Method for producing molded product

Abstract

To provide a technique that can reduce a possibility of scratches or damage occurring to a molded product when the molded product is recovered from an injection molding device onto a tray.SOLUTION: A method for producing a molded product includes: a first step of injecting a plasticized material containing metal powder into a mold using an injection molding device to form a molded product; a second step of recovering the molded product onto a tray covered with cushioning material; and a third step of heating the molded product recovered onto the tray together with the tray and cushioning material in a heating furnace, where the cushioning material contains a granular or fibrous inorganic material.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a molded article. [Background technology]

[0002] Patent Document 1 discloses a technique for aligning and positioning molded products removed from an injection molding device so that they can be automatically loaded onto a pallet. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 6-59937 Summary of the Invention [Problem to be solved by the invention]

[0004] When the molded product is recovered from the injection molding machine onto a tray, there is a possibility that the molded product may be scratched or damaged during recovery. [Means for solving the problem]

[0005] According to a first aspect of the present disclosure, there is provided a method for manufacturing a molded product, comprising: a first step of injecting a plasticized material containing a metal powder into a mold using an injection molding device to form a molded product; a second step of collecting the molded product on a tray covered with a cushioning material; and a third step of heating the molded product collected on the tray together with the tray and the cushioning material in a heating furnace, the cushioning material including a granular or fibrous inorganic material. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a top view showing a schematic configuration of an injection molding device. [Figure 2] FIG. 1 is a perspective view showing a schematic configuration of an injection molding device. [Figure 3]FIG. 2 is a cross-sectional view showing a schematic configuration of a material supply device. [Figure 4] FIG. 2 is a perspective view showing a schematic configuration of a flat screw. [Figure 5] FIG. 2 is a schematic plan view of the barrel. [Figure 6] FIG. 1 is a process diagram showing a method for manufacturing a molded product. [Figure 7] 10A and 10B are diagrams showing some examples of cushioning materials. [Figure 8] FIG. 10 is a diagram showing the measurement results of materials and their weights. [Figure 9] 1A and 1B are diagrams showing cross-sectional observation images of a material before and after vacuum heating. [Figure 10] FIG. 1 shows the results of X-ray diffraction of a material before and after vacuum heating. [Figure 11] 6A to 6C are process diagrams illustrating a method for producing a molded product according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] A. First embodiment: FIG. 1 is a top view showing a schematic configuration of an injection molding apparatus 10 according to a first embodiment. FIG. 2 is a perspective view showing a schematic configuration of the injection molding apparatus 10. Metal powder injection molding is performed in the injection molding apparatus 10. FIGS. 1 and 2 show arrows indicating mutually orthogonal X, Y, and Z directions. The X and Y directions are parallel to a horizontal plane, and the Z direction is opposite to the direction of gravity. The X, Y, and Z directions shown in FIG. 3 and subsequent figures correspond to the X, Y, and Z directions shown in FIGS. 1 and 2. In the following description, when specifying a direction, positive and negative signs are used in combination to indicate the direction indicated by the arrow, with "+" indicating the positive direction and "-" indicating the negative direction opposite to the direction indicated by the arrow.

[0008] The injection molding apparatus 10 comprises a material supplying apparatus 100, a mold clamping apparatus 130, and a control unit 500. The injection molding apparatus 10 injects plasticized material produced by the material supplying apparatus 100 into a molding die 160 to form a molded product. The operation of the material supplying apparatus 100 and the mold clamping apparatus 130 is controlled by the control unit 500. The control unit 500 is configured as a computer equipped with a CPU and memory, and controls each part of the injection molding apparatus 10 by the CPU executing a program stored in the memory. Note that the control unit 500 may also be configured as a circuit.

[0009] A metal forming die 160 is attached to the mold clamping device 130. The forming die 160 is not limited to being made of metal, and may be made of ceramic. The metal forming die 160 is called a mold. The forming die 160 includes a fixed die 161 and a movable die 162. The fixed die 161 is a die that is fixed relative to the material supply device 100. The movable die 162 is a die that can be moved in the mold clamping direction and mold opening direction relative to the fixed die 161 by the mold clamping device 130. In this embodiment, the mold clamping direction is the -Y direction, and the mold opening direction is the +Y direction.

[0010] The mold clamping unit 130 has the function of opening and closing the fixed mold 161 and the movable mold 162. The mold clamping unit 130 includes a motor 131 and a ball screw 132. The mold clamping unit 130 is controlled by a control unit 500. The control unit 500 drives the motor 131 of the mold clamping unit 130 to rotate the ball screw 132, and moves the movable mold 162, which is connected to the ball screw 132, relative to the fixed mold 161, thereby opening and closing the casting mold 160.

[0011] A hopper 30 into which the material for the molded product is fed is connected to the material supply device 100. In this embodiment, a pellet-shaped material containing metal powder and a binder is used as the material for the molded product. The material may be fed to the material supply device 100 not only through the hopper 30 but also through a tube through which the material is pressure-fed, for example.

[0012] The material supply device 100 plasticizes at least a portion of the material supplied from the hopper 30 to produce a plasticized material, and then injects the produced plasticized material into a cavity defined between the fixed mold 161 and the movable mold 162. In this specification, "plasticization" is a concept that includes melting, and refers to changing a material from a solid to a fluid state. Specifically, for a material that undergoes glass transition, plasticization refers to raising the temperature of the material to or above the glass transition point. For a material that does not undergo glass transition, plasticization refers to raising the temperature of the material to or above the melting point.

[0013] 3 is a cross-sectional view showing a schematic configuration of material supplying apparatus 100. Material supplying apparatus 100 includes a plasticizing unit 110 that plasticizes at least a portion of a material to produce a plasticized material, a nozzle 114 that injects the plasticized material, and an injecting unit 120 that communicates with nozzle 114.

[0014] The apparatus includes a plasticizing section 110, a flat screw 111, a barrel 112, and a heater 113 as a heating section.

[0015] The flat screw 111 is accommodated in the accommodation unit 101. The flat screw 111 is also called a rotor or simply a screw. The flat screw 111 is rotated by a motor 118 around a drive shaft 119 of the motor 118 within the accommodation unit 101. A central axis RX, which is the rotation center of the flat screw 111, coincides with the center of the drive shaft 119 of the motor 118 in the XZ plane. In this embodiment, the axial directions of the drive shaft 119 and the central axis RX are aligned along the Y direction. The rotation of the flat screw 111 by the motor 118 is controlled by the control unit 500. The flat screw 111 may be driven by the motor 118 via a reducer.

[0016] A communication hole 115 is formed in the center of the barrel 112. The communication hole 115 is connected to a flow path 116. A cylinder 121 and a nozzle 114, which will be described later, are connected to the flow path 116. A check valve 124 is provided in the flow path 116, upstream of the cylinder 121. The check valve 124 prevents the plasticized material from flowing back from the nozzle 114 toward the flat screw 111.

[0017] The heater 113 heats the barrel 112. Heating by the heater 113 is controlled by the control unit 500. In FIG. 3, the heater 113 is arranged on the −Y direction side of the cylinder 121, but the heater 113 may also be arranged on the +Z direction side or the −Z direction side of the cylinder 121. Furthermore, multiple heaters 113 may be arranged to sandwich the cylinder 121 from the +Z direction side and the −Z direction side.

[0018] FIG. 4 is a perspective view showing a schematic configuration of the flat screw 111. The flat screw 111 has a generally cylindrical shape whose length along the central axis RX is shorter than its length perpendicular to the central axis RX. A spiral groove 202 is formed around a central portion 205 on a groove-forming surface 201 of the flat screw 111 facing the barrel 112. The groove 202 communicates with a material inlet 203 formed on the side surface of the flat screw 111. Material supplied from the hopper 30 is supplied to the groove 202 through the material inlet 203. The grooves 202 are formed by being separated by ridge portions 204. FIG. 4 shows an example in which three grooves 202 are formed, but the number of grooves 202 may be one or more. The groove 202 is not limited to a spiral shape, but may also be a spiral shape or an involute curve shape, or may have a shape extending in an arc from the central portion 205 to the outer periphery.

[0019] 5 is a schematic plan view of the barrel 112. The barrel 112 has an opposing surface 212 that faces the groove-forming surface 201 of the flat screw 111. A communication hole 115 that communicates with the flow path 116 is formed in the center of the opposing surface 212. A plurality of guide grooves 211 are formed in the opposing surface 212, connected to the communication hole 115 and extending in a spiral shape from the communication hole 115 toward the outer periphery. Note that the guide grooves 211 do not necessarily have to be provided in the barrel 112. Furthermore, the guide grooves 211 do not necessarily have to be connected to the communication hole 115.

[0020] The material supplied to the groove 202 of the flat screw 111 is plasticized between the flat screw 111 and the barrel 112 by the rotation of the flat screw 111 and the heating of the heater 113, and flows along the groove 202 and the guide groove 211 by the rotation of the flat screw 111, and is guided to the center portion 205 of the flat screw 111. The material that has flowed into the center portion 205 flows out into the flow path 116 from a communication hole 115 provided in the center of the barrel 112.

[0021] As shown in FIG. 3 , the injection unit 120 includes a cylinder 121 that communicates with the nozzle 114 and is connected to a flow path 116 through which the plasticized material flows, a plunger 122 that moves within the cylinder 121, and a plunger drive unit 123. The plunger drive unit 123 includes a ball screw 126 that moves the plunger 122 along the longitudinal direction of the plunger 122, and a motor 127 that drives the ball screw 126. In this embodiment, when the ball screw 126 is driven by the motor 127, the plunger 122 connected to the ball screw 126 moves forward or backward. "Forward" refers to the direction in which the plunger 122 approaches the flow path 116. "Backward" refers to the direction in which the plunger 122 moves away from the flow path 116.

[0022] In the injection unit 120, the control unit 500 controls the plunger drive unit 123 to perform a suction operation and a delivery operation. The suction operation is an operation in which the plasticized material is sucked into the cylinder 121 from the flow path 116 by moving the plunger 122 backward. The delivery operation is an operation in which the plasticized material sucked into the cylinder 121 is delivered to the nozzle 114 by moving the plunger 122 forward. The control unit 500 controls the injection amount, injection speed, and injection pressure of the plasticized material from the nozzle 114 by adjusting the movement amount and movement speed of the plunger 122 during the suction operation and delivery operation. The suction operation is also called a metering operation.

[0023] After the injection unit 120 performs a delivery operation and the plasticized material is injected into the cavity from the nozzle 114, the mold clamping device 130 drives the ball screw 132 to move the movable mold 162 in the mold opening direction relative to the fixed mold 161, thereby opening the mold. When the mold is opened, an ejector pin (not shown) incorporated in the movable mold 162 protrudes relatively into the cavity, and the molded product is released from the cavity.

[0024] 6 is a process diagram showing the method for manufacturing a molded product in this embodiment. In step S10, the injection molding apparatus 10 injects a plasticized material containing metal powder into the mold 160 to injection-mold the molded product. Step S10 is also referred to as the first step.

[0025] In step S20, the molded articles are collected in a tray 300 covered with cushioning material. In this embodiment, the molded articles are released from the movable mold 162 by the ejector pins and then freely fall into the tray 300 disposed below the injection molding apparatus 10, thereby collecting the molded articles. As shown in FIGS. 1 and 2, the tray 300 collects the molded articles while being transported by a belt-type transport device 310. Therefore, the molded articles fall into different positions within the tray 300 for each shot. The tray 300 that has collected the molded articles is transported to the heating furnace by the transport device 310. The tray 300 may be transported by an unmanned transport vehicle such as an AGV (Automatic Guided Vehicle) or an AMR (Autonomous Mobile Robot). Step S20 is also referred to as the second process.

[0026] In step S30, the molded product collected in the tray 300 is heated together with the tray 300 and the cushioning material in a heating furnace, where it is degreased and sintered. Step S30 is also referred to as the third step. In this embodiment, the above-described manufacturing method is used to manufacture, for example, a gear-shaped part having a center axis and a weight of 0.007 g.

[0027] In this embodiment, the tray 300 and the cushioning material have a heat resistance temperature higher than the sintering temperature of the metal powder contained in the material of the molded product. Because the molded product is sintered in a heating furnace, the heat resistance temperature of the tray 300 and the cushioning material is preferably 1200°C or higher. The tray 300 is made of, for example, ceramic. The cushioning material contains a granular or fibrous inorganic material. The cushioning material has a sintering temperature higher than the sintering temperature of the metal powder contained in the material of the molded product. The cushioning material is preferably non-magnetic. If the cushioning material is non-magnetic, the molded product containing metal can be recovered using a magnet after sintering. To ensure sufficient cushioning properties, the thickness of the cushioning material spread within the tray 300 is preferably 4 mm or more for granular inorganic materials and 12.5 mm or more for fibrous inorganic materials.

[0028] According to the manufacturing method for molded products in the first embodiment described above, cushioning material is spread throughout the tray 300 for collecting molded products, reducing the possibility of scratches or damage to the molded products when the molded products are collected. In particular, in this embodiment, granular or fibrous cushioning material is used as the cushioning material, which prevents the molded products from moving within the tray 300 while the tray 300 is being transported. Therefore, even if the molded products do not have flat portions, they can be transported smoothly. Furthermore, in this embodiment, the molded products are heated together with the tray 300 and cushioning material in the heating furnace, so there is no need to remove the molded products from the tray 300 before heating. This improves the manufacturing efficiency of molded products.

[0029] Furthermore, in this embodiment, the molded articles are collected while the tray 300 is being moved by the conveying device 310. This prevents the molded articles that have dropped from the movable mold 162 onto the tray 300 from coming into contact with molded articles that have already been collected on the tray 300. As a result, contact between the molded articles is prevented, reducing the possibility of scratches or damage to the molded articles.

[0030] FIG. 7 is a diagram showing several examples of cushioning materials. In FIG. 7, materials 1 to 4 are listed as examples of cushioning materials. Materials 1 and 2 are ceramic particles, and materials 3 and 4 are alkaline earth silicate (AES) wool. Specifically, material 1 is Naigai Cerameaads (registered trademark) 60 manufactured by Itochu Ceratec Corporation. Material 2 is FINE-Bz (registered trademark) AZ10#80 manufactured by AGC Ceramics. Material 3 is BSSR1400 Blanket 100 manufactured by Isolite Kogyo Co., Ltd., with a thickness of 25 mm. Material 4 is Fineflex BIO (registered trademark) Blanket #130 manufactured by Nichias Corporation, with a thickness of 25 mm.

[0031] The main chemical components of Material 1 are 61% AL2O3 and 36% SiO2. The largest particle size of Material 1 is 0.425 mm. Material 1 contains 16.9% particles with a particle size of 0.425 mm, 66.4% particles with a particle size of 0.3 mm, 15.9% particles with a particle size of 0.212 mm, and 0.8% particles with a particle size of 0.15 mm. The particle size of the particle with the highest content ratio in Material 1 is 0.3 mm. Material 1 is composed of 100% particles with a particle size of 0.1 mm or larger. The heat resistance temperature of Material 1 is 1825°C.

[0032] The main chemical components of Material 2 are 80% Al2O3, 9.5% ZrO2, 8.5% SiO2, 0.12% Fe2O3, and 0.08% TiO2. Material 2 contains 2.3% particles with a diameter of 0.3 mm, 32% particles with a diameter of 0.212 mm, 28% particles with a diameter of 0.15 mm, 25.6% particles with a diameter of 0.106 mm, 10.6% particles with a diameter of 0.075 mm, and 1.5% particles with a diameter of 0.053 mm. The particle size of the particle with the highest content ratio in Material 2 is 0.212 mm. Material 2 contains 87.9% particles with a diameter of 0.1 mm or larger. The heat resistance temperature of Material 2 is 1500°C.

[0033] The main chemical components of Material 3 are 77% SiO2 and 19% CaO and MgO. The heat resistance temperature of Material 3 is 1400°C.

[0034] The main chemical components of Material 4 are 76% SiO2 and 22% CaO and MgO. The heat resistance temperature of Material 4 is 1300°C.

[0035] Figure 8 shows the results of measuring the weights of materials 1 and 2. Materials 1 and 2 were placed in crucibles, and the crucibles were vacuum-heated at 1200°C. Figure 8 shows the change in weight of materials 1 and 2, including the weight of the crucibles, before and after heating. The weights were measured using an electronic balance. The weight change of materials 1 and 2 before and after heating was less than 0.009% by weight at most, meaning that there was almost no weight change. Therefore, if materials 1 and 2 have particles with a particle size of 0.1 mm or more, as in materials 1 and 2, particles are prevented from floating around and being sucked in when the vacuum is drawn during vacuum heating, and the molded product can be sintered well.

[0036] Figure 9 shows cross-sectional observation images of materials 1 to 4 before and after vacuum heating. The heating conditions were the same as those in the experimental results shown in Figure 8. Figure 9 shows the results of observing the cross sections of materials 1 to 4 before and after heating using a scanning electron microscope at 2000x magnification. According to the images shown in Figure 9, for material 1, no particular difference was observed in the observation results before and after heating. For material 2, heating produced many fine, elongated particles. For materials 3 and 4, heating roughened the surfaces of the materials. In other words, the cushioning material made of ceramic particles showed less change in material before and after heating than the cushioning material made of AES wool.

[0037] FIG. 10 shows the X-ray diffraction results of materials 1 to 4 before and after vacuum heating. The heating conditions were the same as those in the experimental results shown in FIG. 8. According to the X-ray diffraction results shown in FIG. 10, for materials 1 and 3, a cristobalite peak appeared after heating. For material 2, no particular change was observed before and after heating. For material 4, diopside and cristobalite peaks appeared after heating.

[0038] According to the experimental results described above, although some of Materials 1 to 4 become rough or deformed when heated, by spreading them in the tray 300, the possibility of scratches or damage to the molded product when it is collected can be reduced. However, the experimental results described above confirmed that ceramic particles are more resistant to surface roughening before and after heating than AES wool. Furthermore, it was confirmed that Material 2 is less likely to deform than Material 1 when it comes to ceramic particles.

[0039] The smaller the particle size of the ceramic particles, the more likely they are to cause scratches or chips in the molded product, but the more likely they are to adhere to the molded product. Conversely, the larger the particle size of the ceramic particles, the more likely they are to cause scratches or chips in the molded product, but the less likely they are to adhere to the molded product. Therefore, based on the above experimental results, the maximum particle size of the ceramic particles is preferably 0.425 mm or less, and the minimum particle size is preferably 0.1 mm or more. Furthermore, the particle size of the ceramic particles with the highest content ratio is preferably 0.3 mm or less, and preferably 0.2 mm or more.

[0040] B. Second embodiment: 11 is a process diagram showing a method for manufacturing a molded product carried out in the second embodiment. In the second embodiment, injection molding is performed in step S10, and the molded product is collected in tray 300 in step S20. After that, water is sprayed onto tray 300 in step S25 before the molded product is heated in step S30. In the second embodiment, ceramic particles such as material 1 or material 2 described above are used as the cushioning material spread over tray 300.

[0041] As described above, in the second embodiment, water is sprayed onto the tray 300 before the molded article is heated, which prevents the ceramic particles in the tray 300 from floating around and adhering to the molded article. In addition, the sprayed water moistens the ceramic particles in the tray 300, which prevents the ceramic particles from flowing due to vibrations during transportation. Therefore, the molded article can be prevented from being buried in the ceramic particles during transportation of the tray 300.

[0042] C. Other Embodiments: (C1) In the above embodiment, the molded article is recovered onto the tray 300 by freely falling from the movable mold 162 onto the tray 300. Alternatively, the molded article may be recovered by being held by a robot or the like and transported from the movable mold 162 to the tray 300.

[0043] (C2) In the above embodiment, the injection molding apparatus 10 is provided with a flat screw 111 as a screw. Alternatively, the injection molding apparatus 10 may be provided with an in-line screw as a screw.

[0044] D. Other forms: The present disclosure is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit thereof. For example, the technical features of the embodiments corresponding to the technical features in each aspect described below can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted.

[0045] (1) According to a first aspect of the present disclosure, there is provided a method for manufacturing a molded product, comprising: a first step of injecting a plasticized material containing a metal powder into a mold using an injection molding device to form a molded product; a second step of collecting the molded product on a tray covered with a cushioning material; and a third step of heating the molded product collected on the tray together with the tray and the cushioning material in a heating furnace, the cushioning material including a granular or fibrous inorganic material and having a sintering temperature higher than the sintering temperature of the metal powder. In this type of manufacturing method for molded products, the tray is covered with cushioning material, which can prevent scratches or damage to the molded products when they are collected.

[0046] (2) In the above embodiment, the cushioning material may include ceramic particles as the granular inorganic material.

[0047] (3) In the above-described embodiment, the cushioning material may contain alkaline earth silicate wool as the fibrous inorganic material.

[0048] (4) In the above embodiment, the maximum particle size of the ceramic particles may be 0.425 mm or less.

[0049] (5) In the above embodiment, the ceramic particles may include particles of different particle sizes, and the particle size of the particles with the highest content ratio among the different particle sizes may be 0.3 mm or less.

[0050] (6) In the above embodiment, in the second step, the molded articles may be collected on the tray while the tray is moved by a conveying device so that the molded articles do not come into contact with each other. According to this embodiment, contact between the molded articles can be suppressed.

[0051] (7) In the above embodiment, a step of spraying water onto the tray on which the molded article is collected may be included before the third step. According to this embodiment, it is possible to prevent the ceramic particles in the tray from floating in the air. [Explanation of symbols]

[0052] 10... injection molding apparatus, 30... hopper, 100... material supply device, 101... storage section, 110... plasticizing section, 111... flat screw, 112... barrel, 113... heater, 114... nozzle, 115... communication hole, 116... flow path, 118... motor, 119... drive shaft, 120... injection section, 121... cylinder, 122... plunger, 123... plunger drive section, 124...check valve, 126...ball screw, 127...motor, 130...mold clamping device, 131...motor, 132...ball screw, 160...forming die, 161...fixed die, 162...movable die, 201...groove forming surface, 202...groove, 203...material inlet, 204...ridge portion, 205...center portion, 211...guide groove, 212...opposing surface, 300...tray, 310...convex device, 500...control portion

Claims

1. a first step of injecting a plasticized material containing metal powder into a mold using an injection molding device to form a molded product; a second step of collecting the molded product in a tray covered with cushioning material; a third step of heating the molded product collected in the tray together with the tray and the cushion material in a heating furnace, The cushioning material includes a granular or fibrous inorganic material. Manufacturing method of molded products.

2. A method for producing the molded article according to claim 1, The method for manufacturing a molded product, wherein the cushioning material contains ceramic particles as the granular inorganic material.

3. A method for producing the molded article according to claim 1, The method for manufacturing a molded product, wherein the cushioning material contains alkaline earth silicate wool as the fibrous inorganic material.

4. A method for producing the molded product according to claim 2, The method for producing a molded product, wherein the maximum particle size of the ceramic particles is 0.425 mm or less.

5. A method for producing the molded product according to claim 2, the ceramic particles include particles of different sizes; A method for producing a molded product, wherein the particle size of the particles with the highest content ratio among the different particle sizes is 0.3 mm or less.

6. A method for producing the molded article according to claim 1, In the second step, the molded articles are collected into the tray while being moved by a conveying device so that the molded articles do not come into contact with each other.

7. A method for producing the molded product according to claim 2, A method for manufacturing a molded product, comprising a step of spraying water onto the tray in which the molded product is collected, prior to the third step.

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