JP3814894B2 - Tool abnormality detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a tool abnormality detection device for detecting tool breakage or the like of a machine tool.
[0002]
[Prior art]
  Conventionally, a tool provided with load detecting means for detecting a motor load of a main spindle or a feed axis of a machine tool, and determination means for determining whether there is an abnormality in the tool of the machine tool by comparing the detected machining addition with an evaluation reference value There is an anomaly detection device, for example, one described in JP-A-7-132440.
[0003]
  In the technique disclosed in Japanese Patent Laid-Open No. 7-132440, motor load reference data and variance are obtained from motor load sampling data at the time of trial cutting, and a threshold corresponding to variation in sampling data is obtained using this variance. Set, compare the reference data with the measured data of the motor load at regular intervals, and monitor whether the difference between the two data exceeds the threshold, for example, to determine whether there is a tool abnormality .
[0004]
[Problems to be solved by the invention]
  However, in the conventional technique, for example, when a tool diameter such as a drill or a tap is small and the difference between the motor load during actual operation and the motor load during idle operation is small, the processing is normally performed. Nevertheless, it was sometimes determined that the tool was abnormal. If such a misjudgment occurs, unnecessary work such as stopping the machine tool and replacing the tool is executed, which causes problems such as a reduction in efficiency and waste of expenses due to replacement of a normal tool. It was.
[0005]
  The present invention has been made to solve the above-described problems, and an object thereof is to prevent such erroneous determination in a tool abnormality detection device.
[0006]
[Means for Solving the Problems]
  As a means for solving the above-mentioned problem, a tool abnormality detection device according to claim 1 is a load detection means for detecting a motor load of a main spindle or a feed shaft of a machine tool, the detected motor load and an evaluation reference value. In the tool abnormality detection device comprising a determination means for determining the presence or absence of abnormality of the tool of the machine tool by comparison of the operation state input for performing an input indicating whether the machine tool is in the idle operation or the actual operation Means,A reference value input means for inputting the evaluation reference value, and a no-load variation range in which the evaluation reference value input via the reference value input means is a variation range of the motor load during idle operation. Whether or not the evaluation reference value is appropriate is determined based on whether or not the motor load variation range during operation is within the load variation range.A comparison means;The no-load variation range, the load variation range, and the evaluation reference value are displayed so as to be able to distinguish each other's magnitude relationship, and displayed according to the result of the determination by the comparison unitAnd a result display means.
[0007]
  The idle operation in the present invention means, for example, that the machine tool is operated with the tool removed, or the machine tool is operated without placing the workpiece on the work table. If necessary, the tool and the workpiece do not interfere with each other. It says driving in a state. The actual operation is an operation for actually machining a workpiece with a tool mounted on the spindle, for example, and the actual operation includes trial machining for data collection.
[0008]
  In this tool abnormality detection device, the load detection means outputs, for example, a load current value, a voltage value or a power value of a spindle motor of a machine tool, or an output of a load cell that outputs a signal corresponding to a force applied to the tool. The motor load of the machine tool is detected by, for example. The load detection means may detect either the main shaft motor load or the feed shaft motor load, or may detect both.
[0009]
  As is apparent from the difference between the above-described idle operation and actual operation, the motor load is smaller during idle operation than during actual operation.
  Therefore, the evaluation reference value is set to be between the no-load reference value calculated based on the motor load during idle operation and the load reference value calculated based on the motor load during actual operation. For example, it is possible to determine whether there is an abnormality in the tool of the machine tool by comparing the motor load detected by the load detecting means with the evaluation reference value.
  More specifically, if the detected motor load is smaller than the evaluation reference value, it can be said that the operation is idle. For example, the tool is not hitting the work due to tool breakage or the like, and the detected motor load is the evaluation reference. If the value is larger than the value, it can be said that the actual operation is performed, and it can be said that the tool normally hits the work and there is no abnormality in the tool.
[0010]
  However, since the motor load varies within a certain range, the present invention adopts the no-load variation range, which is the variation range of the motor load during idle operation, as the above-mentioned no-load reference value. As shown, a load variation range that is a motor load variation range during actual operation is employed.
  In the present invention, an input indicating whether the machine tool is idling or actual operation is made by the operation state input means. The operating state input means may be, for example, a switch whose position can be switched by pushing or tilting.
  Examples of the reference value input means include a numeric keypad panel and a dial.
[0011]
  Comparison meansThe evaluation reference value input via the reference value input means is the no-load variation range. Whether or not the evaluation reference value is appropriate is determined based on whether or not it is within the load variation range. The comparison means may be a circuit that compares the magnitudes of a plurality of input voltages and outputs a signal corresponding to the comparison, or allows the CPU to perform this function.
  Result display meansThe no-load variation range, the load variation range, and the evaluation reference value are displayed so that the mutual magnitude relationship can be identified, and the display according to the result of the determination by the comparison means, for example, the evaluation input via the reference value input means Displays whether the reference value is appropriate.
  As a result display means, the no-load variation range, the load variation range, and the evaluation reference value can be displayed so that the magnitude relationship between each other can be identified. For example, the evaluation reference value is appropriate, for example, "Evaluation reference value is too large" What is necessary is just to use the display apparatus which can display whether it is.
[0012]
  For example, the operator can input the evaluation reference value by operating the reference value input means while observing the display by the display means. For example, the operator can input an appropriate evaluation reference value by two to three trials.it can.
[0013]
  Judgment means was finally decided in this wayUsing the evaluation standard valueThis and the detected motor loadWithJudges the presence or absence of tool tool abnormalities by comparisonHowever, because the evaluation standard value is set with reference to the no-load variation range and the load variation range,Even when the difference between the motor load during actual operation and the motor load during idle operation is small, there is no risk of erroneous determination, and accurate determination can always be performed.
  Therefore, an erroneous determination of tool abnormality may cause unnecessary work such as stopping the machine tool and replacing the tool, resulting in a decrease in efficiency and waste of expenses due to replacement of a normal tool. Absent.
[0014]
  Note that the determination means may be a circuit that compares the magnitudes of a plurality of input voltages and outputs a signal corresponding thereto, or can cause the CPU to perform this function. This is the same as the comparison meansIt is.
[0015]
[0016]
[0017]
  Claim 2The tool abnormality detection device described isClaim 1In the tool abnormality detection device described above,Load variation rangeIs calculated based on the motor load in a predetermined number of trial machining.
[0018]
  Load variation rangeIs calculated on the basis of the motor load in a predetermined number of trial machining, so that the evaluation reference value can be made more accurate if trial machining is performed prior to machining of a workpiece as a product. Note that the number of trial processings may be set as appropriate by, for example, experiments.
[0019]
  Claim 3The tool abnormality detection device described isClaim 1 or 2In the tool abnormality detection device described above,No-load variation rangeandLoad variation rangeIs a sampling value of a predetermined period or a predetermined number of times.Combination of mean and varianceIt is described by.
[0020]
  By describing the no-load variation range and the load variation range using a combination of average and variance, for example, the sum and difference of the average and variance, the possibility of misjudgment is further reduced and more precise judgment is made. Can be executed.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
  Next, embodiments of the present invention will be described in detail by way of examples of the present invention.
[0022]
【Example】
  First, with reference to FIG. 1 and FIG. 2, the mechanical structure of the machine tool 10 of a present Example is demonstrated. As shown in FIG. 1, the machine tool 10 includes a table 14 for placing a workpiece (not shown) inside a splash guard 12 for preventing the scattering of cutting waste, for example, tool exchange such as a drill or a tap. An ATC magazine 16, a machine tool main body (hereinafter also simply referred to as a main body) 20, and the like are disposed. Further, the splash guard 12 is provided with an operation panel 22, a workpiece exchange port 24 for workpiece entry / exit and maintenance, an inspection hatch 26 mainly for maintenance, and the like. The operation panel 22 is provided with a state switch 23 as an operation state input unit, a liquid crystal display 25 as a result display unit, and a numeric keypad 27 as a reference value input unit.
[0023]
  As shown in FIG. 2, the main body 20 has a main shaft 28 for holding a tool such as a drill or a tap, a main shaft motor 30 for rotationally driving the main shaft 28, and a large number of steel balls, and is fixed to the main shaft side. A ball screw mechanism 36 comprising a nut portion 32 and a ball screw 34 inserted in the nut portion 32, a Z-axis motor 38 for rotationally driving the ball screw 34, a guide rail 40 arranged in parallel with the ball screw 34, a guide rail The slide 42 etc. which connect 40 and the main shaft side are provided. The Z-axis motor 38 corresponds to a drive motor for the feed shaft.
[0024]
  In the main body 20, the ball screw mechanism 36 and the Z-axis motor 38 constitute a Z-axis feed mechanism for feeding in the Z-axis direction. By rotating the ball screw 34 by the Z-axis motor 38, the Z-axis direction of the main shaft 28. Is moved. Further, the table 14 shown in FIG. 1 can be moved in the X-axis and Y-axis directions, and the relative positions of the workpiece and the tool in the X-, Y-, and Z-axis directions are changed along with the movement of the main shaft 28 in the Z-axis direction. Can be made.
[0025]
  The machine tool 10 includes a control system having the configuration shown in FIG. 3 in order to control the rotational speed of the main shaft 28 and the position in the Z-axis direction. As shown in FIG. 3, this control system is the main axis control system 50 for controlling the rotation of the main axis 28, the Z-axis control system 60 for controlling the Z-axis position of the main axis 28, and the center of this control system. The microcomputer unit 70, the operation panel 22, and an X-axis control system (not shown) for controlling the X-axis position of the table 14 and a Y-axis control system (not shown) for controlling the Y-axis position of the table 14 are configured. Has been.
[0026]
  The spindle control system 50 includes a spindle motor 30, a spindle servo amplifier 52 for supplying power to the spindle motor 30, and an axis control circuit 54 for controlling the power supplied to the spindle servo amplifier 52. The axis control circuit 54 is a microcomputer. The operation of the spindle servo amplifier 52 is controlled in accordance with an instruction from the CPU 72 of the unit 70. The Z-axis control system 60 includes a Z-axis motor 38, a Z-axis servo amplifier 62 for supplying power to the Z-axis motor 38, and an axis control circuit 64 for controlling the power supplied to the Z-axis servo amplifier 62. The control circuit 64 is configured to control the operation of the Z-axis servo amplifier 62 in accordance with an instruction from the CPU 72 of the microcomputer unit 70. Further, the X-axis control system and the Y-axis control system which are not shown in the figure have substantially the same configuration as the main shaft control system 50 and the Z-axis control system 60.
[0027]
  The microcomputer section 70 includes a ROM that stores a control program and the like, a one-chip CPU 72 that incorporates an input / output port and the like, and a RAM 74 that serves as a work area for the CPU 72, and is configured as a known microcomputer. The microcomputer unit 70 (strictly, the CPU 72) controls the spindle control system 50, the Z-axis control system 60, and the like according to a control program, and performs predetermined machining on the workpiece. Further, the microcomputer unit 70 is connected to the operation panel 22, and the microcomputer unit 70 performs various operations such as an operation state signal output when the state switch 23 of the operation panel 22 is pressed and a numerical value input signal from the numeric keypad panel 27. Can be acquired, or a signal can be sent to the operation panel 22 to control the display of images and characters on the liquid crystal display 25 of the operation panel 22 and to control the blinking of the LED lamps.
[0028]
  Further, the CPU 72 can acquire current value data corresponding to the current (motor current) supplied to the spindle motor 30 by the spindle servo amplifier 52 via the axis control circuit 54. That is, the CPU 72 can know the motor current in real time.
[0029]
  Further, the CPU 72 has a built-in counter that increments the count value at a constant cycle, for example, every 1/1000 second. By using the counter, the elapsed time such as a required time from the start to the end of a certain process is obtained. Time can also be measured.
[0030]
  The CPU 72 functions as a load detection unit, a determination unit, and a comparison unit, details of which will be described later. Next, a tool abnormality detection procedure in the machine tool 10 will be described along the processing of the CPU 72 of the microcomputer unit 70.
[0031]
  As shown in FIG. 4, when the machine tool 10 is started, the CPU 72 starts a main process. For example, the operator operates the numeric keypad 27 to read a value input as the threshold value L, and sets this threshold value. The value L is stored in, for example, the RAM 74 (Step 101, hereinafter, Step is abbreviated as S).
[0032]
  Next, the CPU 72 determines whether or not the process for determining the trial data is necessary based on whether or not the operation state signal is input from the state switch 23 (S102). If the determination is affirmative, the CPU 72 proceeds to the process of S103. In S103, the CPU 72 confirms that no tool is mounted on the spindle 28 based on information from the ATC magazine 16, for example, and then performs test-free load machining (does not perform machining such as cutting on the workpiece). Then, current value data sent from the shaft control circuit 54 every 2/1000 seconds, for example, for a predetermined measurement interval (see FIG. 7B) of the motor current of the spindle motor 30 at that time is acquired and the current value is obtained. The operation of storing (sampling value), calculating the average of the sampling values as the average value Ino, and storing it in the RAM 74, for example, is repeated a plurality of times (in this embodiment, five times), and the average value of the plurality of average values Ino The average value X0 of the motor current is calculated, and the standard deviation σ0 of the average value X0 is obtained, and the average value X0 and the standard deviation σ0 are stored in a predetermined area of the RAM 74.
[0033]
  Next, the CPU 72 instructs the ATC magazine 16, for example, and puts a tool such as a drill on the spindle 28.Let me wear itFrom the axis control circuit 54, for example, 2/1000 for a predetermined measurement section (see FIG. 7A) of the motor current of the spindle motor 30 at that time is performed by trial cutting (working such as cutting on the workpiece). The current value data sent every second is acquired, the current value (sampling value) is stored, the average of the sampling values is calculated as the average value In, and stored in, for example, the RAM 74 a plurality of times (this embodiment) In the example, it is repeated 5 times), and the average value X of the motor current is calculated as the average value of the average value In of the plurality of times, and the standard deviation σ of the average value X is obtained, and the average value X and the standard deviation σ are stored in the RAM 74 Store in a predetermined area. As shown in FIG. 7, since the average value In of the motor current in the cutting process (trial cutting process and actual cutting process) is larger than the average value In0 of the motor current at the time of the test-free load machining, the average value X is It becomes larger than the above-mentioned average value X0.
[0034]
  Next, the CPU 72 executes a comparison determination process shown in detail in FIG. 5 (S105). As shown in FIG. 5, when the comparison determination process is started, the CPU 72 causes the RAM 74 to store the threshold value L, the average value X0 of the motor current during trial load machining, the standard deviation σ0, and the average motor current during trial cutting. The value X and the standard deviation σ are read (S201).
[0035]
  Next, the CPU 72 varies the motor current during trial no-load machining (X0 ± 3σ0 in this embodiment, hereinafter referred to as “no-load variation”), and the motor current during trial cutting (X ± 3σ in this embodiment). (Hereinafter referred to as variation at the time of load) and the threshold value L are compared, and processing for displaying the result is performed.
[0036]
  Specifically, the CPU 72 first determines whether the upper limit (X0 + 3σ0) of the no-load variation is less than the lower limit (X-3σ) of the load variation (S202). If the upper limit (X0 + 3σ0) of the no-load variation is greater than or equal to the lower limit (X-3σ) of the load variation, for example, as shown in FIG. 6A, the no-load variation and the load variation overlap. In other words, it is impossible to accurately determine whether there is no tool breakage or no load machining, so it is impossible to accurately determine whether the tool is broken. Therefore, if a negative determination is made in S202, the CPU 72 instructs the operation panel 22 that the no-load variation and the load variation overlap on the liquid crystal display 25 as shown in FIG. And an image indicating the possibility of erroneous detection are displayed (S203).
[0037]
  If the determination is affirmative in S202, the CPU 72 proceeds to S204, and determines whether the upper limit (X0 + 3σ0) of the no-load variation is less than the threshold value L. If the upper limit (X0 + 3σ0) of the no-load variation is greater than or equal to the threshold value L, for example, as shown in FIG. 6B, the threshold value L is within the no-load variation range. Become. Therefore, if a negative determination is made in S204, the CPU 72 instructs the operation panel 22 to indicate on the liquid crystal display 25 that the threshold value L is within the range of no-load variation as shown in FIG. A message indicating that the setting of the image to be displayed and the threshold value L is too small is displayed (S205).
[0038]
  On the other hand, if an affirmative determination is made in S204, the CPU 72 proceeds to S206 and determines whether or not the lower limit (X-3σ) of the load variation exceeds the threshold value L. If the lower limit (X-3σ) of the load variation is less than or equal to the threshold value L, for example, the threshold value L is within the load variation range as shown in FIG. . Therefore, if a negative determination is made in S206, the CPU 72 instructs the operation panel 22 to indicate on the liquid crystal display 25 that the threshold value L is within the range of variation during loading as shown in FIG. A message indicating that the setting of the image and the threshold value L is too large is displayed (S207).
[0039]
  If the determination in S206 is affirmative, the threshold value L is between the no-load variation and the load variation, so the CPU 72 instructs the operation panel 22 to display on the liquid crystal display 25 as shown in FIG. An image indicating that the threshold value L is between the no-load variation and the load variation and a message indicating that the threshold value L is appropriately set are displayed (S208).
[0040]
  As shown in FIG. 4, when the comparison determination process ends and the process returns to the main process, the CPU 72 determines the threshold L based on the result of the comparison determination process.Necessity of resettingIs determined (S106). Specifically, when the comparison determination process ends in S205 (when the threshold value L is too small) or ends in S207 (when the threshold value L is too large), the threshold value L is reset. Is determined to be necessary (S106: YES), the process proceeds to S107, and when the comparison determination process ends in S208, it is determined that the resetting of the threshold value L is unnecessary (S106: NO), and the process proceeds to S108. Note that when the comparison determination process is ended in S203 (when the no-load variation and the load variation overlap), the CPU 72 cannot, for example, deal with the change in the threshold L setting. As error processing, the operator waits for an instruction to be input and performs processing according to the instruction.
[0041]
  In S107, for example, the CPU 72 waits for the operator to operate the numeric keypad 27 of the operation panel 22 to input a new threshold value L, and if it is input, stores it in the RAM 74 as the threshold value L. The above-described S105 (that is, the comparison determination process) is executed. Therefore, an appropriate threshold value L can be set by repeating S105 to S107. Note that the threshold value L in S107 is set by the CPU 72 selecting an appropriate value between the no-load variation and the load variation without using an external input, and setting this as a new threshold value L. As an automatic configurationGood.
[0042]
  In S108, the CPU 72 executes a process associated with the end of the trial data determination. After executing the process of S108 or when determining that the process for determining the trial data is unnecessary (S102: NO), the CPU 72 proceeds to the process of S109 and processes the workpiece according to a preset machining program. Perform processing for cutting.
[0043]
  Then, during this actual cutting, the motor current of the spindle motor 30 in the measurement section is sampled, and the average value I is obtained (S110, see FIG. 7A). Subsequently, the CPU 72 compares the average value I of the motor current with the threshold value L, and if the average value I is not less than the threshold value L (S111: NO), the tool corresponds to, for example, cutting. Since it can be determined that there is a load, that is, the tool is not broken, the process returns to S109 to execute the next actual cutting.
[0044]
  If the average value I is below the threshold value L (S111: YES), it can be determined that the tool has no load corresponding to, for example, cutting, that is, the tool is broken. Output a signal. When this abnormality signal is present, the operation panel 22 issues an alarm by, for example, displaying an abnormality on the liquid crystal display 25, sounding a buzzer, or lighting an alarm lamp. With such an alarm, for example, the operator can know that there is an abnormality such as a broken tool, and can perform appropriate processing such as stopping the machine tool 10 and replacing the tool.
[0045]
  As described above, in the machine tool 10 of the present embodiment, in the operation for setting the threshold value L, the magnitude relationship between the threshold value L and the no-load variation and the load variation is the liquid crystal display. For example, the operator can input an optimum value while watching the display on the liquid crystal display 25 and set it as the threshold value L.
[0046]
  Since the presence or absence of tool breakage is determined by comparing the threshold value L set in this way with the average value I of the motor current during actual cutting, the motor load during actual cutting and trial load machining Even when the difference from the motor load is small, there is no risk of erroneous determination, and accurate determination can always be performed. Therefore, there is no risk of performing unnecessary work such as stopping the machine tool and replacing the tool, for example, due to erroneous determination of tool abnormality, resulting in reduced efficiency and waste of expenses due to replacing a normal tool. It does not occur.
[0047]
  As mentioned above, although embodiment of this invention was described according to the Example, this invention is not limited to such an Example, and it cannot be overemphasized that it can implement variously in the range which does not deviate from the summary of this invention. For example, in the embodiment, the threshold value L is set using the non-load variation (X0 ± 3σ0) and the load variation (X ± 3σ). The standard deviation (X0 ± σ0, X ± σ) may be used, or only the average value (X0, X) at no load and load, or only the standard deviation (σ0, σ) at no load and load Good.
[0048]
  In the embodiment, the average value of the motor current in a predetermined measurement section of the spindle motor is used as the no-load reference value and the load reference value. For example, the maximum value or the integral value of the motor current in the same measurement section can be used. .
[0049]
【The invention's effect】
  As described above, the tool abnormality detection device according to claim 1 erroneously determines whether there is a tool abnormality even when the difference between the motor load during actual operation and the motor load during idle operation is small. There is no risk of doing so, and accurate judgment can always be executed. Therefore, there is no risk of performing unnecessary work such as stopping the machine tool and replacing the tool due to erroneous determination of tool abnormality, for example, by reducing efficiency and replacing normal tools due to such work. There is no waste of expenses.
[0050]
[0051]
  Claim 2In the described tool abnormality detection device, the reference value at load is calculated based on the motor load in a predetermined number of trial machining, so if trial machining is performed prior to machining of the workpiece as a product, the evaluation reference value is further increased. Can be accurate.
[0052]
  Claim 3In the described tool abnormality detection device, the reference value at no load and the reference value at load are described as the average or variance of the sampling values for a predetermined period or the predetermined number of times, or a combination of the average and variance, so that there is a possibility of erroneous determination. This makes it possible to carry out a more precise determination with less.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an overall configuration of a machine tool according to an embodiment.
FIG. 2 is an explanatory diagram of a configuration in the vicinity of a spindle of a machine tool according to an embodiment.
FIG. 3 is a block diagram illustrating a configuration of a control system of the machine tool according to the embodiment.
FIG. 4 is a flowchart of main processing executed by the CPU of the machine tool according to the embodiment.
FIG. 5 is a flowchart of a comparison determination process executed by the CPU of the machine tool according to the embodiment.
FIG. 6 is an explanatory diagram of a display example of a no-load variation, a load-time variation, and a threshold value relationship in the machine tool of the example, and FIG. 6A shows that the no-load variation and the load variation are excessive. 6B is an explanatory diagram when the threshold value is smaller than the upper limit value of no-load variation, and FIG. 6C is a lower limit value of the threshold value variation when loaded. FIG. 6D is an explanatory diagram when the threshold value is between the load variation and the load variation.
7 is a graph of a measurement result of a motor current in the machine tool of the example, FIG. 7A is a graph of an example of a measurement result of a motor current during actual cutting, and FIG. 7B is a no-load machining. It is a graph of an example of the measurement result of the motor current at the time.
[Explanation of symbols]
  DESCRIPTION OF SYMBOLS 10 ... Machine tool 12 ... Splash guard 14 ... Table 16 ... ATC magazine 20 ... Main body 22 ... Operation panel 23 ... State switch (operating state input means) 24 ... Work exchange port 25 ... Liquid crystal display (result display means) 26 ... Inspection hatch 27 ... Numeric keypad (reference value input means) 28 ... Spindle 30 ... Spindle motor 32 ... Nut 34 ... Ball screw 36 ... Ball screw mechanism 38 ... Z-axis motor 40 ... Guide rail 42 ... Slide 50 ... Spindle control system 52 ... Spindle servo amplifier 54 ... Axis control circuit 60 ... Z-axis control system 62 ... Z-axis servo amplifier 64 ... Axis control circuit 70 ... Microcomputer unit 72 ... CPU (load detection means, determination means, comparison means, evaluation reference value setting means) 74 ... RAM

Claims (3)

A tool comprising: load detection means for detecting a motor load of a main spindle or a feed axis of a machine tool; and determination means for judging whether or not the tool of the machine tool is abnormal by comparing the detected motor load with an evaluation reference value. In the anomaly detection device,
An operation state input means for performing an input indicating whether the machine tool is idling or actual operation;
A reference value input means for inputting the evaluation reference value;
The evaluation reference value input through the reference value input means is a no-load variation range that is a variation range of the motor load during idle operation and a load variation range that is a variation range of the motor load during actual operation. Comparing means for determining whether or not the evaluation reference value is appropriate based on whether or not
A result display means for displaying the no-load variation range, the load variation range and the evaluation reference value so that mutual magnitude relations can be identified, and displaying according to the result of the judgment by the comparison means; A tool abnormality detection device characterized by that. In the tool abnormality detection device according to claim 1,
The tool variation detecting device, wherein the load variation range is calculated based on the motor load in a predetermined number of trial machining operations . In the tool abnormality detection device according to claim 1 or 2,
The tool abnormality detecting device, wherein the no-load variation range and the load variation range are each described by a combination of an average and a variance of sampling values for a predetermined period or a predetermined number of times .

Images