JP2000229351A - Production of undercut-shaped thermoformed article and female mold for thermoforming - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce the article by demolding stably even in the shape of a large undercut by a method in which during demolding, low pressure air is supplied from a vacuum-demolding holes converged near an undercut forming part of help the demolding from the undercut forming part of a molding while the part being warped. SOLUTION: A female mold for thermoforming is composed of a bowl-shaped main cavity 21 and a nearly cylindrical bottom mold 22 to close a through hole 21a. Numbers of vacuum-demolding holes 23 are arranged in the inner surface of the female mold to be converged to a bowl bottom part for forming an undercut. The holes 23, through a hollow passage formed in the bottom mold 22 and a hollow passage formed in a bottom mold base, are made to communicate with an external pressure control mechanism through a control valve, during demolding, and compressed air is supplied, while an undercut forming part is being warped, to help demolding from the undercut forming part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermoformed product having an undercut shape and a female mold for thermoforming, and more particularly to a thermoform having an undercut shape suitable for forming a deep undercut shape. The present invention relates to a method for producing a molded article and a female mold for thermoforming.

[0002]

2. Description of the Related Art In thermoforming, a thermoplastic resin plate is heated to a plastic state, sucked by a mold, molded, and released from the same mold. Since the thermoplastic resin plate remains flexible even when cured, a certain degree of undercut shape is possible.

[0003]

In the above-mentioned conventional method for producing a thermoformed product having an undercut shape,
The undercut shape allowed for stable production is small, and there is a problem that, for example, when trying to produce a thread bottom as a bowl of cup noodles, it is not satisfactory. The present invention has been made in view of the above problems, and has a method of manufacturing a thermoformed product having an undercut shape which can be stably released even with a larger undercut shape, and a female mold for thermoforming. The purpose is to provide.

[0004]

In order to achieve the above object, the invention according to claim 1 is characterized in that a vacuum / release hole is concentratedly arranged near an undercut forming portion in a molding die for thermoforming, and the mold is released. At the same time, a configuration is employed in which compressed air is supplied from the vacuum / release hole to deflect the undercut-shaped part of the molded product and assist the release from the undercut-formed part.
In the invention according to claim 1 configured as described above, the molding die for thermoforming has an undercut forming portion, and the vacuum / release holes are concentrated around this portion.
Therefore, when the compressed air is supplied from the vacuum / release hole at the time of mold release, the undercut-shaped portion of the molded product is bent, and the overlap with the undercut-formed portion is reduced and the molded product is easily detached.

[0005] Here, the mold for thermoforming can basically be constituted by either a male mold or a female mold. As an example, the invention according to claim 2 is a method for manufacturing a thermoformed product having an undercut shape according to claim 1, wherein the thermoforming mold is formed by a female mold having a bowl-shaped concave shape. The above-mentioned undercut formation site is formed in a divergent shape from the bottom of the bowl-shaped concave bowl toward the back side, and the above-mentioned undercut is formed while supplying pressure air from the vacuum / release hole to bend the bottom of the molded product. It is configured to assist release from the cut formation site.

In the invention according to claim 2 configured as described above, the thermoforming mold is a female mold having a bowl-shaped concave shape, and is directed from the bottom of the bowl-shaped concave shape toward the back side. It is formed in a flared shape. Therefore, when the molded product is pulled out from the female mold, the flared portion has an undercut shape. Vacuum and release holes are concentrated around this undercut formation site, so if air is supplied from the vacuum and release holes during release, pressure will be applied from the outside to the inside of the bottom of the bowl. Is done. If pressure is applied from the bottom of the bowl, the bowl will bend inward with the bowl bottom furthest from the opening end as the center. Then, the protruding portion that widens from the bottom of the bowl becomes oblique with respect to the concave portion of the undercut forming portion provided in the female mold, so that it easily slips through.

By the way, if an undercut shape is formed at the bottom of the bowl and the vacuum / release holes are concentrated in the vicinity of the undercut shape, they will not be arranged near the opening end.
As a result, the portion on the opening end side may not be in close contact with the inner peripheral wall surface of the mold. Therefore, the invention according to claim 3 is:
3. The method of manufacturing a thermoformed product having an undercut shape according to claim 2, wherein the female mold has the vacuum / release hole formed in a bottom portion of the bowl, and a portion near the opening end of the bowl-shaped concave shape. An air communication hole is formed, and compressed air is supplied from inside the bowl of the molded product during molding.

In the third aspect of the present invention, an air communication hole is formed near the opening end of the bowl-shaped concave shape, and compressed air is supplied from the inside of the bowl of the molded product at the time of molding. . A vacuum / release hole is formed on the bottom side of the bowl, and when a negative pressure is applied during molding, suction is performed along the inner peripheral surface shape of the mold. On the other hand, since compressed air is supplied from the inside of the bowl of the molded product during molding, not only the bottom of the bowl but also the portion near the opening end is pressed toward the inner peripheral surface of the mold. The air between the two is sucked from the vacuum hole on the bottom side of the bowl and is exhausted from the atmosphere communication hole from the end of the opening, so that the air adheres over the entire inner surface of the bowl-shaped concave shape.

It works more effectively if the timing of supplying compressed air at the time of mold release is adjusted to another operation. As an example, the invention according to claim 4 is a method for manufacturing a thermoformed product having an undercut shape according to any one of claims 1 to 3, wherein the vacuum /
It is configured to start supplying compressed air from the release hole. In the invention according to claim 4 configured as described above,
Since the compressed air is supplied prior to the knockout, the compressed air is supplied from the time when the portion near the opening end is attached to the mold, and the bottom of the bowl is easily bent. This is because even if compressed air is supplied after a gap is formed between the mold near the opening end and the mold after the start of knockout, the compressed air leaks out and cannot be bent.

As described above, it is not impossible to use a male type instead of a female type. In the case of a male mold that forms a bowl, the softened thermoplastic resin will be sucked into the outer surface of the mold,
When compressed air is supplied at the time of release from the mold, the compressed air expands outward and bends, so that it is likely to come off from the undercut formation site. As described above, the method of assisting the mold release by bending the molded product immediately before the mold release is realized in a substantial device, and in this sense, it is easily understood that the present invention can be applied to a substantial device. it can. In this case, the invention according to claim 5 is formed in a bowl-shaped concave shape, and a vacuum / release hole is formed at the bottom of the bowl from the viewpoint that the supply of the compressed air and the bending thereof has an effect of facilitating release. It is arranged so that it is concentrated and the air communication hole is arranged at the part near the opening end.

[0011] In the invention according to claim 5 configured as described above, the vacuum bottom is formed on the bottom of the bowl formed in the bowl-shaped concave shape.
The release holes are concentrated, and the bottom of the bowl is bent if air is supplied from the vacuum / release holes, and the atmosphere communication hole is located near the opening end. Even if the air existing between the mold and the peripheral surface cannot be exhausted from the vacuum / release hole, the air is released to the atmosphere outside the mold. Of course, it may be configured as an integral unit including the configuration for performing the supply / exhaust control. As one such example, the invention according to claim 6 is characterized in that, in the thermoforming female mold according to claim 5, the vacuum / release hole is arranged at the bottom of the bowl-shaped concave bowl at the time of release. A configuration is provided with a pressurized air supply mechanism for mold release that bends the bottom of the bowl of the molded product inward in the mold by supplying compressed air.

When the pressurized air supply mechanism for release supplies compressed air from the vacuum / release hole as described above, the bottom of the bowl is bent. Deflection of the bowl bottom can assist mold release regardless of the presence or absence of the undercut shape, but the real value is obtained when the undercut shape is formed. For this reason, the invention according to claim 7 is the thermoforming female mold according to any one of claims 5 and 6, wherein the undercut forming portion formed to be divergent from the bottom of the bowl-shaped concave bowl. And pressurized air is supplied from the vacuum / release hole to bend the bottom of the bowl of the molded product and release the same from the undercut formation site.

[0013] In the invention according to claim 7 having the above-described structure, the undercut forming portion is formed so as to diverge from the bottom of the bowl-shaped concave shape, and the molded product is pulled out as usual. Even if it tries, the undercut formation site and the undercut shape of the molded product interfere. However, if the bottom of the bowl is bent inward, the undercut shape of the molded product slips out of the undercut formation portion and is likely to come off.

In addition, when a thermoformed product having an undercut forming portion is manufactured using the above-described female mold for thermoforming, a series of operations are often controlled by a sequencer. In this case, supply and exhaust of the vacuum and release holes,
Since the release and knockout timings are controlled by the same sequencer, the present invention can be applied as such a control program, and instead of implementing the present invention as a medium recording such a control program. There is no.

Of course, the recording medium may be a magnetic recording medium, a magneto-optical recording medium, or any recording medium to be developed in the future. Also, the duplication stages of the primary duplicated product, the secondary duplicated product, and the like are equivalent without any question. In addition, the present invention is not limited to the case where the present invention is used even when the supply is performed using a communication line. further,
The concept of the present invention is not completely different even when part is software and part is realized by hardware, and part is stored on a recording medium and read as needed as needed. Such a form may be adopted.

[0016]

As described above, according to the present invention, the undercut-forming portion is assisted while releasing the undercut-forming portion while bending the undercut-forming portion of the molded product. A method of manufacturing a thermoformed product having an undercut shape that can be manufactured by molding can be provided. Further, according to the second aspect of the invention, it is possible to form a shape that diverges from the bottom of the bowl toward the back, that is, a shape like a thread bottom.

Further, according to the invention according to claim 3,
Even if the vacuum / release holes are concentrated at the bottom of the bowl, the portion near the opening end of the bowl-shaped concave shape can be formed into a desired shape. Further, according to the invention according to claim 4,
Since the supply of the compressed air is started prior to the knockout, the undercut-shaped portion can be reliably bent. On the other hand, according to the fifth and sixth aspects of the present invention, it is possible to provide a thermoforming female mold that can easily hold the mold release.

According to the invention of claim 7, it is possible to provide a thermoforming female mold capable of forming a divergent undercut shape at the bottom of the bowl.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a main part of a thermoforming apparatus according to an embodiment of the present invention, and FIG. 2 is a timing chart showing an operation sequence of the thermoforming apparatus.

First, the upper substrate 11 and the lower substrate 31 are fixed to an upper table (not shown) and a lower table (not shown).
At 1 and M2, each can be moved up and down within a predetermined stroke range. A cavity base 12 is bolted to the upper substrate 11 at a predetermined distance, a cavity holder 13 is bolted to the cavity base 12, and a plurality of main cavities 21 are fixed to the cavity holder 13.
Is installed. As shown in FIG. 3 in an enlarged manner, the thermoforming female mold 20 includes a main cavity 21 and a bottom mold 22.
It is composed of The main cavity 21 is formed in a generally bowl-shaped concave shape.
A substantially cylindrical bottom mold 22 is vertically movably supported so as to close the through-hole 21a.

The shape of the bowl is continuous from the opening end to the bottom wall surface through the peripheral wall surface. The through-hole 21a is formed in the bottom wall surface, and as the opening diameter narrowed once from the peripheral wall surface goes toward the depth direction. After the diameter is expanded in a divergent shape, the diameter is reduced again to about the initial opening diameter, and thereafter it is formed to have a constant diameter. The portion that expands in a divergent shape here is a portion that forms the outer shape of the thread bottom formed at the bottom of the bowl, and forms an undercut in the die-cutting direction.

The bottom mold 22 forms the concave bottom surface, and has two steps 22a formed concentrically on the bottom surface. The outer shape of the bottom die substantially matches the constant inner diameter portion of the through hole 21a, but the opening end diameter of the through hole 21a is slightly smaller than the same constant inner diameter portion. The bottom mold 22 penetrates the cabinet base 12 and is supported by the bottom mold base 14 held between the cabinet base 12 and the substrate 11. The bottom type base 14 can be moved up and down within a predetermined stroke range by the driving device M3, and the stroke extends from a position retracted by almost the height of the yarn bottom from the end of the yarn bottom to the start end of the yarn bottom. The distance at which the bottom surface of the mold 22 reciprocates.

On the inner peripheral surface of the thermoforming female mold 20, a vacuum
Although a large number of release holes 23 are arranged, they are particularly concentrated on the bottom of the bowl, which is a portion where the above-mentioned undercut is formed. Referring to FIG. 3, it can be seen that it is formed at a portion continuous from the peripheral wall surface to the bowl bottom portion, at a portion at the outermost end of the yarn bottom, and at a portion of the two-step portion 22 a. This vacuum / release hole 23
The number and arrangement of the bottom parts of the molded product when the compressed air is supplied from the vacuum / release hole 23 as described later, in addition to the minimum condition of being closely adhered along the inner peripheral shape of the bowl shape, Is determined under such a condition that it can be bent inward.

These vacuum / release holes 23 are mutually connected to the bottom mold 2.
2 and a pressure control mechanism (not shown) through a hollow path formed in the bottom mold base 14 and an external pressure control mechanism (not shown) through control valves V1 and V2. As shown in the timing chart of FIG. 2, a negative pressure is supplied or a compressed air is supplied.
The timing for supplying a negative pressure to the vacuum / release hole 23 is indicated as “vacuum / release hole (vacuum)”, and the timing for supplying compressed air is referred to as “vacuum / release hole (release)”.
Is displayed. On the other hand, such a vacuum / release hole 23 is not formed at the open end of the main cavity 21. Instead, the air communication hole 24 is formed at the concave portion along the shape of the open end.
Is formed. Therefore, even when pressure is applied from the plug side during molding as described later, no air pool is formed between the molded body and the main cavity 21.

In addition, a knockout plate 15 is arranged on the side of the lower substrate 31 in the cabinet holder 13, and can be separated and approached by a predetermined stroke when the mold is released by the driving device M4. On the side of the lower substrate 31, a plug base 32 is bolted with a spacer 33 interposed therebetween to form a closed pressure box as a whole. The plug 41 is located at a position facing the main cavity 21.
Are fixed by bolts, and a communication port 32a is formed around the portion where the plug 41 is planted. Further, by disposing the seal plate 34 surrounding the plug 41 and having a through hole so as to face the opening end of the main cavity 21, in a state where the upper substrate 11 and the lower substrate 31 are close to each other, A sealed space communicating with the compressed air box is formed while sandwiching a thermoplastic resin plate between the seal plate 34 and the main cavity 21.
The compressed air box is also connected to the pressure control mechanism via the control valves V3 and V4. The pressure control mechanism supplies a negative pressure or a compressed air as shown in the timing chart of FIG. It is supposed to be. The drive devices M1 to M4 and the control valves V1 to V4 are controlled by the drive control device C1 including a sequencer or the like in accordance with the timing chart of FIG.

Next, the operation of this embodiment having the above configuration will be described with reference to the timing chart of FIG.
Note that a heater, a feeder, and the like are arranged at the preceding stage of the thermoforming device, but a general device can be used, and a description thereof will be omitted. First, at timing T1, the upper table starts lowering, and the upper substrate 11 and the thermoforming female mold 20 fixed to the upper table start lowering. The lowering of the upper table ends at timing T3,
The lower table starts rising from timing T2 earlier than that, and timing T4 is slightly delayed after the lowering of the upper table is completed.
Complete the ascent with.

FIG. 4 shows the components in the mold closed state at the timing T4, but omits only the thermoplastic resin plate. At this time, the bottom mold 22 is at a position (ascending position) recessed from the main cavity 21. Further, the thermoplastic resin plate is sandwiched between the opening end of the main cavity 21 and the seal plate 34 in a circular shape, and the plug 41 extends inward of the main cavity 21 at the center. At timing T50, compressed air is supplied from the compressed air box side, and negative pressure is simultaneously supplied to the vacuum / release hole 23. Then, while being pressed from the plug 41 side into the main cavity 21, the thermoplastic resin plate is sucked into the vacuum / release hole 23 to reliably form even the recessed detailed shape of the female inner peripheral surface. . FIG. 5 is a sectional view focusing on the thermoplastic resin plate formed in this manner. In this state, although the outer shape of the thread bottom formed at the bottom of the bowl is formed, the original bowl bottom has an intermediate shape formed at a position deeper than the thread bottom.

However, slightly later than the timing T50, at the timing T51, as shown in FIG.
Is lowered by the actuator, and the bottom mold 22 is lowered in the through hole 21a. As the bottom mold 22 descends in the through hole 21a, the original bowl bottom is moved to the opening end side of the through hole 21a, and the bottom of the yarn bottom is moved through the through hole 21a.
The portion that continued to the bottom of the bowl along the inner peripheral surface of the is turned up to form a new inner wall surface of the yarn bottom. In addition, bottom mold 2
2 is performed with a slight delay, the thermoplastic resin plate itself is still in a softened state, and the lower end of the bottom mold 22 is slightly larger in diameter than the opening end diameter of the through hole 21a as described above. As a result, the peripheral edge of the bowl bottom and the starting end of the yarn bottom, which are in the softened state, are pressed together and welded, and the gap is eliminated. This state is shown in FIG.

Although a stepped portion is also formed at a portion near the opening end of the main cavity 21, the vacuum / release hole 23 is concentrated at the bottom of the bowl and is not formed at the stepped portion. However, instead of the step portion, the air communication hole 24 is formed, and when the thermoplastic resin plate is pressed against the step portion at a portion near the opening end when the compressed air is supplied from the plug 41 side, the meantime is increased. Is exhausted to the outside through the air communication hole 24. Therefore, it is closely adhered and cured along the inner peripheral surface shape of the main cavity 21.

At a timing T6 after a predetermined curing time, the supply of compressed air from the compressed air box is stopped, and the compressed air is exhausted by communicating with the outside air. At the timing T7, the supply of the negative pressure to the vacuum / release hole 23 is stopped and the bottom mold 22 is raised. FIG. 8 shows a cross section of the molded body immediately after the bottom mold 22 is raised. Since the diameter of the through-hole 21a expands in a divergent shape, the yarn bottom surely has an undercut shape. In this state, even if knockout is performed, it is not always possible to reliably release the mold. And if there is any one that cannot be released from the mold, all the other molded bodies will be damaged in the next feeding step.

In this embodiment, prior to separating the upper table and the lower table, first, compressed air is supplied from the vacuum / release hole 23 at timing T8. Before the mold release, the bowl-shaped molded body is pressed against the open end. In this state, the compressed air is sent to the bottom of the bowl, so that the bowl bottom naturally tends to bend inward. Then, the lower table is started to be lowered at timing T9 slightly later than this. FIG. 9 shows a state in which the bottom of the bowl is going to bend inward. Even if the thread bottom has an undercut shape, if the center of the bottom of the bowl is pushed down, the periphery thereof is slightly drawn inward. When pulled in in this manner, the end portion of the yarn bottom is also drawn inward, so that the yarn bottom can be slipped out of the undercut formation portion. When the lower table is lowered in this state, the seal plate 34 is lowered, and the lower end of the molded body is free. In most cases, the thread bottom comes off at this point,
Since the knockout plate 15 is also pushed down at the timing T10 which is later than this, the release is surely completed.

When the knockout plate 15 starts to be pushed down, the upper table also starts to rise, but it starts to rise slowly at first, and the speed of the molded body is reduced from the timing T11 when it is considered that the mold release is completely completed. Raise and rise. At the same time as the release, the supply of the compressed air from the vacuum / release hole 23 is stopped at the timing T12. When the lower table starts to lower with the lowering of the knockout plate 15, it is not necessary to keep the compressed air box in communication with the atmosphere, and the exhaust is stopped at the timing T10. When the upper table and the lower table have completely stopped, the knockout plate 15 is also returned to the original position close to the cabinet holder 13. FIG.
0 means that the upper and lower tables are completely stopped,
The state at the time when the knockout plate 15 is not pulled back is shown.

The above process is performed as one thermoforming cycle to produce a bowl-shaped molded body. In addition, if the yarn bottom spreading outward from the bottom of the bowl can be formed in this way, the bowl looks more like a bowl and the texture is improved. Further, the yarn bottom portion has sufficient strength because the thermoplastic resin plate is doubled, and there is no gap on the inner peripheral surface of the bowl communicating with the inside of the yarn bottom, so that hygiene is good. Since the function of accelerating the release is to bend the bottom of the bowl, only the supply holes for the release may be concentrated on the bottom of the bowl. However, if a vacuum hole is separately formed, the compressed air leaks out. Therefore, it is best to make the vacuum hole and the release hole common.

Incidentally, in the above-described embodiment,
Although an example in which the yarn bottom is formed by undercut has been described, a method in which the undercut shape can pass through the undercut forming portion of the mold by bending the bowl is also applicable. For example, even when a male mold is used, if compressed air is supplied from the vicinity of the undercut shape, the mold is bent in a direction away from the mold, and this bending direction is exactly the direction that easily slips from the undercut formation site. .

Further, in this embodiment, the molded body having the undercut shape is formed. However, even if there is no undercut shape, there is an effect that the mold is easily released. This is because the bottom of the bowl is deflected before releasing from the mold, so that the bowl is easily detached in the subsequent releasing step. As described above, when forming the undercut yarn bottom at the bottom of the bowl, the vacuum / supply vacuum is applied.
Since the release hole is concentrated on the bottom of the bowl, when the pressurized air is supplied from the vacuum / release hole at the time of release, the bottom of the bowl is bent inward, and the undercut shape of the molded product is removed from the undercut formation site, Can be released from the mold.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a thermoforming device according to an embodiment of the present invention.

FIG. 2 is a timing chart showing an operation sequence of the thermoforming apparatus.

FIG. 3 is an enlarged schematic sectional view of a female mold of the thermoforming device.

FIG. 4 is a sectional view of a main part of the thermoforming device in a mold-clamped state.

FIG. 5 is a schematic sectional view of a molded body immediately after the start of molding.

FIG. 6 is a sectional view of a main part of the thermoforming apparatus in a state where a bottom mold is lowered.

FIG. 7 is a schematic sectional view of the molded body in the same state.

FIG. 8 is a schematic cross-sectional view of a molded body in a state where a bottom mold is raised again.

FIG. 9 is a schematic cross-sectional view of a molded body in a state where the bottom of the bowl is bent by supplying compressed air from a vacuum / release hole.

FIG. 10 is a cross-sectional view of a main part of the thermoforming apparatus in a state where a knockout plate is pushed down.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Upper board 12 ... Cabinet 13 ... Cabinet holder 14 ... Bottom mold base 15 ... Knockout plate 20 ... Female mold for thermoforming 21 ... Main cavity 21a ... Through-hole 22 ... Bottom mold 22a ... Step part 23 ... Vacuum / release hole Reference numeral 24: air communication hole 31: lower substrate 32: plug base 32a: communication port 33: spacer 34: seal plate 41: plug

Continuing from the front page (72) Inventor Kenichi Mizoguchi 158 Toro-cho, Togo-cho, Aichi-gun, Aichi Prefecture 247 Kitayama, F-term in the Asano Research Laboratories Co., Ltd. MB01 MC03 MK15

Claims (7)

[Claims] 1. An undercut shape of a molded product by arranging vacuum and release holes in the vicinity of an undercut forming portion of a molding die for thermoforming and supplying compressed air from the vacuum and release holes at the time of release. A method for producing a thermoformed product having an undercut shape, wherein the method is to assist mold release from an undercut forming portion while bending the portion. 2. The method for producing a thermoformed product having an undercut shape according to claim 1, wherein the undercut forming portion is formed while forming the thermoforming mold with a female mold having a bowl-shaped concave shape. Is formed in a divergent shape from the bottom of the bowl-shaped concave bowl toward the back side, and the pressurized air is supplied from the vacuum / release hole to bend the bottom of the molded product from the undercut forming portion while bending. A method for producing a thermoformed product having an undercut shape, characterized by assisting a mold. 3. The method of manufacturing a thermoformed product having an undercut shape according to claim 2, wherein the female mold has a bowl-shaped concave shape while forming the vacuum / release hole at the bottom of the bowl. A method for producing a thermoformed product having an undercut shape, wherein an air communication hole is formed in a portion near an opening end, and compressed air is supplied from the inside of a bowl of the molded product during molding. 4. The method of manufacturing a thermoformed product having an undercut shape according to any one of claims 1 to 3, wherein supply of compressed air from the vacuum / release hole is started prior to knockout. A method for producing a thermoformed product having an undercut shape. 5. A thermoforming female formed in a bowl-shaped concave shape, wherein vacuum / release holes are concentrated at the bottom of the bowl, and an air communication hole is arranged at a portion near the opening end. Type. 6. The female mold for thermoforming according to claim 5, wherein a pressurized air is supplied from a vacuum / release hole centrally arranged at the bottom of said bowl-shaped concave bowl at the time of release. A female mold for thermoforming, characterized in that it comprises a pressurized air supply mechanism for mold release for bending the bottom of the bowl of the molded product inward. 7. The thermoforming female mold according to claim 5, wherein the thermoforming female mold has an undercut forming portion formed so as to diverge from the bottom of the bowl-shaped concave shape. A female mold for thermoforming, characterized in that a pressurized air is supplied from a vacuum / release hole to bend the bottom of the bowl of the molded product and release from the undercut forming portion.