JPH01176537A - Undercut processing mechanism in mold for molding of resin - Google Patents

Abstract

PURPOSE:To prevent the abnormal action of a first slide core at a first stage, by preparing a plastic member which energizes between the first slide core and the second slide core in the direction to separate them each other. CONSTITUTION:When advancing a first slide core 30 by driving a hydraulic cylinder 15 after a mold break, the occurrence of abnormal action that a second side core 31 moves with the first slide core 30 together is prevented, because the second slide core is pushed in the direction opposite to the advancing of the first slide core. That is, the second slide core 31 stops at the original position, until the flange portion 35 of a connecting member 34 contacts to the stop 37 of the second slide core 31, and only after the flange portion 35 has contacted to the stop 37 of the second slide core 31, it advances with the first slide core 30 together. Therefore, there is no possibility that the second slide core 31 moves with the first slide core 30 together from the beginning and a molding is so much deformed that it causes a permanent deformation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an undercut treatment structure in a mold for resin molding.

[Prior Art] An example of a resin molded product including an undercut portion is an automobile bumper. Figure 3 is a perspective view of the bumper, Figure 4
The figure is an enlarged partial sectional view taken along the line (X)-(X) in FIG. 3.

As shown in the drawings, the side portions of the bumper (1) are bent inward to form undercut portions (2).

When molding a resin molded product having such an undercut part, one method for treating the undercut part is to forcibly deform the molded part to separate the undercut part from the mold. This method is called the forced extraction method).

This forced removal method will be explained based on FIGS. 5 to 7.

Figure 5 is a partial sectional view of an injection mold for molded products such as bumpers, where 00 is the fixed side cavity die, Ql)
1 is the core die on the movable side, and a product forming part (12) is formed between the two when the mold is clamped. The core die n+1 may be on the fixed side, and the cavity die (to) may be on the movable side. (131 is a parting surface, and the undercut portion (2) extends in a direction perpendicular to the opening/closing direction of the mold.

A cavity 04) facing the parting surface 03 is formed in the core die (111), into which the first slide core (3) and the second slide core (31) slide in a direction perpendicular to the mold opening direction of the mold. possible.

At the protrusion (lla) of the first slide core (sword, second slide core (31) and core die CII), the outer surface (2a) and the tip surface (2b) of the undercut portion (2), respectively.
) and an inner surface (2C).

Here, the outer surface (2a) of the undercut portion (2) is
When the undercut part is removed from the mold, the corresponding part of the mold must be removed in order to deform the molded product, and the tip surface (2b) refers to the surface that is pressed to deform the molded product. The inner surface (2c) is the surface that ultimately separates from the mold due to deformation of the molded product.

A driving means, such as a hydraulic cylinder, is disposed on the side of the core die 01), and its piston rod θG is fixed to the first slide core, and by driving the hydraulic cylinder area, the first slide core will be moved.

A cavity (32) is formed at the bottom of the second slide core (31), and a through hole (3) extends from the cavity (32) along the movement direction.
3) is formed. The space (32) has a flange part (35) and a rod part (
A connecting member (34) consisting of (36) is provided.

The rod portion (36) of the connecting member (34) has a through hole (33)
The distal end thereof is fixed to the bottom of the first slide core (2) by screwing or the like. Connecting member (
34) moves as the first slide core circle moves, but while the first slide core circle moves by a distance (Dl), the flange portion (35) of the connecting member (34)
so that the second slide core (31) does not move until it comes into contact with the locking part (37) of the second slide core (31).
The flange portion (35) of the connecting member (34) is a blank space (32)
The diameter of the rod (36) is also made slightly smaller than the diameter of the through hole (33). The flange portion (35) of the connecting member (34) is connected to the second slide core (
After coming into contact with the locking portion (37) of the second slide core (31), the second slide core (31) moves together with the first slide core circle.

In the mold-clamped state shown in FIG. 5, the product molding part 0'2J is filled with molten resin, and after cooling, the core die (old) is retracted and separated from the cavity die 02, and the mold is opened.

Next, as shown in Fig. 6, the hydraulic cylinder area is driven to move the first slide core ■ to the undercut portion (2
) in the direction of deformation (toward the right in the drawing) in order to release it (hereinafter referred to as forward movement). First slide core (the movement of the sword consists of a first stage movement and a second stage movement (however, these movements are continuous movements).

In the first stage, the flange part (35) of the connecting member (34) that has advanced together with the first slide core (3) moves forward with the second slide core (3).
This is the operation until it comes into contact with the locking part (37) of 1), during which the first slide core (2) moves forward by a predetermined distance (Dl).

The second stage is an operation in which the first slide core (7) moves forward together with the second slide core (31), during which the first slide core (7) and the second slide core (31) move by a predetermined distance (D2). Advance.

The predetermined distance (old) is usually the length (Ll) of the outer surface (2a) of the undercut portion (2) along the moving direction, that is, the length (Ll) of the undercut portion (2) formed on the first slide core (30). The length of the corresponding recess along the moving direction (Ll
) is about the same or slightly longer. Note that the length may be slightly shorter than the length (Ll) as long as the undercut portion (2) and the first slide core (2) do not interfere during the second stage operation later.

When the first slide core (30) moves forward by a distance (Dl),
The second slide core (31) still remains in its original position, and only the connecting member (34) moves forward, and its flange portion (35) engages the locking portion (37) of the second slide core (31).
).

When the first slide core (3) continues to move forward by a predetermined distance (D2) in the second stage operation, the second slide core (31) also moves forward by a distance (D2), as shown in FIG.

Then, the tip (2b) of the undercut (2)
is pressed by the second slide core (31), and the molded product (1)
The distal end surface (2b) changes over the distance (D2) with the deformation of
) to move a great deal. The distance (D2) is the length (L2) along the moving direction of the inner surface (2C) of the undercut part (6th
(see figure) is about the same or slightly longer. Therefore, when the second slide core (31) moves forward by a distance (D2), the inner surface (2C) of the undercut portion (2) is separated from a corner portion (llb) of the protrusion (lla) of the core die (11). Ru. In this state, when the molded product (1) is extruded in the opening/closing direction of the mold with an extrusion pin (not shown), the molded product (1) is easily removed from the core die 01), and the demolding operation is completed.

The demolded molded product (1) returns to its original shape.

[Problems to be Solved by the Invention] However, in the above mold structure, when the hydraulic cylinder is driven to advance the first slide core (2), the second slide core (2), which should not originally move during the first stage of operation, moves forward. 31) may move together. This phenomenon is caused by the surface tension of lubricating oil or the like adhering between the contact surfaces of the first slide core (30) and second slide core (31), or by the surface tension of the rod (36).
) and the through hole (33), mold release resistance of the molded product, etc. This occurs when the first slide core ('!A and the second slide core (31) become stuck together. , as shown in FIG.
2), and the undercut portion (2) also moves by a distance (Dl+D2) accordingly.

This is much larger than the moving distance (D2) of the undercut (2) during normal operation, so the amount of deformation of the molded product (1) may be too large, causing permanent deformation or, in extreme cases, damage. Problems such as storage may occur.

In view of the above points, the present invention provides a mold in which the second slide core does not operate abnormally during the first stage operation of the first slide core.

[Means for Solving the Problems] The present invention provides a mold for molding a resin molded product having an undercut portion extending substantially perpendicular to the opening/closing direction of the mold. a first slide core that forms the inner surface of the undercut portion, and a first slide core that mainly forms the outer surface of the undercut portion, and a first slide core that mainly forms the outer surface of the undercut portion; The first slide core and the second slide core are arranged so as to be movable in a direction perpendicular to the opening/closing direction of the mold, and the first slide core is moved forward a predetermined distance when demolding the mold. After the first slide core is separated from the outer surface of the undercut portion, the second slide core is connected so as to move forward in conjunction with the first slide core, and the undercut is removed by the advancement of the second slide core. The undercut treatment structure is configured such that the inner surface of the undercut portion is separated from the one mold by pressing the tip of the undercut portion to deform the molded product, the first slide core and the second slide core being separated from the other mold.
The present invention relates to an undercut processing structure in a resin molding die, characterized in that an elastic member is provided between the slide core and an elastic member that urges the two to move away from each other.

[Function] By providing an elastic member between the first slide core and the second slide core that urges them apart, the second slide core moves during the first stage of operation of the first slide core. Therefore, the molded product can be reliably removed from the mold without permanently deforming the molded product.

[Example code] Next, the present invention will be explained based on the drawings.

FIG. 1 is a schematic partial sectional view showing an embodiment of the mold of the present invention.

The mold shown in FIG. 1 has the same structure and operation as the mold shown in FIGS. 5 to 7 described above, except for the structures of the first slide core and the second slide core. 5th thing I wanted to do
The same elements as in FIGS. 7 to 7 are given the same reference numerals, and some explanations are omitted.

In Fig. 1, a recess (40) is formed at the bottom of the first slide core ('!A), a recess (41) is formed at the front of the second slide core (31), and a recess (4D) and a recess (4D) are formed at the front of the second slide core (31). 41
An elastic member (42), such as a compression coil spring, is arranged in the space formed by the first slide core ('3A) and the second slide core (31).

When the hydraulic cylinder 6 is driven to advance the first slide core (7) after opening the mold, the second slide core (31) moves forward by the action of the elastic member (42).
Since the sword is pressed in the opposite direction to the forward direction of the sword, the second slide core (31) and the first slide core (7) are prevented from coming into contact with each other and moving together, which is an abnormal operation, as shown in Fig. 2. The flange portion (35) of the connecting member (34)
) comes into contact with the locking part (37) of the second slide core (31), that is, until the first slide core (31) moves forward by a distance (Dl), the second slide core (31) remains in its original position. Stop, flange part (35) of connecting member (34)
It moves forward together with the first slide core (3CI) only after it comes into contact with the locking part (37) of the second slide core (31).

Therefore, as shown in FIG. 8, the second slide core (
31) moves together with the first slide core (30) from the beginning, and the molded product does not deform significantly to cause permanent deformation.

The second stage operation and the accompanying undercut part (
The removal of the core die 01) in 2) is the same as in the case of FIG. 7 described above.

The recessed portion for providing the elastic member (42) between the first slide core (1 and the second slide core (31)
As shown in the figure, it may be provided so as to span both the first slide core (3) and the second slide core (31), or it may be provided only on one of them.

The elastic member (42) is not limited to a compression coil spring, but may also be a plate spring, rubber, etc., as long as it biases the first slide core (3) and the second slide core (31) apart.

[Effects of the Invention] In undercut processing using the forced punching method, the molded product can be reliably deformed by a predetermined amount at the undercut portion and the undercut portion can be removed from the mold, thereby preventing permanent deformation of the molded product. No problems occur.

[Brief explanation of the drawing]

Fig. 1 is a schematic partial sectional view showing one embodiment of the mold of the present invention, Fig. 2 is a schematic partial sectional view showing the state at the time of demolding, Fig. 3 is a perspective view of the bumper, and Fig. 4 is the (X)-(X) in Figure 3
FIG. 5 is a schematic partial sectional view showing a mold using a conventional forced punching method, and FIGS. 6 to 8 are explanatory diagrams showing operations during undercut processing. (Main symbols in the drawings) (1), Molded product (2) - Undercut part 00): Cavity die 01): Core die a2), Product molding part (Inscription: 1st slide core (31): 2nd slide core ( 34); Connecting member (42): Elastic member six pieces

Claims (1)

[Claims] 1. In a mold for molding a resin molded product having an undercut portion extending in a direction substantially perpendicular to the opening/closing direction of the mold, either the fixed mold or the movable mold may form the inner surface of the undercut portion. , and a first slide core that mainly forms the outer surface of the undercut portion and a second slide core that mainly forms the tip of the undercut portion are attached to the one mold in the opening and closing direction of the mold. A first slide core and a second slide core are provided in front and rear so as to be movable in orthogonal directions, and the first slide core is moved forward a predetermined distance during demolding, and the first slide core is separated from the outer surface of the undercut portion. After this, the second slide core is connected to move forward in conjunction with the first slide core, and the forward movement of the second slide core presses the tip of the undercut part to deform the molded product and form the undercut. an undercut treatment structure configured to separate the inner surface of the part from the one mold, wherein an elastic member is provided between the first slide core and the second slide core to bias them in a direction to separate them. An undercut treatment structure in a resin molding die, characterized by being provided with an undercut treatment structure.