JP5588625B2 - Casting mold, sand mold manufacturing method using the same, and resin molded body molded by molding mold molded from the sand mold - Google Patents

Description

  The present invention is used for molding a resin molded body made of a thermoplastic resin, and more specifically, a casting master mold capable of forming a concavo-convex pattern on the surface of a resin molded body, and a method for producing a sand mold using the same In addition, the present invention relates to a resin molded body formed from a molding die formed from the sand mold, and is particularly suitable for a foamed resin molded body.

  Foamed resin molded body made of thermoplastic resin such as polystyrene, polyethylene, polypropylene, etc. is composed of a lower mold for molding, and an upper mold for molding mold that can move in the mold closing / opening direction with respect to the lower mold Using a molding die that molds a molding space that matches the shape of the desired foamed resin molding when the mold is closed, and fills the molding space with foamed resin particles of thermoplastic resin, The foamed resin particles are produced by foaming and fusing the foamed resin particles by heating the foamed resin particles in the molding space with a heating medium.

  However, it is pointed out that a turtle shell pattern of the foamed resin particles is formed on the surface of the foamed resin molded body produced by foaming and fusing the foamed resin particles, which impairs the appearance of the foamed resin molded body. For this reason, a molding die having an uneven pattern is widely used. The molding die has a concavo-convex pattern formed on the molding surface, and the concavo-convex pattern is formed on the surface by transferring the concavo-convex pattern onto the surface of the foam molded body, and the turtle shell pattern of the foamed resin particles is formed. It is possible to produce a foamed resin molded article having an appearance that is not conspicuous.

  Conventionally, such a molding die manufacturing method has been disclosed, for example, as disclosed in Patent Document 1, on the surface of a casting master (hereinafter simply referred to as “original”), such as a metal mesh or punching metal. There is known a method of attaching a pattern forming member, forming a sand mold having a concavo-convex pattern transferred from the original mold, and further casting a molding die having a concavo-convex pattern transferred from the sand mold.

Registered Utility Model No. 3045015

  However, as shown in FIG. 8, the prototype 51 having a discontinuous surface or an arc surface on the entire surface or a part of the surface is difficult to attach to the entire surface because the concavo-convex pattern forming member is hard. That is, conventionally, as shown in FIGS. 4A and 4B, the concavo-convex pattern forming member can be attached only to the plane portion, and as a result, as shown in FIG. The resin molded body 53 molded from a molding die molded using a mold has a concavo-convex pattern formed only on a flat surface portion, and a concavo-convex pattern is not formed on a discontinuous surface portion or an arc surface portion. It was not able to raise.

  Therefore, in view of such circumstances, the present invention is formed from a casting mold capable of forming a concavo-convex pattern on a discontinuous surface portion or an arc surface portion, a sand mold manufacturing method using the same, and a sand mold. Another object of the present invention is to provide a resin molded body molded by a molding die.

The casting master according to the present invention is used for molding a sand mold of a molding mold for molding a resin molded body made of a thermoplastic resin, and forms a concavo-convex pattern on the entire or part of the molding surface of the sand mold. Therefore, in the casting mold in which the concavo-convex pattern forming member is attached to the entire surface or a part of the surface, the concavo-convex pattern forming member is a laminate made of a material having elasticity and flexibility, and the shore of the upper layer portion having the concavo-convex shape. a hardness is configured higher than the Shore a hardness of the lower portion, the lower portion and wherein the fit these in contact with the surface of the prototype for the casting.

  According to such a configuration, it is possible to easily attach to the surface by flexibly deforming the concavo-convex pattern molded member made of a material having elasticity and flexibility in accordance with the surface shape of the casting prototype. Even if it includes a discontinuous surface portion or an arc surface portion, it can be easily attached. Therefore, it is possible to form a concavo-convex pattern on the molding surface of a sand mold molded using such a casting mold, and on the molding surface of a molding mold molded using the sand mold. A concavo-convex pattern can be formed on the surface of the molded body, and the design can be improved.

Further , according to such a configuration, the concavo-convex pattern forming member has a concavo-convex shape, that is, provided with a plurality of concave portions or convex portions, and the front surface and the back surface are not penetrated, and the casting prototype is formed. Even if the back surface of the concavo-convex pattern forming member is coated with an adhesive or the like, the adhesive or the like does not block the concave portion formed on the surface or the concave portion formed by the convex portion and the convex portion. Moreover, if the surface of the concavo-convex pattern forming member has at least a concavo-convex shape, and further has a concavo-convex shape on the back side, if both the front and back sides do not penetrate, an adhesive applied to the back side, etc. However, it does not block the concave portion on the surface or the concave portion formed by the convex portion and the convex portion, and the adhesion force to the casting mold can be further increased. Therefore, a sand mold formed using such a casting master can be formed without lacking uneven shapes. Therefore, it is possible to form a concavo-convex pattern on the molding surface of a sand mold molded using such a casting mold, and on the molding surface of a molding mold molded using the sand mold. A concavo-convex pattern can be formed on the surface of the molded body, and the design can be improved.

The sand mold manufacturing method using the casting master according to the present invention is used for molding a molding die for molding a resin molded body made of a thermoplastic resin, and the molding surface of the molding die is used. A casting mold having a concavo-convex pattern on the entire surface or a part of the molding surface in order to form a concavo-convex pattern on the entire surface or a part of the molding surface, wherein the concavo-convex pattern forming member is attached to the entire surface or part of the surface. In the sand mold forming method using the above, the uneven pattern forming member is a laminate made of a material having elasticity and flexibility, and the Shore A hardness of the upper layer portion having the uneven shape is higher than the Shore A hardness of the lower layer portion. A sand mold having a concavo-convex pattern is formed on the entire molding surface or a part of the molding surface by using a casting prototype in which the lower layer portion is attached in contact with the surface of the casting prototype.

  According to such a configuration, it is possible to easily attach to the surface by flexibly deforming the concavo-convex pattern molded member made of a material having elasticity and flexibility in accordance with the surface shape of the casting prototype. Even if it includes a discontinuous surface portion or an arc surface portion, it can be easily attached, and an uneven pattern can be formed on the molding surface of the sand mold formed using the casting master. Therefore, a concavo-convex pattern can be formed on the molding surface of a molding die molded using such a sand mold, and as a result, a concavo-convex pattern can be formed on the surface of the resin molded body. Can be increased.

  In addition, the method for producing a sand mold using the casting prototype according to the present invention is a method of casting sand in a state in which a synthetic resin film is disposed on the concave / convex pattern forming member with respect to the casting prototype attached with the concave / convex pattern forming member. It is preferable to form a sand mold by compression.

  According to this configuration, the synthetic resin film is disposed on the concavo-convex pattern forming member, and the sand mold is formed by compressing the cast sand to the casting mold to which the concavo-convex pattern forming member and the synthetic resin film are attached. On the molding surface, a smooth concavo-convex pattern with convex and concave corners can be formed, and as a result, a smooth concavo-convex pattern can be formed on the surface of the resin molded body, resulting in more design. Can be increased.

  According to such a configuration, it is possible to easily attach to the surface by flexibly deforming the concavo-convex pattern molded member made of a material having elasticity and flexibility in accordance with the surface shape of the casting prototype. Even if it includes a discontinuous surface portion or an arc surface portion, it can be easily attached. And it is possible to form a concavo-convex pattern on the molding surface of a sand mold to be molded using such a casting mold, and to form a concavo-convex pattern on the molding surface of a molding die to be molded using the sand mold, and as a result In addition, a concavo-convex pattern can be formed on the surface of the resin molded body, and the design can be further improved.

  As described above, according to the casting master and the sand mold manufacturing method using the same according to the present invention, and the resin molded body molded by the molding die molded from the sand mold, the discontinuous surface portion and the arc Even in the surface portion, there is an excellent effect that an uneven pattern can be formed.

It is sectional drawing of the wooden type | mold which concerns on this embodiment, (a) is a lower type | mold of a convex wooden type | mold, (b) shows an upper type | mold of a convex wooden type | mold, (c) shows a concave wooden type | mold. . The manufacturing process of the lower mold | type of the convex sand mold which concerns on this embodiment is shown. The manufacturing process of the upper mold | type of the convex sand mold which concerns on this embodiment is shown. A manufacturing process for completing the convex sand mold by combining the lower mold and the upper mold of the convex sand mold according to the present embodiment will be described. The manufacturing process of the concave sand mold concerning this embodiment is shown. (A) shows the molding die shape | molded using the wooden mold | type, (b) shows the foaming molding shape | molded using this shaping | molding die regarding this embodiment. The manufacturing process of the lower mold | type of the convex sand mold which concerns on other embodiment is shown. With respect to the prior art, (a) and (b) show a prototype to which a concavo-convex pattern molding member is attached, and (c) shows a resin molded product molded from a molding die molded using the prototype.

  Hereinafter, an embodiment of a casting prototype according to the present invention will be described with reference to the drawings. Note that the casting prototype according to the present embodiment will be described by taking a wooden mold produced by machining wood using an appropriate cutting tool. In the present embodiment, an example in which the foamed resin molded body 4 shown in FIG. 6B is molded will be described. A molding die 3 for molding the foamed resin molded body 4 shown in FIG. 6A includes a convex molding die (hereinafter referred to as “convex die”) 3a, and a concave mold. And a molding die (hereinafter referred to as “concave die”) 3b.

  First, a wooden pattern will be described with reference to FIG. The wooden mold includes convex wooden molds 1a and 1b for forming the convex metallic mold 3a and a concave wooden mold 1c for molding the concave metallic mold 3b. The convex wooden molds 1a and 1b have a lower mold 1a and an upper mold 1b, and the lower mold 1a has a wooden main body 11a having a surface A having a shape corresponding to the molding surface of the convex mold 3a. And a concavo-convex pattern forming member 12 attached to the surface A. The concave wooden mold 1c includes a wooden main body 11c having a surface B having a shape corresponding to the molding surface of the concave mold 3b, and a concavo-convex pattern molding member 12 attached to the surface B.

  The concavo-convex pattern forming member 12 used here is made of a material having elasticity and flexibility. In this embodiment, the concavo-convex pattern forming member 12 is made of an elastomeric polymer material and is more easily shaped than a synthetic resin. Can be transformed. Then, it is a convex shape such as the surface A of the lower mold 1a of the convex wooden mold (see (a) of the figure), or a concave shape such as the surface B of the concave wooden mold 1c (see (c) of the same figure). It can be easily attached to the wooden mold. The elastomeric polymer material is, for example, a thermosetting elastomer and a thermoplastic elastomer. The thermosetting elastomer is so-called rubber, and the thermoplastic elastomer has properties of rubber at normal temperature and can be melted at high temperature, so that it can be easily molded.

  Further, the concavo-convex pattern forming member 12 is a sheet-like body having at least a concavo-convex shape on the surface side, that is, a sheet-like body having a plurality of convex portions 13 with a uniform spacing on the surface side. Therefore, even if the front surface and the back surface are not penetrated and the adhesive is applied to the back surface for attaching to the wooden mold, the adhesive blocks the concave portion formed by the convex portion 13 and the convex portion 13 on the front surface. There is no such thing. Further, the convex portions 13 have such a size that the turtle shell pattern on the surface of the foamed resin molded body 4 formed by heating and foaming the foamed resin particles is inconspicuous, or have a space between the convex portions 13. To. Moreover, the convex part 13 is a cylindrical shape whose top part is substantially circular.

  Next, a method for manufacturing a molding die for molding the foam molded body according to the present embodiment will be described with reference to FIGS. First, the manufacturing method of the convex mold 3a will be described with reference to FIGS. The convex mold 3a is molded by molding the convex sand mold 2a using the convex wooden molds 1a and 1b, and further using the convex sand mold 2a. And the manufacturing method of this convex sand mold 2a is manufactured by shape | molding the convex sand mold 2a using the wooden molds 1a and 1b by which the uneven | corrugated pattern shaping | molding member 12 was attached to the surface A which shape | molds the convex sand mold 2a. The In order to form the convex sand mold 2a, it is necessary to further mold the lower mold 20a and the upper molds 20b and 20c.

  First, a manufacturing process for forming the lower mold 20a of the convex sand mold will be described. As shown in FIG. 2 (a), the concavo-convex pattern forming member 12 is cut into a shape corresponding to the surface A of the lower mold 1a of the convex wooden mold, stretched along the surface A, and attached with an adhesive or the like. . Here, the concavo-convex pattern forming member 12 made of an elastomer material does not need to be attached while avoiding the non-planar portion of the surface A as in the prior art, and the concavo-convex pattern forming member 12 can be easily attached.

  Next, as shown in FIG. 4B, the lower mold 1a is placed on the base 21, and the periphery of the lower mold 1a is positioned so that the lower mold 1a is located at the center (hereinafter simply referred to as “frame body”). ”And a casting sand 23 so as to embed the lower mold 1 a in the frame body 22. Next, the casting sand 23 filled in the frame body 22 is hardened to the shape by sealing with carbon dioxide gas. Thereafter, as shown in FIG. 2 (c), the lower body 1a is removed by reversing the frame body 22, thereby forming the lower mold 20a of the convex sand mold having the cavity 24 that matches the inverted shape of the lower mold 1a. To do. As a result, the concavo-convex pattern transferred from the concavo-convex pattern forming member 12 is formed on the molding surface C of the convex sand mold lower mold 20a facing the surface A of the convex mold-shaped lower mold 1a.

  Next, the process of molding the convex sand mold upper mold 20c will be described. In addition, as shown in FIG.1 (b), since the upper mold | type 1b of a convex type | mold wooden mold is not equipped with the shaping | molding surface for shape | molding a convex mold, the attachment of the uneven | corrugated pattern shaping | molding member 12 is abbreviate | omitted, The steps similar to those of the lower mold 20a of the convex sand mold are performed as shown in FIGS. However, when the convex sand mold upper mold 20c is combined with the convex sand mold lower mold 20a, it communicates with a gate for pouring molten metal into the cavity 24 of the convex sand mold lower mold 20a. A gate 25 is provided. Then, as shown in FIG. 4A, the convex sand mold 2a is formed by combining the lower mold 20a and the upper mold 20c of the convex sand mold.

  And the convex metal mold | die 3a is shape | molded by casting using the convex sand mold 2a. That is, as shown in FIG. 4 (a), the lower mold 20a of the convex sand mold is combined on the lower side and the upper mold 20c of the convex sand mold is combined on the upper side, and the molten metal is fed from the gate at the tip of the gate rod 25 of the upper mold 20c. Is cast into the cavity 24, and the molten metal is solidified to cast the convex mold 3a. Thereby, the concavo-convex pattern transferred from the convex sand mold 2a is molded on the molding surface D of the convex mold 3a facing the molding surface C of the convex sand mold 2a. Although not shown, the convex mold 3a is formed with a steam hole for introducing steam for heating the foamed resin particles by steam when the foamed molded body is molded.

  Next, a method for manufacturing the concave mold 3b will be described with reference to FIG. The concave mold 3b is formed by forming a concave sand mold 2b using the concave wooden mold 1c and further using the concave sand mold 2b. The method for manufacturing the concave sand mold 2b is performed in the same manner as the method for manufacturing the convex sand mold 2a. As shown in FIG. Using the concave wooden mold 1c to which the member 12 is attached, the concave sand mold 2b is molded as shown in FIGS.

  Thus, the convex mold 3a and the concave mold 3b as shown in FIG. 6A are manufactured, and the convex mold 3a and the concave mold 3b are fitted and clamped to form both molds 3a. , 3b is filled with foamed resin particles, and the foamed resin molded body 4 is molded by heating and foaming the foamed resin particles with a heating medium such as water vapor, thereby forming the foamed resin molding 4 Concave and convex patterns are formed on the surface of the body 4 from both molds 3a and 3b. Specifically, a plurality of substantially circular shapes, which are the shapes of the tops of the convex portions 13, are uniformly transferred. And the foaming resin molding 4 with the favorable external appearance which does not make the turtle shell pattern of foaming resin particle conspicuous can be manufactured, or effects, such as a flaw concealment and noise prevention, can also be acquired.

  In addition, the wooden molds 1a and 1c according to the present embodiment can easily attach the concavo-convex pattern forming member 12 to the surfaces A and B that are convex or concave, and the surfaces A and B By attaching the concave / convex pattern forming member 12 to B, the concave / convex pattern can be formed on the sand molds 2a, 2b and the molding dies 3a, 3b formed using the wooden molds 1a, 1b, 1c. A concavo-convex pattern can be formed on the surface of the foamed resin molded body 4 molded using the molding dies 3a and 3b.

  Further, in the concavo-convex pattern forming member 12 according to the present embodiment, since the front surface and the back surface do not penetrate like the conventional metal mesh or punching metal, the adhesive applied to the back surface is different from the surface side convex portion 13. The sand mold formed using this wooden mold does not block the concave portion formed by the convex portion 13, the concave and convex pattern is not lost, and the pattern having the substantially circular convex portion is uniformly transferred. can do.

  The casting mold according to the present invention, the method for producing a sand mold using the same, and the resin molded body molded by the molding mold molded from the sand mold are not limited to the above embodiment. Of course, various modifications can be made without departing from the scope of the present invention.

  For example, in the wooden molds 1a and 1c according to the above-described embodiment, the example in which the uneven pattern forming member 12 is attached to the surfaces A and B has been described. However, the present invention is not limited to this, and the uneven pattern is smoothly formed. Further, a synthetic resin film may be further attached.

  Here, a wooden mold according to another embodiment of the above-described embodiment will be described with reference to FIG. 7, taking as an example a convex sand mold lower mold 20a 'that is molded using the convex wooden mold 1a'. In addition, about the part similar to the said embodiment, description is abbreviate | omitted using the same code | symbol.

  First, a lower mold 1a ′ of a convex wooden mold according to another embodiment has a concavo-convex pattern forming member 12 attached to the surface A and further covers the concavo-convex pattern forming member 12, as shown in FIG. Thus, the synthetic resin film 14 is attached. Examples of the synthetic resin film 14 include resins such as polyethylene, polypropylene, polyvinyl chloride, and polyester, or copolymers of these resins. Moreover, it is preferable to shape | mold the synthetic resin film 14 as thinly as possible from a viewpoint of making it deform | transform along the uneven | corrugated pattern shaping | molding member 12. FIG.

  And the manufacturing method of the convex sand type | mold lower mold | type 20a 'shape | molded using this convex type | mold wooden lower mold | type 1a' is similar to the said embodiment, as shown to the same figure (b) and (c). The convex sand mold lower mold 1a ′ having the concave and convex pattern forming member 12 and the synthetic resin film 14 attached to the surface thereof is compressed into the cast sand 23 to form the convex sand mold lower mold 20a ′. Thereby, the casting sand 23 presses the portion facing the concave portion between the convex portion 13 and the convex portion 13 of the lower mold 1a ′ of the convex wooden mold, and the synthetic resin film 14 toward the bottom of the concave portion. Therefore, the uneven shape formed on the forming surface A of the lower mold 20a ′ of the convex sand mold can be a smooth undulation. Similarly, when the upper mold, the convex sand mold, and the concave sand mold are molded, and the molding dies 3a ′ and 3b ′ are molded using these molds as shown in FIG. A smooth uneven shape can be formed.

  In the casting mold master according to the above embodiment, the wood molds 1a, 1b, and 1c whose material is wood have been described as examples. However, the present invention is not limited thereto, and the material is clay, foamed polystyrene, foamed urethane, It may be a casting prototype such as a synthetic resin.

  Further, in the concavo-convex pattern forming member 12 according to the above embodiment, an example of an elastomer material has been described, but the present invention is not limited thereto, and may be a thermoplastic resin such as polyolefin and polyurethane, that is, Any material having elasticity and flexibility may be used. Furthermore, it is preferable that the Shore A hardness is 90 or less. Most preferably, it is 30 or less. The Shore A hardness is measured by a method of measuring the durometer A hardness of JIS K7215 plastic.

  Moreover, in the uneven | corrugated pattern shaping | molding member 12 which concerns on the said embodiment, although the example which is a sheet-like body was demonstrated, it is not limited to this, A fibrous body and the member which has a sheet form or a fiber form are laminated | stacked It may be a laminated body.

  In particular, when the concavo-convex pattern forming member is a laminate, it is preferable that the Shore A hardness of the upper layer portion is higher than the Shore A hardness of the lower layer portion. For example, in the case of attaching a laminate in which two or more layers are laminated on a convex arcuate surface, the lower layer part (the part in contact with the arcuate surface) of the laminate is pulled or compressed to follow the arcuate surface. However, while it can be attached along the arc surface by being deformed flexibly, the upper layer part (the part including the convex part) of the laminate can be kept in the concave and convex shape, Since there is no distortion, the concavo-convex pattern can be made homogeneous.

  In the concavo-convex pattern forming member 12 according to the above-described embodiment, the example having the concavo-convex shape on the front surface side has been described. However, the present invention is not limited to this, and the back surface side does not interfere with the concavo-convex shape on the front surface side. You may have uneven | corrugated shape. That is, even if it has an uneven shape on the back surface, the adhesive applied to the back surface is not recessed, or the convex portion and the convex portion, so that the front surface and the back surface do not interfere with each other. Without clogging the concave portion formed by the surface, and without forming an unnecessary concave portion on the resin molded body by the raised convex portion due to the leakage of the adhesive from the back surface to the front surface side, and a casting prototype It can also increase the adhesive strength. And the uneven | corrugated shape which has in a back surface does not need to be the same as the uneven | corrugated shape which it has on the surface side, and may be a notch into which an adhesive agent can enter.

  Moreover, in the uneven | corrugated pattern shaping | molding member 12 which concerns on the said embodiment, although the example attached to the surfaces A and B of the wooden molds 1a and 1c using an adhesive agent was demonstrated, it is not limited to this, A concavo-convex pattern shaping | molding It may be attached to the casting mold with an adhesive tape that has been affixed to the back surface of the member in advance.

  In the concavo-convex pattern forming member 12 according to the above-described embodiment, an example is described in which a plurality of convex portions 13 having a substantially circular top shape are provided on one surface in order to form the concavo-convex pattern. Instead, it may be a concavo-convex pattern forming member having a plurality of concave portions having a substantially circular bottom shape on one surface, and by doing so, it is possible to prevent the concavo-convex pattern from being lost. And the pattern which has a substantially circular hollow is transferred uniformly. In addition, even if the uneven | corrugated pattern shaping | molding member 12 is provided with a through-hole instead of the convex part 13, it does not receive a restriction | limiting in the attachment to the non-planar part of the uneven | corrugated pattern shaping | molding member 12.

  Moreover, in the molding method of the sand molds 2a, 2b according to the above embodiment, the example in which the molding sand 23 is compressed by the wooden molds 1a, 1b, 1c has been described. However, the present invention is not limited to this. The upper surface of the body 22 and the casting sand 23 are covered with a non-breathable synthetic resin sheet, and connected to a suction device, for example, a vacuum pump, and filled into the frame body 22 from a suction port provided in the frame body 22. Then, air may be sucked in vacuum from the casting sand 23 sandwiched between the base 61 and the synthetic resin sheet, and the casting sand 23 may be hardened into that shape.

  Moreover, in the wooden molds 1a and 1c according to the above-described embodiment, the example in which the concavo-convex pattern molding member or the synthetic resin film 14 is attached to the entire surfaces A and B has been described, but the present invention is not limited thereto. The concave / convex pattern forming member or the synthetic resin film 15 may be attached to a part of the surfaces A and B.

  Moreover, although the resin molded body which concerns on the said embodiment demonstrated the foamed resin molded product to the example, it is not limited to this, Other resin molded bodies can be selected freely.

  1a, 1a '... convex wooden mold (lower mold), 1b ... convex wooden mold (upper mold), 1c ... concave wooden mold, 11a ... wooden main body, 11b ... wooden main body, 11c ... wooden main body, 12 ... concave-convex pattern forming member, 13 ... convex part, 14 ... synthetic resin film, 2a ... convex sand mold, 2b ... concave sand mold, 20a, 20a '... convex sand mold (lower mold), 20b, 20c ... convex sand mold (upper Mold), 21 ... base, 22 ... sand mold preparation frame (frame body), 23 ... cast sand, 24 ... cavity, 25 ... pouring bar, 3 ... molding mold, 3a ... convex mold (Convex mold), 3b ... concave mold (concave mold), 31 ... molding space, 4 ... foamed molded product (resin molded product), 51 ... casting mold, 52 ... punching metal, 53 ... resin Molded body, A, B ... molding surface, C, D ... molding surface

Claims (3)

Used to form a sand mold of a molding die for molding a resin molded body made of a thermoplastic resin. In order to form an uneven pattern on the entire surface or part of the molding surface of the sand mold, the entire surface or part of the surface is formed. In the casting prototype to which the uneven pattern forming member is attached,
The concavo-convex pattern forming member is a laminate composed of a material having elasticity and flexibility, and is configured such that the shore A hardness of the upper layer portion having the concavo-convex shape is higher than the shore A hardness of the lower layer portion, and the lower layer portion is the casting A casting prototype characterized by being attached in contact with the surface of the prototype. It is used for molding a molding die for molding a resin molded body made of a thermoplastic resin. In order to form an uneven pattern on the entire molding surface or part of the molding die, the entire molding surface or part of the molding surface is used. In a sand mold forming method using a casting prototype in which a concavo-convex pattern molding member is attached to the entire surface or part of the surface, the sand mold forming method having a concavo-convex pattern in the part,
The concavo-convex pattern forming member is a laminate made of a material having elasticity and flexibility, and is configured such that the shore A hardness of the upper layer portion having the concavo-convex shape is higher than the shore A hardness of the lower layer portion, and the lower layer portion is A sand mold forming method, wherein a sand mold having a concavo-convex pattern is formed on the entire surface or a part of a molding surface using a casting mold attached in contact with the surface of the casting mold. 3. The sand mold forming method according to claim 2, wherein the sand mold is formed by compressing the cast sand in a state where the synthetic resin film is disposed on the uneven pattern forming member with respect to the casting mold to which the uneven pattern forming member is attached.

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