JP2005178066A - Injection molding method and molded product molded thereby - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the movement of a molded product from being moved at operation of an undercut molding core or the movement of the molded product having a high shrinkage factor in a center direction at shrinkage, in molding an molded product having an undercut. <P>SOLUTION: In the injection molding method for molding the molded product 100 by the cavity 109 formed by clamping a fixed mold 103 and a movable mold 102 and ejecting the molded product 100 by an ejector pin 106 after mold opening to demold the same from the fixed mold 103 or the movable mold 102, a cut part 106A is formed to the leading end of the ejector pin 106 and a projection molding space 110 is formed between the leading end of the ejector pin 106 and the surface of the cavity 109 by the cut part 106A. A part of a resin is penetrated in the space 110 from the interior of the cavity 109 at the time of filling with the resin to form a surrounding rib 108A which is locked with the ejector pin 106 simultaneously with the molding of the molded product 100 to prevent the movement of the molded product 100. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is an injection molding method for molding a molded product by filling a melted thermoplastic resin into a cavity formed in a mold, and in particular, there is an undercut portion or a shrinkage in a part of the molded product. The present invention relates to an injection molding method applied when a product is molded using a high-rate resin as a material, and a molded product molded by this molding method.

The molding method using an injection mold is a method in which a fixed mold and a movable mold are clamped, and a space (cavity) formed thereby is filled with molten resin to perform a pressure holding process and a cooling process. After a lapse of time, both the molds are generally opened and the molded product is ejected from the mold by ejector pins.
Therefore, in an injection mold used in such a molding method, a structure that prevents the opening and closing of the injection mold must be avoided as much as possible.
However, as shown in FIG. 1, when a receiving part 101 for fixing the molded product 100 is formed on a part of the molded product 100, the receiving part 101 is formed between a fixed mold and a movable mold. It becomes a shape caught in the opening and closing direction, that is, an undercut portion. For this reason, the molding process when the molded product 100 has an undercut portion is molded using the slide insert 105 formed on the inclined piece 104 as shown in FIG. When removing 100, as shown in FIG. 16 (b), the ejector pin 106 is ejected in synchronism with the opening and closing of the mold to release the molded product 100, and at the same time, the slide insert 105 of the inclined piece 104 is moved to the mold. By sliding in the direction perpendicular to the opening and closing direction, the slide insert 105 of the inclined piece 104 is extracted from the undercut portion, and when the slide insert 105 is completely extracted from the undercut portion, the ejector pin 106 is further removed. Thus, the molded product 100 is ejected and removed from the mold.

However, in the case of a resin having a low shrinkage rate, since the releasability from the mold is poor, it is difficult for the slide insert 105 to come off from the undercut portion, which may hinder the molding operation.
When a resin having a high shrinkage rate, for example, a crystalline resin is used, shrinkage occurs toward the center of the molded article 100 when the resin is cooled and solidified after filling. Therefore, in a mold in which a deep groove (a high rib 107 in the molded product 100) is formed in the cavity surface of the movable mold 103, a force in the center direction is applied to the molded product 100 due to contraction of the resin after filling the resin. As a result, the rib 107 bites into the groove on the cavity surface. For this reason, there may be inconveniences such as so-called galling in which meat is removed when the molded product 100 is taken out from the mold, the molded product 100 cannot be released from the mold, or the ribs are damaged.
In order to solve the above problems, the following techniques are disclosed.
First, the following is well-known about formation of an undercut part.

[Patent Document 1] Japanese Patent Application Laid-Open No. 2001-162658 SUMMARY OF THE INVENTION The present invention relates to a molding die capable of preventing a molded product from moving along with a projecting molding means when the projecting molding means moves to remove the projecting molded portion from the projecting portion of the molded product. In the injection mold 30, the fixed mold plate 34 and the movable mold plate 43 form a cavity 44 corresponding to the molded product 1, and the projecting molding portion 48 a of the projecting molding means 48 is a recess corresponding to the projecting portion 2. The point 49 communicates integrally with the cavity 44, and the ejector pin 47 protrudes slightly into the cavity 44 through the movable mold plate 43 in order to eject the molded product 1 from the cavity 44. Thus, after the molded product 1 having the projecting portion 2 is molded, when the projecting molding means 48 moves to remove the projecting molded portion 48a from the projecting portion 2, the ejector pin 47 is slightly engaged into the molded product 1. Therefore, it is an invention that the molded article 1 can be prevented from moving along with the protruding molding means 48. That is, according to the present invention, since the ejector pin is slightly projected into the cavity in advance, the molded product is restricted from moving even if the protruding molding means is moved by slightly entering the molded product. Is. However, since the ejector pin enters the molded product, only that portion becomes thin. As a result, the portion may be uneven in gloss and the desired design quality may not be obtained. Further, when the warpage of the molded product is large, the ejector pin may be detached from the molded product, and the movement preventing effect may not be obtained. Next, the following are well-known about the shrinkage | contraction of a molded article.

JP, 2003-11183, A In this invention, the fixed pin which reaches the inside of a cavity is fixed to the circumference of an ejector pin in the metallic mold device constituted from a fixed side mold plate and a movable side mold plate. In this state, resin is poured from the gate hole into the cavity. At this time, since the top of the fixing pin protrudes from the bottom of the cavity, the resin does not flow into the protruding portion. When the resin pouring is finished, the resin in the cavity is cooled and solidified. At this time, the molded product tends to shrink, but since the fixing pin is buried in the molded product, the shrinking operation is prevented. As a result, shrinkage of the molded product can be prevented as much as possible, and a good molded product can be obtained. However, as in Patent Document 1, since the fixing pin is inserted into the molded product, there is a problem of thinning of the molded product, a problem of unevenness of gloss, and a problem of detachment of the fixing pin due to warpage of the molded product.

A first object of the present invention is to provide an injection molding method in which a slide insert for forming an undercut portion operates smoothly when the molded product has an undercut portion.
A second object of the present invention is to provide an injection molding method capable of smoothly releasing when a mold having a rib structure is used to mold using a resin having a high shrinkage rate.
The third object of the present invention is to provide a molded product having a sufficient rib shape with no damage to the ribs of the molded product.

  In order to achieve the above object, according to the first aspect of the present invention, in the injection molding method, after opening a molded product formed by a cavity formed by clamping a fixed side mold and a movable side mold. In the injection molding method in which the molded product is released from the fixed side mold or the movable side mold by projecting with the ejector pin, by forming the cut part at the tip of the ejector pin, the tip of the ejector pin at the cut part A projection forming space is formed between the inlet of the ejector pin guide hole in the cavity and a part of the resin enters the space from the cavity when the resin is filled. A protrusion for pin engagement is formed.

  Further, in the invention described in claim 2, the projection forming space of claim 1 is formed by forming the entrance portion of the ejector pin guide hole with a large diameter on the outer peripheral surface and the cavity surface of the tip of the ejector pin. It is characterized by being formed with a large diameter portion.

  Furthermore, the invention according to claim 3 is characterized in that the projecting portion forming space according to claim 1 is composed of an annular or semi-annular surrounding rib groove formed in the inlet portion of the ejector pin guide hole. is there.

  Further, in the invention described in claim 4, the projection forming space of claim 1 is characterized by comprising a linear plate-like rib groove formed in the inlet portion of the ejector pin guide hole. .

  Further, the invention according to claim 5 is characterized in that the projection forming space of claim 1 is formed of a radial plate-like rib groove formed at the entrance portion of the ejector pin guide hole.

  Further, in the invention described in claim 6, the projection forming space of claim 1 is formed by an annular or semi-circular surrounding rib groove formed in the entrance portion of the ejector pin guide hole and a linear shape formed outside thereof. It is characterized by being formed by plate-like rib grooves that are parallel or radial or a combination of this parallel and radial.

  Further, the invention according to claim 7 is characterized in that the plate-like rib groove of claim 6 is formed deeper than the annular and semi-annular surrounding rib grooves.

  Further, the invention according to claim 8 is characterized in that in the injection-molded product, a protrusion is integrally formed on the whole or a part of the periphery facing the tip of the ejector pin.

[Action]
Protrusions that support the stress on the tip of the ejector pin are formed at the same time as molding the molded product, and molded when the slide insert slides due to the engagement between the ejector pin and the projecting portion, or when the molded product is thermally contracted Prevent movement of goods.

The effects of the present invention are as follows.
1. Since the protrusion is integrally formed with the rib groove adjacent to the ejector pin on the molded product, the molded product engages with the ejector pin at this protrusion, and the molded product moves when the slide insert slides. The molded product does not move due to the stress associated with resin shrinkage. As a result, the molded product can be easily released from the mold (claims 1 to 8).
2. By forming the projecting portion as a deep plate-like rib groove by the surrounding rib groove and the surrounding rib, the molded product can be reliably held even when the molded product is warped (Claims 4 to 7).
3. Since the plate-shaped rib grooves for forming the protrusions are formed radially, the formed plate-shaped ribs are engaged with the ejector pins in all or part of the periphery, which prevents the molded product from moving in all directions. It is effective (claim 5).
4). By combining the annular or semi-annular surrounding rib groove and the plate-like rib groove, a projecting portion having high strength can be formed (Claim 6).
5). At the time of mold release in the molding process, the molded product is fixed by the engaging action of the ejector pin and the protrusion. Therefore, in the case of a molded product having a rib shape, a molded product having a stable strength without damage to the rib is obtained. (Claim 8).

The injection molding method according to the present invention is characterized by an injection molding method in which a protrusion engaging with a tip side surface of an ejector pin is integrally formed with a molded product.
Therefore, even if the fixed side mold and the movable side mold of the mold start to open and the slide insert starts to move in a direction perpendicular to the opening direction of the mold, the slide pin is inserted due to the engagement between the ejector pin and the protrusion. It is possible to prevent the molded product from moving due to the adhesion between the child and the resin in the undercut portion. Accordingly, the slide insert can be smoothly extracted from the undercut forming portion.
In addition, the shrinkage direction that occurs when the molten resin in the cavity solidifies occurs toward the center of the molded product, but if the molded product has high ribs, the resin in the groove on the cavity surface will adhere to the groove surface due to shrinkage. As a result, the releasability becomes worse.

However, due to the engagement effect between the ejector pin and the protrusion, it is possible to prevent shrinkage, and the molded product can be easily released from the mold without the molded product being in close contact with the groove on the cavity surface.
Further, in Patent Documents 1 and 2, the movement of the molded product is prevented by slightly moving the tip of the ejector pin or the fixed pin into the molded product. Therefore, the ejector pin or the fixed pin enters the molded product. It is necessary that the thickness of the molded product is as large as possible. Further, when the warpage of the molded product is large, the ejector pin or the fixing pin may be detached from the molded product, and the effect may not be obtained. However, according to the present invention, the protrusion between the ejector pin and the molded product can be deeply engaged by integrally forming the protruding portion that engages with the ejector pin on the molded product side instead of entering the molded product. The meeting is surely done. Moreover, since a thin part is not formed in a molded product, the factor which generate | occur | produces gloss nonuniformity can be removed.

As a method of forming the projection, the projection molding space can be formed here by making the periphery of the tip surface of the ejector pin one stage, but of course, it is the cavity surface, and the ejector pin guide hole It is also possible to form a projection forming space by forming a large-diameter hole or groove at the inlet by this guide hole.
In the injection molding method according to a third aspect, the protrusion molding space according to the first aspect is an annular or semi-annular surrounding rib groove surrounding the tip side surface of the ejector pin.
The shape of the rib groove has an advantage that a sink problem does not occur in the molded product. In addition, by forming a shape that surrounds all or part of the tip of the ejector pin, it can be joined annularly or semi-annularly to the ejector pin and reliably engaged against movement and contraction from all directions. Can do.
Further, when the direction of stress applied to the ejector pin can be predicted, a semi-circular surrounding rib groove may be formed only at a position where the stress is received.

In the injection molding method according to claim 4, a plurality of protrusion molding spaces according to claim 1 are engaged with the tip side surface of the ejector pin, and are extended to a stressed position in the ejector pin and in the stress direction. A projection forming space for forming the plate-shaped rib is formed on the cavity surface, whereby the plate-shaped rib is integrally formed with the molded product.
The direction of the plate-like rib groove is formed so as to extend in the direction of the stress, and since the ejector pin is received at the end face, the plate-like rib does not deform even when more stress is applied, for example, linear and parallel Or it is set as the multiple sheet shape which consists of radial form or these combination.
Further, by forming a plurality of plate-like ribs, the plate thickness per sheet can be reduced, and the total area for receiving the ejector pins can be made wider than in the case of a single plate.

Further, in the injection molding method according to claim 6, since the plate-like rib is formed outside the annular or semi-annular surrounding rib according to claim 3, the strength of the surrounding rib can be increased.
Furthermore, in claim 7, the plate-like rib is formed so that its height is higher than that of the surrounding rib. For example, if the height of the surrounding rib is increased in order to further increase the engagement between the surrounding rib and the ejector pin or prevent the molded product from being detached from the surrounding rib even if the molded product is warped, the contact area between the surrounding rib and the ejector pin is increased. The ejector pin may not come off due to the increased contact. However, if it is a plate-like rib, it engages with the ejector pin only on the necessary surface, so even if the surrounding rib side is made higher so that the ejector pin does not come off the plate-like rib, the contact area is small and it is easy to release. it can.
Therefore, even if the molded product is warped and the surrounding rib is separated from the ejector pin, the plate-like rib can receive the ejector pin, and it has a good effect on the releasability due to sliding of the undercut slide insert and resin shrinkage. can get.

An embodiment of the invention described in claims 1 and 2 will be described with reference to FIGS. FIG. 1 shows a molded product 100 molded according to the first embodiment. It is substantially plate-shaped and has side walls 100A on both sides, and is used as a cover of the apparatus main body as a use. A reinforcing rib 107 is provided on the back surface, and a fixing portion 101 for attaching the cover to the apparatus main body is integrally formed. The fixed part 101 has a hollow box shape with an opening on a side surface. Therefore, since this fixing portion 101 has an opening in a direction perpendicular to the direction in which the injection mold is opened, this is an undercut portion. Therefore, in order to mold, the description has been made based on FIG. A molding method using the slide insert 105 is required.
In the injection molding method of Example 1 for molding such a molded product 100, as a method of forming the protrusion 108A for engaging the ejector pin, as shown in FIG. 2, the molded product 100 is ejected from the mold to the ejector pin. Further, the step portion 106A was formed with the periphery of the tip surface portion as one paragraph. In terms of dimensions, the diameter R of the ejector pin 106 was 10 mm, the diameter r of the convex portion at the tip was 8 mm, and the height h was 2 mm. Therefore, the width of the step portion 106A is 1 mm. However, the side surface of the convex portion is slightly inclined so that it can be easily removed.

By forming the protrusion molding space 110 on the surface of the cavity 109 with the ejector pins 106 described above, as shown in FIG. 1, a circular surrounding rib (projection) 108 </ b> A is integrally formed on the molded product 100.
Next, a molding method using the ejector pin 106 shown in FIG. 2 will be described with reference to FIG.
3A and 3B are cross-sectional views of the main part near the undercut portion and the ejector pin in the injection mold and the molded product. FIG. 3A is an explanatory diagram in which the resin is filled in the cavity, and FIG. 3B is the injection mold. Explanatory drawing which has opened the type | mold and protruded the molded product with the ejector pin, (c) is a cross-sectional explanatory drawing of the molded product completed shaping | molding. The tip shape of the ejector pin 106 is exaggerated from the shape shown in FIG. 2 for easy understanding.
In the movable mold 103 in FIG. 3 (a), the slide insert 105 is located at the tip of the inclined piece 104 that forms the undercut-shaped fixed portion 101, and the top surface is positioned at the same position as the cavity 109 surface when filled with resin. Ejector pins 106 are provided. The cavity 109 was filled with a molten resin after the movable side mold 103 and the fixed side mold 102 were clamped. Polystyrene (PS) resin was used as the resin in this example.

The melted resin is formed in the space between the slide insert 105 continuous with the cavity 109 and the movable mold 103 (formation of a fixed portion), and the projection portion between the tip of the ejector pin 106 and the ejector pin guide hole 103A. The space (formation space of the surrounding rib 108A) 110 is also filled.
After completion of filling the molten resin, the resin is solidified by cooling while holding the pressure, and then the mold clamping between the movable side mold 103 and the fixed side mold 102 is released as shown in FIG. 3B, and the mold is opened. In synchronism with the opening, the ejector pins 106 are ejected, and the molded article 100 thus formed is released. Further, as a result of the inclined piece 104 protruding in the oblique direction, the slide insert 105 at the tip moves in a direction perpendicular to the opening direction of the mold. At this time, since the resin of the fixing portion 101 which is an undercut is in close contact with the peripheral slide insert 105, a force for moving the molded product is generated.

However, since the molded product 100 is fixed by fitting the ejector pin 106 and the surrounding rib (projection) 108A, the slide insert 105 can be detached from the fixed portion 101. Thereafter, the molded product (cover) 100 in which the undercut fixing portion 101 is integrally formed as shown in the cross-sectional view of FIG.
FIG. 4 is a perspective view showing a positional relationship between the fixing portion 101 and the surrounding rib 108A in the molded product 100. FIG. From FIG. 4, it is possible to understand the relative relationship between the exit portion where the slide insert 105 moves in the fixed portion 101 and the location where the surrounding rib 108 </ b> A is formed.
FIG. 5 shows a semi-circular surrounding rib 108A ′ as a protrusion. If the direction of stress from the ejector pin 106 is fixed, a semi-circular surrounding rib may be provided only at the stress position.

In Example 2, an example of molding using a resin material having a high shrinkage rate will be introduced based on FIG.
6 (a) and 6 (b) are cross-sectional views of the main part in the vicinity of the rib and the ejector pin in the injection mold and the molded product. FIG. 6 (a) is an explanatory diagram in which the cavity is filled with resin. These are explanatory drawings which open the metal mold | die for injection molding and protrude the molded product with the ejector pin.
Many ribs 107 (only representative parts are shown in FIG. 6) are formed on the back surface of the molded product 100 in this embodiment (see FIG. 1). The rib 107 has a shape of 6 mm in height and 1 mm in width on the top surface. In the conventional molding method, since the shrinkage ratio of the resin is high, when the molten resin is solidified, the force (in the direction of the arrow) shown in FIG. The resin filled in the side surface of the groove 103B formed in the above is pressed. Therefore, the mold release resistance becomes high and the molded product 100 cannot be removed from the mold, or the resin is torn off in the groove 103B, or inconveniences such as galling occur.

In this embodiment, the ejector pin 106 used in the first embodiment is incorporated into an injection mold, and melted polystyrene (PS) resin is filled in the cavity 109 as shown in FIG. went.
Next, when the resin is solidified, as shown in FIG. 6B, the mold clamping between the movable mold 103 and the fixed mold 102 is released, and the mold is opened. In synchronization with this opening, the molded product 100 is ejected by the ejector pin 106. Although a contracting force is generated in the molded product 100, the contraction is suppressed by fitting the ejector pin 106 and the surrounding rib 108A. Therefore, the rib 107 can be extracted from the groove 103B with a small release resistance, so that the resin is not left in the mold or cannot be extracted. Thereafter, when the ejector pin 106 is further protruded and the molded product is taken out from the injection mold, the molded product (cover) 100 shown in FIG. 4 is completed.

Next, an embodiment of the invention described in claims 4 and 5 will be described with reference to FIGS.
In the first embodiment, the step portion 106A is formed on the ejector pin 106 to form the surrounding rib 108A. However, in the third embodiment, the concave portion (space) 110 for forming the plate-like rib (projection portion) 108B is formed on the surface of the cavity 109. The ejector pin 106 is formed so as to be engaged with a position where the stress or contraction force of the slide insert 105 is applied. The plate-like rib 108B has a dimension of 3 mm in height and 4 mm in width and 0.5 mm on the top surface. Others are the same as the first embodiment.
FIG. 7 is a cross-sectional view of an essential part near an undercut and an ejector pin in an injection mold and a molded product, (a) is an explanatory diagram in which a resin is filled in a cavity, and (b) is an injection mold. Explanatory drawing which has opened and ejected the molded product with the ejector pin, (c) is a cross-sectional explanatory drawing of the molded product which has been molded.

In the movable mold 103 in FIG. 7 (a), the slide insert 105 at the tip of the inclined piece 104 that forms the undercut-shaped fixed portion 101 and the top surface are positioned at the same position as the cavity 109 surface when filling with resin. Ejector pins 106 are provided. The cavity 109 was filled with a molten resin after the movable side mold 103 and the fixed side mold 102 were clamped.
After completion of filling with the molten resin, cooling is performed while maintaining pressure, and the resin is solidified. Then, as shown in FIG. 7B, the movable side mold 103 and the fixed side mold 102 are clamped and the mold is opened. In synchronization with the opening, the ejector pin 106 is ejected to release the molded product 100 formed. At this time, since the resin of the fixing portion 101 which is an undercut is in close contact with the peripheral slide insert 105, a force for moving the molded product is generated.
However, since the molded product 100 is fixed by the engagement between the ejector pin 106 and the plate-like rib 108 </ b> B, the slide insert 105 can be detached from the fixed portion 101. Thereafter, when the ejector pin 106 is further protruded and taken out from the injection mold, a molded product (cover) 100 in which the undercut fixing portion 101 shown in the cross-sectional view of FIG. 7C is integrally formed is completed.
FIG. 8 is a perspective view showing the positional relationship between the fixing portion 101 and the plate-like rib 108B in the molded product 100. FIG. The virtual position of the ejector pin 106 is indicated by a broken line. The relative relationship between the opening, which is the exit of the slide insert 104 in the fixed portion 101, and the place where the plate-like rib 108B is formed can be understood.

Embodiments of claims 4 and 5 will be described with reference to FIG. FIG. 9 is a top view of the plate-like rib 108B according to the fourth and fifth aspects. Of the plurality of plate-like ribs 108B, the plate-like ribs 108C at both ends are formed radially, and the plate-like ribs 108C are reinforcing ribs. A broken line is a virtual position of the ejector pin 106.
Even if the stress from the ejector pin 106 is applied to the plate-like rib 108B, the plate rib 108B can be prevented from being turned or crushed by the auxiliary rib 108C.
Although the said Example is description of the plate-shaped rib 108B and the reinforcing rib 108C, you may form all the plate-shaped rib 108B radially like the reinforcing rib 108C. At this time, the radial rib may be the entire periphery of the ejector pin 106 or a part of the stress direction.

An embodiment of the invention described in claim 6 will be described with reference to FIGS.
FIGS. 10A, 10B, and 10C are cross-sectional views of the main part near the undercut and the ejector pin in the injection mold and the molded product, and FIG. 10A is an explanation of filling the cavity with resin. FIG. 5B is an explanatory view in which an injection mold is opened and a molded product is projected by an ejector pin, and FIG. 5C is a cross-sectional view of the molded product that has been molded. 11A and 11B are explanatory views of the surrounding rib and the plate-like rib, and FIG. 11A is a perspective view and FIG. 11B is a top view.

The mold structure of the present embodiment is based on the mold structure of the first embodiment, and is higher than the surrounding rib 108A at the position of the outer side surface of the surrounding rib 108A that is opposite to the direction in which the slide insert 104 comes out of the undercut. The feature is that the plate-like rib 108B is formed. In this embodiment, the plate-shaped rib 108B has two plate-shaped ribs 108B having a rib shape as shown in FIG. Thus, by forming the peripheral rib 108A low and the plate-like rib 108B high, it is possible to prevent the occurrence of sink marks seen in the thick stepped portion. Further, by arranging the ejector pins 106 in parallel in the radial direction, it is possible to effectively cope with the pressing force from the ejector pins 106.
The molding method will be described with reference to FIG. Polypropylene (PP) resin was used as the resin material. Since PP resin tends to warp, it may come off from the surrounding rib 108A shown in the first embodiment (see FIG. 12). In particular, this tendency is seen as the position of the ejector pin 106 is further away from the center of the molded product 100.
First, as shown in FIG. 10A, after the movable side mold 103 and the fixed side mold 102 are clamped, the melted resin is filled into the cavity 109.
The molten resin includes a space between the slide insert 104 and the movable mold 103 continuous with the cavity 109 (formation of a fixed portion), a tip of the ejector pin 106, an ejector pin guide hole 103A, and a plate-like rib forming portion. The space 110 (formation of plate-like ribs) is also filled.

After completion of filling the molten resin, cooling is performed while maintaining pressure, and when the resin is solidified, the mold is opened between the movable mold 103 and the fixed mold 102 as shown in FIG. 10B, and the mold is opened. In synchronization with the opening, the ejector pin 106 is ejected to release the molded product 100 formed. In addition, the tilting piece 104 also protrudes in an oblique direction, and the slide piece 105 at the tip is moved at right angles to the opening direction of the mold. At this time, even if the molded product 100 is warped and removed from the surrounding rib 108A, the ejector pin 106 can be received by the plate-like rib 108B higher than the surrounding rib 108A, so that the molded product 100 is fixed. The slide insert 105 can be detached from the fixed portion. Thereafter, when the molded product 100 is further ejected by the ejector pins 106 and taken out from the injection mold, the molded product 100 in which the undercut fixing portion 101 shown in the sectional view of FIG. 10C is integrally formed is completed.
The surrounding rib 108A has an effect of preventing the surrounding rib 108A from being turned over as shown in FIG. 13 because the fracture strength is improved by the plate-like rib 108B.

Another embodiment relating to claim 6 will be described with reference to FIG. 14 (a) and 14 (b) are explanatory views of the embodiment of claim 6, (a) is an explanatory view of a cavity composed of a movable side mold and a fixed side mold, and (b) is an ejector pin. It is explanatory drawing protruded by.
In the fifth embodiment described above, the reinforcing rib 108B is provided at a position opposite to the direction in which the slide insert 105 comes out of the undercut. In this embodiment, the difference is that the shrinkage of the molded product 100 generally works in the center direction of the molded product 100, so that the height of the surrounding rib 108 </ b> A is at a position opposite to the central direction in the molded product 100 as shown in FIG. 14. This is because the plate-like rib 108B having a height higher than that is formed.
In the injection molding method, after the movable mold 103 and the fixed mold 102 are clamped, the melted resin is filled into the cavity 109 (FIG. 14A), and the mold is opened after the resin is solidified. The molded product 100 is taken out. At that time, the rib can be smoothly extracted from the groove with a small release resistance by suppressing the shrinkage of the resin by the surrounding rib 108A. Further, even if the molded product 100 is warped and the ejector pin 106 is detached from the surrounding rib 108A, the ejector pin 106 is received by the plate-like rib 108B higher than the surrounding rib 108A, so that the molded product 100 can be removed from the mold without any trouble (see FIG. 14 (b)).

In this embodiment, various shapes of projections and combinations thereof will be introduced based on FIG. FIG. 15 is a top view of all the protrusions. Further, the plate-like rib 108B and the reinforcing rib 108C are set to be higher than the surrounding ribs 108A and 108A ′.
FIG. 15A shows a semicircular surrounding rib 108A ′ that engages with about a half circumference of the ejector pin 106, and can be used when the direction of the stress is fixed. In FIG. 15B, the plate-like rib 108B and the reinforcing rib 108C are combined with the semicircular surrounding rib 108A ′ of FIG. Of course, only the plate-like rib 168B can be selected. In FIG. 15C, the plate-like rib 108B and the reinforcing rib 108C are combined with the annular surrounding rib 108A (in the fifth embodiment, only the plate-like rib 108B). FIG. 15D shows the surrounding rib 108A when the ejector pin 106 is square, and FIG. 15E shows the semicircular surrounding rib 108A ′ of FIG. 15D.
FIG. 15 (f) shows a projection portion in which the square semi-enclosing rib 108A ′ and the plate-like rib 108B of FIG. 15 (e) are combined, and FIG. 15 (g) shows a further addition of a reinforcing rib 108C.
FIG. 15H shows an example in which the protrusions are formed by combining all the plate-like ribs 108B and the auxiliary ribs 108C radially.
As described above, the optimum shape and combination of the ribs can be selected depending on the mold structure, molded product, injection conditions, and the like.

The external view of the molded article shape | molded by the Example of this invention. Explanatory drawing of the ejector pin used for Example 1. FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram for explaining an injection molding die and a molding method in Example 1 based on the vicinity of an undercut and an ejector pin, where (a) is at the time of resin injection, (b) is at the time of mold release, (c ) Is an explanatory diagram of a molded product. Explanatory drawing of the fixing | fixed part and surrounding rib of the molded article shape | molded in Example 1. FIG. The perspective view of a semi-annular surrounding rib. Explanatory drawing at the time of mold release of a molded product explaining the injection die and molding method in Example 2 based on the rib of a molded product, and the ejector pin vicinity. FIG. 4 is an explanatory diagram for explaining an injection mold and a molding method in Example 3 based on an undercut of a molded product and the vicinity of an ejector pin, where (a) is a resin injection, and (b) is a molded product release. (C) is explanatory drawing of a molded article. The perspective view which shows the positional relationship of the fixing | fixed part and plate-shaped rib in a molded article. Explanatory drawing of the plate-shaped rib in Example 4. FIG. It is explanatory drawing explaining the injection die in Example 5, and a shaping | molding method based on undercut and the vicinity of an ejector pin, (a) at the time of resin filling, (b) at the time of mold release, (c) is Explanatory drawing of a molded article. It is explanatory drawing of the surrounding rib and plate rib in Example 5, Comprising: (a) is a top view, (b) is a perspective view. Explanatory drawing when a molded product warps. Explanatory drawing which the surrounding rib deform | transformed. FIG. 7 is an explanatory diagram for explaining the injection molding die and molding method in Example 6 based on the vicinity of a rib and an ejector pin, where (a) is a pressure holding and cooling, and (b) is an explanatory diagram at the time of release. . (A)-(h) is explanatory drawing of the shape of a projection part. Explanatory drawing of the main part near the undercut and ejector pin in a conventional injection mold and a molded product, and a molding process.

Explanation of symbols

100 Molded article 101 Fixed portion 4 Rib 108 Projection portion 102 Fixed side mold 103 Movable side mold 109 Cavity 106 Ejector pins 108A, 108A 'Surrounding rib 108B Plate-shaped rib 108C Reinforcing rib

Claims (8)

  The molded product formed by the cavity formed by clamping the fixed side mold and the movable side mold is released from the fixed side mold or the movable side mold by pushing the ejector pin after the mold is opened. In this injection molding method, by forming a cut portion at the tip of the ejector pin, a projection forming space is formed between the tip of the ejector pin and the inlet of the ejector pin guide hole in the cavity at the cut portion. An injection molding method for molding a protrusion for engaging an ejector pin at the same time as molding of a molded product by allowing a part of the resin to enter the space from the inside of the cavity during resin filling.   The protrusion forming space of claim 1 is formed by a large-diameter portion formed by forming the entrance portion of the ejector pin guide hole to a large diameter on the outer peripheral surface and the cavity surface of the tip of the ejector pin. Injection molding method.   2. The injection molding method according to claim 1, wherein the projection forming space comprises an annular or semi-annular surrounding rib groove formed in an inlet portion of the ejector pin guide hole.   2. The injection molding method according to claim 1, wherein the projecting portion forming space comprises a straight plate-like rib groove formed at an inlet portion of the ejector pin guide hole.   2. The injection molding method according to claim 1, wherein the projecting portion forming space comprises a radial plate-like rib groove formed at an inlet portion of the ejector pin guide hole.   The projection forming space of claim 1 is an annular or semi-annular surrounding rib groove formed in the entrance portion of the ejector pin guide hole and a linear parallel or radial formed outside thereof, or a combination of this parallel and radial. An injection molding method comprising a plate-like rib groove.   7. The injection molding method according to claim 6, wherein the plate-like rib groove is formed deeper than the annular or semi-annular surrounding rib groove. An injection-molded product, wherein a protrusion is integrally formed on all or part of the periphery facing the tip of the ejector pin.

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