JP2005178185A - Injection molding mold and method for producing injection-molded article using the mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding mold which has an undercut part curving inside in the end part of a molding body and injection-molds a molding with a parting line made invisible from the outside when assembled and a method for producing the injection-molded article using the mold. <P>SOLUTION: The injection molding mold is composed of a movable mold comprising an inclination core which is contacted slidably with the side of a core and is made movable inward by extrusion and a slide core which has an undercut part outer surface molding surface and a particle surface having an undercut part tip surface molding surface and a projection and is forward/backward movable in relation to the undercut part inner surface molding surface of the inclination core and a fixed mold having a molding main body outer surface molding surface, a step part positioned on the outside of the molding surface, and a particle surface positioned inward from the molding surface through the step part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an injection mold for injection molding a molded product having an undercut portion bent inward at an end portion of a molded product body, and an injection molded product manufacturing method using the same.

  Since injection molding is suitable for mass production of thermoplastic resin molded products, it is applied to the production of various molded products. Large products such as automotive bumpers, instrument panels and radiator grills are also manufactured by injection molding.

  Among these injection-molded products, there is a molded product having an undercut portion that bends inward at an end portion of a molded product body, such as an automobile bumper. That is, as shown in FIGS. 6 and 7, the automobile bumper is formed with a rolled portion 202 that bends inwardly at the foil arch portions 201 at both ends of the bumper body 200, and the fender portions 203 near the upper ends of both ends of the bumper body 200. A fender mating portion 204 that bends inward is formed.

  The rolling part 202 is necessary for installing mudguards, and the fender mating part 204 is necessary for the design of the fender part 203, but the under part that bends inward to the end of such a molded product body. When a molded product having a cut portion is injection-molded, there is a drawback that parting lines are generated in the foil arch portion 201 and the fender portion 203.

Conventionally, as an injection mold for injection-molding a molded product having an undercut portion that bends inwardly at the end of the molded product body, for example, as shown in FIG. There is known an injection mold 100 including a movable mold 101 and a fixed mold 102 in which a cavity 104 is formed, and a slide core 103 having molding surfaces 103a and 103b for molding the front end surface and outer surface of an undercut portion of a molded product. (For example, refer to Patent Document 1).
JP 2002-192666 A

  In order to perform injection molding with the injection mold 100, molten thermoplastic resin is injected into the cavity 104 for molded product, the movable mold 101 is retracted to open the mold, and the slide core 103 is retracted to move the undercut portion. Remove from the mold 101 and eject the ejector pin 105 to obtain a molded product.

  Since a parting line is generated on the contact surface between the fixed mold 102 and the slide core 103 in the molded product molded by the injection molding die, in the above-described automobile bumper, the parting line is formed on the foil arch part 201 and the fender part 203. When the car was assembled and viewed from the side, this parting line was visible, and there was an aesthetic problem.

  In view of the above-mentioned drawbacks, the object of the present invention is an injection for injection-molding a molded product that has an undercut portion that bends inwardly at the end of the molded product body and from which the parting line is not visible when assembled. An object of the present invention is to provide a molding die and a method for producing an injection molded product using the same.

The injection mold according to claim 1 is composed of a fixed mold and a movable mold that can be freely opened and closed. When the mold is closed, a cavity for the molded product is formed. An injection mold for injection molding a molded product having an undercut portion to be inserted,
The movable mold has a core having a molded body inner surface, a molded body inner surface and an undercut inner surface, and is slidably in contact with the side surface of the core. A tilted core that is movable, a tip surface forming surface of an undercut part, an outer surface forming surface and a particle surface of an undercut part, and an undercut part inner surface forming surface of an inclined core. On the other hand, it consists of a slide core that can move forward and backward,
The fixed mold has a molded product body outer surface molding surface, a step portion located outside the molding surface, and a particle surface located inward from the molding surface via the step portion,
When the mold is closed, the particle surface of the slide core and the particle surface of the fixed mold are brought into close contact with each other, and the core molded product body inner surface molding surface, the inclined core molded product body inner surface molding surface, the undercut portion inner surface molding surface, A molded product cavity is formed by the tip surface molding surface of the undercut portion and the outer surface molding surface of the undercut portion, and the molded product outer surface molding surface and the step portion of the fixed mold. .

  The injection mold according to claim 1 is capable of injection-molding a molded product having an undercut portion bent inward at an end portion of a molded product body, and the particle surface of the fixed mold and the particle surface of the slide core are The particle line is formed on the outer surface of the undercut portion because it contacts the outer surface of the undercut portion. Therefore, a molded product in which the parting line cannot be seen from the outside when assembled is obtained.

The method for producing an injection-molded article having an undercut portion that bends inward at the end of the molded article body according to claim 5 uses the injection mold according to any one of claims 1 to 4, and the following steps: It is characterized by comprising.
(1) Clamping the injection mold and injecting resin for injection molding into the molded product cavity, (2) With the undercut part of the molded product fixed, the inclined core and slide core are fixed The process of partially retracting the movable mold until the end of the molded product body is inside the fixed mold particle surface while deforming the molded product while following it.
(3) a step of retracting the entire movable mold and opening the mold;
(4) separating the slide core from the inclined core, releasing the fixing of the undercut portion of the molded product, and releasing the deformation of the molded product; and
(5) Step of taking out the molded product

  In the method of manufacturing an injection molded product having an undercut portion that bends inward at the end of the molded product body according to claim 5, an injection molded product in which particle lines are formed on the outer surface of the undercut portion can be easily obtained. .

  6. The manufacturing method according to claim 5, wherein the injection-molded product having an undercut portion bent inward at an end portion of the molded product main body according to claim 6 is an automobile bumper. It is.

  The injection-molded product obtained by the method for producing an injection-molded product having an undercut portion that bends inward at the end of the molded product body according to claim 6 has a particle line formed on the outer surface of the undercut portion, Since the parting line is not visible from the outside when assembled, it can be suitably used as an automobile bumper.

  The structure of the injection mold of the present invention and the method of manufacturing an injection molded product using the same is as described above, and has an undercut portion that bends inward at the end of the molded product body, and is external when assembled. Therefore, an injection molded product in which the parting line is not visible can be easily manufactured.

  Hereinafter, although an embodiment of the present invention is described based on a drawing, the present invention is not limited to the following example.

  FIG. 1 is a cross-sectional view showing an example of an injection mold according to the present invention, and shows a state where the injection mold is closed.

  In the figure, reference numeral 1 denotes a fixed mold in which a sprue 11 for supplying an injection molding resin is formed. Inside the fixed mold 1, a molded product main body outer surface molding surface 12 connected to the sprue 11, a step portion 13 outside the molded product main body outer surface molding surface 12, and an end portion of the step portion 13 are connected. A particle surface 14 located inward of the molded product outer surface molding surface 12 is formed.

  In the figure, reference numeral 2 denotes a movable type, and the movable type 2 includes a core 4, a pair of inclined cores 5, and a slide core 6. The core 4 has a front end surface which is a molded product body inner surface molding surface 41, which becomes wider toward the lower end (right side in FIG. 1), and the side surface is an inclined surface.

  The lower end portion is fixed to a hollow support block 21, and the core 4 and the support block 21 are integrally formed. Furthermore, a through hole 22 is formed in the support block 21 along the inclined surface of the core 4.

  The inclined core 5 includes an inclined core body 51 having a molded product body inner surface molding surface 54 and an undercut portion inner surface molding surface 55 connected thereto, a support member 52 formed integrally with the inclined core body 51, It consists of a slide block 53.

  The support member 52 is slidably inserted into a through-hole 22 provided in the support block 21 and is installed in the hollow portion of the support block 21 so as to be capable of moving forward and backward in the front-rear direction (left-right direction in FIG. 1). The tilted core body 51 is attached to a slide block 53 that is movable inward and outward (vertical direction in FIG. 1) and tilted inward so as to slide along the side surface of the core 4.

  That is, when the slide block 53 is moved forward, the inclined core body 51 slides and advances along the side surface of the core 4, and the interval between the inclined core body 51 and the pair of inclined core bodies 51 becomes narrower and moves backward. Spread to the original spacing.

  The slide core 6 has a tip surface molding surface 61 of the undercut portion, an outer surface molding surface 63 of the undercut portion, and a particle surface 64 that comes into contact with the particle surface 14 of the fixed die 1 when the mold is closed. A protrusion 62 is formed on the outer surface molding surface 63 of the undercut portion.

  In addition, an inclined hole 66 parallel to the inclined surface of the core 4 is formed on the surface opposite to the outer surface molding surface 63 of the undercut portion, and the guide is erected on the support block 21 in parallel with the inclined surface of the core 4. A block 65 is slidably inserted.

  Therefore, the slide core 6 is disposed in contact with the outer surface of the support member 52 of the inclined core 5 so as to be capable of moving forward and backward with respect to the undercut portion inner surface molding surface 55.

  The support block 21, the slide block 53, and the slide core 6 are connected to different drive devices (not shown), and can be moved separately.

  In the injection mold, when the mold is closed, the particle surface 64 of the slide core 6 and the particle surface 14 of the stationary mold 1 are brought into close contact with each other. Molded product body inner surface molding surface 54 and undercut portion inner surface molding surface 55, tip surface molding surface 61 of undercut portion of slide core 6 and outer surface molding surface 63 of undercut portion, and molded product body outer surface molding of fixed mold 1 The molded product cavity 3 is formed by the surface 12 and the stepped portion 13.

    Next, the manufacturing method of the injection molded product which has the undercut part which curves inside at the edge part of a molded product main body using the said injection mold is demonstrated with reference to drawings.

  First, as shown in FIG. 1, the injection mold is closed, and an injection molding resin is injected from the sprue 11 into the molded product cavity 3. After injecting and filling the molten resin into the molded product cavity 3, as shown in FIG. 2, only the support block 21 (core 4) is retracted while the inclined core 5 and the slide core 6 follow the fixed mold 1. And partially open the mold.

  When only the support block 21 is retracted while the inclined core 5 and the slide core 6 follow the fixed mold 1, the inclined core 5 and the slide core 6 are undercut of the molded product 7 molded in the molded product cavity 3. The portion 71 is fixed inward (in the upward direction in FIG. 2) with the protrusion 62 formed on the undercut portion inner surface molding surface 55 of the inclined core 5 and the outer surface molding surface 63 of the undercut portion 71 of the slide core 6. )

  Accordingly, since the undercut portion 71 of the molded product 7 is pulled inward and deformed, the support block 21 (core 4) is moved until the end of the molded product main body is inside the particle surface 14 of the fixed mold 1. .

  In this case, the distance until the end of the molded product main body is inside the particle surface 14 of the fixed mold 1 is the same as the depth of the stepped portion 13, but when the depth of the stepped portion 13 is increased, the molded product 7 is enlarged. If the deformation needs to be increased and the deformation is increased, the molded product 7 is destroyed during the mold removal, or even if the mold can be removed, it is difficult to return to the original shape. It is preferable that the depth is substantially the same as the thickness of the molded product 7 to be molded.

  Next, as shown in FIG. 3, the entire movable mold 2 is moved backward to open the mold. In this case, in the molded product 7, the undercut portion 71 is fixed by the undercut portion inner surface molding surface 55 of the inclined core 5 and the protrusion 62 formed on the outer surface molding surface 63 of the undercut portion of the slide core 6. Therefore, the end of the molded product main body is positioned inside the particle surface 14 of the fixed mold 1, and the mold can be opened without the end of the molded product main body contacting the particle surface 14 of the fixed mold 1.

  After opening the mold, as shown in FIG. 4, when the slide core 6 is separated from the inclined core 5 and retreated (rightward in FIG. 4), the projecting portion 62 comes off from the undercut portion 71 of the molded product 7. The undercut portion 71 of the molded product 7 is opened and recovered to the original shape.

  Finally, as shown in FIG. 5, the inclined core 5 is advanced until the tip of the undercut portion 71 of the molded product 7 is located outward from the inner cut surface 55 of the undercut portion of the inclined core 5. Take out.

  Further, an ejector device may be installed, and the ejector device may be driven to extrude the molded product 7 and release the mold.

  After demolding of the molded product is completed, the movable mold 2 is advanced, and the mold is closed as shown in FIG. 1, and thereafter, the steps as described above are repeated to obtain the molded product.

  As shown in FIG. 1, the particle surface 14 of the fixed mold 1 and the particle surface 64 of the slide core 6 of the movable mold 2 are positions where the outer surface of the undercut portion 71 of the molded product 7 of the molded product cavity 3 is formed. Since they are in contact with each other, the particle line is generated in the undercut portion 71 of the molded product having an undercut portion that bends inward at the end of the obtained molded product body.

  Therefore, as shown in FIGS. 6 and 7, when the undercut portion is formed so as to be a rolled portion 202 that bends inward to the foil arch portion 201 or a fender matching portion 204 that bends inside the fender portion 203, When this automobile bumper is assembled, the rolled part 202 and the fender mating part 204 are not visible from the outside, so the particle lines are not observed from the outside, and are beautiful and have excellent design properties. Is particularly preferably used as an automobile bumper.

It is sectional drawing which shows an example of the injection mold of this invention. The partial cross section which shows the state which partially opened the injection mold in the manufacturing method of the injection molded article which has the undercut part bent inside by the edge part of a molded article main body using the injection mold of this invention FIG. The partial cross section which shows the state which completed the mold opening of the injection mold in the manufacturing method of the injection molded article which has the undercut part bent inside by the edge part of a molded article main body using the injection mold of this invention FIG. In the method of manufacturing an injection molded product having an undercut portion that bends inward at the end of the molded product body using the injection mold of the present invention, the mold is completely opened and the slide block is moved backward. FIG. 6 is a partial cross-sectional view showing a state in which an undercut portion is free. In the method of manufacturing an injection molded product having an undercut portion that bends inward at the end of the molded product body using the injection mold of the present invention, the injection mold is completely opened and the slide core is advanced. FIG. 6 is a partial cross-sectional view showing a state where an injection molded product is taken out. It is a cross-sectional view which shows an example of the bumper for motor vehicles. It is AA sectional drawing in FIG. It is sectional drawing which shows an example of the conventional injection mold for injection-molding the molded article which has the undercut part bent inside at the edge part of the molded article main body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixed type | mold 11 Sprue 12 Molded article main body outer surface molding surface 13 Step part 14 Particle surface 2 Mobile mold 21 Support block 22 Through-hole 3 Molded product cavity 4 Core 41 Molded article main body inner surface molding surface 5 Inclined core 51 Inclined core main body 52 Support Member 53 Slide block 54 Molded product inner surface molding surface 55 Undercut part inner surface molding surface 6 Slide core 61 Tip surface molding surface of undercut part 62 Projection part 63 Outer molding surface of undercut part 64 Particle surface 65 Guide block 7 Molded product 71 Undercut section

Claims (6)

It consists of a fixed mold and a movable mold that can be opened and closed. A molded product cavity is formed when the mold is closed. A molded product with an undercut part that bends inward at the end of the molded product body is injection molded. An injection mold for performing
The movable mold has a core having an inner surface for molding the molded product body, an inner surface for molding the inner surface of the molded product body, and an inner molding surface for the undercut portion, and is slidably in contact with the side surface of the core. A tilted core that is movable, a tip surface forming surface of an undercut part, an outer surface forming surface and a particle surface of an undercut part, and an undercut part inner surface forming surface of an inclined core. On the other hand, it consists of a slide core that can move forward and backward,
The fixed mold has a molded product body outer surface molding surface, a step portion located outside the molding surface, and a particle surface located inward from the molding surface via the step portion,
When the mold is closed, the particle surface of the slide core and the particle surface of the fixed mold are brought into close contact with each other, and the core molded product inner surface molding surface, the inclined core molded product body inner surface molding surface and the undercut portion inner surface molding surface, A molded product cavity is formed by the tip surface molding surface of the undercut portion, the outer surface molding surface of the undercut portion, and the molded product outer surface molding surface and the step portion of the fixed mold. Injection mold.   The inclined core includes an inclined core body having an inner surface of the molded product body and an inner surface of the undercut part, a support member formed integrally with the inclined core body, and a slide block. 2. The injection mold according to claim 1, wherein the inclined core body is attached to the slide block so as to be movable and inclined inward.   3. The injection mold according to claim 2, wherein the slide core is installed in contact with the outer surface of the support member of the inclined core so as to be movable forward and backward.   4. The injection mold according to claim 1, wherein the depth of the step portion is substantially the same as the depth of the cavity for the molded product. A method for producing an injection-molded product having an undercut portion that bends inwardly at an end of a molded product body using the injection mold according to any one of claims 1 to 4 and comprising the following steps: .
(1) Closing the injection mold and injecting the injection molding resin into the molded product cavity. (2) With the undercut part of the molded product fixed, the inclined core and slide core are fixed. The process of partially retracting the movable mold until the end of the molded product body is inside the fixed mold particle surface while deforming the molded product while following it.
(3) a step of retracting the entire movable mold and opening the mold;
(4) separating the slide core from the inclined core, releasing the fixing of the undercut portion of the molded product, and releasing the deformation of the molded product; and
(5) Step of taking out the molded product   6. The method of manufacturing an injection-molded product having an undercut portion that bends inward at an end portion of the molded product body according to claim 5, wherein the injection-molded product is a bumper for an automobile.

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