JPH0985586A - Detecting device and method for cutting state of rotational cutting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detecting device and a detecting method, able to detect a change of the cutting state at high precision also when a change of cutting torque is small, and by which instantaneous increase of cutting torque by chatter vibration is not accidentally detected in mistake for increase by abrasion of a tool. SOLUTION: Cutting torque to act on an end mill 1 is measured by a magnet- striction type torque sensor 14, the cutting torque is integrated by the time per rotation of the end mill 1 by means of a waveform area calculating device 19, and a cutting torque integral value is calculated. Thus obtained cutting torque integral value is compared with the threshold value previously set and stored in a storing device 2 by a comparing device 20, when the cutting torque integral value exceeds the threshold value, a warning signal is output to a controller 21 of a machine tool.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutting state detection device and a detection device for a rotary cutting tool for monitoring changes in the cutting state due to tool wear in cutting using a rotary cutting tool such as an end mill and a drill. It is about the method.

[0002]

2. Description of the Related Art As a detection method for monitoring the cutting state of a rotary cutting tool of this type, for example, a method of predicting breakage of a rotary cutting tool due to tool wear or the like is disclosed in Japanese Laid-Open Patent Publication No. 6-1.
The one described in Japanese Patent No. 98547 is known. In the detection method described in this publication, as shown in FIG. 4, first, a test work is experimentally cut with a new tool (cutting tool), and the cutting torque is preferably set as a cutting torque pattern A including a time change. It is detected, and based on this, the breakage risk torque level B of a size before the breakage of the tool is set. Then, the fluctuation of the cutting torque pattern C during the actual cutting is compared with the breakage risk torque level B, and the actual cutting torque pattern C becomes larger than the breakage risk torque level B as shown by the chain line. If it is detected, it is judged that there is a risk of breakage, the motor that rotates the tool is stopped, step back is performed, or the clutch of the rotary drive system is disengaged, and the cutting torque is further increased. Prevent from becoming. The reference numeral D in the drawing indicates the torque level at which the tool is actually predicted to break based on the cutting torque pattern A.

[0003]

However, in such a rotary cutting tool, the change in cutting torque due to wear may be relatively small depending on the type and cutting conditions. For example, FIG. 5 shows a carbon steel material (SN) produced by a single-blade end mill having an outer diameter of 10 mm and a cutting blade made of cemented carbide.
CM439) shows the relationship between the flank wear width VB of the cutting edge and the cutting torque when shoulder cutting is performed. As shown in FIG. 5, the cutting torque is equal to the wear width VB.
It is almost constant regardless of B. However, the cutting conditions for the shoulder cutting shown in FIG. 5 are as follows.・ Cutting speed: 150m / min (spindle speed 3000r.
pm) ・ Feed: 0.05mm / rev ・ Incision: 4.0mm ・ Cutting width: 2.0mm ・ Down cut, dry cutting

However, when the change in the cutting torque due to the tool wear is small as described above, the actual cutting torque pattern C does not exceed the breakage risk torque level B in the conventional detection method described above. The cutting is not interrupted. In other words, until the cutting torque reaches a magnitude just before the tool is broken, the cutting edge is used for cutting while the tool is still worn, which leads to deterioration of the finished surface accuracy. It is inevitable. On the other hand, in the above detection method, when chatter vibration or the like that is not caused by tool wear or the like occurs in the tool during cutting, the cutting torque is momentarily remarkably increased, and the actual cutting torque pattern C becomes the breakage risk torque. There is also a problem that the level B is exceeded, and this is detected as due to wear of the tool, and the cutting is interrupted although there is actually no risk of breakage.

The present invention has been made in view of such circumstances, and it is possible to detect a change in the cutting state due to tool wear or the like with high accuracy even when the change in the cutting torque is small, and chatter vibration. It is an object of the present invention to provide a detection device and a detection method for a cutting state by a rotary cutting tool that does not erroneously detect an instantaneous increase in cutting torque due to wear or the like.

[0006]

In order to solve the above problems and to achieve such an object, a detection device according to claim 1 of the present invention is a measurement device for measuring a cutting torque acting on a rotary cutting tool. And a cutting means for calculating a cutting torque integral value by integrating the cutting torque measured by the measuring means with a time per a predetermined number of rotations of the rotary cutting tool. The detection method according to claim 5 uses such a detection device to measure a cutting torque acting on a rotary cutting tool, and integrates the cutting torque with time per predetermined number of rotations of the rotary cutting tool to perform cutting. A feature is that a torque integral value is calculated. However, according to the present invention, by detecting the cutting state based on the integrated value of the cutting torque per predetermined number of rotations of the rotary cutting tool in this manner, even if the change of the cutting torque itself is small, the cutting torque is small. While it is possible to reliably detect the change in the integrated value, the instantaneous increase in cutting torque due to chatter vibration etc. has a very short action time and has little effect on the integrated value of cutting torque. It can be prevented from being detected as due to tool wear or the like.

Here, in the above detection device, the cutting torque integral value is provided in advance by providing a comparing means for comparing the cutting torque integral value calculated by the computing means with a preset threshold value, or in the detecting method. By comparing with the set threshold value, if the cutting torque integrated value exceeds this threshold value, it is judged that the cutting state has reached a predetermined dangerous area due to tool wear etc. and the interruption of cutting etc. is prompted. You can Further, by adopting a magnetostrictive torque sensor as a measuring means in the above detection device, or in the above detection method, by measuring the cutting torque acting on the rotary cutting tool by the magnetostrictive torque sensor, it is possible to contact the cutting tool in a non-contact manner. Therefore, it is possible to directly measure the cutting torque with high accuracy without affecting the measurement of the cutting torque. Further, in the detection device, the arithmetic means is configured to integrate the cutting torque in a time period per one rotation of the rotary cutting tool to calculate the cutting torque integrated value, or in the detection method,
By integrating the cutting torque with the time per revolution of the rotary cutting tool to calculate the cutting torque integral value, it is possible to measure the change in the cutting state in smaller time units and perform more rigorous detection. Becomes

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the detection apparatus of the present invention and an embodiment of the detection method of the present invention performed using the detection apparatus will be described below with reference to FIG. In FIG. 1, reference numeral 1 indicates a single-blade throw-away type end mill as a rotary cutting tool according to the present embodiment. The end mill 1 has its base end portion held by a holder 2, and further this holder. By attaching 2 to the spindle 3 of the machine tool, the spindle 2 is rotated around the axis O together with the holder 2 and the spindle 3, and is fed in the axis O and the feed direction orthogonal to the axis O to the tip of the end mill 1. The workpiece 5 placed on the table 6 of the machine tool is cut by the cutting blade 5 of the attached throw-away tip 4. On the other hand, a cylindrical wall-shaped extending portion 2a is formed at the tip of the holder 2, and the extending portion 2a and the end mill 1 housed in the extending portion 2a are formed.
A cylindrical support body 9 connected to an arm 8 extending from the spindle head 7 of the machine tool is provided between the bearing 10 and the body circumference of the bearing 10.
The support body 9 is interposed between the end mill 1 and the holder 2 which rotate integrally, and is fixedly supported on the spindle head 7. There is.

[0009] And, on the body circumference of the end mill 1,
12 are formed by forming a magnetostrictive film made of Fe-Ni-Mo-B by using a plasma spraying method, while facing the magnetostrictive layers 11 ..., 12 ... A pair of coils 13, 13 are arranged on the inner peripheral portion of the support 9 so as to surround the body peripheral portion of the end mill 1 side by side in the direction of the axis O, and these magnetostrictive layers 11 ,. , 13 constitute a magnetostrictive torque sensor 14 as a measuring means in the present embodiment. Here, in the present embodiment, as shown in FIG. 1, the magnetostrictive layers 11 ..., 12 ... Are respectively ± 45 ° with respect to the axis O direction.
When the cutting torque is applied to the end mill 1 at the time of cutting and a twisting stress acts, the magnetostrictive layers 11 ... A compressive stress is generated and its permeability changes, and the self-inductance of the coils 13, 13 also changes in proportion to this, so the cutting applied to the end mill 1 from the difference in the inductance of these two coils 13, 13. Torque is measured.

On the other hand, the coils 13 and 13 are connected to a sensor amplifier 16 via a preamplifier 15 built in the arm 8. The sensor amplifier 16 further includes a low pass filter 17 and an A / D converter 18. The magnetostrictive torque sensor 1 is connected to the waveform area calculation device 19 as the calculation means in the present embodiment via
The output value of the cutting torque measured by 4 is used as a waveform of the cutting torque with respect to time, and this waveform area calculating device 19
It is designed to be input to. Then, in the waveform area calculation device 19, the cutting torque is integrated from the waveform of the input cutting torque by the time per predetermined number of rotations of the end mill 1 to calculate the cutting torque integrated value. In particular, in the present embodiment, the cutting torque is integrated by the time per one rotation of the end mill 1 to calculate the cutting torque integral value.

Further, in the present embodiment, the waveform area calculating device 19 is connected to a comparing device 20 as a comparing means in the present embodiment, and the comparing device 20 is further connected to the control device 21 of the machine tool. ing. on the other hand,
A storage device 22 is separately connected to the comparison device 20, and the storage device 22 stores a threshold value of a cutting torque integral value preset according to the type of cutting tool, cutting conditions and the like in a database. Remembered Then, in the comparison device 20, the cutting torque integrated value output from the waveform area calculation device 19 is compared with the threshold value stored in the storage device 22, and when the cutting torque integrated value exceeds the threshold value, An alarm signal is output to the control device 21, whereby the motor of the machine tool is stopped, step back is performed, or the clutch of the rotary drive system is disengaged so that the cutting torque is further increased. Configured to prevent. In addition, these comparison devices 20,
The processing by the storage device 22, the waveform area calculation device 19 and the like is specifically performed by a computer or the like.

However, in the detecting device thus constructed and the detecting method performed by using the detecting device, the cutting edge 5 of the end mill 1 cuts the work W and the cutting applied to the end mill 1. The torque is the magnetostrictive layer 11 ...
Coil 13, 1 due to tensile / compressive stress acting on 12 ...
Magnetostrictive torque sensor 1 as the change of the inductance of 3
4 is measured and output, and is input to the waveform area calculation device 19 via the preamplifier 15, the sensor amplifier 16, the low-pass filter 17, and the A / D converter 18 as a fluctuation waveform of the cutting torque with respect to time. Then, in the waveform area calculation device 19, an integrated value of the cutting torque per predetermined number of rotations of the end mill 1 (per rotation in this embodiment) from the input cutting torque, that is, the predetermined number of rotations of the fluctuation waveform. The area of time per hit is sequentially calculated and output. Further, in the present embodiment, this result is input to the comparison device 20 and is compared with a preset threshold value of the cutting torque integral value stored in the storage device 22 to obtain the input cutting torque integral value. When exceeds the threshold value, an alarm signal is output to the control device 21 to take a measure to reduce the cutting torque.

As described above, in the above-described detecting device and detecting method, the magnetostrictive torque sensor 14 as the measuring means is used.
The cutting torque measured by means of the waveform area calculating device 19 as the calculating means is calculated as an integral value per predetermined number of rotations of the end mill 1, so that it is measured with respect to a change in cutting state due to tool wear of the cutting edge 5 or the like. Even if the fluctuation of the cutting torque is relatively small, the fluctuation can be surely grasped as the integrated value of the cutting torque, and the change of the cutting state can be detected with high accuracy. On the other hand, even if the cutting torque may momentarily increase due to chatter vibration, etc., it is possible to suppress the influence on the entire calculated integrated value of the cutting torque. Only with this, it is possible to prevent the abnormal cutting state from being detected. Therefore,
According to this embodiment, it is possible to solve the above-mentioned problems of the conventional technique and improve the accuracy of detecting the cutting state such as the tool wear amount. Further, by sequentially calculating and outputting the cutting torque integrated value during cutting in this way, it is possible to detect the cutting state in real time and estimate the tool wear amount, etc. It is also possible to maintain processing accuracy by performing correction such as changing the path during processing.

Further, in the present embodiment, the waveform area calculation device 19 is connected to the comparison device 20, and the integrated cutting torque value calculated by the waveform area calculation device 19 is stored in the storage device 22 in the comparison device 20. It is configured to be compared with a preset threshold value. Therefore, by appropriately setting this threshold value according to the type of tool, cutting conditions, etc., the cutting torque integral value increases and exceeds the threshold value as the cutting torque increases due to the progress of tool wear. In this case, this is judged to be a dangerous cutting state in which tool breakage or the like may occur, and as described above, a warning signal is output to the control device 21 to reduce the cutting torque or interrupt the cutting operation itself. It is possible to avoid such a dangerous state. Further, by comparing the integrated value of the cutting torque with the preset threshold value in the comparison device 20 and feeding back the result to the control device 21 of the machine tool to control the machine tool, It is also possible to promote automation of work and further expansion of unmanned work. In the present embodiment, the comparison device 20 is connected to the control device 21 of the machine tool in this way to control the same, but instead of this or in addition to this,
An alarm device activated by the warning signal may be used to prompt the operator to warn.

On the other hand, in this embodiment, the magnetostrictive torque sensor 14 is used as the cutting torque measuring means as described above.
The cutting torque applied to the end mill 1 is measured as a change in the inductance of the coils 13, 13 from the tensile / compressive stress acting on the magnetostrictive layers 11 ,. That is, the end mill 1
It is possible to directly measure the cutting torque without contacting the blade, so that it is possible to prevent the influence of the contact of the contact point etc. on the cutting torque measurement, and it is possible to perform more accurate measurement. By calculating the cutting torque integral value based on the cutting torque thus measured, it is possible to further improve the detection accuracy of the cutting state.

Further, in the present embodiment, the waveform area calculating means 19 calculates the cutting torque integral value by integrating the measured cutting torque with the time per one rotation of the end mill 1, that is, the cutting. By obtaining the integrated value of the cutting torque with reference to the unit rotation of the tool, it is possible to obtain the advantage that the change in the cutting state can be strictly detected at each finer time. When the cutting blade 5 of the rotary cutting tool is one as in the end mill 1 of the present embodiment, the cutting torque integrated value per one rotation is obtained, and the situation such as wear of the cutting blade 5 is directly obtained. It is possible to reliably grasp the cutting state by detecting the. However, depending on the type of rotary cutting tool, the number of blades, or the cutting conditions, the cutting torque may be integrated in the time per one rotation or more, or conversely, 1/2 rotation, 1/3 rotation, etc. The cutting torque integral value may be calculated by integrating the time per rotation number below. For example, in the case of shoulder milling with a two-blade end mill arranged at equal intervals in the circumferential direction, the waveform of the cutting torque by both cutting blades alternates every 1/2 rotation, so 1 / By calculating the cutting torque integral value by the time per two rotations and analyzing the tendency of the integral value obtained alternately, it is possible to detect the cutting state such as which cutting edge is worn by the tool in more detail. It will be possible.

[0017]

EXAMPLE Next, as an example, with the progress of the flank wear of the cutting edge 5 as a cutting state when shoulder cutting by the end mill 1 was performed using the detection apparatus of the above-described embodiment, It was investigated how the cutting torque and its integrated value changed. However, the cutting conditions in this example are the same as the conditions for shoulder cutting shown in FIG. 5, and therefore the relationship between the flank wear width VB and the cutting torque obtained in this example is the same as that in FIG. Become. Further, in these cuttings, the flank wear width VB at the position of 1/2 of the cut in the axis O direction of the cutting edge 5 is measured by an optical tool microscope.

FIGS. 2 (a) to 2 (f) show the waveforms obtained by passing the cutting torque measured for each flank wear width VB through a low-pass filter of 1.5 kHz. FIG. 5 shows the relationship between the flank wear width VB and the cutting torque. However, as the flank wear width VB increases, the increase in the cutting torque itself due to the increase in the contact area between the cutting edge of the cutting edge 5 and the workpiece is slight, and the flank wear width VB can be detected from this. It is difficult.

On the other hand, FIG. 3 shows that the result of FIG.
The relationship between the cutting torque integrated value obtained by integrating the cutting torque per one revolution of the end mill 1 and the flank wear width VB is shown. It can be seen that the integrated value of the cutting torque is gradually increased accordingly. Therefore, based on the result of FIG. 3, it is sufficiently possible to detect the cutting state represented by flank wear from the integrated value of the cutting torque, and the reference numeral X in FIG. Set the threshold as shown,
It is also possible to determine whether or not the cutting state is a dangerous state that causes damage to the tool by comparing this with the calculated cutting torque integrated value. In the present embodiment, the cutting torque may momentarily increase due to chatter vibration that occurs during cutting, but this has a negligible effect on the cutting torque integrated value.

[0020]

As described above, according to the present invention,
The cutting state of the rotary cutting tool can be detected from the integrated value of the cutting torque, which makes it possible to reliably grasp the cutting state even when the variation of the cutting torque with respect to the variation of the cutting state is small. Even if a large amount of cutting torque is momentarily applied due to chatter vibration, etc., it is possible to avoid a situation in which this is mistakenly recognized as due to tool wear, so it is possible to improve detection accuracy. It will be possible.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a detection device of the present invention.

FIG. 2 is a flank wear width V according to an embodiment of the present invention.
It is a figure which shows the waveform of the cutting torque measured for every B.

FIG. 3 is a diagram showing a relationship between a flank wear width VB and an integrated value of cutting torque based on the result shown in FIG. 2 in an example according to the present invention.

FIG. 4 is a diagram showing a conventional method of detecting a cutting state.

5 is a diagram showing the relationship between the flank wear width VB and the cutting torque, which is similar to that obtained based on the results shown in FIG. 2 in the example according to the present invention.

[Explanation of symbols]

 1 End Mill (Rotating Cutting Tool) 2 Holder 3 Spindle 5 Cutting Edge 9 Support 11, 12 Magnetostrictive Layer 13 Coil 14 Magnetostrictive Torque Sensor (Measuring Means) 19 Waveform Area Calculator (Calculating Means) 20 Comparison Device (Comparing Means) 22 Storage device

Claims (8)

[Claims] 1. A measuring means for measuring a cutting torque acting on a rotary cutting tool, and a cutting torque measured by this measuring means is integrated with respect to a time per predetermined number of rotations of the rotary cutting tool to obtain an integrated cutting torque value. An apparatus for detecting a cutting state by a rotary cutting tool, which comprises: 2. The cutting state by the rotary cutting tool according to claim 1, further comprising a comparing unit that compares the cutting torque integrated value calculated by the calculating unit with a preset threshold value. Detection device. 3. The apparatus for detecting a cutting state by a rotary cutting tool according to claim 1, wherein the measuring means is a magnetostrictive torque sensor. 4. The calculating means calculates the integrated value of the cutting torque by integrating the cutting torque with a time per one rotation of the rotary cutting tool.
A device for detecting a cutting state by the rotary cutting tool according to claim 3. 5. A rotation characterized in that a cutting torque acting on a rotary cutting tool is measured, and the cutting torque is integrated by a time per a predetermined number of rotations of the rotary cutting tool to calculate a cutting torque integrated value. A method of detecting the cutting state by a cutting tool. 6. The method for detecting a cutting state by a rotary cutting tool according to claim 5, wherein the integrated cutting torque value is compared with a preset threshold value. 7. The method for detecting a cutting state by a rotary cutting tool according to claim 5, wherein the cutting torque acting on the rotary cutting tool is measured by a magnetostrictive torque sensor. 8. The cutting torque integrated value is calculated by integrating the cutting torque with a time per one rotation of the rotary cutting tool to calculate the cutting torque integral value. A method of detecting the cutting state by a rotary cutting tool.