JP7600007B2 - Scrap drop simulation method, simulation program, and press equipment quality assessment method - Google Patents

Description

The present invention relates to a simulation method and a simulation program for the falling of scrap that occurs in a press machine, and a method for assessing the quality of a press machine using the simulation method.

In the manufacturing process of press products, after the workpiece, which is a plate material, is pressed and formed using a press device, there is a trimming process in which the scrap portion of the workpiece is cut off and discarded.

In the trimming process, scrap cut from the workpiece is dropped into a scrap chute installed in the press device. However, if the scrap remains inside the press device due to unpredictable movements, it can cause defective products in the subsequent processing of pressed products or damage to the press dies.

To solve these problems, technology has been developed to simulate the action of scrap falling into the scrap chute when designing press equipment.

For example, Patent Document 1 describes a simulation method in which a press machine and scrap generated from a workpiece pressed by the press machine are virtually created in a computer, and the action of the scrap falling into a scrap chute and being discharged to the outside is virtually reproduced.

JP 2016-134174 A

In conventional simulation methods, when scrap is generated, gravity alone is applied to cause the scrap to fall freely. As a result, scrap of the same shape generated in the same part of the press device will fall in the same way, but in an actual press device, the falling motion of the scrap changes each time. This is thought to be because when scrap is generated, forces other than gravity are also acting, such as the pressing force from the upper die of the press die when cutting, the restoring force due to the elastic deformation of the plate material itself, the moment of inertia of the scrap itself, and air resistance.

However, the magnitude of these forces is small compared to gravity, and they change subtly each time scrap is generated, making it difficult to numerically calculate these forces and add them to the simulation. Also, adding each force to the simulation equation results in an enormous amount of calculations.

The present invention has been made in consideration of the above problems, and aims to provide a simulation method and simulation program for scrap falling that can accurately predict the falling motion of scrap in a press device while suppressing an increase in the amount of calculations in the simulation, as well as a quality assessment method for a press device using the simulation method.

In order to achieve the above object, one embodiment of the present invention is a simulation method for scrap falling, which three-dimensionally models a press die of a press machine, scrap generated from a workpiece machined by the press die, and a scrap chute that guides the scrap to the outside of the press machine, and predicts how the scrap falls into the scrap chute and is discharged to the outside, and is characterized by including a step of applying gravity and a force of random magnitude within a predetermined range to the scrap at the initial stage of the scrap generated from the workpiece falling into the scrap chute.

According to this configuration, when the scrap is virtually dropped into the scrap chute in the simulation, a force of random magnitude within a predetermined range is applied, so the falling motion of the scrap generated in the press device changes each time. This makes it possible to reproduce the way in which the falling motion of the scrap changes each time the scrap is generated without having to individually numerically calculate various forces other than gravity acting on the scrap, so that it is possible to accurately predict the falling motion of the scrap in the press device while suppressing an increase in the amount of calculations in the simulation.

In addition, one embodiment of the present invention is characterized in that the simulation method includes a step of performing a deceleration process for the scrap when the falling speed of the scrap exceeds a predetermined threshold.

This configuration makes it possible to perform a highly accurate simulation while suppressing an increase in the amount of calculation required for the simulation. Specifically, if the time interval for calculating the falling speed of the scrap is lengthened in order to reduce the amount of calculation required for the simulation, a phenomenon occurs in the simulation where the scrap gets caught in the scrap chute. If the reaction force that the scrap receives from the chute is calculated in this state, the reaction force becomes excessively large, and the accuracy of the simulation decreases. Furthermore, if the time interval for calculating the falling speed is shortened in order to resolve this situation, the amount of calculation becomes enormous. In response to this, by slowing down the falling speed, it is possible to lengthen the interval for calculating the falling speed to suppress an increase in the amount of calculation, while suppressing an excessive reaction force when the scrap hits the scrap chute, thereby improving the accuracy of the simulation.

In addition, one embodiment of the present invention is characterized in that in the simulation method, the random force magnitude is set in each of the mutually orthogonal X, Y, and Z directions.

With this configuration, forces of random magnitude act on the falling scrap in the X, Y, and Z directions, making it possible to reproduce the various falling motions that can occur when the scrap falls into the scrap chute.

One embodiment of the present invention is a scrap falling simulation program that creates a three-dimensional model of a press die of a press machine, scrap generated from a workpiece machined by the press die, and a scrap chute that guides the scrap to the outside of the press machine, and predicts the operation of the scrap being discharged to the outside via the scrap chute, and is characterized by including a step of applying gravity and a force of random magnitude within a predetermined range to the scrap at the initial stage of the scrap generated from the workpiece falling into the scrap chute.

With this configuration, it is possible to reproduce the way in which the falling motion of the scrap changes each time it is generated without having to individually numerically calculate the various forces other than gravity acting on the scrap, so it is possible to accurately predict the falling motion of the scrap in the press device while suppressing an increase in the amount of calculations in the simulation.

In addition, one embodiment of the present invention is characterized in that the quality assessment method for a press machine using the simulation method includes an iterative process of repeating the operation of dropping the scrap into the scrap chute a predetermined number of times using the simulation method, a probability calculation process of calculating the probability that the scrap has been discharged to the outside through the scrap chute in the iterative process, and a determination process of determining that the design quality of the press machine is low if the probability is less than a predetermined threshold value.

According to this configuration, by repeating the scrap dropping action a predetermined number of times using the above-mentioned simulation method, it is possible to predict whether scrap with different dropping actions will get stuck in the scrap chute. In addition, if the probability that the scrap is discharged to the outside through the scrap chute is less than a predetermined threshold, i.e., if there is a relatively high probability that the scrap will not be discharged to the outside due to clogging in the scrap chute, etc., it is determined that the design quality of the press device is low. Therefore, by making design changes to the press device based on this determination result, it is possible to improve the design quality of the press device.

The scrap drop simulation method and simulation program of the present invention, as well as the press machine quality assessment method using the simulation method, make it possible to accurately predict the scrap drop behavior in the press machine while suppressing an increase in the amount of calculations in the simulation.

FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. 1 is a block diagram showing a simulation system for executing a simulation method and a method for determining design quality of a press apparatus according to an embodiment of the present invention. 1 is a flowchart showing the steps of a method for simulating scrap dropping. FIG. 13 is a diagram illustrating a deceleration process for the scrap. FIG. 1 is a diagram illustrating a random force acting on scrap. 4 is a flowchart showing the steps of a method for determining the design quality of a press apparatus.

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram showing a press device 50. The press device 50 presses a workpiece 70, which is a plate material, and also performs trimming to cut off a scrap portion of the workpiece 70. As shown in FIG. 1, the press device 50 includes a press die 54 and a scrap chute 56 that guides scrap 72 cut from the workpiece 70 to the outside of the press device 50.

The press die 54 is a part where trimming is performed on the workpiece 70, and includes a lower die 66 fixed at the installation site, and an upper die 61 that can move up and down relative to the lower die 66. The lower die 66 includes a lower cutting blade 68 supported on a lower die body 67. The upper die 61 includes a pad 62 that holds down the workpiece 70 placed on the lower die 66, a cam slider 64, and an upper cutting blade 65. The cam slider 64 moves forward toward the workpiece 70 by abutting against a cam driver 69 provided on the lower die body 67 as the upper die 61 descends, and moves backward as the upper die 61 ascends. The upper cutting blade 65 is provided on the cam slider 64 so as to face the lower cutting blade 68.

The workpiece 70 is cut by the upper cutting edge 65 and the lower cutting edge 68 of the press die 54, and part of the cut workpiece 70 falls into the scrap chute 56 of the press device 50 as scrap 72.

The scrap chute 56 is disposed below the lower cutting edge 68 of the press die 54 and extends at an incline with respect to the vertical direction. In the illustrated example, the scrap chute 56 and the lower die body 60 are integrally formed. As shown in FIG. 2, the scrap chute 56 has two side walls 56a, 56b extending in the vertical direction and a bottom wall 56c connecting the lower ends of the two side walls 56a, 56b, and is open at the top. The top surface of the bottom wall 56c is formed smooth, and the scrap 72 slides downward in the inclined direction along this top surface and is discharged to the outside of the press device 50.

The scrap drop simulation method of this embodiment simulates the process in which scrap 72 generated when workpiece 70 is cut by press device 50 falls into scrap chute 56 and passes through scrap chute 56 until it is discharged to the outside of press device 50. By simulating the manner in which scrap 72 falls and is discharged based on the setting data of press device 50 at the design stage of press device 50, it is possible to eliminate the problem of scrap 72 remaining inside press device 50 at the design stage. The scrap drop simulation method of this embodiment will be described below.

Figure 3 is a block diagram showing a simulation system 10 for executing the scrap drop simulation method of this embodiment. In addition to simulating scrap drop, the simulation system 10 of this embodiment has a judgment function for judging the design quality of the press device 50 using the simulation results. This simulation system 10 is composed of a single computer such as a microcomputer or a personal computer, or multiple computers connected to each other via a network.

The simulation system 10 includes an input device 12 as an information input means, an external storage device 14 as a storage means, a calculation device 16 as a control means, and a display device 18 as a display means.

The input device 12 can be configured using input means such as a keyboard, a mouse, and/or a touch panel.

The external storage device 14 is an external memory connected to the computing device 16 and can be composed of a magnetic disk, optical disk, etc.

The arithmetic unit 16 is a calculator including a microcomputer, and is equipped with a central processing unit (CPU) which is an information processing unit, internal memories such as RAM and ROM, and an input/output interface for communicating with other devices. The information processing unit of the arithmetic unit 16 is not limited to a CPU, and can be, for example, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), an application specific standard product (ASSP), a system on chip (SOC), etc.

The arithmetic device 16 can execute, with the CPU, a scrap drop simulation program stored in the internal memory or the external storage device 14, a scrap drop simulation program recorded on a recording medium readable by the arithmetic device 16, or a scrap drop simulation program loaded from the outside via a network or communication device (not shown). With this simulation program, the arithmetic device 16 simulates pressing and trimming the press device 50 and workpiece 70 that are the analysis targets specified by the input device 12, and simulates the scrap 72 generated from the workpiece 70 falling into the scrap chute 56 and being discharged to the outside.

The above-mentioned flow simulation includes a model construction unit 22, a random force setting unit 24, a deceleration processing unit 26, a probability calculation unit 30, and a judgment unit 32, which are provided in the calculation device 16.

The model construction unit 21 reads shape data of the press device 50, the workpiece 70, and the scrap 72, and constructs a three-dimensional model of these. The shape data can be input to the calculation device 16 via the input device 12 or the external storage device 14. In this embodiment, the three-dimensional model is created using the CAD data used when designing these.

The random force setting unit 24 sets a force F of random magnitude within a predetermined range to be applied at the initial stage of the fall of the scrap 72. This force F of random magnitude (hereinafter also referred to as "random force F") can be expressed by a random function shown in the following formula (1).
force = (upper limit, lower limit) Equation (1)

In this embodiment, as shown in the following equations (2), (3), and (4), a random force F is set in each of the X direction, the Y direction, and the Z direction which are perpendicular to each other.
X-direction force=(upper limit x _up , lower limit x _low ) Equation (2)
Y-direction force=(upper limit value y _up , lower limit value y _low ) (3)
Z direction force=(upper limit value z _up , lower limit value z _low ) Equation (4)

In this embodiment, as an example, the positive Y direction is set to the direction of gravity, and the lower limit y _low is set to 0. In addition, the upper limit x _up , the upper limit y _{up ,} and the upper limit z _up are set to positive values, and the lower limit x _low and the lower limit z _low are set to negative values. The random force F acting on the scrap 72 is the resultant force of the forces in the X direction, Y direction, and Z direction set by the formulas (2) to (4). The range of the magnitude of the random force F is set so that it is smaller than the magnitude of gravity acting on the scrap 72.

When the falling speed V of the scrap 72 exceeds a predetermined threshold value _Vth (hereinafter also referred to as the "speed threshold value _Vth "), the deceleration processing unit 26 performs a process of decelerating the scrap 72. The deceleration processing is performed according to a preset rule, and in this embodiment, when the speed threshold value _Vth is exceeded, a process of halving the magnitude of the falling speed V of the scrap 72 is performed as shown in the following formula (5).
V=V/2...Formula (5)

The probability calculation unit 30 calculates the probability that the scrap 72 is properly discharged outside the press device 50 in the simulation based on the results of the scrap drop simulation. The judgment unit 30 judges whether the design quality of the press device 50 is low or not based on the probability calculated by the probability calculation unit 30.

The results of the simulation of scrap falling analyzed by the computing device 16 are displayed on the display device 18. The display device 18 is a device capable of visually displaying information, and can be configured, for example, with a liquid crystal display, an organic EL display, a plasma display, and/or a cathode ray tube display. The display device 18 can display not only the simulation results but also the simulation process.

Next, the method for simulating scrap dropping using the simulation system 10 will be explained using the flowchart in Figure 4.

As shown in FIG. 4, in step S10, various shape data and calculation condition data are read from the external storage device 14 and/or the internal memory of the computing device 16. The shape data includes shape data of the press device 50, the workpiece 70, and the scrap 70, and also includes data on the shape change caused by processing the workpiece 70. The calculation condition data includes the moving cycle time of the upper die 61 of the press die 54 (e.g., 6 seconds), the pressure force of the press die 54, the time Te for dropping the scrap 72 (e.g., 4 seconds), the number of frames N of the scene into which the drop time Te is equally divided (N is an integer of 2 or more), the upper and lower limits of the random function described above, the magnitude of gravity, and the conditions of the reaction force received from the scrap chute 56 when the scrap 70 abuts against the scrap chute 56. In the next step S12, a three-dimensional model is created by the model construction unit 22 from the shape data that has been read.

In the next step S14, the number of times M (M is an integer equal to or greater than 1) that the scrap 72 will be dropped is set. The number of times M can be a number specified by the input device 12. In the next step S16, the number of times m that the scrap 72 will be dropped is reset, and the number of times m is set to 1.

In the next step S18, scene n=1 is set for the falling motion of scrap 72. Here, n is the number of each scene of the frame number N loaded in the numerical condition data, and is an integer from 1 to N. Scene 1 is set to the scene where scrap 72 is generated by cutting the workpiece 70, that is, the scene at the beginning of the fall of scrap 72.

In the next step S20, the random force setting unit 24 sets a random force F based on the random functions of the above-mentioned equations (2) to (4). In the next step S22, gravity and the random force F are applied to the scrap 72 in scene 1. These forces start the falling action of the scrap 72.

In the next step S24, it is determined whether or not the falling speed V of the scrap 72 exceeds a predetermined speed threshold _Vth . If the speed threshold _Vth is exceeded, in the following step S26, the deceleration processing unit 26 executes a process of decelerating the falling speed V.

Figure 5 is a diagram for explaining the deceleration process of the scrap 72. If the deceleration process is not performed on the scrap 72, and the time interval for calculating the falling speed of the scrap 72 is lengthened (i.e., the value of the number of frames N is reduced) in order to reduce the amount of calculation for the simulation, the scrap 72 may be wedged into the scrap chute 56 in scene n during the simulation, as shown by the scrap 72 shown by the imaginary line in Figure 5. This wedged phenomenon does not occur in the actual press device 50, but if the reaction force that the scrap 72 receives from the scrap chute 56 is calculated based on this wedged state in the simulation, the reaction force may become excessively large, and the scrap 72 may bounce back from the scrap chute 56 (hereinafter also referred to as the "bounce back phenomenon"). In order to eliminate the occurrence of the bounce back phenomenon, it is effective to shorten the time interval for calculating the falling speed (i.e., to increase the value of the number of frames N), but if the number of frames N is increased, the amount of calculation becomes enormous.

Since the falling speed V of the scrap 72 reaches a maximum immediately before it hits the scrap chute 56, in this embodiment, a threshold is set for this falling speed V, and when the falling speed V exceeds the speed threshold _Vth , a deceleration process is performed to prevent the above-mentioned bouncing phenomenon from occurring, while lengthening the interval for calculating the falling speed V of the scrap 72 and suppressing an increase in the amount of calculations. This makes it possible to improve the accuracy of the simulation by suppressing excessive reaction force when the scrap 72 hits the scrap chute 56.

After the deceleration process is performed, in the next step S28, it is determined whether or not the falling time of the scrap 72 exceeds the set falling time Te of the scrap 72. The falling time Te is set to a time until the scrap 72 does not remain in the press device 50 and is discharged to the outside via the scrap chute 56. Note that, in step S24, if the falling speed V is equal to or less than the speed threshold value _Vth , the deceleration process is not performed and the process proceeds to step S28.

If time Te has not been exceeded in step S28, scene n is counter-processed in the following step S30, and processing continues again from step S24. If time Te has been exceeded in step S28, it is determined in the following step S32 whether the number m of times the scrap 72 has fallen is equal to or greater than the set number M. If the number m is less than the set number M, the number m is counter-processed in the following step S34, and processing continues again from step S18 (i.e., the process of dropping the scrap 72 from the initial falling position of scene 1 is newly continued).

Figure 6 is a diagram explaining the random force F acting on the scrap 72. In a falling operation with a count m=1, a random force F1 is applied using a random function at the beginning of the fall of the scrap 72. Also, in a falling operation with a count m=2, a random force F2 is applied at the beginning of the fall of the scrap 72. In this way, by using a random function, the random force F acting on the scrap 72 changes every time the count m changes. Note that the gravity acting on the scrap 72 at the beginning of the fall is constant.

On the other hand, if the number m is equal to or greater than the set number M in step S32, the process proceeds to step S36, and the results of the simulation (whether or not scrap 72 is clogged, the trajectory of the falling scrap 72, etc.) are displayed on the display of the display device 18. In this embodiment, if a clog of scrap 72 occurs, the state in which scrap 72 is clogged inside the press device 50 is displayed on the display. In the example shown in Figure 1, the scrap 72 clogged in the scrap chute 56 is shown by a virtual line, which allows the location of the clog to be visually identified.

As described above, in the simulation method and simulation program according to this embodiment, when the scrap 72 is virtually dropped into the scrap chute 56 in the scrap drop simulation, a force F of random magnitude within a predetermined range is applied, thereby changing the dropping behavior of the scrap 72 each time. This makes it possible to reproduce in the simulation the dropping behavior of the scrap 72, which changes each time due to forces other than gravity acting on the scrap 72 when the scrap 72 is generated in the actually manufactured press device 50 (for example, the pressing force from the upper die 61 of the press die 54 during cutting, the restoring force due to the elastic deformation of the workpiece 70 and the scrap 72, the moment of inertia of the scrap 72 itself, air resistance, and the force due to the shear angle of the upper cutting edge 64 and the lower cutting edge 68).

In addition, because the random force F is set using a random function, the falling motion of the scrap 72 can be changed each time without individually calculating forces other than gravity acting when the scrap 72 is generated, so that the falling motion of the scrap 72 in the press device 50 can be accurately predicted while suppressing an increase in the amount of calculations in the simulation. In addition, in this embodiment, forces of random magnitude are applied to the scrap 72 in each of the X, Y, and Z directions, so that a variety of falling motions that may occur when the scrap 72 falls into the scrap chute 46 can be reproduced.

Furthermore, in the simulation method and simulation program of the present embodiment, when the falling speed of the scrap 72 exceeds a predetermined speed threshold _Vth , a process of decelerating the scrap 72 is performed, thereby making it possible to suppress the occurrence of the bouncing back phenomenon of the scrap 72 in the simulation while reducing the amount of calculation required for the simulation, and thus to perform a highly accurate simulation.

Next, the method for determining the design quality of the press machine 50 using the simulation system 10 will be described using the flowchart in FIG. 7.

As shown in FIG. 7, in step S50, the number of times M for the dropping operation of the scrap 72 is set. The number of times M is set to an integer equal to or greater than 2. The number of times M can be a number specified by the input device 12. In the next step S52, the number of times m for the dropping operation of the scrap 72 is reset, and the number of times m is set to 1.

In the next step S54, a simulation of scrap dropping is performed using the simulation method described above. The processing of step S54 is similar to the processing of steps S18 to S28 and step S30 of the simulation method described above, so details are omitted here.

In the next step S56, it is determined whether the number m of times the scrap 72 falls is equal to or greater than the set number M. If the number m is less than the set number M, the number m is counted in the next step S34, and processing continues again from step S18 (i.e., the process of dropping the scrap 72 from the initial drop position in scene 1 is continued anew). In this way, the simulation of the scrap falling is repeated a predetermined number of times until the set number M is reached (repetitive process).

On the other hand, if the number of times m is equal to or greater than the set number of times M in step S56, the process proceeds to step S60, where the probability calculation unit 30 calculates the probability R that the scrap 72 has been discharged to the outside of the press device 50 via the scrap chute 56 in the above-mentioned repetitive process (probability calculation process). For example, if the number of times M=200 and the number of times that the scrap 72 has been properly discharged to the outside Q=180 (i.e., the number of times that scrap 72 was left behind=20), then the probability R=180/200*100(%).

In the next step S62, it is determined whether the calculated probability R is less than a predetermined threshold value _Rth . The threshold value _Rth can be appropriately set by the input device 12. If the probability R is less than the threshold value _Rth in step S62, it is determined in the following step S64 that the design quality is low (determination step). On the other hand, if the probability R is equal to or greater than the threshold value _Rth in step S62, it is determined in the following step S66 that the design quality is good (determination step). After the determination in step S64 or step S66 is performed, the process proceeds to the next step S68, where the determination result is displayed on the display of the display device 18 together with the simulation result.

As described above, in the method for determining the design quality of the press device 50 of this embodiment, the scrap 72 falling action is repeated a predetermined number of times using the scrap falling simulation method described above, and it is possible to predict whether or not scrap 72 with different falling actions will get stuck in the scrap chute 56. In addition, the design quality of the press device 50 can be improved by calculating the probability that the scrap 72 is discharged to the outside of the press device 50 through the scrap chute 56 and determining the design quality based on this probability. For example, if there is a relatively high probability that the scrap 72 will not be discharged to the outside of the press device 50 due to clogging in the scrap chute 56, etc., the design quality of the press device 50 is determined to be low, and the design of the press device 50 can be changed based on this determination result.

For example, if the design quality is judged to be low, the shape of the bottom surface of the scrap chute 56 can be redesigned to be V-shaped as shown in Figure 2 to make it easier to fall. In addition, for example, a rod-shaped member for changing the falling attitude of the scrap 72 can be installed between the position where the scrap 72 starts to fall and the scrap chute 56, and the falling action can be controlled so that the scrap 72 comes into contact with this rod-shaped member and is discharged properly without clogging.

The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the invention.

10 Simulation system 12 Input device 14 External storage device 16 Calculation device 18 Display device 50 Press device 54 Press die 56 Scrap chute 61 Upper die 66 Lower die 70 Workpiece 72 Scrap F1, F2 Random force

Claims (5)

A simulation method for scrap dropping, which comprises creating a three-dimensional model of a press die of a press machine, scrap generated from a workpiece machined by the press die, and a scrap chute that guides the scrap to the outside of the press machine, and predicting how the scrap drops into the scrap chute and is discharged to the outside, comprising:
A simulation method comprising the steps of: applying gravity and a force of a random magnitude within a predetermined range to the scrap generated from the workpiece at the initial stage of the scrap falling into the scrap chute. The simulation method according to claim 1, further comprising a step of performing a deceleration process for the scrap when the falling speed of the scrap exceeds a predetermined threshold. The simulation method according to claim 1 or 2, characterized in that the random force is set in each of the mutually orthogonal X, Y, and Z directions. A scrap dropping simulation program for three-dimensionally modeling a press die of a press device, scrap generated from a workpiece machined by the press die, and a scrap chute that guides the scrap to the outside of the press device, and predicting an operation of the scrap being discharged to the outside through the scrap chute,
A simulation program comprising a step of applying gravity and a force of a random magnitude within a predetermined range to the scrap generated from the workpiece at the initial stage of the scrap falling into the scrap chute. A quality assessment method for a press machine using the simulation method according to any one of claims 1 to 3,
a repeating step of dropping the scrap into the scrap chute a predetermined number of times using the simulation method;
a probability calculation step of calculating a probability that the scrap is discharged to the outside through the scrap chute in the repetitive step;
a determining step of determining that the design quality of the press apparatus is low when the probability is less than a predetermined threshold value;
A method for evaluating the quality of a press machine, comprising:

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