JPH09150451A - Plastic product molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enabled mold release whereever an undercut part is located and to simplify and to miniaturize the structure of a mold by performing mold release while front and back split molds are elevated when the mold release is performed. SOLUTION: A mold is constituted of a central mold 5a and a front split mold 5b and a back split mold 5c divided along a tapered line L being widened downward at parts of a bonnet and a rear window. In addition, the front and back split molds 5b and 5c are constituted in such a way that they are elevated in parallel to the tapered line L by an air cylinder 6 arranged on the back face of a base 2. Then, after a sheet is brought into close contact with the whole periphery of the mold and is solidified, when the front and back split molds 5b and 5c are elevated in parallel to the tapered line L by means of the air cylinder, as the interval between the front and back split molds 5b and 5c is narrowed, mold release can be performed by releasing the front and back split molds 5b and 5c from an undercut part of a model car.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a plastic product such as a model car made of plastic, particularly a product having an undercut portion by vacuum forming.

[0002]

2. Description of the Related Art A conventional vacuum forming method for a plastic molded product such as a model car will be described. In the vacuum forming method, a thermoplastic resin sheet is fixed to an upper mold, and in a state where the sheet is heated and softened by a heater, a convex mold on a lower mold is pushed up to perform pre-elongation, and then the lower mold is formed under vacuum. It is a method of sucking and molding into a mold.

In the vacuum forming method described above, it is easy to release a molded product without undercuts. However, in the case of a molded product with undercuts such as a bumper of a model car, Due to the difficulty of mold release, the lower mold is divided into a plurality of parts so that mold release is facilitated.

FIG. 3 shows a mold for molding a conventional model car having an undercut. The mold is a central mold 1a and a block-shaped front split mold located at front and rear bumpers of the central mold 1a. 1b and rear split mold 1c. The two split molds 1b and 1c can release the model car from the mold by sliding the base car 2 in the direction of arrow b after the vacuum forming.

FIG. 4 shows another conventional mold. This mold is composed of a central mold 3a, a front mold 3b and a rear mold 3c, which are divided along a tapered line narrowing upward at a bonnet and a rear window. Then, the center mold 3a is lowered as shown by the arrow a after vacuum forming by the air cylinder 4 arranged on the lower surface of the base 2, and then the front / rear split molds 3b and 3c are slid in the direction of the arrow b, whereby the model car is moved. It can be released from the mold.

[0006]

In the former mold of the prior art described above, in the case of a model car having an undercut portion 1a 'as shown by an imaginary line above the bumper behind the model car, There has been a problem that division by the post-split type 1c becomes impossible.

Also, with the latter lower mold, it is possible to manufacture a model car having the above-mentioned undercut 1a ', but it is necessary to lower the central mold 3a, so There is a problem that the structure becomes complicated and a large molding machine is required to lower the central mold 3a by a considerable amount.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to make it possible to release a mold regardless of an undercut portion at any position, and to simplify the structure of a mold. Another object of the present invention is to provide a method of molding a plastic product which can be reduced in size and can prevent abrasion of a rubbed portion during movement of a split mold.

[0009]

DISCLOSURE OF THE INVENTION The method for molding a plastic product of the present invention achieves the above-mentioned object.
The means is a method of forming a plastic product by pre-expanding a heat-softened plastic sheet and then sucking it into a mold by vacuum, and dividing the mold by a central mold and a taper line expanding downward. Front and rear split type,
It is characterized in that the front-rear split mold is configured to be lifted along the taper line, and at the time of mold release, the front-rear split mold is lifted and released.

Further, it is desirable that the means for raising the front-and-back split die is to raise in a direction away from the central die.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A mold for carrying out a method for molding a plastic product (model car) according to the present invention will be described below with reference to FIG. The mold of the present invention has a central mold 5
a and a front split mold 5b and a rear split mold 5c which are divided along a linear taper line L that widens downward in the bonnet and the rear window. The front and rear split dies 5b and 5c are configured to rise in parallel with the tapered line L by an air cylinder 6 arranged on the back surface of the base 2.

Next, a method of forming a model car using the above-described mold will be described. In the same manner as in the conventional vacuum forming method, the heat-softened sheet is lowered onto a mold, pre-elongated, and then vacuum-formed by sucking air from a hole penetrating to a surface formed in the mold.

Then, after the sheet is in close contact with the entire circumference of the mold and is solidified, the front and rear split dies 5b and 5c are raised in parallel with the taper line L by the air cylinder (arrow a). , 5c is narrowed, so that the front and rear split molds 5b, 5c can be released from the undercut portion of the model car to perform mold release.

In the above-mentioned mold, front and rear split molds 5b, 5
Since the center mold 5a and the front and rear split molds 5b and 5c are in sliding contact with each other along the taper line L when the c moves up and down, the sliding surface of a commonly used aluminum mold is worn by long-term repeated molding. I do.

Therefore, in the present embodiment, as shown in FIG. 2, the air cylinder 6 for vertically moving the front and rear split molds 5b and 5c is changed in angle from the taper line L, that is, the taper line. Installed at a steeper slope than L.

In this way, the air cylinder 6 is attached to the taper line L.
Since the molds 5b and 5c are not parallel to each other but rise in a direction away from each other, the front and rear split molds 5b and 5c gradually separate from the central mold 5a as they rise and do not come into sliding contact with each other. It can be prevented.

[0017]

As described above, according to the present invention, the central mold and the front-rear split mold are divided by the taper line, and the front-rear split mold is slid with respect to the central mold so that the space between the front and rear split molds is narrowed. Since the load on the cylinder that moves the front-rear split mold up and down is small, a small cylinder can be used. Moreover, since the front-rear split mold only projects above the base, it is not necessary to make the base so large. Therefore, the molding apparatus can be downsized.

Further, since the ascending / descending portion of the front / rear split mold is moved in a direction away from the central mold so that the sliding contact surface does not come into contact with the central mold, the sliding contact time between the central mold and the front / rear split mold is shortened. It has the effect of preventing abrasion and improving the service life.

[Brief description of the drawings]

FIG. 1 is a side view of a mold for performing a plastic product molding method according to the present invention.

FIG. 2 is a partial side view showing another embodiment.

FIG. 3 is a side view of a conventional mold.

FIG. 4 is a side view of another conventional mold.

[Explanation of symbols]

 1 Model car (plastic product) 5a Central type 5b Front split type 5c Rear split type 6 Air cylinder L Tapered wire

Claims (2)

[Claims] 1. A method for forming a plastic product by pre-expanding a heat-softened plastic sheet and then sucking it in a mold in a vacuum, wherein the mold is composed of a central mold and a taper line expanding downward. It is composed of a front and rear split mold which is divided and a means for raising the front and rear split mold along the taper line, and at the time of mold release, the front and rear split mold is lifted and released. Molding method for plastic products. 2. The method for molding a plastic product according to claim 1, wherein the means for raising the front-rear split die is configured to raise in a direction away from the central die.