JPH11138624A - Sheet forming mold and sheet forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the prevention of a forming mold even having an inverted taper from being broken at the clamping and opening of molds by a constitution wherein the opening peripheral edge part of the cavity part of a female mold is made of an elastic member. SOLUTION: A formed article is a cup-like container having an opening at its top surface part. Its sheet forming mold 20 is the type of a mold, in which an inverted taper part is formed under a mold clamped state. A female mold 31 can be made of aluminum similarly as a male mold 22. In the female mold 21, a cavity part 24, in which the plug part 25 of the male mold 22 is to be inserted, is formed. Further, in the female mold 21, a liner 31 is fitted so as to be arranged to form the opening peripheral part 35 of an opening 32. Furthermore, a wall surface 33 is composed of this liner 31. The liner 31 is made of silicone rubber, which preferably deforms by an external force as large as developed by pushing with a hand especially under the ambience of about 100 deg.C and immediately restores when the external force is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold used for molding a resin sheet and a molding method.

[0002]

2. Description of the Related Art Conventionally, for forming a foamed sheet, for example, an apparatus shown in FIG. 6 has been widely used (for example, see Japanese Patent Application Laid-Open No. 6-218805). Referring to FIG. 1, foam sheet 1 is sequentially fed out from raw material 2, and is first sent into oven 3. In the oven 3,
The ambient temperature is set to be constant, and the foam sheet 1
It is heated to a predetermined temperature in the oven 3 in advance. The heating temperature at this time differs depending on the material of the foam sheet used. The heated foam sheet 1 is immediately sent to the press 4.

The press 4 has a molding die 7 having a female die 6 and a male die 5. The foam sheet 1 is made of a molding die 7
The molding die 7 is driven by a cylinder 8 to clamp the female die 6 and the male die 5 to perform press molding. The molded foam sheet 9 is cut by a cutter 10 and trimmed to complete a product.

[0004]

When the female mold 6 and the male mold 5 are clamped, the heated foam sheet 1 is stretched. At this time, the foam sheet 1 is Or a slip occurs between the male mold 5. The magnitude of the slip resistance changes depending on the temperature of the female mold 6 or the male mold 5,
When the mold is made of metal, generally, the higher the temperature, the more slippery.

[0005] By the way, the foam sheet 1 is
Is difficult to heat the entire foamed sheet 1 uniformly, and the foamed sheet 1 will have some temperature unevenness along the sheet surface. On the other hand, the molding die 7 is usually made of aluminum. However, since aluminum is very excellent in thermal conductivity, when the foamed sheet 1 having uneven temperature is pressed, the temperature unevenness of the foamed sheet 1 is reduced. Temperature unevenness corresponding to the above occurs also on the molding die 7 side.

FIG. 7 shows a foam sheet 1 formed by a molding die 7.
FIG. 4 is a view schematically showing a state in which is formed. Referring to the figure, when temperature unevenness occurs in the molding die 7 made of aluminum, a slippery portion and a slippery portion occur between the foamed sheet 1 and the molding die 7, and therefore, the foamed sheet 1 has a portion that is strongly pulled during mold clamping and a portion that is not. In particular, the female mold 6 of the foam sheet 1
If the portion corresponding to the edge portion 11 is lower in temperature than the other portions, a phenomenon occurs in which the edge portion 11 is strongly pulled.

As described above, if the foamed sheet 1 is not uniformly stretched as a whole, an unintended pattern is generated in a strongly pulled portion after molding, which causes a problem that the quality of a product is deteriorated.

[0008] In the molding die 7 shown in FIG.
The taper 12 is formed between the male mold 5 and the male mold 5, but depending on the mold, an inverse taper may be formed between the female mold and the male mold. In a mold having such an inverse taper, even if a mold clearance as designed in advance is formed in a mold-clamped state, in a mold-opened state,
Due to the influence of the reverse taper, the gap between the female mold and the male mold, particularly, the gap between the edge portion of the female mold and the corner of the male tip becomes extremely small. For this reason, depending on the assembling accuracy of the press machine, the female mold and the male mold may collide, and the mold may be damaged.

Accordingly, a first object of the present invention is to provide a sheet molding die and a sheet molding method which can prevent damage during mold clamping / mold opening even in a molding die having a reverse taper. To provide.

A second object of the present invention is to provide a sheet forming die and a sheet forming method capable of suppressing the occurrence of defective products in a formed product by uniformly stretching a material sheet during mold clamping. That is.

[0011]

In order to achieve the first object of the present invention, a sheet molding die according to claim 1 is provided with a female mold having a predetermined cavity and a female mold having a predetermined cavity. A sheet molding die for press-forming a material sheet by clamping, comprising a female mold and a male mold to be mold-clamped, wherein at least the opening peripheral edge of the cavity is elastic. It is characterized by being constituted by members.

According to this configuration, the molding die has a reverse taper, and depending on the assembling accuracy of the molding die and other various circumstances, the male mold and the female mold are separated when the mold is clamped or opened. Even if a collision occurs, since the elastic member is used at least on the peripheral edge of the opening of the female cavity, the impact at the time of the collision can be reduced by the elastic member. Moreover, since the elastic member is used at the peripheral edge of the opening of the cavity, there is no inconvenience that the clamping force is insufficient when the material sheet is pressed.

According to a second aspect of the present invention, there is provided a sheet molding die according to the first aspect, wherein the elastic member includes silicon rubber. Is what you do.

According to this configuration, the same operation as the first aspect of the invention is achieved. In addition, by using silicon rubber as the elastic member, it is possible to reduce at least the thermal conductivity of the peripheral edge of the opening of the cavity.

In order to achieve the first object of the present invention, a sheet forming method according to a third aspect includes a female mold having a predetermined cavity and a plug inserted into the female mold cavity. In a sheet forming method for press-forming a material sheet by clamping with a male mold,
At the time of mold clamping, an elastic member is arranged at least on the periphery of the opening of the cavity, and the material sheet is pressed via the elastic member.

According to this configuration, the molding die has a reverse taper, and the male die and the female die are closed when the mold is clamped or opened due to the assembling accuracy of the molding die and various other circumstances. Even if a collision occurs, the elastic member is used at least in the periphery of the opening of the female cavity at the time of mold clamping, so that the impact at the time of collision can be reduced by the elastic member. Moreover, since the elastic member is used at the peripheral edge of the opening of the cavity, there is no inconvenience that the clamping force is insufficient when the material sheet is pressed.

Further, in order to achieve the second object of the present invention, a sheet forming method according to claim 4 is characterized in that, in the sheet forming method according to claim 3, the elastic member contains silicon rubber. Is what you do.

According to this configuration, the same operation as the third aspect of the invention is achieved. In addition, by using silicone rubber as the elastic member, it is possible to reduce at least the thermal conductivity of the peripheral edge of the opening of the cavity, and to avoid a rapid temperature change of the peripheral edge of the opening due to the temperature of the material sheet. it can.

[0019]

Embodiments of the present invention will be described below. FIG. 1 is a cross-sectional view of a sheet forming die according to an embodiment of the present invention, showing a state where the die is clamped. FIG. 2 is a cross-sectional view of the sheet forming die, showing a state where the die is opened.

Referring to these drawings, this sheet forming die 20 is a so-called match mold. The sheet molding die 20 has a female mold 21 and a male mold 22. When the mold is opened as shown in FIG.
A sheet forming operation is performed by arranging a material sheet between the two and inserting the male mold 22 into the female mold 21 and clamping the mold.

The feature of this embodiment is that the molded product formed by molding is a cup-shaped container having an opening on the upper surface, and the sheet molding die 20 is a so-called closed mold. A liner 31 made of silicone rubber is mounted on a predetermined portion of the female mold 21 in that the reverse taper portion 30 is formed, and a material sheet is pressed through the liner 31 at the time of mold clamping. The point is that it is.

The male mold 22 can be made of aluminum, and has a plug 25 inserted into the cavity 24 of the female mold 21. At the base end portion of the plug portion 25, a side surface 34 that is inclined so as to increase the outer diameter of the plug portion 25 is formed. The side surface 34 is formed so as to go around the outer periphery of the base end portion of the plug portion 25.

The female mold 21 can be made of aluminum similarly to the male mold 22. Female mold 21 is male mold 22
Cavity portion 24 into which the plug portion 25 is inserted. When the male mold 22 and the female mold 21 are clamped, a predetermined clearance 2 is provided between the female mold 21 and the male mold 22.
3 are formed. This cavity 2
A wall surface 33 is formed at the entrance of 4 so as to be inclined so as to increase the diameter of the opening 32 of the cavity portion 24. This wall surface 33 is formed so as to go around the inner periphery of the entrance portion of the cavity portion 24. Also, the wall 33
Corresponds to the inclination angle of the side surface 34. Thereby, with the male mold 22 and the female mold 21 clamped,
The reverse taper portion 30 is configured.

Further, a liner 31 is fitted into the female mold 21. The liner 31 is arranged so as to form an opening peripheral portion 35 of the opening 32.
1 defines the wall surface 33. The liner 31 is formed of silicon rubber as described above.
Silicon rubber having a hardness of 40 to 80 or less in a JIS K6301 A type spring hardness test can be used. It is preferable to restore immediately after the removal. In the present embodiment, one having a hardness of 70 is used.

Next, a sheet forming operation using the sheet forming die 20 according to the present embodiment will be described. FIG.
FIG. 4 is a view schematically showing a sheet forming operation using a sheet forming die 20.

Referring to FIG. 3A, reference numeral 40 indicates a material sheet. This material sheet 40 is unwound from a raw material and is heated in advance by an oven (not shown). As the material sheet 40, polystyrene, polypropylene, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, or a composite product thereof can be used. Further, the material sheet may be a non-foamed sheet or a foamed sheet. In the present embodiment, a foamed polypropylene sheet is employed. Also,
The heating temperature for preheating is set to 140 ° C.
In general, the preheating temperature is 110-120 ° C. for polystyrene and 130-150 ° C. for polypropylene.
C., 80-90.degree. C. for polyethylene terephthalate, 100-120.degree. C. for polyethylene naphthalate, and 130-150.degree. C. for polycarbonate.

As shown in FIG. 3A, the sheet forming die 2
FIG. 3 (b) in a state where the material sheet 40 is arranged for
The male mold 22 is clamped to the female mold 21 as shown in FIG. The speed at which the mold is clamped is set to 100 mm / min. At the time of this mold clamping, the material sheet 40 is stretched and finally formed into a match mold as shown in FIG.

The peripheral edge 35 of the opening of the female mold 21 is
It is composed of a liner 31 made of silicone rubber. Therefore, when the material sheet 40 is pressed by the mold clamping, the liner 31 is interposed between the material sheet 40 and the female mold 21. Thus, the thermal conductivity of the opening peripheral portion 35 of the female mold 21 is low. Therefore, even when the preheated material sheet 40 does not have a uniform temperature as a whole and has a temperature distribution along the sheet surface, the temperature distribution corresponds to the temperature distribution when the mold is clamped. Thus, the temperature of the opening peripheral portion 35 of the female mold 21 can be prevented from rising or falling. That is, at the time of mold clamping, the slip resistance between the material sheet 40 and the female mold 21 is made uniform, and the material sheet 40 is strongly pulled at the edge portion 50 of the opening 32 of the female mold 21 as compared with other portions. The phenomenon can be avoided.

As a result, the material sheet 40 can be evenly stretched at the time of mold clamping. That is, a specific portion of the material sheet 40 is not strongly pulled at the time of mold clamping, and it is possible to prevent an unintended pattern or the like from being generated in a product and to maintain a constant quality. In particular, in the present embodiment, since a cup-shaped container is molded, it is possible to prevent wrinkles and the like from occurring around the opening of the container.

In addition, by forming the opening peripheral portion 35 of the female mold 21 with silicone rubber, there is an advantage that the molded product can be taken out very smoothly when the mold is opened.

FIG. 4 shows a comparison inspection result when a molding operation is actually performed using a conventional mold and the sheet molding mold 20 according to the present embodiment. The inspection items are the weight of the molded article, the lip strength of the molded article, the presence or absence of wrinkles (unintended patterns) and cracks on the appearance of the molded article, and the releasability of the molded article.
The number of tests was 20 for each mold.
Regarding the weight of the molded article and the lip strength of the molded article, the maximum value, the minimum value, the average value and the standard deviation σ _n-1 of 20 tests were obtained. The presence or absence of wrinkles or cracks on the appearance of the molded article and the releasability of the molded article were visually examined and judged.

The weight of the molded article is in grams. Inspection of the weight of the molded article is performed by the material sheet 40 during molding.
Is not uniformly stretched, the thickness variation of the molded article becomes large, and as a result, the weight variation becomes large. The unit of the lip strength is Newton. The reason for examining the lip strength is that when the thickness of the molded article varies greatly, a high rigidity part and a low rigidity part occur in the molded article. Then, by measuring these, it can be determined whether or not the material sheet 40 is uniformly stretched.

The lip strength is defined as follows. That is, as shown in FIG. 5, a cup-shaped container 51 which is a molded product is sandwiched by a compression tester 60 under predetermined conditions.
In this state, the repulsive force of the container 51 is measured, and the magnitude of the repulsive force is defined as the lip strength. In the case of the present embodiment, the compression speed by the compression tester 60 is 100 mm / mi.
n and the compression distance is 10 mm. That is, the lip strength is the maximum value of the repulsive force when the compression speed is compressed by 10 mm at a compression speed of 100 mm / min.

As shown in FIG. 4, the weight and the lip strength of the molded product are smaller than those of the conventional product, and no wrinkles or cracks are generated. Therefore, it can be seen that the use of the sheet forming die 20 according to the present embodiment can achieve good forming in which the material sheet 40 is uniformly stretched.

Further, in the present embodiment, by forming the opening peripheral portion 35 with the liner 31 made of silicone rubber, the following operation and effect can be obtained.

The reverse tapered portion 3 like the sheet forming die 20
In the type having 0, the dimension of the clearance 23 changes during mold clamping / mold opening. That is, as shown in FIG. 1, if the clearance in the mold-clamped state is d, the clearance in the mold-opened state is, as shown in FIG. 2,
This value is considerably smaller than d. Specifically, in the present embodiment, the clearance d is set to 1.5 mm, and the clearance when the mold is opened is 0.7 mm. The clearance d is an extremely important design dimension for achieving a required molding dimension, and it is not allowed to change the value of d in order to increase the clearance when the mold is opened.

As described above, when the clearance between the male mold 22 and the female mold 21 is extremely small, the accuracy of assembling the sheet forming mold 20 and other various circumstances during the mold clamping / mold opening may be reduced. Although the male mold 22 and the female mold 21 may collide with each other, even if they collide, the impact can be mitigated by the liner 31. And liner 3
No. 1 has a hardness of 70 and is used only for the opening peripheral portion 35 of the cavity portion 24, so that there is no inconvenience that the clamping force when the material sheet 40 is pressed is absorbed by the liner 31. , Sufficient mold clamping force can be secured.

The following is a possible modification of this embodiment. Although the liner 31 is made of silicon rubber, other elastic members can be generally used. However, depending on the type of the material sheet 40 to be molded and the molding conditions, the elastic member is required to have heat resistance of at least about 200 ° C. In terms of hardness, performance equivalent to that of the silicone rubber is required. It should be noted that colored silicone rubber can also be used.

In the present embodiment, the liner 31 is mounted only on the opening peripheral portion 35 of the female mold 21.
Can be formed entirely of silicone rubber. However, the male mold 22 can also be formed of silicone rubber. As described above, the influence of the temperature distribution of the material sheet 40 can be effectively avoided by forming the molding die itself from silicon rubber.

[0040]

According to the first or third aspect of the present invention,
Since the elastic member is used at least at the peripheral edge of the opening of the cavity of the female mold, even if the male mold and the female mold collide at the time of mold clamping and mold opening, this impact is mitigated by the elastic member. It is possible to prevent the mold from being damaged. Moreover, since the elastic member is used at the peripheral edge of the opening of the cavity, it is possible to prevent the molded article from being defective due to insufficient clamping force when pressing the material sheet.

According to the second or fourth aspect of the invention, the same effects as those of the first or third aspect of the invention can be obtained. In addition, by using silicone rubber as the elastic member, at least the thermal conductivity of the peripheral edge of the opening of the cavity can be reduced. At this time, the material sheet can be evenly stretched. As a result, a specific portion of the material sheet is not strongly pulled, and the quality of the product can be kept constant.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a sheet forming die according to an embodiment of the present invention, showing a state in which the die is clamped.

FIG. 2 is a cross-sectional view of the sheet forming die according to the embodiment of the present invention, showing a state where the die is opened.

FIG. 3 is a diagram schematically showing a molding operation using a sheet molding die.

FIG. 4 is a diagram showing a comparison between when a molded product is manufactured using a conventional mold and the mold according to the present embodiment.

FIG. 5 is a schematic diagram illustrating the concept of lip strength.

FIG. 6 is a view schematically showing an apparatus for performing a conventional sheet forming process.

FIG. 7 is a view schematically showing a state in which a foam sheet is molded by a conventional molding die.

[Explanation of symbols]

 Reference Signs List 20 sheet molding die 21 female die 22 male die 23 clearance 24 cavity portion 25 plug portion 30 reverse taper portion 31 liner (elastic member) 32 opening 33 wall surface 34 side surface 35 opening peripheral portion 40 material sheet 50 edge portion

Claims (4)

[Claims] 1. A material sheet comprising: a female mold having a predetermined cavity portion; and a male mold having a plug portion inserted into the female cavity portion and being clamped by a female mold and a mold. A sheet forming die for press-forming a sheet, wherein at least an opening peripheral portion of the cavity is formed of an elastic member. 2. The sheet molding die according to claim 1, wherein said elastic member contains silicon rubber. 3. A sheet forming method for press-forming a material sheet by clamping with a female mold having a predetermined cavity portion and a male mold having a plug portion inserted into the female mold cavity portion. In this case, an elastic member is arranged at least on the peripheral edge of the opening of the cavity portion, and the material sheet is pressed via the elastic member. 4. The sheet forming method according to claim 3, wherein the elastic member contains silicon rubber.