JP7263016B2 - Mold making method - Google Patents

Description

The present invention relates to a mold manufacturing method and a three-dimensional modeling apparatus.

2. Description of the Related Art Conventionally, there is a so-called 3D printer as a three-dimensional modeling apparatus that realizes a three-dimensional shape drawn by computer graphics (CG) with a resin material, a powder material, or the like. There are various methods for producing three-dimensional objects using 3D printers. For example, there is a material extrusion method for modeling with a resin material, and there is a binder injection method (binder jet method) for modeling with a powder material.

According to the binder injection method, for example, a cement composition for a binder injection type addition manufacturing apparatus described in Patent Document 1 below is used as a powder material, and a water-based binder is sprayed on a desired position to form a powder. A three-dimensional object is produced by solidifying the material. A three-dimensional object is used, for example, in a mold into which molten metal, plastic, or the like (hereinafter referred to as "melt") is injected when casting a casting.

JP 2017-178671 A

However, three-dimensional objects manufactured from hydraulic powder materials such as those described above require a procedure for removing the powder material attached to the three-dimensional object (hereinafter, the procedure for removing the powder material is referred to as "depowder". ), if the mold is used with the powder material adhering to it, the dimensional accuracy of the casting will be low and the casting surface will be rough.

The present invention has been proposed in view of such circumstances. That is, it is an object of the present invention to provide a mold manufacturing method and a three-dimensional molding apparatus that can easily depowder and manufacture a mold for casting a casting having high dimensional accuracy and a beautiful casting surface.

A three-dimensional object manufactured by a three-dimensional modeling apparatus using a binder injection method differs in the ease of depowder (the ease with which powder material adheres) depending on the surface. Therefore, when manufacturing a mold with this three-dimensional modeling apparatus, the surface that is relatively easy to depowder is the surface where the molten material is poured and the casting is formed (hereinafter referred to as the "casting molding surface"). This makes it easier to depowder the molding surface of the casting. If the depowder is suitable, the casting surface will be smooth and suitable for casting.

In order to achieve the above object, a mold manufacturing method according to the present invention includes a lifting procedure for moving a stage for manufacturing a mold to a position relatively low with respect to a reference plane, and a step of crossing the stage from one side. A recoater that moves to the other side moves the powder material on one side from the reference surface to the stage to level it, and a binder is sprayed from the printer head onto the powder material on the stage. A mold manufacturing method for manufacturing a mold used for casting a casting by repeating the lifting procedure, the material filling procedure, and the molding procedure, wherein the molding procedure solidifies the powder material by It is characterized in that the mold is prepared so that the surface of the mold for molding the casting faces the upper surface.

The method for producing a mold according to the present invention is characterized in that the mold is produced such that a portion of the mold having the largest surface area faces the upper surface.

A method of manufacturing a mold according to the present invention is characterized in that the molds are combined to manufacture a core having an outer surface formed by a surface for forming the casting.

The method for producing a mold according to the present invention is characterized in that the mold is dried at a temperature of 40°C to 150°C.

A three-dimensional modeling apparatus according to the present invention includes a stage that moves by a predetermined amount to a position relatively low with respect to a reference plane, and a stage that moves from one side to the other side across the stage, so that powder on one side is a recoater that moves the material from the reference surface to the stage to level it, and a printer head that solidifies the powder material by spraying a binder onto the powder material on the stage, and A three-dimensional modeling apparatus for producing a mold used for casting a casting by repeating a lifting procedure, a material filling procedure by the recoater, and a modeling procedure by the printer head, wherein the surface of the mold for molding the casting is , and a direction determining means for determining the direction of the mold to be the upper surface side.

In the mold manufacturing method according to the present invention, the mold is manufactured so that the surface of the mold for molding the casting faces the upper surface. That is, the upper surface of the produced mold becomes the casting surface. Since the ease of depowder in the mold is better on the upper surface than on the lower surface, if the upper surface of the mold is the casting surface, it is easier to depowder the casting surface, and the casting surface is smooth and appropriate. Become. Therefore, depowder is easy, and a mold for casting a casting having high dimensional accuracy and a beautiful casting surface can be produced.

For example, when a plurality of molds are combined to form a main mold, the casting surfaces of the respective molds face each other inside. That is, all of the casting surfaces of the master mold (the inside of the master mold) are excellent depowder-friendly surfaces. Therefore, depowder is easy, and a main mold for casting a casting having high dimensional accuracy and a beautiful casting surface can be produced.

In the mold manufacturing method according to the present invention, the mold is manufactured so that the portion of the mold with the largest surface area faces the upper surface. For example, when casting a casting with a complicated shape, the molding surface of the mold is of course the same shape as the casting and is complicated. Therefore, in order to appropriately cast a casting having a complicated shape, it is preferable that the casting molding surface be easily depowdered in order to obtain an appropriate casting molding surface. Since a complex shape generally has a relatively large surface area, the mold is manufactured so that the casting surface with the largest surface area is the upper surface of the mold. Therefore, it is possible to easily depowder even a complex casting molding surface, and to produce a mold for casting a casting having high dimensional accuracy and a beautiful casting surface.

A method for manufacturing a mold according to the present invention is to manufacture a core having an outer surface formed by a surface for forming a casting by combining molds. That is, while the core has a casting molding surface on the entire outer peripheral surface, if this core is made, for example, half by half, and a mold having a casting molding surface that is excellent in ease of depowder is combined and made, the middle All external surfaces of the child are excellent for ease of depowder. Therefore, it is possible to easily depowder and manufacture a core for casting a casting having high dimensional accuracy and a beautiful casting surface.

The mold making method according to the present invention may include a drying procedure at a temperature of 40 to 150 degrees. That is, drying the mold at a given temperature increases the ease of depowder. Therefore, a mold for casting a casting having high dimensional accuracy and a beautiful casting surface can be produced.

The three-dimensional modeling apparatus according to the present invention has a direction determining means for determining the direction of the mold so that the surface for molding the casting is the upper surface side. Therefore, depowder is easy, and a mold for casting a casting having high dimensional accuracy and a beautiful casting surface can be produced.

FIG. 1 shows an outline of a three-dimensional modeling apparatus used in a mold manufacturing method according to a first embodiment of the present invention, where (a) is a plan view and (b) is a cross-sectional view taken along the line AA in (a). be. FIG. 2 is an external perspective view of a mold manufactured by the mold manufacturing method according to the first embodiment of the present invention. FIG. 3 is an external perspective view of a mold manufactured by a mold manufacturing method according to a comparative example. FIG. 4 is an external perspective view of a mold manufactured by a mold manufacturing method according to a reference example.

Below, the mold manufacturing method according to the first embodiment of the present invention will be described based on the drawings. FIG. 1 shows an outline of the configuration of a three-dimensional modeling apparatus (hereinafter, the three-dimensional modeling apparatus is referred to as a "3D printer") used in the mold manufacturing method.

The 3D printer 1 materializes the mold M by a binder injection method based on the data of the mold M expressed in three dimensions. First, an outline of the configuration of the 3D printer 1 will be described.

As shown in FIG. 1, a 3D printer 1 includes a stage 3 that moves up and down with respect to a reference plane 2, a material placement section 4 that is outside the stage 3 and on the reference plane 2, and this material placement section. A material supply unit (not shown) that supplies the powder material 5 to the placement unit 4, a recoater 6 that moves the powder material 5 from the material placement unit 4 to the stage 3 to level it, and the powder material on the stage 3 It has a printer head 7 for spraying a binder on 5 and a guide section 8 for freely moving the printer head 7 . In the following description, as shown in FIG. 1, three mutually orthogonal axes are the X-axis, the Y-axis, and the Z-axis. 3, the depth direction of the stage 3 is defined as the Y-axis, and the height direction along which the stage 3 moves up and down is defined as the Z-axis. On the X-axis, one of the widths is the right side and the other is the left side. On the Y axis, one side is the back side and the other side is the front side.

The stage 3 is in the shape of a rectangular flat plate, and is a place where the mold M is produced. A lifting mechanism 9 is attached to the bottom surface of the stage 3 , and the Z-axis is moved up and down by the operation of the lifting mechanism 9 . The material placement section 4 is arranged outside the stage 3 and on the back side of the stage 3 . The material supply section is arranged outside the stage 3 and above the material placement section 4 . Note that the material supply section may be arranged outside the stage 3 and on the back side of the material placement section 4 . The recoater 6 has a rod shape elongated in the X-axis direction and is arranged on the reference plane 2 . The recoater 6 freely moves on the reference surface 2 in parallel with the stage 3 between the back side of the material placement section 4 and the front side of the stage 3 on the Y-axis. The guide part 8 is longitudinal in the X-axis direction and freely moves between the back side and the front side of the stage 3 in the Y-axis while being parallel to the stage 3 . The printer head 7 is supported by the guide portion 8 and freely moves along the guide portion 8 along the X-axis.

Next, a procedure for manufacturing the mold M by a binder injection method using the 3D printer 1 will be described. The 3D printer 1 is input with data of a desired mold M represented in three dimensions. The fabrication procedure includes an orientation procedure, a material supply procedure, a material filling procedure, a shaping procedure, a drying procedure, and a depowder procedure. Each procedure is provided in the 3D printer 1 as direction determination means, material supply means, material filling means, modeling means, drying means, and depowder means. The drying procedure (drying means) and the depowder procedure (depowder means) may be realized by a device (not shown) separate from the 3D printer 1. A drying procedure is not essential.

The orientation procedure determines the orientation of the template M to be produced. More specifically, the direction of the mold M is determined so that the molding surface of the mold M faces the upper surface. The selection of the casting surface is arbitrary, but the part of the mold M that has the most complicated shape is selected as the casting surface. For example, in addition to the point with the largest surface area, the point with the most conspicuous height difference, unevenness, curves, etc., is selected as the casting forming surface. In other words, the surface of the mold M into which the molten material is not poured and which does not come into contact with the casting is the lower surface side or the side surface side.

In FIG. 1, the stage 3 is aligned on the same plane as the reference plane 2 in the initial state. In the elevating procedure, the elevating mechanism 9 operates to lower the stage 3 along the Z-axis, thereby moving the stage 3 to a position relatively lower than the reference plane 2 by a predetermined amount.

In the material supply procedure, the powder material 5 is supplied from the material supply section to the material placement section 4 . The powder material 5 is piled up on the material placing portion 4 . Note that the lifting procedure and the material supply procedure may be executed in order or simultaneously.

In the material filling procedure, the recoater 6 moves from the back side of the material placement section 4 to the front side across the stage 3 on the Y axis, so that the powder material 5 is transferred from the material placement section 4 to the stage 3. be moved. The powder material 5 is leveled on the stage 3 by moving the recoater 6 on the stage 3 along the reference plane 2 . In some cases, the material supply procedure is repeated multiple times so that the stage 3 is filled with the powder material 5 and leveled.

In the modeling procedure, while the guide unit 8 moves in the Y-axis direction and the printer head 7 moves in the X-axis direction, the binder is sprayed from the printer head 7 at a preset position. The powder material 5 is solidified at the point where the contact is made. To explain the operation of the guide section 8 and the printer head 7 in detail, for example, the guide section 8 is first arranged on the frontmost side in the production position. At this position, the printer head 7 moves from the right side to the left side along the guide portion 8 and ejects the binder. Next, the guide portion 8 moves to the back side by a predetermined amount, and at this position, the printer head 7 moves from the right side to the left side and ejects the binder. This operation is repeated, and the guide part 7 moves to the innermost side of the mold M.

According to the lifting procedure, material supply procedure, material filling procedure, and modeling procedure of the first round, the first laminate having a height corresponding to a predetermined amount by which the stage 3 descends is modeled in the desired mold M. In this way, the lifting procedure, the material supply procedure, the material filling procedure, and the modeling procedure are repeated a plurality of times, so that the first to n-th laminates connected in the Z-axis direction form the desired mold M on the stage. 3. Here, the upper side of the first laminate serves as a molding surface, and the lower surface of the first laminate serves as a surface that does not come into contact with the melt or casting.

In the drying procedure, the mold M, which is buried in the powder material 5 or from which the powder material 5 has been appropriately removed, is left to dry for 3 hours or longer. At that time, the mold M is dried in an atmosphere of 40 to 150 degrees. The drying procedure may be shortened in time as the temperature is increased. For example, if it is 150 degrees, it may be about 5 minutes. If the temperature exceeds 150 degrees, the structure may be destroyed and the mold M may become fragile. Also, in the drying procedure, drying may be performed at normal temperature (for example, room temperature of about 20° C.) for 3 hours or more. Also, it may be executed by a device (not shown) other than the 3D printer 1 . The upper surface of the mold M can be easily depowdered without performing the drying procedure, and the lower surface can be easily depowdered by performing the drying procedure. Even when the core, which is the second embodiment of the present invention described later, is produced as an integral body, if the complex surface is produced as the upper surface and the drying procedure is performed, the casting surface is relatively beautiful and can be easily depowdered. It becomes a possible core.

In the depowder procedure, the powdered material 5 adhering to the mold M is removed, for example, by a brush or air from an air compressor. In the depowder procedure, the drying procedure may be executed by another device (not shown) other than the 3D printer 1 .

The shape of the template M produced in the first embodiment is various. For example, there are cases in which the main mold is composed of a single mold M, and cases in which a plurality of molds M are combined to constitute the main mold. In the former case, the specific outer surface of the main mold (single mold M) becomes the casting molding surface, and in the latter case, the inside of the main mold (the inside surrounded by multiple molds M) becomes the casting molding surface. becomes. In the latter case, for example, the upper mold M and the lower mold M of the main mold divided into upper and lower parts are separately manufactured, and then the respective molds M are combined. Each mold M is manufactured so that the casting surface faces upward, and when the molds M are combined, the casting surface of the upper mold M faces downward, and the casting surface of the lower mold M faces downward. is directed upwards. The entire interior of the completed main mold serves as the casting molding surface, and the hollow portion, which is the inner side of the main mold, is composed only of the casting molding surface.

In the mold manufacturing method according to the second embodiment of the present invention, a core is manufactured by combining the molds M manufactured by the mold manufacturing method according to the first embodiment. A core is used, for example, as a mold for forming a hollow portion when casting a hollow casting. In other words, the entire outer surface of the core produced by combining the molds M is the casting forming surface.

Next, the powder material 5 used in the manufacturing method will be described.

The powder material 5 is a hydraulic composition such as cement, gypsum, or lime, and contains, for example, a specific proportion of a polymer with respect to 100 parts by mass of a binder containing a specific proportion of calcium aluminate. Specifically, the hydraulic composition has the following structure.

[1] A hydraulic composition containing 2 to 12 parts by mass of a polymer per 100 parts by mass of a binder containing 50 to 100% by mass of calcium aluminate.
[2] The hydraulic composition according to [1] above, wherein the calcium aluminate is amorphous calcium aluminate.
[3] The hydraulic composition according to [1] or [2], wherein the polymer is polyvinyl alcohol.
[4] The hydraulic composition according to [3], wherein the polyvinyl alcohol has a saponification degree of 80 to 90 mol%.
[5] The hydraulic composition according to [3] or [4], wherein the polyvinyl alcohol has an average particle size of 150 µm or less.
[6] The binder contains 0 to 20% by mass of cement whose setting (initial setting) is within 30 minutes as measured in accordance with JIS R 5210, with the entire binder being 100% by mass. The hydraulic composition according to any one of -[5].
[7] The hydraulic composition according to any one of [1] to [6], wherein the binder contains 0 to 5% by mass of gypsum in terms of anhydrous gypsum based on 100% by mass of the entire binder.

Since the hydraulic composition described above has high strength development and high heat resistance, when it is used for the mold M, it generates little gas during casting and can produce castings with no defects.

The hydraulic composition contains 2 to 12 parts by mass of the polymer with respect to 100 parts by mass of the binder containing 50 to 100% by mass of calcium aluminate.

Hereinafter, calcium aluminate, which is an essential component of the binder, and cement, which is an optional component, will be separately described in detail.

<Calcium Aluminate>
The calcium aluminate is 3CaO.Al ₂ O ₃ , 2CaO.Al ₂ O ₃ , 12CaO.7Al 2 O ₃ , 5CaO.3Al ₂ O 3 , CaO.Al _{2 O 3 ,} 3CaO.5Al ₂ O ₃ , _or CaO Calcium aluminates such as 2Al ₂ O ₃ ; including calcium fluoroaluminates such as 3CaO 3Al ₂ O ₃ .CaF ₂ and 11CaO 7Al ₂ O ₃ .CaF ₂ in which halogen is dissolved or substituted in calcium aluminate calcium haloaluminate; calcium sodium aluminate such as 8CaO.Na ₂ O.3Al ₂ O ₃ and 3CaO.2Na ₂ O.5Al ₂ O ₃ ; calcium lithium aluminate; alumina cement; , Ti, Fe, Mg, Cr, P, F, S, and other trace elements (including oxides, etc.) dissolved in a solid solution.
Amorphous calcium aluminate is produced by melting a raw material and then quenching it. Therefore, it has substantially no crystalline structure. Since early strength development is high, the vitrification rate is preferably 90% or more.
The CaO/Al ₂ O ₃ molar ratio of the calcium aluminate is preferably 1.5-3.0, more preferably 1.7-2.4. When the molar ratio is 1.5 or more, the hydraulic composition exhibits high early strength, and when it is 3.0 or less, the hydraulic composition has high heat resistance.
Further, the content of calcium aluminate is preferably 50 to 100% by mass when the total of binders including calcium aluminate and optional components such as cement and gypsum is taken as 100% by mass. When this value is 50% by mass or more, the hydraulic composition exhibits high early strength development and high heat resistance. The value is preferably 60 to 100% by mass, more preferably 70 to 100% by mass, still more preferably 80 to 95% by mass.
Also, the Blaine specific surface area of calcium aluminate is preferably 1000 to 6000 cm ² /g, more preferably 1500 to 5000 cm ² /g, in order to obtain sufficient early strength development and suppress dust generation. Incidentally, the Blaine specific surface area of calcium aluminate is more preferably 1000 to 2500 cm ² /g, particularly preferably 1500 to 1500 cm 2 /g, in order to achieve uniform spreading in the additive manufacturing apparatus and not to reduce the strength of the mold. 2000 cm ² /g.

<Cement>
Cement is an optional component of the binder, and if the setting (initial setting) measured according to JIS R 5210 is within 3 hours and 30 minutes, the early strength development after 3 hours from the time of manufacturing the mold M is It is preferable because it is high, and the coagulation (initial) is more preferably within 1 hour.
The content of cement in the binder is preferably 50% by mass or less, more preferably 30% by mass or less, and still more preferably 20% by mass or less, based on 100% by mass of the entire binder, in order to improve early strength development. , and particularly preferably 10% by mass or less.
Also, the content of calcium silicate in the cement is preferably 25% by mass or more. If the content is 25% by mass or more, the strength development after one day of age is high, and if long-term strength development is required, the content is preferably 45% by mass or more.
The cement is selected from fast-hardening cement, ultra-fast-hardening cement, ordinary Portland cement, high-early strength Portland cement, moderate heat Portland cement, low heat Portland cement, white Portland cement, ecocement, blast furnace cement, fly ash cement, and cement clinker powder. One or more types are mentioned. Cement clinker powder is also included in cement.
Among these, fast-hardening cement, ultra-rapid-hardening cement, or water-stopping cement, which sets (initial setting) within 30 minutes, is preferable because of its high early-stage strength development. Commercially available products such as fast-hardening cement include Super Jet Cement (SJC: manufactured by Taiheiyo Cement Co., Ltd.), Jet Cement (manufactured by Sumitomo Osaka Cement Co., Ltd.), Lion Shisui (registered trademark, manufactured by Sumitomo Osaka Cement Co., Ltd.), and Denka Super Cement. (manufactured by Denka).

<Gypsum>
Gypsum is an optional component of the binder, and includes one or more selected from anhydrous gypsum, hemihydrate gypsum, and dihydrate gypsum. Among these, gypsum hemihydrate is preferred because of its higher early strength development.
The content of gypsum in the binding material is preferably 5% by mass or less in terms of anhydrous gypsum, with the entire binding material being 100% by mass, in order to improve strength and prevent gas and graphite spheroidization defects during the production of castings. , more preferably 3% by mass or less, and still more preferably 1% by mass or less.

In addition, the gypsum may be gypsum contained in cement, and ultra-fast-hardening cement (for example, Taiheiyo Cement Co., Ltd. Super Jet Cement) having a gypsum content of 5% by mass or more in terms of anhydrous gypsum in cement contains calcium By mixing it with aluminate and using it as a binding material, early strength development is further improved.

<Polymer>
The content of the polymer in the hydraulic composition is preferably 2 to 12 parts by mass in terms of solid content with respect to 100 parts by mass of the binder, in order to increase the strength of the hydraulic composition. If the polymer content is less than 2 parts by mass, the effect of improving the strength is low, and bleeding may occur, resulting in poor dimensional accuracy. In some cases, cracks may occur, and molds with complicated shapes cannot be manufactured. The content of the polymer is more preferably 3 to 12 parts by mass and even more preferably 4 to 10 parts by mass with respect to 100 parts by mass of the binder.
The polymer is a polymer dispersion, re-emulsified powder resin, etc. defined in JIS A 6203 in terms of polymer form, and polyacrylate, ethylene/vinyl acetate copolymer in terms of polymer type. , styrene/butadiene copolymer, vinyl acetate/vinyl versatate copolymer, vinyl acetate/vinyl versatate/acrylate terpolymer, polyvinyl alcohol, maltodextrin, epoxy resin, and urethane resin One or more types are mentioned.
Among these, polyvinyl alcohol (partially saponified or completely saponified polyvinyl acetate) is preferable, and polyvinyl alcohol having a degree of saponification of 85 to 90 mol% is more preferable, since early strength development can be obtained. .
Further, the average particle diameter (median diameter D50) of the polyvinyl alcohol is preferably 10 to 150 μm, more preferably 30 to 90 μm, since high strength can be obtained, since early strength development can be obtained. Therefore, when polyvinyl alcohol is mixed and pulverized with one of the binders or raw materials of a plurality of binders to adjust the particle size, the particles can be finer and homogeneously mixed, and early strength development can be enhanced.
The polymer may be used by mixing it with a binder or sand in powder form, or may be used by dissolving it in water, which will be described later.

<Sand>
The sand is not particularly limited as long as it is refractory sand, and examples include one or more selected from silica sand, olivine sand, zircon sand, chromite sand, alumina sand, artificial sand, and the like.
Further, the amount of sand compounded is preferably 100 to 600 parts by mass with respect to 100 parts by mass of the binder. If the value is within the range, fire resistance and strength development can be ensured. The blending amount is more preferably 150 to 500 parts by mass, more preferably 200 to 400 parts by mass with respect to 100 parts by mass of the binder.

<Curing accelerator>
The hydraulic composition can further contain a curing accelerator as an optional component in order to improve strength development. The curing accelerator is one or more selected from alkali metal carbonate, alkali metal lactate, alkaline earth metal lactate, and alkali metal silicate. These curing accelerators are highly effective in improving the strength development in a hydraulic composition having a polymer content of 2 to 6 parts by mass with respect to 100 parts by mass of the binder. In addition, these curing accelerators are highly effective in improving the strength development when the curing temperature described below is as low as 10 to 40°C.
And (i) the alkali metal carbonate includes one or more selected from sodium carbonate, potassium carbonate, and lithium carbonate. Also, (ii) the alkali metal lactate is
One or more selected from sodium lactate, potassium lactate, and lithium lactate can be used. (iii) The alkaline earth metal lactate includes one or more selected from calcium lactate and magnesium lactate. In addition, (vi) the alkali metal silicate may be one or more selected from sodium silicate, potassium silicate, and lithium silicate.
The content of the curing accelerator is preferably 3 to 10 parts by mass with respect to 100 parts by mass of the binder. If the content of the curing accelerator is within this range, it is possible to ensure early strength development for rapid modeling and strength that can be handled. The content of the curing accelerator is more preferably 4 to 9 parts by mass, more preferably 5 to 8 parts by mass, per 100 parts by mass of the binder. The curing accelerator may be mixed in advance with the hydraulic composition, or may be used by dissolving in water supplied from an additive manufacturing device.

<Others>
In order to facilitate the operation (de-powder) of removing the uncured powder of the hydraulic composition remaining after molding from the mold M, the hydraulic composition is further optionally added to the total 100 parts by mass of the binder. 0.1 to 2 parts by mass, more preferably 0.5 to 1.5 parts by mass of hydrophobic fumed silica can be included as a component of. Here, hydrophobic fumed silica is silica powder obtained by treating the surface of fumed silica with silane or siloxane to make the surface hydrophobic.
Further, the BET specific surface area of the hydrophobic fumed silica is preferably 30 to 300 m ² /g in order to further increase the removal efficiency of the powder of the hydraulic composition. If the BET specific surface area of the hydrophobic fumed silica is within this range, the fluidity of the powder is improved, the surface spread by the additional manufacturing device is flat, and the weight of the mold M is reduced without lowering the strength. can. Further, since the air permeability of the mold M is improved, defects are less likely to occur even if gas is generated during the production of castings. Hydrophobic fumed silica is also effective in preventing caking of powder and improving mixability.

The hydraulic composition may further contain arbitrary components such as blast furnace slag, fly ash, silica fume, silica fine powder, and limestone powder as strength development modifiers.

<Method for making template M>
In the mold manufacturing method, the mold M is manufactured using the additive manufacturing apparatus and the hydraulic composition used in the present invention. The additive manufacturing device is not particularly limited, and a commercially available product such as a powder lamination type additive manufacturing device can be used. Also, the hydraulic composition is prepared by mixing the above components with a commercially available mixer or by hand. When a plurality of materials are used as the binding material, the binding materials may be mixed in advance using a commercially available mixer or manually, or may be mixed and pulverized using a pulverizer.
Moreover, water can be used as a binder. As the water, ordinary tap water, well water, or the like can be used. The hydraulic composition preferably contains 28 to 60 parts by mass of water and sand with respect to 100 parts by mass of the binder. If the blending ratio of water is within this range, strength development can be ensured. The mixing ratio of water is preferably 30 to 55 parts by mass, more preferably 32 to 45 parts by mass, from the viewpoint of increasing the strength and dimensional accuracy of the mold M. In addition, since water imparts various functions required, one or more selected from thickeners, lubricants, fluidizing agents, surfactants, and surface tension reducing agents may be mixed and used. good.

Methods for curing the mold M include aerial curing alone, aerial curing followed by underwater curing, and surface impregnation curing. Among these, air curing alone is preferable from the viewpoint of early development of strength and suppression of water vapor generated during casting production. The temperature for air curing is preferably 10 to 100°C, more preferably 30 to 80°C, from the viewpoint of strength enhancement by calcium aluminate, cement and polymer. The relative humidity in air curing is preferably 10 to 90%, more preferably 15 to 80%, still more preferably 20 to 60%, from the viewpoint of sufficient strength development and production efficiency. Furthermore, the air curing time is preferably 1 hour to 1 week, more preferably 2 hours to 5 days, still more preferably 3 hours to 4 days, from the viewpoint of sufficient strength development and production efficiency.

Next, an example of a method for making a mold will be described.

The 3D printer used in the examples is a binder injection system manufactured by 3D System (ProJet 660Pro), and the main specifications are as follows.
Stage: 254 x 381 x 203 (mm)
Lamination pitch: 100 (μm)
Lamination speed: about 28 (mm/h)

Molds M ₁ , M ₂ and M ₃ were produced using the 3D printer described above. FIGS. 2-4 show each of the templates M ₁ , M ₂ , M ₃ produced. As shown in FIGS. 2-4, the molds M ₁ , M ₂ , M ₃ are rectangular parallelepipeds having a top surface 10 , a side surface 11 and a bottom surface 12 . Further, side A, side B, and side C are defined, and design dimensions of molds M ₁ , M ₂ , and M ₃ are as follows.
Side A = 10 (mm)
Side B = 16 (mm)
Side C = 80 (mm)

<Materials used>
The formulation of the powder material that is the basis of the mold M is: amorphous calcium aluminate: super jet cement: Espearl: Cerabeads = 0.9: 0.1: 1: 1
2% polymer was added to this mixture. Details are as follows.
(1) Amorphous Calcium Aluminate Amorphous Calcium Aluminate A trial product with a CaO/Al ₂ O ₃ molar ratio of 2.2, a vitrification rate of 95% or more, and a Blaine specific surface area of 3490 cm ² /g. be.
(2) Cement Super Jet Cement, manufactured by Taiheiyo Cement Co., Ltd., calcium silicate content of 47% by mass, initial setting of 30 minutes, Blaine specific surface area of 4700 cm ² /g. However, it contains 14% by mass of anhydrous gypsum.
(3) Sand Equal amounts of the following two types of artificial foundry sand were mixed and used.
Sand 1 Alumina type, trade name Espearl #180L, manufactured by Yamakawa Sangyo Co., Ltd. Sand 2 alumina type, trade name Naigai Cerabeads #1450 (registered trademark), manufactured by Itochu Ceratec Co., Ltd. (4) Polymer Polyvinyl alcohol Product number 22-88S1 (PVA217SS), Made by Kuraray Co., Ltd. Saponification degree is 87 to 89%, average particle diameter (median diameter D50) is 60 μm, content of particles larger than 94 μm is 29% by mass, content of particles larger than 77 μm is 47% by mass, 10% diameter (D10) is 25 μm and 90% diameter (D90) is 121 μm.
(5) Water 3% by mass glycerol aqueous solution (binder solution for ProJet 660Pro), manufactured by 3D System. The water volume settings for the device are 65% external and 90% internal, giving a water/binder ratio of approximately 30%.

The mold _M1 of the example was manufactured so that the casting surface faced the upper surface. The casting mold _M2 of the comparative example was produced so that the casting surface faced the lower surface. The mold _M3 of the reference example is the same as the mold _M2 , and the lower surface is a casting molding surface. Three molds M ₁ , M ₂ and M ₃ were prepared for each of the examples, comparative examples, and reference examples.

In the example, after the mold _M1 was produced, it was left in a room of about 20 degrees for 3 hours to perform depowder. In each of the first to third molds _M1 , the bottom surface 12 and side surface 11 were completely depowdered. Next, the upper surface 10 (casting molding surface) of each was blown with a constant amount of air for 30 seconds, and then the weight was measured (first measured value of the example). After that, the upper surface 10 (casting molding surface) was completely depowdered and weighed (Example 2 measurement). The difference between the first measured value of the example and the second measured value of the example is the amount of powder material adhering to the top surface 10 (casting surface). The results are as follows.

First mold M ₁ : Example 1 measured value - Example 2 measured value = 0.1 g
Second mold M ₁ : Example 1 measured value - Example 2 measured value = 0.1 g
Third mold M ₁ : Example 1 measured value - Example 2 measured value = 0.1 g

That is, it can be seen from the examples that the mold _M1 is manufactured so that the casting surface faces the upper side, and that the casting surface of the mold M1 is easily depowdered. In other words, it can be seen that the upper surface 10 is easier to depowder than the lower surface 12 of the mold made in the mold making method.

In the comparative example, after the mold _M2 was produced, it was left in a room of about 20 degrees for 3 hours to perform depowder. In the first to third mold _M2 , the top surface 10 and side surface 11 respectively were completely depowdered. Next, the lower surface 12 (casting molding surface) of each was blown with a constant amount of air for 30 seconds, and then the weight was measured (comparative example first measured value). After that, the lower surface 12 (casting molding surface) was completely depowdered and the weight was measured (comparative example second measurement value). The difference between the first measured value of the comparative example and the second measured value of the comparative example is the amount of powder material adhering to the lower surface 12 (casting molding surface). The results are as follows.

First mold M ₂ : Comparative example first measured value - Comparative example second measured value = 1.3 g
Second mold M ₂ : Comparative Example 1st measured value - Comparative Example 2nd measured value = 1.4 g
Third mold M ₂ : Comparative Example 1st measured value - Comparative Example 2nd measured value = 1.4 g

In other words, it can be seen from the comparative examples that the casting mold _M2 , which is manufactured so that the casting surface faces downward, is difficult to depowder. In other words, the mold made in the mold making method is found to be more difficult to depowder on the bottom surface 12 than on the top surface 10 .

In the reference example, after being left in a room of about 20°C for 3 hours, drying was performed in an atmosphere of 40°C for 3 hours. In the first to third mold _M3 , the top surface 10 and side surface 11 respectively were completely depowdered. Next, the lower surface 12 (casting molding surface) of each was blown with a constant amount of air for 30 seconds, and then the weight was measured (reference example first measured value). After that, the lower surface 12 (casting molding surface) was completely depowdered and the weight was measured (reference example second measurement value). The difference between the reference example first measurement value and the reference example second measurement value is the amount of powder material adhering to the lower surface 12 (casting molding surface). The results are as follows.

First mold M ₃ : Reference Example 1st measured value - Reference Example 2nd measured value = 0.1 g
Second mold M ₃ : Reference Example 1st measured value - Reference Example 2nd measured value = 0.1 g
Third mold M ₃ : Reference Example 1st measured value - Reference Example 2nd measured value = 0.1 g

That is, even if the mold _M3 is made so that the casting surface is on the bottom side, it is possible to easily depowder the casting surface by drying it in an atmosphere of 40 degrees for 3 hours. can be seen from In other words, it can be seen that the ease of depowder is increased by drying the mold produced in the mold production method at a predetermined temperature.

Next, the effects of the mold manufacturing method and the 3D printer 1 will be described.

As described above, the mold manufacturing method and the 3D printer 1 have a direction determination procedure (orientation determination means). Orientation is determined. With this configuration, the upper surface of the produced mold M inevitably serves as the casting molding surface. As can be seen from the examples and the like, the ease of depowder in the mold M is better on the upper surface than on the lower surface. There is, and the casting molding surface becomes smooth and suitable. Therefore, it is possible to manufacture a casting mold M for casting a casting that is easy to depowder and has high dimensional accuracy and a beautiful casting surface.

Also, in the orientation procedure, the part of the mold M that has the most complicated shape is selected as the casting surface. Therefore, it is possible to easily depowder even a complicated casting molding surface, and to manufacture a mold M for casting a casting having high dimensional accuracy and a beautiful casting surface.

As can be seen from the examples and the like, the mold manufacturing method and the 3D printer 1 increase the ease of depowder by drying the mold M for 3 hours or more. Therefore, the mold M for casting a casting having high dimensional accuracy and a beautiful casting surface can be produced.

Also, in the drying procedure, it is dried in an atmosphere of 40 to 150 degrees. That is, as can be seen from the reference example, drying the mold M at a predetermined temperature increases the ease of depowder. Therefore, the mold M for casting a casting having high dimensional accuracy and a beautiful casting surface can be produced. Even without the drying procedure of the present embodiment, the ease of depowder is still superior on the top surface compared to the bottom surface.

In the mold manufacturing method according to the second embodiment, a core is manufactured by combining the molds M manufactured by the mold manufacturing method according to the first embodiment. That is, all the outer surfaces of the core produced by combining the molds M become casting molding surfaces, and all of the outer surfaces of the core become surfaces excellent in ease of depowder. Therefore, it is possible to easily depowder and manufacture a core for casting a casting having high dimensional accuracy and a beautiful casting surface.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments. Various design changes can be made to the present invention without departing from the scope of the claims.

1 3D printer (three-dimensional modeling device)
2 reference surface 3 stage 4 material mounting unit 5 powder material 6 recoater 7 printer head 8 guide unit 9 lifting mechanism 10 upper surface 11 side surface 12 lower surface M, M _{1 to 3} molds (molds)

Claims (5)

A lifting procedure for moving a stage for manufacturing a part of a mold to a relatively low position with respect to a reference plane, and a recoater that moves from one side to the other side across the stage to move the powder on one side. A material filling procedure of moving the body material from the reference surface to the stage to level it, and a modeling procedure of solidifying the powder material by spraying a binder from a printer head onto the powder material on the stage. A mold manufacturing method for manufacturing a part of the mold used for casting a casting by repeating the lifting procedure, the material filling procedure, and the modeling procedure , and combining parts of the mold to produce the mold. There is
Of the part of the mold, a part of the mold is produced so that the surface for molding the casting is the upper surface side , and a plurality of parts of the mold are combined to produce the mold .
A mold manufacturing method characterized by: A part of the mold is produced so that the part with the largest surface area of the mold is on the upper surface side , and a plurality of parts of the mold are combined to produce the mold .
2. The mold manufacturing method according to claim 1, characterized in that: The mold having an inner surface formed by the surface forming the casting is produced and used as a main mold ,
3. The mold manufacturing method according to claim 1 or 2, characterized in that: The mold having an outer surface formed by the surface forming the casting is produced to form a core .
3. The mold manufacturing method according to claim 1 or 2 , characterized in that: Through a procedure of drying the mold in an atmosphere of 40 degrees to 150 degrees ,
5. The mold manufacturing method according to any one of claims 1 to 4, characterized in that:

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