JPH02503171A - Intelligent insert with integrated sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Intelligent insert with integrated sensor selected! Sushi Sushi 1. Field of invention The present invention provides an integrated system for generating signals indicative of tool status and operating parameters. Attached I; relates to a cutting tool or insert having a sensor.

2. Description of conventional technology The development of unmanned machining centers for factory use is progressing rapidly, and today there are various The nature of this type of numerically controlled machine makes it suitable for unmanned manufacturing. similarly Automated material inspection systems have also been developed; The main difficulty in realizing this is the use of computer-controlled, unmanned machining lack of effective and reliable sensors to monitor data manufacturing systems; It is. Accurately sensing the cutting tool condition is important for operation, but so far could not be achieved. Immediately recognize when a tool breaks or cracks. Sensing is important in order to Also, if the tool wears out more than the storage capacity, or any other deviation of the desired parameters, the tool can be quickly replaced. In order to obtain a signal, a signal is needed to indicate its status. Tools become worn or dull; or if it breaks, it may cause a substandard product to be manufactured or damage to the manufactured parts. This may cause damage to the product or the machine tool itself.

As a result, manufacturing costs increase and manufacturing capacity is lost. Thus, the present invention One important feature prevents such losses and satisfies unattended machining centers. The goal is to ensure safe driving.

In conventional technology, the manufacturing process is monitored while it is being carried out within the machining system. , adaptive controls have been developed to change machining conditions so that the machine is more productive. Ru.

An adaptive control system that operates by sensing the current of the drive motor of the machine spindle. is already commercially available.

Also, some force sensing and feedback control systems are commercially available, but Generally speaking, it is satisfactory as shown in the prior art cited below. I can't think of it. Therefore, the present invention is accurate, reliable, and Designed to meet current requirements for adaptive control that can be used in It is something that

If the monitored machine is on the production line and fails to detect damage to a single tool. When on individual machining centers, the entire production line is affected. suffer a much greater loss. Therefore, the present invention is widely applicable to these types of processes. It is available for use.

In conventional technology, the dynamics of chip generation during machining has not been studied. Various methods have been developed to measure machining forces.

For example, Tolsti (Tl1st2) D, J and Andrews (Mu mdr *vs) “Critical consideration of sensors for unmanned machining” by G and C (MuCr1 tical Review al 5 sensors for Hamssmed MsckjmtB) (Annual Report of C, 1, 1, P 3z-4, 191 At υ, several types of sensors have been tested for reliability in unattended machining operation. being investigated. This paper aims to achieve the full potential of unmanned machining centers An important problem that must be solved in speed of removal and ensure that corrective action can be taken in the event of an accident or rupture. The aim is to develop reliable and effective sensors that can this theory Although the text considers the sensors available at the time, all of these Reliability due to physical filtering of the signal on the tool due to interference from the tool support It has serious drawbacks in terms of performance and direct responsiveness.

Typical dynamometer sensors that attach cutting tools are Kunio Uehara and Yuichikan. ``Elucidation of the mechanism of chip generation by measuring acoustic emissions'' by Hen. 1ific&tio++ of Chip For+astiom cTh* n1sa Through Acoustic Emissiam Ntsusu rt+a@mts” (Annual Report of C,1,R,?, 33-1.1914) described in the paper. Dynamometer or platform for attaching tool holders The worm uses DC level measurements to sense balanced phenomena such as average cutting force. The results are satisfactory. However, the AC component or high side number force is or by interconnecting surfaces between the insert and its tool holder, or between the tool holder and the dynamometer. , and filtered by the dynamics of the measurement system itself. As a result, the dynamometer is I KB Phenomena occurring above s cannot be detected.

Attaching an accelerometer to a tool holder and using the assembly with a force sensor B, Lindbtrs and L Limdström. "Measurement of segmentation frequency in the process of chip generation" ("III ξ5sireants of the SBm*ntatian FrCq+ uney in th* Chip For+astioIIProctssJ ) (Annual report of C, 1, R, P, 33-1.1H3) There is. While accelerometers can sense extremely high frequencies, The insert is physically clamped into the pocket of the tool holder and 5-10 due to the small ability to transmit signals through the interconnect plane with the KH! As described above, the ability to sense phenomena occurring at the cutting edge of the tool is limited.

In this way, high-frequency phenomena that occur just at the cutting edge of the tool can be efficiently transferred to the tool holder. Therefore, the accelerometer mounted on the tool holder is cannot sense the high frequency forces or vibrations experienced by the vehicle.

Under normal commercial cutting conditions, the frequencies passing through the crystal grains are within the band of Nus. It is in. Frequency and segmentation of chips passing through this crystal grain and other forces The mechanical behavior of the material reflects this noise generation and, as a result, its structure and It vibrates in a mode and frequency that match the applied excitation frequency. Tool holder and As a result of the movement of the tool post, the workpiece develops a wave-like component on its surface following this movement. will have. In traditional systems that utilize existing sensors, these Movement is filtered and cannot be sensed for either process monitoring or process control. I can't do it.

Summary of the invention The present invention carries the sensor directly on the tool and acts on the insert without filtering. relating to chip inserts or chip tools that provide signals that can indicate vibrations and forces caused by . This insert is of standard size and shape, but can be set on the body within its circumference. The sensor has a means for attaching a sensor that emits a high frequency sensing signal in response to vibrations. to ensure that all relevant vibrations and forces are determined. be.

In various forms of the invention, the insert is an accelerometer, preferably a piezoelectric sensor. Directly used for mounting sensors, i.e. piezoelectric or piezoelectric emitter sensors. Ru. These sensors can sense cutting tool phenomena such as force, temperature, vibration etc. With the goal.

In one form of the invention, the piezoelectric film is the material for forming the insert. joined as a part or integrally formed, or piezoelectric or piezoresistive can be attached directly to the outer surface of the cutting tool. Insert cutting pressure sensitive contacts used on piezoelectric or piezoresistive (piezoelectrically sensitive) films to You can receive the number.

Cutting tools, in particular, use deposited piezoelectric, piezo-sensitive, or heat-sensitive materials. If so, the sensor can be provided with a relatively small increase in cost. Currently on sale Most carbide cutting tools or inserts are already coated. , although additional coatings are required to impart the necessary layers or piezosensitivity, Subsequent application of material to the cutting tool can be easily accomplished.

For example, silk screen printing and thick film techniques can be used.

The circuit for amplifying the low level signal is installed inside or inside the tool holder for the first stage amplification. can be carried on a rotating cutting head. This head has an insert to external circuits, e.g. optical couplers, slip rings or radio frequency transfer circuits. Figure 1 shows the worn cutter engaging the workpiece. a partial schematic diagram showing a cutting tool and generated chips; FIG. 2 is a perspective view of a cutting tool according to the invention with a measuring instrument mounted directly thereon; , FIG. 3 is a cross-sectional view of the cutting tool shown in FIG. 2 in which the first type of sensor is used; FIG. 4 shows an acceleration sensor used with a tool insert formed in accordance with the present invention. Yet another configuration, FIG. 5, for use with a cutting tool formed in accordance with the present invention. Cross-sectional view of the model acceleration sensor, FIG. 6 shows a cutting insert having a sensor according to the invention when the cutting insert breaks. A plot of a typical response signal received from the Figure 7 shows piezoelectric or piezoresistive materials used to sense vibrations and forces. A perspective view of the deposited cutting tool, FIG. 8, showing the deposited layer of piezoelectric or piezoresistive material. A partially enlarged sectional view passing through the center of FIG. FIG. 9 shows a rotating tool with a tool insert according to the invention mounted thereon. FIG.

Detailed description of suitable rush examples In FIG. 1 a schematic representation of the tools used for machining is shown. as a whole The cutting tool or insert, designated lO, has a sharp cutting edge portion 11 and is A tool surface 12 and a tool side 13 are adjacent to the cutting edge portion. This side 13 is Indicates the condition of worn tools. Workpiece 14 is engaged by cutting portion 11 . As the tool moves below the surface of the workpiece 14, the chip, designated 15, is removed from the workpiece. The chips 15 are disposed along the shear plane indicated by reference numeral 16. Separated and discarded. As the tool wears, it becomes difficult to move the tool relative to the workpiece. The force required for this changes, the smoothness of the machined surface 14A changes, and the cutting edge portion The vibrations occurring in 1 and similar phenomena are indicative of the condition of the tool. By segmentation of chips The vibrations of the tool 10 are transmitted as waves in the surface finish of the surface 14A. Ru. However, in most operating systems, the vibration of the cutting edge of the tool is at a high frequency. , and this frequency is the interconnection between the tool and the clamp that holds it in place. filtered by

Conventionally, the cutting tool 10 is clamped to a tool holder or tool post, typically recessed. held on at least two lateral sides of the chamber and clamped to its bottom surface; Ru.

The tool or cutting insert is generally square and has one or more cutting edges on it. I can get it. The model of the cutting edge used depends on the material of the workpiece and the work piece. depending on the surface finish required for the surface and other 7 actors.

2 and 3, a cutting tool or insert according to a first embodiment of the present invention is shown. The tool holder 17 is attached to the tool holder 17 by means of the clamp finger 18 and is indicated by the reference numeral 20. a block of suitable material held by the clamping fingers 18; is a support block that is held by the screw 18A and interferes with the seating surface of the tool holder 17. It is held against 19. The cutting insert or tool 20 may be It can be reversed. The spacer portion 21 of the insert is shown in a state where it is formed for cutting. has been done. This is hollowed out as desired, and as a whole, the typical tool 10 in FIG. It can be adapted to the shape of. The cutting insert 20 is formed in the center. The piezoelectric sleeve 23 has a hole 22 (FIG. 3) in the hole 22. is glued to the inner surface of the This sleeve 23 is fastened by a suitable adhesive technique, Holds the piezoelectric body in place. Preferably, this adhesive material is electrically conductive and the sleeve so as to form an electrical contact to the outer surface of the

The hole 24 inside the sleeve 23 has a contact point to the inside surface of the piezoelectric sleeve. Ru. - The spring contact 25A constituting the bellows type is used as an electrical contact.

This contact 25A realizes contact with the support block 19, which is connected to the tool holder The conductors can be connected to block 19 to transmit signals. Ru.

Together, the mass 25 and the piezoelectric sleeve form an accelerometer. Mass 25 is in the sleeve A load is applied to change the voltage between the outer and inner surfaces of the sleeve, and this change in voltage is It is sensed by the conductor from the router 17 and the contact 25A. Shaking the cutting insert 20 The motion is picked up by the mass, which causes a shear force to be applied to the sleeve. An electric current is placed within the preferably radially polarized piezoelectric sleeve 23 between the inner and outer surfaces. pressure is generated. Vibrations affecting the cutting tool are sensed, thereby causing An output voltage proportional to the shear force is generated. Cut-in as described below. If the circuit 20 were to break, the amplitude of the vibration and therefore the magnitude of the output voltage would be significantly reduced. It is possible to detect early cracks and use the signal to generate an alarm.

FIG. 4 shows a modification of the invention. Sleeve 27 is a cutting insert Or it is glued to the inner surface of the hole 22 of the tool 20. This sleeve 27 can be any suitable It can be made of any material. The cutting tool is made of high speed steel or carbide material. If formed, it can be fused or laser or electronic welded. Se For lamic cutting tools or inserts, silicone-coated stainless steel It is possible to use a sleeve. Silicon nitride and sialon (5IALON) ) with ceramic cutting inserts made of zirconium or titanium. You can also use leaves. Use an alumina cutting insert or tool. from the metal alloy sold under the trade name KOVAR. A sleeve consisting of:

The inner bore 28 of the sleeve 27 is equipped with internal threads designated 29 and a high-bandwidth accelerometer. It is tightly screwed into a metal insert. Therefore, this accelerometer is suitable for cutting positioned on the central axis of the insert 20 and directly and tightly physically attached to the insert come into contact with. This means that all vibrations inside the insert are picked up by the accelerometer. It means to be given up. External vibrations affecting the insert are also sensed and therefore Therefore, all vibrations or movements of the cutting insert are transmitted to the accelerometer.

Accelerometer 29 can be used to capture vibrations encountered by the accelerometer. Connected to appropriate circuits to control feed rate, cutting inserts or tool changes. Provides information on insert breaks, cracks or chipping. vibration vibration Circuits that provide an output as a function of number are suitable.

FIG. 5 shows a further modified embodiment of the cutting insert and sensor of the present invention. It is shown. A cutting insert, generally designated 30, may be used if desired. For example, it may be made of a suitable material such as tool steel or ceramic.

In this form of the invention, the cutting tool has a pair of blind holes or has recesses 31, 32, and these blind holes or recesses 31, 32 are on the central axis. Extending inwardly from the opposite surface of the tool. These faces each have the code 33.3 4.

A central bar 35 of the material separates the holes, and this central bar 35 covers the bottom of the holes 31,32. A separate piezoelectric sensor 36 is attached to the bottom with oppositely facing surfaces forming a Supported. These piezoelectric sensors 36 are acceleration sensors and constitute a sensor. It has an inertial mass 37 on the outside of each piezoelectric piece.

Each of the inertial masses 37 is bonded to and attached to a respective piezoelectric sensor. It is equipped with a metal material that constitutes an electrical contact to the terminal. On the outer surface of the mass 37, a suitable Contacts and conductors 39 can be provided.

Each mass 37 as a whole is directly connected to its associated piezoelectric sensor 36; Since it is not fastened to the surface of the hole in the cutting insert, the mass is along the axis 38. It moves under vibration in the direction and applies a load to each sensor. Sensor made of piezoelectric material 36 (preferably a piezoelectric ceramic material) is placed on the surface of the hole in the cutting insert 30. It is glued. The sides of the sensor are usually coated with metal to accommodate the cutting insert. This provides an electrical connection. The mutual connection surfaces between the cutting insert and the piezoelectric body are in contact. Forms a ground connection. The sensing frequency generally represents the state of interest of the cutting tool. Connect a suitable resistor across the sensing surface of the piezoelectric sensor so that The required information can be obtained by measuring the voltage drop that occurs when It will be done.

The circuit that indicates insert rupture is extremely simple as shown in the block diagram in Figure 3. It can be made into something. It is constituted by a piezoelectric sleeve 23, or as shown in FIGS. A voltage signal from an accelerometer of the type shown in FIG. 5 appears on conductor 26A126B. child The output signal of is a voltage signal as shown, and is applied through an appropriately designed amplifier 43. amplified.

The signal on line 44, which is the output of amplifier 43, is preferably provided to comparator 45. , this comparator 45 is an amplifier 4 with a reference point 45A set to a certain level. During normal operation, the comparator provides no output, but if rupture occurs. When this happens, the output of the accelerometer increases rapidly as shown in Figure 6, and the voltage on line 44 increases. When the reference level is exceeded, the comparator provides an output, which is used to convert the signal An alarm or other indication is provided through circuit 45A.

Alternatively, the tool insert and the sensor rotate in a holder or head, in particular When used above, the sensor 23 made of piezoelectric material or other acceleration sensor The output voltage of can be used to light the LED 46 (FIG. 3). piezoelectric body If sufficient voltage is generated from or if an amplifier 43 can be used. , this LED 46 can be connected directly to the lead from the piezoelectric sensor.

A photosensitive transistor 46A is used to sense the light level from the LED 46 and answer the question. Generate the problem signal and a! can provide output for recording performance. . The LED 46 and its associated circuitry can be mounted on a rotating tool holder. Meanwhile, the receiving sensor 46A is attached to the frame of the machine tool, and the receiving sensor 46A is mounted on the insert. The signal from the sensor can be optically coupled to the output circuit. This circuit is As shown with reference numeral 17A in Fig. 2, it can be stored in a container in a tool holder or in a kiln. I can do that. The chamber can be covered using a removable cover.

Figure 6 shows that the piezoelectric sensor mounted on the tool insert is similar to other similar sensors. A typical plot of the output from the sensor is shown. Figure 6 shows unnecessary frequencies The voltage is on the vertical axis (y-axis) and time after electronic filtering to remove This is shown on the horizontal axis (X-axis). Normal vibration is about 1 as shown by line 47A. Provides a constant output voltage. Due to the rupture, the magnitude of the output increases as shown by line section 47B. The sharpness changes. The peak amplitude exceeds the reference value 48 for a predetermined time in the comparator 45 , the comparator 45 produces an output for providing an alarm signal.

Cutting inserts or tools are designed to comply with existing US and ISO standards. It is necessary to calibrate the regular vibration values and output alarm values on-site. It is considered unnecessary. After the accelerometer or sensor is in place, the manufacturer will cut the Configuring the insert sensor output offline is a sufficient on-site task. It is possible to do this accurately. Utilizes a circuit that can automatically set conductors. can be used to respond to changes in operating conditions.

Titanate and zirconate materials or other materials such as high Curie point quartz The materials are examples of materials suitable for the construction of the accelerometers illustrated in FIGS. 3 and 5.

The piezoelectric ceramic or piezoelectric structure is heated in a strong electric field and gradually cooled. This ensures that piezoelectric sensitivity is obtained when the cooling phase passes through the ferromagnetic point. Ru. Cutting inserts or tools that are accidentally overheated should be allowed to heat up and gradually cool down. It is restored by tributing the same stage. Disconnect with accelerometer sensor Cutting inserts require cooling during use, either by convection or conduction means, depending on the desired If so, cooling passages can be formed within the tool holder.

Cutting inserts can be formed in a relatively simple way, and individual sensors can also be It can also be formed by a patch method and coated appropriately. Each voltage sensor 23 or The mass 25 or 37 added to 26 should be selected to obtain the desired sensitivity. I can do it.

A suitable force sensor may be constructed as shown in FIGS. 7 and 8, in which case the cutting insert The sert or tool 50 is formed into an appropriate shape as shown, and a cutting edge of the desired shape is formed. It can be provided with a part or a cover. In this case, the cutting blade itself has an integral force. A sensing (piezoelectric or piezoresistive) material is provided. For example, the axial direction indicated by reference numeral 51 A circular piezoelectric film centered on the cutting insert 50 is provided on opposing main sides thereof. It is desirable that the thickness of the piezoelectric material is from 1 or less to 500,711 or less, and cutting If there are any carbonized deposits on the surface of the insert, they may be deposited on the copper or nickel layer. It is desirable that electrical contact be made to the sensor 51. next The cutting tool itself acts as a ground electrode, and the electrical contacts are indicated by the reference numeral 53 in FIG. It can be attached to any suitable external layer as shown in the diagram. 1 of 50 inserts or Two or more lateral sides can be utilized to attach the piezoelectric material. For example, A sensor 54 is provided on at least one circumferential side of the insert or tool 50 and a sensor 54 is provided on at least one circumferential side of the insert or tool 50. 50 is a sensor 54I; it can be provided at any part adjacent to and at a right angle to the sensor 54I; come.

They also have a suitable covering layer 56 (6.2 to 0.5 pm thick) and electrical connections. point 57 can be attached, while cutting insert 50 provides a ground connection. , an electrical excitation signal can be applied across the sensor layer. . Connect a piezoresistive material to a conventional cross-linked circuit and sense the change in resistance under load. It is possible to know.

Also, if desired, the contacts built into the tool holder can function as electrodes. I can also do it. Piezoelectricity or piezoelectricity generated within the force sensor shown in Figures 7 and 8 The resistive voltage or output signal from the piezoresistive bridge is amplified and the signal is The signal magnitude is then correlated to the force on the cutting insert. .

Utilizes the force acting directly on the cutting insert sensed by the devices in Figures 7 and 8. to determine or monitor tool wear or to detect near-breakage conditions. I can do it. The vibration of the tool changes as the tool wears, and the frequency of vibration changes with the frequency of vibration. Detected and analyzed by a detection circuit. Acceleration signal and power signal if desired Redundancy can be provided so that both numbers can be used; Normally, only one of the signals functions.

It is desirable to use low cost piezoelectric materials in commercial applications. excess acid Depositing radio frequency sputtered zinc dioxide in the presence of As shown in FIG. 8, it is an inexpensive means for depositing a piezoelectric layer. car again Bide cutting inserts or tools are generally coated and requires an adhesive layer of copper or other conductive material before depositing the piezoelectric sensing element. .

FIG. 10 shows a cup in which a sensor such as that shown in FIG. 3 or FIGS. 7 and 8 rotates. A typical application of a cutting insert mounted on a tabelug 63 is illustrated. There is.

The cutting inserts 64 are held in place in a suitable manner, and the cutting rods 63 are attached to each insert. a removable cover for a detection circuit 66 coupled to the sensor on the seat 64; A container 65 is provided. The power source for the circuit may also be contained within the enclosure 65. come. Appropriate leads may also be provided for connection to the sensor. light emitting diode When using a cutting insert, the sensor 68 detects breaks, wear, or other mounted adjacent to the head so that it can sense the light output that will indicate the Rukoto can.

Disclosed herein is that the cutting insert or tool is capable of generating vibrations applied to the cutting insert. Directly displays information that displays the frequency or force of the Responds extremely quickly to cutting phenomena. Sensors and tools can be pre-installed and will not cause scratches. There is no need to accurately insert or tighten a contact plate that tends to stick. In addition, There is no physical interconnection filtration between the cutting insert and its supporting structure. do not have. The acoustic emission signal is transmitted by a highly sensitive piezoelectric material at 10 KH! ~3H! Ill ! It can be sensed in the band.

The geometry or profile of cutting tools that utilize the sensor of the present invention may be different for different machine configurations. It may be different from what is shown to suit the needs of the user.

Although the present invention has been described in terms of preferred embodiments, those skilled in the art will understand that the spirit and scope of the invention can be understood by those skilled in the art. It is understood that changes may be made in form and detail without departing from the scope of the invention. cormorant.

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Claims (11)

[Claims] 1. A cutting insert for machining materials with a cutting edge and a solid body and a cutting phenomenon integrally coupled to the insert and acting on the insert. and a sensor that detects a parameter in the cutting edge portion that is a function of Characteristic cutting inserts. 2. said sensor being an accelerometer means within the generally geometrical form of said insert; As a function of the forces and vibrations attached to the core and acting on said cutting insert Claim 1, further comprising said accelerometer means for providing an output. Cutting insert as described. 3. wherein the accelerometer is a conventional wide bandwidth accelerometer; means for attaching to the cutting insert, the insert being attached to the cutting insert; a hole formed in a central portion; a sleeve insert glued to the insert, the accelerometer being attached to the sleeve; Claim 2, characterized in that it comprises means for attaching to the insert. equipment. 4. the sensor has an outer surface secured to the cutting insert; a ring made of a piezoelectric material positioned within an inner hole formed in the plate; a mass fixed to a portion of the piezoelectric material defining the open center; electrical conductor means coupled to the portion connected to the electrical conductor for sensing the voltage output. The cutting insert according to claim 1, characterized in that: 5. The cutting insert has a planar side surface and an axis perpendicular to the side surface. , and the accelerometer means comprises a piezoelectric material, and the cutting insert has a surface. at least one hole, means for adhering the piezoelectric body to a surface of the hole, and the The mass is formed on the surface of the piezoelectric body, and the mass is formed on the surface of the piezoelectric body, and the mass is and means for changing the voltage output of the piezoelectric body when accelerated. The apparatus according to claim 2. 6. deposited on a selected surface of the cutting insert; piezoelectrically sensitive material means in electrical contact, the cutting force being applied to the cutting insert; said piezoelectric material means being positioned such that said piezoelectric material means can change properties when The cutting insert according to claim 1, characterized in that: 7. The piezoelectric sensitive material means is in electrical contact with the cutting insert and the piezoelectrically sensitive material means is in electrical contact with the cutting insert. Claims comprising means for electrically contacting the electroconductive surface of the sensitive material. A cutting insert according to scope 6. 8. a pair of substantially parallel main sides defining the wall thickness, and around the cutting insert. a solid body having an external cutting edge portion; and at least one surface of the cutting insert. a layer of piezoelectrically sensitive material attached to and formed to be electrically sensitive to the surface; the layer of piezoelectric sensitive material having an exposed surface; and means for providing a second electrical contact to an exit surface of the piezoelectrically sensitive material. The layers hold the cutting insert in place and are used to machine the material. A material characterized in that it is provided with an integrated sensor that responds to forces acting on the cutting insert. Cutting inserts for machining materials. 9. Particularly, the piezoelectrically sensitive material is integrally bonded to the surface of the cutting insert. The cutting insert according to claim 8, characterized in that: 10. The piezoelectric material is on at least one side of the cutting insert and on the cutting insert. Claim 8, characterized in that it is attached to at least a part of the outer peripheral cutting edge portion. Cutting inserts as described in . 11. a means for mounting the cutting insert on the tool carrier; and a circuit hand. means formed in the tool carrier for carrying the steps and connecting them to the piezoelectrically sensitive material; The cutting insert and tool according to claim 8, characterized by comprising: career.