Method for manufacturing molded body and casting apparatus

Abstract

To provide a method for manufacturing a molded body capable of sufficiently suppressing the generation of a weld line in the molded body, and a cast molding apparatus for the molded body.SOLUTION: The present invention provides a method for producing a formed body by slurry pressure forming, the method including a pouring step of pouring slurry from one or a plurality of pouring ports (2b) provided in a casting mold (2), and a depositing step of, after the casting mold (2) is filled with the slurry, pushing the slurry from the pouring port (2c) at a predetermined pressure in a state where a slurry discharge port (2b) provided in the casting mold (2) is closed, A circulating process for discharging the slip from at least one slip discharge port (2b) while pouring the slip from at least one pouring port (2c) is executed before a thickening process.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a green body, and more particularly to a method for producing a green body by slip pressure molding, and a slip casting apparatus. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2005-153495 (Patent Document 1) describes a method for casting ceramic bodies by slip casting. In this casting method, a ceramic body is formed using a plaster mold and a slurry in which ceramic raw material powder is dispersed in water. The plaster mold has an inlet for injecting the slurry into a cavity, an exhaust hole for discharging air from the cavity, and two paths branching from the inlet and joining near the exhaust hole. The slurry is not vibrated when it branches from the inlet, but is vibrated by the time the slurry joins near the exhaust hole. The invention described in Patent Document 1 aims to prevent the formation of linear weld lines in the cast body by vibrating the slurry. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-153495 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as in the invention of Patent Document 1, simply applying vibration to the slip while the slip is being poured into the casting mold is not enough to sufficiently suppress the occurrence of weld lines in the green body, and there is still a problem in that weld lines will occur.

[0005] Therefore, an object of the present invention is to provide a method for producing a molded body and a slip casting apparatus for a molded body that can sufficiently suppress the occurrence of weld lines in the molded body. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the present invention provides a method for producing a green body by slip pressure molding, which comprises: a pouring step in which a slip is poured into a casting mold through one or more pouring ports; and a casting step in which, after the mold has been filled with the slip, the slip is forced through the pouring ports at a predetermined pressure while the mold's drain ports are closed.The method is characterized in that a circulation step is carried out before the casting step in which the slip is poured into at least one pouring port while simultaneously being discharged from at least one drain port.

[0007] According to the present invention configured as described above, a circulation step is carried out before the casting step, in which the slip is poured through the pouring port while being simultaneously discharged from the discharge port, so that most of the portions of the slip that are likely to form weld lines due to collisions between the slips poured into the casting mold from the pouring port can be discharged through the discharge port. As a result, portions of the slips that have collided with each other in the casting mold are less likely to remain in the casting mold, effectively suppressing the formation of weld lines in the molded product.

[0008] In the present invention, preferably, at the final stage of the circulation step, the total volume of the slip introduced from the inlet per unit time is made substantially equal to the total volume of the slip discharged from the outlet per unit time.

[0009] According to the present invention configured as described above, at the end of the circulation step, the total volume of the slip poured into the casting mold from the pouring port per unit time is made substantially equal to the total volume of the slip discharged from the discharge port per unit time. Therefore, by the end of the circulation step at the latest, the air trapped in the casting mold is completely discharged from the casting mold, and the occurrence of weld lines in the molded product can be sufficiently suppressed.

[0010] In the present invention, the circulation step is preferably carried out continuously for a predetermined period of time.

[0011] According to the present invention configured as described above, the circulation process is carried out continuously for a predetermined period of time, so that the weld line portion of the slip that occurs in the casting mold during the pouring process can be sufficiently discharged from the drain port, and the occurrence of weld lines in the molded body can be sufficiently suppressed.

[0012] The present invention also provides a slip casting apparatus for producing a green body by slip pressure molding, comprising: a casting mold having at least one pouring port and at least one sludge discharge port; a pressurizing device for pressurizing the slip so that the slip flows into the casting mold through the pouring port; a sludge discharge valve for closing or opening the sludge discharge port; and a control unit for controlling the pressurizing device and the sludge discharge valve, wherein the control unit performs a circulation step in which, after the casting mold has been filled with slip, the pressurizing device is operated with the sludge discharge port closed, before the casting step in which the pressurizing device is operated with the sludge discharge port closed.

[0013] According to the present invention configured as described above, the control unit controls the pressurizing device and the sludge discharge valve to execute a circulation step in which the pressurizing device is operated with the sludge discharge port open before the casting step, so that most of the portions of the mold where the sludge particles collide with each other and are prone to weld lines can be discharged through the sludge discharge port. As a result, portions of the mold where the sludge particles collide with each other are less likely to remain in the mold, effectively suppressing the occurrence of weld lines in the molded product.

[0014] In the present invention, the casting mold preferably further comprises an exhaust port for discharging air trapped in the casting mold, and the distance between the sludge discharge port, which is open during the circulation step, and the pouring port through which the slip is poured into the casting mold is shorter than the distance between the sludge discharge port and the exhaust port and the distance between the pouring port and the exhaust port.

[0015] According to the present invention configured as described above, the distance between the drain port, which is open during the circulation process, and the pouring port through which the slip is poured into the casting mold is shorter than the distance between the drain port and the exhaust port and the distance between the pouring port and the exhaust port, so that during the circulation process, the slip flows sufficiently through the casting mold before being discharged from the drain port. This ensures that any weld lines that occur in the casting mold are reliably discharged from the drain port, and the occurrence of weld lines in the molded product is sufficiently suppressed.

[0016] In the present invention, preferably, the total cross-sectional area of ​​the inlet ports is approximately the same as the total cross-sectional area of ​​the sludge discharge ports.

[0017] According to the present invention configured in this manner, the total cross-sectional area of ​​the pouring ports is approximately the same as the total cross-sectional area of ​​the sludge discharge ports. This makes it possible to set the flow rate of the slip poured through the pouring ports and the flow rate of the slip discharged through the sludge discharge ports to be approximately the same during the circulation process. This enables the slip to be circulated smoothly during the circulation process, and effectively suppresses the occurrence of weld lines in the molded body. [Effects of the Invention]

[0018] According to the method for producing a molded body and the apparatus for casting a molded body of the present invention, the occurrence of weld lines in the molded body can be sufficiently suppressed. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram showing the overall configuration of a slip casting apparatus according to a first embodiment of the present invention. [Figure 2] 1 is a side view of a casting mold provided in a casting molding apparatus according to a first embodiment of the present invention. [Figure 3] 1 is a perspective cross-sectional view of a casting mold provided in a casting molding apparatus according to a first embodiment of the present invention. [Figure 4] 1 is a flowchart showing the steps of a method for producing a molded body according to a first embodiment of the present invention. [Figure 5]1A to 1C are diagrams schematically illustrating a method for producing a molded body according to a first embodiment of the present invention. [Figure 6] 1A to 1C are diagrams schematically illustrating a method for producing a molded body according to a first embodiment of the present invention. [Figure 7] FIG. 10 is a perspective view of a casting mold provided in a casting molding apparatus for a molded body according to a second embodiment of the present invention. [Figure 8] 10 is a perspective cross-sectional view of a casting mold provided in a casting molding apparatus for a molded body according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Next, a method for manufacturing a molded body and a slip casting apparatus for a molded body according to an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a diagram showing the overall configuration of a slip casting apparatus according to a first embodiment of the present invention, Fig. 2 is a side view of a casting mold provided in the slip casting apparatus according to the first embodiment of the present invention, and Fig. 3 is a perspective sectional view of the casting mold provided in the slip casting apparatus according to the first embodiment of the present invention.

[0021] 1, the slip casting apparatus 1 of this embodiment comprises a casting mold 2 for slip pressure molding of a green body, a pressurizing device 4 for pressurizing the slip and causing it to flow into the casting mold 2, and a sludge discharge valve 6 for closing or opening a sludge discharge port provided in the casting mold 2. The casting apparatus 1 also comprises an exhaust valve 8 for opening and closing an exhaust port for discharging air from the casting mold 2, and a control unit 10 for controlling the pressurizing device 4, the sludge discharge valve 6, and the exhaust valve 8.

[0022] In this embodiment, the casting mold 2 is a resin mold made of resin, and is configured to form a green body by pouring a slip into a cavity 2a provided therein. The casting mold 2 is also provided with a pouring port 2b, a sludge discharge port 2c, and an exhaust port 2d, which communicate with the internal cavity 2a. In this embodiment, the cross-sectional area of ​​the pouring port 2b and the sludge discharge port 2c are approximately the same. In this embodiment, the pouring port 2b and the sludge discharge port 2c are provided on the bottom surface of the casting mold 2, and the exhaust port 2d is provided on the top surface of the casting mold 2. In addition, a pouring valve 12 is provided between the pressurizing device 4 and the casting port 2b, a sludge discharge valve 6 is provided at the sludge discharge port 2c, and an exhaust valve 8 is provided at the exhaust port 2d.

[0023] The pressurizing device 4 is configured to pressurize the slip and cause it to flow through the pouring port 2b of the casting mold 2. When the slip is allowed to flow through the pouring port 2b, a pouring valve 12 provided at the pouring port 2b is opened. The opening and closing of the pouring valve 12 is controlled by a control signal from the control unit 10. By causing the pressurizing device 4 to cause the slip to flow through the pouring port 2b, the cavity 2a of the casting mold 2 is filled with the slip. Furthermore, with the mold 2 filled with the slip, pressure can be applied to the slip by the pressurizing device 4.

[0024] The sludge discharge valve 6 is provided at the sludge discharge port 2c of the casting mold 2 and is configured to close or open the sludge discharge port 2c. The opening and closing of the sludge discharge valve 6 is controlled by a control signal from the control unit 10, and the sludge discharge valve 6 is configured to be opened at a predetermined timing to discharge the slip from the casting mold 2.

[0025] The exhaust valve 8 is provided at the exhaust port 2d of the casting mold 2 and is configured to open and close the exhaust port 2d. The exhaust port 2d is provided to exhaust air that has been trapped inside the casting mold 2 before the start of pouring slip into the casting mold 2. The opening and closing of the exhaust valve 8 is controlled by a control signal from the control unit 10, and the exhaust valve 8 is opened at a predetermined timing to exhaust air from inside the casting mold 2.

[0026] The control unit 10 is configured to control the pressurizing device 4, the sludge discharge valve 6, the exhaust valve 8, and the pouring valve 12 to execute the pouring process, the circulation process, and the inlaying process in the method for producing a molded body according to an embodiment of the present invention. Specific control of each process will be described later. The control unit 10 is specifically configured by a microprocessor, memory, an interface circuit, software for operating these components, and the like (all not shown).

[0027] Next, the operation of the molded body slip casting apparatus according to the first embodiment of the present invention and the molded body manufacturing method will be described with reference to FIGS. Fig. 4 is a flow chart showing the steps of the method for producing a molded body of this embodiment. Fig. 5 and Fig. 6 are diagrams schematically showing the method for producing a molded body of this embodiment.

[0028] First, in step S1 of the flowchart shown in Figure 4, the control unit 10 sends control signals to the sludge discharge valve 6, the exhaust valve 8, and the inflow valve 12, respectively, to close the sludge discharge valve 6 and open the exhaust valve 8 and the inflow valve 12 (see column I in Figure 5).

[0029] Next, in step S2, the control unit 10 sends a control signal to the pressurizing device 4 to activate it, thereby starting the slip pouring process. This causes the slip to flow through the pouring opening 2b of the casting mold 2, and begins filling the cavity 2a of the casting mold 2. When the slip flows into the cavity 2a of the casting mold 2, it hits the inner wall surface of the cavity 2a and spreads out from the pouring opening 2b to the surrounding area, as shown in column II of Figure 5.

[0030] As the pouring continues, the slip splits into two from the pouring port 2b and spreads through the cavity 2a, as shown in column III of Figure 5. As a result, the air that had been trapped in the cavity 2a of the casting mold 2 is pushed out by the inflow of the slip and is discharged from the exhaust port 2d.

[0031] 4, after the pouring process is started, it is determined whether a predetermined pouring time has elapsed. If the predetermined pouring time has not elapsed, the process of step S3 is repeated. Once the pouring time has elapsed, the process of the flowchart proceeds to step S4. In this embodiment, the predetermined pouring time is set to approximately 280 seconds.

[0032] After a predetermined pouring time has elapsed since the start of the pouring step, the two streams of slip that had been spreading through the cavity 2a inside the casting mold 2 have collided with each other, filling the gaps within the cavity 2a, as shown in column IV of Figure 5. In the example shown in Figure 5, the slip poured through the pouring opening 2b flows in two streams through the annular cavity 2a and collides near point P on the opposite side of the pouring opening 2b. Note that although the collision occurs at point P in the schematic illustration of Figure 5, in an actual casting mold that is constructed three-dimensionally, the collision of the two slips occurs in a generally linear region.

[0033] In the conventional method for manufacturing a green body, the marks left by the collision of the slip inside the casting mold 2 remain as weld lines in the green body. These weld lines remaining in the green body can cause breaks, cracks, and bulges in the ceramic after firing the green body, resulting in defective products and reduced quality.

[0034] Next, in step S4 of Fig. 4, the control unit 10 sends control signals to the sludge discharge valve 6 and the exhaust valve 8, respectively, to open the sludge discharge valve 6 and close the exhaust valve 8 (see line V of Fig. 5). Furthermore, the control unit 10 continues to operate the pressurizing device 4, and continues to inject the slip from the pouring port 2b. As a result, as shown in line VI of Fig. 5, the slip in the cavity 2a of the casting mold 2 is discharged from the sludge discharge port 2c. That is, the control unit 10 executes a circulation step in which the slip is poured from the pouring port 2b while simultaneously being discharged from the sludge discharge port 2c.

[0035] The slip in the casting mold 2 can be discharged from the drain port 2c due to gravity or the like, even without the pressure device 4 injecting the slip. However, at least at the end of the circulation step, the pressure device 4 injects the slip so that the volume of the slip poured into the pouring port 2b per unit time is approximately the same as the volume of the slip discharged from the drain port 2c per unit time. This allows the slip to circulate within the casting mold 2, filling the cavity 2a of the casting mold 2 with the slip without any gaps. Furthermore, due to this circulation step, the point P at which the slip collides inside the casting mold 2 is pushed by the injected slip and moves within the cavity 2a of the casting mold 2 toward the drain port 2c.

[0036] Furthermore, in step S5 of Fig. 4, after the circulation process is started, it is determined whether a predetermined circulation time has elapsed. If the predetermined circulation time has not elapsed, the process of step S5 is repeatedly executed. That is, the circulation process is executed continuously for the predetermined time. Then, when the circulation time has elapsed, the process in the flowchart proceeds to step S6.

[0037] Furthermore, after a predetermined circulation time has elapsed since the start of the circulation step, the collision point P of the slip that had been moving through the casting mold 2 toward the sludge discharge port 2c has been discharged to the outside through the sludge discharge port 2c, as shown in column VII of FIG. 6. In this embodiment, the predetermined circulation time is set to be approximately the same as the pouring time. This circulation time is set so that the slip injected in the pouring step can be sufficiently replaced in the circulation step and the collision point P that has occurred can be effectively discharged. Furthermore, after the predetermined circulation time has elapsed, in region A between the pouring port 2b and the sludge discharge port 2c in the casting mold 2, the slip that has flowed from the pouring port 2b to the right in FIG. 6 and the slip that has flowed over the sludge discharge port 2c and toward the left from the sludge discharge port 2c are sufficiently mixed, resulting in a state free of weld lines.

[0038] In this embodiment, the circulation process is performed until a predetermined circulation time has elapsed after the pouring process. Alternatively, as a modification, the amount of slip poured into the circulating process through the pouring port or the amount of slip discharged from the discharge port during the circulating process can be detected, and the period during which the circulation process is performed can be controlled based on this amount of slip.

[0039] In this embodiment, the distance between the sludge discharge port 2c and the pouring port 2b through which the slip is poured into the casting mold 2 is shorter than the distance between the sludge discharge port 2c and the exhaust port 2d and the distance between the pouring port 2b and the exhaust port 2d. Therefore, the point P at which the slip collides inside the casting mold 2 travels a relatively long distance within the casting mold 2 before being discharged outside through the sludge discharge port 2c. As a result, the collision point P that occurs inside the casting mold 2 can be effectively discharged.

[0040] Next, in step S6, the control unit 10 sends a control signal to the sludge discharge valve 6 to close it (see column IIX in FIG. 6). The control unit 10 also applies pressure to the slip filled in the casting mold 2 by continuing to operate the pressurizing device 4. That is, after the slip has been filled in the casting mold 2, the control unit 10 starts the casting step of forcing the slip through the pouring opening 2b of the casting mold 2 at a predetermined pressure while keeping the sludge discharge opening 2c of the casting mold 2 closed.

[0041] 4, after the casting process is started, it is determined whether a predetermined casting time has elapsed. If the predetermined casting time has not elapsed, the process of step S7 is repeated. Once the predetermined casting time has elapsed, the process proceeds to step S8 in the flowchart. Once the predetermined casting time has elapsed, the slip in the casting mold 2 is cast onto the wall surface of the cavity 2a of the casting mold 2, and a green body is formed in the casting mold 2.

[0042] Next, in step S8, the control unit 10 sends a control signal to the pressurizing device 4 to stop the operation of the pressurizing device 4. The control unit 10 also sends a control signal to the sludge discharge valve 6 to open the sludge discharge valve 6 (see column IX in FIG. 6). This executes the sludge discharge step, and the uncast slip in the casting mold 2 is discharged from the sludge discharge port 2c. Note that the present invention can also be configured such that the pouring valve 12 provided at the pouring port 2b of the casting mold 2 is a three-way valve, and after the pressurizing device 4 is stopped, the three-way valve can be switched to allow sludge to be discharged from the pouring port 2b as well.

[0043] Furthermore, in step S9, the green body in the casting mold 2 is demolded, completing the green body 14 (see column X in FIG. 6). In this embodiment, the casting mold 2 is composed of two halves, which can be separated to remove the green body from the casting mold 2. The completed green body then undergoes drying, glazing, firing, and other processes to become a ceramic product. In the green body produced by the green body production method of this embodiment, weld lines that occur due to the collision of the slip inside the casting mold 2 are removed in the circulation process. This effectively prevents chips, cracks, and bulges from occurring in the ceramic product after firing the green body.

[0044] According to the method for producing a green body of the first embodiment of the present invention, a circulation step (steps S4 and S5 in FIG. 4) is carried out before the casting step, in which slip is poured through the pouring port 2b while simultaneously being discharged from the drainage port 2c, so that the slips poured into the casting mold 2 from the pouring port 2b collide with each other, and most of the portions (collision points P) where weld lines are likely to occur can be discharged from the drainage port 2c. As a result, portions of the casting mold 2 where the slips collide with each other are less likely to remain in the casting mold 2, effectively suppressing the occurrence of weld lines in the green body.

[0045] Furthermore, according to the method for producing a green body of this embodiment, at the end of the circulation step, the total volume of the slip poured in through the pouring port 2b per unit time is made substantially equal to the total volume of the slip discharged through the drainage port 2c per unit time. Therefore, at the latest by the end of the circulation step, the air that has been retained in the casting mold 2 is completely discharged from the casting mold, and the occurrence of weld lines in the green body can be sufficiently suppressed.

[0046] Furthermore, according to the method for manufacturing a molded body of this embodiment, the circulation process is carried out continuously for a predetermined time (step S5 in Figure 4), so that the weld line portion of the slip (impact point P) that occurs in the casting mold 2 during the pouring process can be sufficiently discharged from the sludge discharge port 2c, and the occurrence of weld lines in the molded body can be sufficiently suppressed.

[0047] Furthermore, with the slip casting apparatus 1 of this embodiment, the control unit 10 controls the pressurizing device 4 and the sludge discharge valve 6 to execute a circulation step (steps S4 and S5 in FIG. 4) in which the pressurizing device 4 is operated with the sludge discharge port 2c open before the inlay step (steps S6 and S7 in FIG. 4), so that most of the portions (collision points P) where the sludge particles poured into the casting mold from the pouring port 2b collide with each other and are prone to weld lines can be discharged from the sludge discharge port 2c. As a result, portions of the casting mold 2 where the sludge particles collide are less likely to remain in the casting mold 2, effectively suppressing the occurrence of weld lines in the molded product.

[0048] Furthermore, according to the slip casting apparatus 1 of this embodiment, the distance between the sludge discharge port 2c, which is open during the circulation process, and the pouring port 2b through which the slip is poured into the casting mold 2 is shorter than the distance between the sludge discharge port 2c and the exhaust port 2d and the distance between the pouring port 2b and the exhaust port 2d, so that during the circulation process, the slip flows sufficiently through the casting mold 2 before being discharged from the sludge discharge port 2c. This ensures that any weld lines that occur in the casting mold 2 are reliably discharged from the sludge discharge port 2c, and the occurrence of weld lines in the molded product is sufficiently suppressed.

[0049] Furthermore, in the slip casting apparatus 1 of this embodiment, the cross-sectional area of ​​the pouring port 2b is approximately the same as the cross-sectional area of ​​the sludge discharge port 2c. This makes it possible to set the flow rate of the slip poured through the pouring port 2b and the flow rate of the slip discharged through the sludge discharge port 2c in the circulation step to approximately the same. This allows the slip to circulate smoothly in the circulation step, and effectively prevents weld lines from occurring in the molded body.

[0050] Next, a method for producing a green body and a slip casting apparatus for a green body according to a second embodiment of the present invention will be described with reference to FIGS. The method for manufacturing a green body and the apparatus for casting a green body of this embodiment use a different casting mold from those of the first embodiment. Therefore, only the differences between the first embodiment and the second embodiment of the present invention will be described below, and a description of the same configurations, actions, and effects will be omitted.

[0051] FIG. 7 is a perspective view of a mold provided in a molded body casting apparatus according to a second embodiment of the present invention, and FIG. 8 is a perspective cross-sectional view of a mold provided in a molded body casting apparatus according to the second embodiment of the present invention.

[0052] As shown in Figures 7 and 8, the casting mold 20 provided in the slip casting apparatus for molding a molded body of this embodiment differs from the first embodiment in that it has multiple pouring ports and multiple sludge discharge ports. That is, in this second embodiment of the present invention, the casting mold 20 has two pouring ports 20b and 20c and two sludge discharge ports 20d and 20e. An exhaust port 20f is also provided on the top surface of the casting mold 20. The pouring ports 20b and 20c, the sludge discharge ports 20d and 20e, and the exhaust port 20f all communicate with the cavity 20a formed inside the casting mold 20. The numbers of pouring ports, sludge discharge ports, and exhaust ports can be set as desired depending on the configuration of the molded body to be molded.

[0053] Each of the pouring ports 20b and 20c is provided with a pouring valve (not shown), through which a slip can be poured from a pressurizing device (not shown). Each of the sludge discharge ports 20d and 20e is provided with a sludge discharge valve (not shown), through which the slip can be discharged from the casting mold 20. The exhaust port 20f is provided with an exhaust valve (not shown), through which air can be discharged. In this embodiment, each of the pouring ports 20b and 20c and each of the sludge discharge ports 20d and 20e have the same cross-sectional area. As a result, the total cross-sectional area of ​​the pouring ports 20b and 20c is approximately the same as the total cross-sectional area of ​​the sludge discharge ports 20d and 20e.

[0054] In the method for producing a green body according to the second embodiment of the present invention, in the pouring step (corresponding to step S1 in FIG. 4), the sludge discharge valves (not shown) of the sludge discharge ports 20d and 20e are closed. Meanwhile, the pouring valves (not shown) of the pouring ports 20b and 20c are opened, and the exhaust valve (not shown) of the exhaust port 20f is also opened. Then, a pressurizing device (not shown) pours the slurry from the pouring ports 20b and 20c.

[0055] Next, in the circulation step (corresponding to step S4 in FIG. 4), the inlet valve (not shown) for inlet 20c and the drain valve (not shown) for drain outlet 20d are opened, while the inlet valve (not shown) for inlet 20b and the drain valve (not shown) for drain outlet 20e are closed. The exhaust valve (not shown) for exhaust outlet 20f is also closed. In this state, the pressurizing device (not shown) is operated to circulate the slip in the casting mold 20.

[0056] By opening and closing the valves as described above, in this embodiment, the distance between the sludge discharge port 20d, which is open during the circulation process, and the pouring port 20c through which the slip is poured into the casting mold 20, is shorter than the distance between the sludge discharge port 20d and the exhaust port 20f and the distance between the pouring port 20c and the exhaust port 20f. Therefore, during the circulation process, the slip flows sufficiently through the casting mold 20 before being discharged through the sludge discharge port 20d. As a result, any weld lines that may occur in the casting mold 20 can be reliably discharged through the sludge discharge port 20d, thereby effectively preventing the occurrence of weld lines in the molded body. The number and positions of the pouring ports and the sludge discharge ports that are opened during the circulation process can be determined as desired depending on the configuration of the molded body to be molded.

[0057] In this embodiment, the circulation process is also carried out continuously for a predetermined time, and at least at the end of the circulation process, the total volume of the slip introduced through the inlet 20c per unit time and the volume of the slip discharged through the outlet 20d per unit time are made substantially equal. Furthermore, in this embodiment, the inlet 20c and the outlet 20d that are open during the circulation process have substantially the same cross-sectional area.

[0058] When a plurality of inlets and / or sludge discharge ports are opened in the circulation step, it is preferable that the total cross-sectional area of ​​the open inlets and the total cross-sectional area of ​​the open sludge discharge ports are made substantially equal. Furthermore, when a plurality of inlets and a plurality of sludge discharge ports are opened simultaneously in the circulation step, it is preferable that the total volume of the slip introduced through the inlets per unit time and the total volume of the slip discharged through the sludge discharge ports per unit time are made substantially equal.

[0059] Furthermore, in the casting process (corresponding to step S6 in FIG. 4), the pouring valve (not shown) of the pouring port 20c is opened, while the pouring valve (not shown) of the pouring port 20b and the sludge discharge valves (not shown) of the sludge discharge ports 20d and 20e are closed. Then, the slip in the casting mold 20 is pressurized by a pressurizing device (not shown).

[0060] Next, in the sludge discharge step (corresponding to step S8 in FIG. 4), the sludge discharge valves (not shown) of the sludge discharge ports 20d and 20e and the pouring valves (not shown) of the pouring ports 20b and 20c are opened, and the uncoated slip is discharged through these valves. Note that in the coating step and the sludge discharge step, the number and positions of the pouring ports and sludge discharge ports to be opened or closed can be set as desired depending on the configuration of the compact to be molded.

[0061] Finally, the green body in the casting mold 20 is demolded to complete the green body (not shown). In this embodiment, the casting mold 20 is also composed of two halves, which can be separated to remove the green body from the casting mold 20. The completed green body then undergoes drying, glazing, firing, and other processes to become a ceramic product.

[0062] According to the method for producing a green body of the second embodiment of the present invention, a circulation step is carried out before the casting step, in which slip is poured through pouring port 20c while simultaneously being discharged from drainage port 20d, so that the slips poured into mold 20 from pouring ports 20b and 20c collide with each other, and most of the portions where weld lines are likely to occur can be discharged from drainage port 20d. As a result, portions of mold 20 where the slips collide with each other are less likely to remain in mold 20, effectively suppressing the occurrence of weld lines in the green body.

[0063] Furthermore, according to the method for producing a molded article of this embodiment, at the end of the circulation step, the total volume of the slip poured into the casting mold from the pouring port per unit time is made substantially equal to the total volume of the slip discharged from the discharge port per unit time. Therefore, by the end of the circulation step at the latest, the air that has been trapped in the casting mold is completely discharged from the casting mold, and the occurrence of weld lines in the molded article can be sufficiently suppressed.

[0064] Furthermore, according to the method for producing a molded article of this embodiment, at the end of the circulation step, the total volume of the slip poured into the mold through the pouring ports 20b, 20c per unit time is made substantially equal to the total volume of the slip discharged from the discharge ports 20d, 20e per unit time. Therefore, by the end of the circulation step at the latest, the air remaining in the casting mold 20 is completely discharged from the casting mold 20, and the occurrence of weld lines in the molded article can be sufficiently suppressed.

[0065] Furthermore, according to the method for manufacturing a molded body of this embodiment, the circulation step is carried out continuously for a predetermined period of time, so that the weld line portion of the slip that occurs in the casting mold 20 during the pouring step can be sufficiently discharged from the drain port, and the occurrence of weld lines in the molded body can be sufficiently suppressed.

[0066] Furthermore, in the slip casting apparatus for green bodies of this embodiment, the control unit controls the pressurizing device and the sludge discharge valve to execute a circulation step in which the pressurizing device is operated with sludge discharge port 20d open before the casting step, so that most of the portions where weld lines are likely to occur due to collisions between the slips poured into mold 20 from pouring ports 20b and 20c can be discharged from sludge discharge port 20d. As a result, portions of mold 20 where the slips collide are less likely to remain in mold 20, effectively suppressing the occurrence of weld lines in the green body.

[0067] Furthermore, according to the method for producing a green body of this embodiment, the distance between the sludge discharge port 20d, which is open in the circulation step, and the pouring port 20c through which the slip is poured into the casting mold 20 is shorter than the distance between the sludge discharge port 20d and the exhaust port 20f and the distance between the pouring port 20c and the exhaust port 20f, so that in the circulation step, the slip flows sufficiently through the casting mold 20 and is then discharged from the sludge discharge port 20d. This allows the portion of the weld line that occurs in the casting mold 20 to be reliably discharged from the sludge discharge port 20d, and the occurrence of weld lines in the green body can be sufficiently suppressed.

[0068] Furthermore, in the slip casting apparatus for molded bodies of this embodiment, the total cross-sectional area of ​​the pouring ports 20b, 20c is approximately the same as the total cross-sectional area of ​​the sludge discharge ports 20d, 20e. Therefore, the flow rate of the slip poured through the pouring ports and the flow rate of the slip discharged through the sludge discharge ports can be set to be approximately the same during the circulation process. This allows the slip to circulate smoothly during the circulation process, and effectively prevents weld lines from occurring in the molded body.

[0069] Although the embodiment of the present invention has been described above, various modifications can be made to the above-described embodiment. [Explanation of symbols]

[0070] 1 Cast molding equipment 2 Casting mold 2a cavity 2b Pouring port 2c Sludge drainage port 2d exhaust port 4. Pressure device 6 Sludge drain valve 8 Exhaust valve 10 Control Unit 12 Inlet valve 14 Molded body 20 Casting mold 20a cavity 20b Pouring port 20c pouring opening 20d Sludge drainage port 20e Mud removal port 20f exhaust port

Claims

1. A method for producing a molded body by slip pressure molding, comprising: a pouring step of pouring a slip through one or more pouring ports provided in the casting mold; a casting step in which, after the casting mold is filled with the slip, the slip is forced through the pouring opening at a predetermined pressure while a draining opening provided in the casting mold is closed; and A method for producing a molded body, characterized in that a circulation step is carried out before the casting step, in which slip is poured through at least one of the pouring ports while simultaneously discharging the slip from at least one of the discharge ports.

2. 2. The method for producing a molded body according to claim 1, wherein, at the end of the circulation step, the total volume of the slip poured through the pouring port per unit time is made substantially equal to the total volume of the slip discharged through the draining port per unit time.

3. The method for producing a molded article according to claim 1, wherein the circulation step is carried out continuously for a predetermined period of time.

4. A slip casting apparatus for a molded body by slip pressure molding, a casting mold having at least one pouring port and at least one draining port; a pressurizing device for pressurizing the slip so that the slip flows into the pouring opening of the casting mold; a sludge discharge valve that closes or opens the sludge discharge port; a control unit that controls the pressurizing device and the sludge drain valve; and a control unit that executes a circulation step of operating the pressurizing device with the sludge discharge port open after the slip has been filled into the casting mold and before a casting step of operating the pressurizing device with the sludge discharge port closed.

5. 5. The slip casting apparatus according to claim 4, wherein the casting mold further comprises an exhaust port for discharging air trapped in the casting mold, and the distance between the mud discharge port, which is open during the circulation step, and the pouring port through which the slip is poured into the casting mold is shorter than the distance between the mud discharge port and the exhaust port and the distance between the pouring port and the exhaust port.

6. 5. The slip casting apparatus according to claim 4, wherein the total cross-sectional area of ​​said pouring ports is approximately the same as the total cross-sectional area of ​​said sludge discharge ports.

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