Patent Publication Number: US-11045866-B2

Title: Method for preventing defect caused by shift in cavity parts

Description:
TECHNICAL FIELD 
     The present invention relates to a method for preventing a defect that is caused by a shift in cavity parts when molding. Specifically, it relates to a method for estimating a shift in cavity parts to prevent a defect that may be caused by the shift. 
     BACKGROUND ART 
     In a foundry, a line for molding that molds a cope and a drag, especially a line for molding a cope and a drag with flasks, assembles a carrier for a pattern (a carrier plate), which is mounted on it, and a flask for a cope flask and a carrier for a pattern and a flask for a drag flask. It fills a molding space that is formed by means of the flask, the carrier plate, and a squeeze board with molding sand to separately mold a cope and a drag. Then it assembles the cope and the drag. Molten metal is poured into the cope and the drag to manufacture a cast product. 
     If a shift occurs when the carrier for a pattern and the flask are assembled, the cavity part, which is a space to manufacture a cast product when molten metal is poured, is shifted in relation to the flask. Thus a shift between the cavity part of the cope and that of the drag occurs when the cope flask and drag flask are assembled. Incidentally, the term “a shift in cavity parts” means a shift between a cavity part of a cope and that of a drag, unless otherwise stated. Further, if a shift occurs between a cope flask and a drag flask when they are assembled, a shift occurs between the cope and the drag even when the positions of the cavity parts are at their set positions in the cope and the drag. Thus, a shift occurs between the cavity part of the cope and that of the drag. A shift in cavity parts causes a cast product to be defective. Therefore, a method has been provided to prevent a shift between a carrier for a pattern and a flask and between a cope flask and a drag flask, wherein a pin and a bushing are provided to a carrier for a pattern and a flask, to fit the pin with the bushing. 
     However, since a carrier for a pattern and a flask are repeatedly used, a pin or a bushing may be worn out, so that a shift may easily occur. Thus, to analyze molding information, a system was proposed to detect the degree of wear of a pin and a bushing of the flasks during the operation of a line for the molding so that the data on the degree are sent through a network to be monitored (see Patent Literature 1). 
     However, the pin and bushing may not be uniformly worn out. Thus, when they are worn out a shift between the cavity parts does not always occur. 
     Thus, the object of the present invention is to provide a method for preventing a defect that is caused by a shift in cavity parts, by measuring shifts between a carrier for a pattern and a flask and between a cope flask and a drag flask. 
     PRIOR-ART PUBLICATION 
     Patent Literature 
     [Patent Literature 1] 
     
         
         Japanese Patent Laid-open Publication No. 2001-321927 
       
    
     SUMMARY OF INVENTION 
     To achieve the above-mentioned object, a method for preventing a defect caused by a shift in cavity parts of a first aspect of the present invention is, for example, as in  FIGS. 2, 3, 9, and 12 , the method in molding a cope and a drag with flasks by using a cope flask  110  that is assembled with a carrier plate  130  for the cope flask and a drag flask  120  that is assembled with a carrier plate  140  for the drag flask. The method comprises a step of measuring a shift between the carrier plate  130  for the cope flask and the cope flask  110 . It also comprises a step of measuring a shift between the carrier plate  140  for the drag flask and the drag flask  120 . It also comprises a step of measuring a shift between the cope flask  110  and the drag flask  120  that have been assembled. It also comprises a step of determining if a shift in cavity parts is within an allowable range, wherein the data on the shift is obtained based on the shift between the carrier plate  130  for the cope flask and the cope flask  110 , the shift between the carrier plate  140  for the drag flask and the drag flask  120 , and the shift between the cope flask  110  and the drag flask  120 , that have been assembled. 
     By the above configuration, since any shift in the cavity parts is determined to see if it is within an allowable range, wherein the data on the shift is obtained based on the measured shifts between the carrier plates for the cope and drag flasks and the cope and drag flasks and the measured shift between the cope flask and the drag flask that have been assembled, a defect caused by a shift in cavity parts can be prevented. 
     By the method for preventing a defect caused by a shift in cavity parts of a second aspect of the present invention, for example, as in  FIGS. 2, 3, 9, and 12 , the carrier plate  130  for the cope flask and the cope flask  110  may be positioned in relation to each other by means of a male jig  112  for the positioning and a female jig  132  for the positioning. The carrier plate  140  for the drag flask and the drag flask  120  may be positioned in relation to each other by means of a male jig  142  for the positioning and a female jig  122  for the positioning. The cope flask  110  and the drag flask  120  are positioned in relation to each other by means of a male jig  112  for the positioning and a female jig  122  for the positioning. By this configuration, since the cope and drag flasks and the carrier plates for the cope and drag flasks and the cope and drag flasks are positioned by means of the male jigs for the positioning and the female jigs for the positioning, a shift cannot easily occur, to thus prevent a defect caused by the shift in the cavity parts. 
     The method for preventing a defect caused by a shift in cavity parts of a third aspect of the present invention, for example, as in  FIGS. 5, 6, and 7 , may further comprise a step of measuring a degree of wear of the male jig  112 ,  142  for the positioning or the female jig  122 ,  132  for the positioning of any of the carrier plate  130  for the cope flask, the cope flask  110 , the carrier plate  140  for the drag flask, and the drag flask  120 . By this configuration, since the degree of wear of the male jig for the positioning or the female jig for the positioning is measured, whether the shift occurs due to wear can be found. 
     By the method for preventing a defect caused by a shift in cavity parts of a fourth aspect of the present invention, for example, as in  FIGS. 5, 6, and 7 , an outer periphery of the male jig  112 ,  142  for the positioning or an inner periphery of the female jig  122 ,  132  for the positioning may be measured in the step of measuring the degree of wear. By this configuration, since the outer periphery of the male jig for the positioning or the inner periphery of the female jig for the positioning is measured to find the degree of the wear, the degree of the wear can correctly be measured even when the jigs are unevenly worn out. 
     The method for preventing a defect caused by a shift in cavity parts of a fifth aspect of the present invention, for example, as in  FIG. 12 , may further comprise a step of generating an alarm if the degree of wear of the male jig  112 ,  142  for the positioning or the female jig  122 ,  132  for the positioning is outside the allowable range. By this configuration, since an alarm is generated if the degree of wear of the male jig for the positioning or the female jig for the positioning is outside the allowable range, the state wherein the degree of wear is great can be found. 
     The method for preventing a defect caused by a shift in cavity parts of a sixth aspect of the present invention, for example, as in  FIG. 12 , may further comprise a step of linking the degree of wear of the male jig  112  for the positioning or the female jig  122  for the positioning to the cope flask  110  or the drag flask  120  that has that male jig  112  for the positioning or that female jig  122  for the positioning, so as to find a flask in which the male jig  112  for the positioning or the female jig  122  for the positioning should be exchanged during the maintenance of a line for molding a cope and a drag with flasks. By this configuration, since a cope flask or a drag flask of which the male jig for the positioning or the female jig for the positioning has been worn out can be easily found, an inspection and an exchange can effectively be carried out. 
     The method for preventing a defect caused by a shift in cavity parts of a seventh aspect of the present invention, for example, as in  FIG. 12 , may further comprise a step of comparing respective shapes that have been found based on the measured values on the outer periphery of the male jig  112 ,  142  for the positioning and on the inner periphery of the female jig  122 ,  132  for the positioning with at least one of the measured shift between the carrier plate  130  for the cope flask and the cope flask  110 , the measured shift between the carrier plate  140  for the drag flask and the drag flask  120 , and the measured shift between the cope flask  110  and the drag flask  120 , that have been assembled. By this configuration, the validation of the result of the measured shift can be judged based on the comparison of the shape of the male jig for the positioning or the female jig for the positioning with the shift. 
     The present invention comprises the steps of measuring a shift between a carrier plate for a cope flask and the cope flask, measuring a shift between a carrier plate for a drag flask and the drag flask, measuring a shift between the cope flask and the drag flask that have been assembled, and determining if a shift in cavity parts is within an allowable range, wherein the data on the shift is obtained based on the shift between the carrier plate for the cope flask and the cope flask, the shift between the carrier plate for the drag flask and the drag flask, and the shift between the cope flask and the drag flask that have been assembled. Thus, the shift in cavity parts is found based on the measurements on the shift between the cope and drag flasks and the carrier plate and on the shift between the cope and drag flasks that have been assembled, to determine if it is within the allowable range. Thereby, a defect that is caused by the shift in cavity parts can be prevented. 
     The basic Japanese patent application, No. 2018-030258, filed Feb. 23, 2018, is hereby incorporated by reference in its entirety in the present application. 
     The present invention will become more fully understood from the detailed description given below. However, the detailed description and the specific embodiments are only illustrations of the desired embodiments of the present invention, and so are given only for an explanation. Various possible changes and modifications will be apparent to those of ordinary skill in the art on the basis of the detailed description. 
     The applicant has no intention to dedicate to the public any disclosed embodiment. Among the disclosed changes and modifications, those which may not literally fall within the scope of the present claims constitute, therefore, a part of the present invention in the sense of the doctrine of equivalents. 
     The use of the articles “a,” “an,” and “the” and similar referents in the specification and claims are to be construed to cover both the singular and the plural form of a noun, unless otherwise indicated herein or clearly contradicted by the context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein is intended merely to better illuminate the invention, and so does not limit the scope of the invention, unless otherwise stated. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a plan view illustrating a line for the molding. 
         FIG. 2  is a partial and sectional side view illustrating the formation of a molding space in a cope flask by a molding machine. 
         FIG. 3  is a partial and sectional side view illustrating the formation of a molding space in a drag flask by a molding machine. 
         FIG. 4  is a partial plan view illustrating the measurement of a shift between the carrier plate and the flask in the molding machine. 
         FIG. 5  is a side view illustrating the measurement of the degree of wear of the pin (the male jig for the positioning) of the cope flask. 
         FIG. 6  is a side view illustrating the measurement of the degree of wear of the pin (the male jig for the positioning) of the cope flask. It is shown in a direction that is perpendicular to that in  FIG. 5 . 
         FIG. 7  is a side view illustrating the measurement of the degree of wear of the bushing (the female jig for the positioning) of the drag flask. 
         FIG. 8  is a side view illustrating the measurement of the degree of wear of the bushing (the female jig for the positioning) of the drag flask. It is shown in a direction that is perpendicular to that in  FIG. 7 . 
         FIG. 9  is a side view illustrating the mold assembling of the cope and drag flasks and the measurement of a shift between the cope flask and the drag flask by a mold-assembling device. 
         FIG. 10  is a side view illustrating the mold assembling of the cope and drag flasks and the measurement of a shift between the cope flask and the drag flask by a mold-assembling device. It is shown in a direction that is perpendicular to that in  FIG. 9 . 
         FIG. 11  is a plan view illustrating the mold assembling of the cope and drag flasks and the measurement of a shift between the cope flask and the drag flask by a mold-assembling device. It is viewed along the arrows A-A in  FIG. 9 . 
         FIG. 12  is a flowchart of the method for preventing a defect caused by a mold shift. The flowchart is divided into three drawings, (a), (b), and (c). 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Below the embodiments of the present invention are discussed with reference to the drawings. In the drawings, the same or corresponding members are denoted by the same reference numbers. Thus, duplicate descriptions are omitted. First, with reference to  FIG. 1 , an embodiment of a line for molding molds is discussed. The line  1  for the molding alternately molds a cope and a drag with flasks. In the drawing, the arrow defined by the outline denotes the direction to convey the molds or the flasks. The same denotation is applicable to the other drawings. 
     In the line  1  for the molding, a molding machine  10  is provided that molds the cope and drag (the mold) from molding sand. A pouring machine  30  is also provided that pours molten metal into the mold. A shake-out machine  40  is also provided that breaks the mold to separate a cast product from the molding sand after the molten metal has been cooled and has solidified to form a cast product. Between the machines  10 ,  30 ,  40 , the mold is conveyed by a roller conveyor, which is not shown, or transported by being mounted on a carriage  50  with a molding board. A plurality of the carriages  50  with a molding board are arranged on rails (not shown) that are disposed in parallel. The carriages  50  with a molding board, which form a line, are pushed out by a pusher  52  that is provided at the end of a side for pushing out. Thus the carriages  50  with a molding board in a line, i.e., the cope and drag  100 , are transported by a distance that is equal to the length of a mold. Incidentally, a cushion  54  that shrinks when the pusher  52  pushes is preferably provided at the end of a side for taking out, to sandwich the carriages  50  with a molding board in a line. By so doing the carriage  50  with a molding board is stable during the transportation. 
     Traversers  56  are provided at both ends of the line of the carriages  50  with a molding board to transfer the carriage  50  to a rail that is parallel to and next to the rail on which the carriages  50  are arranged. The carriage  50  with a molding board that comes to the end of the line is transferred to the head of the line of the carriages  50  on the next rail by means of the traversers  56 . 
     In the line  1  for the molding, a roll-over machine  82  is provided that inverts the mold (the two pieces, the cope and the drag) that has been molded by the molding machine  10 , i.e., upside down (roll over it about an axis that runs in a direction to transport the flasks), so that the mold upwardly faces the cavity parts. In the line  1  for the molding, a sand cutter  84  is further provided to remove excess sand on the surfaces of the cavities of the cope and the drag. The sand cutter  84  may treat only the drag. In the line  1  for the molding, a sprue-forming machine  86  that forms a sprue in the cope is further provided. In the line  1  for the molding, a machine  88  for re-rolling over the cope flask is provided to re-roll over the cope (re-roll over it about an axis that runs in a direction to transport the flasks), so that its cavity part faces downwardly, to be placed on the drag. In the line  1  for the molding, a mold-assembling device  20  is provided so that the drag is mounted on the carriage  50  with a molding board so that the cope that has been rolled over by means of the machine  88  for re-rolling over the cope flask is placed on the drag, and so that the cope and drag  100  are formed. 
     Molten metal is poured into the cope and drag  100  that are transported on the line  1  for the molding from the pouring machine  30 . The cope and drag  100  into which molten metal has been poured are transported for a set distance. While they are transported for a set time, the molten metal that has been poured is cooled and solidifies, to form a cast. The cope and drag  100  in which the molten metal has solidified are drawn out from the cope and drag flasks (collectively called “the flask”) by the shake-out machine  40 . They are further broken so that a cast is taken out and the molding sand is sent to a device for sand preparation (not shown). The cope flask and the drag flask are alternately arranged by a machine  42  for separating the flask, to be returned to the molding machine  10 . 
     Next, with reference to  FIGS. 2 and 3 , molding by the molding machine  10  is discussed.  FIG. 2  is a partial and sectional view illustrating the formation of a molding space in the cope flask  110  by the molding machine  10 . A pattern plate  136  for the cope flask to which a pattern  134  for the cope flask is fixed is fixed on the carrier plate  130  for the cope flask. The cope flask  110  is placed on it. In the present embodiment, the carrier plate  130  for the cope flask has a leveling frame  138  for the cope flask that is a frame that surrounds, and vertically slides on, the pattern plate  136 . A plurality of guide pins  139  are connected to the lower part of the leveling frame  138  for the cope flask. They are vertically and slidably inserted in the main body of the carrier plate  130  for the cope flask. The leveling frame  138  for the cope flask is vertically moved by a vertical cylinder, which is not shown, via the guide pins  139 . A bushing  132  of the carrier plate for the cope flask, which is the female jig for the positioning of the carrier plate  130  for the cope flask, is attached to the leveling frame  138  for the cope flask. By inserting a pin  112  for the cope flask, which is the male jig for the positioning of the cope flask  110 , into the bushing  132  of the carrier plate for the cope flask, a shift between the carrier plate  130  for the cope flask and the cope flask  110  is prevented. However, after they are repeatedly used, the pin  112  for the cope flask or the bushing  132  of the carrier plate for the cope flask may be worn out, to cause a shift. 
     Typically, the bushing  132  of the carrier plate for the cope flask is a hole having a circular section and the pin  112  for the cope flask is a shaft having a circular section, the diameter of which decreases toward the tip. When the pin  112  for the cope flask is inserted into the bushing  132  of the carrier plate for the cope flask, a part of the pin  112  for the cope flask is preferably engaged with the bushing  132  of the carrier plate for the cope flask so that no rattle occurs. However, the shapes of the bushing  132  of the carrier plate for the cope flask and the pin  112  for the cope flask are not necessarily those mentioned above. They may have an arbitrary section, such as an elliptical, rectangular, or polygonal shape if the pin  112  for the cope flask can be inserted into the bushing  132 , and engages with, the bushing  132  of the carrier plate for the cope flask, so that no rattle occurs. The bushing  132  of the carrier plate for the cope flask may be attached to a part that projects from the carrier plate  130  for the cope flask. Incidentally, the shape of the bushing  132  of the carrier plate for the cope flask and the shape of the pin  112  for the cope flask that are above discussed can be applied to the other female jig for the positioning (the bushing) and the other male jig for the positioning (the pin). 
     An auxiliary flask  18  is placed on the cope flask  110 . A squeeze board  16  is inserted inside the auxiliary flask  18 . A nozzle  14  for filling the molding sand is formed in the squeeze board  16  so that molding sand (not shown) in a hopper  19  for filling the molding sand that is located above the squeeze board  16  is supplied to the molding space in the cope flask  110 . After the molding sand has been supplied to the molding space in the cope flask  110 , the squeeze board  16  is lowered to squeeze the molding sand between it and the pattern plate  136  for the cope flask, to form a mold. A part that corresponds to the pattern  134  for the cope flask becomes a void space. That is, a space (the cavity part of the cope) is formed that will be a part of a product when the cope flask  110  and the drag flask  120  are assembled. By pouring molten metal into that space, a cast is manufactured. Incidentally, by lowering the leveling frame  138  for the cope flask during the squeezing, the molding sand is advantageously squeezed from the side of the pattern plate  136  for the cope flask. 
       FIG. 3  is a partial and sectional view illustrating the formation of a molding space in the drag flask  120  by the molding machine  10 . The pattern plate  146  for the drag flask to which the pattern  144  for the drag flask is fixed is fixed on the carrier plate  140  for the drag flask. The drag flask  120  is placed on it. Like the carrier plate  130  for the cope flask, the carrier plate  140  for the drag flask has the leveling frame  148  for the drag flask. A plurality of guide pins  149  are attached to it that move so that the leveling frame  148  is vertically moved. The pin  142  of the carrier plate for the drag flask, which is the male jig for the positioning of the carrier plate  140  for the drag flask, is fixed to the leveling frame  148  for the drag flask. By inserting the pin  142  of the carrier plate for the drag flask in the bushing  122  for the drag flask, which is the female jig for the positioning of the drag flask  120 , a shift between the carrier plate  140  for the drag flask and the drag flask  120  is prevented. However, a shift may occur as discussed above. 
     The auxiliary flask  18  is placed on the drag flask  120 . The squeeze board  16  is inserted inside the auxiliary flask  18 . The nozzle  14  for filling the molding sand is formed in the squeeze board  16  so that molding sand (not shown) in a hopper  19  for filling the molding sand that is located above the squeeze board  16  is supplied to the molding space in the drag flask  120 . After the molding sand has been supplied to the molding space in the drag flask  120 , the squeeze board  16  is lowered to squeeze the molding sand between it and the pattern plate  146  for the drag flask, to form a mold. The part that corresponds to the pattern  144  for the drag flask becomes a void space. That is, a space (the cavity part of the cope) is formed that will be a part of a product when the cope flask  110  and the drag flask  120  are assembled. By pouring molten metal into that space, a cast is manufactured. Incidentally, by lowering the leveling frame  148  for the drag flask during the squeezing, the molding sand is advantageously squeezed from the side of the pattern plate  146  for the drag flask. The molding machine  10  alternately molds a cope and a drag. 
     A sensor  12  is provided to the molding machine  10 , to measure a shift between the carrier plate  130  for the cope flask and the cope flask  110  or between the carrier plate  140  for the drag flask and the drag flask  120 . The sensor  12  may be a publicly-known displacement sensor, such as a laser displacement sensor, an infrared displacement sensor, or a contact displacement sensor. Since measuring the position of the pattern is difficult, the positions of the carrier plate and the flask are measured, to estimate a shift between the pattern and the flask. The shift between the carrier plate  130  for the cope flask and the cope flask  110  or between the carrier plate  140  for the drag flask and the drag flask  120  is normally measured before molding. However, it may also be measured after the squeezing. A shift between the carrier plate and the flask may occur during the squeezing. By measuring the shift before and after the squeezing, the bushing  132  and the pin  142  for the carrier plates for the cope and drag flasks or the pin  112  and the bushing  122  for the cope and drag flasks, or both, may be found to be worn out. 
     As in the plan view of  FIG. 4 , three sensors  12  for the flask are provided. In the same way, three sensors  12  for the carrier plate are provided. Incidentally, the three sensors may be vertically moved to measure the positions of both the flask and the carrier plate. Since three sensors  12  are provided, three respective distances to the flask or the carrier plate can be measured. Since the coordinates of the three sensors  12  are known, the coordinates of the three points of the flask and those of the carrier plate can be found. When the coordinates of the three points are found, the positions of the centers and the angles of rotations in the horizontal plane of the flask and the carrier plate can be calculated, since the shapes of them are known. The shift between the flask and the carrier plate can be determined based on the shifts between the positions of the centers and the angles of rotation in the horizontal plane that have been calculated or based on the coordinates of the corners of the flask and the carrier plate that have been calculated based on the positions of the centers and the angles of rotation. Since the shapes of the flask and the carrier plate are known, the shift between the flask and the carrier plate can be accurately found. 
     A shift between the flask and the carrier plate is prevented by inserting the pin  112  for the cope flask into the bushing  132  of the carrier plate for the cope flask and by inserting the pin  142  of the carrier plate for the drag flask into the bushing  122  for the drag flask. However, the pin  112  for the cope flask, the bushing  132  of the carrier plate for the cope flask, the pin  142  of the carrier plate for the drag flask, or the bushing  122  for the drag flask, may be worn out after being repeatedly used, so that a shift occurs. 
     Therefore, the degree of the wear of the pin and the bushing is measured.  FIGS. 5 and 6  are side views illustrating the measurement of the degree of wear of the pin  112  for the cope flask by means of a device  60  for measuring the degree of wear of the pin. Since two pins  112  for the cope flask are normally provided to the cope flask  110 , the degrees of wear of the two pins  112  for the cope flask are measured by two respective pdevices  60  for measuring the degrees of wear of the pins. However, the number of pins is not limited to two and the number of devices  60  for measuring the degrees of wear of the pins is not limited to two. In the device  60  for measuring the degrees of wear of the pins, the pin  112  for the cope flask is positioned, for example, in a holder  64  for the sensor that has an open top. The pin  112  for the cope flask is preferably positioned concentrically with the holder  64  for the sensor. The sensor  62  that measures the coordinates of the surface of the pin  112  for the cope flask is located at a set height of the holder  64  for the sensor. The set height is a height to measure a part of the pin  112  for the cope flask that engages with the bushing  132  of the carrier plate for the cope flask or the bushing  122  for the drag flask. In  FIG. 6  the holder  64  for the sensor has two sensors  62 . However, the number of sensors  62  may be just one or three or more. The sensor  62  may be a publicly-known displacement sensor, such as a laser displacement sensor, an infrared displacement sensor, or a contact displacement sensor. The holder  64  for the sensor is held by a rotary actuator  66  to be rotated about the pin  112  for the cope flask. The rotary actuator  66  is fixed by a holder  68  for the device for the measurement. 
     By the device  60  for measuring the degree of wear of the pin, the coordinates of the entire circumference of the pin  112  for the cope flask can be measured by means of the sensor  62 , since the holder  64  for the sensor is rotated about the pin  112  for the cope flask. That is, the degree of wear of the entire circumference of the pin  112  for the cope flask can be measured. For example, the maximum degree of wear is assumed to be the degree of wear of the pin  112  for the cope flask. Alternatively, the average of the measured degrees of wear or the degree of wear at an arbitrary position may be used. The measured degrees of wear are preferably stored with a link to the cope flask  110 . 
       FIGS. 7 and 8  are side views illustrating the measurement of the degree of wear of the bushing  122  for the drag flask of the drag flask  120  by means of a device  70  for measuring the degree of wear of the bushing. Two bushings  122  for the drag flask are provided in conformity with two pins  112  for the cope flask. Also, two devices  70  for measuring the degree of wear of the bushing are provided. However, the number of bushings is not limited to two and the number of devices  70  for measuring the degree of wear of the bushing is also not limited to two. In the device  70  for measuring the degree of wear of the bushing, a sensor  72  that is directed to measure the inner surface of the bushing  122  for the drag flask is supported by a holder  74  for the sensor. The sensor  72  may be a publicly-known displacement sensor, such as a laser displacement sensor, an infrared displacement sensor, or a contact displacement sensor. By using a displacement sensor, the sensor  72  that is located obliquely below the bushing  122  for the drag flask can measure the inner surface of the bushing  122  for the drag flask that is located obliquely above it. The holder  74  for the sensor is held by the rotary actuator  76  to be rotated about the bushing  122  for the drag flask. The rotary actuator  76  is fixed directly below the bushing  122  for the drag flask by means of a holder  78  for the device for the measurement. 
     By the device  70  for measuring the degree of wear of the bushing, the coordinates of the entire inner circumference of the bushing  122  for the drag flask can be measured by means of the sensor  72 , since the holder  74  for the sensor is rotated about the bushing  122  for the drag flask. That is, the degree of wear of the entire inner circumference of the bushing  122  for the drag flask can be measured. For example, the maximum degree of wear is assumed to be the degree of wear of the bushing  122  for the drag flask. Alternatively, the average of the measured degrees of wear or the degree of wear at an arbitrary position may be used. The measured degrees of wear are preferably stored with a link to the drag flask  120 . 
     The degrees of wear of the pin  112  for the cope flask and the bushing  122  for the drag flask are preferably measured at the positions P 1  and P 2  of the flask as in  FIG. 1 . That is, the device  60  for measuring the degree of wear of the pin and the device  70  for measuring the degree of wear of the bushing are preferably located upstream of the molding machine  10 . 
     About the carrier plate  140  for the drag flask, the degree of wear of the pin  142  of the carrier plate for the drag flask is measured in the same way as that discussed about the pin  112  for the cope flask with reference to  FIGS. 5 and 6 . About the carrier plate  130  for the cope flask, the degree of wear of the bushing  132  of the carrier plate for the cope flask is measured in the same way as that discussed about the bushing  122  for the drag flask with reference to  FIGS. 7 and 8 . The degrees of wear of the pin  142  of the carrier plate for the drag flask and the bushing  132  of the carrier plate for the cope flask are preferably measured outside the flow of the molds in  FIG. 1  (outside the molding machine  10 ), i.e., before the carrier plate  130  for the cope flask and the carrier plate  140  for the drag flask are carried in the molding machine  10 . The measured degrees of wear are preferably stored with a link to the carrier plate  140  for the drag flask or the carrier plate  130  for the cope flask. 
       FIGS. 9 and 10  illustrate the mold assembling of the cope and drag flasks by the mold-assembling device  20 . The cope flask and the drag flask that have alternately been molded by the molding machine  10  are treated by means of the roll-over machine  82 , the sand cutter  84 , the sprue-forming machine  86 , and the machine  88  for re-rolling over the cope flask. Then they are assembled by means of the mold-assembling device  20 . The mold-assembling device  20  mounts the drag flask  120  on the carriage  50  with a molding board that is placed on the traversers  56  by means of a lifter  22 . The drag flask  120  houses the drag in which the cavity part faces upwardly. Next, the cope flask  110  is placed on the drag flask  120  by means of the lifter  22 . The drag flask  120  houses the cope in which the cavity part has been caused by the machine  88  for re-rolling over the cope flask to face downwardly. A shift between the cope flask  110  and the drag flask  120  is prevented by inserting the pin  112  for the cope flask, which is the male jig for the positioning of the cope flask  110 , into the bushing  122  for the drag flask, which is the female jig for the positioning of the drag flask  120 . However, the pin  112  for the cope flask or the bushing  122  for the drag flask may be worn out after being repeatedly used, so that a shift occurs. 
     Therefore, sensors  26  are provided to the mold-assembling device  20 , to measure a shift between the cope flask  110  and the drag flask  120 . The sensor  26  may be any publicly-known displacement sensor, such as a laser displacement sensor, an infrared displacement sensor, or a contact displacement sensor. The sensors  26  are held by the holder  28  for the sensor at two stages, i.e., at the up stage and at the down stage. The holder  28  for the sensor is supported by a rack  24 . However, the sensors  26  on either stage may measure both the cope flask  110  and the drag flask  120  by being vertically moved. In this case, the holder  28  for the sensor may be configured to vertically move in relation to the rack  24 . 
     As in  FIG. 11 , three sensors  26  are provided for the cope flask  110 . In the same way, three sensors  26  are provided for the drag flask  120 . Incidentally, both the cope flask  110  and the drag flask  120  are measured by three sensors that are vertically moved. Since three sensors  26  are provided, the distances to three points of the cope flask  110  or the drag flask  120  can be measured. Since the coordinates of the three sensors  26  are known, the coordinates of the three points of the cope flask  110  and those of the drag flask  120  can be found. When the coordinates of the three points are found, the positions of the centers and the angles of rotations in the horizontal plane of the cope flask  110  and the drag flask  120  can be calculated, since their shapes are known. The shift between the cope flask  110  and the drag flask  120  can be determined based on the shifts between the positions of the centers and the angles of rotation in the horizontal plane that have been calculated or based on the coordinates of the corners of the cope flask  110  and the drag flask  120  that have been calculated based on the positions of the centers and the angles of rotation. Since the shapes of the cope flask  110  and the drag flask  120  are known, the shift between them can be accurately found. 
     Next, with reference to the flowchart in  FIG. 12 , estimating the shift in cavity parts and preventing a defect caused by the shift are discussed. Incidentally, the flowchart is divided into 3 sheets, (a)-(c). The connecting points are shown by using the encircled numbers. First, as discussed with reference to  FIGS. 5-8 , the degrees of wear of the pin  112  for the cope flask, the bushing  122  for the drag flask, the bushing  132  of the carrier plate for the cope flask, and the pin  142  of the carrier plate for the drag flask, are measured (S 11 ). The data on the degrees of wear that have been measured are stored with links to the cope flask  110 , the drag flask  120 , the carrier plate  130  for the cope flask, and the carrier plate  140  for the drag flask. For example, they are stored in a controller (not shown) for the line for the molding. 
     Next, as discussed with reference to  FIGS. 2-4 , the shifts X, Y (X and Y are shifts in two horizontal directions that are perpendicular to each other) between the cope flask  110  and the carrier plate  130  for the cope flask and the shifts X′, Y′ (X′ and Y′ are shifts in two horizontal directions that are perpendicular to each other) between the drag flask  120  and the carrier plate  140  for the drag flask are measured by the molding machine  10  (S 12 ). Next, as discussed with reference to  FIGS. 9-11 , the shifts x, y (x and x are shifts in two horizontal directions that are perpendicular to each other) between the cope flask  110  and the drag flask  120  that have been assembled are measured by means of the mold-assembling device  20 , where the shifts are measured as shifts of the cope flask  110  in relation to the lower flask  120  (S 13 ). Incidentally, the shifts X, Y, X′, Y′, x, y may be shifts of the coordinates of the corners, that is, the maximum values or average values of the shifts of the coordinates of four corners, or shifts of an arbitrary corner among four corners. 
     Next, it is determined if the shifts are within the allowable range (S 14 ). Thus it is determined if the relationships |(X−X′)−x|≤0.3, |(Y+Y′)−y|≤0.3 are fulfilled. The value “0.3” at the right hand denotes the allowable value, 0.3 mm. However, the allowable value is not limited to 0.3 mm, since it is determined based on a shape, a size, an application, etc., of a cast. The “(X−X′)” calculates the difference between the shift X, which is the shift between the cope flask  110  and the carrier plate  130  for the cope flask, and the shift X′, which is the shift between the drag flask  120  and the carrier plate  140  for the drag flask. If the direction of the shift of the cope flask  110  in relation to the carrier plate  130  for the cope flask (i.e., the cavity part for the cope flask) is the same as that of the drag flask  120  in relation to the carrier plate  140  for the drag flask (i.e., the cavity part for the drag flask), then the shifts in the cavity parts are canceled out when the cope and drag flasks are assembled. Thus, the difference between the shift X and the shift X′ is assumed to be the shift in cavity parts. By the present embodiment, since the drag flask  120  is not subject to re-rolling over, the direction of X′ (a direction of a shift between the cope flask  110  and the drag flask  120  in a direction to transport the flasks) is not changed. About the direction of Y′ (the direction of the shift between the cope flask  110  and the drag flask  120  in a direction that is perpendicular to the direction to transport the flasks), since the direction of the shift of the cope flask  110  is reverse to that of the drag flask  120 , the sum of the shift Y between the cope flask  110  and the pattern  134  for the cope flask and the shift Y′ between the drag flask  120  and the pattern  144  for the drag flask is used. In both calculations, the shifts between the patterns  134 ,  144  for the cope and drag flasks and the cope and drag flasks  110 ,  120  are found. By using the formulae |(X−X′)−x|, |(Y+Y′)−y| the absolute values of the shifts in cavity parts are calculated by reducing the shifts x, y between the cope flask  110  and the drag flask  120  from the shifts between the patterns  134 ,  144  for the cope and drag flasks and the cope and drag flasks  110 ,  120 . It is determined if those shifts are within the allowable value, 0.3 mm. 
     By this configuration, the results of measurements of the shifts between the cope and drag flasks  110 ,  120  and the patterns  134 ,  144  for the cope and drag flasks and the results of measurements of the shifts between the cope flask  110  and the drag flask  120  are combined to find the shifts in cavity parts, to determine if a defect that is caused by the shift occurred. That is, the reliability in determining an occurrence of a defect increases compared to where the shift is determined based only on a shift between the cope flask  110  and the drag flask  120  that have been assembled. Thus determining to be a defect even when no defective product will be manufactured can be prevented, so that the waste of many molds is prevented. 
     Next, with reference to  FIG. 12( b ) , the operations that are carried out when the above operations determine that no shift has occurred are discussed. Since no shift occurs, molten metal is poured into the mold as usual (S 20 ). It is determined if the degrees of wear of the pin  112  of the cope flask  110  and the bushing  122  of the drag flask  120  are within the allowable range (0.3 mm or less) (S 21 ). Even if no shift between the cope and drag flasks  110 ,  120  occurs, an instruction for the exchange is displayed on a panel, etc., if the degree of wear of the pin  112  or the bushing  122  exceeds the allowable range (S 22 ). Next, it is determined if the degrees of wear of the bushing  132  of the carrier plate  130  and the pin  142  of the carrier plate  140  are within the allowable range (0.3 mm or less) (S 23 ). Even if no shift between the cope and drag flasks  110 ,  120  occurs, an instruction for the exchange is displayed on a panel, etc., if the degree of wear of the bushing  132  or the pin  142  exceeds the allowable range (S 24 ). 
     The degree of wear of the pin  112  of the cope flask  110  is stored with a link to the cope flask  110  (as data to be shifted of the cope flask  110 ). The degree of wear of the bushing  122  of the drag flask  120  is stored with a link to the drag flask  120  (as data to be shifted of the drag flask  120 ). The degree of wear of the bushing  132  of the carrier plate  130  for the cope flask is stored with a link to the carrier plate  130  for the cope flask (as data to be shifted of the carrier plate  130  for the cope flask). The degree of wear of the pin  142  of the carrier plate  140  for the drag flask is stored with a link to the carrier plate  140  for the drag flask (as data to be shifted of the carrier plate  140  for the drag flask) (S 25 ). The term “data to be shifted” means data that include data on the cope flask, the drag flask, the carrier plate for the cope flask, or the carrier plate for the drag flask, and are shifted in conformity with their movements. That is, they are the data that are linked with the cope flask, the drag flask, the carrier plate for the cope flask, or the carrier plate for the drag flask. In this way the data on the degrees of wear are managed for each of the cope flask, the drag flask, the carrier plate for the cope flask, and the carrier plate for the drag flask, so that a part that has been worn out can quickly be exchanged during the maintenance of the line  1  for the molding. Thus an inspection and an exchange can effectively be carried out. Then, the next cycle, i.e., a next molding, is carried out (S 26 ). 
     Next, with reference to  FIG. 12( c ) , the operations that are carried out when the above operations determine that a shift has occurred are discussed. First, though the shift in the cavity parts has occurred, it is determined if molten metal should be poured (S 30 ). There is a case where molten metal is poured into a mold where a shift has occurred. In this case an instruction for carefully inspecting a cast product is generated (S 32 ), to carefully inspect a cast product to find a problem in using it. If no molten metal is poured, then one mold is short. Thus an instruction for additional molding is sent to the molding machine  10  (S 31 ). 
     It is determined if the degrees of wear of the pin  112  of the cope flask  110  and the bushing  122  of the drag flask  120  are within the allowable range (0.3 mm or less) (S 34 ). If the degree of wear of the pin  112  or the bushing  122  exceeds the allowable range, an instruction for the exchange is displayed on a panel, etc. (S 35 ). Next, it is determined if the degrees of wear of the bushing  132  of the carrier plate  130  and the pin  142  of the carrier plate  140  are within the allowable range (0.3 mm or less) (S 36 ). If the degree of wear of the pin  142  or the bushing  132  exceeds the allowable range, an instruction for the exchange is displayed on a panel, etc. (S 37 ). 
     Next, it is determined if either the degrees of wear of the pin  112  and the bushing  122  or those of the pin  142  and the bushing  132  are within the allowable range (determined as YES) (S 38 ). If the degree of wear of the pin  112  or the bushing  122  and that of the pin  142  or the bushing  132  exceed the allowable range (determined as NO), the cause of the shift in cavity parts is estimated as wear of the pin or the bushing. The instructions for the exchange of the pin or the bushing has been displayed on the panel, etc., and so an operator has been alerted. 
     If either or both of the degrees of wear of the pin  112  and the bushing  122  and those of the pin  142  and the bushing  132  are within the allowable range (if YES at S 38 ), a shift is considered to have occurred for a reason that is specific to that mold (for example, being unevenly worn out) or by accident. Thus, it is determined if such a phenomenon often occurs when using the same flask or the same carrier plate (S 39 ). That is, the number of accumulated times this step was carried out when using a specific flask or carrier plate may be, for example, ten or less. If it is over ten (if NO at S 39 ), a defect may exist in the pin or the bushing of the flask or the carrier plate. Thus an instruction for the inspection or the exchange of the pin or the bushing of the flask or the carrier plate is displayed on the panel, etc., (S 40 ). 
     Incidentally, the number of continuous times, not accumulated times, may be used for determining if the phenomenon occurs when using a specific flask or carrier plate. Alternatively, the ratio of the number of times to carry out that step to the total number when using a specific flask or carrier plate may be used. For example, if the ratio exceeds 10%, an instruction for the inspection or the exchange of the pin or the bushing of the flask or the carrier plate is displayed on the panel, etc. Incidentally ten or 10% is just an example, and another number may be used. 
     Next, in the same way as discussed above, the results of the measurements of the degrees of wear of the pin and the bushing of the flasks and the carrier plates are stored as data to be shifted. By this, the flask or the carrier plate that has been inspected or exchanged during the maintenance can quickly be found, so that an inspection and an exchange can effectively be carried out (S 41 ). Then, the next cycle, i.e., a next molding, is carried out (S 42 ). 
     As discussed with reference to  FIGS. 5-8 , since the circumference of the pin  112  for the cope flask, of the bushing  122  for the drag flask, of the bushing  132  of the carrier plate for the cope flask, and of the pin  142  of the carrier plate for the drag flask, are measured, the shapes of the pin and the bushing are determined. Thus, for example, it can be judged if a large shift is determined to have occurred even when the pin or the bushing has not substantially been worn out. In such a case the device  60  for measuring the degree of wear of the pin or the device  70  for measuring the degree of wear of the bushing may not correctly work. Alternatively, a part for attaching the sensor  12 ,  26  that has measured the shift may be unusual. Thus, a step of comparing the respective shapes of the pin and the bushing with the measured shift is effective. Incidentally, by the above discussion, a shift between the flask and the carrier plate and between the cope and drag flasks is prevented by means of the pin and the bushing. However, the shift may be prevented by another known method (for example, by a convex bushing and a concave bushing). 
     By the method for estimating the shift in cavity parts and preventing a defect caused by the shift of the present invention, the shift in cavity parts is determined based on the shift between the flasks and the carrier patterns for the cope and drag flasks and the shift between the cope and drag flasks, to determine if a defect that is caused by the shift occurs. Thus, the reliability in determining an occurrence of a defect increases, to decrease the waste of molds. Further, since the data on the degrees of wear of the pins and bushings are managed as data to be shifted, a part that has been worn out can be quickly and efficiently exchanged, to efficiently operate the line for molding. 
     Below, the main reference numbers that are used in the specification and the drawings are listed.
       1  the line for the molding     10  the molding machine     12  the sensor     14  the nozzle for filling the molding sand     16  the squeeze board     18  the auxiliary flask     19  the hopper for filling the molding sand     20  the mold-assembling device     22  the lifter     24  the rack     26  the sensor     28  the holder for the sensor     30  the pouring machine     40  the shake-out machine     42  the machine for separating the flask     50  the carriage with a molding board     52  the pusher     54  the cushion     56  the traverser     60  the device for measuring the degree of wear of the pin     62  the sensor     64  the holder for the sensor     66  the rotary actuator     68  the holder for the device for the measurement     70  the device for measuring the degree of wear of the bushing     72  the sensor     74  the holder for the sensor     76  the rotary actuator     78  the holder for the device for the measurement     82  the roll-over machine     84  the sand cutter     86  the sprue-forming machine     88  the machine for re-rolling over the cope flask     100  the cope and drag     110  the cope flask     112  the pin of the cope flask (the male jig for the positioning)     120  the drag flask     122  the bushing for the drag flask (the female jig for the positioning)     130  the carrier plate for the cope flask     132  the bushing of the carrier plate for the cope flask (the female jig for the positioning)     134  the pattern for the cope flask     136  the pattern plate for the cope flask     138  the leveling frame for the cope flask     139  the guide pin     140  the carrier plate for the drag flask     142  the pin of the carrier plate for the drag flask (the male jig for the positioning)     144  the pattern for the drag flask     146  the pattern plate for the drag flask     148  the leveling frame for the drag flask     149  the guide pin