Punching processing control method

Abstract

Provided is a punching processing control method for controlling the processing state of a punching device that repeatedly performs a punching process for punching, with a punch (31), a workpiece (33) placed on a die (32), wherein: the work amount (62) of the punching load in a position section including the load during punching of the workpiece is calculated on the basis of a punching load curve (51) indicating the relationship between punch load and position; the impulse (61) of the punching load in a time section including the load during punching of the workpiece is calculated on the basis of a punching load curve (51) indicating the relationship between punch load and time; and the punching speed is determined from the work amount of the punching load and the impulse of the punching load during the punching process.

Description

Punching process control method

[0001] The present disclosure relates to a method for controlling a stamping process.

[0002] The tools used in machine tools wear out with repeated use, causing a deterioration in the machining accuracy of the workpiece. When a tool can no longer maintain the required machining accuracy, it reaches the end of its life. Technologies to extend tool life are being investigated in order to understand the tool's life and take measures such as replacing the tool with a new one before it reaches the end of its life.

[0003] Patent Document 1 discloses an example in which a press is used as a machine tool, in which the press performs repetitive operations. First, the pressure applied to the slide of the press is measured, and the pressure reduction rate is calculated from the change in pressure over time, thereby determining whether or not the workpiece has been punched in that one shot.

[0004] Also disclosed is a punching processing control method in which the slide position of a press machine is measured, and the operating speed of the press machine is calculated from the position information of the slide, and when it is estimated that punching has not been performed on the workpiece, the speed switching position for the next shot is calculated from the measured punching speed and position information of the slide, and the lower limit position of the slide is controlled.

[0005] Patent No. 3775900

[0006] The punching processing control method described in Patent Document 1 merely controls the lower limit position based on the punching speed and punching position, and in particular does not mention which parameters should be selected as inputs to control the punching speed or how they should actually be controlled. Therefore, there is still room for improvement in terms of extending the tool life of the die.

[0007] Therefore, the present disclosure provides a punching control method that can extend the tool life of a die.

[0008] According to one aspect of the present disclosure, there is provided a punching control method for controlling a processing state of a punching device that repeatedly performs punching processing by punching a workpiece placed on a die, the method comprising the steps of: calculating a work amount of the punching load in a position interval including the load at the time of punching the workpiece, based on a punching load curve of the punch versus position; calculating an impulse of the punching load in a time interval including the load at the time of punching the workpiece, based on a punching load curve of the punch versus time; and determining a punching speed based on the work amount of the punching load and the impulse of the punching load during the punching processing.

[0009] According to the present disclosure, by determining the punching speed based on the work load of the punching load and the impulse of the punching load during the punching process, it is possible to perform the punching process under optimal conditions that reduce the load on the tool, and it is possible to provide a punching process control method that can suppress the progression of wear on the side surface of the punch and extend the tool life of the die.

[0010] Schematic diagram showing the process of punching a workpiece with a machine tool Schematic diagram showing the process of punching a workpiece with a machine tool Schematic diagram showing the process of punching a workpiece with a machine tool Schematic diagram showing the process of punching a workpiece with a machine tool Schematic diagram showing the wear state of a punch Schematic diagram showing the wear state of a punch Block diagram of a punching control device according to the present disclosure Graph showing the time change in load on a punch during punching Graph showing the position change in load on a punch during punching Flowchart for determining an estimated value to be controlled using a control value estimation model according to the present disclosure Tool diagram when micro-chipping occurs Graph of a load curve when micro-chipping occurs Graph of a commonly observed change in load curve (time axis) Graph of a commonly observed change in load curve (position axis) Graph of a change in load curve (time axis) according to an embodiment of the present disclosure Graph of a change in load curve (position axis) according to an embodiment of the present disclosure Schematic diagram illustrating lateral force acting on a punch Schematic diagram illustrating lateral force acting on a punch

[0011] [Background to the Disclosure] Tools used in machine tools wear out as machining is repeated, and the load waveform obtained by measuring the load applied to the tool gradually changes as the tool wears.

[0012] Typically, when a tool comes into contact with a workpiece, it processes (cuts, for example) the workpiece due to a shearing force or a breaking force, and the tool receives a reaction force, which gradually wears down the edge of the tool.

[0013] However, for example, after cutting the workpiece, a remnant portion remains, and if the tool and the remnant portion physically interfere with each other, wear will progress not only on the edge of the tool but also on the side of the tool, and as a result of the tool being continuously subjected to an extra load than usual, wear will progress on the tool and the tool life will be shortened; this phenomenon often occurs in actual work sites.

[0014] 1A to 1D are schematic diagrams showing a process in which a die is installed in a machine tool and a workpiece 33 is punched out using a punch 31 and a die 32 as tools in the die.

[0015] When processing starts, the punch 31 descends and comes into contact with the workpiece 33 (FIG. 1A).

[0016] Next, punch 31 starts punching the workpiece 33 (FIG. 1B).

[0017] Furthermore, the punch 31 is lowered, cutting the workpiece 33 (FIG. 1C).

[0018] After punching the workpiece 33, the workpiece 33 is separated into a punched-out portion 33c after cutting and a remaining portion 34, and the punched-out portion 33c falls downward.

[0019] On the other hand, for a while after punching the workpiece 33, physical interference occurs between the punch 31 and the remaining material portion 34 of the workpiece 33, and a load may continue to be applied to the punch 31. For example, the remaining material portion 34 of the workpiece 33 may be pulled between the punch 31 and the die 32 (FIG. 1D), causing interference between the punch 31 and the remaining material portion 34.

[0020] 2A and 2B will be used to explain the differences in the locations where wear of punch 31 progresses. When processing workpiece 33 below punch 31 in Fig. 2A, wear progresses mainly at edge portion 35 below punch 31. Normally, as shown in Fig. 2B, wear progresses so that edge portion 35 develops a C-face or R-face, but when punch 31 interferes with remaining material portion 34, side portion 36 also gradually wears, and the wear of side portion 36 accelerates the wear of edge portion 35, resulting in a shortened tool life.

[0021] The present inventors have used information about the load on the tool to discover a relationship between changes in a calculated value obtained from the load and the progression of wear. Specifically, the present inventors have discovered that by controlling the punching speed, one of the punching conditions, to an optimal value based on the calculated value obtained from the load, the progression of wear on the side surface of the punch and the reduction in tool life can be suppressed, leading to the following disclosure. Here, the calculated values ​​obtained from the load are a punching load workload 62 and a punching load impulse 61. The punching load workload 62 is calculated from a punching load curve 51 (see FIG. 4B ) showing the relationship between the load and position of the punch 31. Specifically, the punching load workload 62 is the integral value of the punching load curve 51 in a position section including the load when punching the workpiece 33. The punching load impulse 61 is calculated from a punching load curve 51 (see FIG. 4A ) showing the relationship between the load of the punch 31 and time. Specifically, the impulse 61 of the punching load is the integral value of the punching load curve 51 in a time interval including the load when punching the workpiece 33. The relationship between the change in the calculated value obtained from the load and the progress of wear is such that if the punching speed increases and the impulse 61 decreases even if the workload 62 does not change, the progress of wear of the punch 31 is suppressed.

[0022] Physical interference between the punch 31 and the remaining portion 34 of the workpiece can be caused by various disturbance factors. Disturbance factors include, for example, a narrow clearance between the punch 31 and the die 32, or cutting in a tearing mode where the breaking force is dominant. For example, as the wear of the punch 31 or the die 32 progresses to a certain extent, the cutting mode can transition from a cutting mode where the shear force is dominant to a cutting mode where the breaking force is dominant. Alternatively, if the workpiece 33 contains a highly ductile material, the cutting mode is likely to become a cutting mode where the breaking force is dominant, regardless of the progress of wear of the punch 31. The highly ductile material can be, for example, a metal material, a resin material, or a composite material of the metal material and the resin material. Examples of highly ductile metallic materials include gold, silver, platinum, iron (pure iron and low-carbon steel), stainless steel (particularly austenitic stainless steel), nickel, copper, aluminum, zinc, tin, lead, titanium, magnesium, or Inconel (a trademark of a nickel-based superalloy, a trade name of Special Metals Corporation (formerly Inco / International Nickel Company)).

[0023] Hereinafter, embodiments of the present disclosure will be described in detail, with appropriate reference to the drawings. However, more detailed description than necessary may be omitted. For example, detailed description of already well-known matters or redundant description of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the inventors provide the accompanying drawings and the following description to enable those skilled in the art to fully understand the present disclosure, and do not intend for them to limit the subject matter described in the claims.

[0024] (Embodiment) [Overall Configuration] FIG. 3 is a block diagram showing a punching control device 103 according to an embodiment.

[0025] The punching control device 103 is a device that implements a punching control method for controlling the processing state of a punching device that repeatedly performs punching by a punch 31 on a workpiece 33 placed on a die 32 .

[0026] The punching control device 103 includes a sensing unit 104, a calculation unit 105, and a processing condition control unit 106, all of which are connected to each other via wire or wirelessly for communication. Communication can be performed using a public line such as the Internet and / or a dedicated line. Each unit may be installed in the same factory or on two or more premises, or may be installed for each machine tool.

[0027] In the sensing unit 104, a load sensor 41 is attached to the punch 31 or the die 32, and the load applied to the punch 31 and the die 32 is measured with high sensitivity as a load curve (waveform) 51. In addition, a position sensor 42 is attached to at least one of the slide and bolster of the punching device of the machine tool and the plates of the die (die plate, stripper plate, etc.), and position information 52 corresponding to the operating position of the punch 31 is measured with high sensitivity. Sensor measurement values ​​43, such as data on the measured load curve (waveform) 51 and position information 52, are sent to the calculation unit 105.

[0028] The calculation unit 105 acquires the load curve 51 and position information 52, which are the sensor measurement values ​​43, and the current (i.e., before the punching speed change determination) punching conditions 53 acquired from the machine tool, and performs numerical calculations based on the acquired sensor measurement values ​​43 and punching conditions 53 in accordance with a preset control value estimation model 90 (described later).

[0029] The load curve 51 is a curve that shows the change over time or the change in position of the load on the punch 31 acquired by the load sensor 41. Here, a case where the load curve 51 shows the relationship between the load and time or the position will be described using Figures 4A to 4B and 1A to 1D. Figure 4A is a graph that shows the change over time of the load on the punch 31 during punching with a machine tool.

[0030] When machining starts, the punch 31 descends and comes into contact with the workpiece 33 (FIG. 1A). In the graph of FIG. 4A, the time when the punch 31 comes into contact with the workpiece 33 is time T1. As shown in the graph of FIG. 4A, almost no load is applied to the punch 31 until the punch 31 comes into contact with the workpiece 33 (section S1 in FIG. 4A).

[0031] When punch 31 starts punching workpiece 33 (FIG. 1B), the load on punch 31 increases rapidly, as shown in section S2 of the graph in FIG. 4A. The point in time when punch 31 cuts workpiece 33 (FIG. 1C) is time T2 of the graph in FIG. 4A. Once workpiece 33 is cut, the load on punch 31 drops to nearly zero. This is because the workpiece 33 has been punched and resistance to punch 31 is gone.

[0032] For a while after punching the workpiece 33 (section S3 in the graph of FIG. 4A), an extra load is applied to the punch 31 due to disturbance factors such as interference between the punch 31 and the remaining material portion 34.

[0033] Furthermore, in actual processing, cutting is not always performed while the punch 31 and the workpiece 33 remain perpendicular, so if punching is performed with the punch 31 tilted even slightly, excess load on the punch 31 due to external disturbances such as interference between the punch 31 and the remaining material portion 34 may also be included in section S2 of the graph in Figure 4A.

[0034] While Fig. 4A only shows a load curve in which the horizontal axis indicates a change over time, as shown in Fig. 4B, a load waveform similar to that of Fig. 4A can also be obtained by indicating a position change corresponding to the operating position of punch 31 on the horizontal axis based on position information 52, as will be described below. Fig. 4B is a graph showing a position change of the load applied to punch 31 during punching by a machine tool.

[0035] When processing starts, the punch 31 descends and comes into contact with the workpiece 33 (FIG. 1A). In the graph of FIG. 4B, the position where the punch 31 comes into contact with the workpiece 33 is position P1. As shown in the graph of FIG. 4B, almost no load is applied to the punch 31 until the punch 31 comes into contact with the workpiece 33 (section S1 in FIG. 4B).

[0036] When punch 31 starts punching workpiece 33 (FIG. 1B), the load on punch 31 increases rapidly, as shown in section S2 of the graph in FIG. 4B. The position at which workpiece 33 is cut by punch 31 (FIG. 1C) is position P2 of the graph in FIG. 4B. Once workpiece 33 is cut, the load on punch 31 drops to nearly zero. This is because the workpiece 33 has been punched and resistance to punch 31 is gone.

[0037] For a while after punching the workpiece 33 (section S3 in the graph of FIG. 4B), an extra load is applied to the punch 31 due to disturbance factors such as interference between the punch 31 and the remaining material portion 34 .

[0038] Furthermore, in actual processing, cutting is not always performed while the punch 31 and the workpiece 33 remain perpendicular, so if punching is performed with the punch 31 tilted even slightly, it is possible that extra load on the punch 31 due to external disturbances such as interference between the punch 31 and the remaining material portion 34 may also be included in section S2 of the graph in Figure 4B.

[0039] The calculation unit 105 calculates various calculation values ​​from the load curve 51. That is, the calculation unit 105 can calculate the integral values ​​(areas) of the load curve 51 in the sections S2 and S3 in Figures 4A and 4B, respectively, and can calculate the load impulse 61 as the integral value in the case of Figure 4A where the horizontal axis shows the change in time, the load work amount 62 as the integral value in the case of Figure 4B where the horizontal axis shows the change in position, and the peak load 63 as the maximum value of the load in the section S2 in Figures 4A and 4B.

[0040] Furthermore, the calculation unit 105 can calculate a punching speed 54 A for the workpiece 33 from the time information and the position information 52 .

[0041] Furthermore, the calculation unit 105 can calculate the punching conditions 55 for the next time (i.e., after the punching speed change determination) based on the calculation results up to now and the current punching conditions 53 (i.e., before the punching speed change determination) in accordance with the control value estimation model 90 (described later).

[0042] The calculated data of the next punching conditions 55 is sent from the calculation unit 105 to the processing condition control unit 106.

[0043] The machining condition control unit 106 can control the machining conditions of the machine tool based on the next (i.e., after the punching speed change determination) punching conditions 55. For example, the machining condition control unit 106 can control the servo motor of the machine tool to increase or decrease the punching speed 54B.

[0044] Although an example has been shown in which the calculation unit 105 calculates the integral value (area) of the load curve 51 in the sections S2 and S3 in FIGS. 4A and 4B, the calculation unit 105 may select only either the section S2 or the section S3 in FIGS. 4A and 4B, and the calculation unit 105 can also obtain the desired load impulse 61 and the amount of change in the load work amount 62 from the integral value (area) of the load curve 51 in the section S2 or S3.

[0045] 5 shows a flow in which the calculation unit 105 determines an estimated value to be controlled by the control value estimation model 90. This model 90 allows the calculation unit 105 to determine a predicted value by exchanging information bidirectionally between the calculation unit 105 and the machining condition control unit 106.

[0046] A method for determining an estimated value of the punching speed by the calculation unit 105 as an example of an estimated value to be controlled will be described with reference to FIG.

[0047] First, in step S1, the calculation unit 105 acquires the current (i.e., before the punching speed change determination) punching conditions 53 from the machine tool, confirms the current (i.e., before the punching speed change determination) punching speed (first speed A), and calculates the first calculation value A using multiple load waveforms of the load curve.

[0048] In the next step S2, the calculation unit 105 calculates the first impulse 61 and the first workload 62 of the load as the first calculation value A. At this time, it is preferable that the calculation unit 105 calculates the average impulse and average workload for the most recent 10 to 100 shots, respectively, and sets them as the first impulse and the first workload. Because the average value for a few shots (less than 10 shots) is prone to variation due to the influence of various disturbances, and because the load waveform changes from moment to moment depending on the amount of wear on the punch 31, it is not preferable to have too few or too many shots. Furthermore, it is preferable that the calculation unit 105 selects the most recent load waveform, taking into account the influence of the amount of wear on the punch 31, as described above.

[0049] In the next step S3, the punching speed is changed from the first speed A to the second speed B by the processing condition control unit 106, and punching is continued. At this time, it is preferable to change the second speed B so that it is faster than the first speed A.

[0050] In the next step S4, the calculation unit 105 calculates a second calculation value B at the second speed B. As the second calculation value B, the calculation unit 105 calculates a second impulse 61 of the load and a second workload 62 of the load, similar to the first calculation value A. It is also preferable that the calculation unit 105 calculates the average value of the impulse and the average value of the workload for the number of shots, similar to the first calculation value A, and sets these as the second impulse 61 and the second workload 62.

[0051] In the next step S5, the calculation unit 105 calculates the amount of change in the average value of the load impulse 61 and the amount of change in the average value of the load workload 62 due to the change from the first speed A to the second speed B. Furthermore, the calculation unit 105 compares the absolute value of the amount of change in the average value of the load impulse 61 with the absolute value of the amount of change in the average value of the load workload 62, and if the calculation unit 105 determines that the following holds: amount of change (absolute value) of workload 62 < amount of change (absolute value) of impulse 61 (1), the process proceeds to the next determination step S6.

[0052] On the other hand, if the calculation unit 105 determines that the formula (1) does not hold, the calculation unit 105 determines in step S8 that the current punching speed (i.e., before the punching speed change determination) is to be maintained as the first speed A.

[0053] In the next step S6, the calculation unit 105 checks whether the amount of change in the average value of the load impulse 61 is a negative value. If the calculation unit 105 determines that the amount of change is a negative value, the process proceeds to the next determination step S7. On the other hand, if the calculation unit 105 determines that the amount of change is not a negative value, the calculation unit 105 determines in step S8 that the first speed A, which is the current punching speed (i.e., before the punching speed change determination), should be maintained.

[0054] In step S6, it is more preferable that the change in the average value of the load impulse 61 is a negative value, and further that the change in the average value of the impulse 61 also satisfies the relationship of the following equation.

[0055] (Second speed B / first speed A) ≦ (impulse 61 at second speed B / impulse 61 at first speed A) (2) This is because, on the premise that the peak load obtained from the load curve remains almost unchanged even when the speed is changed, the impulse may change to the same extent as the speed ratio.

[0056] In the next step S7, the calculation unit 105 determines whether microchipping has occurred in the punch 31 and the die 32. The occurrence of microchipping can be detected by pattern matching with a preset (or stored) reference waveform, or by threshold-determining the load re-rising value (the peak immediately after punching) at time T2 immediately after punching when the load value drops significantly to near zero and at position P2 and thereafter. If the calculation unit 105 determines that microchipping has occurred, it can be determined that the punching speed is not appropriate because there is a possibility that an excessive load is being applied to the tool. Therefore, the calculation unit 105 determines that the current punching speed (i.e., before the punching speed change determination), which is the first speed A, should be maintained.

[0057] In step S7, if the calculation unit 105 determines that no minute chipping has occurred, the calculation unit 105 can determine that it is better to change the punching speed to the second speed B.

[0058] The calculation unit 105 sends the value of the second speed B, which is the punching speed, as the next punching condition 55 to the processing condition control unit 106, and the processing condition control unit 106 changes the punching condition to the second speed B, which is the punching speed.

[0059] According to the above-described decision flow, the punching speed can be determined as an example of an estimated value to be controlled, and the punching conditions can be changed according to the machining state.

[0060] Furthermore, after a certain number of shots have elapsed and the stability of the punching process has been confirmed, such as the absence of micro-chipping, the second speed B, which is the punching speed, becomes the current punching speed (i.e., before the punching speed change decision), and the decision flow in Figure 5 can be repeated.

[0061] Here, the characteristics of the load curve 51 when micro-chipping occurs are shown in FIGS. 6A and 6B.

[0062] Fig. 6A is an enlarged image of the edge of the punch 31 where a micro-chipping 71 has occurred. Fig. 6B shows an example of the load curve at this time, and it can be seen that a micro-peak 72 appears in the chipping area. When a micro-chipping 71 occurs, punching is physically delayed in that area, and this appears in the load curve in the form of a micro-peak 72.

[0063] In this way, by capturing the characteristics of the load waveform in the calculation unit 105, the calculation unit 105 can determine whether or not micro-chipping has occurred.

[0064] According to the punching control method described above, the punching speed is determined based on changes in the workload of the punching load and changes in the impulse of the punching load during punching, thereby controlling the processing state. This makes it possible to carry out punching under optimal conditions that reduce the load on the tool, suppress the progression of wear on the side surface of the punch 31, and extend the tool life of the die.

[0065] [Estimated Mechanism] Here, the mechanism by which such an effect was obtained by changing the punching speed will be explained.

[0066] 7A to 7D show load curves when the punching speed is changed, where Fig. 7A to Fig. 7B show graphs of changes in a commonly seen load curve (time axis and position axis), and Fig. 7C to Fig. 7D show graphs of changes in a load curve (time axis and position axis) according to an embodiment of the present disclosure.

[0067] 7A shows a change in the load curve that is typically observed when the punching speed is changed, with a solid line representing the load waveform 81 before the punching speed change and a dashed line representing the load waveform 82 after the punching speed change. After the punching speed change, the speed is increased compared to before the change. Note that since the horizontal axis in FIG. 7A represents time, calculating the integral value of the load waveform results in the impulse.

[0068] 7B shows a change in the load curve that is typically observed when the punching speed is changed, with the load waveform 83 before the punching speed change shown as a solid line and the load waveform 84 after the punching speed change shown as a dashed line. After the punching speed change, the speed is increased compared to before the change. Note that since the horizontal axis in FIG. 7B represents position, the integral value of the load waveform is calculated to obtain the workload.

[0069] Generally, when the punching speed is increased, the impact force generated between the punch 31 and the workpiece 33 increases, and so the load increases after the punching speed is changed compared to before the change. In other words, the load increases significantly on the vertical axis. On the other hand, when the horizontal axis is the time axis, the horizontal axis direction of the load waveform decreases in proportion to the increase in punching speed. Furthermore, when the horizontal axis is the position axis, the distance over which the load is applied by punching does not change even if the punching speed is increased, so the horizontal axis direction of the load waveform does not change.

[0070] As a result of this mechanism, although it depends on the amount of increase in load, the amount of change (absolute value) of the workload 62 and the amount of change (absolute value) of the impulse 61 become equal, or the amount of change (absolute value) of the impulse 61 becomes greater than the amount of change (absolute value) of the workload 62. Furthermore, after changing the punching speed, both the amount of change in the workload 62 and the amount of change in the impulse 61 increase in value compared to before the change. This is because the load on the vertical axis increases significantly.

[0071] 7C shows a change in the load curve according to an embodiment of the present disclosure when the punching speed is changed, with a solid line representing a load waveform 81 before the punching speed change and a dashed line representing a load waveform 85 after the punching speed change according to an embodiment of the present disclosure. After the punching speed change, the speed is increased compared to before the change. Note that, since the horizontal axis in FIG. 7C represents time, calculating the integral value of the load waveform results in an impulse.

[0072] 7D shows the change in the load curve according to an embodiment of the present disclosure when the punching speed is changed, with a solid line representing a load waveform 83 before the punching speed change and a dashed line representing a load waveform 86 after the punching speed change according to an embodiment of the present disclosure. After the punching speed change, the speed is increased compared to before the change. Note that since the horizontal axis in FIG. 7D represents position, the integral value of the load waveform is calculated to obtain the workload.

[0073] Generally, increasing the punching speed increases the impact force generated between the punch 31 and the workpiece 33. However, if the decrease in lateral force is greater than the increase in impact force (in other words, if changing the punching speed has the effect of mitigating the lateral force 39, as will be described later), the load may not change significantly even if the punching speed is increased. In other words, the vertical axis may remain almost unchanged. On the other hand, if the horizontal axis is the time axis, the punch descends faster as the punching speed increases, so the horizontal axis direction of the load waveform becomes smaller. Furthermore, if the horizontal axis is the position axis, the distance over which the load is applied by punching does not change even if the punching speed is increased, so the horizontal axis direction of the load waveform does not change.

[0074] As a result of this mechanism, although it depends on the increase in load, the change (absolute value) in impulse 61 becomes larger than the change (absolute value) in workload 62. Furthermore, after the punching speed is changed, the change in workload 62 and the change in impulse 61 both decrease in value compared to before the change. This is because the change in the horizontal axis is more easily reflected while the load on the vertical axis remains almost unchanged.

[0075] Generally, variations in the thickness of the workpieces can occur frequently in production sites, and therefore, variations due to variations in the thickness of the workpieces must be eliminated.

[0076] When the thickness of the workpiece varies, in a load curve whose horizontal axis is the position axis, the value on the horizontal axis of the load curve increases or decreases roughly in proportion to the thickness of the workpiece, and the amount of change (absolute value) of the work load 62 also increases or decreases. On the other hand, in a load curve whose horizontal axis is the time axis, the value on the horizontal axis of the load curve increases or decreases roughly in proportion to the thickness of the workpiece, and the amount of change (absolute value) of the impulse 61 also increases or decreases.

[0077] In this case, the amount of change (absolute value) in the workload 62 and the amount of change (absolute value) in the impulse 61 are approximately the same, and the relationship in formula (1) does not hold. In other words, by comparing the change in the workload with the change in the impulse rather than considering only the change in the impulse, it is possible to eliminate changes caused by variations in the thickness of the workpiece and find optimal conditions for reducing the load on the tool.

[0078] In this way, by using the estimation mechanism shown in FIGS. 7C and 7D and the control value estimation model 90 shown in FIG. 5, it is possible to find the optimal conditions for reducing the load on the tool, thereby extending the tool life of the die.

[0079] 8A and 8B, the lateral force acting on punch 31 will be described. In the process of punching workpiece 33 with punch 31, punch 31 receives a reaction force 38 in the punching direction from workpiece 33b that is being deformed during processing, and also receives a lateral force 39 from remaining material portion 34b during processing on the side of punch 31. Remaining material portion 34b during processing is pressed and fixed in the vertical direction by die 32 and stripper 36, so the lateral force 39 from remaining material portion 34b during processing is not negligible.

[0080] 8B, even after the workpiece 33 has been cut, the punch 31 continues to receive a lateral force 39 from the remaining material portion 34 on its side surface. Although the magnitude of the lateral force 39 is reduced compared to during the punching process, the punch 31 continues to receive the lateral force 39.

[0081] Therefore, the load applied to punch 31 is the sum of reaction force 38 in the punching direction and lateral force 39, but the impact force generated between punch 31 and workpiece 33 is included in reaction force 38 in the punching direction. As mentioned above, increasing the punching speed has the effect of increasing the impact force. On the other hand, it is thought that a rapid descent of punch 31 also has the effect of reducing the contact force or dynamic friction coefficient with remaining material portion 34b or remaining material portion 34 during processing, and it is thought that the balance between the impact force and lateral force 39 changes significantly depending on the conditions under which workpiece 33 is punched.

[0082] 7C and 7D, a narrow clearance 37 between the punch 31 and the die 32 is preferable as a condition for causing a change in the load curve according to the embodiment of the present disclosure. When the clearance 37 is narrow, the ratio of the lateral force 39 to the reaction force 38 in the punching direction increases, and therefore, it is considered that changing the punching speed has a greater effect in reducing the lateral force 39. As an example, if the finished dimensions when manufacturing a tool are ±3 μm and the dimensions caused by the accumulated error when assembling the die manually and the distortion when mounting the die on a machine tool are approximately ±12 μm, then in practice, a condition for the clearance 37 to be narrow is considered to be approximately 15 μm or less.

[0083] 7C-7D , the conditions for generating the load curve changes according to the embodiment of the present disclosure are preferably selected such that the workpiece 33 is a highly ductile metal material such as gold, silver, platinum, iron (pure iron and low-carbon steel), stainless steel (particularly austenitic stainless steel), nickel, copper, aluminum, zinc, tin, lead, titanium, magnesium, or Inconel (a trademark of a nickel-based superalloy, a trade name of Special Metals Corporation (formerly Inco International Nickel Company)), a resin material, or a composite material of the above metal and resin materials. The more ductile the material, the greater the ratio of the lateral force 39 to the punching direction reaction force 38, since the material is machined in a tearing-off mode where the fracture force is dominant.

[0084] 7C to 7D, a condition for causing the change in the load curve according to the embodiment of the present disclosure is that the punch 31 or the die 32 has been worn to a certain extent. As the wear progresses, the workpiece is cut in a tearing-off mode in which the breaking force is dominant, and it is thought that the ratio of the lateral force 39 to the punching direction reaction force 38 increases. Generally, when the wear amount of the punch 31 or the die 32 reaches about 20 μm, burrs often occur on the workpiece 33, and it is thought that when the wear amount reaches about 20 μm, the workpiece is often cut in a tearing-off mode.

[0085] [Effects] According to the above-described embodiment, by determining the punching speed and controlling the processing state based on changes in the workload of the punching load and changes in the impulse of the punching load during punching, it is possible to perform punching under optimal conditions that reduce the load on the tool, and it is possible to provide a punching control method that can suppress the progression of wear on the side surface of the punch 31 and further extend the tool life of the die.

[0086] It should be noted that any of the various embodiments or modifications described above can be appropriately combined to achieve the effects of each. In addition, combinations of embodiments, combinations of examples, or combinations of embodiments and examples are possible, and combinations of features from different embodiments or examples are also possible.

[0087] The punching control method according to the present disclosure can be widely applied to extending the tool life of dies in processing devices that perform processes such as cutting, bending, forging, or drawing.

[0088] 103 Punching processing control device 104 Sensing unit 105 Calculation unit 106 Processing condition control unit 31 Punch 32 Die 33 Workpiece 33b Workpiece being processed and deformed 33c Punched-out portion 34 Remaining material portion 34b Remaining material portion during processing 35 Side portion 36 Stripper 37 Clearance 38 Reaction force in punching direction 39 Lateral force 41 Load sensor 42 Position sensor 43 Sensor measurement value 51 Load curve (waveform) 52 Position information 53 Current (i.e., before punching speed change determination) punching condition 54A Punching speed of current (i.e., before punching speed change determination) punching condition 54B Punching speed of next punching condition 55 Punching condition 61 Load impulse 62 Load work amount 63 Peak load 71 Minute chipping 72 Minor peak 81 Load waveform before punching speed change (time axis) 82 Load waveform after punching speed change (time axis) 83 Load waveform before punching speed change (position axis) 84 Load waveform after punching speed change (position axis) 85 Load waveform after punching speed change according to an embodiment of the present disclosure (time axis) 86 Load waveform after punching speed change according to an embodiment of the present disclosure (position axis) 90 Control value prediction model

Claims

1. A punching control method for controlling the processing state of a punching device that repeatedly performs punching processing to punch a workpiece placed on a die with a punch, comprising the steps of: calculating the work amount of the punching load in a position section including the load at the time of punching the workpiece, based on a punching load curve showing the relationship between the load and position of the punch; calculating the impulse of the punching load in a time section including the load at the time of punching the workpiece, based on a punching load curve showing the relationship between the load of the punch and time; and determining a punching speed based on the work amount of the punching load and the impulse of the punching load during the punching processing.

2. The punching processing control method according to claim 1, further comprising the steps of: after the step of determining the punching speed, changing the punching speed from a first speed determined in the step of determining the punching speed to a second speed faster than the first speed; calculating and comparing a change in the work amount and a change in the impulse of the punching load before and after changing the punching speed to the second speed, respectively; and determining the value of the punching speed to be the second speed after the change when the change in the impulse of the punching load is larger than the change in the work amount of the punching load.

3. A punching processing control method according to claim 1, further comprising a step of changing the punching speed from a first speed determined in the step of determining the punching speed to a second speed after the step of determining the punching speed, wherein in the step of changing to the second speed, the value of the punching speed is determined to be the second speed only when the change in the impulse of the punching load is greater than the change in the work amount of the punching load and the change in the impulse of the punching load is a negative value by changing the condition so that the second speed after the change is faster than the first speed before the change.

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