JP2023008161A - Automatic operation stabilization device, automatic operation stabilization method, and program - Google Patents

Abstract

To detect chattering vibration with high accuracy and suppress generation of chattering vibration in a cutting process, even in an environment where disturbance of a factory or the like may occur.SOLUTION: An automatic operation stabilization device 17 includes: a work material dimension calculation section 21 for calculating the dimensions of a work material, in the automatic operation stabilization device 17 in which a cutting tool 5 is mounted to a spindle 7 and the cutting tool 5 is rotated together with the spindle 7, and which outputs a command for controlling a cutting process to a processing device 4 carrying out the cutting process of the work material 6; a processing condition calculation section 22 for calculating feeding speed indicating a relative movement speed of the work material in the cutting process, on the basis of the dimensions of the work material; and a processing device command section 25 which outputs to the processing device 4, a change command for changing at least one of the feeding speed and a rotational frequency of the spindle 7, according to generation of chattering vibration in the processing device 4 determined based on variation in a feeding shaft motor current that is a current of a feeding shaft motor 10 of the processing device 4 in the cutting process.SELECTED DRAWING: Figure 1

Description

The present invention relates to technology for controlling machining equipment based on chatter vibration in the cutting process.

2. Description of the Related Art In a cutting process in which a cutting tool and a work material are moved relative to each other using a machining apparatus to machine the work material, chatter vibration may occur and the cutting tool may be damaged. When chatter vibration occurs, it may cause deterioration of machining quality and chipping of the cutting edge of the cutting tool. In addition to chatter vibration, chipping of the cutting edge of the cutting tool is also caused by foreign substances that are inherent in the work piece, etc., and if machining is continued with chipping of the cutting tool, the cutting tool may be severely damaged. In indexable cutting tools, not only the cutting edge called replaceable insert tip but also the body to which the insert tip is attached may be damaged.

In the chatter vibration control device described in Patent Document 1, vibration detection means for detecting vibration, vibration analysis means for analyzing the vibration of the cutting tool based on the vibration detected by the vibration detection means, and the analysis result of the vibration analysis means and a tool control means for controlling the feed rate of the cutting tool, and when the magnitude of the chatter vibration of the cutting tool detects chatter vibration exceeding a threshold value, the tool control means controls the number of revolutions of the cutting tool and the Suppress chatter vibration by changing the feed rate. It is described that an acceleration sensor, a microphone, or the like can be exemplified as the vibration detection means.

Further, in the tool abnormality detection device described in Patent Literature 2, the fluctuation width per unit time of the load of the motor of the processing device is calculated, and the abnormality of the cutting tool is detected based on the comparison with the threshold value.

JP 2018-20426 A JP 2020-157447 A

However, at cutting sites such as factories, multiple different processing devices are installed in close proximity, and environmental factors such as loading and unloading of work materials by cranes cause vibrations and sounds that suddenly occur, resulting in chatter vibration events. There are many disturbances in detection. If a chatter vibration detection device using conventional vibration detection means is operated in an environment where such disturbances can occur, the possibility of generating false alarms due to the disturbance increases even if the installation positions of the acceleration sensor and the microphone are adjusted.

Also, when chatter vibration occurs, countermeasures against chatter vibration can be taken by changing the setting values for the cutting process, such as reducing the rotation speed and feed rate of the cutting tool, and temporarily stopping the cutting process. Therefore, even if chatter vibration can be reliably detected, if false alarms occur frequently, the productivity of the cutting process is lowered.

In addition, there is a cutting process in which the side surface of a plate-shaped material formed by forging or rolling is cut to adjust it to a desired size (width). The width and thickness of the plate-shaped work material are not constant, but the dimensions fluctuate, and the plate-shaped work material is also bent. For this reason, the cutting resistance is reflected in the spindle servomotor current, but when cutting a plate-shaped work material with such irregular dimensions, the current value in the normal state fluctuates greatly, and the normal state and the abnormal state are different. is difficult to determine with high accuracy. Therefore, in cutting a work material whose dimensions vary, when detecting an abnormality of the cutting tool using measurement data such as the servo motor current of the machining device, it is necessary to distinguish between the normal state and the abnormal state with high accuracy. is an issue.

Furthermore, in order to realize a highly efficient cutting process for a work material whose dimensions vary, it is effective to set an appropriate feed rate according to the dimensions of the work material. However, when the dimension of the work material changes frequently, the operator often adjusts the feed rate manually, which hinders automation. Therefore, it is also a challenge to improve efficiency in automatic operation of the cutting process.

Therefore, an object of the present invention is to detect chatter vibration with high precision in an environment where there are many disturbances compared to the conventional chatter vibration detection method such as a cutting site, in cutting work of irregular dimensions. Detect and suppress. Moreover, it is more desirable to stabilize the automatic operation that can detect the tool abnormality with higher accuracy and suppress the expansion of tool damage. In addition, it is an object of the present invention to automatically acquire the dimensions of an irregularly shaped work material, match the dimensions of the work material, and stabilize the automatic operation capable of automatically setting an appropriate feed rate.

In order to solve the above problem, the present invention detects the occurrence of chatter vibration based on variations in feed shaft motor current obtained from the drive unit. More specifically, a cutting tool is mounted on a spindle, the cutting tool is rotated together with the spindle, and a command for controlling cutting is output to a processing device that performs cutting of a work material. Stabilization of automatic operation In the apparatus, a work material size calculation unit that calculates the size of the work material; and a processing that calculates a feed rate indicating a relative movement speed of the work material in the cutting process based on the size of the work material. A condition calculation unit determines the feed rate and the spindle speed according to the occurrence of chatter vibration in the processing device determined based on variations in the feed shaft motor current, which is the current of the feed shaft motor of the processing device in the cutting process. and a processing device command unit that outputs a change command to change at least one of the rotation speeds of the processing device.

The present invention also includes an automatic driving stabilization method using an automatic driving stabilization device, a program that causes the automatic driving stabilization device to function as a computer, and a storage medium that stores this program.

According to the present invention, chatter vibration can be detected with higher accuracy, and machining control capable of suppressing it becomes possible.

It is a figure which shows the structure of the automatic operation stabilization system in one Example of this invention. It is a flowchart processed by the automatic driving stabilization system in one Example of this invention. FIG. 5 is a time-series chart of the feed shaft motor current when chatter vibration is automatically suppressed after the occurrence of chatter vibration in one embodiment of the present invention. FIG. 5 is a time-series chart diagram of the standard deviation of the feed shaft motor current when the chatter vibration is automatically suppressed after the occurrence of the chatter vibration in one embodiment of the present invention. FIG. 5 is a time-series chart diagram of the feed rate when chatter vibration is automatically suppressed after the occurrence of chatter vibration in one embodiment of the present invention. FIG. 5 is a time-series chart of standard deviation of feed shaft motor current before and after chatter vibration occurs in one embodiment of the present invention. FIG. 4 is a time-series chart of average values of feed shaft motor currents in one embodiment of the present invention. FIG. 5 is a time-series chart of feed axis motor current when a tool abnormality is detected and machining is stopped in one embodiment of the present invention. FIG. 4 is a time-series chart of the standard deviation of the feed axis motor current when the tool abnormality is detected and the machining is stopped in one embodiment of the present invention; FIG. 4 is a time-series chart of feed rates when a tool abnormality is detected and machining is stopped in an embodiment of the present invention; It is a figure which shows the image data acquired by the cut material information acquisition part in one Example of this invention. FIG. 4 is a diagram showing a calculation rule for calculation processing of feed speed based on work material size in one embodiment of the present invention. It is a figure which shows the GUI screen of the display part in one Example of this invention.

An embodiment of the present invention will be described below. In the present embodiment, the target is a processing apparatus 4 for cutting work materials of various shapes, that is, work materials having irregular dimensions. In addition, in all the drawings for explaining this embodiment, the same reference numerals are given to the parts having the same function, and the repeated explanation thereof will be omitted in principle. However, the present invention should not be construed as being limited to the contents of the examples described below. Those skilled in the art will easily understand that the specific configuration can be changed without departing from the idea or gist of the present invention.

The present embodiment will be described in detail below. In this embodiment, in the processing device 4 for cutting a work material with irregular dimensions, the dimensions of the work material are automatically obtained, the feed speed is set, and the increase in variation in the feed shaft motor current is determined by a threshold value. to detect chatter vibration. After that, the feed speed is changed by automatic control to suppress chatter vibration, and when the variation in the feed axis motor current exceeds the threshold value again, it is determined that the tool is abnormal and the tool breakage is detected.

FIG. 1 is a diagram showing the configuration of an automatic driving stabilization system 1 in this embodiment. FIG. 1 shows an example in which an automatic operation stabilizing system 1 is attached to a processing device 4 . Also, the cutting process in the automatic driving stabilization system 1 is an example of cutting the side surface of the plate-shaped work material 6 . The processing device 4 is an NC milling machine, a machining center, or the like that can be controlled by an NC program (Numerical Control).

In the processing device 4, a cutting tool 5 is fixed to a main shaft 7, the main shaft 7 is rotated by a main shaft motor 8, a work material 6 is fixed to a table 9, and the cutting tool 5 and the work material 6 are relatively moved. The work material 6 is processed into a desired shape by bringing it into contact. At this time, the current value input to the spindle motor 8 by the servo amplifier 11a is controlled by a command from the NC device 12 in which the NC program is stored. As a result, the spindle motor 8 is rotated at the number of revolutions as instructed. Similarly, based on commands from the NC device 12, the servo amplifier 11b controls the current value input to the feed shaft motor 10. FIG. As a result, the feed shaft motor 10 is rotated so as to achieve the feed speed as instructed. The cutting tool 5 is, for example, an indexable end mill having a plurality of blades.

The automatic driving stabilization device 17, which is the main body of the automatic driving stabilization system, can be configured on a general-purpose computer. Its hardware configuration consists of the following components.
・Arithmetic unit 2 composed of CPU (Central Processing Unit), RAM (Random Access Memory), etc.
・Storage unit 3 composed of ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive) using flash memory, etc.
・Input unit 13 composed of input devices such as a keyboard and a mouse
・Display unit 14 composed of a display device such as an LCD (Liquid Crystal Display) or an organic EL display, various output devices, etc.
A communication unit 15 configured by a NIC (Network Interface Card), an input/output interface device, and the like.

The communication unit 15 is connected to a wired network, a wireless network, an individual dedicated cable, a USB (Universal Serial Bus) cable, or the like. Through these, the communication unit 15 is connected to the measurement unit 16 for measuring the current value between the servo amplifier 11b of the processing device 4 and the feed shaft motor 10, the NC unit 12, and the workpiece information acquisition unit 18. ing.

The measurement unit 16 is composed of a current sensor, an AD converter, and the like. The work material information acquisition unit 18 is composed of a camera, a displacement meter, and the like. The automatic driving stabilization system 1 is composed of an automatic driving stabilization device 17 , a measurement section 16 and a work piece information acquisition section 18 .

The calculation unit 2 implements each functional unit by loading each program stored in the storage unit 3 into the RAM and executing it by the CPU. The programs include a workpiece dimension calculation program 31, a machining condition calculation program 32, a measurement signal processing program 33, an abnormality detection program 34, and a machining apparatus command program 35. The calculation unit 2 has a work material dimension calculation unit 21, a machining condition calculation unit 22, a measurement signal processing unit 23, an abnormality signal processing unit 24, and a processing device command unit 25 corresponding to each program. Here, these functions may be realized by processing according to a program or may be realized by processing by dedicated hardware. In this embodiment, each unit corresponds to each program on a one-to-one basis, but the present invention is not limited to this. Further, when processing according to a program is performed, the calculation unit 2 may not be divided into individual units, but in the present embodiment, each unit performs the processing. The program storage unit 3 has storage areas for storing the programs described above, control parameters 36 , workpiece information 37 , workpiece dimensions 38 , and measurement signals 39 .

The automatic operation stabilization system 1 is activated upon receiving a signal from the NC device 12 that the work material 6 is input to the processing device 4 . Then, the measuring unit 16 operates until the end of machining is determined based on the measurement signal of the current value obtained between the servo amplifier 11b and the feed shaft motor 10 (hereinafter referred to as the feed shaft motor current). Alternatively, when an abnormality of the cutting tool is detected, the operation is continued until issuing a preset control instruction for the processing device 4 is completed.

The work material size calculation unit 21 calculates the size of the work material from the measurement data acquired by the work material information acquisition unit 18 stored in the work material information 37 using the work material size calculation program 31 in the storage unit 3. Calculate The calculated dimensions of the work material are stored in the work material dimensions 38 of the storage unit 3 .

The machining condition calculator 22 uses the machining condition calculator 32 in the storage unit 3 to calculate the feed rate according to the dimensions of the workpiece stored in the workpiece dimensions 38 . The feed speeds to be calculated are the normal feed speed according to the dimensions of the work material and the feed speed at the time of abnormal detection when chatter vibration is detected. The feed speed when an abnormality is detected is calculated based on the feed speed when normal. The calculated feed speed is stored in the control parameter 36 of the storage unit 3 . In addition, the normal feed rate is output to the NC unit 12 of the processing device 4 by the processing device command unit 25 according to the processing device command program 35 before starting the cutting process.

The measurement signal processing unit 23 uses the measurement signal processing program 33 in the storage unit 3 to perform arithmetic processing on the measurement signal of the feed shaft motor current stored in the measurement signal 39 to determine chatter vibration and tool abnormality.

When the measurement signal processing unit 23 determines chatter vibration, the abnormality signal processing unit 24 changes at least one of the feed speed at the time of abnormality detection and the rotation speed of the main shaft 7 stored in the control parameter 36 to a processing device command. The part 25 outputs to the NC device 12 of the processing device 4 .

Further, when the measurement signal processing unit 23 determines that the tool is abnormal, the processing device command unit 25 issues a change command to perform the operation of the processing device 4, which is stored in advance in the control parameter 36, to the NC unit of the processing device 4. output to 12. The commands at this time are tool retraction, tool replacement, and the like.

Next, the processing flow performed by the automatic driving stabilization system 1 and the processing device 4 shown in FIG. 1 will be described below along with the example of the flowchart of FIG.

First, in step S01, the operation of the automatic driving stabilization system 1 is started. When the operator presses the operation start button on the GUI screen of the automatic operation stabilization system, which will be described later, displayed on the display unit 14, the operation of the automatic operation stabilization system 1 is started, and the work material input start signal Standby state.

Next, in step S<b>02 , the automatic operation stabilizing system 1 recognizes that the work material 6 has been put into the processing device 4 by a trigger signal for putting the work material 6 into the processing device 4 . This recognition can be performed by the work material size calculator 21 or the like. Here, the trigger signal for recognizing that the work material 6 has been introduced into the processing device 4 may be triggered by reading a specific character string by monitoring the information of the NC program. Alternatively, a PLC (Programmable Logic Controller) built in the processing device 4 or a post-installed PCL may output a signal that the work material 6 is introduced into the processing device 4 as a trigger. Alternatively, a sensor may be attached to the movement path of the work material 6 of the processing device 4, and a signal or the like that detects movement of the work material 6 may be used as a trigger.

Next, in step S03, the work material information acquisition unit 18 acquires the shape and dimensions that affect the machining load (cutting resistance) of the cutting process. For example, when cutting the side surface of the plate-like cut material 6, the thickness of the plate material is obtained, and when cutting the upper surface of the plate-like cut material 6, the width is obtained. A camera, a displacement meter, or the like is used for the work material information acquisition unit 18 . When a camera is used for the work material information acquisition unit 18 , the measured data is stored in the work material information 37 of the storage unit 3 . When a displacement gauge or the like that can directly acquire the dimensions of the work material is used in the work material information acquisition unit 18 , the measured dimensions of the work material are stored in the work material dimensions 38 of the storage unit 3 .

In addition, in order to use a displacement gauge or the like that can directly acquire the dimensions of the work material 6 in the work material information acquiring unit 18, the position in the processing device 4 that does not hinder the cutting process on the movement path of the work material 6 is required. Therefore, it is necessary to install a sensor such as a displacement meter in contact with or close to the work material 6. On the other hand, when a camera is used for the work material information acquisition unit 18, it can be installed at a position farther from the work material 6 than a displacement meter or the like, so there is an advantage that there are many options for the installation location.

Next, in step S<b>04 , the work material dimension calculation unit 21 uses the work material dimension calculation program 31 from the measurement data acquired by the work material information acquisition unit 18 stored in the work material information 37 . Calculate the dimensions of the material 6. The calculated dimensions of the work material 6 are stored in the work material dimensions 38 of the storage unit 3 . Note that this step is omitted when a displacement gauge or the like is used for the work material information acquisition unit 18 .

Next, in step S<b>05 , the machining condition calculation unit 22 uses the machining condition calculation program 32 from the dimensional data of the work material 6 stored in the work material information 37 to calculate normal values according to the dimensions of the work material 6 . Calculate the feed speed at time and the feed speed at the time of abnormality when chatter vibration is detected. The calculated normal feeding speed and abnormal feeding speed are stored in the control parameter 36 of the storage unit 3 . The abnormal feed speed is calculated based on the normal feed speed. In normal machining, cutting is performed at the normal feed rate, and when chatter vibration is detected, the automatic operation stabilizing system 1 automatically switches to the abnormal feed rate. Further, the normal state indicates a case where chatter vibration is not detected, and the abnormal state indicates a case where chatter vibration is detected.

Next, in step S<b>06 , the processing device command section 25 outputs a command including the normal feed speed stored in the control parameter 36 to the NC unit 12 of the processing device 4 .

In step S07, the processing device 4 changes the feed speed according to the feed speed command value included in the command output in step S07. Then, in step S08, the processing device 4 performs cutting according to the changed feed rate. That is, the processing device 4 rotates the main shaft 7 to which the cutting tool 5 is fixed, and moves the work material 6 fixed to the table 9 relative to the cutting tool 5 to start processing.

Then, in step S09, the measurement unit 16 starts acquiring the feed shaft motor current obtained between the servo amplifier 11b and the feed shaft motor 10. FIG. The acquired measurement signals are sequentially stored in the measurement signal 39 of the storage unit 3 as time-series data. The start of current acquisition is triggered by the reading of a specific character string or an increase in the motor current of the spindle 7 by monitoring the information of the NC program. Further, it is preferable that the current acquisition interval (cycle) is shorter than the cycle obtained from the frequency of the number of blades times the number of rotations of the cutting tool so that the state of the tool can be easily reflected.

Next, in step S10, the abnormality signal processing unit 24 extracts data from the measurement signal stored in the measurement signal 39 using the abnormality detection program 34 at each preset time interval, and calculates the standard deviation, which is the variation. Calculate After the chatter vibration is detected, it is necessary to respond in a short time (several seconds) in order to reduce the deterioration of the machining quality of the machined surface and the damage to the cutting edge of the cutting tool 5 .

For this reason, the time interval for calculating the variation, which is the characteristic amount for detecting chatter vibration, should be as short as possible, preferably one second or less. In order to stably calculate variations, the number of data is preferably at least 100. For example, in order to obtain 100 data at 1-second intervals, it is preferable to set the current acquisition interval to 10 milliseconds or less. be.

The feed shaft motor current reflects the feed speed at which the workpiece 6 and the cutting tool 5 move relative to each other. If a certain period of time has elapsed with the feed shaft motor current value being low, it can be determined that the workpiece 6 and the cutting tool 5 have not moved relative to each other and that the cutting process has stopped. In order to determine the machining state in step S12, which will be described later, the average value of the feed shaft motor current is also calculated in step S10.

Further, in step S11, the abnormality signal processing unit 24 compares the variation calculated in step S10 with a preset abnormality determination threshold value. If the abnormality determination threshold is exceeded, it is determined that chatter vibration has occurred, and the process proceeds to step S13. The abnormality determination threshold is set in advance based on existing data obtained in advance when chatter vibration occurs and data when tool breakage occurs.

On the other hand, if the abnormality determination threshold value is not exceeded, the abnormality signal processing unit 24 determines the machining state in step S12. In step S12, when it is determined that machining is in progress, the process returns to step S10 to extract feed shaft motor current data at preset time intervals and calculate variations. Standard deviation is suitable for this variability, but other measures such as variance may be used.

On the other hand, if it is determined in step S12 that the machining is finished, after stopping the acquisition of the feed shaft motor current, the process returns to step S02 and waits until the next workpiece 6 is input. In step S12, when the average value of the feed shaft motor current calculated in step S10 continues to be lower than a predetermined value, it is determined that the machining is finished. For example, when the machining state determination threshold is set to 5 [A], the end of machining is determined when the average value of the feed axis motor current is equal to or lower than the machining state determination threshold for 5 consecutive seconds.

Further, in step S13, the abnormality signal processing unit 24 counts the threshold value exceeding number n when the abnormality determination threshold value is exceeded in step S11. The initial value of the number of times exceeding the threshold value n is 0 (zero), and when the threshold value is exceeded once, the number of times exceeding the threshold value n becomes 1, and thereafter, the number of times exceeding the threshold value n increases each time the threshold value is exceeded. It should be noted that the number of exceeding the threshold value n is reset to 0 (zero) when the end of machining is determined in step S12 and when the tool abnormality is determined in step S17.

Further, in step S14, if the number of exceeding the threshold value n=1 in the abnormality signal processing unit 24, the process proceeds to step S15 for outputting a feed speed signal at the time of abnormality. As a result, when chatter vibration occurs, it is possible to suppress the chatter vibration by controlling at least one of the feed speed and the rotational speed of the main shaft 7 . On the other hand, if the number of times of exceeding the threshold n is not 1, the process proceeds to step S17.

In step S15, the processing device command unit 25 sends a change command including at least one of the abnormal feed speed and the rotational speed of the main shaft 7 stored in the control parameter 36 of the storage unit 3 to the NC device 12 of the processing device 4. Output.

In step S16, the processing device 4 changes at least one of the feed speed and the rotation speed of the main shaft 7 according to the change command input to the NC device 12 including at least one of the feed speed and the rotation speed of the main shaft 7 when there is an abnormality. After that, the process returns to step S10.

In step S17, the abnormality signal processing unit 24 compares the predetermined number of exceeding the threshold m for judging tool abnormality with the number of exceeding the threshold n counted in step S13. When the number of exceeding the threshold value n is smaller than the number of exceeding the threshold value m for judging tool abnormality, it is determined that there is no tool abnormality and the process returns to step S10. On the other hand, when the number of times exceeding the threshold value n is equal to or more than the number of times exceeding the threshold value m for determining tool abnormality, it is determined that the tool is abnormal and the process proceeds to step S18. When the cutting tool 5 is broken, even if at least one of the feed speed and the rotation speed of the main shaft 7 is controlled, the fluctuation of the feed shaft motor current is not reduced and the threshold value is repeatedly exceeded. Therefore, it is possible to detect the tool breakage by comparing the increase in the number of exceeding the threshold value n with the number of exceeding the threshold value m for determining the tool abnormality.

It should be noted that the determination of the tool abnormality is not necessarily limited to the number of exceeding the threshold value m for judging the tool abnormality. .

However, if the number of exceeding the threshold value m for judging the tool abnormality is too small, there is a possibility that the tool abnormality is erroneously determined before the chatter vibration is suppressed. After it is determined in step S11 that the variation in the feed axis motor current exceeds the abnormality determination threshold value and that chatter vibration has occurred, in step S16 the processing device 4 changes at least one of the feed speed and the rotation speed of the main shaft 7 to prevent chatter vibration. There is a time lag of several seconds before it is suppressed. Therefore, it is necessary to set the number of exceeding the threshold value m for judging the tool abnormality in consideration of this time lag.

Further, in step S18, the processing device command section 25 outputs to the NC device 12 of the processing device 4 a change command for executing the operation of the processing device 4, which is stored in advance in the control parameters 36 of the storage section 3. FIG. The command at this time is, as described above, tool retraction, tool replacement, or the like.

At step S<b>19 , the processing device 4 performs an operation upon detection of tool abnormality based on the command input to the NC device 12 . When the operation at the time of tool abnormality detection is to retract the tool, the processing device 4 stops the feed of the work material 6, then separates the cutting tool 5 from the work material 6, and moves the work material provided in the processing device 4. to a safe position where it does not come in contact with the fixing jig.

In addition, if the processing device 4 is equipped with an automatic tool changer for the cutting tool 5, prepare the same cutting tool 5 used for cutting, and perform the following processing after determining that the tool is abnormal. It can be performed. After stopping the feed of the work material 6, the processing device 4 separates the cutting tool 5 from the work material and automatically replaces it with another cutting tool of the automatic tool changer, and removes the cutting tool 5 determined to be abnormal. It is possible to process the continuation of

In this case, the automatic operation stabilizing device 17 restarts from acquiring the feed shaft servomotor current in step S09 in accordance with the restart of the cutting process. In addition, the threshold value exceeding count n is reset to 0 (zero). Thereby, the automatic operation of the cutting process of the processing device 4 and the operation of the automatic operation stabilizing system 1 are continued. However, it is necessary to accurately grasp the area that has already been machined and to take sufficient care to prevent the new cutting tool from colliding with the work material 6 .

Next, details of chatter vibration detection and chatter vibration suppression processing performed in steps S09 to S16 will be described using examples of measurement data and calculation data. FIG. 3 is an example of a time-series chart of the feed shaft motor current when chatter vibration is automatically suppressed after the occurrence of chatter vibration. This is stored as time-series data in the measurement signal 39 of the storage unit 3 in step S09 shown in FIG. This is an example of cutting the side surface of a plate-shaped work material having a thickness of about 100 mm and a length of about 3500 mm with an indexable milling tool having a plurality of cutting edges. The horizontal axis indicates the machining time [seconds], and the vertical axis indicates the feed shaft motor current value (A).

In the signal waveform of the feed axis motor current shown in FIG. 3, the current value increases from the machining time of about 5 seconds. This is because the servo amplifier 11b controls the feed shaft motor 10 to move the table 9 on which the work material 6 is mounted at the normal feed speed. A spike waveform 40 with a machining time of about 5 seconds is an overshoot at the start of motor rotation. After the spike-shaped waveform 40, the vertical width (hereinafter referred to as amplitude) of the feed shaft motor current waveform gradually expands, and becomes substantially constant after about 15 seconds of machining time.

Since the cutting tool 5 of this example is a milling tool, it is cut, and its machining is continuous cutting, and the cutting resistance changes periodically. The feed component force in the feed direction in which the work material 6 advances has the same tendency. For this reason, the feed shaft motor current changes periodically according to the feed component force in order to keep the feed speed constant. After the spike-shaped waveform 40, the amplitude of the signal waveform gradually increases because the cutting tool 5 gradually penetrates the work material 6 and the radial depth of cut of the cutting tool 5 increases. This is because the resistance increases. The reason why the amplitude of the signal waveform is substantially constant after the machining time is about 15 seconds is that the cutting force of the cutting tool 5 becomes substantially constant due to the constant radial depth of cut.

In the signal waveform of the feed shaft motor current shown in FIG. 3, a waveform 41 with a large amplitude can be seen at a machining time of about 135 seconds. This indicates that chatter vibration increased the fluctuation of the cutting resistance, and the feed shaft motor current changed according to the increase in fluctuation of the feed component force. In addition, the waveform 41 with a large amplitude has less variation within 10 seconds, and thereafter the amplitude does not increase significantly until the feed shaft motor current decreases to near 0 [A]. This indicates that the chatter vibration is suppressed within 10 seconds, and thereafter the chatter vibration is not generated or suppressed until the end of the machining process.

Next, FIG. 4 is an example of a time-series chart of the standard deviation of the feed shaft motor current when the chatter vibration is automatically suppressed after the occurrence of the chatter vibration in this embodiment. This is obtained by extracting the feed shaft motor current shown in FIG. 3 at intervals of one second and calculating the standard deviation. The abnormality determination threshold value 43 shown in FIG. 4 is set in advance based on existing data obtained in advance when chatter vibration occurs and data on occurrence of tool breakage. In the time-series chart of the standard deviation of the feed shaft motor current shown in FIG. 4, the waveform 42 of the standard deviation of the machining time of about 135 seconds corresponding to the waveform 41 with a large amplitude of the feed shaft motor current shown in FIG. , the abnormality determination threshold value 43 was exceeded. This makes it possible to detect the occurrence of chatter vibration. Note that, as described above, the standard deviation is one type of variation, and it is also possible to use other indices that indicate variation.

Further, the magnitude of the amplitude of the feed shaft motor current is the fluctuation of the feed shaft motor current, which is a variation. Chatter vibration and tool abnormality are detected by comparing this variation with a threshold as a feature amount. If the difference between the maximum value and the minimum value is used in this variation calculation method, even if the maximum value and the minimum value deviate greatly due to noise, etc., the difference between the maximum value and the minimum value will increase, causing chatter vibration. may be erroneously detected. On the other hand, the standard deviation can be calculated using a larger number of data, thereby minimizing the influence of greatly separated data such as noise. Therefore, as a method of calculating variations in the feed shaft motor current for detecting chatter vibration with high accuracy, it is preferable to use a standard deviation calculated from a large number of data, and the number of data is preferably 100 or more.

FIG. 5 is an example of a time series chart of the feed rate when the chatter vibration is automatically suppressed after the occurrence of the chatter vibration in this embodiment. This feed rate is data obtained separately from the NC device 12 of the processing device 4 . The standard deviation of the feed axis motor current shown in FIG. 4 exceeded the threshold at about 135 seconds of machining time, and chatter vibration was detected. This is the result.

Further, the normal feeding speed 45 and the abnormal feeding speed 46 are calculated based on the work material information acquired by the work material information acquisition unit 18 by the automatic operation stabilization system 1 . Here, the feed speed when chatter vibration was detected was set to 90% of the feed speed during normal operation. Lowering the cutting resistance is effective in suppressing chatter vibration, and lowering the feed rate reduces the feed amount per blade of the cutting tool, thereby reducing the cutting resistance. This suppresses chatter vibration. On the other hand, when the feed rate is lowered, the machining efficiency is lowered. Therefore, in consideration of both machining efficiency and chatter vibration suppression, it is preferable that the feed rate when chatter vibration is detected be 80 to 95% of the normal feed rate.

FIG. 6 is a time series chart of the standard deviation of the feed shaft motor current before and after chatter vibration occurs in this embodiment. This is obtained by extracting the standard deviation data of the feed shaft motor current for the machining time of 120 to 150 seconds in the range 44 shown in FIG. A marker (o) indicates a standard deviation calculated every second. Since the marker 47 exceeded the abnormality determination threshold value 43, it was determined that chatter vibration occurred, and the number of exceeding the threshold value n became 1, and the feed speed of the processing device 4 was changed to the feed speed at the time of abnormality.

Here, as described above, after the chatter vibration is detected, there is a time lag between changing the feed speed and then suppressing the chatter vibration. Three markers after the marker 47 exceed the abnormality determination threshold 43 . However, in step S17 shown in FIG. 2, since the number of exceeding the threshold value m for determining tool abnormality is set to 10 here, the tool is not determined to be abnormal, and chatter vibration is suppressed after that, so the standard deviation is reduced. . The time 48 from chatter vibration detection to chatter vibration suppression was about 5 seconds. No tool mark caused by chatter vibration was observed on the machined surface of the work material 6 from which this data was acquired, and no chipping of the cutting edge was observed on the cutting tool 5 either.

Next, the process of determining the machining state performed in step S12 shown in FIG. 2 will be described using an example of calculation data. FIG. 7 is an example of a time-series chart diagram of the average value of the feed shaft motor current in this embodiment. This is obtained by extracting the feed shaft motor current shown in FIG. 3 at intervals of 1 second and calculating the average value. Further, the machining state determination threshold value 49 is determined by comparing existing data obtained in advance when machining is in progress and when machining is stopped so that the respective states can be discriminated. When the average value of the feed axis motor current exceeded the machining state determination threshold value 49 once and then became smaller than the machining state determination threshold value 49 continuously, it was determined that the machining was stopped. Here, it was determined that the machining was completed when the state where the value became smaller than the machining state determination threshold value 49 exceeded 10 consecutive times (for 10 seconds). A waveform 50 is a waveform determined as the end of machining.

Next, the tool abnormality determination and the processing after the tool abnormality detection performed in steps S09 to S14 and steps S17 to S19 shown in FIG. 2 will be described using examples of measurement data and calculation data.

FIG. 8 is an example of a time series chart of the feed shaft motor current when the tool abnormality is detected and the machining is stopped in this embodiment. This is an example of cutting the side surface of a plate-shaped work material 6 having a thickness of about 120 mm and a length of about 3000 mm with an indexable milling tool having a plurality of cutting edges. This is the measured waveform of the feed axis motor current when it is determined that the tool is abnormal during machining, the feed is stopped at the machining time of 45 seconds, the cutting tool 5 is separated from the work material 6, and the tool is retracted to a safe position. is.

FIG. 9 is an example of a time-series chart of the standard deviation of the feed axis motor current when machining is stopped after detecting a tool abnormality in this embodiment. is detected and machining is stopped. In addition, FIG. 9 shows the standard deviation calculated by extracting the feed axis moh current shown in FIG. 8 every one second. A marker (o) in the figure indicates the standard deviation calculated every second. The abnormality determination threshold value 43 was exceeded at the marker 51 . Since the threshold value is exceeded for the first time, the normal feed speed 53 is automatically changed to the abnormal feed speed 54 as shown in FIG. Since the thickness of the work material 6 is different, the feeding speeds in the normal state and in the abnormal state shown in FIGS. 5 and 10 are different.

Here, the standard deviation of the feed shaft motor current shown in FIG. 9 continued to exceed the abnormality determination threshold value 43 even after the feed speed was changed to the abnormal one. With the marker 52, it was determined that the tool abnormality occurred because the number of exceeding threshold n reached the threshold exceeding number m for judging tool abnormality set to 10 times or more. After that, the feed rate was set to 0 (m/min) and the cutting tool 5 was retracted to a safe position. Since there is a time lag before the feed speed of the processing device 4 is set to 0 (m/min), two markers exceeding the threshold are seen after the marker 52, but the feed speed decreases after that. When the retracted cutting tool 5 was checked, chipping of a maximum of about 0.35 mm was found on the cutting edge of the cutting tool 5 . However, no breakage was found in the body of the cutting tool 5, and it was possible to use it again for cutting by replacing only the cutting edge.

Next, the work piece dimension calculation processing performed in step S04 shown in FIG. 2 will be described using acquired data. Here, FIG. 11 is an example of data of the work material 6 acquired by the work material information acquisition unit 18 in this embodiment. FIG. 11 shows image data acquired from obliquely above the side surface of the plate-shaped work material 6 by the work material information acquisition unit 18 consisting of a camera.

Here, an example of a method of calculating the dimensions of the side surface 56, which is the part to be processed, from this image will be described. First, processing such as gray scale conversion and black and white reversal is performed so that the edges that become the sides of the plate-shaped work material 6 can be easily identified. Next, after each edge is extracted by the edge detection method, a straight line 59 that is the upper side of the side surface and a straight line 58 that is the lower side of the side surface are selected. Then, the distance 61 between the straight lines 59 and 58 is calculated. Note that the unit of the distance obtained from the image data is the pixel of the image data. For this reason, information on the work material 6 made of a plate material whose dimensions are measured in advance and the thickness is known is acquired by the work material information acquisition unit 18 at the same angle of view, and the mm conversion value of the pixel in the image data is calculated. to set. As a result, it becomes possible to calculate the dimension (mm) of the side surface of the part to be processed from the newly acquired image data of the work material 6 .

The second straight line 59 from the top of the image data is the upper side of the side surface of the plate-like work material 6, and the lowest straight line 58 is the lower side of the side surface. Even with stacked plate-shaped work materials, it is possible to select straight lines that will be the upper and lower sides of the side surface for calculating the total thickness according to the same selection rule. Further, if the image data contains information such as a jig for fixing the work material 6, it is preferable to cut out the image so that the area other than the work material 6 becomes a space before processing. Furthermore, in that case, it is better to adjust the timing of acquiring the image data, etc., so that the position where the space other than the work material 6 is the same as possible with respect to the image data, so that the cutout position is the same. preferred.

Next, the processing for calculating the feed rate based on the dimensions of the work piece performed in step S05 shown in FIG. 2 will be described using an example of the calculation rule. FIG. 12 shows an example of a calculation rule for calculating the feed rate based on the dimensions of the work material in this embodiment. In this figure, the horizontal axis indicates plate thickness, and the vertical axis indicates feed rate. The reference plate thickness is normalized to 1.0, and the corresponding feed rate is also normalized to 1.0. Further, the plate thickness on the horizontal axis is the total thickness when the plate-like cut materials 6 are piled up.

Here, for plate thicknesses of 0.5 to 2.0, the feed rate is varied in proportion to the plate thickness so that the machining load (cutting resistance) becomes uniform with a plate thickness of 1.0 as the reference. However, when the plate thickness is 0.5 or less, if the feed speed is set according to the plate thickness ratio, the feed speed becomes too high, and the load on the tip of the cutting tool 5 increases due to the increase in the feed amount per blade. Since there is a risk of damage if the plate thickness is 0.5 or less, the plate thickness is set constant.

For example, when a plate thickness of 100 mm is used as the reference (1.0), the feed speed of the work material 6 with a plate thickness of 120 mm is set to about 83% of the plate thickness of 100 mm according to the plate thickness ratio, The feeding speed of the cut material is set to about 133% of the plate thickness of 100 mm based on the plate thickness ratio. As a result, when the thickness of the work material 6 is large, the feed rate is lowered to reduce the load applied to the cutting tool, thereby suppressing tool breakage. In some cases, the feed rate can be increased to improve machining efficiency.

In addition, instead of setting the feed rate as a ratio to the plate thickness, the calculation rule may be such that the range of plate thickness is divided and the feed speed is set stepwise for each range of plate thickness. Absent. Also, what is shown here is the normal feed speed, and the abnormal feed speed is set to, for example, 80 to 95% of the normal feed speed based on the normal feed speed, as described above. do.

Next, an operation screen (GUI screen) displayed on the display unit 14 of the automatic driving stabilization system 1 will be described. FIG. 13 is a diagram showing a GUI (Graphical User Interface) screen of the display unit 14 in the automatic driving stabilization system 1 in this embodiment. It is an outline of the GUI screen showing the operation of the automatic driving stabilization system 1, the set processing conditions, and the operating state on the screen of the display unit 14. FIG. The GUI screen 801 includes an operation start button 802 for starting operation of the automatic operation stabilization system 1, an operation interruption button 803 for ending operation, a workpiece size display section 804, a normal feed speed display section 805, An abnormal feed speed display unit 806 , a tool abnormality detection light 807 , and a chatter vibration detection light 808 are provided.

The work material dimension display section 804 displays the dimensions of the work material 6 calculated using the information acquired by the work material information acquiring section 18 . The normal feed speed display portion 805 displays the normal feed speed calculated according to the dimensions of the work piece 6, and the abnormal feed speed display portion 806 displays the abnormal feed speed.

Here, in step S11 shown in FIG. 2, when chatter vibration is detected by exceeding the abnormality determination threshold value, the chatter vibration detection light 808 is turned on, and when the chatter vibration is suppressed, it is turned off again. Further, when the tool abnormality is determined in step S17 shown in FIG. 2, the tool abnormality detection light 807 is turned on. As a result, it is possible to visually inform the person who monitors the cutting process whether or not a tool abnormality has occurred.

According to this embodiment, chatter vibration can be detected and automatically suppressed by the acquired feed shaft motor current in cutting a plate-shaped work material having irregular dimensions. As a result, chatter vibration can be detected with high accuracy without being affected by disturbances due to environmental factors, as compared with a conventional chatter vibration detection device using an acceleration sensor or a microphone. In addition, since tool abnormalities can be detected and the spread of tool damage can be suppressed, it is possible to stabilize automatic operation of cutting work, and it is possible to reduce the cost of countermeasures related to processing defects and reduce tool costs. .
In addition, since the dimensions of the work material can be automatically acquired and the feed rate can be set according to the dimensions for cutting, compared to machining at a constant feed rate, machining efficiency can be improved and the cutting tool can be Optimizing the cutting resistance applied to this can contribute to suppressing tool breakage. Moreover, when the operator adjusts the feed rate according to the dimensions of the work material, it is possible to save the labor of the operator.

Although an example in which the feed shaft motor current is used as the measurement signal has been described, the power value may be processed in the same way. The unit of the parameter is changed from current value (A) to power value (W), and the rest is the same.

Also, although the example of controlling the feed rate after detecting chatter vibration has been described, chatter vibration can also be suppressed by controlling the number of revolutions of the cutting tool 5 (the number of revolutions of the main shaft 7). In that case, the chatter vibration can be suppressed by changing the rotation speed when chatter vibration is detected to about 80 to 95% of the normal rotation speed. Become. It is also possible to suppress chatter vibration by simultaneously controlling the feed speed and rotation speed after the chatter vibration is detected.

It is also possible to determine whether the tool is abnormal by repeatedly exceeding the abnormality determination threshold value after the feed speed and the rotational speed of the main shaft 7 have been controlled.

This is the end of the description of this embodiment. According to this embodiment, in a processing apparatus for cutting a workpiece with irregular dimensions, chattering is detected by determining an increase in variation in feed axis motor current as a threshold value. Vibration is detected, and machining conditions are automatically controlled and changed to suppress chatter vibration. Further, the increase in variation in the feed axis motor current is judged again with a threshold value, and if the number of times the threshold value is exceeded exceeds a predetermined number of times, it is judged that the tool is abnormal and the tool breakage can be detected. As a result, it is possible to suppress chatter vibration and the spread of tool damage, and to stabilize automatic operation. In addition, the dimensions of work materials with irregular dimensions can be automatically acquired, and the feed rate suitable for the dimensions of the work material can be automatically set, making it possible to improve the efficiency of cutting work. .

DESCRIPTION OF SYMBOLS 1... Automatic operation stabilization system, 2... Calculation part, 3... Storage part, 4... Processing apparatus, 5... Cutting tool, 6... Work material, 7... Spindle, 8... Spindle motor, 9... Table, 10... Feed Axis motor 11a Servo amplifier 11b Servo amplifier 12 NC unit 13 Input unit 14 Display unit 15 Communication unit 16 Measuring unit 17 Automatic operation stabilizing device 18 Work piece Material information acquisition unit 21 Work material size calculation unit 22 Machining condition calculation unit 23 Measurement signal processing unit 24 Abnormal signal processing unit 25 Machining device command unit 31 Work material size calculation program , 32... Machining condition calculation program, 33... Measurement signal processing program, 34... Abnormality detection program, 35... Machining device command program, 36... Control parameter, 37... Work material information, 38... Work material dimensions, 39... Measurement Signal 40 Spike waveform 41 Large amplitude waveform 42 Standard deviation waveform 43 Abnormality judgment threshold 45 Normal feed speed 46 Abnormal feed speed 49 Machining state judgment Threshold 53 Feed speed in normal state 54 Feed speed in abnormal state 56 Side surface of work material 61 Distance between straight lines 801 GUI screen 802 Operation start button 803 Operation interrupt button 804 Workpiece dimension display 805 Normal feed speed display 806 Abnormal feed speed display 807 Tool error detection light 808 Chatter vibration detection light

Claims (15)

A cutting tool is mounted on a spindle, the cutting tool is rotated together with the spindle, and an automatic operation stabilizing device that outputs a command to control cutting to a processing device that performs cutting of a work material,
a work material size calculation unit that calculates the size of the work material;
a machining condition calculation unit that calculates a feed rate indicating the relative movement speed of the work material in the cutting process based on the dimensions of the work material;
Of the feed speed and the rotation speed of the main shaft, according to the occurrence of chatter vibration in the processing device determined based on the variation in the feed shaft motor current, which is the current of the feed shaft motor of the processing device in the cutting process An automatic operation stabilizing device comprising a processing device command unit that outputs a change command to change at least one of the processing devices to the processing device. In the automatic operation stabilization device according to claim 1,
The automatic operation stabilizing device further includes a measurement signal processing unit that extracts the feed shaft motor current at predetermined time intervals and calculates variations in the feed shaft motor current. In the automatic operation stabilization device according to claim 2,
The measurement signal processing unit compares the variation in the feed shaft motor current with a predetermined abnormality determination threshold, and determines chatter vibration according to the comparison result. In the automatic operation stabilization device according to claim 3,
an abnormality signal processing unit that detects an abnormality of the tool of the processing apparatus according to a comparison result between the variation in the feed axis motor current and the abnormality determination threshold after the change command is output;
The processing device command unit is an automatic operation stabilizing device that outputs a change command according to the tool abnormality. In the automatic operation stabilization device according to claim 4,
The processing device command unit is an automatic operation stabilizing device that outputs a change command based on the dimensions of the work material. A cutting tool is mounted on a spindle, the cutting tool is rotated together with the spindle, and an automatic operation stabilization device using an automatic operation stabilizing device that outputs a command to control cutting to a processing device that performs cutting of a work material. In the operation stabilization method,
Calculate the dimensions of the work material by the work material dimension calculation unit,
calculating, by a machining condition calculation unit, a feed rate indicating a relative movement speed of the work material in the cutting process, based on the dimensions of the work material;
The feed rate and the A method for stabilizing automatic operation, wherein a change command for changing at least one of the rotation speeds of a spindle is output to the processing device. In the automatic driving stabilization method according to claim 6,
Further, an automatic operation stabilizing method of extracting the current of the feed shaft motor current at predetermined time intervals by a measurement signal processing unit and calculating the variation of the feed shaft motor current. In the automatic driving stabilization method according to claim 7,
A method for stabilizing automatic operation, wherein the measurement signal processing unit compares the variation in the feed shaft motor current with a predetermined abnormality determination threshold, and determines chatter vibration according to the comparison result. In the automatic driving stabilization method according to claim 8,
Further, after outputting the change command, the abnormality signal processing unit detects a tool abnormality of the processing device according to a result of comparison between the variation in the feed axis motor current and the abnormality determination threshold,
A method for stabilizing automatic operation, wherein the processing device command unit outputs a change command according to the tool abnormality. In the automatic driving stabilization method according to claim 9,
An automatic operation stabilizing method, wherein the processing device command unit outputs a change command based on the dimensions of the work material. An automatic operation stabilizing device that outputs a command to control cutting to a processing device that mounts a cutting tool on a spindle and rotates the cutting tool together with the spindle to cut the work material,
a work material size calculation unit that calculates the size of the work material;
a machining condition calculation unit that calculates a feed rate indicating the relative movement speed of the work material in the cutting process based on the dimensions of the work material;
Of the feed rate and the number of rotations of the main shaft, according to the occurrence of chatter vibration in the processing device determined based on the variation in the feed shaft motor current, which is the current of the feed shaft motor of the processing device in the cutting process A program for functioning as a computer having a processing device command unit that outputs a change command for changing at least one of the processing devices to the processing device. The program according to claim 11,
Further, a program for operating a measurement signal processing unit that extracts the current of the feed shaft motor current at predetermined time intervals and calculates variations in the feed shaft motor current. The program according to claim 12,
A program that causes the measurement signal processing unit to compare variations in the feed shaft motor current with a predetermined abnormality determination threshold, and to determine chatter vibration according to the comparison result. The program according to claim 13,
Furthermore, after outputting the change command, operating an abnormality signal processing unit for detecting a tool abnormality of the processing apparatus according to a result of comparison between the variation in the feed axis motor current and the abnormality determination threshold,
A program for causing the processing device command section to output a change command corresponding to the tool abnormality. 15. The program according to claim 14,
A program for causing the processing device command unit to output a change command based on the dimensions of the work material.

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