JPS59209821A - Method for manufacturing a plastic molded product that has a roughly box shape - Google Patents

Abstract

PURPOSE:To make it possible to employ a resin with a low MFR suitable for vacuum forming, by compression molding a preform having a simple boxlike shape, and subjecting the preform to vacuum forming before the preform cools. CONSTITUTION:A preform (a) that has a simple boxlike shape with a gentle curved surface that is a little smaller than the intended item is molded by a compression mold (A) comprising bottom and top forces 1, 2. Then before the preform completely cools so that it may be still flexible enough and plastic, the forces 1, 2 are opened, the top force 2 with the preform (a) is immediately fitted in a vacuum forming bottom force 6 and they are closed. Successively, air is sucked from suction ports 9 to stuck the preform (a) onto the molding surface 8 of the vacuum forming bottom force 6 thereby forming it along the surface 8 into the final formed item (b).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to a method for manufacturing Hakoya's molded products, such as the inner box of a refrigerator. ◇ Generally, Hakoya's molded products, such as the inner box of a refrigerator, are made by vacuum forming thermoplastic synthetic resin. They are produced by injection molding or injection molding, but the former is mainly vacuum molded from ABS, HIPS, or hard PVC plates, and the wall thickness cannot be uniform, resulting in very thin parts. Polyolefin resins, which have low raw material prices, have poor vacuum formability compared to the above-mentioned resins, so they have drawbacks such as being unsuitable for deep drawing such as inner boxes.

Furthermore, the 7-lunge part that is to be connected to the outer box is stretched during molding, so it cannot be made to the required thickness, and the thickness is uneven, which can cause problems in connecting with the outer case. be.

On the other hand, the latter can be molded using relatively inexpensive resins such as polyolefin resin, and the wall thickness can be made uniform, but due to restrictions on the fluidity of the resin inside the mold, it is not possible to make the thickness below a certain thickness, and molding is possible. The cycle is also difficult, as in vacuum forming, for a short time of around 80 seconds, and it takes around 1 minute to cool down and take it out.

Also, while the former mold requires either a male or female aluminum mold and an auxiliary plug, the latter requires high pressure, so f! ! There are problems such as the need for male and female molds manufactured by i, which are expensive.

As a solution to the above problem,
There is one in Publication No. 76.

In the method disclosed in Japanese Patent Publication No. 57-127776, a preformed product having a simple shape similar to the inner box of a refrigerator is first molded by injection molding, and then the preformed product is molded into the preformed product before it has cooled down. The desired inner box is obtained by placing a vacuum-formed female mold in the shape of the inner box and adhering it to the inner surface of the mold.

However, according to this method, the molten resin is injected into the closed mold at one point or several points during the molding process of the preform, so if the fluidity of the resin at the melting temperature is not good, the molding will fail. It is difficult, especially when it comes to large box molded products such as refrigerator inner boxes, because the preformed products are also large.
R (Melt Fl ow Ratio) of about 10 must be used.

On the other hand, in the next step, when the preform is adsorbed or pressed onto the vacuum forming product, materials with a large MFH do not have good vacuum formability, making it difficult to make the wall thickness uniform, resulting in very thin parts. It is desirable to use a material with a low MFR.

Usually, MFRo, 5th to 3rd rank materials are used for vacuum forming.

Additionally, materials with a lower MFH generally have better impact resistance and cold resistance, and the molded product is also stronger.

However, when trying to mold a preformed product by injection molding using a material with a small MFH, resin must be press-fitted across many gates. The part where it collides, usually called the weld line, is created. This partial hole is not a desirable condition because the slightly cooled resin flowing from both sides collides with each other, and the composition is different from other parts, and the elongation of the vacuum molding in the next step is also different.

Furthermore, the temperature of the resin in the preformed product differs considerably between the portion near the gate and the end portion, which is also undesirable.

The present invention aims to solve the above problems, and the technical problem to be solved by the present invention is to form a preformed product by a molding method that can use a resin with a small MFH suitable for vacuum forming. It is to be.

The technical means taken by the present invention to achieve the above-mentioned technical problem is to mold a simple box-shaped preformed product, which is smaller than the target molded product and connected by a large curved surface, using a compression molding method. Before the preform has cooled down, a female mold for vacuum forming in the shape of the desired molded product is placed over it, and the preform is adsorbed to the molding surface of the female disc to form the final molded product. It is something to do.

The preformed product is molded using a compression molding method in which resin is put into male and female molds, and the resin is softened at high temperature and forced to flow into the disk by clamping the mold. The fluidity of the resin may be slightly worse than that of the injection molding method, and it is possible to use a resin with a small MFH suitable for the next step of vacuum forming. There is no temperature difference.

Hereinafter, an example of implementation of the present invention will be described based on the drawings.

This example is a method for manufacturing a roughly box-shaped plastic molded product that is an inner box of a refrigerator.
A simple box-shaped preform (a), which is smaller than the inner box of the target refrigerator and connected by large curved surfaces, is molded by compression molding.

The molds (4) for compression molding are female, male mattido, and die yoshinashi, which are each attached to a pressure press (not shown) to form a female W (
1) are placed facing each other vertically.

In addition, in this compression mold), the gap between the male and female molds (1) and (2) in the clamped state, that is, the molding part (3), is the final molded product, that is, the inner box of a refrigerator (b). It is small in size and is layered in a box shape with seven simple rungs connected by large curved surfaces, without any unevenness for forming shelf supports, etc.

The compression molding mold body) has female and male molds (1) (
2) In the open state, open the nozzle (4) of the extruder (B).
) The resin (c) is extruded into a sheet shape, and this is put into the cavity (5) of the female mold (1) while still at a high temperature, and the resin (c) is tightened with hydraulic pressure.

The resin (C) softened at high temperature flows through the mold and reaches every corner of the molding part (3), forming a preformed product (=
) is formed.

At this time, the resin (C) to be charged has the same weight as the inner box (b) of the target refrigerator, and its dimensions are smaller than the projected area of the inner box (b).

Therefore, it will not protrude beyond the 7 rung part during molding.

Next, the mold (IX2) is opened while the preformed product 0 has not completely cooled down and still has sufficient flexibility and fallability, and the mold (IX2) is opened with the preformed product (a) attached. The male mold (2) (due to resin contraction) is attached to the male mold (2), and the H shape (taken out from the blank) is immediately transferred to the female mold for vacuum forming ( 6) Insert and tighten the mold.

In this process, a female mold for compression molding and a female mold for vacuum forming (6) are arranged side by side on a horizontally movable surface plate (7), and after compression molding, a male mold is placed. At the same time as lifting the mold (2) upward and separating the molds, move the surface plate (7) sideways to move the female mold (6) for vacuum forming to just below the male mold (2), and insert the male mold into it. This can be done by lowering the mold (2), or by lowering the female mold (1) for compression molding as shown in Figures 7 and 8.
and a female mold (6) for vacuum forming are placed opposite to each other on both sides of the male mold (2), and after the compression molding is completed and the mold is opened, the male mold (2) is inverted. This is done by matching the female mold (6) for vacuum forming, and moving the female mold (6) forward to cover the male mold (2).

Although not shown in the drawings, the device is equipped with a female mold for compression molding and a female mold for vacuum forming arranged side by side on a surface plate, and a surface plate that rotates in opposition to this. By rotating this, the male mold is attached with the center of rotation shifted so that it can be moved from a position corresponding to the female mold for compression molding to a position corresponding to the female mold for vacuum forming. It is also possible. In this case, it goes without saying that either the surface plate with the male mold or the surface plate with the female mold can be moved forward and backward.

The molding surface (8) of the female mold (6) for vacuum forming is formed in the shape of the inner box of the intended refrigerator with unevenness (not shown) to serve as a shelf support, etc. Necessary suction ports (9) are provided at the locations, which communicate with a suction device (not shown) such as a suction vibrator.

In addition, this female mold for vacuum forming (6) and the male mold for compression molding (2) are arranged so that the 7-run molded parts α (b) of each mold are brought into contact with each other by tightening the fitting molds. It has become.

Therefore, the preformed product (→ 72nd part (b) is
) It will be in a state where it is clamped by the 7-rung molded parts (g) and (b) of (2).

Then, following the above process, the shear is sucked through the suction port (9) to attract the preformed product (-) to the molding surface (8) of the female mold (6) for vacuum forming and align it. Final molded product color)
to form.

At this time, since the 7 rung part (6) is sandwiched between the 7 rung forming part (6) (b), it will not be stretched by suction.

Finally, after the final molded product (color) has completely cooled and hardened, the mold (2) C6) is opened and taken out. Type (2
) was not released from the male mold (2) and moved on to the next process, but the preformed product (&) was released from the male mold (2) before being vacuum formed in the next process. female mold (6)
It is also possible to insert it inside.

In this case, as shown in FIGS. 9 to 11, the molding amount (■) for compression molding is determined by the male and female dies (1) (2) and the 7 Two ring-shaped molds for lunge forming (Llα→) are constructed into four divisible molds.
) and remove the preforms (→
While releasing the mold, two J101 for 7 lunge molding
Do not open α→, leave the 7th rung part (b) clamped and tightened, and set α→ in this mold to correspond to the 7th rung part (turn) of the female mold for vacuum forming (6). By setting the preformed product (=), the preformed product (=) is inserted into the female mold for vacuum forming (6) and vacuum forming is performed.

Since the present invention has the above configuration, it has the following advantages.

(1) It is possible to use a resin with a low MFR that is suitable for vacuum forming, and as a result, there are no parts where the vacuum forming special wall thickness is extremely thin, and the wall thickness can be made uniform. Of course, molded products with excellent impact resistance and cold resistance can be obtained.

(2) When the preforming step is performed by injection molding, there is no weld line, and the temperature of the resin is not partially uneven, and there is no risk of inconvenience in the next process, making it a good product. Vacuum forming can be expected.

(3) Energy-saving molding is possible without trimming loss.

(4) One drawback of vacuum forming, that the end portion of the molded product is sticky, can also be solved by thickening the end portion of the preform.

[Brief explanation of the drawing]

The drawings show one embodiment of the method for manufacturing a roughly box-shaped plastic molded product according to the present invention, and FIGS. 1 to 5 are cross-sectional views schematically showing the manufacturing process in order. The sixth factor is the final molding. A perspective view of the product, FIGS. 7 to 8 are cross-sectional views schematically showing other embodiments of the transition from the preform molding process to the next final molded product molding process, and FIGS. 9 to 11 are FIG. 7 is a cross-sectional view schematically showing still another embodiment. (=)...Preformed product (b)--Final molded product (1)...Female mold for compression molding (2)--Male mold (6)--Female mold for vacuum forming (8 )...Molding surface of female mold for vacuum forming Patent applicant Kodama Chemical Industry Co., Ltd.

Claims (1)

[Claims] In manufacturing plastic molded products that are approximately box-shaped,
A box-shaped preform, which is smaller than the desired molded product and has a simple shape connected by a large curved surface, is molded by compression molding, and before the preform has cooled, it is molded into the desired final shape. Cover this with a female mold for vacuum forming that has the shape of the product,
A method for manufacturing a plastic molded product having a roughly box shape, characterized by forming a final molded product by adsorbing a preform onto the molding surface of a female mold.