JPH05329924A - Method of forming resin sheet - Google Patents

Abstract

PURPOSE:To make easily the thickness of a formed article uniform even in the case of the formed article having recesses and protrusions. CONSTITUTION:A quadrangular sheet S to be formed, which is used for forming an article, is divided into a sheet forming region S1 for forming the article and useless sheet regions S2, S3, which are to be separated from the formed article after forming, on the basis of a design specifications of an to be formed. Of the useless sheet regions, the useless sheet region S3 corresponds to a cavity at the top of a deep drawing portion of the formed article. A slit SL1 is formed at the central part of the useless sheet region S3 corresponding to the cavity, while slits SL2 are formed in the useless sheet region S2 at the side parts of a folding portion of slant face parts of the formed article, prior to forming. Thereafter, when the plug-assist vacuum forming is performed, a pressing force generated by the downward movement of a plug works on the slit SL1 to open it, so that the force, which causes the extension of the resin sheet in the sheet forming region S1, is not applied thereto.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin sheet molding method for forming a molded article by following the unevenness of a molding die with the resin sheet in vacuum molding.

[0002]

2. Description of the Related Art Vacuum forming is often used as a method for shaping a thermoplastic resin sheet (hereinafter simply referred to as "resin sheet") into a desired shape. Vacuum forming
In this method, the resin sheet is heated and softened to be sucked by a predetermined suction die so that the resin sheet follows the irregular shape of the suction die to form a molded body.

By the way, the part of the suction type where the unevenness is remarkable is
The resin sheet receives a stronger tensile force than other parts of the suction type. For this reason, in the obtained molded product, the wall thickness of the portion having severe irregularities becomes thinner than the other portions. When such a situation occurs, the thin-walled portion is inferior in rigidity and is damaged, or a uniform soft feeling cannot be obtained due to the uneven thickness, and the product quality deteriorates.

In order to solve these problems, the following measures have hitherto been taken. In order to ensure the softness and rigidity required for the product quality even in the portion where the wall thickness is thin, the wall thickness of the resin sheet itself used has been made extra thick. Alternatively, JP-A-53-13
As can be seen in No. 3270, the wall thickness of the resin sheet is also locally changed in correspondence with the uneven portion of the vacuum forming suction mold. According to this latter method,
Even when using a suction type with locally significant unevenness,
It is possible to keep the thickness of the resin sheet molded body substantially uniform. In addition, in the obtained molded body, the portion where the wall thickness is thin is a deep-drawn portion or a corner portion of the molded body.

[0005]

However, the following problems have been pointed out even with the above-mentioned conventional methods. With the method of increasing the thickness of the resin sheet itself in advance, the soft feeling of the thin part is improved compared to before such measures, but the softness is uniform over the entire molded body. I can't get the feeling. Further, since the entire resin sheet to be molded becomes thick, the weight, the amount of the resin material used, and the cost increase.

On the other hand, in the method of locally changing the wall thickness of the resin sheet, the above-mentioned increase in weight and the like can be avoided, but the wall thickness change must be accurately corresponded to the concave and convex portions of the suction type. I have to. That is, it is difficult to control the thickness of the resin sheet before molding. The above-mentioned vacuum forming is generally a plug-assisted vacuum forming in which a plug is used together in order to enhance the shaping property of the sheet, but the above-mentioned problems are not limited to such vacuum forming, and a resin sheet is also used. It was a common problem in molding.

The present invention has been made in order to solve the above-mentioned problems in the prior art, and a method for molding a resin sheet which is easy to make the thickness uniform even in the case of a molded article having uneven portions. The purpose is to provide.

[0008]

The procedure adopted by the present invention in order to achieve the above object is a resin sheet molding method for molding a molded article by causing the resin sheet to follow the irregularities of a molding die. A resin sheet in a sheet forming region of a range forming a molded body is expanded by following the irregularities of the molding die, and an unnecessary sheet in a range separated from the molded body after molding in the vicinity of the sheet forming region of the stretched part. When there is a region, an opening that is opened by the force of stretching the resin sheet in the sheet forming region may be formed in advance in the unnecessary sheet region before the resin sheet in the sheet forming region is stretched. The summary will be given.

[0009]

The resin sheet used for molding the molded body can be distinguished into a sheet forming region which forms the molded body and an unnecessary sheet region which is separated after the molding. In the method of molding a resin sheet having the above structure, the resin sheet in the sheet forming area is expanded by following the irregularities of the molding die, and when there is an unnecessary sheet area in the vicinity of the sheet forming area of the expanded part, Acts like.

That is, the opening formed in advance in the unnecessary sheet area is opened by the force of extending the resin sheet in the sheet forming area, and this opening is formed before the resin sheet in the sheet forming area is extended. .. Therefore, it is possible to avoid applying a force to the resin sheet in the sheet forming area to the resin sheet, and the opening portion in the unnecessary sheet area is opened. As a result, the resin sheet in the sheet forming area is not expanded by the amount of the opening.

[0011]

EXAMPLES Next, preferred examples of the method for molding a resin sheet according to the present invention will be described with reference to the drawings. First,
A molded product obtained by the resin sheet molding method of the example will be described. As shown in FIG. 1A, the molded body W is
The flat resin sheet is bent to have a shape in which the lower stage side plane H1 and the upper stage side plane H2 are connected to each other, and the lower stage side plane H1 is provided with the deep drawing portion W0. Then, I in FIG.
As shown in FIG. 1 (b) which is a cross-sectional view taken along the line I, a hole W1 is formed at the top of the deep drawn portion W0.

The resin sheet for molding the molded body W is
A sheet material formed of a thermoplastic resin material such as polypropylene or polyvinyl chloride to a uniform thickness. In order to mold the molded body W having the above-mentioned shape using this resin sheet, a quadrangular sheet S to be molded as shown in FIG. 2 is prepared. The area surrounded by the alternate long and short dash line in the figure is the sheet forming area S1 used for forming the molded body W. On the other hand, the range distinguished from the sheet forming area S1 by the diagonal lines is the unnecessary sheet area separated from the molded body W after molding, and the unnecessary sheet area S2 outside the sheet forming area S1 and the unnecessary sheet inside the sheet forming area S1. There is a region S3. Of these, the unnecessary sheet area S3 corresponds to the punched hole W1 at the top of the deep drawing portion W0.

Next, a molding apparatus for vacuum forming the molded body W from the sheet S to be molded will be described. Figure 3
The molded sheet S (resin sheet) is the upper clamp 101.
Is held between the upper clamp 101 and the lower clamp 102, and the upper clamp 101 and the lower clamp 102 are supported by a support mechanism 103. The forming apparatus 100 also includes a heating device 200 and a vacuum forming device 300. The heating device 200 includes an upper heater 210 and a lower heater 220, and heats the upper surface and the lower surface of the sheet S to be molded, respectively. Also, the vacuum forming device 3
00 is an upper molding part 310 having a vertically movable plug.
And a lower molding part 320 having a lower suction mold for sucking and shaping the sheet.

The heating device 200 and the vacuum forming device 300
Is the support mechanism 1 by each drive device (not shown).
Go back and forth against 03. Then, when driven by the support mechanism 103, the heating device 200 includes the upper heater 210 and the lower heater 220, and the vacuum forming device 300 includes the upper forming part 310 and the lower forming part 320, respectively. Move it up or down.

Next, a process of forming the molded body W from the sheet S to be molded will be sequentially described. Since the shape of the molded body W is already known at the design stage, the sheet S to be molded S
The sheet forming area S1 and the unnecessary sheet area S2 can be distinguished before forming. Further, since the positions of the deep drawn portion W0 and the punched hole W1 in the molded body W are already known at the designing stage, the sheet forming area S1 of the unnecessary sheet area S3 corresponding to the punched hole W1 and, by extension, the target area. The position on the molding sheet S is also specified before molding. Furthermore,
A slope H that connects the lower plane H1 and the upper plane H2
3 is also specified.

From these things, in the first step in the forming process of the formed body W, as shown in FIG. 2, the slits SL1 and SL2 are formed in the unnecessary sheet region S3 and the unnecessary sheet region S2 of the sheet S to be molded. .. The slits SL1 and SL2 have the following relationships with the unnecessary sheet area S3 and the unnecessary sheet area S2, respectively.

The slit SL1 is formed in the unnecessary sheet area S3,
That is, it is located at the center of the punching hole W1 punched after the molding of the molded body W, and is formed as a crossed slit as shown in the drawing. In forming the slit SL1, it is taken into consideration that the tip of each cross-shaped slit does not reach the boundary between the unnecessary sheet area S3 and the sheet forming area S1. The slit SL2 connects the lower-side flat surface H1 and the upper-side flat surface H2 of the molded body W with an inclined surface portion H3.
Is formed in the unnecessary sheet area S2 so as not to reach the boundary with the sheet forming area S1 at the side of the sheet forming area S1 in the range corresponding to the bent portion. The slits SL1 and SL2 are formed at the time of forming the sheet S to be molded by the upper clamp 101 and the lower clamp 102.
It does not matter before or after the clamp. Further, it may be before forming by the vacuum forming apparatus 300 described later.

After the sheet S to be molded having the slits SL1 and SL2 formed therein is clamped, the heating device 200 moves up and down the sheet S to be molded. Then, the upper heater 210 and the lower heater 220 of the heating device 200 heat the sheet S to be molded to a predetermined temperature to soften it.

When the heating process is completed, the heating device 200 retracts, and instead the vacuum forming device 300 causes the sheet S to be formed.
It moves to the upper and lower positions. And the upper molding part 31
The plug-assisted vacuum forming is performed by the 0 plug and the lower suction die of the lower forming unit 320. Since this vacuum forming is well known, its detailed description is omitted.
Only the points related to the gist of the present invention will be described.

First, the formation of the deep drawn portion W0 will be described. As shown in FIG. 4, the plug 31 of the upper molding part 310
1 is lowered toward the lower suction mold 321. When the plug 311 continues descending in this manner, the sheet S to be molded in the range forming the top surface of the plug 311 and the deep drawing portion W0.
And the sheet S to be molded in the above range is already heated and softened, so that the sheet S to be molded is bent by the pressing force caused by the lowering of the plug 311. The state of the slit SL1 at this time will be described with reference to FIGS. 5A and 5B in which the periphery of the slit SL1 is viewed from the direction of arrow A in the drawing.

That is, before the plug 311 is lowered, as shown in FIG.
As shown in FIG. 5A, the slit SL1 that was just crossed in a cross shape is also pressed by the downward movement of the plug 311 on the slit SL1.
As shown in FIG. That is, the slit S
L1 gradually opens when receiving a pressing force due to the drop of the plug 311.

Next, as shown in FIG. 6, the plug 311 is lowered to the bottom dead center, and the plug 311 and the lower suction die 32 are placed.
With 1, the mold sheet S is clamped. By this mold clamping, the slit SL1 including the opening region is airtightly sealed by the top surface of the plug 311 and the bottom surface of the recess of the lower suction mold 321. That is, the lower suction mold 3 described later
Avoid air leakage during suction from 21. The slit SL1 in this mold clamping state is as shown in FIG.
In the open state further opened from the open state shown in (b), the plug 311 and the lower suction mold 321 are airtightly held.

After completion of the mold clamping described above, vacuum suction from the lower suction mold of the lower molding section 320 is started as indicated by an outline arrow in FIG. 6, and the vacuum suction is continued for a predetermined time. By the vacuum suction from the lower suction mold 321, the sheet S to be molded is sucked by the mold and the lower suction mold 3
21 Adhere to the surface.

Further, similarly to the above-mentioned formation of the deep-drawn portion W0, the sheet S to be formed in the range forming the slope portion H3 has the same shape.
The pressing force by the plug 311 acts. Therefore, the slit SL2 formed in the unnecessary sheet region S2 on the side of the bent portion in the vicinity of the slope portion H3 opens in a V shape with the sheet end portion as an opening portion.

Then, the sheet S to be molded is shaped by vacuum suction / pressing for a predetermined time to form a molded body W. After that, the vacuum forming apparatus 300 is retracted, and the unnecessary sheet area S3 including the opened slit SL1 is punched out from the sheet forming area S1 (formed body W) by a punching device (not shown), and the deep drawn portion W0 of the formed body W is cut. A hole W1 is formed at the top. The unnecessary sheet area S2 including the slit SL2 is trimmed and separated from the sheet forming area S1 (molded body W).

As described above, in the resin sheet molding method according to this embodiment, in the unnecessary sheet area S3 corresponding to the hole W1 formed at the top of the deep-drawn portion W0 of the molded body W,
The slit SL1 is formed in advance. Then, the force for extending the slit SL1 to the resin sheet at the deep drawing portion W0 forming portion in the sheet forming area S1, that is, the plug 311.
The opening was made by the pressing force that accompanies the descent.

Therefore, the slit SL1 is opened without applying a force for extending the resin sheet in the sheet forming area S1 to the slit SL1.
The resin sheet in the sheet forming region S1 is not extended by the amount of opening. As a result, according to the method of molding the resin sheet according to the present embodiment, even in the molded body W having the deep-drawn portion W0, the corners of the deep-drawn portion W0 have a thickness due to the elongation of the resin sheet. Does not cause unevenness. Moreover, such uniformization of the wall thickness of the molded body W can be realized by a simple method of previously forming the slit SL1 in the unnecessary sheet region S3. Further, even in the range of the sheet to be molded S forming the slope portion H3, it is possible to make the wall thickness uniform in this range by not applying a force to extend the same.

The present invention is not limited to the above-described embodiments, but can be carried out in various modes without departing from the scope of the invention, and the following modifications can be made.

In the above embodiments, the case where a single resin sheet is shaped to obtain the molded body W has been described. However, a skin resin sheet that serves as a skin layer and a base resin sheet that serves as a base thereof are laminated. It can also be applied to the case where a two-layer resin sheet is shaped to obtain a molded body. Further, it can be applied not only to a three-layer resin sheet having a cushion layer between a skin layer and a base but also to a multilayer resin sheet having more layers than this.

In the above embodiment, the resin sheet is shaped by vacuum molding, but it may be shaped by using another molding method such as press molding.

In the above-described embodiment, the slit for linearly dividing the resin sheet is formed, but in the molding process of the molded body W, the slit is opened prior to the expansion of the resin sheet in the sheet forming region to form the resin sheet in the sheet forming region. Any shape may be used as long as it does not apply a force for stretching it. For example, as shown in FIG. 8, a plurality of through holes may be formed so as to be arranged in a row with a slight interval left therebetween. Further, although the slit SL1 in the above-described embodiment and the through hole in FIG. 8 are arranged in a cross shape, the shape is not limited to this. For example, a shape intersecting with a * shape may be used.

[0032]

As described above, according to the method for molding a resin sheet of the present invention, an opening formed in advance in an unnecessary sheet area separated after molding is used to form a sheet forming area in a molding process of a molded body by a molding die. The resin sheet is opened prior to extension. Therefore, the resin sheet in the sheet forming area is not stretched, and the resin sheet in the sheet forming area is not elongated by the amount of the opening. As a result, the unevenness of the wall thickness due to the elongation of the resin sheet does not occur even if the unevenness is present in the molded body. Therefore, according to the molding method of the resin sheet of the present invention, the wall thickness of the molded body is made uniform. Can be realized by a simple method of forming an opening in the unnecessary sheet area in advance.

[Brief description of drawings]

FIG. 1 is an explanatory view for explaining a shape of a molded body W obtained by a resin sheet molding method of an example.

FIG. 2 is an explanatory diagram for explaining the shape of a sheet S to be molded used for molding a molded body W.

FIG. 3 is a conceptual diagram showing a configuration of a molding apparatus that molds a resin sheet by applying an embodiment of the present invention.

FIG. 4 is an explanatory diagram for explaining how the deep-drawn portion W0 of the compact W is formed.

FIG. 5 is an explanatory diagram for explaining a state of an opening of a slit SL1 when forming a deep drawing portion W0 of the molded body W.

FIG. 6 is an explanatory diagram for explaining how the deep drawn portion W0 of the compact W is formed.

FIG. 7 is an explanatory diagram for explaining the state of the opening of the slit SL1 when forming the deep drawn portion W0 of the molded body W.

FIG. 8 is an explanatory diagram for explaining a modified example of the slit SL1 in the embodiment.

[Explanation of symbols]

 100 ... Molding device 103 ... Supporting mechanism 200 ... Heating device 300 ... Vacuum molding device 310 ... Upper molding part 311 ... Plug 320 ... Lower molding part 321 ... Lower suction mold H1 ... Lower stage side plane H2 ... Upper stage side plane H3 ... Slope part S ... Sheet to be molded S1 ... Sheet forming area S2 ... Unnecessary sheet area S3 ... Unnecessary sheet area SL1 ... Slit SL2 ... Slit W ... Molded body W0 ... Deep drawing portion W1 ... Punch hole

Claims (1)

[Claims] 1. A method of molding a resin sheet, which comprises molding a molded article by imitating a resin sheet to conform to the irregularities of a molding die, wherein the resin sheet in a sheet forming region in the range where the molded body is shaped has irregularities of the molding die. When there is an unnecessary sheet area which is expanded by copying and is separated from the molded body after molding in the vicinity of the sheet forming area of the expanded portion, a force for expanding the resin sheet in the sheet forming area. The method for molding a resin sheet, wherein the opening portion opened by is formed in the unnecessary sheet area in advance before the resin sheet in the sheet forming area is elongated.