JPH05177697A - Mold for synthetic resin molded item and method for molding thereof - Google Patents

Abstract

PURPOSE:To mold surely and without thickness deviation a synthetic resin molded item with an undercut from a synthetic resin sheet. CONSTITUTION:A vacuum forming mold is constituted of the first forming mold 1 having an undercut part 1a on the mold face and the second forming mold 2 which has an approximate shape to the mold face and is fitted to the first forming mold so as to bring a synthetic resin sheet S under a plasticized condition into contact with or close to the mold face. As the first forming mold 1, an air-permeable mold vacuum-sucking the synthetic resin sheet S is used. A movable plug as a pushing mechanism is provided on the second forming mold 2 and the synthetic resin sheet S is pushed into the undercut part 1a by driving the movable plug by means of an air bag 8 and is brought into contact with the mold face of the part or is brought close thereto.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding die and a molding method for molding an undercut synthetic resin molded article from a synthetic resin sheet.

[0002]

2. Description of the Related Art Conventionally, for vacuum forming a synthetic resin sheet, a vacuum forming die comprising a breathable die and a plug die having a shape similar to its forming surface is used. A synthetic resin sheet in a plastic state is set between and, and the synthetic resin sheet is brought close to the molding surface by matching the breathable mold and the plug mold, and then the synthetic resin sheet is removed from the breathable mold. This is done by vacuum suction and bringing the molded surface into close contact.

[0003]

When molding a synthetic resin molded product having an undercut with this conventional apparatus, an undercut portion corresponding to this is provided on the molding surface of the breathable mold, but For convenience, the plug mold cannot be provided with a shape corresponding to the undercut portion, so that it is difficult to bring the synthetic resin sheet close to the molding surface of the undercut portion. When the undercut portion is shallow, the synthetic resin sheet and the molding surface of the undercut portion are not separated from each other so much that the synthetic resin sheet can be extended by the vacuum suction force and brought into close contact with the molding surface.

However, when the undercut is deep, the synthetic resin sheet and the molding surface are largely separated from each other, so that the synthetic resin sheet cannot be brought into close contact with the molding surface only by the vacuum suction force, and the predetermined undercut shape is obtained. Was not obtained. Further, even when the undercut portion is shallow, the synthetic resin sheet is stretched unevenly, so that the uneven thickness phenomenon is likely to occur, in which the wall thickness becomes thin especially at the corner portion and becomes thick at other portions.

Therefore, an object of the present invention is to provide a molding die and a molding method for a synthetic resin molded product, which can reliably mold a synthetic resin molded product having an undercut from a synthetic resin sheet without uneven thickness. is there.

[0006]

In order to solve the above-mentioned problems, the molding die of the synthetic resin molded product of the present invention comprises a first molding die having an undercut portion on the molding surface and a molding surface close to the molding surface. A second molding die that is fitted to the first molding die so as to bring the synthetic resin sheet having the above-mentioned shape and in a plastic state into contact with or close to the molding surface. The present invention is characterized in that a pushing mechanism for pushing into the undercut portion of the first molding die is provided.

Further, the method for molding a synthetic resin molded article according to the present invention is characterized in that the molding surface is provided between a first molding die having an undercut portion and a second molding die having a shape similar to the molding surface. ,
After setting the synthetic resin sheet in a plastic state, the first molding die and the second molding die are matched with each other, the synthetic resin sheet is brought into contact with or close to the molding surface, and the pushing mechanism provided in the second molding die. Is characterized in that the synthetic resin sheet is pushed into the undercut portion of the first mold.

Here, the "first mold" may be breathable or non-breathable. For example, when vacuum molding is performed from the first molding die, it may be breathable, but when pressure molding or press molding is performed by the second molding die, it may be breathable or non-breathable. Moreover, the following can be illustrated as a "pushing mechanism." A movable plug of a similar type to that which is moved back and forth to the undercut portion by driving means such as an airbag or an air cylinder. A rubber sheet that is inflated at the undercut by compressed air. A flexible plug made of a flexible elastic material that deforms with mold matching and enters the undercut portion. An elastic plate that is slid by the driving means and deforms at the undercut portion. A leaf spring that pushes a synthetic resin sheet into the corner of the undercut section.

[0009]

According to the molding die or molding method for a synthetic resin molded article of the present invention, since the pushing mechanism provided in the second molding die pushes the synthetic resin sheet into the undercut portion of the first molding die, an undercut The synthetic resin sheet is uniformly stretched inside and abuts or comes close to the molding surface, and by the vacuum molding, pressure molding, press molding, etc. at that time or thereafter, it is possible to ensure a predetermined underlayer without any uneven thickness. It is molded into a cut shape.

[0010]

Embodiments of the present invention embodied in a vacuum forming mold will be described below with reference to the drawings. 1 and 2 show a first embodiment of a vacuum forming die. The vacuum forming die comprises a first forming die 1 having an undercut portion 1a on its forming surface and a synthetic resin sheet S in a plastic state. It is composed of a second molding die 2 fitted to the first molding die 1 so as to come into contact with or come close to the molding surface.

The first molding die 1 comprises a breathable electroformed shell 9 produced in a shell shape by the electroforming method described in Japanese Patent Publication No. 2-14434 and a support frame for hermetically supporting the peripheral edge portion thereof. It consists of 4. The electroformed shell 9 is provided with a large number of air holes 3 for vacuum suction whose diameter is increased toward the back side, and an uneven pattern (not shown) such as leather grain is formed on the front side molding surface. A vacuum suction device (not shown) such as a vacuum pump is connected to the first mold 1.

The second mold 2 comprises a mold body 22 having a shape similar to the molding surface of the first mold 1, and a support frame 23 for supporting the peripheral edge thereof. A concave portion 5 is formed in a portion of the mold body 22 corresponding to the undercut portion 1a of the first molding die 1, and the concave plug 5 has a movable plug as a pushing mechanism for pushing the synthetic resin sheet S into the undercut portion 1a. 6 are accommodated. The movable plug 6 is made of a material having excellent slidability and heat resistance (for example, Teflon) or the like, and is formed into a shape similar to the undercut portion 1a. A spring 7 and an airbag 8 are provided on the back side of the movable plug 6,
The airbag 8 is connected to an external air supply / exhaust device (not shown). The movable plug 6 is configured to enter the undercut portion 1a by the inflation of the airbag 8 and return to the recess 5 by the tension of the spring 7.
As the synthetic resin sheet S, one having a thickness of 1 to 5 mm made of a thermoplastic synthetic resin such as vinyl chloride, vinylidene chloride, polyethylene and polypropylene is used.

Next, a method of vacuum forming a synthetic resin molded product using the above molding die will be described. First, the first molding die 1 and the second molding die 2 are opened, and the synthetic resin sheet S which has been plasticized by heating is set between them. Next, the two molding dies 1 and 2 are matched with each other, and the synthetic resin sheet S is pressed by the second molding die 2 to form the first molding die 1
Abuts or comes close to the molding surface other than the undercut portion 1a. Next, the airbag 8 is inflated by the supply of air, the movable plug 6 is projected, and the synthetic resin sheet S is pushed into the undercut portion 1a by the movable plug 6. Simultaneously with or after this, the synthetic resin sheet S is vacuum-sucked from the first mold 1 and adheres to the entire molding surface,
The uneven pattern provided on the molding surface is transferred to the synthetic resin sheet S.

Since the movable plug 6 has a shape similar to that of the undercut portion 1a, the synthetic resin sheet S is pressed in a wide area and uniformly stretched, and abuts against the molding surface of the undercut portion 1a. approach. Therefore, even if the undercut portion 1a is deep, the synthetic resin sheet S can be reliably vacuum-formed into a predetermined undercut shape without uneven thickness. Further, since the breathable electroformed shell 9 having the vent hole enlarged in the middle is used as the first molding die 1, a strong vacuum suction force can be obtained, and the uneven pattern can be clearly transferred to the synthetic resin sheet S. You can

After a lapse of a predetermined cooling time, the air in the airbag 8 is released, the airbag 8 is contracted by the tension of the spring 7, and the movable plug 6 is returned to the recess 5. Then, the two molds 1 and 2 are opened, and the synthetic resin molded product is released from the first mold 1. In the vacuum forming die of the first embodiment, the second forming die 2 is provided with a compressed air passage opening toward the undercut portion 1a, and the synthetic resin sheet S is formed by the compressed air from the compressed air passage. You may comprise so that it may be pressed more strongly. Further, as a means for driving the movable plug 6, an airbag 8 is used.
Alternatively, an air cylinder can be used.

FIGS. 3 and 4 show a second embodiment of the vacuum forming mold, and the same parts as those in the first embodiment are designated by the same reference numerals. Explaining only the difference, in the second embodiment, the rubber sheet 10 is used as the pushing mechanism, and the rubber sheet 10 is provided so as to cover the molding surface of the second molding die 2. A compressed air passage 11 is formed in the second mold 2, and the rubber sheet 10 is expanded by the compressed air from the compressed air passage 11 so that the synthetic resin sheet S is pushed into the undercut portion 1a. Therefore, according to this embodiment, the relatively inexpensive rubber sheet 10 can be used to bring the synthetic resin sheet S into close contact with the molding surface of the undercut portion 1a without any gap.

FIGS. 5 and 6 show a third embodiment of the vacuum forming die, in which the second forming die 2 is provided with a flexible plug 13 as a pushing mechanism. The flexible plug 13 is formed of silicon rubber or the like in a shape corresponding to the undercut portion 1a. And both molds 1,
At the time of mold matching of 2, the flexible plug 13 is deformed following the shape of the undercut portion 1a, and the synthetic resin sheet S is pushed into the undercut portion 1a. Therefore,
Also according to the third embodiment, the synthetic resin sheet S can be accurately formed into a predetermined undercut shape with an inexpensive structure. In the case of an undercut having a complicated shape, the flexible plug 13 may be provided with a compressed air ejection hole so that the synthetic resin sheet S is pressed against the molding surface by compressed air.

7 to 9 show a modification of the flexible plug 13 in the third embodiment. The flexible plug 13 shown in FIG. 7 has a compressed air passage 14 therein, and the flexible plug 13 is expanded by compressed air inside the undercut portion 1a, so that the synthetic resin sheet S is formed on the molding surface of the undercut portion 1a. It is configured so that it can be in close contact without a gap. The flexible plug 13 of FIGS. 8 and 9 includes two compressed air passages 14, and as shown in FIG. 8, when compressed air is supplied to both of the compressed air passages 14, the entire structure expands. As shown, when compressed air is supplied to only one of the compressed air passages 14, it is inclined to one side. According to this, one flexible plug 13 can be deformed according to the shape of the undercut portion 1a. It is also possible to embed a shape memory alloy in the flexible plug 13 and cool and heat it to add a shape deforming function to the flexible plug 13.

FIG. 10 shows a fourth embodiment of a vacuum forming die, in which an elastic plate 16 is used as a pushing mechanism. The elastic plate 16 is formed of an elastic material such as silicon rubber having excellent slidability and heat resistance, and one end of the elastic plate 16 is formed of a second material.
It is fixed to the surface of the molding die 2, the other end is slidably inserted into the second molding die 2, and the insertion end is connected to an actuator (not shown) such as an air cylinder via a wire. The second molding die 2 is provided with a guide protrusion 17, and the elastic plate 16 is deformed along the guide protrusion 17 in the undercut portion 1a to push the synthetic resin sheet S into the undercut portion 1a. ..

11 and 12 show a fifth embodiment of the vacuum forming die, in which the first forming die 1 is provided with a mushroom-shaped undercut portion 1a. A support rod 19 for supporting the synthetic resin sheet S and two leaf springs 20 as a pressing mechanism are fixed to the second mold 2, and an operating rod 21 for deforming the leaf spring 20 is slidably provided. There is. Then, the operating rod 21 is connected to an air cylinder (not shown).
Each leaf spring 20 is opened to the outside by pulling it down with the like, and the synthetic resin sheet S is pushed into the corners of the undercut portion 1a by the tips thereof. Therefore, according to this configuration, in particular, the corner of the synthetic resin sheet S is formed by the leaf spring 20 with an accurate thickness,
Unlike the conventional case, there is no fear that the thickness of this portion will be thin. In this embodiment, if compressed air is also used, the portion of the synthetic resin sheet S other than the corners is undercut portion 1.
It can be brought into close contact with the molding surface of a.

The present invention is not limited to the configuration of the above-mentioned embodiment, and can be embodied by appropriately changing it without departing from the spirit of the invention.

[0022]

As described in detail above, according to the present invention,
Since the pushing mechanism for pushing the synthetic resin sheet into the undercut portion is provided, an excellent effect that a synthetic resin molded product having an undercut from the synthetic resin sheet can be reliably molded without uneven thickness is obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a vacuum forming mold showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the molding die of FIG. 1 during undercut molding.

FIG. 3 is a sectional view of a vacuum forming die showing a second embodiment of the present invention.

FIG. 4 is a cross-sectional view showing the molding die of FIG. 3 during undercut molding.

FIG. 5 is a sectional view of a vacuum forming die showing a third embodiment of the present invention.

FIG. 6 is a cross-sectional view showing the molding die of FIG. 5 during undercut molding.

FIG. 7 is a sectional view showing a modification of the flexible plug of the third embodiment.

FIG. 8 is a cross-sectional view showing another modification of the flexible plug of the third embodiment.

9 is a cross-sectional view showing different operating states of the flexible plug of FIG.

FIG. 10 is a sectional view of a vacuum forming die showing a fourth embodiment of the present invention.

FIG. 11 is a sectional view of a vacuum forming die showing a fifth embodiment of the present invention.

FIG. 12 is a cross-sectional view showing the molding die of FIG. 11 during undercut molding.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 1st shaping | molding die 1a Undercut part 2 2nd shaping | molding die 6 Movable plug 10 Rubber sheet 13 Flexible plug 16 Elastic plate 20 Leaf spring S Synthetic resin sheet

Claims (2)

[Claims] 1. A first molding die having an undercut portion on a molding surface and a first molding for bringing a synthetic resin sheet in a plastic state having a shape similar to the molding surface into contact with or close to the molding surface. A second molding die that is fitted to the mold, wherein the second molding die is provided with a pushing mechanism that pushes the synthetic resin sheet into the undercut portion of the first molding die. Mold of. 2. After a synthetic resin sheet in a plastic state is set between a first molding die having an undercut portion on the molding surface and a second molding die having a shape similar to the molding surface,
The first molding die and the second molding die are matched with each other, the synthetic resin sheet is brought into contact with or brought close to the molding surface, and the synthetic resin sheet is under-applied to the first molding die by the pushing mechanism provided in the second molding die. A method for molding a synthetic resin molded product, which comprises pressing into a cut portion.