JP6637689B2 - Machine tool tool state determination device - Google Patents

Description

  The present invention relates to a tool state determination device that determines the state of a tool in a machine tool that processes a workpiece while rotating a tool mounted on a spindle.

2. Description of the Related Art In a machine tool that cuts a work by rotating a tool, if the tool is damaged, a processing defect that cannot process the work into a desired shape occurs. In addition, if the feed axis continues to operate in a situation where the workpiece cannot be removed due to damage to the tool, the tool and the workpiece will collide, and the machine will be damaged. For this reason, the load of the spindle motor, which is considered to represent the state of the tool most, is displayed on the monitor of the NC device, and the machine operator judges the quality of the cutting state, and the machine monitors the spindle load and stops the feed shaft. It is generally performed.
For example, Patent Document 1 discloses a method of displaying the load of a spindle motor in a bar graph by color-coding a specific area according to the load value when displaying the load on a display device in an analog manner. Thereby, the state of the load can be intuitively grasped by the color. Patent Literature 2 discloses a tool life predicting device that obtains an average value of a processing load using a cutting dynamometer, sets an allowable range of load variation, and outputs an abnormal signal when the allowable range is exceeded. The presence or absence of a remarkable change in the processing load can be determined from the number of output abnormal signals. Patent Literature 3 discloses a load monitoring method in which tool wear is determined based on an average value obtained by subtracting current during acceleration / deceleration of a load current value of a spindle motor. Here, upper and lower limits of the current value are provided, and a comparison is made with this value to determine an abnormality and output a message to the monitor.

JP-A-58-120455 JP-A-5-329748 JP-A-7-24694

In the load display of the spindle motor disclosed in Patent Document 1, there is an advantage that the magnitude of the load value can be determined by color, but there is no relationship between the color and the state of the tool. For this reason, it is necessary to know in advance which color will damage the tool. In general, the spindle load fluctuates due to acceleration or deceleration of the spindle or an instantaneous increase in load during machining. On the other hand, since the amount of change in the state of the tool applied to the load on the spindle motor may be very small, it is difficult to read the bar graph.
Further, in Patent Document 2, it is necessary to set a load variation in advance in order to determine that the tool is abnormal, but it is difficult to set the value in, for example, machining of a first product. In Patent Document 3, similarly to Patent Document 2, it is necessary to set a current value for determining an abnormality in advance.

  Therefore, an object of the present invention is to provide a tool state determination device for a machine tool that can easily grasp the state of a tool without having to prepare advance data such as a processing load in advance.

In order to achieve the above object, the invention according to claim 1 is directed to a machine tool that mounts a tool having a plurality of blades on an outer periphery to a main spindle and rotates the tool together with the main spindle to process a workpiece. A tool state determination device for determining a state of a tool,
Spindle load detecting means for detecting the load of the spindle for a predetermined number of rotations ,
Spindle load processing means for extracting an average value of the spindle load detected by the spindle load detection means and a rotation frequency component that is a magnitude of a frequency component corresponding to the rotation frequency of the spindle in the spindle load for each number of times of detection ; ,
A storage unit that stores an average value and a rotation frequency component of the spindle load extracted by the spindle load processing unit under the same processing conditions for each of the detection times ,
When the average value of the spindle load for each of the number of detections stored in the storage means continuously increases and the rotational frequency component of the spindle load for each of the number of detections becomes continuously constant, tool wear occurs. And determination means for determining
According to a second aspect of the present invention, in the configuration of the first aspect, the determination unit is configured such that an average value of the spindle load for each of the number of detections increases continuously , and a rotation frequency component of the spindle load is continuous. The tool wear is determined when it is continuously constant after the decrease.
According to a third aspect of the present invention, in the configuration of the first or second aspect, the spindle includes a spindle load calculation command described in a machining program and a program interpreting unit that reads a machine position at which the spindle load calculation command is executed. The load processing means extracts an average value of the spindle load and a rotation frequency component based on the spindle load calculation command interpreted by the program interpreting means.
According to a fourth aspect of the present invention, in any one of the first to third aspects, a notifying unit for notifying a result of the determination by the determining unit is provided.

According to the present invention, the increase in the average value of the spindle load and the stabilization of the rotation frequency component are determined as the wear of the tool, so that it is not necessary to prepare advance data such as the machining load in advance, and the state of the tool can be changed. Easy to understand.
In particular, according to the third aspect of the present invention, the spindle load is measured during the machining program and the average value and the rotation frequency component are automatically extracted at predetermined machine coordinates. When machining with a program, the spindle load can always be measured at the same machining position. In addition, by specifying the machining position, it is possible to avoid measurement of an unstable spindle load when the tool enters the work, for example.

It is a block diagram of a machine tool. It is sectional drawing of groove processing by an end mill. It is an image figure of a time progress of a spindle load in a normal tool. It is an image figure of a time passage of a spindle load in a tool with runout. It is an image figure of the average value of the spindle load which rose with progress of tool wear, and the rotation frequency component which decreased. It is explanatory drawing which arranged the average value of the spindle load and the measured value of a rotation frequency component in the tool wear state. It is an explanatory view of a tool state monitor screen. It is a flowchart of a calculation process until it determines a tool state. FIG. 9 is an explanatory diagram of an example of a program for displaying a tool state.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating an example of a machine tool. A main shaft housing 1 of the machine tool is provided with a main shaft 6 rotatable by a main shaft motor 2, and a tool 3 is attached to a tip of the main shaft 6. The work 4 is fixed on the table 5, and by moving the table 5, the tool 3 and the work 4 are relatively moved to process the work 4.
Reference numeral 11 denotes an NC device that controls a machine tool. The NC device 11 operates the machine according to the stored NC program 12 to process the work 4 and also has a function as a tool state determination device of the present invention. .

In the NC device 11, the NC program 12 is executed by a program interpreting unit 13 as a program interpreting unit, the machine control command is interpreted, and the NC program 12 is transmitted to a feed axis control unit 15 that controls the feed axis of the spindle 6 and the table 5. The target position command and the feed speed command are transferred to the function generator 14, and a rotation speed command is output to the spindle controller 16 for controlling the spindle 6.
Reference numeral 17 denotes a spindle load detection unit as spindle load detection means. The spindle load detection unit 17 is connected to the spindle control unit 16 and combines a load signal corresponding to the required power or required torque of the spindle motor 2 with the rotation frequency. To detect.

Reference numeral 18 denotes a spindle load processing unit serving as a spindle load processing unit. The spindle load processing unit 18 detects a spindle load at an arbitrary number of spindle rotations based on the load signal detected by the spindle load detection unit 17 and the rotation frequency. The extraction processing of the average value and the rotation frequency component is performed. If the NC program 12 describes a command to execute the process of extracting the average value of the spindle load and the rotation frequency component for an arbitrary number of spindle rotations in the spindle load processing unit 18, the program interpretation unit 13 The load processing unit 18 is instructed to perform the extraction processing. The average value of the spindle load and the value of the rotation frequency component calculated (extracted) by the spindle load processing unit 18 are recorded in a storage unit 19 as storage means.
Reference numeral 20 denotes a wear determining unit serving as a determining unit. The wear determining unit 20 determines that tool wear has occurred when the average value of the spindle load increases and the rotational frequency component of the spindle load becomes constant. 19, and the recording result is displayed on a display screen 21 as a notifying means.

Here, the spindle load generated in the processing will be described with reference to FIGS. FIG. 2 is a schematic diagram for performing groove machining using the tool 3 as a two-edge end mill. The end mill attached to the main shaft 6 moves in the feed direction of FIG. 2 while rotating by operating the table 5 on which the work 4 is mounted, so that a groove having an end mill diameter is formed in the work. If the end mill has two blades and the shape of the blades is uniform with respect to the rotation center of the main shaft 6, the main shaft load will undergo two equal increases and decreases during one rotation of the main shaft 6 (FIG. 3). .
However, since the center of rotation of the main shaft 6 and the center of the end mill are actually displaced, the end mill whirls with respect to the rotation of the main shaft 6. Therefore, in the case of two blades as shown in FIG. 2, the cut amount decreases with one sheet, and conversely, the cut amount increases with the other blade, resulting in a waveform of the rotational frequency component as shown in FIG. When the wear of the blade advances due to the processing, the load increases as shown by a dotted line in FIG. 5, while the wear of the blade which has been largely cut advances, and the run-out with respect to the center of the main shaft of the end mill decreases. As a result, the spindle load generated at each cutting edge approaches, so that the rotational frequency component of the spindle load decreases and approaches the averaging.

FIG. 6 is a graph in which the average value of the spindle load and the value of the rotational frequency component of the spindle load in the actual machining are plotted every time the same workpiece is machined. The vertical axis represents the spindle load (rotational frequency component of the spindle load, the average value of the spindle load), the horizontal axis represents the wear larger the numerical a progressive degree of wear of the tool is in progress.
From this figure, the average value of the spindle load increases as the wear progresses, but the rotational frequency component of the spindle load becomes constant beyond 3 after the degree of wear decreases. Here, the value of the horizontal axis 4 corresponds to the use limit of the tool in a state where the wear is progressing and chipping is occurring. Therefore, the condition under which the average value of the spindle load increases and the rotational frequency component of the spindle load becomes constant is a measure of the tool life. In addition, it is conceivable that the minute deviation between the rotation center of the main spindle and the center of the end mill changes depending on individual differences between the main spindle, the tool holder, and the end mill. However, as long as the same type is selected, the deviation amount occurs within a certain range, and thus the condition under which the rotational frequency component of the spindle load is constant can be said to be a standard of the tool life.

Therefore, the tool state monitor screen on the display screen 21 can be displayed as shown in FIG. 7 based on the graph of FIG. In FIG. 7, the upper and lower graphs show the average value of the main shaft load, and the lower graph shows the load fluctuation (rotation frequency component of the main shaft load ). Here, since the average value of the spindle load increases and the load variation is constant at the fourth and fifth measurement times, the tool state is determined and displayed as "wear" at the upper right.
The display screen 21 is a touch panel. The lower part of the display screen 21 displays a “measure” button for measuring and storing a spindle load by a push operation at an arbitrary timing, storing the plot, and plotting the spindle load on a graph, and a push operation. And a "clear" button for deleting the spindle load.

Next, a procedure for determining the tool state in FIG. 7 by the spindle load processing unit 18 and the wear determination unit 20 will be described with reference to the flowchart in FIG.
First, it is determined whether there is a spindle load calculation command in the NC program 12 (S11). This spindle load calculation command is performed as shown in "M ^**** , 50" in FIG. ^{In ****} , any number that can be used in the M command is entered. “M ^**** ” is a calculation command, and is executed simultaneously with the program block described next to the calculation command. By describing a numerical value of 1 to 100 (%) after “M ^**** ”, it is possible to calculate a spindle load during axis movement by executing a program block. If “M ^**** , 50”, the spindle load calculation command is executed when the axis movement distance reaches 50%.
If there is a calculation command in the determination of S11, in S12, the spindle load is measured by the preset number of spindle rotations.
Next, an average value of the spindle load is calculated in S13, and a rotation frequency component of the spindle load is calculated in S14. Then, in S15, the average value of the spindle load and the rotation frequency component are displayed on the display screen 21 and stored in the storage unit. In step S16, the wear determination unit 20 determines the state of the tool from the result of recording the spindle load. In FIG. 7, since the average value of the spindle load increases and the rotation frequency component decreases and then becomes constant, it is determined to be “wear”.

  As described above, according to the NC device 11 of the above-described embodiment, the spindle load detection unit 17 that detects the load on the spindle, and the spindle load that extracts the average value and the rotation frequency component of the spindle load detected by the spindle load detection unit 17. A processing unit 18, a storage unit 19 that stores the spindle load average value and the rotation frequency component extracted by the spindle load processing unit 18 under the same machining conditions, and an average spindle load stored in the storage unit 19. By providing the wear determination unit 20 that determines that the tool wears when the rotation frequency component is increased and the rotation frequency component becomes constant, there is no need to prepare advance data such as a machining load in advance, thereby simplifying the state of the tool. Can be grasped.

In particular, here, since the spindle load is measured during the NC program and the average value and the rotation frequency component are automatically extracted at predetermined machine coordinates, for example, when machining a large number of works such as mass production machining with the same program, The spindle load can always be measured at the same machining position. In addition, by specifying the machining position, it is possible to avoid measurement of an unstable spindle load when the tool enters the work, for example.
Further, by notifying the determination result of the wear determining unit 20 on the display screen 21, the operator can easily determine the timing of tool change.

The notification of the tool wear is not limited to the display on the tool state monitor screen, but may be performed by an alarm sound, a synthetic voice, or the like.
Also, in the above embodiment, the tool state is automatically determined by measuring the spindle load during the NC program. The determination may be made by monitoring the tool state at the timing of (1).
Further, in the above embodiment, the tool state determination device is realized by the NC device and the tool state monitor screen is displayed on the display screen of the NC device. For example, the spindle load processing unit, the storage unit, and the wear determination unit are provided by the NC device. Apart from this, it may be provided in an external device (such as a personal computer) connected to the NC device by wire or wirelessly, and the spindle load may be monitored and reported by the external device. In this way, the tool status of a plurality of machine tools can be grasped by one external device.

  1. Spindle housing, 2. Spindle motor, 3. Tool, 4. Work, 5. Table, 6. Spindle, 11. NC device, 12. NC program, 13. Program interpreter , 14 function generator, 15 feed axis controller, 16 spindle controller, 17 spindle load detector, 18 spindle load processor, 19 storage unit, 20 wear determination Part, 21 ... display screen.

Claims (4)

A tool state determination device for determining a state of the tool in a machine tool that mounts a tool having a plurality of blades on an outer circumference on a main spindle and rotates the tool together with the main spindle to process a workpiece,
Spindle load detecting means for detecting the load of the spindle for a predetermined number of rotations ,
Spindle load processing means for extracting an average value of the spindle load detected by the spindle load detection means and a rotation frequency component that is a magnitude of a frequency component corresponding to the rotation frequency of the spindle in the spindle load for each number of times of detection ; ,
A storage unit that stores an average value and a rotation frequency component of the spindle load extracted by the spindle load processing unit under the same processing conditions for each of the detection times ,
When the average value of the spindle load for each of the number of detections stored in the storage means continuously increases and the rotational frequency component of the spindle load for each of the number of detections becomes continuously constant, tool wear occurs. And a determining means for determining the condition of the tool. The determination means increases with the continuous mean value of the spindle load for each of the detection times, and the tool when the rotational frequency component becomes constant continuously after continuously decreases the spindle load wear and The tool state determination device for a machine tool according to claim 1, wherein the determination is performed.   A spindle load calculation command described in a machining program and a program interpreting means for reading a machine position at which the spindle load calculation command is executed, wherein the spindle load processing means includes a spindle load calculation command interpreted by the program interpretation means. 3. The tool state determination device for a machine tool according to claim 1, wherein an average value and a rotation frequency component of the spindle load are extracted based on the following.   The tool state determination device for a machine tool according to claim 1, further comprising a notification unit configured to notify a result of the determination by the determination unit.

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