JP3089126B2 - Tool abnormality detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting an abnormality of a machining tool in-process (during machining).

[0002]

2. Description of the Related Art In recent years, there has been an increasing interest in automation of machine tools aimed at improving productivity, and many automatic machine tools including NC machines have been put to practical use.

For the stable operation of such an automatic machine tool, it is necessary to put into practical use a device that detects a tool abnormality, thereby stopping the machine or generating an alarm. Many proposals have been made regarding abnormality detection of a cutting tool. In particular, recently, with the development of various detectors and signal processing techniques, interest in a method and an apparatus for detecting a tool abnormality in process has been increasing.

By the way, as a conventional tool abnormality detection,
Focusing on the fact that an abnormality occurs in the tool, the load of the machine tool drive system (for example, cutting resistance, spindle motor current, feed axis motor current) changes, and by measuring the amount of change in these loads, A method of detecting an abnormality has been adopted.

However, the amount of change in the measurement signal of these loads when a tool abnormality occurs is generally small, and furthermore, since it is an electrical signal, a factory having a poor electrical environment is susceptible to electrical noise, and the accuracy and reliability of abnormality determination are high. There was a problem in that. In particular, it is more difficult to detect relatively minor abnormalities such as chipping and chipping, and high-precision,
That is, a tool abnormality detection device having a high abnormality detection sensitivity and few erroneous determinations can hardly be found.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a tool abnormality detecting device which has high sensitivity and can be used in-process with less erroneous determination.

[0007]

According to the present invention, there is provided a tool abnormality detecting apparatus for detecting a rotational speed of a main shaft of a machine tool and transmitting the rotational speed as a main shaft rotational speed signal. Signal sampling means for sending a velocity signal as a discrete time-series signal capable of being processed in a subsequent stage, arithmetic processing means for obtaining a power component as a generalized displacement parameter of the discrete time-series signal, Threshold setting means for setting an abnormality determination level; and abnormality determination for determining whether or not a tool abnormality has occurred based on the calculation result of the arithmetic processing means and the abnormality determination level set by the threshold setting means. Means, and output means for outputting tool abnormality information based on the determination result of the abnormality determination means.

[0008]

With the above configuration, the tool abnormality detecting device of the present invention has the following operation. The rotational speed of the machine tool spindle being machined is detected in-process by the spindle rotational speed detecting means, the detected signal is converted into a discrete time series signal by the signal sampling means, and the discrete time series signal is calculated by the arithmetic processing means. The power component when this time-series signal is used as a generalized displacement parameter is obtained in-process,
It is determined by the abnormality determining means in-process whether or not the obtained power component exceeds the abnormality determination level set by the threshold value setting means. The tool abnormality information is output to the control device of the machine tool or the operator in-process.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram of a cutting machine as a target example of tool abnormality detection, FIG. 2 is a block diagram showing a basic configuration of a tool abnormality detection device according to an embodiment of the present invention, and FIG. FIG. 9 is a diagram illustrating a comparison result between the technology and the present invention.

In FIG. 1, a tool 1 is mounted on a spindle 2, and the spindle 2 is incorporated in a headstock 3 and rotated by a spindle motor 4. The headstock 3 is moved vertically by a motor 7 along a column on a column base 5. The column base 5 is mounted on a bed 8 so as to be movable in the left-right direction, and is moved by a motor 6. As a result, the tool 1 using the motors 4, 6, 7
To process a workpiece (not shown).

In FIG. 2, the tool abnormality detecting device includes a spindle rotational speed detecting section 9, a signal sampling section 10, an arithmetic processing section 11, a threshold value setting section 12, and an abnormality judging section 13.
And an output unit 14. Each of these parts 9 to
14 may be separate for each functional block, or a part or the whole may be processed by a microcomputer, a minicomputer, or the like, and may be appropriately modified.

Next, a series of operations of the tool abnormality detecting device will be described together with the functions of the units 9 to 14.

The spindle speed detector 9 detects the rotation speed of the spindle 2 and converts the signal into a signal that can be processed by the signal sampling unit 10 at the subsequent stage, for example, a voltage signal or a digital signal, and sends it out. The main shaft rotation speed detector 9 includes, for example, (1) an N-pulse / 1-rotation rotary encoder (not shown) installed so as to rotate at a rotation speed proportional to the rotation speed of the main shaft 2 and a well-known frequency / voltage. Any configuration using conventionally known devices and techniques, such as a combination with a conversion device, and (2) a combination of a well-known synchronization counter with a rotation pulse generator that outputs one pulse for each rotation of the spindle 2 can do.

The signal sampling section 10 processes the signal detected and converted by the main shaft rotation speed detecting section 9 into a discrete time series signal which can be easily handled by the arithmetic processing section 11 at the subsequent stage. Specifically, it is configured by a noise removal circuit, an amplifier circuit, an analog / digital converter, a digital / digital converter, or the like, for example, in accordance with the specifications of the spindle rotation speed detection unit 9, and transmitted from the spindle rotation speed detection unit 9. A continuous analog time series signal or a quasi-continuous digital time series signal is converted into a discrete time series signal.

The arithmetic processing unit 11 includes a signal sampling unit 1
A power component when a discrete time-series signal sent from 0 is used as a generalized displacement parameter of the spindle rotational speed signal, for example, a device or element having a mathematical operation processing function such as a microcomputer. And the like.

Here, an example of the arithmetic processing in the arithmetic processing unit 11 will be described. That is, the spindle rotation speed is treated as a generalized displacement parameter y (t), and the following (i) to (iv)
The power component of the spindle rotation speed is obtained by the procedure described in (1). t is time. (I) Calculation of moving average <y _i > _m :

(Equation 1) (Ii) Calculation of velocity component Δ <y _i > _m :

Δ <y _i > _m = <y _i > _m− <y _i−1 > _m = (1 / m) (y _i −y _im ) Equation (2) (iii) Acceleration component Δ ² Calculating <y _i > _m :

Δ ² <y _i > _m = <y _i > _m− <y _i−1 > _m = (1 / m) ｛(y _i −y _i−1 ) − (y _im −y _im−1 )｝ Equation (3) (iv) Calculation of power component <P _i > _m :

<P _i > _m = ｛Δ <y _i > _m ｝ × ｛Δ ² <y _i > _m ｝ = (1 / m ² ) (y _i −y _im ) (y _i −y _i−1 −y _im + y _im-1 ) Expression (4)

Here, the power is the amount of work per unit time, is obtained by differentiating the energy, and its dimension is ML.
² T ^-3 . M is the dimension of mass, L is the length, and T is the dimension of time. On the other hand, since the dimension of the quantity obtained by multiplying the speed component and the acceleration component of a certain signal is L ² T ^-3 , the physical quantity proportional to the power of the corresponding motion of the signal is obtained by (speed component) × (acceleration component). It turns out that it can be obtained. That is, a physical quantity proportional to the machine tool spindle rotation power is obtained by the above equation (4). Further, as can be seen from the equation (4), the i-th power component <P _i > of the discrete time-series signal y (t)
_m is y _i and the signal values y _im , y _i−1 , y
It can be obtained from _im and y _im−1 , and by setting the signal sampling interval to be equal to or longer than the time required for the calculation represented by the above equation (4), it is possible to perform in-process calculation processing.

Next, the threshold value setting unit 12 sets an abnormality judgment level which is a threshold value necessary for judging whether normal processing or a tool error has occurred with respect to the power component of the signal to be monitored. For example, a method of setting various voltage setting circuits, a digital switch, or the like may be considered, and a method of setting a plurality of abnormality determination levels corresponding to the degree of a generated tool abnormality is also possible. The specific value of the abnormality determination level can be determined based on the results obtained through measurement, analysis, and the like of actual load data by an actual machining test.

The abnormality judging section 13 compares the result of the arithmetic processing in the arithmetic processing section 11 with the set value of the abnormality judgment level in the threshold value setting section 12 to judge whether or not a tool abnormality has occurred.
For example, if the power component exceeds the abnormality determination level, an abnormality has occurred. The abnormality determination unit 13 can be realized by various types of conventionally known electric circuits in consideration of the specifications of signals transmitted from the arithmetic processing unit 11 and the threshold setting unit 12, respectively.

The output unit 14 receives the determination result of normal processing or the occurrence of a tool abnormality by the abnormality determination unit 13 and outputs the determination result to the control device on the machine tool side or the operator side. It can be constituted by a relay circuit, an electric circuit, an alarm device and the like.

In the description of the above embodiment with reference to FIG. 2, each of the functional units 9 to 14 has been described as being separate for each block, but a part or all of them are processed by a microcomputer or a minicomputer. It is possible to make appropriate modifications without departing from the spirit of the present invention. In addition, the method of detecting the rotation speed of the machine tool spindle using the rotation of the spindle itself has been described, but other rotating bodies that rotate accurately in proportion to the spindle rotation, or move in proportion to the spindle rotation. Of course, it is also possible to detect the spindle rotation speed via another moving body or the like.

FIG. 3 shows an example of a tool abnormality detection result in an actual machining test by comparing the prior art with the present invention. FIG. 3
Reference numeral 15 in the middle indicates the current flowing through the armature of the spindle motor in the prior art, and is a monitoring target signal in a conventional tool abnormality detection device that monitors a load on a general drive system. is there. On the other hand, reference numeral 16 relates to the present invention, and shows a result of obtaining a power component when a rotational speed signal of a machine tool spindle is used as a generalized displacement parameter, and a signal transmitted from the arithmetic processing unit 11 in FIG. It corresponds to.

As can be seen from FIG. 3, in this example, when a tool abnormality occurs, the conventional spindle motor current signal 15 has about +4
Although a level change of about 0% occurs, a level change of about + 760% occurs in the power component signal 16 of the present invention.
5, which is about 3.2 seconds earlier than the abnormality detection time 15A.
That is, as compared with the conventional tool abnormality detection device that monitors the load current applied to the drive system, the magnitude of the power component when the spindle rotation speed is a generalized displacement parameter according to the present invention is monitored to determine whether a tool abnormality has occurred. Is high in detection sensitivity, and earlier detection is possible. Further, since the mechanical movement of the rotation of the main shaft is used as a monitoring target, it is hardly affected by electric noise and erroneous determination is small.

In the example shown in FIG. 3, a large level change occurs in the power component signal 16 at the time of changing the processing conditions, such as at the start of high-speed processing, but the machining conditions not shown in FIG. By installing a functional device, such as a relay circuit, for recognizing a change in processing conditions under such normal processing conditions, it is possible to recognize a change in processing conditions, and this processing condition change time 17 is excluded from abnormal monitoring targets. can do. Therefore, the above level change does not become a practical obstacle.

[0025]

The tool abnormality detecting device of the present invention has the following effects. (1) Continuous monitoring of the magnitude of the power component when the rotational speed of the machine tool spindle is used as a generalized displacement parameter, resulting in the occurrence of tool abnormalities in-process earlier with higher sensitivity than before. Can be detected. (2) Since the mechanical motion of the rotation speed of the machine tool spindle is used as a monitoring target, erroneous determinations due to the influence of electrical noise are small. (3) Since not only the acceleration component but also the speed component is considered as the power component, the power component is not easily affected by an instantaneous change in the processing state that does not involve a large change in speed, for example, a change in the processing state due to entanglement of cuttings or the like. , There are few erroneous determinations.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a cutting machine shown as a target example of tool abnormality detection.

FIG. 2 is a block diagram showing an embodiment of a tool abnormality detection device according to the present invention.

FIG. 3 is a diagram showing a comparison result between a conventional technique and the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tool 2 Spindle 9 Spindle rotation speed detection unit 10 Signal sampling unit 11 Operation processing unit 12 Threshold setting unit 13 Abnormality judgment unit 14 Output unit 16 Power component aging signal

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshihiko Higashiguchi 1-1-1, Wadazakicho, Hyogo-ku, Kobe-shi, Hyogo Mitsubishi Heavy Industries, Ltd. Kobe Shipyard (72) Inventor Fumihide Takeda Minami-ku, Hiroshima-shi, Hiroshima 2-14-23 Ujina Miyuki Takeda Engineering Consultant Co., Ltd. (56) References JP-A-1-164537 (JP, A) JP-A-61-159353 (JP, A) JP-A-1-277299 ( JP, A) JP-A-57-54053 (JP, A) JP-A-5-285793 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23Q 17/09

Claims (1)

(57) [Claims] 1. A main shaft rotation speed detecting means for detecting a rotation speed of a main shaft of a machine tool and transmitting the detected rotation speed as a main shaft rotation speed signal.
Signal sampling means for transmitting the spindle rotation speed signal as a discrete time-series signal capable of being processed at a subsequent stage, arithmetic processing means for obtaining a power component as a generalized displacement parameter of the discrete time-series signal, Threshold setting means for setting an abnormality determination level based on a power component;
Abnormality determining means for determining whether or not a tool abnormality has occurred based on the result of the calculation by the processing means and the abnormality determination level set by the threshold value setting means; Output means for outputting tool abnormality information.