JP2021011048A - Method for thermoforming - Google Patents

Abstract

To enable enhancement of operation efficiency, and reduce a cycle time for thermoforming.SOLUTION: A thermoforming apparatus 1 includes: a first vacuum pump 7A connected to a hotplate 3 of the thermoforming apparatus via a first connection pipe 71, and capable of sucking from a heated surface 3a; a second vacuum pump 7B connected to a molding frame 2 via a second connection pipe 72, and capable of depressurizing in the molding frame 2; and a third switching valve 76 for switching so that both the connection pipes 71 and 72 are communicable. In a method for thermoforming, when the hotplate 3 heats a sheet 4, the third switching valve 76 communicates both the connection pipes 71 and 72, and the fist vacuum pump 7A and the second vacuum pump 7B suck from the heated surface 3a to vacuum, to depressurize an upper space between the sheet 4 and the hotplate 3; when bonding the sheet 4 heated and softened by the hotplate 3, the third switching valve 76 blocks a linkage pipe 75 of both the connection pipes 71 and 72, and the second vacuum pump 7B sucks from the molding frame 2 to vacuum, to depressurize a lower space below the sheet 4.SELECTED DRAWING: Figure 2

Description

The present invention relates to a thermoforming method using a thermoforming apparatus.

Conventionally, as a device for adhering a sheet (skin sheet) to the outer surface of a molding base material, a vacuum press laminated molding device, a thermoforming device by heating a hot plate, and the like are known (see, for example, Patent Document 1).
For example, the vacuum press laminating molding apparatus disclosed in Patent Document 1 includes upper and lower chambers. The lower chamber can accommodate the molded base material and can set a sheet on the peripheral edge on the upper chamber side. The upper chamber has a hot plate provided with a heater above, and is connected to a vacuum tank and a pressurizing tank so that the inside of the chamber including the upper and lower chambers can be evacuated and pressurized. The lower chamber is connected to a vacuum tank, and the inside of the chamber is evacuated.

Then, in the vacuum press laminating molding apparatus described in Patent Document 1, the lower chamber is depressurized while the intermediate chamber is depressurized and the sheet is separated from the base material. As a result, the air between the base material and the sheet is sufficiently eliminated without being hindered by the sheet, and then the upper chamber is pressurized. Therefore, the differential pressure between the upper chamber and the lower chamber causes the sheet to come into close contact with the base material in a vacuum state.

Japanese Patent No. 3102916

However, in the conventional thermoforming method, it is necessary to heat the sheet until the adhesive surface (lower surface) of the sheet is softened to a state required for coating. Therefore, by performing vacuum suction with a vacuum pump on the heating surface of the hot plate and adsorbing the sheet on the heating surface, the heating efficiency of the sheet is improved and the sheet is heated efficiently. However, the vacuum pump has a problem that it takes time to reach the target vacuum degree and the cycle time required for thermoforming becomes long, and there is room for improvement in that respect.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a thermoforming method capable of improving operation efficiency and shortening the cycle time required for thermoforming. ..

In order to achieve the above object, the thermoforming method according to the present invention comprises a base, a mold capable of accommodating the base, and a hot plate capable of bringing a heating surface into close contact with the upper edge of the frame of the mold. And, a sheet is arranged between the mold and the hot plate, heated from above with respect to the sheet, and heated with the hot plate with respect to the molded base material held on the base. It is a thermoforming method using a thermoforming apparatus that molds or adheres the softened sheet to the hot plate, and the thermoforming apparatus is connected to the hot plate by a first connecting pipe, and the heated surface is formed. The first vacuum pump that can be sucked from and the second vacuum pump that is connected to the mold by the second connecting pipe and can depressurize the inside of the mold can communicate with the first connecting pipe and the second connecting pipe. When the sheet is heated by the heating plate, the switching valve communicates the first connecting pipe and the second connecting pipe with the first vacuum pump and the second vacuum. A step of vacuum sucking from the heated surface of the hot plate by a pump to reduce the pressure in the upper space between the sheet and the hot plate, and molding the sheet heated and softened by the hot plate into a mold. Or, at the time of bonding, the communication portion between the first connecting pipe and the second connecting pipe is cut off by the switching valve, and vacuum suction is performed from the mold by the second vacuum pump to lower the seat. It is characterized by having a step of reducing the pressure in the lower space.

In the present invention, the sheet heated and softened by the heated surface of the hot plate is uniformly molded or coated on the surface of the molding base material held on the base housed in the mold. be able to. When the sheet is attracted to the heating surface of the hot plate and heated, the first connecting pipe and the second connecting pipe are communicated by a switching valve, and two pumps, a first vacuum pump and a second vacuum pump, are used. Vacuum suction can be performed from the heating surface to reduce the pressure in the upper space above the sheet. Therefore, the rising time for reaching the target vacuum degree in the upper space at this time can be shortened, the operation efficiency can be improved, and the cycle required for thermoforming can be shortened. It is also possible to increase the degree of vacuum in a certain period of time.

Further, in the present invention, since two vacuum pumps can be used during suction on the heating surface of the hot plate, it is possible to reduce the capacity of the first vacuum pump connected to the hot plate by the first connecting pipe.
On the other hand, when the lower space in the mold, which is the lower side of the seat, is depressurized, the communication portion between the first connecting pipe and the second connecting pipe is cut off by the switching valve, and the hot plate of the seat is used by the first vacuum pump. The side can be depressurized and the lower space can be decompressed by the second vacuum pump.

According to the thermoforming method of the present invention, it is possible to improve the operation efficiency and to achieve the effect of shortening the cycle time required for thermoforming.

It is a vertical sectional view which shows the structure of the thermoforming apparatus by embodiment of this invention. It is a figure which shows the schematic structure of the connection system of a vacuum pump. It is a figure which shows the time chart of the molding operation of the thermoforming method shown in FIG. It is a side view for demonstrating the thermoforming method using the thermoforming apparatus shown in FIG. It is a side view for demonstrating the thermoforming method following FIG. It is a side view for demonstrating the thermoforming method following FIG. (A) to (c) are diagrams showing the operating state of the vacuum pump, and are the diagrams corresponding to FIG. 2. It is a side view which shows the schematic structure of the thermoforming apparatus by an Example. It is a figure which shows the result of an Example, and is the graph which shows the relationship between time t and vacuum pressure Pa.

Hereinafter, the thermoforming method according to the embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, in the thermoforming method according to the present embodiment, a thermoforming apparatus 1 adopting a hot plate heating method is used, and the sheet 4 softened by heating the hot plate 3 is placed in the chamber 2A of the mold 2. This is a method of coating the surface 6a of the molding base material 6 held on the arranged base 5.

Here, as the thermoformed product 6A (see FIG. 5), for example, an automobile part or the like having front and back surfaces is adopted, and the sheet 4 softened by heating is adsorbed on the surface 6a of the resin molded base material 6 to cover it. It is a molded product that is thermoformed by the above. In the present embodiment, the molded base material 6 has a substantially eclipsed tubular shape, but is not particularly limited as long as it can be held on the base 5.

The thermoforming apparatus 1 includes a base 5 for holding a molding base material 6 for covering the sheet 4, a mold 2 having a space (chamber 2A) capable of accommodating the base 5 and the molding base material 6, and a mold 2 The heating plate 3 is provided so that the heating surface 3a can be brought into close contact with the upper edge portion 21a of the frame. In this thermoforming apparatus 1, a sheet 4 is arranged between a mold 2 and a hot plate 3, the sheet 4 is heated from above, and the sheet 4 softened by heating is held on a base 5. It is configured to adhere to the base material 6.

The sheet 4 is a known multilayer sheet having a printing layer and a protective film or carrier film (not shown) provided on the front surface side of the printing layer, and having an adhesive layer on the back surface side of the printing layer. The material of the sheet 4 can be solidified when it is heated and molded by the hot plate 3 and cooled. As the sheet 4, a roll sheet wound in a roll shape may be adopted.
The sheet 4 may be sequentially unwound by a sheet unwinding device (not shown), cut by a sheet cutting portion (not shown), and continuously supplied along the heating surface 3a for each thermoformed product 6A. it can.

The molded base material 6 is the main body of a molded product in which the sheet 4 is coated and adhered and is made of a thermoplastic resin such as a polypropylene resin or a polyethylene resin. However, the material of the molded base material 6 is not limited to the resin.

The formwork 2 is made of a metal member such as stainless steel which is rectangular in top view, and has a bottom plate 20 and a side wall 21 erected upward from the outer peripheral portion of the bottom plate 20. In the inner chamber 2A surrounded by the bottom plate 20 and the side walls 21 on all sides, a base 5 for holding the molded base material 6 is fixed on the bottom plate 20.

The mold 2 is placed on a slidable frame frame 23, and can be moved between a molding position on the lower side of the hot plate 3 and a predetermined retracting position (not shown) away from the molding position. ing. That is, when the mold 2 is in the retracted position, the molding base material 6 is attached to and detached from the base 5 in the chamber 2A of the mold 2. If the formwork 2 itself has a movable structure as described above, the frame frame 23 can be omitted.
Here, the operation of lateral movement of the mold 2 and the drive of the second vacuum pump 7B and the pressurizing pump, which will be described later, are controlled by a control unit (not shown).

A large number of formwork vents 22, 22, ... Are formed at positions of the bottom plate 20 near the side wall 21. These formwork vents 22 are connected to a second vacuum pump 7B provided with a vacuum tank (not shown) via a second connecting pipe 72. At the time of thermoforming by the thermoforming apparatus 1 of the present embodiment, the inside of the chamber 2A can be depressurized by driving the second vacuum pump 7B and sucking vacuum.

The side wall 21 has a height at which the position of the frame upper edge portion 21a is higher than the base 5 housed in the chamber 2A and the molded base material 6 held by the base 5. The frame upper edge portion 21a is a portion that sandwiches the sheet 4 with the hot plate 3. That is, at the upper edge portion 21a of the frame, the hot plate 3A abuts with the sheet 4 in an airtight state, whereby the mold 2 and the hot plate 3 are closed and the inside of the chamber 2A becomes a closed space. Therefore, in a state where the sheet 4 is sandwiched between the frame upper edge portion 21a and the hot plate 3, an airtight space is defined above and below the sheet 4 sandwiched.

The base 5 housed in the mold 2 is made of metal or the like and is arranged on the bottom plate 20. The molded base material 6 is adhered to and held by a holding portion 5a formed in a convex shape upward at the center of the base 5. The holding portion 5a is formed in a shape along the back surface of the molded base material 6 (opposite surface of the covering surface 4a of the sheet 4).

Then, the molded base material 6 held on the base 5 is lowered toward the bottom 20 side by introducing compressed air from the hot plate 3 to the chamber 2A side by a pressure tank or the like (not shown). Covered and glued by.

As shown in FIG. 1, the hot plate 3 is located above the mold 2 arranged at a predetermined molding position, and is provided so as to be movable up and down with respect to the mold 2 by an expansion / contraction device (not shown). .. The hot plate 3 has a heating surface 3a formed of a smooth flat surface on the lower surface side, and is configured to be softened by adsorbing and heating the sheet 4. Specifically, the hot plate 3 is arranged in a state of being moved downward and in close contact with the frame upper edge portion 21a of the mold 2 arranged at the molding position from above.
Here, the operation of moving the hot plate 3 up and down and the drive of the first vacuum pump 7A and the pressurizing pump, which will be described later, are controlled by a control unit (not shown).

A plurality of heaters 31, 31, ... Are provided on the upper surface 3b of the hot plate 3 at predetermined intervals.
On the heating surface 3a of the hot plate 3, a plurality of hot plate ventilation holes 32, 32, ... Opening in the heating surface 3a are formed at predetermined intervals. As shown in FIG. 2, these hot plate ventilation holes 32 are connected to a first vacuum pump 7A provided with a vacuum tank (not shown) via a first connecting pipe 71. At the time of molding, the inside of the chamber 2A can be depressurized by driving the first vacuum pump 7A and sucking vacuum.

Further, the hot plate vent 32 of the hot plate 3 is connected to a pressure pump (not shown) provided with a pressure tank for storing compressed air by a compressor. This pressurizing pump is provided so as to be switchable from the first vacuum pump 7A described above.
With such a configuration, at the time of thermoforming, the connection between the first vacuum pump 7A and the pressurized pump is appropriately switched, the vacuum tank maintained in the vacuum state is opened, and the sheet 4 is vacuum-sucked from the hot plate ventilation hole 32. It is brought into close contact with the heating surface 3a, or compressed air is supplied from the heating surface 3a into the chamber 2A from the heating plate ventilation hole 32 to pressurize the sheet 4 toward the molding base material 6 side. It is possible to lower it. It should be noted that the degree of vacuum may be increased by directly sucking by driving only the first vacuum pump 7A without providing the vacuum tank as in the present embodiment.

As described above, in the thermoforming apparatus 1 of the present embodiment, the first connecting pipe 71 connecting the hot plate 3 and the first vacuum pump 7A is provided with a first switching valve 73 for opening and closing the flow path. The second connecting pipe 72 that connects the frame 2 and the second vacuum pump 7B is provided with a second switching valve 74 that opens and closes the flow path. Then, the position of the first connecting pipe 71 on the first vacuum pump 7A side of the first switching valve 73 and the position of the second connecting pipe 72 on the second vacuum pump 7B side of the second switching valve 74 are connected. A pipe 75 is provided. The connecting pipe 75 is provided with a third switching valve 76 that opens and closes the flow path.
For example, when the upper space K1 on the upper side of the seat 4 is depressurized in the hot plate ventilation hole 32 of the hot plate 3, the second switching valve 74 is closed and the first switching valve 73 and the third switching valve 76 are opened. Therefore, it is possible to drive two units, the first vacuum pump 7A and the second vacuum pump 7B, to perform vacuum suction.

Although not particularly shown, the thermoforming apparatus 1 of the present embodiment is provided with a cutting jig for trimming an unnecessary portion of the sheet 4 coated on the molding substrate 6. This cutting jig is provided, for example, on the bottom plate 20 of the mold 2, and the blade portion is arranged upward, and the cutting jig is vertically oriented with a predetermined interval with respect to the molding base material 6 held on the base 5. It is located at a position facing the. The cutting jig is configured in this way, and the blade portion of the cutting jig hits the sheet 4 coated on the molding base material 6 to cut and trim.

Next, a thermoforming method for molding the thermoformed product 6A using the thermoforming apparatus 1 described above will be described using the operation flow of FIG. 3 and the like. Here, the position of the mold 2 shown in FIG. 4 is set as the initial position where thermoforming is performed. Note that FIG. 3 is an example of a thermoforming method using the thermoforming apparatus 1, and the time of each operation, the start time, the end time, the timing of each operation, and the like can be appropriately changed.

First, the molding base material 6 is held by the holding portion 5a of the base 5 arranged on the bottom plate 20 of the mold 2 in a state where the mold 2 is located at the retracted position retracted from the above-mentioned initial position. (See FIG. 4). After that, as shown in FIG. 4, the mold 2 is moved to the initial position and placed below the hot plate 3 in the raised position. Subsequently, the sheet 4 is supplied in a state of extending along the frame upper edge portion 21a of the mold 2 and being stretched in the plane direction. At this time, the heating surfaces 3a of the hot plate 3 face each other at a predetermined interval above the sheet 4.

Next, as shown in FIG. 1, a step of heating the sheet 4 by the hot plate 3 is performed. Specifically, the hot plate 3 is lowered, and the outer peripheral portion of the heating surface 3a is brought into contact with the frame upper edge portion 21a of the mold 2 from above via the sheet 4. As a result, the sheet 4 is in a state of being sandwiched by the frame upper edge portion 21a and the hot plate 3 without a gap over the entire circumference. Further, the inside of the chamber 2A is sealed by closing the upper opening of the mold 2. As a result, the sheet 4 is in contact with the heating surface 3a of the hot plate 3. Then, the upper and lower spaces (upper space K1 and lower space K2) sandwiching the sheet 4 are isolated from each other.
The sheet 4 may be cut into a predetermined size by a cutting means (not shown) after the roll-shaped sheet 4 is unwound on the frame upper edge portion 21a, sandwiched by the hot plate 3. Alternatively, a sheet 4 having a preset size may be arranged on the frame upper edge portion 21a and sandwiched between the hot plates 3.

After the hot plate 3 is lowered, the space above the sheet 4 (upper space K1) is evacuated by sucking from the hot plate ventilation hole 32 of the hot plate 3 (upper vacuum operation S1: ON). The heating surface 3a of the hot plate 3 is heated by the heater 31, and the heating surfaces 3a are operated in the hot plate 3 by operating both vacuum pumps 7A and 7B shown in FIG. 2 through the plurality of hot plate ventilation holes 32, 32, ... The upper space K1 between the sheet 4 and the sheet 4 is vacuum-sucked to reduce the pressure, and the sheet 4 is adsorbed on the heating surface 3a to be heated. At this time, the sheet 4 is heated by coming into contact with the heating surface 3a.

Specifically, in the upper vacuum operation S1, as shown in FIG. 7A, the first vacuum pump 7A is opened by opening the first switching valve 73, closing the second switching valve 74, and opening the third switching valve 76. A predetermined time (this is the upper vacuum time) via the first connecting pipe 71 and the connecting pipe 75 using two units of the second vacuum pump 7B (time in the range shown as “two hot plate vacuums” in FIG. 3). Suction only (T1). As a result, the sheet 4 is adsorbed on the heating surface 3a and heated. Here, in the first connecting pipe 71, the second connecting pipe 72, and the connecting pipe 75 of FIGS. 7A to 7C, the thick wire indicates that the vacuum pumps 7A and 7B are in communication with each other. ..

Then, at the timing after the upper vacuum operation S1 is started (ON), the space under the seat 4 (lower space K2) is set to a predetermined time (this is set as the lower pressure air time T2) by using a compressed air pump (not shown). ) Is compressed (lower pressure air operation S2: ON). The lower compressed air operation S2 ends earlier than before the upper vacuum operation S1 ends, and the lower compressed air time T2 is shorter than the upper vacuum time T1. By performing the lower compressed air in the lower compressed air operation S2, the sheet 4 is pressed upward from the lower side and further adheres to the heating surface 3a reliably. Then, when the predetermined lower pressure air time T2 elapses, the vacuum pumps 7A and 7B are stopped, or the vacuum pumps 7A and 7B are set to atmospheric pressure to exhaust the air in the lower space K2 of the seat 4 and operate the lower pressure air. S2 ends (lower pressure air operation S2: OFF).

Next, at the timing when the lower pressure air operation S2 is completed, as shown in FIG. 7B, the two vacuum pumps 7A and 7B used in the upper vacuum operation S1 are replaced with one of the first vacuum pumps 7A (FIG. 3). Switch to the time in the range indicated as "1 hot plate vacuum"). That is, the third switching valve 76 is closed, and the vacuum suction by the heating surface 3a is performed only by the first vacuum pump 7A via the first connecting pipe 71 (upper direct vacuum operation S11: ON). At this time, since the second switching valve 74 of the second connecting pipe 72 connected from the second vacuum pump 7B to the mold 2 is closed, the vacuum suction operation by the second vacuum pump 7B is not performed.

Next, a step of coating the surface 6a of the molded base material 6 with the sheet 4 softened by heating by the hot plate 3 is performed.
First, by exhausting the lower space K2 on the lower side of the seat 4 (lower exhaust operation S3: ON) as described above, the lower space K2 is compressed and opened. Further, as shown in FIGS. 5 and 7 (c), a plurality of form vent holes 22, 22 formed in the bottom plate 20 of the form 2 by the second vacuum pump 7B by opening the second switching valve 74. A high degree of vacuum is achieved by vacuum suctioning from, ..., and depressurizing (lower vacuum operation S4: ON, lower direct pull vacuum operation S41: ON). The time during which the lower vacuum operation S4 operates at this time is defined as the lower vacuum time T3. At this time, the time is in the range shown in FIG. 3 as “1 hot plate vacuum, 1 mold vacuum”.

Then, when the upper vacuum time T1 elapses, the first switching valve 73 is closed and the upper space K1 is exhausted to open the vacuum (upper vacuum opening operation S5: ON, upper vacuum opening operation S6: ON). As a result, the vacuum suction by the hot plate 3 is stopped. That is, while maintaining the decompression operation of the lower vacuum operation S4, the suction operation of the sheet 4 is stopped, and the upper space K1 between the hot plate 3 and the sheet 4 is opened to the atmosphere.

Further, after the elapse of the lower vacuum time T3, the upper space K1 is compressed (upper compressed air operation S7: ON). The time during which the upper compressed air operation S7 operates at this time is defined as the upper compressed air time T4.
By depressurizing the lower space K2 and opening the upper space K1 in a vacuum in this way, the lower space K2 is in a high vacuum state, and as shown in FIG. 5, the sheet adsorbed on the heating surface 3a of the hot plate 3 4 moves away from the heating surface 3a and further downward. That is, after the sheet 4 adsorbed on the heating surface 3a of the hot plate 3 is heated to a predetermined temperature and a predetermined time (upper vacuum time T1) elapses, the vacuum suction by the hot plate ventilation hole 32 of the hot plate 3 is stopped. The suction operation of the sheet 4 is stopped. As a result, the space between the hot plate 3 and the sheet 4 is opened to the atmosphere, so that a pressure difference is generated between the upper space K1 and the lower space K2 sandwiching the sheet 4. Then, the sheet 4 softened by heating moves away from the heating surface 3a of the hot plate 3 toward the bottom plate 20 (molding base material 6) side, and is pressed in close contact so as to cover the surface 6a of the molding base material 6. , The sheet 4 covers the surface 6a of the molded base material 6 and is adhered.

After that, the coated sheet 4 is trimmed by cutting the coated sheet 4 at an appropriate cut line using a cutting jig (not shown). Here, when the molding base material 6 is pressed against the blade of the cutting jig in compressed air (upper compressed air operation S7: ON), the base material holding is switched from ON to OFF.
When the space between the hot plate 3 and the sheet 4 is opened to the air, the vacuum tank connected to each of the vacuum pumps 7A and 7B is switched to the pressurized tank, so that the hot plate vent hole of the hot plate 3 is opened. Compressed air may be sent out from 32 to pressurize the upper space.

Next, as shown in FIG. 6, a step of removing the thermoformed product 6A, which is obtained by coating the molded base material 6 with the sheet 4 and thermoforming, from the base 5 is performed. Specifically, the hot plate 3 is raised and moved above the mold 2, and the mold 2 is moved from the molding position to the retracted position in a plan view. Then, in the mold 2 located at the retracted position, the thermoformed product 6A is separated from the base 5 and removed.
The thermoformed product 6A is completed by the above operation, and a series of molding operations for thermoforming one thermoformed product 6A is completed.

Next, the operation of the thermoforming method described above will be described with reference to the drawings.
In the present embodiment, as shown in FIGS. 1 and 5, a molded base material in which the sheet 4 heated and softened by the heating surface 3a of the hot plate 3 is held on the base 5 housed in the mold 2 is held. The surface 6a of 6 can be uniformly coated over the entire surface.
When the sheet 4 is adsorbed on the heating surface 3a of the hot plate 3 and heated, as shown in FIG. 7A, the first switching valve 73 is opened, the second switching valve 74 is closed, and the third switching valve 76 is closed. The first connecting pipe 71 and the second connecting pipe 72 are communicated with each other via the connecting pipe 75, and vacuum is evacuated from the heating surface 3a using two pumps, the first vacuum pump 7A and the second vacuum pump 7B. The upper space K1 on the upper side of the sheet 4 can be depressurized by suction. Therefore, the rising time for reaching the target vacuum degree in the upper space K1 at this time can be shortened, the operation efficiency can be improved, and the cycle required for thermoforming can be shortened. It is also possible to increase the degree of vacuum in a certain period of time.

Further, in the present embodiment, since the two vacuum pumps 7A and 7B can be used during suction on the heating surface 3a of the hot plate 3, the capacity of the first vacuum pump 7A connected to the hot plate 3 by the first connecting pipe 71. Can be made smaller.

On the other hand, when the lower space K2 in the mold 2 on the lower side of the seat 4 is depressurized, the first switching valve 73 and the second switching valve 74 are opened, and the third switching valve 76 is closed. The communication portion (connecting pipe 75) of the connecting pipe 71 and the second connecting pipe 72 is cut off, the hot plate side of the sheet 4 is depressurized by the first vacuum pump 7A, and the lower space K2 is depressurized by the second vacuum pump 7B. Can be done.

As described above, in the thermoforming method according to the present embodiment, it is possible to improve the operation efficiency and shorten the cycle time required for thermoforming.

Next, an example for supporting the effect of the thermoforming method according to the above-described embodiment will be described below.

(Example)
In this embodiment, the thermoforming apparatus 100 shown in FIG. 8 described above is used, vacuum suction is performed in a case using one vacuum pump and a case using two vacuum pumps, and the degree of vacuum on the hot plate side (FIG. 9). The vacuum pressure P ₀ of the vacuum pump and the time t when the target vacuum degree was reached in (the solid line shown in)) were measured, and the effect of the above-described embodiment was confirmed.
The thermoforming apparatus 100 shown in FIG. 8 has a planar shape of 200 mm in length and 200 mm in width on the heating surface of the hot plate 101, and adopts a mold 102 having a length of 200 mm, a width of 200 mm and a height of 50 mm. There is. Reference numeral 103 shown in FIG. 8 is a sheet.

FIG. 9 shows a vacuum on the hot plate side when the hot plate 101 side of the sheet 103 is vacuum-sucked and the mold 102 side is vacuum-sucked with the sheet 103 sandwiched between the mold 102 and the hot plate 101. The degree is shown by a solid line, and the degree of vacuum on the formwork side is shown by a broken line. Then, at the hot plate side vacuum degree, the time t (seconds) until the target vacuum degree was reached and the vacuum pressure P ₀ (Pa) of the vacuum pump were measured.
In the graph of FIG. 9, the vacuum pressure P _{0 on} the vertical axis is 1000 Pa on the upper side of the paper surface, indicating that the vacuum pressure P ₀ increases toward the lower side of the paper surface. As the two vacuum pumps used in this embodiment, the hot plate vacuum pump A connected to the hot plate 101 side has a capacity of 300 L / min, and the mold vacuum pump B has a capacity of 1000 L / min. I'm using something.

The vacuum suction method of the hot plate 101 was carried out in two cases in which the usage states of the two vacuum pumps A and B were changed.
In the first case, the hot plate vacuum pump A connected to the hot plate 101 and the mold vacuum connected to the mold 102 until the hot plate 101 reaches the target vacuum pressure (hot plate vacuum reaching pressure P11). Two vacuum pumps of pump B are connected to the hot plate 101 to perform vacuum suction, and after reaching the hot plate vacuum reaching pressure P11, the mold side vacuum pump B is connected from the hot plate 101 to the mold 102. This is a case of switching.
The second case is a case in which only the hot plate side vacuum pump A is connected to the hot plate 101, and the mold side vacuum pump B is connected only to the mold 102 to perform vacuum suction. That is, only one hot plate vacuum pump A is connected to the hot plate 101 until the hot plate 101 reaches the target vacuum pressure (hot plate vacuum reaching pressure P11).

In the results of FIG. 9, in the heat plate side vacuum of the first case and the second case, by driving the vacuum pump, the vacuum pressure P ₀ of the heating plate 101 at time t11 since the vacuum suction against the heating plate 101 is It started to rise, and the hot plate 101 reached the target vacuum degree at time t12. In the first case using the two vacuum pumps A and B, the hot plate vacuum ultimate pressure P11 when the target vacuum degree was reached was 400 Pa. The time to reach the target vacuum degree T11 (t12-t11) from the time t11 when the vacuum pressure rise started was 4 seconds. On the other hand, in the second case using one vacuum pump A, the hot plate vacuum ultimate pressure P11 when the target vacuum degree was reached was 500 Pa. Further, the vacuum degree arrival time T11 (t12-t11) at which the target vacuum degree was reached from the vacuum pressure rise start time t11 was 5 seconds.

In the hot plate side vacuum degree, molding is started at a timing when a predetermined time elapses after reaching the target vacuum degree. In the case of the first case, the vacuum pump A for the hot plate continues vacuum suction to the hot plate 101, and the connection of the vacuum pump B for the mold is switched from the hot plate 101 side to the mold 102 side. Molding is started after vacuum suction is performed on the frame 102 for a predetermined time.

As described above, the vacuum degree reaching time T11 at the hot plate side vacuum degree is shortened by 1 second in the first case using the two vacuum pumps A and B as compared with the second case of the one vacuum pump A. I was able to confirm. That is, it was found that the ascending time can be shortened and the operating efficiency can be improved by using the two vacuum pumps A and B until the target vacuum degree on the hot plate 101 side is reached.
Furthermore, it was also confirmed that the capacity of the hot plate vacuum pump can be made smaller than the capacity of the formwork vacuum pump due to the effect of shortening the rise time for reaching the degree of vacuum on the hot plate 101 side as described above. ..

Although the embodiment of the thermoforming method according to the present invention has been described above, the present invention is not limited to the above embodiment and can be appropriately changed without departing from the spirit of the present invention.

For example, in the present embodiment, the hot plate 3 is configured to move up and down, but the present invention is not limited to this, and the mold 2 and the hot plate 3 may be relatively close to each other in the vertical direction. The position of the hot plate 3 may be fixed, and the mold 2 may be provided so as to be vertically movable with respect to the hot plate 3. Alternatively, of course, the mold 2 and the hot plate 3 may be configured to be movable in the vertical direction. Therefore, the position of the mold 2 is not limited, and the hot plate 3 and the mold 2 may be provided so as to overlap each other in a plan view during thermoforming.

Further, in the thermoforming method of the present embodiment, each operation (upper vacuum operation S1, lower pressure air operation S2, lower exhaust operation S3, lower vacuum operation S4, upper exhaust operation S5, upper vacuum opening operation S6, upper pressure air operation S7, The time, timing, etc. of the upper direct vacuum operation S11 and the lower direct vacuum operation S41) can be set according to the conditions such as the material and thickness of the sheet 4, the type of adhesive, and the material of the molded base material 6. it can.

In this embodiment, the thermoforming method of coating and adhering the sheet 4 to the molding base material 6 is targeted, but not only in the case of such laminating molding but also the carrier film on the uppermost layer of the sheet is peeled off by transfer trimless. It also includes a case where only the decorative layer (corresponding to the sheet of the present invention) is transferred to the molded base material.

Further, in the present embodiment, the thermoforming method of coating the molded base material 6 with the sheet 4 softened by the hot plate 3 is targeted, but the present invention is not limited to the sheet coating. For example, it is also possible to mold a thermoformed product for mold shaping, in which a sheet 4 softened by heating of a hot plate 3 is shaped using a base 5 as a mold. Also in the case of this mold shaping, the thermoforming method can be carried out by the same method as the above-described embodiment.

Further, the configuration of the mold 2 (including the base 5 and the frame frame 23), the shape and size of the hot plate 3, and the sheet cutting means can be appropriately set.

Further, the trimming step of the sheet 4 may be performed at the same time as the molding as in the present embodiment, or may be performed in a separate step after the molding.

In addition, it is possible to replace the components in the above-described embodiment with well-known components as appropriate without departing from the spirit of the present invention.

1 Thermoforming equipment 2 Mold 2A Chamber 3 Hot plate 3a Heating surface 4 Sheet 5 Base 6 Molding base material 6A Thermoformed product 6a Surface 7A 1st vacuum pump 7B 2nd vacuum pump 20 Bottom plate 21 Side wall 21a Frame upper edge 22 Form ventilation hole 32 Hot plate ventilation hole 71 1st connection pipe 72 2nd connection pipe 73 1st switching valve 74 2nd switching valve 75 Connection pipe 76 3rd switching valve K1 Upper space K2 Lower space

Claims (1)

It has a base, a mold capable of accommodating the base, and a hot plate capable of bringing a heating surface into close contact with the frame upper edge of the mold, and is between the mold and the hot plate. The sheet is placed on the sheet, heated from above with respect to the sheet, and the sheet heated and softened by the hot plate is molded or adhered to the molding base material held on the base. It is a thermoforming method using a thermoforming device.
The thermoforming apparatus is connected to the hot plate by a first connecting pipe, is connected to a first vacuum pump capable of sucking from the heating surface, and is connected to the mold by a second connecting pipe, and can reduce the pressure inside the mold. A second vacuum pump and a switching valve for switching between the first connecting pipe and the second connecting pipe so as to be communicable are provided.
When the sheet is heated by the hot plate, the first connecting pipe and the second connecting pipe are communicated by the switching valve, and the heating surface of the hot plate is communicated by the first vacuum pump and the second vacuum pump. Vacuum suction from the sheet to reduce the pressure in the upper space between the sheet and the hot plate.
When the sheet heated and softened by the hot plate is molded or bonded, the switching valve cuts off the communication portion between the first connecting pipe and the second connecting pipe, and the second vacuum. A step of vacuum suctioning from the mold with a pump to reduce the pressure in the lower space under the sheet.
A thermoforming method characterized by having.

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