JP7345946B1 - thermoforming equipment - Google Patents

Abstract

[Problem] To provide a thermoforming device that is unlikely to cause misalignment. In a thermoforming apparatus 100 that heats a resin sheet S using a heating means 110 and shapes the resin sheet S using a mold 200, the resin sheet S is disposed at the upper part. Pressure control means is held between the first chamber 101 and the second chamber 102 disposed at the bottom, and controls the inside of the first chamber 101 or the second chamber 102 to an arbitrary pressure when molding the resin sheet S. 270, the pressure control means 270 controls the first valve V1 connected to the first chamber 101 or the second valve V2 connected to the second chamber 102, and controls the first chamber 101 or the second valve V2 in multiple stages. Switch the internal pressure of the second chamber. [Selection diagram] Figure 8

Description

The present invention relates to a technology for thermoforming resin sheet materials, and specifically, when molding resin sheet materials by heating them with a radiant heating device, the molding accuracy is improved by changing the heating conditions depending on the part. It is a technology that allows

Thermoforming machines are used to mold heated and softened resin sheets to make food containers and blister packs. It is also used to make various plastic products such as automobile parts, home appliances, and industrial trays. In recent years, it has also been used for applications such as transferring patterns using thermoforming machines, adhering to the outer surface of molding substrates, and for molding that requires positional accuracy.

Patent Document 1 discloses a technique related to a method for molding a decorative molded product. After heating the resin sheet material, preliminary shaping is performed, and after the resin sheet material is further heated, the resin sheet material is vacuum formed. In other words, by shaping in two stages, it becomes possible to form a small R shape by deep drawing.

Japanese Patent Publication No. 62-255119

However, with the technique described in Patent Document 1, it is difficult to perform highly accurate positioning in molding a resin sheet material. When the resin sheet material softens due to heating, drawdown is likely to occur due to the weight of the sheet itself, making highly accurate positioning difficult. Therefore, even when adopting a method of pre-shaping and then reheating and further shaping as shown in Patent Document 1, in order to achieve highly accurate positioning, it is necessary to Since it is necessary to sufficiently soften the resin sheet material when heating it, waving and drawdown of the resin sheet material cannot be avoided during heating. This may lead to problems such as misalignment or wrinkles depending on the condition of the resin sheet material of the molded product.

For this reason, the conventional method has been to heat the resin sheet material at a low temperature that does not cause drawdown of the resin sheet material, and then apply compressed air at an ultra-high pressure of, for example, 3 MPa or more to mold the resin sheet material. However, when a transparent resin sheet material is molded using low-temperature heating and ultra-high pressure, residual stress may occur inside the molded product, affecting the transparency of the material. Furthermore, since it is necessary to maintain ultra-high pressure air during molding, there are problems in that the molding apparatus itself tends to be expensive and molding takes time.

Therefore, it is an object of the present invention to provide a thermoforming apparatus in which positional displacement is unlikely to occur even when molding is performed under a relatively low pressure environment when thermoforming is performed using a resin sheet material.

In order to achieve the above object, a thermoforming apparatus according to one aspect of the present invention has the following features.

(1) In a thermoforming device that heats a sheet using a radiation heating means and uses a mold to mold the sheet or coat and bond the sheet to a base material,
The sheet is held between a first chamber located at the top and a second chamber located at the bottom,
comprising a pressure control means for controlling the internal pressure of the first chamber or the second chamber when molding the sheet;
The pressure control means includes:
A first pressure control valve connected to the first chamber is controlled to set the pressure in the first chamber to a first pressurized state and to a second pressurized state in which the internal pressure of the first chamber is higher than the first pressurized state. Ability to switch between pressurized state and
Alternatively, controlling a second pressure control valve connected to the second chamber to switch the pressure in the second chamber between a first vacuum state and a second vacuum state having a higher degree of vacuum than the first vacuum state. having a function;
It is characterized by

(2) In the thermoforming apparatus described in (1),
The pressure control means
As the first control stage,
After the sheet and the mold are brought close to each other and the sheet comes into contact with a convex portion of the mold, the pressure in the first chamber is controlled to be in the first pressurized state,
or controlling the pressure in the second chamber to be in the first vacuum state after the sheet and the mold are brought into close proximity and the sheet comes into contact with a convex part of the mold;
As the second control stage,
During the forming of the sheet, the pressure in the first chamber is controlled to be in the second pressurized state, or the pressure in the second chamber is controlled to be in the second vacuum state; enabling multi-stage pressure control;
is preferred.

(3) In a thermoforming device that heats a sheet using a radiation heating means and uses a mold to shape the sheet into a mold or coat and adhere the sheet to a base material,
The sheet is held between a first chamber located at the top and a second chamber located at the bottom,
comprising pressure control means for controlling the internal pressures of the first chamber and the second chamber when molding the sheet;
The pressure control means includes:
A function of controlling a second pressure control valve connected to the second chamber to switch the pressure in the second chamber between a first vacuum state and a second vacuum state having a higher degree of vacuum than the first vacuum state. ,
and controlling a second pressure control valve connected to the second chamber to switch the pressure in the second chamber between a first vacuum state and a second vacuum state having a higher degree of vacuum than the first vacuum state. Has a function,
As the first control stage,
After the sheet and the mold are brought close to each other and the sheet comes into contact with the convex part of the mold, the pressure in the second chamber is controlled to be in the first vacuum state, and the pressure in the second chamber is controlled to be in the first vacuum state. controlling the pressure to be in the first vacuum state,
As the second control stage,
In the middle of forming the sheet, the pressure in the second chamber is controlled to be in the second vacuum state, and the pressure in the second chamber is controlled to be in the second vacuum state. enabling pressure control;
It is characterized by

According to any of the aspects (1) to (3) above, by using a thermoforming device that performs multistage pressure control, highly accurate molding that is less likely to cause positional deviation even in a relatively low pressure environment. It becomes possible to realize this. In this, as a first control step, after the sheet and the mold are brought close to each other and the sheet contacts the convex part of the mold, the pressure in the first chamber is controlled to be in the first pressurized state, or The pressure in the second chamber is controlled to be in the first vacuum state, or both are controlled to be in the first pressurized state or the first vacuum state, and as a second control step, after a predetermined period of time has elapsed, , the pressure in the first chamber is controlled to be in the second pressurized state, or the pressure in the second chamber is controlled to be in the second vacuum state, or both are controlled to be in the second pressurized state, the second vacuum state. This is because by employing multi-stage pressure control that controls the pressure to be in a two-vacuum state, it becomes possible to apply pressure according to the sheet forming stage.

A sheet heated by a radiant heating device at a temperature that does not cause drawdown is brought into contact with a preheated mold, and then molded while being further heated. At this time, in the first control stage, the sheet held between the first chamber and the second chamber is maintained such that the pressure in the first chamber is maintained at the first pressurized state, or the pressure in the second chamber is maintained at the first pressurized state. The first vacuum state is maintained and molded while being heated, and after a predetermined period of time, the molding is further transferred to the second control stage or the second control stage in which the second vacuum state is achieved, and molding is continued at an even higher degree of vacuum. Alternatively, molding is performed by appropriately controlling both the first chamber internal pressure and the second chamber internal pressure. During molding, if you create a high vacuum all at once, the sheet may stretch more than necessary, but by performing multi-stage pressure control, you can increase the pressure according to the sheet molding situation, and as a result, The sheet can be easily formed into any shape.

(4) In the thermoforming apparatus according to any one of (1) to (3),
determining the timing of switching from the first control stage to the second control stage using elapsed time as a trigger;
is preferred.

(5) In the thermoforming apparatus according to any one of (1) to (3),
comprising temperature confirmation means for measuring the surface temperature of the sheet,
determining a switching timing from the first control stage to the second control stage using temperature data obtained from the temperature confirmation means as a trigger;
is preferred.

According to the aspect described in (4) or (5) above, molding can be started at an appropriate timing. As explained above, the purpose of molding with multi-stage pressure control is to air-form a sheet heated to an appropriate temperature at an appropriate pressure, or to perform vacuum forming to achieve even better results. It becomes possible to mold a molded product with a uniform thickness or a targeted thickness. The timing may be determined based on the passage of time or based on temperature data obtained by temperature confirmation means.

(6) In the thermoforming apparatus according to any one of (1) to (5),
The radiant heating means includes:
Multiple heaters are lined up,
a first area configured by the heater corresponding to a convex portion of the mold;
a second area configured by the heater that does not include the first area,
The radiant heating means includes:
comprising a heating control means that enables different output control in the first area and the second area,
By the heating control means,
As the first heating stage,
performing initial heating on the sheet by the radiant heating means;
As the second heating stage,
When the sheet and the mold are brought close to each other and the sheet comes into contact with the convex portion,
The first area performs low-temperature heating with reduced output,
The second area enables multi-stage heating control to perform high temperature heating with higher output than the first area,
starting the first control step during the second heating step;
is preferred.

According to the aspect described in (6) above, by using a thermoforming device that performs multistage heating control, it is possible to achieve highly accurate molding that is less likely to cause positional deviation even when molding is performed in a relatively low pressure environment. becomes possible. In the first heating stage, the sheet is initially heated to a temperature that does not cause drawdown, and after the sheet comes into contact with the convex part of the mold, the second heating stage is performed and the output is turned off to the first area. This is because we adopted a method that performs low-temperature heating and high-temperature heating with higher output in the second area.

When the sheet heated by the radiant heating device in the first heating stage comes into contact with the preheated mold, a temperature change occurs at the contact portion. This is because a temperature change occurs due to direct contact between the mold and the sheet. As a result, if uniform heating is continued, there will be areas where the temperature rises more than necessary and areas where the temperature is insufficient. To cope with this, by dividing the area and applying the necessary heating, it is possible to heat the parts you want to process more and suppress the heating in the parts you don't want to process, making it easier to form the sheet into any shape. .

Specifically, for example, by setting the first area as a place that requires positioning and that you do not want to stretch, after the first area contacts the convex part of the mold, low-temperature heating is performed so that the first area is at a low temperature. However, it is possible to perform molding in which the second area corresponding to the portion to be deformed is heated at a higher temperature with higher output. By performing multi-stage heating control in this manner and dividing the area to be heated, it becomes possible to deform the sheet by heating the portion to be deformed intensively. As a result, molding with higher shape accuracy is possible.

(7) In the thermoforming apparatus described in (6),
A portion of the sheet corresponding to the first area is a portion of the molded product that requires alignment;
is preferred.

According to the aspect described in (7) above, the part of the sheet corresponding to the first area comes into contact with the convex part of the mold first and is heated at a low temperature in the second heating stage, so that there is no deformation during molding. become less susceptible. Therefore, by making the parts of the molded product that require alignment, such as printed parts and parts used as transparent windows, as parts of the sheet that correspond to the first area, the effects of misalignment that occur during molding can be minimized. Is possible.

(8) In the thermoforming device according to (6) or (7),
The heating control means includes a temperature confirmation means for confirming the temperature of the sheet, and performs the multistage heating control using temperature data of the sheet obtained by measurement by the temperature confirmation means;
is preferred.

According to the aspect described in (8) above, the temperature of the sheet to be measured can be determined by the radiation thermometer, and more accurate control can be performed by the heating control means, so that molding with high shape accuracy can be performed. possible.

FIG. 1 is an explanatory diagram of a schematic configuration of a thermoforming apparatus according to the present embodiment. It is a top view of the heater used for the thermoforming apparatus of this embodiment. It is an explanatory view showing the third process of molding of this embodiment. It is an explanatory view showing the fourth process of molding of this embodiment. It is an explanatory view showing the 5th process of molding of this embodiment. The plan view of the heater in this embodiment corresponds to the third step. The plan view of the heater in this embodiment corresponds to the fourth step. It is a time chart showing the molding procedure of this embodiment. 1 is a schematic diagram of a system of a thermoforming apparatus according to the present embodiment.

First, an outline of the configuration of a thermoforming apparatus 100 according to an embodiment of the present invention will be explained. FIG. 1 is an explanatory diagram illustrating a schematic configuration of a thermoforming apparatus 100 according to the present embodiment. The thermoforming apparatus 100 includes a first chamber 101, a second chamber 102, a heating means 110, and a mold 200. This thermoforming apparatus 100 has a configuration in which a resin sheet S to be molded is held in a first chamber 101 and a second chamber 102, and molded while being heated by a heating means 110 disposed above.

A compressor and a vacuum pump, which will be described later, are connected to the first chamber 101 and the second chamber 102 of the thermoforming apparatus 100, respectively, and the pressure in the first chamber 101 and the second chamber 102 is reduced by operating the compressor or vacuum pump. Adjustments can be made. The first chamber 101 opens downward, the second chamber 102 opens upward, and by raising and lowering the first chamber 101 and the second chamber 102, the resin sheet S can be sandwiched. Holds the manufactured sheet S.

A compressor and a pressurizing tank (not shown) are connected to the first chamber 101, and by providing a first valve V1, which will be described later, in the middle of the first pipe P1, the inside of the first chamber 101 can be pressurized to an arbitrary pressure. can. A vacuum pump (not shown) is connected to the second chamber 102, and by providing a second valve V2, which will be described later, in the middle of the second pipe P2, the inside of the second chamber 102 can be reduced to an arbitrary pressure. The first chamber 101 and the second chamber 102 have a structure that can withstand the internal pressure generated when the resin sheet S is pressurized and depressurized during molding. The first valve V1 and the second valve V2 are pressure control valves that can detect internal pressure and arbitrarily control the pressure.

The resin sheet S is made of polycarbonate, a thermoplastic resin, and is a sheet material cut into a rectangular shape with a thickness of about 300 μm. These materials and thicknesses are merely examples, and the material and thickness of the resin sheet S are not limited to these, but the present invention aims to solve problems in processing relatively thin resin sheets. Therefore, it is assumed that the thickness of the resin sheet S to be processed is approximately 250 μm to 500 μm. Note that this does not preclude use in thick plate materials, and even if the present invention is applied to the molding of thick plate materials, it can be expected that effective effects will be produced.

FIG. 2 shows a plan view of the heater used in the thermoforming apparatus 100. The heating means 110 is a group of heaters 111 arranged above the resin sheet S to perform radiation heating used for heating the resin sheet S from the upper surface, and as shown in FIG. The heaters 111 are arranged in a tile pattern on the lower surface of the heater 120. In FIG. 2, for the sake of explanation, the cells are arranged in 4 rows and 8 columns, but this may be increased or decreased as necessary. By increasing the number of matrices, it becomes possible to handle more detailed shapes.

The heating means 110 is held by an upper elevating device 120, and the upper elevating device 120 has a configuration in which the heating means 110 can be moved to an arbitrary height within the first chamber 101 by a first driving device 121, which will be described later. ing. Further, each heater 111 is connected to a heating control means 250, which will be described later, so that the output can be arbitrarily adjusted.

Thermometers (S1, S2) are provided at the top of the upper lifting device 120 to measure the temperature at the surface of the resin sheet S through the gap provided in the upper lifting device 120 and the heating means 110. The first thermometer S1 and the second thermometer S2 are radiation thermometers that measure the temperature of the resin sheet S in a non-contact manner. Note that as many thermometers as necessary are installed for reasons described later.

The mold 200 is held by a lower lifting device 210 that can be raised and lowered to any height by a second driving device 211, which will be described later, and is used for molding the resin sheet S. The mold 200 has a protrusion 200a formed therein. The convex portion 200a corresponds to a part of a molded product M made from a resin sheet S, for example, a part where a pattern is printed and would be problematic if misalignment occurs, or a part where transparency is required and internal distortion would be problematic. It is said that For convenience, the portion of the mold 200 other than the convex portion 200a is defined as a low portion 200b for convenience.

The convex portion 200a of the mold 200 corresponds to the first area A1 of the heating means 110 shown in FIG. The first area A1 is the area surrounded by the two-dot chain line in FIG. 2 and includes the four heaters 111, and the other area is the second area A2. The mold 200 consists of a convex part 200a and a lower part 200b, and the second area A2 of the heating means 110 corresponds to the lower part 200b and the part around which the resin sheet S comes into contact. Note that it is not prohibited to increase the number of regions of the heating means 110 from two to more.

FIG. 9 shows a schematic diagram of the thermoforming device system. Although the drawing of the heating means 110 is omitted for convenience of explanation, each heater 111 is connected to a heating control means 250. Further, a first thermometer S1 and a second thermometer S2, which correspond to temperature confirmation means, are connected to the heating control means 250, and data from the thermometers (S1 and S2) is used to trigger control of the heater 111. . The first thermometer S1 is installed so as to aim at the part of the sheet corresponding to the first area A1, and the second thermometer S2 is installed so as to aim at the part of the sheet corresponding to the second area A2. Note that the number of thermometers may be increased as necessary. When the area of the heating means 110 is further increased in addition to the first area A1 and the second area A2, it is possible to increase the number of thermometers accordingly and use them as the heating control means 250.

A first drive device 121 that drives the upper lifting device 120 and a second driving device 211 that drives the lower lifting device 210 are connected to a drive control means 260. Although the first chamber 101 and the second chamber 102 are not shown in FIG. 9, the first valve V1 and the second valve V2 connected thereto are connected to the pressure control means 270. The heating control means 250, the drive control means 260, and the pressure control means 270 are provided on the control panel 300.

Next, the procedure for molding the resin sheet S will be explained. The state of the molding is shown in FIGS. 1, 3 to 5, and the molding is performed in the order of FIGS. 1, 3, 4, and 5. FIG. 8 shows an image of a time chart for controlling each function during molding. The horizontal axis shows the elapsed time from t1 to t6 and separates the steps. Below, the operation of each device will be explained based on FIG. 8, divided into the first process Pr1 to the sixth process Pr6.

First, in the first step Pr1, the first chamber 101 and the second chamber 102 are closed so that the inserted resin sheet S is sandwiched between the first chamber 101 and the second chamber 102, as shown in FIG.

Next, in the second step Pr2, the heating means 110 is held at the position where the upper lifting device 120 is lowered, and the resin sheet S is heated from above (the state shown in FIG. 1). The heating means 110 performs initial heating using a heater 111. The heating at this time is such that the resin sheet S is slightly softened, and the heating is continued until it is confirmed that the set temperature is reached by the first thermometer S1 and the second thermometer S2. In this embodiment, the resin sheet S is made of polycarbonate, and its softening temperature is about 150 degrees, so at this point, in the first heating stage, it is heated to a temperature of about 140 degrees, at which the polycarbonate begins to undergo thermal deformation. At this time, since it is desired to quickly complete heating of the resin sheet S, the ignition rate (output) of the heater 111 is set to 100%.

Next, in the third step Pr3, as shown in FIG. is raised and brought into contact with the resin sheet S (denoted as a table in FIG. 8). At this time, the convex part 200a of the mold 200 comes into contact with the resin sheet S before the other part (low part 200b) of the mold 200. In this way, the resin sheet S is deformed by being brought into contact with the resin sheet S while being heated by the heating means 110. Here, since the mold 200 is heated to a lower temperature (approximately 120 degrees), the convex portion 200a comes into contact with the resin sheet S, thereby partially lowering the temperature.

At this time, the heating control means 250 changes the first heating stage from the first heating stage in which all the heaters 111 perform heating with the same output as shown in FIG. 6 to the first heating stage in the second heating stage as shown in FIG. The temperature setting is changed between A1 and the second area A2 to switch to a heating state. Here, the first area A1 shown in FIG. 7 is a position corresponding to the convex part 200a of the mold 200 of the heating means 110, and the second area A2 is a position other than that. The heater 111 corresponding to the first area A1 continues to have an ignition rate of 10% in the third step Pr3, and other areas including the second area A2 (arranged at positions surrounding the heater 111 corresponding to the first area A1) The ignition rate of the heater 111 is 50%. Therefore, the portion of the resin sheet S that is brought into contact with the lower portion 200b is actively heated.

Next, in the fourth step Pr4, using the fact that the surface temperature of the resin sheet S reaches 170 degrees as a trigger (detected by the second thermometer S2), the first chamber 101 is pressurized and the second chamber 102 is Begin to reduce the pressure and start molding. In the fourth step Pr4, the first chamber 101 is pressurized for a predetermined period of time from elapsed time t3 to elapsed time t4 by reducing the amount of compressed air supplied by the first valve V1 (indicated as "upper low pressure air" in FIG. 8). ), the pressure in the second chamber 102 is reduced by restricting the amount of air exhausted by the second valve V2 (denoted as "lower vacuum" in FIG. 8), and molding is performed at a low pressure. The opening degrees of the first valve V1 and the second valve V2 are controlled by the pressure control means 270. Specifically, the pressure in the first chamber 101 is controlled to be 0.1 MPa, and the pressure in the second chamber 102 is controlled to be -0.05 MPa.

Next, in the fifth step Pr5, as shown in FIG. In other words, the first valve V1 and the second valve V2 are opened to perform molding at a higher pressure than in the previous step. Here, as shown in FIG. 8, the opening timing of the first valve V1 is controlled to be delayed from the opening timing of the second valve V2. Specifically, the pressure in the first chamber 101 is controlled to be 0.7 MPa, and the pressure in the second chamber 102 is controlled to be -0.1 MPa.

Finally, in the sixth step Pr6, the internal pressures of the first chamber 101 and the second chamber 102 are returned to atmospheric pressure. Thereafter, the first chamber 101 and the second chamber 102 are opened, and the molded product M obtained by thermoforming the resin sheet S is taken out.

Since the thermoforming apparatus 100 of this embodiment has the above-mentioned configuration, it has the following functions and effects.

First, it becomes possible to thermoform the molded product M with higher precision, which is less likely to cause misalignment. In a thermoforming apparatus 100 that heats a resin sheet S using a radiation heating device (heating means 110) and shapes the resin sheet S using a mold 200, the resin sheet S is It is held so as to be sandwiched between a first chamber 101 disposed at the top and a second chamber 102 disposed at the bottom, and when molding the resin sheet S, the interior of the first chamber 101 or the second chamber 102 is A pressure control means 270 is provided to control the pressure.

The pressure control means 270 then controls a first pressure control valve (first valve V1) connected to the first chamber 101 and a second pressure control valve (second valve V2) connected to the second chamber 102. It has a function of controlling and arbitrarily switching the pressure in the second chamber 102 between a first vacuum state and a second vacuum state having a higher degree of vacuum than the first vacuum state.

As a first control step, after the resin sheets S are brought close to each other and the resin sheets S come into contact with the convex portions 200a of the resin sheets S, the pressure in the first chamber 101 is increased to a first pressure. or the pressure in the second chamber 102 is controlled to be in the first vacuum state, and as a second control step, during the thermoforming of the resin sheet S, the pressure in the first chamber 101 is controlled to be in the first vacuum state. This enables multi-stage pressure control in which the pressure in the second chamber 102 is controlled to be in the second pressurized state, or the pressure in the second chamber 102 is controlled to be in the second vacuum state. This prevents positional displacement of the resin sheet S during thermoforming.

In other words, as shown in FIG. 8, molding is performed with the chamber internal pressure controlled in multiple stages. The "vacuum pressure" graph shown at the bottom shows that molding is performed at a low pressure (-0.05 MPa) in the second chamber 102 from elapsed time t3 to elapsed time t4. At this time, as described above, the "upper low pressure air" control is turned on in the first chamber 101, and the compressed air from the first pipe P1 is supplied to the first chamber 101 by the pressure control means 270 so that the internal pressure becomes 0.1 MPa. 1 valve V1 is used to reduce the supply, the "lower vacuum" control is turned on to the second chamber 102, and the pressure control means 270 exhausts air from the second pipe P2 so that the internal pressure is -0.05 MPa. This is done while throttling with the second valve V2. This is the first control stage.

Next, from the elapsed time t4 to the elapsed time t5, the second control performs thermoforming at a higher pressure (controlled to be 0.7 MPa in the first chamber 101 and -0.1 MPa in the second chamber 102). Move to the stage. By applying pressure in multiple stages in this way, precise molding becomes possible. If high-pressure air is applied all of a sudden, the resin sheet S will easily become thinner than necessary or break, so by applying pressure in multiple stages, it is possible to mold the molded product M with a uniform thickness. There is.

Regarding the timing of switching from the first control stage to the second control stage, as shown in FIG. May be used. Switching from the first control stage to the second control stage should be determined based on the degree of progress of molding the resin sheet S, and the trigger should be based on either the passage of time or temperature data. . The purpose of switching to the second control stage is to increase the degree of adhesion of the resin sheet S to the mold 200, and when the resin sheet S takes the shape of the mold 200 as shown in FIG. By further increasing the degree of vacuum (reaching the second vacuum state), it becomes easier to transfer the shape of the mold 200 onto the resin sheet S.

In addition, drawdown of the resin sheet S is prevented by bringing the mold 200 into contact with the resin sheet S at the stage where the resin sheet S is quickly heated to a temperature that does not cause drawdown in the first heating stage. I can do things. Furthermore, by dividing the area to be heated and providing the heating means 110 with a first area A1 that is heated at a low temperature and a second area A2 that is heated at a higher temperature than the first area A1, the area made of resin that needs to be deformed is provided. By applying the necessary heat to the second area A2 of the sheet S, it becomes possible to deform the sheet S. Therefore, by performing multi-stage heating while controlling the heater 111 with the heating control means 250, it is possible to prevent drawdown of the resin sheet S and improve the molding accuracy of the molded product M.

At this time, the part of the resin sheet S corresponding to the first area A1 is printed on the part that requires alignment, for example, the surface of the resin sheet S, and if any misalignment occurs, it will be reshaped as a molded product M. In some cases, the performance of the product may be affected, or if the transparency is affected by distortion that occurs during molding, misalignment may occur, or internal distortion may make it difficult to see through the transparent part. This can be prevented. The portion of the resin sheet S corresponding to the first area A1 is the portion that first comes into contact with the convex portion 200a of the mold 200 during molding. Since the output of the first area A1 is further reduced than that of the second area A2 in the second heating stage, the resin sheet S may be overheated and deformed more than necessary, and may become wrinkled or torn as the case may be. It is possible to prevent this and mold the resin sheet S into a desired shape.

In this way, by combining multi-stage heating and multi-stage pressure to thermoform the resin sheet S while controlling the chamber internal pressure, drawdown of the resin sheet S during heating can be prevented, and the mold 200 can be lowered during molding. It becomes possible to firmly press the resin sheet S against the molding material and realize molding with high shape accuracy. Furthermore, since it is no longer necessary to form the resin sheet S using low-temperature heating and ultra-high pressure as in the past, equipment manufacturing can be simplified and costs can be expected to be reduced.

Although the thermoforming apparatus 100 according to the present invention has been described above, the present invention is not limited thereto, and various changes can be made without departing from the spirit thereof. For example, the illustrated materials and temperatures may be changed as appropriate. Moreover, if it is desired to further create a temperature gradient, by bringing the heating means 110 closer to the resin sheet S in the second heating stage, the temperature gradient on the resin sheet S can be created more clearly. Moving the heater 111 in the second heating stage is effective in forming a complex shape with many irregularities. Conversely, if the heating means 110 is moved away from the resin sheet S, the temperature gradient can be made gentler.

Further, as multi-stage heating, it is explained that the ignition rate of the heater 111 is set to 100% for the initial heating of the resin sheet S in the first heating stage, but if necessary, the heating means 110 is It does not prevent heating by dividing the area into areas different from A1 and the second area A2, or changing the ignition rate according to the area classification into the first area A1 and the second area A2. For example, it may be possible to heat the resin sheet S uniformly by setting the ignition rate in the central portion of the resin sheet S to be lower than that in the periphery. What is required in the first heating stage is smooth heating of the resin sheet S and a device that does not cause problems such as drawdown. The purpose is different from wanting to keep the temperature as low as possible. In the present invention, highly accurate molding of the resin sheet S is achieved by performing multi-stage heating in which different heating conditions are set for the first heating stage and the second heating stage.

Furthermore, although this embodiment shows an example of mold shaping using the mold 200, the present invention cannot be applied to thermoforming in which a resin sheet S is coated and adhered to a base material. It's not a thing. Even when the present invention is used for mold shaping, the adhesion of the resin sheet S to the base material can be improved, and more accurate molding can be achieved. Further, in this embodiment, data obtained from the first thermometer S1 and the second thermometer S2 is used to trigger the first heating stage and the second heating stage. However, apart from using temperature data as a trigger, it is conceivable to use time as a trigger or to use the degree of vacuum as a trigger, so it is possible to change it as appropriate.

Further, in this embodiment, the internal pressures of the first chamber 101 and the second chamber 102 of the thermoforming apparatus 100 are illustrated, and the timing thereof is explained with reference to FIG. However, since the gist of the invention is to perform multi-stage control in which the pressure is set to a low pressure in the first control stage and the pressure is set to a higher pressure in the second control stage, the numerical value may be increased or decreased as appropriate depending on the thickness and temperature of the resin sheet S. do not prevent you from doing so.

S Resin sheet A1 First area A2 Second area 100 Thermoforming device 110 Heating means 111 Heater 250 Heating control means 200 Mold 200a Convex portion

Claims (4)

In a thermoforming device that heats a sheet using a radiation heating means and uses a mold to shape the sheet into a mold or coat and adhere the sheet to a base material,
The sheet is held between a first chamber located at the top and a second chamber located at the bottom,
comprising a pressure control means for controlling the internal pressure of the first chamber or the second chamber when molding the sheet;
The pressure control means includes:
A first pressure control valve connected to the first chamber is controlled to set the pressure in the first chamber to a first pressurized state and to a second pressurized state in which the internal pressure of the first chamber is higher than the first pressurized state. Ability to switch between pressurized state and
Alternatively, controlling a second pressure control valve connected to the second chamber to switch the pressure in the second chamber between a first vacuum state and a second vacuum state having a higher degree of vacuum than the first vacuum state. Has a function,
The pressure control means
As the first control stage,
After the sheet and the mold are brought close to each other and the sheet comes into contact with a convex part of the mold, the pressure in the first chamber is controlled to be in the first pressurized state, or the pressure in the first chamber is controlled to be in the first pressurized state, or controlling the pressure in the chamber to the first vacuum state;
As the second control stage,
During the forming of the sheet, the pressure in the first chamber is controlled to be in the second pressurized state, or the pressure in the second chamber is controlled to be in the second vacuum state; enabling multi-stage pressure control;
A thermoforming device featuring: The thermoforming device according to claim 1 ,
determining the timing of switching from the first control stage to the second control stage using elapsed time as a trigger;
A thermoforming device featuring: The thermoforming device according to claim 1 ,
comprising temperature confirmation means for measuring the surface temperature of the sheet,
determining a switching timing from the first control stage to the second control stage using temperature data obtained from the temperature confirmation means as a trigger;
A thermoforming device featuring: The thermoforming device according to claim 1 ,
The radiant heating means includes:
Multiple heaters are lined up,
a first area configured by the heater corresponding to a convex portion of the mold;
a second area configured by the heater that does not include the first area,
The radiant heating means includes:
comprising a heating control means that enables different output control in the first area and the second area,
By the heating control means,
As the first heating stage,
performing initial heating on the sheet by the radiant heating means;
As the second heating stage,
When the sheet and the mold are brought close to each other and the sheet comes into contact with the convex portion,
The first area performs low-temperature heating with reduced output,
The second area enables multi-stage heating control to perform high temperature heating with higher output than the first area,
starting the first control step during the second heating step;
A thermoforming device featuring:

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