Inspecting method and inspecting apparatus for casting sand

Abstract

To reduce the time required for inspecting casting sand.SOLUTION: In one embodiment, a method for inspecting casting sand includes the steps of: feeding the casting sand into a test tube; measuring compactability (CB) of the casting sand while compacting the casting sand in the test tube to make a test piece; and compressing the test piece to measure the compressive strength of the test piece.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a method and an apparatus for inspecting foundry sand. [Background technology]

[0002] Sand molds made from molding sand are widely used as casting molds for casting. For example, green sand molds, which are a type of sand mold, are made using molding sand in which binders and additives are added to silica sand. Generally, the green sand molds used for casting are once crushed, and the molding sand recovered is reused as recycled sand by adding binders and additives to it. Since the quality of the recycled molding sand affects the accuracy of the casting, the quality of the molding sand is controlled in the foundry. Specifically, parameters that indicate the characteristics of the molding sand, such as compactability (CB), moisture content, temperature, air permeability, and compressive strength, are measured before the sand mold is made, and it is confirmed whether these parameters are within the range of the control values.

[0003] As a technique for inspecting molding sand, for example, the device described in Patent Document 1 is known. The device described in Patent Document 1 includes a test cylinder, a pressing rod having a pressure plate that rises and falls inside the test cylinder, and a cylinder having a piston rod connected to the pressing rod, and after positioning the pressure plate based on the previously measured CB of the molding sand, the molding sand is supplied into the test cylinder, the molding sand is compressed in the test cylinder to prepare a test piece of a specified height (50 mm), and the compressive strength of the test piece is measured from the load at which the test piece is broken by compressing it with a specified pressure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-318511 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, in the device described in Patent Document 1, the CB of the molding sand is measured in advance to prepare a test piece of a specified height, and then the compressive strength is measured. That is, in this device, the molding sand samples are charged in two batches, and the CB and compressive strength of the molding sand are measured separately for each sample, which causes a problem of long inspection time for the molding sand.

[0006] Therefore, an object of the present disclosure is to reduce the inspection time for molding sand. [Means for solving the problem]

[0007] A method for inspecting molding sand according to one embodiment includes the steps of pouring molding sand into a test tube, compressing the molding sand in the test tube to produce a test piece while measuring the compactability (CB) of the molding sand, and compressing the test piece to measure the compressive strength of the test piece. Effect of the Invention

[0008] According to the present disclosure, the inspection time for molding sand can be reduced. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating a schematic configuration of an inspection device according to an embodiment. [Diagram 2] FIG. 2 is a block diagram showing a functional configuration of a control device. [Diagram 3] 1 is a flowchart illustrating an inspection method according to an embodiment. [Figure 4] FIG. 13 is a diagram illustrating the operation of the inspection device. [Diagram 5] FIG. 13 is a diagram illustrating the operation of the inspection device. [Figure 6] FIG. 13 is a diagram illustrating the operation of the inspection device. [Figure 7] 1 is a graph showing the relationship between the height of a test piece and the compressive strength. [Figure 8] 1 is a graph showing a relationship between compressive strength before and after correction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicated descriptions are omitted. The drawings may be partially simplified or exaggerated for ease of understanding, and the dimensional ratios and angles are not limited to those shown in the drawings. In this specification, the terms "upper", "lower", "left", and "right" are based on the illustrated state and are for convenience.

[0011] FIG. 1 is a diagram showing a schematic configuration of an inspection device 1 according to an embodiment. The inspection device 1 inspects the characteristics of molding sand used to make a casting mold. Molding sand is a raw material for a sand mold, and is typically green sand. Green sand is made by kneading, for example, silica sand, a binder, and additives. Bentonite, for example, is used as a binder for green sand. Water, coal powder, starch, and the like are used as additives.

[0012] Since the accuracy of a casting is affected by the characteristics of the casting sand, the characteristics of the casting sand are inspected before the mold is made. Parameters indicating the characteristics of the casting sand include, for example, compactability (CB), moisture content, temperature, air permeability, and compressive strength. The parameters indicating the characteristics of the casting sand are measured and stored by the inspection device 1. When a casting defect occurs, the stored parameters are read out and used in activities to prevent the casting defect.

[0013] CB is the shrinkage rate [%] when molding sand is compressed with a certain force. Moisture content represents the amount of free moisture in the molding sand. Compressive strength [N / cm 2 ] is the value obtained by dividing the load when the standard test piece is compressed to break by the cross-sectional area of ​​the standard test piece. The standard test piece is prepared according to the method specified in JIS Z 2601 "Testing method for casting sand". Specifically, JIS Z 2601 stipulates that the casting sand in a test tube is tamped with a specified pressure to prepare a standard test piece with a height of 50 mm ± 1 mm, and that the compressive strength is measured using this standard test piece.

[0014] As shown in FIG. 1, the inspection device 1 includes a test tube 11, a chute 12, a pressing rod 13, a first cylinder 14, a load sensor 15, a second cylinder 16, a scraper 17, and a control device 18. The test tube 11 is, for example, a cylindrical body made of steel, and defines an internal space 11s for accommodating casting sand. The test tube 11 is supported by a frame 2 via a support member 3. The test tube 11 has an upper opening 11a and a lower opening 11b, and extends along an axis Z between the upper opening 11a and the lower opening 11b. Hereinafter, the direction along the axis Z may be referred to as the "axial direction". Typically, the axial direction coincides with the up-down direction. The inner diameter of the test tube 11 is constant in the axial direction.

[0015] The chute 12 is provided above the test cylinder 11. The chute 12 guides molding sand stored in a tank (not shown) so that it is poured into the test cylinder 11. The chute 12 may have an outlet that can be opened or closed, and the supply of molding sand to the test cylinder 11 can be switched on or off by opening or closing the outlet. The opening and closing of the outlet is controlled by a control device 18.

[0016] The pressing rod 13 extends along the axis Z, and its upper portion is inserted into the test tube 11. A pressing plate 20 is provided at the upper end of the pressing rod 13. The pressing plate 20 is, for example, a disk-shaped plate, and is disposed in the internal space 11s of the test tube 11. The lower end of the pressing rod 13 is connected to a piston rod 22 of a first cylinder 14, which will be described later. The pressing rod 13 moves in the axial direction as the piston rod 22 moves up and down.

[0017] The first cylinder 14 is provided below the test tube 11. The first cylinder 14 includes a cylinder body 21, a piston rod 22, and a motor 23. The cylinder body 21 is provided on a stand 4 arranged at the bottom of the inspection device 1, and supports the piston rod 22 so that it can advance and retreat. The piston rod 22 extends upward from the cylinder body 21 along the axis Z, and is provided so that it can ascend and descend relative to the cylinder body 21. The upper end of the piston rod 22 is connected to the lower end of the pressing rod 13. The pressure plate 20 of the pressing rod 13 moves in the axial direction (up and down) within the test tube 11 as the piston rod 22 ascends and descends.

[0018] The motor 23 is, for example, a servo motor that moves the piston rod 22 up and down. The motor 23 includes a motor body 23a and an encoder 23b. The motor body 23a drives an output shaft by power supplied from an external power source. The driving force of the motor body 23a is transmitted to the piston rod 22 via the cylinder body 21, and moves the piston rod 22 up and down along the axis Z. The encoder 23b detects the rotation angle of the output shaft of the motor body 23a. The rotation angle of the output shaft corresponds to the axial movement distance of the pressing rod 13. The encoder 23b identifies the position of the pressure plate 20 in the axial direction from the rotation angle of the output shaft.

[0019] The load sensor 15 is disposed between the pressing rod 13 and the piston rod 22. The load sensor 15 is, for example, a load cell, and measures the load applied to the pressing rod 13 from the piston rod 22. The load sensor 15 outputs information indicating the measured load to the control device 18.

[0020] The second cylinder 16 is provided on the side of the test tube 11. The second cylinder 16 includes a cylinder body 25, a piston rod 26, and a motor 27. The cylinder body 25 is supported by the frame 2, and supports the piston rod 26 so that it can advance and retreat in a direction perpendicular to the axis Z (horizontal direction). The piston rod 26 extends horizontally from the cylinder body 25, and is provided so that it can advance and retreat relative to the cylinder body 25. The tip of the piston rod 26 is connected to a scraper 17. The scraper 17 moves horizontally as the piston rod 26 advances and retreats.

[0021] The motor 27 is, for example, a servo motor that drives the piston rod 26. The motor 27 includes a motor body 27a and an encoder 27b. The motor body 27a drives an output shaft by power supplied from an external power source. The driving force of the motor body 27a is transmitted to the piston rod 26 via the cylinder body 25, and moves the piston rod 26 in the horizontal direction. The encoder 27b detects the rotation angle of the output shaft of the motor body 27a. The rotation angle of the output shaft corresponds to the horizontal movement distance of the scraper 17. The encoder 27b identifies the position of the scraper 17 in the horizontal direction from the rotation angle of the output shaft.

[0022] The scraper 17 is connected to the piston rod 26 of the second cylinder 16. The scraper 17 has a closing surface 17a for closing the upper opening 11a of the test tube 11, and a measuring surface 17b arranged above the closing surface 17a. The closing surface 17a and the measuring surface 17b are planes perpendicular to the axis Z and directed downward. The closing surface 17a is arranged at substantially the same height as the upper opening 11a of the test tube 11 in the axial direction. The distance between the closing surface 17a and the measuring surface 17b in the axial direction is set higher than the target height of the test piece.

[0023] The scraper 17 moves horizontally in accordance with the advancement and retreat of the piston rod 26. Specifically, the scraper 17 is movable among a closing position where the closing surface 17a closes the upper opening 11a of the test cylinder 11, a retracted position offset with respect to the supply path of the casting sand from the chute 12 to the test cylinder 11, and a measurement position where the measurement surface 17b is positioned above the upper opening 11a of the test cylinder 11.

[0024] The inspection device 1 may further include a rail 36 and a slider 37. The rail 36 is fixed to the upper part of the frame 2 and extends parallel to the piston rod 26. The slider 37 is slidably attached to the rail 36. The slider 37 is connected to the scraper 17 by a bolt or the like. When the piston rod 26 advances or retreats, the slider 37 slides along the rail 36 and guides the scraper 17 in the horizontal direction.

[0025] The inspection device 1 also includes various sensors for measuring the characteristics of the molding sand. Specifically, the inspection device 1 includes a temperature sensor 31, a moisture sensor 32, and a pressure sensor 33. The temperature sensor 31 is disposed above the test tube 11 and measures the temperature of the molding sand. The moisture sensor 32 is provided in the test tube 11 and measures the moisture content of the molding sand contained in the internal space 11s of the test tube 11. The pressure sensor 33 is provided in the test tube 11 and measures the pressure of the internal space 11s of the test tube 11.

[0026] The control device 18 is a computer equipped with a processor, a storage unit, an input device, a display device, etc., and controls the overall operation of the inspection device 1. The storage unit of the control device 18 stores a control program for controlling various processes executed by the control device 18 by the processor. The control device 18 is connected to the chute 12, the first cylinder 14, the load sensor 15, the second cylinder 16, the encoders 23b and 27b, the temperature sensor 31, the moisture sensor 32, and the pressure sensor 33 so as to be able to communicate with them.

[0027] The control device 18 sends control signals to the chute 12, the first cylinder 14, and the second cylinder 16 to control the operations of the chute 12, the first cylinder 14, and the second cylinder 16. The control device 18 also receives measurement values ​​from the load sensor 15, the temperature sensor 31, the moisture sensor 32, and the pressure sensor 33 to measure parameters indicative of the characteristics of the molding sand.

[0028] Fig. 2 is a block diagram showing the functional configuration of control device 18. As shown in Fig. 2, control device 18 has, as its functional configuration, a control unit 40 and a measurement unit 50. Control unit 40 includes a predicted value acquisition unit 41, an input amount determination unit 42, an input control unit 43, a first cylinder control unit 44, and a second cylinder control unit 45.

[0029] The predicted value acquisition unit 41 acquires a predicted value of the CB of the foundry sand. A skilled operator may be able to predict the CB of the foundry sand from the appearance, feel, weather, etc. of the foundry sand. In this case, the predicted value acquisition unit 41 acquires a predicted value of the CB input by the operator via an input device, for example. The predicted value acquisition unit 41 may acquire a CB of the foundry sand measured in the past as a predicted value of the CB. For example, the CB of the foundry sand measured in the past for each processing line of the foundry sand is stored in the storage unit, and the predicted value acquisition unit 41 may read out the CB of the corresponding processing line from the storage unit and acquire it as a predicted value of the CB.

[0030] The charge amount determination unit 42 determines the amount of molding sand to be charged into the test tube 11 in order to prepare a test piece with a target height (e.g., 50 mm). The amount of molding sand to be charged into the test tube 11 is calculated from the target height of the test piece to be prepared and the predicted value of CB. The amount of molding sand to be charged into the test tube 11 is represented by the height of the molding sand before compression. The height of the molding sand before compression is the height of the molding sand in the test tube 11 before compression based on the height of the pressure plate 20. In the following description, the height of the molding sand before compression may be referred to as the "sand charge height". For example, when the target height of the test piece is Ht and the predicted value of CB is CBp, the sand charge height H1 of the test tube 11 is calculated as shown in the following formula (1).

[0031] H1=100×Ht / (100-CBp) (1)

[0032] The sand pouring height H1 calculated by formula (1) corresponds to the amount of molding sand to be poured into the test tube 11 in order to prepare a test piece having the target height Ht. As described above, the lower the predicted value CBp of CB, the lower the sand pouring height H1, and the higher the predicted value CBp of CB, the higher the sand pouring height H1. The predicted value acquisition unit 41 may acquire a predicted value of the amount of molding sand to be poured into the test tube 11 in order to prepare a test piece having the target height Ht from an operator. When a predicted value of the amount of molding sand is input by the operator, the predicted value may be determined as the amount of molding sand to be poured into the test tube 11 without acquiring the predicted value of CB.

[0033] The charging control unit 43 controls the chute 12 to supply molding sand into the test cylinder 11. For example, the charging control unit 43 controls the chute 12 so that the amount of molding sand determined by the charging amount determination unit 42 is charged into the test cylinder 11.

[0034] The first cylinder control unit 44 controls the motor 23 of the first cylinder 14 to adjust the stroke amount (rising distance or descending distance) of the piston rod 22. The position of the pressure plate 20 in the axial direction is adjusted according to the stroke amount of the piston rod 22. The position of the pressure plate 20 in the axial direction is specified based on the output of the encoder 23b. That is, the first cylinder control unit 44 controls the position of the pressure plate 20 in the up-down direction based on the output of the encoder 23b. The depth of the test tube 11, i.e., the sand filling height H1, changes according to the position of the pressure plate in the axial direction.

[0035] The second cylinder control unit 45 controls the motor 27 of the second cylinder 16 to adjust the stroke amount of the piston rod 26. The position of the scraper 17 in the horizontal direction is adjusted according to the stroke amount of the piston rod 26. The position of the scraper 17 in the horizontal direction is specified based on the output of the encoder 27b. That is, the second cylinder control unit 45 controls the position of the scraper 17 in the horizontal direction based on the output of the encoder 27b.

[0036] The measurement unit 50 includes a temperature measurement unit 51, a moisture content measurement unit 52, a CB measurement unit 53, an air permeability measurement unit 54, a compressive strength measurement unit 55, and a compressive strength correction unit 56. The temperature measurement unit 51 measures the temperature of the molding sand based on the output value of the temperature sensor 31. The moisture content measurement unit 52 measures the moisture content of the molding sand based on the output value of the moisture sensor 32.

[0037] The CB measuring unit 53 measures the CB of the molding sand based on the difference between the height of the molding sand in the test tube 11 before compression and the height of the molding sand in the test tube 11 after compression. The height of the molding sand before compression is the surface height of the molding sand in the test tube 11 based on the height of the pressure plate 20, i.e., the sand pouring height. The height of the molding sand after compression is the height of a test piece made by compressing the molding sand. The height of the molding sand in the test tube 11 is specified based on the stroke amount of the first cylinder 14, which is determined from the output of the encoder 23b.

[0038] The air permeability measuring unit 54 measures the air permeability of the test piece. Specifically, the air permeability measuring unit 54 supplies air from the air source 35 into the test tube 11 so that the air passes through the test piece, and measures the air permeability of the test piece based on the flow rate of the air when the pressure inside the test tube 11 becomes constant.

[0039] The compressive strength measuring unit 55 measures the compressive strength of the test piece. Specifically, the compressive strength measuring unit 55 acquires the load when the test piece is compressed to break from the load sensor 15, and measures the compressive strength of the test piece based on the load.

[0040] The compressive strength correction unit 56 corrects the compressive strength based on the difference between the target height of the test piece and the measured height of the test piece. For example, when the measured height of the test piece is greater than the target height, the compressive strength correction unit 56 corrects the measured compressive strength to be greater, and when the measured height of the test piece is less than the target height, the compressive strength correction unit 56 corrects the measured compressive strength to be smaller. The measuring unit 50 stores the measured temperature, moisture content, CB, air permeability, and corrected compressive strength of the molding sand in the memory unit and displays them on the display unit 60.

[0041] Hereinafter, a method for inspecting molding sand using the inspection device 1 will be described. Fig. 3 is a flowchart showing a method for inspecting molding sand according to one embodiment. In this inspection method, the CB and compressive strength are measured from molding sand S1 charged into a test tube 11. Each step in Fig. 3 is executed by a control device 18 controlling each element of the inspection device 1.

[0042] 3, first, the predicted value acquisition unit 41 of the control device 18 acquires a predicted value of CB of the molding sand S1 (step ST1). The predicted value of CB is input to the inspection device 1 by, for example, an operator. The predicted value acquisition unit 41 may read out a previously measured CB of the molding sand S1 from a storage unit and use it as the predicted value of CB.

[0043] Next, the charge amount determination unit 42 determines the amount of foundry sand S1 to be charged into the test cylinder 11 in order to prepare a test piece S2 of a target height (e.g., 50 mm) (step ST2). For example, the charge amount determination unit 42 substitutes the target height of the test piece S2 and the predicted value of CB into the above formula (1) to obtain the sand charging height H1. As described above, since the diameter of the test cylinder 11 is constant in the axial direction, the sand charging height H1 corresponds to the amount of foundry sand S1 to be charged into the test cylinder 11 in order to prepare a test piece S2 of the target height.

[0044] Next, as shown in FIG. 4(a), the first cylinder control unit 44 controls the stroke amount of the first cylinder 14 to adjust the position of the pressure plate 20 so that the distance between the pressure plate 20 and the upper opening 11a of the test tube 11 becomes the sand pouring height H1 obtained in step ST2 (step ST3). Next, as shown in FIG. 4(b), the second cylinder control unit 45 controls the second cylinder 16 to place the scraper 17 in the retreat position. Then, the pouring control unit 43 controls the chute 12 to pour the molding sand S1 into the test tube 11 (step ST4). At this time, the chute 12 pours the molding sand S1 into the test tube 11 so that the molding sand S1 overflows from the upper opening 11a of the test tube 11.

[0045] Next, the temperature of the molding sand S1 is measured by the temperature sensor 31 (step ST5). The temperature measurement unit 51 obtains information indicating the temperature of the molding sand S1 from the temperature sensor 31 and stores the information.

[0046] Next, as shown in Fig. 4(c), the second cylinder control section 45 advances the piston rod 26 of the second cylinder 16 to place the scraper 17 in the closed position. As the scraper 17 moves from the retracted position to the closed position, a portion of the excess molding sand S1 that has overflowed from the test cylinder 11 is removed. As the scraper 17 is placed in the closed position, the upper opening 11a of the test cylinder 11 is covered and closed by the closing surface 17a of the scraper 17. As a result, the height of the molding sand S1 before compression coincides with the sand pouring height H1.

[0047] 5(a), the first cylinder control unit 44 raises the piston rod 22 of the first cylinder 14, and applies a specified pressure to the molding sand S1 from the pressure plate 20. As a result, the molding sand S1 is compressed between the pressure plate 20 and the closing surface 17a of the scraper 17, and a test piece S2 of the molding sand S1 is produced (step ST6). At this time, the pressure applied to the molding sand S1 from the pressure plate 20 is measured by the load sensor 15, and is fed back so as to reach the specified pressure.

[0048] Next, the CB measurement unit 53 measures the height H2 of the test piece S2 (step ST7). The height H2 of the test piece is found based on the position of the pressure plate 20, which is determined by the output of the encoder 23b. The height H2 of the test piece measured in step ST7 is the measured height of the test piece S2. Next, the CB measurement unit 53 calculates the CB of the molding sand S1 (step ST8). The CB of the molding sand S1 is found based on the difference between the height of the molding sand S1 before compression (i.e., the sand pouring height H1) and the height H2 of the test piece S2 produced by compressing the molding sand S1. Specifically, CB [%] is found from the following formula (2).

[0049] CB = (H1 - H2) / H1 × 100 (2)

[0050] As described above, the CB measurement unit 53 measures the CB of the molding sand S1 while compressing the molding sand S1 in the test tube 11 to prepare the test piece S2. The CB of the molding sand S1 measured by the formula (2) is the measured value of CB.

[0051] Next, the moisture sensor 32 measures the amount of moisture contained in the test piece S2 (step ST9). The moisture amount measuring unit 52 acquires information indicating the amount of moisture contained in the test piece S2 from the moisture sensor 32 and stores the information. Note that the moisture amount measuring unit 52 may measure the amount of moisture before producing the test piece S2.

[0052] 5(b), the second cylinder control unit 45 advances the piston rod 26 of the second cylinder 16. This advances the scraper 17, and the excess molding sand S1 remaining on the upper surface of the test tube 11 is removed.

[0053] Next, the air permeability of the test piece S2 is measured (step ST10). As shown in FIG. 5(c), in order to measure the air permeability of the test piece S2, the first cylinder control unit 44 first lowers the piston rod 22 of the first cylinder 14, and the second cylinder control unit 45 controls the second cylinder 16 to move the scraper 17 to the measurement position. Then, the air permeability measurement unit 54 controls the air source 35 to supply air 35a into the test tube 11 through the gap formed between the pressure plate 20 and the test piece S2, and passes the air 35a through the test piece S2. Then, the air permeability measurement unit 54 adjusts the flow rate of the air 35a so that the pressure in the test tube 11 is constant while monitoring the pressure sensor 33, and calculates the air permeability based on the flow rate of the air 35a when the pressure becomes constant. For example, when the pressure of the internal space 11s measured by the pressure sensor 33 is p and the flow rate of the air 35a is F, the air permeability P can be calculated from the following formula (3).

[0054] P = (F × H2) / p (3)

[0055] Next, the compressive strength of the test piece S2 is measured (step ST11). As shown in FIG. 6(a), in order to measure the compressive strength of the test piece S2, the compressive strength measuring unit 55 raises the piston rod 22 of the first cylinder 14 and brings the test piece S2 into contact with the measurement surface 17b. Then, the compressive strength measuring unit 55 further raises the piston rod 22 and applies a specified pressure to the test piece S2 from the pressure plate 20, destroying the test piece S2. Then, the compressive strength measuring unit 55 obtains from the load sensor 15 the load at which the test piece S2 is destroyed.

[0056] Next, the compressive strength measuring section 55 divides the load at which the test piece S2 breaks by the cross-sectional area of ​​the test piece S2 (i.e., the cross-sectional area of ​​the internal space 11c) to obtain the compressive strength. 2 ] and the breaking load of the test piece S2 is W [N], the compressive strength of the test piece S2 is σ [N / cm 2 ] can be calculated from the following formula (4).

[0057] σ = W / A (4)

[0058] After measuring the compressive strength σ, as shown in Fig. 6(b), the second cylinder control section 45 advances the piston rod 26 of the second cylinder 16. This causes the test piece S2 to be removed.

[0059] Next, the compressive strength σ is corrected based on the difference between the target height and the measured height of the test piece S2 (step ST12). Since the sand pouring height H1 is calculated from the predicted value of CB, the height H2 of the test piece S2 produced by compressing the molding sand S1 may deviate from the target height. Since the compressive strength σ depends on the height H2 of the test piece S2, if the height H2 of the test piece S2 deviates from the target height, the compressive strength σ calculated by formula (4) will deviate from the true compressive strength.

[0060] For example, Figure 7 is a graph showing the relationship between the height of a test piece and the compressive strength when test pieces of different heights were made using the same casting sand and the compressive strength of each test piece was measured. As shown in Figure 7, a linear relationship is confirmed between the height of the test piece and the compressive strength. Specifically, the higher the test piece is, the smaller the measured compressive strength becomes relative to the true compressive strength, and the lower the test piece is, the larger the measured compressive strength becomes relative to the true compressive strength.

[0061] By utilizing this relationship, as shown in Figure 8, the measured compressive strength can be corrected to be larger when the height of the test specimen is higher than the target height (50 mm), and the measured compressive strength can be corrected to be smaller when the height of the test specimen is lower than the target height (50 mm), thereby making the measured compressive strength closer to the true compressive strength.

[0062] Therefore, when the height H2 of the test piece S2 measured in step ST7 is greater than the target height, the compressive strength correction unit 56 corrects the measured compressive strength σ to be greater, and when the height H2 of the test piece S2 is smaller than the target height, the compressive strength correction unit 56 corrects the measured compressive strength σ to be smaller. Note that the greater the difference between the height H2 of the test piece S2 and the target height, the greater the correction amount of the compressive strength σ. The corrected values ​​of the CB, temperature, moisture content, air permeability and compressive strength measured in a series of steps are displayed on the display device 60.

[0063] As described above, in the inspection method according to one embodiment, the CB of the molding sand S1 is measured while compressing the molding sand S1 in the test cylinder 11 to prepare the test piece S2, so that the CB and compressive strength of the molding sand S1 can be measured from a single sample of the molding sand S1 charged into the test cylinder 11. This eliminates the need to charge the molding sand S1 in two separate charges, thereby reducing the number of inspection steps. As a result, the inspection time for the molding sand S1 can be shortened.

[0064] In addition, in this inspection method, when the height H2 of the test piece S2 is higher than the target height, the compressive strength is corrected to be larger, and when the height H2 of the test piece S2 is smaller than the target height, the compressive strength is corrected to be smaller, so that the measured value of the compressive strength can be made closer to the true compressive strength. Note that, as shown in formula (3), the calculation of the air permeability P includes the height H2 of the test piece S2, so even if the height H2 of the test piece S2 deviates from the target height, the effect on the measurement of the air permeability P is small.

[0065] Although the method and device 1 for inspecting foundry sand according to various embodiments have been described above, the present invention is not limited to the above-described embodiments and various modifications can be made without departing from the spirit of the invention. In other words, it should be noted that the above-described embodiments are intended as illustrative examples and do not limit the scope of the present invention.

[0066] For example, in the above embodiment, the amount of molding sand to be charged into the test cylinder 11 is determined using the predicted value of CB, but the amount of molding sand to be charged into the test cylinder 11 may be determined without using the predicted value of CB. For example, when a predicted value of the amount of molding sand is input by an operator, the predicted value of the amount of molding sand may be determined as the amount of molding sand to be charged into the test cylinder 11. Also, when CB can be predicted with high accuracy, it is not always necessary to correct the measured value of compressive strength.

[0067] In the above embodiment, the amount of molding sand charged into the test tube 11 is adjusted by controlling the position of the pressure plate 20. However, the amount of molding sand charged into the test tube 11 may be adjusted by leaving the pressure plate 20 in the lowest position and adjusting the amount of molding sand supplied from the chute 12.

[0068] In the above embodiment, CB, temperature, moisture content, air permeability, and compressive strength are measured as parameters indicating the characteristics of the molding sand, but it is sufficient to measure at least one parameter. For example, in one embodiment, molding sand may be compressed in the test tube 11 to prepare a test piece of a target height, and the test piece may be used to measure only the compressive strength. Even when only the compressive strength of the test piece is measured, the height of the test piece may deviate from the target height. In this case, the measured value of the compressive strength can be corrected to bring the measured value of the compressive strength closer to the true compressive strength.

[0069] The present disclosure includes the following:

[0070] [Clause 1] One embodiment of a method for inspecting molding sand includes the steps of pouring molding sand into a test tube, compressing the molding sand in the test tube to produce a test piece while measuring the compactability (CB) of the molding sand, and compressing the test piece to measure the compressive strength of the test piece.

[0071] In the above inspection method, the CB of the molding sand is measured while compressing the molding sand in the test tube to prepare a test piece, so the CB and compressive strength of the molding sand can be measured from a single sample of the molding sand poured into the test tube. This eliminates the need to pour the molding sand into the test tube twice, reducing the number of inspection steps. As a result, the inspection time for the molding sand can be shortened.

[0072] [Clause 2] The inspection method described in Clause 1 may further include the steps of: acquiring a predicted value of CB of the molding sand; and determining, based on the predicted value of CB, an amount of molding sand to be charged into the test tube in order to prepare a test piece of a target height. By determining the amount of molding sand to be supplied into the test tube based on the predicted value of CB, the height of the test piece can be brought closer to the target height. By bringing the height of the test piece closer to the target height, the measurement accuracy of the compressive strength can be improved.

[0073] [Clause 3] The inspection method according to Clause 2, further comprising a step of adjusting the position of a pressure plate that can be raised and lowered within the test tube based on the amount of molding sand to be charged into the test tube.

[0074] [Clause 4] The inspection method according to any one of clauses 1 to 3 may further include a step of measuring the height of the test specimen, and a step of correcting the compressive strength based on the difference between the target height of the test specimen and the measured height of the test specimen. Since the load when the test specimen is compressed to break depends on the height of the test specimen, if the actual height of the test specimen deviates from the target height, the measurement accuracy of the compressive strength decreases. In contrast, in this embodiment, the compressive strength is corrected based on the difference between the target height of the test specimen and the measured height of the test specimen, so that the measured compressive strength can be made closer to the true compressive strength.

[0075] [Clause 5] In the inspection method described in Clause 4, when the measured height of the test piece is greater than the target height, the measured compressive strength may be corrected to be greater, and when the measured height of the test piece is less than the target height, the measured compressive strength may be corrected to be smaller. When the height of the test piece is greater than the target height, the measured compressive strength is lower than the true compressive strength, so that the measured compressive strength can be made closer to the true compressive strength by increasing the compressive strength. Conversely, when the height of the test piece is less than the target height, the measured compressive strength is higher than the true compressive strength, so that the measured compressive strength can be made closer to the true compressive strength by decreasing the compressive strength.

[0076] [Clause 6] The inspection method according to any one of clauses 1 to 5 may further include a step of measuring the temperature of the molding sand before preparing the test piece.

[0077] [Clause 7] The inspection method according to Clause 6 may further include a step of measuring the moisture content of the molding sand after measuring the temperature of the molding sand.

[0078] [Clause 8] The inspection method according to any one of clauses 1 to 7 may further include a step of measuring the air permeability of the test piece before measuring the compressive strength.

[0079] [Clause 9] A molding sand inspection device according to one embodiment includes a test cylinder extending in an axial direction, a chute for supplying molding sand into the test cylinder, a pressing rod having a pressure plate movable in the axial direction inside the test cylinder, a cylinder connected to the pressing rod and having a piston rod movable back and forth in the axial direction, a load sensor disposed between the pressing rod and the piston rod, and a control device for controlling the operation of the chute and the cylinder, wherein the control device includes an injection control unit for controlling the chute to inject molding sand into the test cylinder, a CB measurement unit for compressing the molding sand in the test cylinder with the pressure plate to prepare a test piece while measuring the compactability (CB) of the molding sand, and a compressive strength measurement unit for measuring the compressive strength of the test piece based on the load measured by the load sensor when the test piece is compressed to destruction.

[0080] In the above inspection device, the CB of the molding sand is measured while compressing the molding sand in the test tube to prepare a test piece, so the CB and compressive strength of the molding sand can be measured from a single sample of molding sand poured into the test tube. This eliminates the need to pour the molding sand in two batches, reducing the number of inspection steps. As a result, the inspection time for molding sand can be shortened. [Explanation of symbols]

[0081] 1...inspection device, 11...test tube, 12...chute, 13...pressure rod, 15...load sensor, 18...control device, 20...pressure plate, 22, 26...piston rod, 43...feeding control unit, 53...CB measurement unit, 55...compressive strength measurement unit, S1...molding sand, S2...test piece.

Claims

1. pouring molding sand into a test tube; a step of measuring compactability (CB) of the molding sand while compressing the molding sand in the test tube to prepare a test piece; compressing the test piece to measure the compressive strength of the test piece; A method for inspecting foundry sand, comprising:

2. obtaining a predicted value of CB of the foundry sand; determining an amount of molding sand to be charged into the test tube in order to prepare the test piece having a target height based on the predicted value of CB; The inspection method of claim 1 , further comprising:

3. 3. The inspection method according to claim 2, further comprising a step of adjusting a position of a pressure plate that can be raised and lowered within the test cylinder based on an amount of molding sand to be charged into the test cylinder.

4. Measuring the height of the test piece; correcting the compressive strength based on a difference between a target height of the test specimen and a measured height of the test specimen; The inspection method of claim 1 , further comprising:

5. 5. The inspection method according to claim 4, wherein, when the measured value of the height of the test piece is greater than the target height, the measured compressive strength is corrected to be greater, and, when the measured value of the height of the test piece is smaller than the target height, the measured compressive strength is corrected to be smaller.

6. The method of claim 1 , further comprising the step of measuring a temperature of the foundry sand before preparing the test specimen.

7. 7. The method according to claim 6, further comprising the step of measuring a moisture content of the foundry sand after measuring the temperature of the foundry sand.

8. The method of claim 1 , further comprising the step of measuring the air permeability of the test piece before measuring the compressive strength.

9. A test tube extending in an axial direction; a chute for supplying molding sand into the test tube; a pressing rod having a pressing plate movable in the axial direction within the test tube; a cylinder having a piston rod connected to the pressing rod and movable in the axial direction; A load sensor disposed between the pressing rod and the piston rod; A control device for controlling the operation of the chute and the cylinder; Equipped with The control device includes: a charging control unit that controls the chute to charge the casting sand into the test tube; a CB measuring section for measuring compactability (CB) of the molding sand while compressing the molding sand in the test tube with the pressure plate to prepare a test piece; a compressive strength measuring unit that measures the compressive strength of the test piece based on the load measured by the load sensor when the test piece is compressed to break; 23. An inspection device comprising:

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