Method for reclaiming foundry sand, method for manufacturing foundry sand, and method for manufacturing sand molds

Abstract

To provide a regeneration method of casting sand capable of realizing the regeneration of casting sand different in properties in practical operation.SOLUTION: A regeneration method of casting sand performs: a resin kneading step 5 of obtaining predetermined resin-kneaded sand 20 by kneading a predetermined amount of predetermined resin 19 for kneaded sand 14 (uncured sand 18) to which no resin 15 has been adhered in forming a sand mold 16 at first; a crushing step 6 of obtaining a crushed matter 21 by crushing each of the predetermined resin-kneaded sand 20 obtained in the resin kneading step 5 and the kneaded sand 14 (resin cured sand 17) to which the resin 15 has been adhered in forming the sand mold 16; and a calcining / regenerating step 8 of producing regeneration sand 12 by calcining the crushed matter 21 obtained in the crushing step 6.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for reclaiming foundry sand, a method for producing foundry sand, and a method for producing a sand mold. [Background technology]

[0002] Casting methods using sand molds made from foundry sand are widely used as a manufacturing method for castings. The foundry sand used for molding such sand molds is specially processed to take into account moldability, etc., and is therefore expensive. For this reason, attempts have been made to recycle the foundry sand used in the sand mold manufacturing process. One known technique for recycling foundry sand is described in Patent Document 1. Patent Document 1 describes a method for recycling foundry sand used to form a mold for shell mold casting by roasting to remove resin adhering to the sand. In the shell mold casting method described in Patent Document 1, all of the foundry sand collected for recycling has resin adhering to it. Therefore, when roasting to remove the resin and recycling the sand, even combustion is possible, and recycled sand with uniform properties can be obtained relatively easily. Meanwhile, in recent years, additive manufacturing has come into use as a method capable of molding sand molds with more complex shapes. In particular, inkjet additive manufacturing has attracted attention as a method capable of molding large sand molds in a short period of time. Inkjet additive manufacturing is a method of molding a sand mold by layering mixed sand, which is made by kneading foundry sand with a hardener, which is a catalyst for hardening the resin, one layer at a time, and printing resin on each layer from an inkjet nozzle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-314080 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when attempting to recycle foundry sand used in inkjet-based additive manufacturing, the following problem arose: The foundry sand collected for recycling includes not only resin-hardened sand, where the resin used in the sand mold has hardened and adhered to its surface, but also unhardened sand, where only the hardener remains. When attempting to recycle foundry sand with such different properties, uneven combustion occurs due to the properties of the foundry sand, making it difficult to obtain uniform recycled sand. Therefore, in inkjet-type additive manufacturing, it has been difficult to recover and recycle casting sand with different properties in actual operations.

[0005] An object of the present invention is to provide a method for reclaiming foundry sand, a method for manufacturing foundry sand, and a method for manufacturing a sand mold, which are capable of reclaiming foundry sand of different properties in actual operation. [Means for solving the problem]

[0006] One aspect of the foundry sand recycling method of the present invention is (a) a method for recycling foundry sand used in an inkjet-type additive manufacturing method in which a resin is printed onto mixed sand, which is made by mixing foundry sand with a hardener that hardens the resin, to form a sand mold, and the method comprises: (b) a resin mixing step in which a predetermined amount of a predetermined resin is mixed with mixed sand to which no resin adhered during molding of the sand mold to obtain a predetermined resin mixed sand; (c) a crushing step in which the predetermined resin mixed sand obtained in the resin mixing step and the mixed sand to which resin adhered during molding of the sand mold are crushed to obtain crushed material; and (d) a roasting and recycling step in which the crushed material obtained in the crushing step is roasted to produce recycled sand.

[0007] One aspect of the method for manufacturing a sand mold of the present invention is (a) a method for manufacturing a sand mold using an inkjet-type additive manufacturing method, in which a resin is printed onto mixed sand obtained by kneading foundry sand with a hardener that hardens the resin, to form a sand mold, and (b) in the step of kneading the hardener and foundry sand, foundry sand for casting is used as the foundry sand, which is obtained by mixing new sand with a predetermined amount of recycled sand obtained by the above-mentioned recycling method. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram showing a molding cycle in the method for manufacturing a sand mold according to the first embodiment. [Figure 2] FIG. 2 is a diagram showing a schematic configuration of a fluidized roasting furnace used in the roasting regeneration process. [Figure 3] FIG. 1 shows the results of calorimetry by TG-DTA analysis of resin-cured sand and uncured sand. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present inventors have discovered the following problems in recycling foundry sand of different properties (resin-hardened sand, unhardened sand) collected by inkjet-type additive manufacturing. Resin-hardened sand, which has the resin used as a sand mold hardened and attached to its surface, and unhardened sand, which has only the hardener attached, are originally the same molding sand, but the substances attached to the surface (resin + hardener, hardener only) are different, so their behavior when heated is significantly different, as shown in Figure 3. Figure 3 shows the results of calorimetry measurements of resin-hardened sand and unhardened sand using TG-DTA analysis. Furan resin and phenolic resin were used as resins. The chemical addition conditions were 0.2 parts by weight of hardener and 2.0 parts by weight of resin per 100 parts by weight of molding sand, which are concentrations commonly used in additive manufacturing. Figure 3 shows that unhardened sand has a lower calorific value than resin-hardened sand. Specifically, resin-cured sand generates heat only when the attached resin burns. Uncured sand, like resin-cured sand, generates heat from the combustion of attached materials (e.g., the hardener) at temperatures around 400–600°C, but also absorbs heat at lower temperatures due to the evaporation of large amounts of attached solvents (e.g., solvents contained in the hardener). Therefore, if all of these sands (resin-cured sand and uncured sand) are roasted simultaneously as in conventional regeneration processes in order to reuse them as foundry sand, uneven conditions arise in the combustion chamber due to differences in roasting behavior, making it difficult to obtain homogeneous recycled sand. The difference in the calorific value of the "uncured sand" on the right and left sides of Figure 3 is due to the different types of hardeners used.

[0010] Hereinafter, examples of a method for reclaiming foundry sand, a method for producing foundry sand, and a method for producing a sand mold according to embodiments of the present invention will be described with reference to Figures 1 to 3. Note that the present invention is not limited to the following examples. Furthermore, the effects described in this specification are merely examples and are not limiting, and other effects may also be obtained. A method for manufacturing a sand mold according to a first embodiment of the present invention will now be described. Fig. 1 is a diagram showing the molding cycle in the method for manufacturing a sand mold according to the first embodiment. The method for manufacturing a sand mold shown in Fig. 1 is an inkjet-type additive manufacturing method in which an inkjet head nozzle is used to print resin onto mixed sand, which is made by kneading foundry sand with a curing agent that hardens the resin, to form a sand mold. As shown in Figure 1, the sand mold manufacturing method (inkjet-type additive manufacturing method) has a manufacturing cycle including a kneading process 1, a molding process 2, a casting process 3, a mold and sand recovery process 4, a resin kneading process 5, a roasting and recycling process 8, and a foundry sand manufacturing process 9.

[0011] In the kneading step 1, foundry sand 10 and a hardener 13 are kneaded to produce mixed sand 14. At least a portion of the foundry sand 10 is recycled sand 12 introduced in the roasting and recycling step 8, which will be described later. The raw material for the foundry sand 10 is not particularly limited, and may be, for example, natural sand, artificial sand, or a mixture thereof. Examples of natural sand include natural silica sand and zircon sand. Examples of artificial sand include artificial sand produced by the sintering method, melting method, or flame fusion method. Examples of the composition of artificial sand that can be used include a mixture of alumina (Al-O-based), mullite (Al-Si-O-based), and mullite-zircon (Al-Si-Zr-O-based).

[0012] The curing agent 13 is not particularly limited as long as it acts as a catalyst for curing the resin 15 (binder) printed on the mixed sand 14 in the molding process 2. When an organic resin such as a furan resin or a phenol resin is used as the resin 15, the curing agent 13 is preferably one that can cure the organic resin at room temperature. For example, curing agents whose main components are xylene sulfonic acid or toluene sulfonic acid may be used. The mixing ratio of the curing agent 13 with respect to the total mass of the foundry sand 10 is preferably in the range of 0.01 to 1.0% by mass.

[0013] In the molding process 2, an inkjet-type additive manufacturing method is used to build a sand mold 16 by layering mixed sand 14 one layer at a time and printing resin 15 on each layer. For example, using an inkjet-type three-dimensional additive manufacturing device 100, a thin layer of mixed sand 14, made by mixing foundry sand 10 and hardener 13, is first uniformly spread on a flat surface using a blade mechanism. Next, an inkjet nozzle head is scanned to print resin 15 on predetermined areas of this thin layer based on data obtained by designing the shape of the sand mold 16 using 3D CAD. The layer in the printed area with resin 15 is bonded and also bonds with the previously formed lower layer. The process of forming thin layers on top and printing resin 15 is then repeated until the entire sand mold 16 is completed with the layer in the printed area with resin 15. Finally, the area without resin 15 remains unbonded and can be easily removed from the sand mold 16. By the above operations, the three-dimensional additive manufacturing device 100 can be used to manufacture a sand mold 16 having a desired three-dimensional structure. As the resin 15, for example, an organic resin can be used. In particular, it is preferable to use a furan resin or a phenol resin. Examples of the furan resin include a furan resin made of one or more selected from the group consisting of furfuryl alcohol, a condensate of furfuryl alcohol and an aldehyde, and a condensate of urea and an aldehyde, or a condensate of two or more selected from the above group. Examples of the phenol resin include a condensate of a phenol and an aldehyde.

[0014] Furthermore, in molding step 2, when the hardened sand mold 16 is removed from the mixed sand 14, the mixed sand 14 on which the resin 15 is not printed and the mixed sand 14 adhering to the sand mold 16 are separately collected. The "mixed sand 14 on which the resin 15 is not printed" is the "mixed sand 14 on which the resin 15 was not printed when the sand mold 16 was molded," which will be described later. The "mixed sand 14 adhering to the sand mold 16" is the "mixed sand 14 to which the resin 15 was attached when the sand mold 16 was molded but which does not constitute the sand mold 16," which will be described later. These mixed sands 14 are preferably collected using a suction device. In the casting process 3, casting is performed using the sand mold 16 formed in the molding process 2 to obtain a casting. In the mold and sand recovery process 4, the mixed sand 14 to which the resin 15 adhered during molding of the sand mold 16 (hereinafter also referred to as "resin-hardened sand 17") is recovered. Examples of the resin-hardened sand 17 include at least one of the sand mold 16 used for casting and the mixed sand 14 to which the resin 15 adhered during molding of the sand mold 16 but which did not constitute the sand mold 16. Examples of the "sand mold 16 used for casting" include fragments of the sand mold 16 that were broken to remove the casting. Examples of the "mixed sand 14 to which the resin 15 adhered during molding of the sand mold 16 but which did not constitute the sand mold 16" include the mixed sand 14 that adhered to the sand mold 16 when the sand mold 16 was removed from the mixed sand 14. The recovery of the mixed sand 14 that adhered to the sand mold 16 is performed in the molding process 2.

[0015] In the resin mixing step 5, a predetermined amount of predetermined resin 19 is mixed with mixed sand 14 (hereinafter also referred to as "uncured sand 18") to which resin 15 did not adhere during molding of the sand mold 16, to obtain predetermined resin-mixed sand 20. Examples of uncured sand 18 include mixed sand 14 to which resin 15 was not printed during molding of the sand mold 16, and / or sand spilled during mixing (e.g., mixed sand 14 not used to mold the sand mold 16, contaminated foundry sand 10). Examples of "mixed sand 14 not used to mold the sand mold 16" and "contaminated foundry sand 10" include sand generated due to malfunctions or maintenance of the 3D additive manufacturing device 100. The predetermined resin 19 is preferably the same as the resin 15 used in the 3D additive manufacturing device 100, and an organic resin, particularly a furan resin or a phenolic resin, is preferred. The furan resin or phenol resin may be the same as the furan resin or phenol resin listed above for Resin 15. The kneading machine may be either a continuous or batch type, as long as it is one typically used for organic self-hardening binders. For example, an Eirich Mixer manufactured by Nippon Eirich Co., Ltd. may be used. The mixing ratio of the specified resin 19 is 0.1 to 5.0 parts by weight per 100 parts by weight of unhardened sand 18. This allows the fluidity of the sand to be maintained in subsequent processes, and also allows the amount of resin to be closer to the amount actually printed (the amount of resin in the resin-hardened sand 17).

[0016] In the crushing process 6, the resin-hardened sand 17 recovered in the mold and sand recovery process 4 and the predetermined resin-mixed sand 20 obtained in the resin-mixing process 5 are crushed to obtain crushed material 21. For example, the resin-hardened sand 17 and the predetermined resin-mixed sand 20 are crushed to 3 mm or less using a crusher (jaw crusher, hammer crusher, etc.) and then charged into a pre-roasting raw material tank. This crushing simplifies mixing by crushing the sand mold 16 (resin-hardened sand 17). In the subsequent mixing process 7, the resin-hardened sand 17 and the predetermined resin-mixed sand 20 can be uniformly mixed, resulting in a stable roasting raw material with minimal influence from the ratio of the resin-hardened sand 17 to the predetermined resin-mixed sand 20. Furthermore, in the mixing process 7, the crushed material 21 obtained in the crushing process 6 is uniformly mixed. This allows the properties of the sand to be charged into the fluidized bed roaster 200 (see FIG. 2), which will be described later, to be homogenized. The mixing process 7 is performed in the pre-roasting raw material tank. The ratio of the resin-hardened sand 17 and the unhardened sand 18 contained in the crushed material 21 mixed in the mixing step 7 is not particularly limited, and can be in the range of 0 to 100%.

[0017] In the roasting and regeneration step 8, the crushed material 21 mixed in the mixing step 7 is roasted to produce recycled sand 12. Specifically, it is preferable to regenerate the crushed material 21 by roasting it using a fluidized roasting furnace 200 as shown in FIG. 2. For example, air 201 is blown in from the bottom of a combustion chamber 202 using a blower (not shown), the crushed material 21 is fluidized in the combustion chamber 202, and a flame from a burner 204 is applied to the fluidized crushed material 21 (hereinafter also referred to as the "sand fluidized layer 203"). As a result, the hardener 13, resin 15, and specified resin 19 on the surface are evaporated or burned to produce recycled sand 12. Here, for example, if unhardened sand 18 is charged into the combustion chamber 202 instead of the crushed material 21, the temperature of the sand fluidized bed 203 in the fluidized roasting furnace 200 is maintained mainly by radiant heat from the burner flame. However, due to the structure, the radiant heat is blocked by the low-temperature air 201 flowing in from below, which can cause uneven baking of the unhardened sand 18 and reduce the quality of the recycled sand 12. In contrast, in the first embodiment, resin 15 or predetermined resin 19 is attached to the surface of the sand particles of the crushed material 21, so that each sand particle burns exothermically, preventing uneven burning of the crushed material 21 and resulting in a uniformly recycled recycled sand 12. Furthermore, the exothermic combustion of the sand particles themselves due to resin 15 or predetermined resin 19 leads to weakening of the burner combustion required to maintain the temperature of the sand fluidized bed 203, enabling efficient use of fuel. Furthermore, since the burner combustion can be weakened while maintaining the temperature of the sand fluidized bed 203, the temperature rise inside the combustion chamber 202 can be suppressed.

[0018] The roasting temperature of the crushed material 21 can be, for example, between 300°C and 1000°C. A temperature range of between 300°C and 550°C is particularly preferred. That is, the crushed material 21 is preferably roasted at a roasting temperature between 300°C and 550°C. Here, if the furnace temperature exceeds 550°C, the furnace materials of the fluidized roasting furnace 200 will deteriorate more quickly, and the crushed materials may be mixed into the recycled sand 12. Furthermore, simply lowering the furnace temperature may result in insufficient evaporation or combustion of the hardener 13. In contrast, in the first embodiment, by adhering a predetermined resin 19 to the particle surfaces of the unhardened sand 18, the particles of the unhardened sand 18 are more likely to burn exothermically. This allows the roasting temperature of the crushed material 21 to be higher than the furnace temperature, enabling high-quality recycling while lowering the furnace temperature. The roasting temperature of the crushed material 21 means the temperature of the sand fluidized bed 203 (crushed material 21 ) measured by a thermometer 205 installed in the sand fluidized bed 203 .

[0019] In the foundry sand production process 9, foundry sand 10 is produced by mixing new sand 11 with a predetermined amount of recycled sand 12 recycled in the roasting and recycling process 8. For example, foundry sand 10 obtained by mixing new sand 11 and recycled sand 12 in a predetermined ratio is introduced into the kneading process 1. The mixing ratio of new sand 11 and recycled sand 12 is, for example, 100 parts by weight of new sand 11 to more than 0 parts by weight and not more than 100 parts by weight of recycled sand 12. This allows the quality of the foundry sand 10 to be maintained and eliminates the need to change the settings of the 3D additive manufacturing apparatus 100. Note that in this embodiment, an example is shown in which foundry sand 10 obtained by mixing new sand 11 and recycled sand 12 is introduced into the kneading process 1. However, other configurations may be adopted. For example, the recycled sand 12 may be introduced directly into the kneading process 1 as foundry sand 10 without being mixed with new sand 11. That is, the foundry sand 10 used to form the sand mold 16 may be 100% recycled sand.

[0020] The ratio of resin-hardened sand 17 to unhardened sand 18 varies for each casting. Therefore, for example, if the resin-hardened sand 17 and unhardened sand 18 are simply roasted simultaneously to perform the regeneration process, uneven combustion due to their properties may occur, as shown in Figure 3, and the quality of the regenerated sand 12 may change. Therefore, in order to produce regenerated sand 12 of consistent quality, it is necessary to adjust the firing temperature and firing time for each lot and to roast and regenerate under sufficient conditions, which may increase costs. Furthermore, for example, if resin-hardened sand 17 and unhardened sand 18 are mixed in a certain ratio and roasted to regenerate the sand in order to eliminate uneven combustion caused by such properties, the amount that can be regenerated may be reduced because the ratio of each material generated varies depending on the product. Furthermore, for example, if different roasting conditions are used for reclaiming sand with different properties (resin-hardened sand 17, unhardened sand 18) in order to increase the amount of sand to be reclaimed, it will be necessary to strictly separate the sand after collection, which may be a lot of work. Also, dedicated lines such as storage tanks will be required for each type of sand (resin-hardened sand 17, unhardened sand 18), which may increase the cost of reclaiming. Therefore, in the inkjet-type additive manufacturing method, it has been difficult to recover and recycle molding sand 10 with different properties in actual operation.

[0021] In contrast, in the foundry sand reclamation method according to the first embodiment, a resin mixing step 5 is first performed in which a predetermined amount of predetermined resin 19 is mixed with mixed sand 14 (unhardened sand 18) to which resin 15 did not adhere during molding of the sand mold 16, to obtain predetermined resin-mixed sand 20. Then, a crushing step 6 is performed in which the obtained predetermined resin-mixed sand 20 and the mixed sand 14 (resin-hardened sand 17) to which resin 15 adhered during molding of the sand mold 16 are crushed to obtain crushed material 21. Then, a roasting and regeneration step 8 is performed in which the crushed material 21 obtained by crushing is roasted to produce reclaimed sand 12. As a result, the specified resin 19 is mixed with the unhardened sand 18, and both the resin-hardened sand 17 (sand mold 16) and the specified resin-mixed sand 20 are crushed, which homogenizes the properties of the crushed material 21 (sand) fed into the fluidized roasting furnace 200 and prevents uneven combustion due to the properties. Therefore, there is no need to adjust the firing temperature and firing time for each lot or to roast and regenerate under sufficient conditions, as described above, and homogenous recycled sand 12 can be obtained, preventing cost increases. Furthermore, unlike the case where a mixture of resin-hardened sand 17 and unhardened sand 18 in a certain ratio is roasted and recycled, as described above, the amount of material that can be recycled can be increased. Furthermore, unlike the case described above where the roasting conditions are changed for each type of sand (resin-hardened sand 17, unhardened sand 18) to perform the regeneration process, there is no need to separate the reclaimed sand 12 after collection, and there is no need for dedicated lines such as storage tanks for each type of sand (resin-hardened sand 17, unhardened sand 18). Therefore, according to the foundry sand recycling method of the first embodiment, it is possible to realize recycling of foundry sand 10 with different properties in an inkjet-type additive manufacturing method in actual operation.

[0022] The present invention can also be configured as follows. (1) A method for regenerating foundry sand used in an inkjet-type additive manufacturing method in which a resin is printed onto mixed sand obtained by kneading foundry sand with a hardener that hardens a resin, to form a sand mold, comprising: a resin mixing step of mixing a predetermined amount of a predetermined resin into the mixed sand to which the resin did not adhere during molding of the sand mold, thereby obtaining a predetermined resin mixed sand; a crushing step of crushing the resin-mixed sand obtained in the resin mixing step and the mixed sand to which the resin adhered during molding in the sand mold to obtain a crushed product; a roasting and regeneration step of roasting the crushed material obtained in the crushing step to produce reclaimed sand; A method for regenerating foundry sand. (2) The mixed sand to which the resin did not adhere during molding of the sand mold is at least one of the mixed sand to which the resin was not printed during molding of the sand mold, the mixed sand that was not used for molding the sand mold, and the contaminated foundry sand; The mixed sand to which the resin adhered during molding of the sand mold is at least one of the sand mold used for casting and the mixed sand to which the resin adhered during molding of the sand mold but which does not constitute the sand mold. The method for regenerating foundry sand according to (1) above. (3) The predetermined resin includes at least one of a furan resin and a phenol resin. The method for regenerating foundry sand according to (1) or (2) above. (4) In the resin mixing step, 0.1 to 5.0 parts by weight of the predetermined resin is mixed with 100 parts by weight of unhardened sand, which is the mixed sand to which the resin did not adhere during molding of the sand mold. A method for regenerating foundry sand according to any one of (1) to (3) above. (5) In the roasting and regeneration step, the crushed material is roasted at a roasting temperature of 300°C or higher and 550°C or lower. A method for regenerating foundry sand according to any one of (1) to (4) above. (6) A method for manufacturing foundry sand to be used in an inkjet-type additive manufacturing method, in which a resin is printed onto mixed sand obtained by mixing foundry sand with a hardener for hardening a resin, to form a sand mold, Manufacture molding sand by mixing a predetermined amount of recycled sand obtained by the method for recycling molding sand according to any one of (1) to (5) above with new sand. Methods for producing foundry sand. (7) In the step of producing the foundry sand, more than 0 parts by weight and 100 parts by weight or less of the recycled sand is mixed with 100 parts by weight of the new sand. The method for producing foundry sand according to (6) above. (8) A method for manufacturing a sand mold by an inkjet-type additive manufacturing method, in which a resin is printed onto mixed sand obtained by mixing foundry sand with a hardener for hardening a resin, to form a sand mold, In the step of kneading the hardener and the foundry sand, a predetermined amount of recycled sand obtained by the method for regenerating foundry sand according to any one of (1) to (5) above is mixed with new sand. Sand mold manufacturing method. (9) In the step of kneading the hardener and the foundry sand, foundry sand is used in which more than 0 part by weight and 100 parts by weight or less of the recycled sand is mixed with 100 parts by weight of the new sand. The method for manufacturing a sand mold according to (8) above. [Explanation of symbols]

[0023] 1...Kneading process, 2...Molding process, 3...Casting process, 4...Sand recovery process, 5...Resin kneading process, 6...Crushing process, 7...Mixing process, 8...Roasting and recycling process, 9...Foundry sand manufacturing process, 10...Foundry sand, 11...New sand, 12...Recycled sand, 13...Hardening agent, 14...Mixed sand, 15...Resin, 16...Sand mold, 17...Resin-hardened sand, 18...Unhardened sand, 19...Specified resin, 20...Specified resin-mixed sand, 21...Crushed material, 100...Three-dimensional additive manufacturing device, 200...Fluidized roasting furnace, 201...Air, 202...Combustion chamber, 203...Sand fluidized bed, 204...Burner, 205...Thermometer

Claims

1. A method for regenerating foundry sand used in an inkjet-type additive manufacturing method in which a resin is printed onto mixed sand obtained by kneading foundry sand with a hardener that hardens a resin, to form a sand mold, comprising: a resin mixing step of mixing a predetermined amount of a predetermined resin into the mixed sand to which the resin did not adhere during molding of the sand mold, thereby obtaining a predetermined resin mixed sand; a crushing step of crushing the resin-mixed sand obtained in the resin mixing step and the mixed sand to which the resin adhered during molding in the sand mold to obtain a crushed product; a roasting and regeneration step of roasting the crushed material obtained in the crushing step to produce reclaimed sand; A method for regenerating foundry sand.

2. The mixed sand to which the resin did not adhere during molding of the sand mold is at least one of the mixed sand to which the resin was not printed during molding of the sand mold, the mixed sand that was not used for molding the sand mold, and the contaminated foundry sand; The mixed sand to which the resin adhered during molding of the sand mold is at least one of the sand mold used for casting and the mixed sand to which the resin adhered during molding of the sand mold but which does not constitute the sand mold.

2. A method for reclaiming foundry sand according to claim 1.

3. The predetermined resin includes at least one of a furan resin and a phenol resin.

2. A method for reclaiming foundry sand according to claim 1.

4. In the resin mixing step, 0.1 to 5.0 parts by weight of the predetermined resin is mixed with 100 parts by weight of unhardened sand, which is the mixed sand to which the resin did not adhere during molding of the sand mold.

2. A method for reclaiming foundry sand according to claim 1.

5. In the roasting and regeneration step, the crushed material is roasted at a roasting temperature of 300°C or higher and 550°C or lower.

2. A method for reclaiming foundry sand according to claim 1.

6. A method for manufacturing foundry sand to be used in an inkjet-type additive manufacturing method, in which a resin is printed onto mixed sand obtained by mixing foundry sand with a hardener for hardening a resin, to form a sand mold, 10. Foundry sand is manufactured by mixing a predetermined amount of recycled sand obtained by the method for recycling foundry sand according to any one of claims 1 to 5 with new sand. Methods for producing foundry sand.

7. In the manufacturing process of the foundry sand, more than 0 parts by weight and 100 parts by weight or less of the reclaimed sand is mixed with 100 parts by weight of the new sand. The method for producing foundry sand according to claim 6.

8. A method for manufacturing a sand mold by an inkjet-type additive manufacturing method, in which a resin is printed onto mixed sand obtained by mixing foundry sand with a hardener for hardening a resin, to form a sand mold, In the step of kneading the hardener and the foundry sand, a predetermined amount of recycled sand obtained by the method for reclaiming foundry sand according to any one of claims 1 to 5 is mixed with new sand. Sand mold manufacturing method.

9. In the step of kneading the hardener and the foundry sand, foundry sand is used in which more than 0 part by weight and 100 parts by weight or less of the reclaimed sand is mixed with 100 parts by weight of the new sand. The method for manufacturing a sand mold according to claim 8.

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