Press machine and method for detecting abnormalities in a press machine

Abstract

To provide a press machine or the like capable of detecting abnormality of a mold.SOLUTION: A press machine includes a detection part for detecting a load value in performing press working to a material to be pressed, a storage part for storing the load value detected by the detection part in association with identification information of the mold mounted on the press machine at the time of detecting the load value, a calculation part for calculating the position of a load center acting on the press machine on the basis of the stored load value, calculating the calculated position of the load center as eccentricity from the center of the press machine to acquire an eccentric load, and generating distribution data of the eccentric load of each mold, a determination part for determining abnormality on the basis of the eccentric load acquired on the basis of the load value detected by the detection part, and the distribution data of the eccentric load corresponding to the mold mounted on the press machine at the time of detecting the load value, and a notification part for giving a notification on the abnormality on the basis of a determination result of the determination part.SELECTED DRAWING: Figure 1

Description

Technical Field

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[0001] The present invention relates to a press machine and a method for detecting an abnormality in the press machine.

Background Art

[0002] Conventionally, a method is known in which a press load during press working is detected, an eccentricity amount is calculated based on the detected press load, and when the detected press load exceeds a press load allowable amount (range of an allowable eccentricity load diagram determined by the manufacturer for each press) based on the calculated eccentricity amount, it is determined that there is a press abnormality (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The above conventional method is a function for protecting the press machine. On the other hand, a user of the press machine needs to manage the state of the mold and the precision of the molded product in addition to press protection, and when an abnormality in the mold or a defect in the product precision occurs, it is necessary to detect it early and take measures. Since abnormalities in the mold and defects in product precision mainly occur within the range of the allowable eccentricity load diagram, it is difficult to detect abnormalities in the mold and defects in product precision and the like by the conventional method.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a press machine and a method for detecting an abnormality in the press machine capable of detecting an abnormality in the mold.

Means for Solving the Problems

[0007] Furthermore, the method for detecting abnormalities in a press machine according to the present invention is characterized by including: a detection step of detecting a load value when press working is performed on a workpiece; a storage step of storing the load value detected in the detection step in association with identification information of a die attached to the press machine at the time the load value is detected; a calculation step of calculating the position of the load center acting on the press machine based on the stored load value, calculating the position of the load center as the eccentricity from the center of the press machine to determine the eccentric load, and generating eccentric load distribution data for each die; a determination step of determining an abnormality based on the eccentric load determined based on the load value detected in the detection step and the eccentric load distribution data corresponding to the die attached to the press machine at the time the load value is detected; and a notification step of notifying the abnormality based on the determination result of the determination step.

[0008] According to the present invention, the load value detected by the detection unit is stored in association with the identification information of the die attached to the press machine at the time of detection. The position of the load center acting on the press machine is calculated from the stored load value. The calculated position of the load center is calculated as the eccentricity from the center of the press machine to determine the eccentric load and generate eccentric load distribution data for each die. By determining an abnormality based on the eccentric load determined based on the load value detected by the detection unit and the eccentric load distribution data corresponding to the die attached to the press machine at the time of load value detection, it becomes possible to detect abnormalities in the die. Here, the load center means the center of gravity of the load. The center of the press machine means the position of the center of the slide on a plane perpendicular to the direction in which the slide moves (vertical direction).

[0009] (2) In the press machine according to the present invention, the calculation unit may use a plurality of eccentric load data arbitrarily selected by the user from a group of eccentric load data corresponding to the same die as the distribution data of eccentric loads corresponding to the die.

[0010] In the abnormality detection method for a press machine according to the present invention, in the calculation step, a plurality of eccentric load data arbitrarily selected by the user from a group of eccentric load data corresponding to the same die may be used as the eccentric load distribution data corresponding to the die.

[0011] (3) The press machine according to the present invention may further include a display control unit that displays an image plotting a group of eccentric load data corresponding to the same die on a display unit.

[0012] The abnormality detection method for a press machine according to the present invention may further include a display control step of displaying an image on a display unit that plots data sets of eccentric loads corresponding to the same die.

[0013] (4) In the press machine according to the present invention, the display control unit may cause the display unit to display waveform data of load values ​​corresponding to data arbitrarily selected by the user from the data group displayed on the display unit.

[0014] In the method for detecting an abnormality in a press machine according to the present invention, in the display control step, waveform data of a load value corresponding to the data arbitrarily selected by the user from the data group displayed on the display unit may be displayed on the display unit.

Brief Description of the Drawings

[0015] [Figure 1] A diagram showing an example of the configuration of a press machine according to the present embodiment. [Figure 2] A diagram showing an example of a load sensor. [Figure 3] A flowchart showing the flow of a process for generating distribution data of an eccentric load. [Figure 4] A diagram showing an example of load values to be stored. [Figure 5] A diagram showing an example of the display of a data group of eccentric loads corresponding to the same mold. [Figure 6] A diagram showing an example of the display of a data group of eccentric loads corresponding to the same mold. [Figure 7] A diagram showing an example of the display of a data group of eccentric loads corresponding to the same mold. [Figure 8] A diagram showing an example of the display of a data group of eccentric loads corresponding to the same mold. [Figure 9] A diagram showing an example of the display of a data group of eccentric loads corresponding to the same mold. [Figure 10] A diagram showing an example of the display of a data group of eccentric loads corresponding to the same mold and waveform data of load values. [Figure 11] A flowchart showing the flow of a process for detecting an abnormality. [Figure 12] A diagram for explaining the abnormality detection method of the present embodiment. [Figure 13] A diagram showing an example of a change in the distribution of an eccentric load.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0017] FIG. 1 is a diagram showing an example of the configuration of a press machine (servo press) according to the present embodiment. The press machine 1 converts the rotation of the servo motor 10 into the vertical reciprocating motion (reciprocating linear motion, lifting motion) of the slide 17 by an eccentric mechanism that converts rotational motion into linear motion, and performs press working on the workpiece using the vertical reciprocating motion of the slide 17. The press machine 1 includes a servo motor 10, an encoder 11, a drive shaft 12, a drive gear 13, a main gear 14, a crankshaft 15, a connecting rod 16, a slide 17, a bolster 18, a control device 100, a user interface 110 (operation unit), and a display 120 (display unit). The press machine is not limited to a servo press, and for example, a mechanical press using a flywheel or a direct-acting press using a ball screw may be used. In this case, the encoder may be provided at the shaft end of the crankshaft 15 or the shaft end of the ball screw.

[0018] The drive shaft 12 is connected to the rotation shaft of the servo motor 10, and the drive gear 13 is connected to the drive shaft 12. The drive gear 13 meshes with the main gear 14, the crankshaft 15 is connected to the main gear 14, and the connecting rod 16 is connected to the crankshaft 15. The rotation shafts such as the drive shaft 12 and the crankshaft 15 are supported by appropriately provided bearings (not shown). The crankshaft 15 and the connecting rod 16 form an eccentric mechanism. By this eccentric mechanism, the slide 17 connected to the connecting rod 16 can move up and down with respect to the stationary bolster 18. Here, the press machine 1 is a two-point drive press machine in which the crankshaft 15 and the slide 17 are connected by two connecting rods 16 that also function as suspensions. An upper die 20 is mounted on the slide 17, and a lower die 21 is mounted on the bolster 18.

[0019] The press machine 1 is equipped with a right load sensor 30 and a left load sensor 31 for detecting the load value when pressing the workpiece during each press cycle. As shown in Figure 2, the right load sensor 30 is a strain gauge attached to the right column 40 (right side frame) of the press machine 1, and the left load sensor 31 is a strain gauge attached to the left column 41 (left side frame) of the press machine 1. Alternatively, pressure sensors provided in a hydraulic chamber formed within the slide 17 may be used as the right load sensor 30 and the left load sensor 31. The output data (voltage signals from the strain gauge or pressure sensor) from the right load sensor 30 and the left load sensor 31 are input to the control device 100.

[0020] The control device 100 includes a press control unit 101, a detection unit 102, a storage unit 103, a calculation unit 104, a determination unit 105, a notification unit 106, and a display control unit 107. Alternatively, the control device 100 may be divided into two separate devices: one for controlling the press machine, consisting of the press control unit 101, the display control unit 107, a user interface 110, and a display 120; and another for detecting the load, consisting of the detection unit 102, the storage unit 103, the calculation unit 104, the determination unit 105, the notification unit 106, the display control unit 107, the user interface 110, and the display 120. In this case, the output data from the right load sensor 30 and the left load sensor 31 are directly input to the load detection device. Furthermore, operating information of the press machine, such as crank angle information, is input from the press machine control device to the load detection device as needed.

[0021] The detection unit 102 receives data output from the right load sensor 30 and the left load sensor 31 for each press cycle, converts the received data based on calibration data stored in the storage unit 103, and detects it as the load value (right load value and left load value) during press working. The calibration data shows the relationship between the voltage signal and the load value, and is measured in advance using a load cell or the like and stored in the storage unit 103.

[0022] The storage unit 103 stores the load value detected by the detection unit 102, and when the load value is detected, the press machine 1 The identification information (mold number) of the molds (upper mold 20, lower mold 21) attached to the slide 17 and bolster 18 is stored in association with the information.

[0023] The calculation unit 104 calculates the position of the load center acting on the press machine 1 based on the stored load values, calculates the eccentric load (a pair of total load value and eccentricity) from the center of the press machine 1 using the calculated position of the load center, and generates eccentric load distribution data for each die. The generated eccentric load distribution data for each die is stored in the storage unit 103. Here, the calculation unit 104 may use a set of eccentric load data arbitrarily selected by the user from a group of eccentric load data corresponding to the same die as the eccentric load distribution data (for example, normal distribution data) corresponding to that die.

[0024] The determination unit 105 determines an abnormality based on the eccentric load calculated by the calculation unit 104 based on the load value detected by the detection unit 102, and the distribution data of the eccentric load corresponding to the mold attached to the slide 17 and bolster 18 of the press machine 1 at the time the load value was detected.

[0025] The notification unit 106 notifies of an abnormality based on the determination result of the determination unit 105. For example, if the determination unit 105 determines that there is an abnormality, the notification unit 106 outputs information to that effect to the display 120.

[0026] The display control unit 107 displays an image on the display 120 in which a data set of eccentric loads corresponding to the same mold is plotted on a graph. The display control unit 107 may also display on the display 120 waveform data of load values ​​corresponding to data arbitrarily selected by the user from the data set displayed on the display 120.

[0027] The user interface 110 is a known input means (e.g., a mouse, trackball, keyboard, etc.) that can be operated in relation to the display 120. Alternatively, the user interface 110 may be integrated with the display 120. In this case, the input means will be displayed on the display 120.

[0028] The display 120 is a liquid crystal display (LCD). Other known display devices (e.g., organic EL (Electro-Luminescence)) may be used as the display 120. Alternatively, a touch panel display may be used as the display 120. Known types of touch panels such as resistive, capacitive, surface-type capacitive, and projected-type capacitive touch panels can be used. If a touch panel is used, input operations can be performed by directly touching the display 120 with a finger or pen.

[0029] Figure 3 is a flowchart showing the process flow for generating eccentric load distribution data.

[0030] Steps S10 to S13 are processes for storing load values. Load values ​​are stored when a die is attached to the press machine 1 and a trial run (die trial) is performed. First, the detection unit 102 receives data output from the right load sensor 30 and the left load sensor 31, and converts the received data based on calibration data stored in the storage unit 103 to detect load values ​​(step S10). Next, the control device 100 determines whether one cycle of the press has finished based on the current crank angle information (step S11). If one cycle has not finished (N in step S11), it proceeds to step S10 to continue detecting load values. If one cycle has finished (Y in step S11), the storage unit 103 assigns a timestamp to the detected load values ​​for one cycle (waveform data for the right load and waveform data for the left load) and stores them in association with the die numbers of the dies attached to the slide 17 and bolster 18 of the press machine 1 at the time of detection (step S12). Figure 4 shows an example of a stored load value. As shown in Figure 4, the load waveform WR for one cycle detected based on data from the right load sensor 30 and the load waveform WL for one cycle detected based on data from the left load sensor 31 are stored as load values ​​associated with the mold number. Next, the control device 100 determines whether to terminate the storage of the load value (step S13). If storage is to be continued (N in step S13), the device proceeds to step S10, and thereafter, load values ​​are stored for each press cycle.

[0031] Steps S14 to S20 are processes for generating eccentric load distribution data. First, the control device 100 selects a die number based on the user's operation on the user interface 110 (step S14). Next, the calculation unit 104 extracts load values ​​corresponding to the selected die number from the stored load value data (step S15), calculates the position of the load center acting on the press machine 1 from each extracted load value, calculates the eccentric load by determining the eccentricity from the center of the press machine 1 based on the calculated position of the load center, and generates a data set of eccentric loads corresponding to the selected die number (step S16). The eccentricity (eccentric position) can be calculated from the balance of moments based on the left and right load values ​​when the combined waveform of the left and right load values ​​(load waveform WR, load waveform WL) shows a peak value, and the distance between the right load sensor 30 and the left load sensor 31 (distance dc shown in Figure 2). Eccentricity is a value that, when the combined waveform of the left and right load waveforms reaches its peak value, is positive when the right load is greater than the left load, and negative when the left load is greater than the right load. The greater the difference between the left and right loads, the larger the absolute value. Eccentric load is data consisting of the peak value (total load value) of the combined waveform of the left and right load waveforms and the eccentricity calculated from the left and right load values. When pressure sensors installed in the hydraulic chamber formed in the slide 17 are used as the right load sensor 30 and left load sensor 31, the eccentricity is calculated based on the left and right load values ​​when the combined waveform of the left and right load values ​​reaches its peak value and the distance between the two connecting rods 16 (point interval, distance dp shown in Figure 2).

[0032] Next, the display control unit 107 displays an image plotting the generated eccentric load data set on the display 120 (step S17). Figure 5 shows an example of an image plotting the eccentric load data set. The image shown in Figure 5 is a graph (scatter plot) with the horizontal axis (X axis) representing the eccentric position (unit: mm) and the vertical axis (Y axis) representing the total load value (unit: kN), on which the eccentric load data set corresponding to the same mold (selected mold number) is plotted. In the figure, a black dot represents one data point of the eccentric load.

[0033] Next, the user selects a range that should be considered a normal distribution (normal range) from the data set of eccentric loads displayed on the display 120 (step S18). The calculation unit 104 stores the data within the selected range in the storage unit 103 as normal distribution data of eccentric loads corresponding to the mold number selected in step S14 (step S19).

[0034] In step S18, the eccentric load data set may contain abnormal data, such as eccentric load data based on load values ​​detected during material feeding into the mold, or eccentric load data based on load values ​​detected during dry firing. Therefore, as shown in Figure 6, the user specifies the range R of the eccentric load data set that should be considered a normal distribution on the display 120. The range R can be specified using the user interface 110 on the display 120, or by directly touching the display 120 with a finger or pen. However, when actually specifying the range R, it is anticipated that the user may have difficulty deciding which data to specify as the range R from among the many data sets. Therefore, a method for providing the user with information to make that decision is described below.

[0035] (Part 1) As shown in Figure 7, the data set of eccentric loads may be displayed separately for each legend (symbol) based on the operating information of the press machine 1. For example, during press operation, the operation selection switch If "Continuous (Continuous Operation)" is selected in the operation selection switch (Slow Speed, Inch, Cut, Safe One, Continuous), the data obtained during steady operation may be displayed as white dots. On the other hand, if the operation selection switch is selected in the state of "Slow Speed," "Inch (Inch Operation)," or "Safe One (Safe One Process)," the data obtained during non-steady operation such as material feeding into the die or dry firing may be displayed as black dots. By pre-associating the operation information of press machine 1 corresponding to each load value data with the number of shots of press machine 1 (value of the production counter of press machine 1) and storing it in the memory unit 103, it is also possible to associate it with each eccentric load data. Furthermore, buttons may be provided on the screen to display or hide the data group according to the state of the operation selection switch.

[0036] (Part 2) As shown in Figure 8, the data sets of eccentric loads may be displayed according to the legend, based on the accuracy information of the molded product. For example, if the product accuracy is judged to be "good," the obtained data set may be displayed as white dots, and if the product accuracy is judged to be "poor," the obtained data set may be displayed as black dots. The judgment of good or bad product accuracy is not limited to "good" and "poor," but may be further subdivided and displayed according to the legend. By associating the product accuracy information corresponding to each load value data with the number of shots of the press machine 1 (the value of the production counter of the press machine 1) in advance and storing it in the storage unit 103, it is also possible to associate it with each eccentric load data. The judgment of good or bad product accuracy may be automatically input into the storage unit 103 in real time from an inspection device (not shown) during press operation, or the results of a sampling inspection may be manually input into the storage unit 103. The input results of the good or bad judgment are stored in the storage unit 103.

[0037] (Part 3) As shown in Figure 9, the data sets of eccentric loads may be displayed according to the legend for each arbitrary elapsed time unit based on the timestamp information. For example, the data sets may be displayed according to the legend for each elapsed time unit every 30 minutes from the start of operation. When producing with a new mold, the load value data may change during the transition from initial wear after the start of operation (when the fine irregularities of the material have been removed) to steady-state wear. Even in such cases, displaying the data according to the legend for each elapsed time unit makes it easier to recognize the change in eccentric load over time and to select the data of eccentric load after the transition to steady-state wear.

[0038] (Part 4) As shown in Figure 10, the waveform data of the load value corresponding to the data arbitrarily selected by the user from the eccentric load data set displayed on the display 120 may be displayed on the display 120. In the example shown in Figure 10, the waveform data of the load value corresponding to the eccentric load EL, indicated by the white dot in the figure and arbitrarily selected by the user from the eccentric load data set (load waveform WR, load waveform WL) is displayed above the image of the eccentric load data set. At this time, the date and time the data was detected may be displayed along with the waveform data of the load value. In this way, the user can determine which data to place within the range R of a normal distribution based on the waveform of each eccentric load data.

[0039] The above method provides users with information to help them decide when specifying a range R, allowing them to easily determine, even later, which data should be designated as a normally distributed range R.

[0040] Next, the control device 100 determines whether to continue processing (generate normal distribution data of eccentric load corresponding to another mold number) (step S20). If it decides to continue processing (Y in step S20), it proceeds to step S14.

[0041] Figure 11 is a flowchart showing the process flow for detecting abnormalities. Abnormality detection is performed during normal press operation.

[0042] First, the detection unit 102 receives data output from the right load sensor 30 and the left load sensor 31, and converts the received data based on calibration data stored in the storage unit 103 to detect it as a load value (step S30). Next, the control device 100 determines whether or not one cycle of the press has been completed based on the current crank angle information (step S31). If one cycle has not been completed (N in step S31), it proceeds to step S30 to continue detecting the load value. If one cycle has been completed (Y in step S31), the calculation unit 104 calculates the eccentricity from the detected load value for one cycle (waveform data for the right load and waveform data for the left load) to determine the eccentric load (a set of total load value and eccentricity) (step S32).

[0043] Next, the determination unit 105 uses the normal distribution data of eccentric loads for each die stored in the memory unit 103 to determine the distance (deviation) of the eccentric load obtained in step S32 from the said average value (step S33), based on the average value and standard deviation σ of the normal distribution data of eccentric loads corresponding to the die number of the die attached to the slide 17 and bolster 18 of the press machine 1 when the load value was detected in step S30 (step S33), and determines whether the distance is within a predetermined distance (step S34). If the eccentric load obtained in step S32 is more than a predetermined distance (for example, 3σ to 6σ) from the average value of the normal distribution data (N in step S34), the notification unit 106 notifies of the abnormality (step S35).

[0044] Next, the control device 100 determines whether or not to continue the process of detecting abnormalities (step S36). If it decides to continue the process (Y in step S36), it proceeds to step S30, and thereafter detects abnormalities based on the eccentric load determined for each press cycle.

[0045] According to this embodiment, the load values ​​detected by the detection unit 102 are stored in advance, associated with the mold numbers of the molds attached to the slide 17 and bolster 18 of the press machine 1 at the time of load detection. Eccentric loads are calculated from the stored load values ​​to generate normal distribution data of eccentric loads for each mold. During press operation, abnormalities can be detected by determining an abnormality based on the eccentric load determined based on the load values ​​detected by the detection unit 102 and the normal distribution data of eccentric loads corresponding to the molds attached to the slide 17 and bolster 18 of the press machine 1 at the time of load detection. For example, as shown in Figure 12, if the eccentric load EL based on the load values ​​detected during press operation is more than a predetermined distance from the average value of the normal distribution ND of eccentric loads under normal conditions due to a mold abnormality or poor product accuracy, an abnormality can be detected even if the eccentric load EL is within the range of the allowable eccentric load diagram AD. On the other hand, with conventional methods, abnormalities cannot be detected as long as the eccentric load EL is within the range of the allowable eccentric load diagram AD. Furthermore, according to this embodiment, by using data within a range arbitrarily specified by the user from the data set of eccentric loads corresponding to the same mold as the normal distribution data of eccentric loads corresponding to that mold, it is possible to exclude eccentric load data based on load values ​​detected during material feeding into the mold or during dry firing, and to create appropriate normal distribution data of eccentric loads.

[0046] Furthermore, in this embodiment, it is possible to estimate changes in the mold from changes in the distribution of eccentric loads corresponding to the same mold. For example, if the normal distribution of eccentric loads immediately after mold maintenance is within the range R shown in Figure 6, and the distribution of eccentric loads corresponding to the same mold after tens of thousands of shots is as shown in Figure 13, then a tendency for the distribution of eccentric loads to shift towards the upper left is observed, suggesting that wear is progressing in the punch and die on the upstream side of the mold, or that some kind of abnormality is occurring. In this way, changes and abnormalities in the mold can be quickly detected from changes in the distribution of eccentric loads corresponding to the same mold, enabling mold maintenance at the optimal timing.

[0047] In the above example, we explained how to determine an anomaly by treating the eccentric load distribution data as normally distributed data and calculating the distance (deviation) from the mean of the normally distributed data to the target. The method is not limited to this. For example, the MT (Maharanobis-Taguchi) method may be used to determine anomalies by using eccentric load distribution data (data from multiple eccentric loads selected by the user from a set of data corresponding to the same mold) as a unit space, and calculating the Mahalanobis distance from the center of the unit space to the object.

[0048] Patent Document 1 discloses a calculation method for creating an allowable load diagram (corresponding to AD in Figure 12) for a two-point driven press machine, but this method has been well known to those skilled in the art for a long time. The allowable eccentric load diagram created by this calculation method is limited only by the point capacity and does not take into account the effects of slide inclination, etc. Therefore, even when the press machine is used with a load within the allowable value of the eccentric load, there is a concern that problems may occur such as deterioration of product accuracy due to slide inclination, seizure of the slide guide, breakage of the mold, and even damage to the frame and points of the press machine. To avoid such problems, each press manufacturer creates a composite allowable load diagram that takes into account the limit of the point capacity, as well as the safety factor and the limit of the amount of slide inclination, and provides it to the user.

[0049] Although embodiments of the present invention have been described in detail above, it will be readily apparent to those skilled in the art that many modifications are possible without substantially departing from the novel aspects and effects of the present invention. [Explanation of Symbols]

[0050] 1…Press machine, 10…Servo motor, 11…Encoder, 12…Drive shaft, 13…Drive gear, 14…Main gear, 15…Crankshaft, 16…Connecting rod, 17…Slide, 18…Bolster, 20…Upper die, 21…Lower die, 30…Right load sensor, 31…Left load sensor, 40…Right column (right side frame), 41…Left column (left side frame), 100…Control device, 101…Press control unit, 102…Detection unit, 103…Storage unit, 104…Calculation unit, 105…Determination unit, 106…Notification unit, 107…Display control unit, 110…User interface, 120…Display

Claims

1. A detection unit that detects the load value when press working is performed on a workpiece, A storage unit stores the load value detected by the detection unit in association with the identification information of the die attached to the press machine at the time the load value was detected. A calculation unit calculates the position of the load center acting on the press machine based on the stored load values, calculates the eccentric load by determining the position of the load center as the eccentricity from the center of the press machine, generates eccentric load distribution data for each die, and stores it in the storage unit. A determination unit determines an abnormality based on the eccentric load obtained based on the load value detected by the detection unit and the eccentric load distribution data for each mold stored in the storage unit, which corresponds to the mold attached to the press machine at the time the load value was detected. A press machine characterized by including a notification unit that notifies of an abnormality based on the determination result of the determination unit.

2. In claim 1, The calculation unit described above, A press machine characterized in that it uses a set of eccentric load data for the same mold, selected arbitrarily by the user, as the distribution data for the eccentric load corresponding to that mold.

3. In claim 2, A press machine further comprising a display control unit that displays an image plotting a set of eccentric load data corresponding to the same mold on a display unit.

4. In claim 3, The display control unit, A press machine characterized in that it displays on the display unit waveform data of load values ​​corresponding to data arbitrarily selected by the user from the data group displayed on the display unit.

5. A detection step for detecting the load value when press working is performed on a workpiece, A storage step involves storing the load value detected in the above detection step in a storage unit, in association with the identification information of the die attached to the press machine at the time the load value was detected. A calculation step involves calculating the position of the center of load acting on the press machine based on the stored load values, determining the eccentric load by calculating the position of the center of load as the eccentricity from the center of the press machine, generating distribution data of the eccentric load for each die, and storing it in the storage unit. A determination step in which an abnormality is determined based on the eccentric load obtained based on the load value detected in the above detection step and the eccentric load distribution data for each mold stored in the storage unit that corresponds to the mold attached to the press machine at the time the load value was detected. A method for detecting abnormalities in a press machine, characterized by including a notification step of notifying an abnormality based on the determination result of the determination step.

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