JPH07299847A - Production of thin-walled sheet like molded product - Google Patents

Abstract

PURPOSE:To produce a thin-walled sheet like molded product without generating warpage. CONSTITUTION:A molded product 10 wherein a plurality of thin-walled sheet like molded parts 12 are integrally connected at gate parts (resin cured in gates) 13 symmetric to a runner part (resin cured in a runner) 11 is produced by the injection molding of a resin and cooled to be taken out of a mold. The molded product 10 is pushed in the gap between a pair of the rod-shaped members 21, 21 of a jig 20 before the temp. of the center of the runner part 11 lowers to the temp. of the mold or lower and the thin-walled sheet like molded products 12 are bent in a line symmetric manner at the connection parts with the gate parts 13 at an angle of 45-135 deg. with respect to the runner part 11 and subsequently cooled perfectly to be cut off at the connection part with the gate parts 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thin-walled sheet-shaped molded article, and more particularly to a method for producing a thin-walled sheet-shaped resin molded article such as a housing for electronic products, automobile parts, lids, nameplates, films and plate materials.

[0002]

2. Description of the Related Art Conventionally, when manufacturing a thin-walled resin molded product as described above, a molding process such as injection molding or transfer molding, or a cutting process of a plate material is adopted. Injection molding is often used from the viewpoint of cost. When a thin sheet-like molded product is manufactured by injection molding, the thickness is 2 mm or less and the vertical length is 100 m.
When manufacturing a thin sheet-like molded product having a width of 20 mm or more and a width exceeding m, a plurality of cavities having the dimensions are symmetrically arranged with respect to the runner, and the long side portions of these plate-like cavities are wide or many. Using a mold that is in communication with the runner through a side gate or a film gate, the mold is filled with resin and molded, and after cooling, a sprue, a resin cured in the runner and the gate (in this specification, a sprue part, The runner portion and the gate portion) are integrally and continuously taken out from the mold to separate the molded product from the sprue portion and the like at the gate portion.

[0003]

However, in the above-mentioned manufacturing method, since the sheet-shaped molded product is thin, the thin-walled sheet-shaped molded product becomes thin due to residual stress and thermal stress when separated from the sprue portion. There is a problem that the sheet-shaped molded product is deformed such as warped.

Therefore, conventionally, as measures against the above-mentioned problems, the warp is corrected after the separation, the ribs are provided on the sheet-shaped molded product so that the warp does not occur, and injection compression is performed at the time of molding. Although such measures have been taken, there is a problem that the correction of the warp increases the man-hours and cannot be completely corrected. Providing the rib lowers the degree of freedom of the shape and reduces the wall thickness. This causes a problem that it becomes difficult, and performing the injection compression not only complicates the mold and the apparatus itself, but also causes a problem that burrs are likely to occur and a molding cycle becomes long. The present invention has been made in view of the above circumstances, and does not cause an increase in man-hours and costs, does not require a special device, and does not require a change in shape, and a sheet-shaped molded product. It is an object of the present invention to provide a manufacturing method capable of effectively preventing the occurrence of warpage.

[0005]

In order to achieve the above object, a method for manufacturing a thin-walled sheet-shaped molded article according to the present invention is such that a plurality of plate-shaped cavities symmetrically arranged with respect to a runner are wide or have a large number of cavities. Using a mold communicating through a side gate or a film gate, the plate-shaped cavity is filled with a resin through the runner and the gate to form a thin sheet-shaped molded product, and then the sheet-shaped molded product is cooled. After being taken out of the mold in a continuous state with the runner and the gate portion, the thin-walled sheet-shaped product was bent at 45 ° to 135 ° with the connecting portion of the gate as a fulcrum, and then the thin-walled sheet-shaped product was cooled. After that, the sheet-shaped molded product was separated.

In the method for manufacturing a sheet-shaped molded product according to the present invention, the thin-walled sheet-shaped molded product is bent until the temperature of the center of the runner portion falls to the mold temperature (claim 2). A mode in which the thin-walled molded product is bent so as to be line-symmetric with respect to the runner portion (claim 3), and a mode in which the sheet-shaped molded product is molded by injection molding (claim 4). Can be configured to.

[0007]

According to the method of manufacturing a thin-walled sheet-shaped molded article according to the present invention, after the thin-walled sheet-shaped molded article is taken out of the mold, the gate section is used as a fulcrum with respect to the runner section from 45 ° to 1 °.
It is bent at an angle of 35 °, preferably 60 ° to 120 °, cooled to a stable temperature in a state where the rigidity is large, and cut off when cooled to a stable temperature, so that occurrence of warpage or the like can be prevented. Therefore, the warp of the sheet-shaped molded product can be prevented without increasing the man-hours and costs, without requiring a special device, and without requiring a change in shape.

In the method for manufacturing a thin-walled molded product according to the present invention, the thin-walled molded product is bent by the time when the central temperature of the runner portion falls to the mold temperature. Item 2), and by bending the thin sheet-shaped molded product so as to be line-symmetric with respect to the runner portion (claim 3), it becomes possible to more effectively prevent warpage.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 are views for explaining a method for manufacturing a thin-walled molded product according to an embodiment of the present invention, FIG. 1 is a plan view of the molded product taken out from the mold, FIG.
Is a front view of the same molded product, FIG. 3 is a perspective view schematically showing a mechanism for bending the molded product taken out of the mold, FIG. 4a,
3B and 3C are front views showing bending of a molded product in time series.

In this embodiment, first, a molded product 10 shown in FIGS. 1 and 2 is molded by resin injection molding using a mold. Although not shown, the mold has a movable mold, a fixed mold, etc., and a plurality of plate-shaped cavities are defined symmetrically with respect to the runner by these molds, and the long side portion of each cavity is a plurality of film gates. To communicate with Lanna. Therefore, as shown in FIGS. 1 and 2, the molded product 10 has a plurality of thin-walled sheet-like resins 12 integrally connected to the runner portion 11 by three film-like gate portions 13 in a state of being taken out from the mold. is doing. In FIGS. 1 and 2, 14 is a resin for the sprue part.

The molded product 10 can be molded by transfer molding or the like, and the mold can be configured so that the cavity and the runner communicate with each other with a wide or multiple side gates. . further,
INDUSTRIAL APPLICABILITY The present invention is suitable for molding a thin-walled sheet-shaped molded product 12 having a thickness of 2 mm or less (particularly 1.5 mm or less) and a longitudinal dimension of more than 100 mm and a lateral dimension of 20 mm or more, but a thin-walled sheet-shaped molded article having a different dimension. It is also possible to apply to the production of 12.

After cooling the molded product 10 molded in the mold, it is taken out from the mold by using a robot (not shown),
Immediately after taking out, each thin-walled sheet-shaped molded product 12 of the molded product 10 is bent at the connecting portion with the gate portion 13 by using the jig 22 shown in FIG. The jig 20 is arranged on the conveyor 30 and includes a pair of rod-shaped members 21 and 21 provided at a predetermined interval so as to be orthogonal to the conveying direction of the conveyor 30.
Then, the robot grasps the sprue portion 14 of the molded product 10 and takes it out of the mold, and subsequently, as shown in FIGS. 4A, 4B and 4C, the thin sheet-shaped molded product 12 of the molded product 10 is moved to the jig 2
The rod-shaped member 2 so as to contact the rod-shaped members 21 and 21 of 0.
The thin-walled sheet-shaped molded product 12 is pushed between the first and second parts 21 and bent so as to be line-symmetric with respect to the runner part 11.

Here, it is desirable to bend the thin-walled sheet-shaped molded article 12 of the molded article 10 before the temperature of the central portion of the runner portion falls below the mold temperature. 45 ° to 135 with respect to part 13
It is bent at an angle θ of 60 °, preferably 60 ° to 120 °. The bending direction is not limited to the direction shown in FIG. 4 described above, but it can be bent as shown in FIGS. 5a and 5b, and as shown in FIG. 5c, the liner symmetry is opposite to that of FIG. 4 with respect to the runner portion 11. However, it is preferable to fold it in line symmetry (FIGS. 4 and 5c). Further, although the molded product 10 is taken out from the mold by the robot and the thin sheet-shaped molded product 12 is bent, it is also possible to bend the thin-walled molded product 12 manually by the operator. There is no end.

Next, when the molded product 10 is bent into the thin sheet-shaped molded product 12, the molded product 10 is released from the robot and drops onto the conveyor 30, and is conveyed to the collecting box by the conveyor 30 and stored therein. Then, after the molded product 10 is left to stand for a whole day and night in this collection box to be completely cooled, the thin sheet-shaped molded product 12 is separated from the runner portion 11 at the gate portion. Instead of natural cooling by leaving it standing, it is also possible to immerse it in cooling water and forcibly cool it with water.

As described above, in this embodiment, immediately after the molded product 10 is taken out from the mold, the thin-walled sheet-shaped molded product 12 is line-symmetrical to the runner portion 11 at the joint with the gate portion 13. Since the thin-walled sheet-shaped molded product 12 is cut after the molded product is completely cooled after being bent at an angle of 45 ° to 135 °, it occurs due to thermal stress or residual stress until the molded product 10 is completely cooled. Warpage can be prevented.

The thickness is 1.0 mm and the lateral dimension is 40.
mm, the vertical dimension is 220 mm, the thin-walled molded product is injection-molded as shown in FIGS. 1 and 2, and the thin-walled molded product is bent manually at different bending angles θ by a robot or completely cooled, and then separated. When the warpage of these thin-walled molded products was compared with the comparative example, the results shown in Table 1 were obtained, demonstrating that the present invention can effectively prevent the warpage.

[0017]

[Table 1]

In the above-mentioned embodiment, the molding of the molded product 10 having both flat surfaces is illustrated, but it can be applied to a molded product having a partially different thickness such as a groove on the front surface or the back surface. Nor. The present invention is particularly effective for such a molded article 10 having partial unevenness, in which the thickness including the height of the convex portion is 2 mm or less.

[0019]

As described above, according to the method for manufacturing a thin-walled sheet-shaped molded article according to the present invention, the thin-walled sheet-shaped molded article is joined to the gate portion at 45 ° or more immediately after being taken out from the mold. Bending at an angle of 135 °, and then, after cooling completely, the thin-walled sheet-shaped molded product was cut off, increasing man-hours and costs, changing the shape, and using no special device. The effect of effectively preventing warpage due to residual stress or thermal stress can be obtained.

In the method for manufacturing a thin-walled molded product according to the present invention, the thin-walled molded product is bent by the time when the central temperature of the runner portion falls to the mold temperature. Item 2) In addition, by bending the thin-walled sheet-shaped product so as to be line-symmetric with respect to the runner portion (Claim 3), it is possible to prevent warpage more effectively, and further employ injection molding. The cost is further reduced.

[Brief description of drawings]

FIG. 1 is a plan view of a molded product taken out of a mold in a method for manufacturing a thin-walled molded product according to an embodiment of the present invention.

FIG. 2 is a front view of the molded product.

FIG. 3 is a perspective view schematically showing a mechanism for bending the molded product.

FIG. 4 is a front view showing a bending process of the molded product in time series in the order of a, b, and c.

FIG. 5 is a front view showing another embodiment of the molded product in a bent state.

[Explanation of symbols]

 10 molded product 11 runner part 12 thin-walled molded product 13 gate part 14 sprue part 20 jig 21 bar-shaped member 30 conveyor θ bending angle

Claims (3)

[Claims] 1. A mold in which a plurality of plate-shaped cavities arranged symmetrically with respect to the runner communicate with each other through a wide or a large number of side gates or film gates, and the runner and the gate are provided in the plate-shaped cavity. After that, the resin is filled to form a thin sheet-shaped molded product, and after cooling, the thin-walled molded product is taken out of the mold in a continuous state with the runner and the gate portion, and the thin-walled molded product is used for the gate. 45 ° ~ 135 ° with connecting part as fulcrum
A method for producing a thin-walled molded article, which is characterized in that the thin-walled molded article is folded and then cut off after the thin-walled molded article is cooled. 2. The method for producing a thin-walled sheet-shaped product according to claim 1, wherein the bending of the thin-walled sheet-shaped product is performed until the temperature of the central portion of the runner portion falls to the mold temperature. 3. The method for manufacturing a thin-walled sheet-shaped article according to claim 1, wherein the thin-walled sheet-shaped article is bent so as to be line-symmetric with respect to the runner portion.