrally.

The present invention is not limited to the above embodiment, and the design can be changed as appropriate. For example, the through-hole may be a long hole or a C-shaped notched through-hole.

[0049]

According to the injection mold and the undercut treatment method of the present invention, an undercut through-hole can be formed, and the molded product can be released from the mold. As a result, the production line can be simplified.

Further, according to the injection molded product of the present invention, when the protrusion of the slide die is forcibly removed from the through hole of the molded product formed by the above-described injection molding die and released, the plate-shaped portion is removed. The base end can be easily bent, and the release can be facilitated, and the plate-shaped portion can be prevented from being damaged during release.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view schematically showing an injection mold according to a first embodiment of the present invention.

FIG. 2 shows a step of releasing a molded article from the injection molding die. FIG. 2 (a) is an enlarged vertical sectional view of a main part showing a state before injection molding and opening of the mold, and FIG. FIG. 3C is an enlarged vertical sectional view of a main part showing a state where the first, second and third slide dies have been integrally slid and an undercut processing of a concave part has been performed. (D) is an enlarged longitudinal sectional view of a main part showing a state in which the first slide die is returned and the protrusion of the first slide die is forcibly removed from the through-hole of the plate-like portion and released.

FIG. 3 is an enlarged longitudinal sectional view of a main part of an injection molding die according to a second embodiment of the present invention.

FIG. 4 is an enlarged perspective view of a main part of an automobile bumper as an example of an injection molded product having an undercut.

FIG. 5 is a sectional view taken along line AA of FIG. 4;

FIG. 6 is a longitudinal sectional view showing a conventional slide core type injection mold.

FIG. 7 is an operation explanatory view of a conventional injection molding die,
(A) is a vertical cross-sectional view in which the mold is opened, (b) is a vertical cross-sectional view in which the slide core is moved to perform an undercut process, and (c) is a vertical cross-sectional view in which the undercut process is completed. FIG.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 injection molding die 7 die forming surface of plate-shaped portion 8 die forming back surface of plate-shaped portion, first slide die, slide die having die surface forming one side surface of plate-shaped portion 9th 2 slide mold 10 third slide mold 11 convex part forming a through-hole 12 spring 13 drive cylinder driving third slide mold 15 coupling means 40 injection molded product 44 concave part serving as undercut 45 plate-shaped part 46 penetration Hole

Claims (5)

[Claims] 1. A mold for injection molding of a molded product having a plate-shaped portion having a through-hole in an undercut region, wherein a mold surface forming one side of the plate-shaped portion has another side. A molded product having an undercut, wherein the molded product has an undercut, which is provided on a slide die that is relatively movable with respect to a die surface to be formed, wherein the slide die is provided with a convex portion that forms a through hole of the plate-shaped portion. Mold for injection molding. 2. The side surface of the projection provided on the slide mold,
The molding having an undercut according to claim 1, wherein a portion pressed against the inner surface of the through hole when the slide die is slid in a direction away from the undercut region of the molded product is formed in a tapered shape having a draft angle. For injection molding of products. 3. The second slide die is reciprocally mounted on a mold mounting plate, is disposed on the edge side of the molded product, and is engaged with the edge of the molded product. Is disposed adjacent to the first slide die, and is provided so as to be able to reciprocate in the direction in which the plate-shaped portion is erected with respect to the die mounting plate, and further returns the first slide die. A spring biasing in the direction, connecting means for connecting the first slide mold and the second slide mold such that the connection is released when a return force equal to or more than a predetermined force acts on the first slide mold; The mold for injection molding of a molded article having an undercut according to claim 1 or 2, further comprising a driving means for driving the second slide mold. 4. A plate-like portion is provided upright on a concave portion of a molded product to be an undercut, and an edge side of a mold surface forming a convex portion on the back surface side of the concave portion is positioned with respect to a mold mounting plate. A third slide type that reciprocates in the direction in which the plate-like portion stands upright, and the second slide type is linked to the operation of the third slide type, thereby driving the second slide type. The mold for injection molding of a molded article having an undercut according to claim 3, wherein 5. An undercut processing method for an injection-molded article having a concave portion serving as an undercut, and a plate-like portion having a through-hole formed in the concave portion, wherein the concave portion is formed. The mold surface is divided and configured by a mold that forms the front surface and the back surface of the plate portion, and one of the molds is provided with a convex portion that forms a through hole of the plate portion,
After the concave surface of the molded product is separated from the other mold, one of the dies is moved relative to the molded product to forcibly remove the projection from the through hole and release the molded product. Undercut processing method.