JPH0773874B2 - Vacuum forming method and vacuum forming die used for the forming - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention includes a horizontal wall portion and a vertical wall portion formed on the periphery of the horizontal wall portion, and has a concave cross-section at the intersection of the horizontal wall portion and the vertical wall portion. The present invention relates to a method for vacuum-forming a synthetic resin molded article having a cross recessed portion, which is formed into a sheet-shaped material having a foam layer on the back side, and a vacuum forming die used for the forming.

<Prior Art> Conventionally, when a molded product made of a synthetic resin is formed by vacuum forming, first, the entire circumference of the sheet-shaped material 5 is clamped by a clamp 4, and the sheet-shaped material 5 is heated in that state ( (See FIG. 4).

After that, the sheet material 5 is pressed against the lower mold 3 of the vacuum forming mold 1 while the entire circumference is clamped by the clamp 4, and the 16th
As shown in the figure, the mold is clamped, and the upper mold 2 provided with a large number of vent holes is evacuated to form a predetermined shape.

Then, the mold was opened, the molded product was taken out, and the peripheral edge was trimmed to obtain a product (see Japanese Patent Laid-Open No. 50-23479).

<Problems to be Solved by the Invention> However, in the conventional vacuum forming method, since the sheet material 5 is formed with the entire circumference being clamped by the clamps 4, the soft sheet material 5 is placed on the lower mold 3. When the sheet-shaped material 5 was placed in a state and clamped, the sheet-shaped material 5 was greatly stretched, and the upper portion of the sheet-shaped material 5 was thin so that the thickness of the molded product was uneven. In particular, when molding a molded product 6 having a deep bottom box shape having a horizontal wall portion 7 and a vertical wall portion 8 extending from the peripheral edge of the horizontal wall portion 7 as shown in FIG. Since the thickness was greatly reduced, the wall thickness was made more uneven.

In addition, since the sheet material 5 is molded with the entire circumference being clamped by the clamps 4, the parts α and β (see FIG. 16) to be trimmed, which are not products, are large and the yield of the molding material is poor. .

Further, as shown in FIG. 14, in the case of molding a molded product 6 having an intersecting concave portion Y having a concave cross-section at an intersecting portion of the horizontal wall portion 7 and the vertical wall portion 8, as a sheet-shaped material 5, When the one having the form layer 5b on the back surface side is used, the cross recess Y to be formed is formed in a state where the front surface side is compressed from the back surface side of the sheet material 5 at the time of forming. Therefore, after the mold release, due to the spring back of the form layer 5b, wrinkles are generated in the intersecting recess Y in an attempt to restore the thickness toward the surface side, and the appearance is deteriorated.

The present invention is to solve the above-described problems, and includes a horizontal wall portion and a vertical wall portion extending from the peripheral edge of the horizontal wall portion, and a cross recessed portion having a cross-sectional concave shape at the crossing portion of the horizontal wall portion and the vertical wall portion. When using a sheet-shaped material with a foam layer on the back side to form a shaped product by vacuum forming,
The material yield can be improved and the wall thickness can be made uniform.
Further, it is an object of the present invention to provide a vacuum forming method capable of preventing wrinkles from being generated in the intersecting concave portions and improving the appearance to perform the forming, and also to provide a vacuum forming die which can be effectively used during the forming.

<Means for Solving the Problems> A vacuum forming method according to the present invention includes a horizontal wall portion and a vertical wall portion formed on a peripheral edge of the horizontal wall portion, and at a crossing portion of the horizontal wall portion and the vertical wall portion. A method of softening a sheet-shaped material having a foam layer on the back side by vacuum forming a molded product made of synthetic resin with a crossed recess with a concave cross-section, with the peripheral edge clamped In a softening step of heating and softening the sheet-shaped material with, a part or all of the clamp that holds the peripheral edge of the sheet-shaped material is removed from the sheet-shaped material, and the sheet-shaped material is softened, A set step of disposing the foam layer side on the lower side of a vacuum forming die composed of an upper die and a lower die; and clamping the vacuum forming die to form the intersection of the sheet-shaped materials. A mold clamping step of crushing the foam layer in the portion where the recess is formed so as not to restore it, and sandwiching and sealing the entire periphery of the sheet-shaped material near the peripheral edge by the upper and lower molds, and vacuuming the sheet. And a shaping step of shaping the blank material into a predetermined shape.

A vacuum forming die according to the present invention includes an upper die and a lower die, which is a vacuum forming die used in the above-mentioned vacuum forming method, wherein the vacuum forming die is provided with a vent hole for vacuuming. The upper mold or the lower mold is characterized in that a sealing surface that closes the ventilation hole is formed at a portion that clamps the sheet-shaped material when the mold is clamped.

<Operation / Effect of Invention> In the vacuum forming method according to the present invention, a sheet-shaped material that is heated and softened in a state where the peripheral edge is clamped is clamped into a sheet-shaped part or all of the clamp that clamps the peripheral edge. Remove from the material, place it on the lower mold of a vacuum forming mold consisting of an upper mold and a lower mold, clamp the mold and clamp the entire periphery of the sheet material near the peripheral edge with the upper and lower molds, and then vacuum. And then molded.

That is, when arranging the softened seal-like material on the lower mold, a part or all of the clamp used for heating and softening the sheet-like material is removed, and a portion not clamped by the clamp is provided to make the sheet-like material From the arrangement, when the sheet material is stretched at the time of the arrangement or the mold clamping, the material at the portion where the peripheral edge is not sandwiched is displaced to the stretched portion and is replenished, It is possible to change the wall thickness. Therefore, even when molding a molded product with a horizontal wall and a vertical wall extending from the peripheral edge of the horizontal wall, be aware that the wall thickness becomes uneven. You can

In addition, before or after clamping the mold, part or all of the clamp is removed, and at the time of clamping, the upper and lower molds seal the entire circumference near the peripheral edge of the sheet-shaped material with the upper and lower molds, and a vacuum is drawn. Unlike the conventional method, it is not necessary to clamp all the circumference of the sheet material during molding, and when molding molded products of the same shape, the outer shape of the sheet material can be made smaller than in the conventional method. As a result, it is possible to reduce the number of parts that are not used as a product and are trimmed after molding, and it is possible to improve the material yield.

Furthermore, even if a sheet-shaped material having a foam layer on the back side is used, it is positively crushed and molded so that the foam layer is not restored in the intersecting concave portion to be molded. Therefore, even if a spring back of the form layer occurs after releasing from the mold, the cross recess Y does not have a spring back of the foam layer and does not restore so as to increase the thickness toward the surface side, so that wrinkles do not occur. Does not deteriorate the appearance.

Further, in the vacuum forming mold according to the present invention, in the upper mold or the lower mold provided with a vent hole for drawing a vacuum in the vacuum forming mold, at the site where the sheet-shaped material is sandwiched during the mold clamping of the above-mentioned vacuum forming method. Since the sealing surface that closes the ventilation holes is formed, the sheet-shaped material can be used as the mold surface of the upper mold or the lower mold equipped with the ventilation holes without air leakage when vacuuming after mold clamping. It can be adsorbed on and shaped into a predetermined shape.

Therefore, in the vacuum forming method according to the present invention, a shape having a horizontal wall portion and a vertical wall portion extending from the peripheral edge of the horizontal wall portion, and a cross recessed portion having a cross-sectional concave shape at the crossing portion of the horizontal wall portion and the vertical wall portion is formed. When using a sheet-shaped material with a foam layer on the back side to vacuum-mold the molded product of,
The yield of the sheet-shaped material of the material can be improved, the wall thickness can be made uniform, and wrinkles can be prevented from being generated in the intersecting recesses, and the appearance can be improved to perform molding. Further, in the vacuum forming die according to the present invention, when the above-described vacuum forming method is performed, the sheet-shaped material can be formed into a predetermined shape without causing air leakage.

<Embodiment> An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIGS. 7 and 14, the molded product 6 vacuum-molded in the embodiment includes a horizontal wall portion 7 and a vertical wall portion 8 extending from the peripheral edge of the horizontal wall portion 7, and includes the horizontal wall portion 7 and the vertical wall portion 8. The skin portion of the instrument panel in the interior part of an automobile is configured as a deep box shape having an intersecting recess Y having a concave cross-section at the intersecting portion. Further, as shown in FIGS. 1 and 3, the molded product 6 has a PP (polypropylene) foam layer 15b on the back surface side thereof.
It is formed from a sheet-like material 15 having a skin layer 15c of soft PVC (vinyl chloride) arranged on the surface of 5b.

Further, the molded product 6 of the embodiment is provided with a portion 8a having a long height and a portion 8b having a short height extending from the lateral wall portion 7 at the opposite portions of the vertical wall portion 8. An undercut portion 8c is formed in the short portion 8b. In addition, the lateral wall portion 7 has an upper step portion 7a.
And a lower step portion 7b are formed, and each step portion 7a, 7b is formed with a recessed portion 7c that is cut after stamping molding described later.

As shown in FIGS. 1 and 2, the vacuum mold 11 for molding the molded product 6 is made of a porous ceramic mold having a large number of vent holes, an upper mold 12 such as an electric mold, and a synthetic resin or aluminum. It is composed of a lower mold 13 of an assist plug type.

The upper mold 12 is a cavity mold surface 12a that can be formed into a predetermined shape by forming a grain pattern on the surface layer 15c of the sheet material 15.
When the mold is clamped,
When the sheet material 15 is sandwiched between the lower mold 13, the sheet material
A seal surface 12b formed by applying a silicone sealant is formed to seal against 15. Also,
An airtight cover body 12c is arranged around the upper die 12, and a suction means (not shown) is connected to the upper portion of the upper die 12.

The lower mold 13 is a sheet-shaped material 15 for the cavity mold surface of the upper mold 12.
A predetermined cavity mold surface 13a is provided so that it can be pressed against the 12a, and the sheet material 1 is formed around the cavity mold surface 13a with the sealing surface 12b of the upper mold 12 during mold clamping.
A sandwiching surface 13b is formed so that the peripheral edge of 5 can be sandwiched. In addition, the cavity mold surface 13a is provided with a concave portion 13 in consideration of molding and releasing of the undercut portion 8c of the molded product 6.
d is formed, and the sheet-shaped material 15 is
Vent holes 13c are formed so that they can be pressed against the 12 cavity mold surfaces 12a by air pressure and are connected to pressurizing means (not shown).

Further, in the design of the cavity 11a of the vacuum forming die 11, even if a spring back occurs in the vicinity of the convex portion X of the molded product 6, the convex portion X tip is pulled back on the surface side and is restored so that wrinkles occur. Therefore, the cavity 11a should be designed in anticipation of that (see Figures 11 and 14).

On the other hand, in the cross recessed portion Y of the molded product 6, unless any measures are taken, the front side of the sheet material 15 is compressed from the back side, and the PP foam layer 15b is thickened to the front side after molding. The spring backs up and wrinkles occur. Therefore, the cavity 11a is formed so that wrinkles do not occur, that is, the foam layer 15b of the intersecting recess Y to be molded is not restored after molding so that the PP foam layer 15b of the intersecting recess Y to be molded can be crushed during mold clamping. Design (see Figures 12 and 14).

Next, a process of molding the molded product 6 using this vacuum molding die 11 will be described.

Preparation Step First, a flat sheet material 15 corresponding to the molded product 6 as shown in FIG. 13 is prepared, and the peripheral portions A to F are clamped by the clamp 14 (see FIG. 3).

The sheet material 15 is prepared by cutting a sheet material formed by extrusion molding into a predetermined shape. At this time, the slit 15a is formed in advance in the molded product 6 at a portion where the recessed portion 7c of the upper step portion 7a of the lateral wall portion 7 which is to be largely projected and recessed is formed.
(See FIGS. 2 and 13) may be formed to further reduce the elongation of the sheet-shaped material 15 at the time of mold clamping described later. Further, the clamp 14 is configured to be able to clamp a plurality of predetermined portions on the peripheral edge of the sheet-shaped material 15, to partially release the clamp, and to move the clamped portion.

Softening process Then, while sandwiched by the clamp 14, the sheet-shaped material 15
Is heated to 160 to 210 degrees by the ceramic heater 16 to be softened (see FIG. 4).

At this time, unlike the conventional case where the entire circumference of the sheet-shaped material 5 is clamped by the clamp 4, the peripheral edge of the sheet-shaped material 15 is partially clamped by the clamp 14, so that the sheet-shaped material 15
At the time of heat shrinkage, the material of the portion whose peripheral edge is not sandwiched moves, and the strain of the sheet-shaped material 15 that has occurred at the time of extrusion molding can be removed.

After the setting step, the clamps 14 that clamped the sheet-shaped material 15 release the clamps of the A to C parts, and the clamps that clamped the D and E parts are shifted to the right in FIG. 13, the clamp is shifted to the left in FIG. 13, and the softened sheet material 15 is arranged on the lower mold 13 as the lower side on the PP foam layer 15b side (see FIG. 5).

At this time, since the sheet-shaped material 15 is arranged on the lower mold 13 by providing a portion that is not clamped by the clamp 14, the material of the portion whose peripheral edge is not clamped even when the sheet-shaped material 15 is stretched at the time of the arrangement. As a result of the aspect in which the material is replenished while being displaced to the region where it is about to extend, it is possible to suppress a change in wall thickness.

The position where the peripheral edge of the sheet material 15 is partially clamped by the clamp 14 is a position for preventing the sheet material 15 from wrinkling when placed on the lower mold 13, Set appropriately according to the shape of the product. Further, when the sheet-shaped material is placed on the lower mold, in the case of molding a molded product in which wrinkles are unlikely to occur, all the clamps that hold the peripheral edge of the sheet-shaped material may be removed.

Clamping step Then, the vacuum forming die 11 is clamped to crush the PP foam layer 15b of the intersecting recess Y to be formed, and the sealing material 12b of the upper die 12 and the sandwiching surface 13b of the lower die 13 are used to form the sheet material 15 The entire circumference in the vicinity of the peripheral edge is sandwiched and sealed (see FIG. 6). Also, once the mold is clamped, the peripheral edge of the sheet-shaped material 15
Since the position of the sheet material 15 is fixed by being clamped by 12 and 13, the rest of the clamp 14 clamped before the mold clamping is removed.

In addition, this mold clamping is performed on the part excluding the cross recessed part Y to be molded.
The pressure is set so that the PP foam layer 15b is not crushed.

Further, even at the beginning of this mold clamping, since the portion that is not clamped by the clamp 14 is provided, even if the sheet-shaped material 15 is stretched, the material of the portion where the peripheral edge is not clamped shifts to the portion that is trying to stretch. The sheet-shaped material 15
It is possible to suppress unevenness in the thickness of the product as much as possible.

Forming step After that, a pressure means and a suction means (not shown) are operated to evacuate and press the sheet material 15 against the cavity die surface 12a of the upper die 12 to form a grain pattern on the surface to form a sheet material. 15 is shaped into a predetermined shape and then cooled (first
・ See Figure 2.)

At this time, at the portion sandwiching the sheet-shaped material 15 around the cavity die surface 12a of the upper die 12, the sealing surface 12b is formed so as to close the ventilation hole for sucking air during evacuation. Air can be prevented from leaking from the peripheral edge of the sandwiched portion, and molding can be performed without any trouble.

Mold Release Step After the molded product 6 is vacuum-formed, the mold is opened, the molded product 6 is removed from the upper mold 12, and unnecessary peripheral portions are trimmed to obtain a product (see FIG. 7).

And when trimming, unlike the conventional case, the whole circumference of the sheet material 15 is vacuum-molded when clamping and vacuuming.
Even if it is not clamped by the clamp 14 arranged around the 11,
The sheet-shaped material 15 can be formed in a shape in which the peripheral edge is arranged inside the vacuum forming die 11, the outer shape can be made smaller than that of the conventional sheet-shaped material 5, and the parts α and β to be trimmed that do not become a product. It can be reduced and the yield of the material can be improved.

In addition, as the sheet-shaped material 15, the PP foam layer 15 on the back side
Even if the one having b is used, in the cross recess Y to be molded, the PP foam layer 15b is positively crushed and molded so as not to be restored. Therefore, after mold release, the PP foam layer 15
Even if the spring back of b occurs, at the cross recess Y, PP
Since the foam layer 15b is not crushed to generate a spring back and is not restored so as to increase the wall thickness to the surface side, wrinkles do not occur and the appearance of the molded product 6 is not deteriorated.

As described above, the vacuum forming method according to the embodiment and the vacuum forming die 11 used for forming the same have the same effects as those described in the section of the above-mentioned action and effect.

Furthermore, the conventional vacuum forming method is a mode in which the clamp 4 holds the entire peripheral edge of the sheet-shaped material 5 before and after the mold clamping, and the entire peripheral edge of the sheet-shaped material 5 is protruded from the vacuum forming die 1, and , The peripheral cover body 2c of the upper mold 2
Therefore, the upper and lower molds 2 and 3 were large in size because air leakage did not occur during molding.

On the other hand, in the vacuum forming method of the embodiment, at the end of the mold clamping, the sheet-shaped material is formed by the sealing surface 12b and the sandwiching surface 13b around the cavity mold surfaces 12a and 13a of the upper and lower molds 12 and 13 of the vacuum forming mold 11. It clamps the entire circumference of the periphery of the periphery of 15, and the mold surfaces 12a and 13a for the cavity and the sealing surfaces 12b and 13b of the periphery thereof.
It is sufficient to form the upper and lower molds 12 and 13 within the range in which can be arranged, and the vacuum forming mold 11 used can be made smaller than the conventional one.

Furthermore, when vacuum-molding a molded product 6 having a long portion 8a and a short portion 8b of the vertical wall portion 8, according to the conventional vacuum forming method, the entire peripheral edge of the sheet-shaped material 5 is clamped by the clamp 4 before and after the mold clamping. The sheet-shaped material 5
The portion to be the short portion 8b in will be narrowed to the same extent as the portion to be the long portion 8a.

However, in the vacuum forming method of the embodiment, the periphery of the short portion 8b of the sheet-shaped material 15 is sandwiched by the upper and lower molds 12 and 13, and can be formed with a shallow drawing, and in particular, the vertical shape as formed in the embodiment. When the molded product 6 including the long portion 8a and the short portion 8b of the wall portion 8 is vacuum-molded, it is possible to effectively make the thickness of the molded product 6 uniform.

In the vacuum forming mold 11 used in the examples, the upper mold 12 for vacuuming is shown as a female mold, but in the case of forming a grain pattern etc. on the inner peripheral surface of the molded product The upper mold for vacuuming may be a male mold and the lower mold on which the softened sheet material is arranged may be a female mold.

The process of manufacturing the instrument panel 26 (see FIGS. 10 and 15) using the molded product 6 will be described below.
It looks like this:

First, as shown in FIG. 8, the trimmed molded product, that is, the skin 6 of the instrument panel 26
The upper mold 22 of the stamping mold 21 including the lower mold 22 and the lower mold 23 is set. The upper die 22 moves up and down with respect to the lower die 23, and the outer skin 6 is easily set to about 90
The upper mold is configured to be rotatable when the skin 6 is set.
Rotate 22 downward. Then, the upper mold 22 has an epidermis 6
After setting, the upper die 22 is rotated upward so as to face the lower die 23.

After that, as shown in FIG. 8, a predetermined amount of the molding material M made of molten PP forming the base material 27 of the instrument panel 26 is flown out from the die 29 of the extrusion head 28 onto the lower mold 23.

Then, as shown in FIG. 9, the mold is clamped to perform stamping molding. At this time, part of the PP foam layer 15b in the skin portion 6 is fused with the molding material M by the heat of the molten molding material M, and the skin portion 6 and the base material 27 are joined together without using an adhesive. The Rukoto.

At the place where the skin 6 is likely to be displaced during mold clamping, a hole 6a is provided in the skin 6, and the skin 6 is hooked at a predetermined position of the upper and lower molds 22 and 23 by fitting the hole 6a. It is desirable to raise the pins 22a etc. to prevent the skin 6 from shifting (see FIGS. 8, 9, and 14).

After that, when the base material 27 is hardened, as shown in FIG. 10, the slide core 24 of the upper mold 22 is moved and the mold is opened to take out the molded product, the peripheral edge is trimmed, and the skin portion 6 is rolled up. In addition to performing terminal processing,
A predetermined instrument panel 26 can be obtained by cutting the part of the recess 7c of the skin 6.

When the stamping molding is performed in this manner, the molten molding material M is flown out onto the lower mold 23, and the mold is clamped and molded in that state, so that the base material 27 is separately molded into a predetermined shape in advance. It is not necessary to prepare, and the base material 27 and the skin part 6 can be joined to each other without using an adhesive, and a molded product 26 having two layers of the skin part 6 and the base material 27 can be easily manufactured. can do. By the way, when manufacturing a molded product 26 consisting of two layers by conventional stamping molding,
The skin portion 6 and the base material 27 are separately molded in advance into a predetermined shape and prepared, and the skin portion 6 and the base material 27 are joined together at the time of stamping molding using an adhesive, which is very difficult. It was a hassle.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a molding die during molding (molding step) showing an embodiment of the present invention, and FIG. 2 is a vertical sectional view of a molding die used in the embodiment. Sectional drawing in the direction orthogonal to the plane shown in the figure, FIG. 3 is a diagram showing a preparation step of the same example, FIG. 4 is a figure showing a softening step of the same example, and FIG. FIG. 6 is a diagram showing a set process of an example, FIG. 6 is a diagram showing a mold clamping process of the same embodiment, FIG. 7 is a diagram showing a mold release process of the same embodiment, and FIG. 9 is a sectional view of the forming die showing the opening of the stamping forming performed in the step, FIG. 9 is a sectional view showing the stamping forming, FIG. 10 is a view showing the releasing after the stamping forming is completed, FIG. FIG. 12 is a diagram for explaining measures against spring back in the vicinity of the convex portion of the molded product during vacuum forming of the same embodiment, and FIG. Fig. 13 is a diagram for explaining measures against spring back near the recess of the molded product. Fig. 13 is a plan view showing a sheet-shaped material used in the same embodiment. Fig. 14 is a perspective view showing a molded product molded in the same embodiment. FIG. 15 is a perspective view showing a molded product which is stamped and molded in the subsequent step of the same embodiment, and FIG. 16 is a sectional view showing a conventional vacuum molding. 6 ... Molded product, 7 ... Horizontal wall part, 8 ... Vertical wall part, 11 ... Vacuum forming mold, 12 ... Upper mold, 12b ... Sealing surface, 13 ... Lower mold, 14 ... Clamp, 15 ...... Sheet material, 15b ・ ・ ・ Form layer, Y …… Cross recess.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsu Ando Kasuga-mura, Aichi Prefecture Kasuga-mura, Ochiai, Nagahata No. 1, Toyoda Gosei Co., Ltd.

Claims (2)

[Claims] 1. A synthetic resin having a shape including a horizontal wall portion and a vertical wall portion formed on a peripheral edge of the horizontal wall portion, and a cross recessed portion having a cross-section concave shape at a crossing portion of the horizontal wall portion and the vertical wall portion. A softening step of softening a sheet-shaped material having a foam layer on the back side to form a molded article by vacuum forming by heating the sheet-shaped material while clamping the peripheral edge with clamps. And a part or all of the clamp holding the peripheral edge of the sheet-shaped material is removed from the sheet-shaped material, and the sheet-shaped material is softened, with the form layer side being the lower side, the upper die and the lower die. A set step of arranging the vacuum forming die on the lower die of the vacuum forming die, and clamping the vacuum forming die to restore the form layer in the portion forming the intersecting recess in the sheet material. Clamping step of crushing and sealing the sheet-shaped material by clamping the entire periphery of the sheet-shaped material by the upper and lower molds, and a shaping step of vacuuming and shaping the sheet-shaped material into a predetermined shape. And a vacuum forming method. 2. The sealing surface of the upper mold or the lower mold having a ventilation hole for drawing a vacuum in the vacuum molding die, which seals the ventilation hole at a portion for clamping the sheet-shaped material at the time of mold clamping. The vacuum forming mold used for vacuum forming according to claim 1, which has a structure in which