JP6967321B1 - Machine tool current measurement system and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for detecting a tool abnormality of a tool used without connecting an external device to an NC device in machining using a plurality of types of tools by a machine tool. SOLUTION: This is a current measuring system for a machine tool in which a first current sensor and a second current sensor are connected to an information processing device, respectively, and the work is centered on a main axis while changing a plurality of types of tools. The machine tool that is driven to rotate as the center of the electric current is the first motor for driving the member when changing the position of the member to which the tool is attached, and the operation for changing multiple types of tools. The information processing device includes the current of the first motor measured by the first current sensor and the current of the second motor measured by the second current sensor, respectively. The time history waveform is overlapped by matching the elapsed time, and the current of the first motor measured by the first current sensor in the analysis process is generated when the operation is for changing multiple types of tools. A current measurement system for machine tools that detects tool abnormalities for each type of tool by cutting out each signal and comparing non-negative function values with the current value of each cutting section as an argument for each number of times the work is machined. [Selection diagram] Fig. 1

Description

The present invention relates to a technique for measuring a current flowing through a motor of a machine tool that performs machining with a cutting tool.

Measurement techniques using various sensors have been developed for the purpose of intelligentizing machine tools that perform machining with cutting tools (hereinafter, may be referred to as "tools"). In particular, due to its low cost and ease of handling, measurement of the current flowing through the motor of a machine tool has been conventionally performed. By estimating the load applied to the tool from the measured current value of the motor, the progress of wear of the tool is estimated. Attempts have also been made to estimate abnormal phenomena such as broken or chipped tools due to sudden and instantaneous changes in the current value of the motor.

Conventionally, in a machine tool that performs cutting by the relative motion of the work (work material) to be machined and the tool, tool wear progresses by repeatedly using the same tool, and the tool is eventually chipped or damaged. do. Therefore, for tools used in machine tools, the number of machining times (once for each machining of work material), which is a guideline for replacement (replacement with the same new tool) recommended by the tool maker. Although it is counted), the optimum tool change time differs depending on the machining method and machining target, so it is required to estimate the optimum tool change time based on the load applied to the tool during cutting. Was there.

Here, NC (numerical control) is performed under the condition that the load of the rotating spindle on which the tool is mounted is detected for a preset number of rotations, and the average value of the spindle load and the rotation frequency component are continuously constant values. A technique for determining tool wear of a machine tool is disclosed (see Patent Document 1).
Further, a technique for determining tool wear by comparing a preset active power waveform of a motor for driving a spindle with an active power waveform of a motor for driving a spindle during machining of a workpiece is disclosed (Patent Document 2). reference).
Further, a technique for providing a machine tool that detects a state in which a tool provided on a rotating spindle is in contact with a work and detects the degree of tool wear by using the degree of change in the tool load applied to the spindle during contact. Is disclosed (see Patent Document 3).

Japanese Patent No. 6637689 Japanese Unexamined Patent Publication No. 2006-821154 Japanese Unexamined Patent Publication No. 2019-30954

However, since the method described in Patent Document 1 needs to use the frequency information of the time series data collected by the acceleration sensor, it is difficult to apply it to the time series data collected by the current sensor.
In addition, when applying to cutting using multiple tools, it is not possible to distinguish individual tools, so it cannot be applied as it is to machining performed at the actual production site. I can say.

Similarly, in the method described in Patent Document 2, there is no reference to a method for discriminating individual tools for machining using a plurality of types of tools. Therefore, in machining using a single tool. Although effective, it cannot be applied as it is to machining using multiple types of tools.

The method described in Patent Document 3 can be applied to machining using a plurality of types of tools by connecting an external device to an NC device provided in a machine tool and acquiring tool change information. However, since the connection of an external device to the NC device is regarded by the machine tool maker as a modification to the machine tool, it is rarely used at the machine tool site.

An object of the present invention is to detect a tool abnormality of a tool used in an actual production site, such as cutting using a plurality of types of tools by a machine tool, without connecting an external device to the NC device. It is to provide the technology to detect.

The machine tool current measurement system of the present invention
A machine tool current measurement system in which the first current sensor and the second current sensor are connected to an information processing device, respectively.
A machine tool that rotates and drives a workpiece around a spindle while changing multiple types of tools is a first motor for driving a member when changing the position of the member to which the tool is attached. Equipped with a second motor to control the operation for changing multiple types of tools,
The information processing device matches the elapsed time of each time history waveform of the current of the first motor measured by the first current sensor and the current of the second motor measured by the second current sensor. The current of the first motor measured by the first current sensor in the analysis process is cut out for each signal generated during the operation for changing multiple types of tools, and each cutting section is cut out. By comparing non-negative function values with the current value of the current as an argument for each number of times the workpiece is machined, tool abnormalities are detected for each type of tool.
The above-mentioned member is, for example, a tool base of an NC lathe or the like. The time to change the position of the member is, for example, the movement of the tool table of the NC lathe in the Z-axis direction and the X-axis direction.

The current measuring method of the machine tool of the present invention is
Multiple types of tools, including a first motor to drive the member when changing the position of the member to which the tool is attached and a second motor to control the operation for changing the multiple types of tools. It is a current measurement method for machine tools that rotate and drive the work around the spindle while changing the speed.
The information processing device to which the first current sensor and the second current sensor are connected respectively has the current of the first motor measured by the first current sensor and the second measured by the second current sensor. The process of superimposing each time history waveform with the current of the two motors by matching the elapsed time, and
In the information processing, the information processing device cuts out the current of the first motor measured by the first current sensor for each signal generated during the operation for changing multiple types of tools, and each cut-out section. It has a process of detecting a tool abnormality for each type of tool by comparing the non-negative function value with the current value of.

According to the present invention, it is possible to provide a technique for detecting a tool abnormality of a tool used in machining using a plurality of types of tools by a machine tool.

It is a block diagram of the current measurement system of the machine tool in 1st Embodiment of this invention. It is a schematic diagram of the machine tool in the 1st Embodiment of this invention. It is a block diagram explaining the signal flow in 1st Embodiment of this invention. It is a figure which shows the time history waveform of the signal of the current flowing through a spindle motor and the current flowing through a servomotor in the first embodiment of the present invention. It is explanatory drawing of the transition of the load feature amount for each type of a tool in the 1st Embodiment of this invention. It is a figure which shows the display screen example of the display device in 1st Embodiment of this invention. It is a flowchart which shows the flow of the current measuring method of the machine tool in the 2nd Embodiment of this invention. It is a block diagram of the current measurement system of the machine tool in the 2nd Embodiment of this invention. It is a schematic diagram of the machine tool in the 2nd Embodiment of this invention. It is a block diagram explaining the signal flow in the 2nd Embodiment of this invention. It is a figure which shows the time history waveform of the signal of the current flowing through a spindle motor and the current flowing through a servomotor in the second embodiment of the present invention. It is explanatory drawing of the transition of the load feature amount for each type of a tool in the 2nd Embodiment of this invention. It is a figure which shows the display screen example of the display device in the 2nd Embodiment of this invention. It is a flowchart which shows the flow of the current measuring method of the machine tool in the 2nd Embodiment of this invention.

Hereinafter, the machine tool current measurement system according to the first embodiment of the present invention will be described in detail with reference to the drawings.
As a machine tool, NC lathe is assumed.

FIG. 1 is a configuration diagram of a current measurement system 10 of a machine tool 1 according to an embodiment of the present invention.
The current measurement system 10 includes a current sensor 205-a, a current sensor 205-b, a current sensor 205-c, a current sensor 205-d, and a cable 21-a, a cable 21-b, a cable 21-c, and a cable 21-d. It is composed of an information processing device (for example, an industrial personal computer) 30 and a display device 40.
The current sensor 205 is, for example, a known magnetic current sensor, and measures a current value (current amount) by detecting a magnetic field created around an electric wire by a current to be measured by a magnetic sensor and measuring the magnitude of the magnetic field. It is a thing. Of the wiring extending from the control panel 2 of the machine tool 1, the current sensor 205-a is attached to a cable (electric wire) connected to the spindle motor 101 in order to measure the current flowing through the spindle motor 101, and is attached to the current sensor 205-b. Is attached to a cable connected to the servomotor 102-a to measure the current flowing through the servomotor 102-a (Z-axis servomotor that drives the tool base 106), and the current sensor 205-c is the servomotor 102-. It is attached to a cable connected to the servo motor 102-b to measure the current flowing through b (X-axis servo motor that drives the tool base 106), and the current sensor 205-d is attached to the servo motor 102-c (tool base rotation). Servo motor) is attached to a cable connected to the servo motor 102-c to measure the current flowing through it.
The cables 21-a, cable 21-b, cable 21-c, and cable 21-d of the current sensor 205-a, the current sensor 205-b, the current sensor 205-c, and the current sensor 205-d are information processing devices. It is connected to 30 (may be a wireless connection or the like). Each cable 21 is connected to an I / O module (which includes an analog electronic circuit for noise reduction and signal amplification and an AD converter for converting analog data into digital data), which is not shown. The / O module may convert the analog signal input from the current sensor 205 into a digital signal and output the digital signal to the information processing apparatus 30 by wired or wireless communication.
The information processing device 30 includes a CPU or the like which is an arithmetic unit as a control unit / calculation unit, and has a predetermined storage device as a storage unit as a built-in or external HDD or the like. Further, the information processing apparatus 30 may include an electronic circuit as an analog circuit.
The display device 40 may include a display mechanism and an input mechanism, and may be supported by a predetermined stand or fixed to the machine tool 1 by a predetermined jig. Further, the display device 40 may have only a notification function like a simple lamp. The display device 40 is connected to the information processing device 30 by a predetermined cable 41 (may be a wireless connection or the like). The display device 40 is, for example, a liquid crystal display, a touch panel display, a tablet terminal, a smartphone, or the like.

FIG. 2 is a schematic view showing an example of a well-known "NC lathe" which is a machine tool 1.
A spindle motor 101 for driving the spindle 100 and a servomotor 102-a, a servomotor 102-b, and a servomotor 102-c for driving the tool base (tool changer) 106 are attached to the machine tool 1.
The work 103 (for example, a metal round bar) to be machined is fixed by a chuck 104 attached to the spindle 100, and rotates about the spindle 100 as an axis.
A plurality of types of tools 105-a and 105-b for machining a work (here, two tools a and b are used for convenience of explanation, but three or more tools may be used) are used as tool stands (tool replacement). Device) Attached to and fixed to 106. The servo motor 102-a (Z-axis servo motor), servo motor 102-b (X-axis servo motor), and servo motor 102-c (tool table rotation servo motor) that drive the tool base 106 are shown in the drawings. In 1, the movement in the left-right direction indicated by the Z-axis in the figure, the movement in the up-down direction indicated by the X-axis in the figure, and the rotation about the left-right direction (Z-axis) indicated by θ in the figure (tool stand). The tools 105-a and 105-b are exchanged by the rotation of 106.). Depending on the machine tool, the degree of freedom of movement by the servomotor 102 may be further increased, and a motor for that purpose may be added.
In FIG. 1, the tool base 106 and the tool 105-a are moved forward to the left side of the figure by the servo motor 102-a (Z-axis servo motor) according to the instructions of the NC program, and the work 103 (rotated around the spindle). The tool 105-a comes into contact with the tool 105-a to perform cutting and the like.
When changing from the tool 105-a to the tool 105-b, in FIG. 1, the tool base 106 and the tool 105-a move backward to the right side in the figure, and the servo motor 102-c (servo base rotation servo motor) is used. ) Rotates the tool base 106 to switch the positions of 105-a and 105-b, so that the tool is changed (note that "change" to a different type of tool and "replacement" of the tool are carried out. (To a new product) ”is explained as a different concept.) As a result, in FIG. 1, when the tool base 106 and the tool 105-b are moved forward by the servo motor 102-a (Z-axis servo motor) to the left side in the figure, the work 103 (rotates around the spindle). The tool 105-b comes into contact with the tool 105-b.
The tool 105 is selected according to the material of the work 103 and the type of machining. For example, in rough machining where it is required to take as much removal volume per unit machining time as possible, the contact volume between the work 103 and the tip of the tool 105 is the contact volume. A tool 105 having a tip shape that homogenizes the surface roughness is selected for surface finishing that directly affects the processing quality, and the work 103 is placed inside the rotation axis. In the inner diameter cutting for cutting from, the tool 105 for boring is selected.

FIG. 3 is a block diagram for explaining a signal flow of an NC lathe which is a machine tool 1 and its current measuring system 10.
In FIG. 3, first, the control signal output from the NC device 201 is input to the PLC 202, the inverter 203, the servo amplifier 204-a, the servo amplifier 204-b, and the servo amplifier 204-c.
The inverter 203 drives the spindle motor 101, and the servo amplifier 204-a, the servo amplifier 204-b, and the servo amplifier 204-c follow the instructions from the NC device 201, and the servo motor 102-a, the servo motor 102-b, and the servo motor, respectively. The motion (movement) of 102-c is controlled.
The current sensor 205-a measures the current flowing through the spindle motor 101, and the current sensor 205-b, the current sensor 205-c, and the current sensor 205-d are the servomotor 102-a, the servomotor 102-b, and the servomotor, respectively. The current flowing through 102-c is measured.
A program (NC program) for processing the work 103 into a desired shape is mounted on the NC device 201.
As the spindle motor 101 rotates, the work 103 fixed by the chuck 104 also rotates at the same time.
When the servo amplifier 204-a drives the servo motor 102-a according to the instruction from the NC device 201, the tool base 106 moves in the left-right direction shown by the Z axis in FIG. 2, and the tool 105 comes into contact with the work 103. , Cutting is done.
By driving the servomotor 102-b by the servo amplifier 204-b according to the instruction from the NC device 201, the tool table 106 moves in the vertical direction shown by the X axis in FIG.
By controlling the servomotor 102-c so that the servo amplifier 204-c rotates the tool base 106 according to the instruction from the NC device 201, the tool 105 in contact with the work 103 is replaced.

FIG. 4 shows the time history waveform 301 (solid line) of the current flowing through the spindle motor 101 during operation of the NC lathe, which is the machine tool 1, measured by the current sensor 205-a, and the current sensor 205-d. It is a time history waveform 302 (broken line) of the current flowing through the servomotor 102-c (servomotor for rotating the tool table) while the machine tool 1 is operating, which is measured by. The vertical axis is the current value, and the horizontal axis is the elapsed time. Here, the current sensor 205-a for measuring the current flowing through the spindle motor 101 as the first current sensor will be described as an example, but the servomotor 102-a (Z-axis servomotor) will be described as the first current sensor. It is also possible to apply the current sensor 205-b that measures the current flowing through the current sensor 205-b and the current sensor 205-c that measures the current flowing through the servo motor 102-b (X-axis servo motor), and duplicate explanations are omitted. (Note that also in the description of FIGS. 5 and 6 described later, the current sensor 205-b and the servomotor 102-b (X-axis servomotor) that measure the current flowing through the servomotor 102-a (Z-axis servomotor) are used. The description of applying the current sensor 205-c for measuring the flowing current is omitted because it is duplicated.)
When the tool used for cutting or the like is changed from the tool 105-a to the tool 105-b, or from the tool 105-b to the tool 105-a, the tool base 106 is rotated. Move. At this time, since a large current flows through the servomotor 102-c to rotate the tool base 106, a momentary peak appears in the time history waveform 302 of the current flowing through the servomotor 102-c. By synchronizing (overlapping) the time history waveform 302 including the instantaneous peak and the time history waveform 301 of the current flowing through the spindle motor 101, the spindle corresponding to the usage time of the tool 105-a and the tool 105-b The time history waveform of the current flowing through the motor 101 can be extracted (cut out).
The measured current value is stored in a storage device or the like of the information processing device 30, and even if the arithmetic device of the information processing device 30 connected to the storage device or the like performs synchronous processing with digital data, it is also possible. Synchronous processing may be performed as analog information in the analog circuit of the information processing apparatus 30 (an electronic circuit that handles continuously changing electric signals).
Specifically, as shown in FIG. 4, the tool 105-a is used from the start time of cutting or the like to the momentary peak that first appears in the time history waveform 302, and the tool table 106 is used for the first time. A momentary peak appears first when rotating, at which point the tool 105-a is changed to tool 105-b, and thereafter, until the next momentary peak appears in the time history waveform 302. Can be considered (estimated) that the tool 105-b is in use. However, FIG. 4 is merely a schematic graph for facilitation of understanding, from the start of cutting or the like until the tool 105-a hits the work 103, or from the tool 105-a. The state in which none of the tools 105 hits the work 103 when changing to the tool 105-b is ignored, and the current value does not necessarily take a constant (flat) value for each tool. is not it.
It should be noted that, at the time of cutting or the like, the time history waveform 302 has an instantaneous peak by associating it with the data of the order in which the plurality of tools are used, which are preset in a predetermined table or the like of the storage device of the information processing apparatus 30. Each time, it is possible to specify from the first tool to the second tool, specifically from what kind of tool to what kind of tool. Data on the order in which the above-mentioned plurality of tools are used is acquired from the information processing device 30, and the data is associated with the data shown in FIG. The name of the tool used may also be displayed.

Further, in FIG. 4, the machine tool 1 has been described on the premise of an “NC lathe” having a predetermined structure, but the machine tool 1 processes the work 103 while changing a plurality of types of tools 105 to process the work 103. As long as it is provided with a first motor that receives current load fluctuations and a second motor that controls the operation for changing multiple types of tools 105, its specific structure is not limited, and the first The current sensor (for example, current sensor 205-a, current sensor 205-b, current sensor 205-c) measures the current flowing through the first motor that receives the load fluctuation when machining the work 103, and the second The current sensor 205-d as a current sensor measures the current flowing through the second motor for controlling the operation for changing the tools 105 of multiple types, and synchronizes the time history waveform of the current flowing through each of these two motors. By doing so, the analysis process can be executed (the same applies to the description of FIGS. 5 and 6 described later).
For example, in the case of a machine tool 1 in which the tool 105 is stored in a box or the like with a door, the door is opened by a predetermined motor, and the door when the tool 105 is selected, gripped and attached by a predetermined arm. By measuring a large current (instantaneous peak) at the time of opening and closing of the door, it is possible to estimate the timing of change of a plurality of types of tools 105.

Further, not only the timing of replacement of the tool 105 is estimated, but also a large current flows through the servomotor 102-a and the servomotor 102-b when the tool base 106 is moved left and right and up and down. It is also possible to estimate the operating time, operating rate, etc. of the machine tool 1 based on the above.

In addition, it can also be used for failure prediction (abnormality detection). That is, the current sensor 205-a as the first current sensor measures the current flowing through the first motor that drives the work 103 side, and the current sensor 205-d as the second current sensor drives the tool 105 side. When the current flowing through the second motor is measured, the time history waveform of the current flowing through each of these two motors is synchronized, the analysis process is executed, and a waveform different from the normal (normal) waveform appears. Can perform failure prediction by regarding the machine machine 1 or the tool 105 as a sign of failure or failure.

5 (a) and 5 (b) show the load feature amount for each type of tool with respect to the number of times of machining (may be machining time, removed volume, etc.) (Note that the “load” here refers to the work. On the other hand, it refers to the magnitude of the repulsive force when a tool is applied. There are various calculation formulas and indexes, but in the following, the load is estimated by measuring the "magnitude of current". That is, when a relatively large load is applied (a deteriorated tool hits the work and a resistance force corresponding to it is generated), a relatively large current flows and a relatively small load is applied. When is applied (a tool that has not deteriorated so much hits the work and a resistance force is generated by that amount), a relatively small current flows, and when no load is applied (idle). , Estimated using the fact that almost no current flows.)
Here, the load feature amount means the average value of the current values of each block in FIG. Specifically, in FIG. 4, the magnitude of the current during the time when the tool 105-a was used is shown as a region (cutting section) of the block 1, and the average value of the magnitude of the current during that time is loaded. As the feature amount, it is plotted as a circle in FIG. 5 (a). Similarly, in FIG. 4, the magnitude of the current during the time when the tool 105-b was used is shown as a region (cutting section) of the block 2, and the average value of the magnitude of the current during that time zone is used as the load feature amount. As a triangle mark in FIG. 5 (b). The circles and triangles plotted in FIGS. 5 (a) and 5 (b) are based on the premise that the same workpiece is processed under the same conditions, for example, in the case of making 100 of the same product. It is a load feature amount calculated and processed by the arithmetic unit of the information processing apparatus 30, and is only shown in a graph for easy understanding, and graphing is not essential.
As the number of machining increases, the load feature amount 401 of the tool 105-a shown in FIG. 5A and the load feature amount 402 of the tool 105-b shown in FIG. 5B both tend to increase (measurement, etc.). It means that the load feature amount does not necessarily increase in proportion to the number of times of processing because there may be an error in.).
This is because when the surface of the tool is worn and deteriorated as the number of times of machining increases, that is, as the tool is used, the friction on the surface of the tool that hits the work increases, that is, the resistance force increases. This is because the load also increases.
The load feature amount of each tool calculated and processed by the arithmetic unit of the information processing device 30 in the threshold 403 and the threshold value 404 of the load feature amount of each tool preset in a predetermined table or the like of the storage device of the information processing device 30. (Even if it reaches once, measurement error measures may be taken such as when it reaches twice in a row just in case. By adding additional conditions such as when the preliminary threshold of about 90% is reached twice in a row. If it is determined that there may be one), it is estimated that the surface of the tool is worn and the deterioration is remarkable and it is time to replace the tool, and the arithmetic unit of the information processing apparatus 30 displays a predetermined alert for tool replacement. Notify the display screen 5 or the like of the device 40.
In the above, the non-negative function values (root mean squares) with the current value of each cutout section as an argument are compared relative to each number of times of machining, but the total value of the absolute values of the current values measured as non-negative function values is summed up. May be used.
Further, in FIGS. 5 (a) and 5 (b), the theoretical life curve (representing the progress of wear of the tool 105 in an ideal situation when there is no variation in the cutting process due to disturbance or the like) is shown. Then, based on the relationship between the plotted load features and the theoretical life curve (transition, tendency of inclination, etc.), the degree of progress of wear at the time of observation of the tool 105 is estimated by various known methods. Is possible. For example, if the theoretical life curve is approximately S-shaped, the timing of approaching the second curve is determined in advance as the tool replacement timing, and information is provided that the second curve is approached from the transition of the plotted load features. When it is determined by the processing device 30, a predetermined alert for tool change may be notified to the display screen 5 or the like of the display device 40.
Further, depending on the machining conditions and the like, the sensitivity of the current flowing through the spindle motor 101 is low as the first motor that receives the load fluctuation when machining the work 103 with respect to the predetermined tool 105 (degree of tool wear and current). There is a possibility that the progress of tool wear cannot be estimated efficiently and effectively. In that case, it can be estimated by the current flowing through the other servo motor 102. Therefore, it is a great merit that there are a plurality of candidates as the first current sensor (for example, current sensor 205-a, current sensor 205-b, current sensor 205-c).

FIG. 6 is a diagram showing an example of a display screen 5 displayed on the display device 40.
The display screen 5 shows a machined product name (for example, a product name: a camshaft of an automobile of company A) display 501, a tool change notification (alert) display 502, a tool load feature amount display 503, and a current measurement value (current measurement value). The time history waveform of the current and the current current value may also be displayed.) Display 504, tool name display 505, and tool replacement history (replacement date and time, etc.) as past history information. It is composed of 506 and the like. Of course, not all of these indications are mandatory.
It should be noted that only the tool change alert may be notified by blinking a predetermined separate lamp or the like without outputting to the display screen 5.
Further, the data output to the display device 40 or the like may be displayed and used on a predetermined display unit (liquid crystal display or the like) only by the information processing device 30 without being output to the display device 40 or the like. good.

Next, the current measurement method of the machine tool 1 using the machine tool current measurement system 10 according to the embodiment of the present invention will be described in detail with reference to the flow chart of FIG.
The basic flow flows to the first motor that receives the load fluctuation when the first current sensor (for example, current sensor 205-a, current sensor 205-b, current sensor 205-c) processes the work 103. The current is measured, and the current sensor 205-d as the second current sensor measures the current flowing through the second motor for controlling the operation for changing the tools 105 of multiple types, and for each of these two motors. The analysis process is executed by synchronizing the time history waveforms of the flowing current.
In the following, the load estimation of the tool is performed when the work 103 is machined while changing the tool 105-a and the tool 105-b, which are two types of tools used for cutting by the NC lathe which is the machine tool 1. By using this together, the wear state of each tool (when the wear state exceeds a certain limit, it is assumed to be a state included in the concept of "tool abnormality") is estimated, and the timing of tool replacement is estimated and notified. The case will be described.
Here, the current sensor 205-a for measuring the current flowing through the spindle motor 101 as the first current sensor will be described as an example, but the current flowing through the servo motor 102-a will be measured as the first current sensor. Similarly, it is possible to apply the current sensor 205-c that measures the current flowing through the current sensor 205-b and the servo motor 102-b.

First, the threshold value 403 and the threshold value 404 of the load feature amount for each tool 105-a and the tool 105-b are set in advance in a predetermined table or the like of the storage device of the information processing device 30 (step S1).

Next, when the machine tool 1 starts machining the work 103 using the tool 105, the current sensor 205-a measures the current flowing through the spindle motor 101, and the current sensor 205-d measures the servomotor 102-c. (Step S2).

Then, as shown in FIG. 4, the information processing apparatus 30 obtains the time history waveform 301 (solid line) of the current flowing through the spindle motor 101 and the time history waveform 302 (broken line) of the current flowing through the servomotor 102-c. , Perform synchronization processing (step S3).

In the arithmetic unit of the information processing apparatus 30, the tool 105-a is used from the start of cutting or the like to the instantaneous peak (peak signal) that first appears in the time history waveform 302, and the tool table 106 is used for the first time. A momentary peak appears first when the is rotated, at which point the tool 105-a is changed to the tool 105-b, and thereafter, the next momentary peak appears in the time history waveform 302. Up to this point, it is assumed that the tool 105-b is used (estimated), and in FIG. 4, the area of the block 1 in which the tool 105-a is used and the area of the block 2 in which the tool 105-b is used are used. The average value of the magnitude of the current in the region is calculated as the load feature amount (step S4). It should be noted that each time an instantaneous peak appears in the time history waveform 302 by associating it with data in the order in which a plurality of tools are used, which are preset in a predetermined table or the like of the storage device of the information processing apparatus 30. It is possible to specify from the first tool to the second tool, specifically from what kind of tool to what kind of tool.

Then, the calculation device of the information processing apparatus 30 determines whether or not the load feature amount of each tool has reached the thresholds 403 and 404 of the load feature amount of each tool set in step S1 above (step). S5) If there is a tool that is determined to have been reached, it is estimated that the surface of the tool is worn and the deterioration is remarkable, and it is time to replace the tool. A predetermined alert to the effect that replacement is necessary is notified to the display screen 5 or the like of the display device 40, for example, as shown in FIG. 6 (step S6).

By doing so, the current of the motor that drives the rotating spindle and the current of the motor that drives the tool switching table are measured and synchronously processed without going through the NC device of the machine tool 1, and the same type of workpiece is processed. In a situation where a plurality of 103s are machined, the non-negative function value of the current waveform cut out for each tool 105 is compared relative to each work and the transition is observed to estimate the wear state of each tool 105 with respect to the number of times the work 103 is machined. can do.
Conventionally, a machine tool maker can analyze data from a program running inside the machine, but when one factory uses multiple machine tools from different manufacturers, it is a general-purpose machine tool. It has been desired to determine the tool replacement timing and the like from the outside of No. 1 (there is a risk that if the internal electric circuit or the like is changed, it will be a modified product or the like and will not be covered by the manufacturer's warranty). For example, when machining one work while changing using three types of tools, one type of tool is used for a relatively long time, so it wears the fastest, but it is set by the machine tool manufacturer. In some cases, the number of rotations is used as a guide for batch replacement, and in some cases, the abnormal value is measured and judged based on the total value of the three types of tools. At that time, the remaining two types of tools are still usable. There was a waste of tool costs. Cost reduction and economic efficiency can be realized by using each tool up to the limit of the allowable range of use and then disposing of it or replacing it with a new one at each timing.

According to the above-described embodiment, it is possible to detect a tool abnormality of a tool used in a cutting process using a plurality of types of tools by an NC lathe which is a machine tool.
Although the NC lathe exemplified above has a single spindle, it can also be applied to a composite lathe having a plurality of spindles.

Further, by using at least one of the current sensors 205 and a predetermined voltage sensor in combination, the voltage is measured at the same time as the current, so that the above current can be obtained based on the power consumption of the spindle motor 101, the servo motor 102, or the like. The same thing as the embodiment used can be realized.

Next, the machine tool current measurement system according to the second embodiment of the present invention will be described in detail with reference to the drawings.
A machining center (vertical machining center) is assumed as a machine tool.
The description that overlaps with the current measurement system of the machine tool according to the first embodiment is omitted as appropriate, and the same device or the like may be designated by the same reference numeral.

FIG. 8 is a block diagram of the current measuring system 10 ′ of the machine tool 1 ′ according to the embodiment of the present invention.
The current measurement system 10' includes a current sensor 205'-a, a current sensor 205'-b, a current sensor 205'-c, a current sensor 205'-d, a current sensor 205'-e, a cable 21'-a, and a cable. It is composed of 21'-b, a cable 21'-c, a cable 21'-d, a cable 21'-e, an information processing device (for example, an industrial personal computer) 30, and a display device 40.
The current sensor 205'is, for example, a known magnetic current sensor, and measures the current value (current amount) by detecting the magnetic field created around the electric wire by the current to be measured by the magnetic sensor and measuring the magnitude of the magnetic field. It is something to do. Of the wiring extending from the control panel 2'of the machine tool 1', the current sensor 205'-a is attached to a cable (electric wire) connected to the spindle motor 101'to measure the current flowing through the spindle motor 101'. The current sensor 205'-b is attached to a cable connected to the servomotor 102'-a to measure the current flowing through the servomotor 102'-a (Z-axis servomotor of the spindle), and the current sensor 205'-c is attached. Is attached to a cable connected to the servomotor 102'-b to measure the current flowing through the servomotor 102'-b (X-axis servomotor that drives the stage 107'), and the current sensor 205'-d is a servo. It is attached to a cable connected to the servomotor 102'-c to measure the current flowing through the motor 102'-c (Y-axis servomotor that drives the stage 107'), and the current sensor 205'-e is the servomotor 102. It is attached to a cable connected to the servomotor 102'-d to measure the current flowing through the'-d (ATC servomotor that drives the ATC (Automatic Tool Changer) 108').
Cable 21'-a, cable 21'-b, cable of current sensor 205'-a, current sensor 205'-b, current sensor 205'-c, current sensor 205'-d, current sensor 205'-e, respectively. The 21'-c, the cable 21'-d, and the cable 21'-e are connected to the information processing apparatus 30 (may be a wireless connection or the like). Each cable 21'is connected to an I / O module (which includes an analog electronic circuit for noise reduction and signal amplification and an AD converter for converting analog data into digital data) (not shown). The I / O module may convert the analog signal input from the current sensor 205'to a digital signal and output the digital signal to the information processing apparatus 30 by wired or wireless communication.
The information processing device 30 includes a CPU or the like which is an arithmetic unit as a control unit / calculation unit, and has a predetermined storage device as a storage unit as a built-in or external HDD or the like. Further, the information processing apparatus 30 may include an electronic circuit as an analog circuit.
The display device 40 may include a display mechanism and an input mechanism, and may be supported by a predetermined stand or fixed to the machine tool 1'by a predetermined jig. Further, the display device 40 may have only a notification function like a simple lamp. The display device 40 is connected to the information processing device 30 by a predetermined cable 41 (may be a wireless connection or the like). The display device 40 is, for example, a liquid crystal display, a touch panel display, a tablet terminal, a smartphone, or the like.

FIG. 9 is a schematic view showing an example of a well-known vertical machining center (3-axis machining, table (stage) driven type), which is a machine tool 1'.
The machine tool 1 includes a spindle motor 101', a Z-axis servomotor 102'-a for driving the spindle 100', a servomotor 102'-b, a servomotor 102'-c for driving the stage 107', and an ATC108'. A driving servomotor 102'-d is attached.
The work 103'(for example, a cubic metal piece) to be machined is attached to and fixed to the stage 107'. The servo motor 102'-b (X-axis servo motor) and servo motor 102'-c (Y-axis servo motor) that drive the stage 107'are left and right shown by the X-axis in FIG. 9, respectively. It controls the movement in the direction and the movement in the front-back direction indicated by the Y-axis in the figure. Depending on the machine tool, the degree of freedom of movement by the servo motor 102'may be further increased, and a motor for that purpose may be added. For example, it is a 5-axis machining in which two axes of rotation and inclination are added.
The tool 105'(here 105'-a) for machining the work is attached to the spindle 100', rotates around the spindle 100', and drives the spindle 100'. (Z-axis servomotor) moves in the vertical direction indicated by the Z-axis in FIG. 9 in FIG.
Multiple types of tools for machining workpieces 105'-a, 105'-b, 105'-c (Here, a, b, and c are set to three for convenience of explanation, but four or more may be used. ) Is replaced by ATC108'. As an example, in FIG. 9, the ATC 108'is provided with tools 105'-b and 105'-c as change tools, and is used for ATC drive according to a tool change signal from the NC device 201'based on the NC program. The servomotor 102'-d operates, and the ATC 108' carries out a change between the tool 105'-a attached to the spindle 100'and the tool 105'-b or the tool 105'-c'(note that they are different). "Change" to a type of tool is described as a different concept from "replacement (to a new one)" of a tool.) The position where the ATC 108'shown in FIG. 9 is provided (mounted) on the machine tool 1'is arbitrary.
In FIG. 9, the spindle 100'is moved to the lower side in the figure by the servomotor 102'-a according to the instruction of the NC program, and the tool 105'-a (rotating around the spindle as the axis) is stage 107'. It abuts on the upper work 103'and performs cutting or the like.
The tool 105'is selected according to the material of the work 103'and the type of machining. For example, in rough machining where it is required to take as much removal volume per unit machining time as possible, the work 103'and the tip of the tool 105' A tool with a shape that increases the contact volume of the tool 105'is selected, and a tool 105'having a tip shape that homogenizes the surface roughness is selected for surface finishing that directly affects the processing quality, and the work 103 is selected. In the inner diameter cutting in which ′ is cut from the inside of the rotating shaft, the tool 105 ′ for boring is selected.

FIG. 10 is a block diagram for explaining a signal flow of a vertical machining center which is a machine tool 1'and its current measuring system 10'.
In FIG. 10, first, the control signals output from the NC device 201'are the PLC202', the inverter 203', the servo amplifier 204'-a, the servo amplifier 204'-b, the servo amplifier 204'-c, and the servo amplifier 204'-. It is input to d.
The inverter 203'drives the spindle motor 101', and the servo amplifier 204'-a, the servo amplifier 204'-b, the servo amplifier 204'-c and the servo amplifier 204'-d are servomotors according to the instructions from the NC device 201, respectively. It controls the motion (operation) of the 102'-a, the servomotor 102'-b, the servomotor 102'-c, and the servomotor 102'-d.
The current sensor 205'-a measures the current flowing through the spindle motor 101', and the current sensor 205'-b, the current sensor 205'-c, the current sensor 205'-d, and the current sensor 205'-e are servo motors 102, respectively. The currents flowing through the'-a, the servo motor 102'-b, the servo motor 102'-c, and the servo motor 102'-d are measured.
A program (NC program) for processing the work 103'into a desired shape is mounted on the NC device 201'.
The tool 105'attached by the rotation of the spindle motor 101'also rotates at the same time.
By driving the servomotor 102'-a by the servo amplifier 204'-a according to the instruction from the NC device 201', the spindle 100'move in the vertical direction shown by the Z axis in FIG. 9, and the tool 105'is a workpiece. It comes into contact with 103'and cutting is performed.
By driving the servomotor 102'-b by the servo amplifier 204'-b according to the instruction from the NC device 201', the stage 107'is in the left-right direction indicated by the X axis in FIG. 9, and from the NC device 201'. By driving the servomotor 102'-c by the servo amplifier 204'-c according to the instruction of, the stage 107'move in the front-rear direction shown by the Y-axis in FIG.
The servo amplifier 204 ′ −d drives the servomotor 102 ′ −d according to the instruction from the NC device 201 ′, so that the ATC 108 ′ implements the change of the tool 105 ′.

FIG. 11 shows the time history waveform 301'(solid line) of the current flowing through the spindle motor 101' while the vertical machining center, which is the machine tool 1', is operating, measured by the current sensor 205'-a. It is a time history waveform 302 ′ (broken line) of the current flowing through the servomotor 102 ′ −d while the machine tool 1 ′ is operating, which is measured by the current sensor 205 ′ −e. The vertical axis is the current value, and the horizontal axis is the elapsed time. Here, the current sensor 205'-a that measures the current flowing through the spindle motor 101'as the first current sensor will be described as an example, but the current flowing through the servo motor 102'-a as the first current sensor will be described. It is also possible to apply the current sensor 205'-b for measuring the current and the current sensor 205'-c for measuring the current flowing through the servo motor 102'-b, and duplicated description will be omitted (note that it will be described later). Also in the explanations of FIGS. 12 and 13, the description of applying the current sensor 205'-b and the current sensor 205'-c will be omitted because they are substantially duplicated.)
When the tool used for cutting or the like is changed from the tool 105'-a to the tool 105'-b, for example, the ATC 108'operates. At this time, since a large current flows through the servomotor 102'-d to operate the ATC108', a momentary peak ((short-term continuous)) occurs in the time history waveform 302'of the current flowing through the servomotor 102'-d. The same applies below, including the peak.))) Appears. By synchronizing (overlapping) the time history waveform 302'including this instantaneous peak with the time history waveform 301' of the current flowing through the spindle motor 101', the tool 105'-a and the tool 105'-b are used. It is possible to extract (cut out) the time history waveform of the current flowing through the spindle motor 101'according to the time.
The measured current value is stored in a storage device or the like of the information processing device 30, and even if the arithmetic device of the information processing device 30 connected to the storage device or the like performs synchronous processing with digital data, it is also possible. Synchronous processing may be performed as analog information in the analog circuit of the information processing apparatus 30 (an electronic circuit that handles continuously changing electric signals).
Specifically, as shown in FIG. 11, the tool 105'-a is used from the start time of cutting or the like to the momentary peak that first appears in the time history waveform 302', and the tool 105'-a is used for the first time. When Can be considered (estimated) to be in use (estimated) until the tool 105'-b appears. However, FIG. 11 is merely a schematic graph for facilitation of understanding, from the start of cutting or the like until the tool 105'-a hits the work 103', or the tool 105'. The state in which none of the tools 105'is hitting the work 103' when changing from −a to the tool 105 ′ −b is expressed by ignoring it, and the current value is not always constant (flat) for each tool. ) Is not taken.
In addition, at the time of cutting or the like, the time history waveform 302'is instantaneously obtained by associating with the data of the order in which the plurality of tools are used, which are preset in a predetermined table of the storage device of the information processing apparatus 30. Each time a peak appears, it is possible to specify from the first tool to the second tool, specifically from what kind of tool to what kind of tool. Data on the order in which the above-mentioned plurality of tools are used is acquired from the information processing device 30, and the data is associated with the data shown in FIG. The name of the tool used may also be displayed.

Further, in FIG. 11, the machine machine 1 ′ has been described on the premise of a “vertical machining center” having a predetermined structure, but the machine tool 1 ′ processes the work 103 ′ while changing a plurality of types of tools 105 ′. If a first motor that receives load fluctuations when machining the work 103'and a second motor that controls the operation for changing a plurality of types of tools 105' are provided, the specific structure thereof is provided. Is not limited, and when the first current sensor (for example, current sensor 205'-a, current sensor 205'-b, current sensor 205'-c, current sensor 205'-d) processes the work 103'. The current flowing through the first motor that is subject to load fluctuations is measured, and the current sensor 205'-e as the second current sensor becomes the second motor for controlling the operation for changing multiple types of tools 105'. The analysis process can be executed by measuring the flowing current and synchronizing the time history waveforms of the current flowing in each of these two motors (the same applies to the description of FIGS. 12 and 13 described later). ).

Further, not only estimating the replacement timing of the tool 105', but also when moving the spindle 100'up and down or moving the stage 107' left and right and back and forth, the servo motor 102'-a and the servo motor 102'- Since a large current flows through b and the servomotor 102'-c, it is possible to estimate the operating time, operating rate, etc. of the machine tool 1'based on the up / down, left / right, front / rear movements.

In addition, it can also be used for failure prediction (abnormality detection). That is, the current sensor 205'-a as the first current sensor measures the current flowing through the first motor that receives the load fluctuation when processing the work 103', and the current sensor 205'-a as the second current sensor is used. -E measures the current flowing through the second motor to control the operation for changing the tools 105'of multiple types, synchronizes the time history waveform of the current flowing through each of these two motors, and executes the analysis process. However, when a waveform different from the normal (normal) waveform appears, it is possible to carry out failure prediction by regarding the machine machine 1'or the tool 105' as a sign of failure or failure.

12 (a) and 12 (b) show the load feature amount for each type of tool with respect to the number of times of machining (may be machining time, removed volume, etc.) (Note that the “load” here refers to the work. On the other hand, it refers to the magnitude of the repulsive force when a tool is applied. There are various calculation formulas and indexes, but in the following, the load is estimated by measuring the "magnitude of current". That is, when a relatively large load is applied (a deteriorated tool hits the work and a resistance force corresponding to it is generated), a relatively large current flows and a relatively small load is applied. When is applied (a tool that has not deteriorated so much hits the work and a resistance force is generated by that amount), a relatively small current flows, and when no load is applied (idle). , Estimated using the fact that almost no current flows.)
Here, the load feature amount means the average value of the current values of each block in FIG. Specifically, in FIG. 11, the magnitude of the current during the time when the tool 105'-a is used is shown as a region (cutting section) of the block 1', and the average value of the magnitude of the current during that time zone is shown. Is plotted as a circle in FIG. 12 (a) with the load feature amount. Similarly, in FIG. 11, the magnitude of the current during the time when the tool 105'-b was used is shown as a region (cutting section) of the block 2', and the average value of the magnitude of the current during that time is loaded. As a feature amount, it is plotted as a triangular mark in FIG. 12 (b). The circles and triangles plotted in FIGS. 12 (a) and 12 (b) are based on the premise that the same workpiece is processed under the same conditions, for example, in the case of making 100 identical products. It is a load feature amount calculated and processed by the arithmetic unit of the information processing apparatus 30, and is merely shown in a graph for easy understanding, and graphing is not essential.
As the number of machining times increases, both the load feature amount 401'of the tool 105'-a shown in FIG. 12A and the load feature amount 402'of the tool 105'-b shown in FIG. 12B increase. The tendency (meaning that the load feature amount does not necessarily increase in proportion to the number of times of processing because there may be an error in measurement etc.) is shown.
This is because when the surface of the tool is worn and deteriorated as the number of times of machining increases, that is, as the tool is used, the friction on the surface of the tool that hits the work increases, that is, the resistance force increases. This is because the load also increases.
The load of each tool calculated and processed by the arithmetic unit of the information processing device 30 to the thresholds 403'and 404' of the load feature amount of each tool preset in a predetermined table or the like of the storage device of the information processing device 30. Measurement error measures may be taken such as when the feature amount is reached (even if it is reached once, but just in case it is reached twice in a row. Additional conditions are added such as when the preliminary threshold of about 90% is reached twice in a row. If it is determined that this is the case), it is estimated that the surface of the tool is worn and the deterioration is remarkable and it is time to replace the tool, and the arithmetic unit of the information processing apparatus 30 has a predetermined alert for tool replacement. Is notified to the display screen 5 and the like of the display device 40.
In the above, the non-negative function values (root mean squares) with the current value of each cutout section as an argument are compared relative to each number of times of machining, but the total value of the absolute values of the current values measured as non-negative function values is summed up. May be used.
Further, FIGS. 12 (a) and 12 (b) show the theoretical life curve (representing the progress of wear of the tool 105'in an ideal situation when there is no variation in the cutting process due to disturbance or the like). Then, based on the relationship between the plotted load features and the theoretical life curve (transition, tendency of inclination, etc.), the degree of progress of wear at the time of observation of the tool 105'is estimated by various known methods. It becomes possible to do. For example, if the theoretical life curve is approximately S-shaped, the timing of approaching the second curve is determined in advance as the tool replacement timing, and information is provided that the second curve is approached from the transition of the plotted load features. When it is determined by the processing device 30, a predetermined alert for tool change may be notified to the display screen 5 or the like of the display device 40.
Further, depending on the machining conditions and the like, the sensitivity of the predetermined tool 105'is low with respect to the current flowing through the spindle motor 101'as the first motor that receives the load fluctuation when machining the work 103' (tool wear). There is a possibility that the progress of tool wear cannot be estimated efficiently and effectively. In that case, it is estimated by the current flowing through the other servo motor 102'. Since it may be possible, there are a plurality of candidates as the first current sensor (for example, current sensor 205'-a, current sensor 205'-b, current sensor 205'-c, current sensor 205'-e). There are great benefits to doing.

FIG. 13 is a diagram showing an example of a display screen 5 displayed on the display device 40.
The display screen 5 shows a machined product name (for example, a product name: a camshaft of an automobile of company A) display 501, a tool change notification (alert) display 502, a tool load feature amount display 503, and a current measurement value (current measurement value). The time history waveform of the current and the current current value may also be displayed.) Display 504, tool name display 505, and tool replacement history (replacement date and time, etc.) as past history information. It is composed of 506 and the like. Of course, not all of these indications are mandatory.
It should be noted that only the tool change alert may be notified by blinking a predetermined separate lamp or the like without outputting to the display screen 5.
Further, the data output to the display device 40 or the like may be displayed and used on a predetermined display unit (liquid crystal display or the like) only by the information processing device 30 without being output to the display device 40 or the like. good.

Next, a current measuring method of the machine tool 1'using the machine tool current measuring system 10 according to the embodiment of the present invention will be described in detail with reference to the float chart of FIG.
The basic flow is when the first current sensor (for example, current sensor 205'-a, current sensor 205'-b, current sensor 205'-c, current sensor 205'-d) processes the work 103'. A second motor for measuring the current flowing through the first motor that is subject to load fluctuations, and for the current sensor 205'-e as the second current sensor to control the operation for changing multiple types of tools 105'. The current flowing through the motors is measured, the time history waveforms of the currents flowing through each of these two motors are synchronized, and the analysis process is executed.
In the following, when machining the work 103'while changing the tool 105'-a and the tool 105'-b, which are two types of tools used for cutting by a vertical machining center which is a machine tool 1'. By using this together with tool load estimation, the wear state of each tool (when the wear state exceeds a certain limit, it is assumed to be included in the concept of "tool abnormality") and the timing of tool replacement is estimated. A case of estimating and notifying will be described.
Here, the current sensor 205'-a for measuring the current flowing through the spindle motor 101'as the first current sensor will be described as an example, but the current flowing through the servo motor 102'-a as the first current sensor will be described. The current sensor 205'-b that measures the current flowing through the servo motor 102'-b, the current sensor 205'-c that measures the current flowing through the servo motor 102'-b, and the current sensor 205'-d that measures the current flowing through the servo motor 102'-c are applied. It is possible as well.

First, a threshold value 403'and a threshold value 404'of the load feature amount for each tool 105'-a and the tool 105'-b are set in advance in a predetermined table or the like of the storage device of the information processing device 30 (step S1').

Next, when the machine tool 1'starts machining the work 103'using the tool 105', the current sensor 205'-a measures the current flowing through the spindle motor 101', and the current sensor 205'-e Measures the current flowing through the servomotor 102'-d (step S2').

Then, as shown in FIG. 11, the information processing apparatus 30 has a time history waveform 301 ′ (solid line) of the current flowing through the spindle motor 101 ′ and a time history waveform 302 ′ (broken line) of the current flowing through the servo motor 102 ′ −d. ), And the synchronization process is performed (step S3').

In the arithmetic unit of the information processing apparatus 30, the tool 105'-a is used from the start time of cutting or the like to the instantaneous peak (peak signal) that first appears in the time history waveform 302', and the tool 105'-a is used for the first time. A momentary peak appears first when the'operates, at which point the tool 105'-a is changed to the tool 105'-b, and thereafter, the time history waveform 302'is followed by the next momentary peak. Until the peak appears, it is assumed that the tool 105'-b is used (estimated), and the area of the block 1'where the tool 105'-a was used and the tool 105'-b in FIG. 11 are The average value of the magnitude of the current in the region of the used block 2'is calculated as the load feature amount (step S4'). It should be noted that every time a momentary peak appears in the time history waveform 302'by associating it with data in the order in which a plurality of tools are used, which are preset in a predetermined table or the like of the storage device of the information processing apparatus 30. It is possible to specify from the first tool to the second tool, specifically from what kind of tool to what kind of tool.

Then, the calculation device of the information processing apparatus 30 determines whether or not the load feature amount of each tool has reached the thresholds 403'and 404' of the load feature amount of each tool set in step S1'. If there is a tool that is determined to have been reached (step S5'), it is estimated that the surface of the tool is worn and deterioration is significant, and it is time to replace the tool. A predetermined alert indicating that the state is severe and the tool needs to be replaced is notified to the display screen 5 or the like of the display device 40, for example, as shown in FIG. 13 (step S6').

By doing so, the current of the motor that drives the rotating spindle and the current of the motor that drives the ATC are measured and synchronized without passing through the vertical machining center of the machine tool 1', and the same type of workpiece is processed. In the situation where a plurality of 103's are machined, the non-negative function value of the current waveform cut out for each tool 105'is compared relative to each work 103', and the transition is observed for each tool 105' with respect to the number of times the work 103' is machined. It is possible to estimate the wear state of.
Conventionally, a machine tool maker can analyze data from a program running inside the machine, but when one factory uses multiple machine tools from different manufacturers, it is a general-purpose machine tool. It has been desired to determine the tool replacement timing, etc. from the outside (there is a risk that if the internal electric circuit or the like is changed, it will be a modified product or the like and will not be covered by the manufacturer's warranty). For example, when machining one work while changing using three types of tools, one type of tool is used for a relatively long time, so it wears the fastest, but it is set by the machine tool manufacturer. In some cases, the number of rotations is used as a guide for batch replacement, and in some cases, the abnormal value is measured and judged based on the total value of the three types of tools. At that time, the remaining two types of tools are still usable. There was a waste of tool costs. Cost reduction and economic efficiency can be realized by using each tool up to the limit of the allowable range of use and then disposing of it or replacing it with a new one at each timing.

According to the above embodiment, it is possible to detect a tool abnormality of a tool used in a cutting process using a plurality of types of tools by a vertical machining center which is a machine tool.

Further, by using at least one of the current sensors 205'and a predetermined voltage sensor in combination, the voltage can be measured at the same time as the current, and the above current can be measured based on the power consumption of the spindle motor 101', the servo motor 102', and the like. It is possible to realize the same thing as the embodiment using.

In addition, although not illustrated one by one, the present invention may be carried out with various modifications within a range not deviating from the gist thereof. For example, the present invention can be applied to a multifunction device in which a function such as a machining center is mounted on an NC lathe.

1 Machine tool (NC lathe)
1'Machine tool (vertical machining center)
2, 2'Control panel 21-a, 21-b, 21-c, 21-d, 21'-a, 21'-b, 21'-c, 21'-d, 21'-e, 41 Cable 30 Information processing device 40 Display device 101, 101'Main axis motor 102a, 102-b, 102-c, 102'-a, 102'-b, 102'-c, 102'-d Servo motor 103, 103'Work 104 chuck 105-a, 105-b, 105'-a, 105'-b, 105'-c Tool 106 Tool stand 107'Stage 108' ATC
201, 201'NC device 202, 202' PLC
203, 203'Inverter 204-a, 204-b, 204-c, 204'-a, 204'-b, 204'-c, 204'-d Servo amplifier 205-a, 205-b, 205-c, 205-d, 205'-a, 205'-b, 205'-c, 205'-d, 205'-e Current sensor 301, 301'Time history waveform of current flowing through spindle motor 302, 302' Servo motor Time history waveform of flowing current 401 Load feature amount of tool 105-a 401'Load feature amount of tool 105'-a 402 Load feature amount of tool 105-b 402'Load feature amount of tool 105'-b 403, 404, 403', 404' Load feature amount threshold 5 Display screen 501 Machined product name display 502 Tool change notification display 503 Tool load feature amount transition display 504 Current measurement value display 505 Tool change history display

Claims (3)

A machine tool current measurement system in which the first current sensor and the second current sensor are connected to an information processing device, respectively.
The machine tool for machining by rotationally driving a work around a spindle while changing a plurality of types of tools is the first for driving the member when changing the position of the member to which the tool is attached. A motor and a second motor for controlling the operation for changing the plurality of types of tools are provided.
The information processing apparatus has a time history of the current of the first motor measured by the first current sensor and the current of the second motor measured by the second current sensor. The process of superimposing the waveforms at the same elapsed time is performed, and the current of the first motor measured by the first current sensor in the analysis process is used for the operation for changing the plurality of types of tools. A tool abnormality is detected for each type of the tool by cutting out each signal that occurs at that time and comparing the non-negative function value with the current value of each cutting section as an argument for each number of times the work is machined. A current measurement system for machine tools featuring. The current measuring system for a machine tool according to claim 1, wherein the information processing apparatus outputs information to a predetermined apparatus in order to notify the information of the tool abnormality. The plurality of motors include a first motor for driving the member when changing the position of the member to which the tool is attached and a second motor for controlling the operation for changing the plurality of types of the tool. a machine tool of the current measurement method of the kind of the tool change Shinano processed by rotating the Lawah over click the spindle as axis,
The information processing device to which the first current sensor and the second current sensor are connected is the current of the first motor measured by the first current sensor and the current of the second current sensor. A step of performing a process of superimposing each time history waveform with the measured current of the second motor by matching the elapsed time.
For each signal generated when the information processing apparatus operates the current of the first motor measured by the first current sensor for the change of the plurality of types of tools in the analysis process. It is characterized by having a process of detecting a tool abnormality for each type of the tool by relatively comparing non-negative function values with the current value of each cutting section as an argument for each number of times the work is machined. How to measure the current of a machine tool.

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