Device and method for determining force on a cutting tool insert

Abstract

A device for determining force on a cutting tool insert includes a cutting tool body configured to couple the cutting tool insert to a cutting machine, the cutting tool body defining a cavity therein. The device also includes a sensor arrangement disposed in the cavity and protruding therefrom. The sensor arrangement includes a loading body, a sensor comprising a sensor ink electrically isolated from the cutting tool body and the loading body, the sensor disposed between a bottom wall of the cavity and the loading body, and connectors coupled to the sensor ink and extending out of the cavity for connection to a data acquisition device to determine a force applied to the sensor. The cutting tool insert is coupled to the sensor arrangement and spaced from the cutting tool body such that forces on the cutting tool insert are transferred to the sensor through the loading body.

Description

DEVICE AND METHOD FOR DETERMINING FORCE ON A CUTTING TOOL INSERTFIELD OF TECHNOLOGY

[0001] The present disclosure relates to the determination of force on a cutting tool insert utilized in a manufacturing process.BACKGROUND

[0002] It is desirable to monitor the condition of cutting tool inserts utilized in manufacturing processes, for example, in the aerospace manufacturing industry, as wear of cutting tool inserts contributes to waste and damage of costly parts. Monitoring the cutting tool insert condition facilitates timely replacement of cutting tool inserts, reducing waste and inhibiting scraping and damaging of costly parts that are manufactured, as well as maintaining machine quality, and machining efficiency.

[0003] Direct real-time condition monitoring of cutting tool inserts in complex multi-axis machining processes, such as 5-axis milling, is difficult to accomplish due to the complex nature of these processes and equipment. In particular, complex movement of cutting tool inserts renders tool condition monitoring difficult.

[0004] Cutting forces generated during the manufacturing process have been found to generally correlate to tool condition, which includes tool wear and tool fracture. Direct measurement of the cutting forces at the location of the tool utilized in the machining process is difficult, however.

[0005] While dynamometers may be useful in determining forces, implementation of dynamometers in such cutting machines is costly and complex. As a result, indirect measurements have been utilized. For example, spindle motor feedback or acoustic emissions have been utilized as an indication of force or wear. Other attempts to determine force are intrusive to the cuttingtool body, reducing cutting tool body strength or rigidity and requiring calibration.

[0006] Improvements in determining force on cutting tool inserts are desirable.SUMMARY

[0007] According to one aspect of an embodiment, there is provided a device for determining force on a cutting tool insert of a cutting machine. The device includes a cutting tool body configured to couple the cutting tool insert to the cutting machine, the cutting tool body defining a cavity therein. The device also includes a sensor arrangement disposed in the cavity and protruding therefrom. The sensor arrangement includes a loading body, a sensor comprising a sensor ink electrically isolated from the cutting tool body and the loading body, the sensor disposed between a bottom wall of the cavity and the loading body, and connectors coupled to the sensor ink and extending out of the cavity for connection to a data acquisition device to determine a force applied to the sensor. The cutting tool insert is coupled to the sensor arrangement and spaced from the cutting tool body such that forces on the cutting tool insert are transferred to the sensor through the loading body.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Embodiments of the present disclosure will now be described, by way of example only, with reference to the attached figures, in which:

[0009] FIG. 1 is a sectional side view of a portion of a cutting tool body including a cutting tool insert in accordance with the prior art;

[0010] FIG. 2 is an illustration of cutting tool insert integrated in a milling tool;

[0011] FIG. 3 is a sectional side view of a portion of a cutting tool body including a cutting tool insert in accordance with an embodiment;

[0012] FIG. 4 is a sectional side view of a portion of a cutting tool body including a cutting tool insert in accordance with another embodiment;

[0013] FIG. 5 is a schematic view showing cutting tool body including a sensor coupled to a wireless transmitter in accordance with an aspect of an embodiment;

[0014] FIG. 6 shows a portion of the cutting tool of FIG. 5; and

[0015] FIG. 7 is a perspective view of a cutting tool body including a cutting tool insert in accordance with another embodiment.DETAILED DESCRIPTION

[0016] For simplicity and clarity of illustration, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. Numerous details are set forth to provide an understanding of the examples described herein. The examples may be practiced without these details. In other instances, well-known methods, procedures, and components are not described in detail to avoid obscuring the examples described. The description is not to be considered as limited to the scope of the examples described herein.

[0017] FIG. 1 is a sectional side view of a portion of a cutting tool including a cutting tool insert of the prior art. The cutting tool includes a cutting tool body 102 that couples a cutting tool insert 104 to the cutting machine, which may be milling machine or other cutting tool machine. The cutting tool insert 104 is releasably coupled to the cutting tool body 102 by a threaded screw fastener. The threaded screw fastener facilitates replacement of the cutting tool insert 104, for example, when worn.

[0018] As indicated, above, measurement of the cutting forces at the location of the tool utilized in the machining process is difficult but is useful as the cutting forces generally correlate to the condition of the cutting tool insert and provide an indicator of machining process issues.

[0019] FIG. 2 is an illustration of cutting tool insert integrated in a milling tool.

[0020] FIG. 3 shows a device 300 for determining force on a cutting tool insert of a cutting machine. The device includes the cutting tool body 302 configured to couple the cutting tool insert 304, also referred to as an insert, to the cutting machine. The cutting tool body 302 defines a cavity therein. A sensor arrangement 306 is disposed in the cavity and protrudes therefrom. The sensor arrangement 306 includes a loading body 308, a sensor 314 comprising a sensor ink electrically isolated from the cutting tool body 302 and the loading body 308. The sensor 314 is disposed between a bottom wall 316 of the cavity and the loading body 308. Isolated connectors 318 re coupled to the sensor 314 and extend out of the cavity for connection to a data acquisition device to determine a force applied to the sensor 314. The cutting tool insert 304 is connected to the sensor arrangement 306 and spaced from the cutting tool body 302 such that forces on the cutting tool insert 304 are transferred to the sensor 314 through the loading body 308.

[0021] In the example of FIG. 3, the device 300, including the cutting tool body 302 is utilized in a milling machine. The device may also be successfully implemented in a cutting tool body utilized in, for example, a lathe or other turning machine for determining force on a turning tool.

[0022] As indicated, the device 300 includes the cutting tool body 302. The cutting tool body 302 includes a cavity therein for receiving the sensor arrangement 306. The cavity is generally cylindrically shaped and includes a bottom wall 316 and cylindrical side wall 318. The bottom wall 316 is generally flat to provide a planar surface at the bottom of the cavity.

[0023] The sensor arrangement 306 is sized and shaped to closely fit in the cavity with very little or no clearance, for example, in a tight clearance fit. The sensor arrangement 306 includes a loading body 308 including a main body portion 320 and a stepped-down end 320 of smaller diameter than the main body portion 320. The main body portion 320 is generally cylindrically shaped to fit within the cavity. The loading body 308 may be, for example, a metal body ordisc that is slidable within the cavity. Thus, the tool body side 312 of the loading body 312 is smaller in diameter than the main body portion 320 of the loading body 308.

[0024] The sensor arrangement 306 also includes the sensor 314 which is a sensor ink such as a pressure-sensitive piezo-resistive ink. The ink thickness may be dependent on the range of measured load. In one example, the nominal thickness is 100 micrometers. The sensor 314 is electrically isolated from the cutting tool body 302 and the loading body 308 by electrical insulators including an electrically isolating substrate 324 on which the sensor ink is disposed and an electrically isolating layer 326. The electrically isolating substrate 324 is coupled to the bottom wall 316 of the cavity in the cutting tool body 302, for example, by an adhesive 328. The electrically isolating layer 326 is disposed between the sensor 314 and the loading body 308. The electrically isolating substrate 324 and the electrically isolating layer 326 may be the same material or may be made of different materials. For example, the electrically isolating substrate 324 and the electrically isolating layer 326 may be flexible substrates of a high performance plastic such as polyimide.

[0025] The electrically isolating layer 326, the sensor 314, and the electrically isolating substrate 324 as well as adhesive 328 generally cover the entire bottom wall 316 of the cavity. The stepped-down end 322, however, is smaller in diameter than the layers including the electrically isolating layer 326, the sensor 314, and the electrically isolating substrate 324 as well as adhesive 328. Thus, a recess is defined by the step-down in the loading body 308 as the recess is left between the main body portion 320 and the electrically isolating layer 326 disposed between the sensor 314 and the loading body 308.

[0026] A pair of shielded conductors 332, 334 including a first shielded conductor 332 and a second shielded conductor 334 are utilized for electrically connecting to the sensor 314. The first shielded conductor 332 is electrically coupled to one face of the sensor 314 and extends through the electricallyisolating substrate 324. The second shielded conductor 334 is electrically coupled to an opposing face of the sensor 314 and extends through the electrically isolating layer 326. Thus, the first shielded conductor 332 and the second shielded conductor 334 are coupled to opposing faces of the sensor 314 to provide electrical connection thereto.

[0027] The shielded conductors 332, 334 may be strips of conducting ink, such as silver conductors printed on opposing faces of the sensor 314. The first shielded conductor 332 and the second shielded conductor 334 extend from the opposing faces of the sensor 314 and along the cutting tool body 302 to a connection point. The shielded conductors 332, 334 are sandwiched between flexible substrate layers 336 such as polyimide, to electrically isolate the shielded conductors 332, 334 from each other and to electrically isolate the shielded conductors 332, 334 from the cutting tool body 302 and from other components of the device and of the cutting machine.

[0028] As indicated above, the recess 330 is defined by the step-down in the loading body 308 as the recess is left between the main body portion 320 and the electrically isolating layer 326 disposed between the sensor 314 and the loading body 308. Thermocouples 338 are disposed in the recess 330 for measurement of temperatures at or near the sensor 314. The thermocouples 338 may be K-type thermocouples that include separate thermocouple connectors extending from the thermocouples 338 or that are connected through conductors in the flexible substrate layers 336.

[0029] In addition to providing the recess 330 for the thermocouples 338, the step-down in the loading body 308 reduces the area of the loading body 308, i.e., the area of the tool body side 312 of the loading body 308, in contact with the electrically isolating layer 326, and reduces the area of the sensor 314 to which force is applied when force is transferred from the cutting tool insert 304 and through the loading body 308.

[0030] A further isolating layer 340 may be disposed on an outer surface 342 of the loading body 308, between the cutting tool insert 304 and the loading body 308. A hole 344 extends through the cutting tool insert 304 and the sensor arrangement 306, which includes the further isolating layer 340, the loading body 308, the electrically isolating layer 326, the sensor 314, and the electrically isolating substrate 324. The hole 344 is aligned with a screw-threaded hole 346 in the cutting tool body 302 for releasably attaching the cutting tool insert 304 to the cutting tool body 302. The hole 344 that extends through the sensor arrangement 306 is not screw threaded to facilitate movement of the loading body 308 and compression of the sensor 314.

[0031] The sensor arrangement 306 protrudes from the cavity in the cutting tool body 302 by less than 0.5mm. For example, the sensor arrangement 306 extends out of the cavity by about 0.2mm. Thus, the cavity is not sufficiently deep to receive the entire sensor arrangement 306 within the wall of the cavity.

[0032] The cutting tool insert 304 that is releasably connected to the cutting tool body 30 is seated adjacent to and abuts the further isolating layer 340 of the sensor arrangement 306. The cutting tool insert 304, however, is spaced from the closest face of the cutting tool body 302 as indicated above, for example by about 0.2mm. This space facilitates movement of the loading body 308, linearly along the cavity, in response to an applied force on the cutting tool insert 304.

[0033] When the cutting tool insert 304 is in use, forces on the cutting tool insert 304 are transferred to the sensor 314 through the loading body 308, thus, applying a compressive force to the sensor 314. The loading body 308 is moveable by a distance that is less than the distance that the sensor arrangement 306 protrudes out of the cavity. Thus, with a sensor arrangement 306 that protrudes out of the cavity by about 0.2mm, the loading body 308 may move, for example, up to about 0.15mm.

[0034] The total thickness of the sensor arrangement 306, including the adhesive, 328, the electrically isolating substrate 324, the sensor 314, theelectrically isolating layer 326, the loading body 308, and the further isolating layer 340, may be, for example, about 3.2mm. The thickness may be selected based on tool geometry and applied load. A thickness in the range of about 3.2mm to about 10mm may be successfully implemented and the thickness selected based on the applied load range. In the example of about 3.2mm, to protrude from the cavity by about 0.2mm, the total depth of the cavity in the cutting tool body 302 may be about 3.0mm.

[0035] With the stepped-down end 322 and resulting recess 330, the loading body 322 transfers force to about 70% or less of the sensor 314 and provides space at the recess 330 for the sensor 314 to expand into as a result of the applied force.

[0036] In the example described above with reference to FIG. 3, the sensor arrangement 306 and the electrical connections including the shielded conductors 332, 334 sandwiched between flexible substrate layers 336 as well as the thermocouple conductors, are a single or unitary piece. The sensor arrangement 306 is located in the cavity with the flexible connectors, including the conductors 332, 334 sandwiched between flexible substrate layers 336 and the thermocouple conductors, extending out of the cavity and along faces of the cutting tool body 302.

[0037] FIG. 4 illustrates an alternative device in which the sensor arrangement 406 is modular. Many of the features and elements of the device illustrated in FIG. 4 are similar to those described with reference to FIG. 3 and are therefore not described again herein. In the present example, however, a flexible connector 450 extends along faces of the cutting tool body and includes a connection point 452, which may be a pin connector. Similarly, the conductors 432, 434 sandwiched between flexible substrate layers 436 and the thermocouple conductors extending from the thermocouples 438 terminate at a complementary connection point 454. The complementary connection point 454 may be a complementary pin connector that couples to the connection point 452.Thus, the sensor arrangement 406 may be disconnected and removed, for example, for replacement, without removing the flexible connector 450.

[0038] FIG. 5 is a schematic view showing the device implemented in a cutting tool body, which in the present example is a milling tool body. In this example, the cutting tool insert 304 is coupled to the cutting tool body 302 and the sensor arrangement, similar to that illustrated in FIG. 3, is disposed in a cavity in the cutting tool body 302 such that forces on the cutting tool insert 304 are transferred to the sensor 314 (similar to that shown in FIG. 3). In the example of FIG. 3, the cutting tool insert was coupled to the cutting tool body utilizing a screw. In the present example, a wedge is utilized to mount the insert in place. The cutting tool insert is solid with no screw hole or holes. The conductors 332, 334 in the flexible substrate layers 336 and the thermocouple connectors extend up the cutting tool body 302 and are connected to a data acquisition board 602 that is located, for example, in the collet 604 coupled to the cutting tool body 302. The collet 604 houses the electrical components and batteries. The data acquisition board 602 is coupled to a wireless transmitter 606 to transmit the data from the sensor 314 (shown in FIG. 3) and the data from the thermocouples 338 (shown in FIG. 3) to a computing device 606. Although shown external to the collet 604 in the diagram, the wireless transmitter 606 may be disposed in the collet 604. The collet 604 is dynamically balanced to facilitate good performance and machine life.

[0039] In use, the cutting machine is utilized for cutting a workpiece and the device 300 is utilized in a method to determine force on the cutting tool insert 304 of the cutting machine. A difference in voltage on opposing sides of the sensor 314 is correlated to a force or applied pressure. Thus, a change in this voltage difference, as a result of a change in resistance of the sensor 314, indicates a change in the force applied. Signals from the sensor 314 are received at the data acquisition board 602 and the difference in voltage between the two faces of the sensor 314 is determined. In addition, signals from the thermocouples 338 are received at the data acquisition board 602. The voltageand signals from the thermocouples 338 are sent to the computing device 606. Using the difference in voltage and the signals from the thermocouples 338, the applied force is determined. The signals from the thermocouples 338 are utilized to correct the determined force value for temperature. Thus, heat that is transferred to the sensor arrangement and that affects the voltage difference, is compensated for, providing a more accurate determination of force. Temperature may also be utilized as an indicator for tool deterioration, which results in increase temperatures.

[0040] The force values determined may be utilized directly. Alternatively, the force determined may be calibrated by apply a known force to the tool insert. The known force may be utilized to calibrate to ensure that the force determined matches the applied force. Optionally, the force may be utilized to determine a corresponding tool condition.

[0041] The device shown and described herein may be successfully implemented for determining force in other cutting machines. FIG. 7 shows a perspective view of a device for determining the force on a cutting tool insert 702 of a turning machine. In the present example, the cutting tool body 704 is utilized in a lathe. The features of the device utilized in the turning machines are similar to those described herein above and are therefore not described again herein.

[0042] Advantageously, real-time determination of forces during machining is achieved utilizing very small scale sensors coupled to a data acquisition board and wireless transmitter on the tool holder using, for example, flexible, printed silver conductors. The device disclosed may be implemented in a cutting machine with only a very small cavity, for example, about 1.0mm deep in the cutting tool body to accommodate the sensor arrangement. The small cavity has little impact on cutting tool body strength and rigidity.

[0043] The forces determined may be directly utilized as an indicator of tool condition or may be correlated to tool condition. The use of the loading bodyreduces the transmission of shear forces to the sensor and facilitates the determination of normal cutting forces. Further, temperature may be utilized as an indicator of cutting tool insert wear and may be compensated for in the determination of force. The use of the flexible wiring connectors also facilitates flexibility in integration with various cutting tool geometries.

[0044] The scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.

Claims

What is claimed is:Claims1. A device for determining force on a cutting tool insert of a cutting machine, the device comprising: a cutting tool body configured to couple the cutting tool insert to the cutting machine, the cutting tool body defining a cavity therein; a sensor arrangement disposed in the cavity and protruding therefrom, the sensor arrangement including: a loading body; a sensor comprising a sensor ink electrically isolated from the cutting tool body and the loading body, the sensor disposed between a bottom wall of the cavity and the loading body; connectors coupled to the sensor ink and extending out of the cavity for connection to a data acquisition device to determine a force applied to the sensor; wherein the cutting tool insert is coupled to the sensor arrangement and spaced from the cutting tool body such that forces on the cutting tool insert are transferred to the sensor through the loading body.

2. The device according to claim 1, wherein the connectors comprise shielded conductors with a respective one of the shielded conductors coupled to each side of the sensor ink.

3. The device according to claim 2, wherein the shielded conductors comprise shielded conducting ink.

4. The device according to claim 3, wherein the shielded conductors comprise shielded printed silver conductors.

5. The device according to claim 1, wherein the sensor is electrically isolated from the cutting tool body by an electrically isolating substrate disposed between the cutting tool body and the loading body.

6. The device according to claim 5, wherein the electrically isolating substrate is coupled to the cutting tool body at the bottom wall of the cavity by an adhesive.

7. The device according to claim 5, wherein the sensor includes an electrically isolating layer disposed between the loading body and the sensor ink.

8. The device according to claim 7, wherein one or both of the electrically isolating substrate and the electrically isolating layer comprise high-performance plastic.

9. The device according to claim 7, wherein one or both of the electrically isolating substrate and the electrically isolating layer comprise polyimide.

10. The device according to claim 1, wherein the cavity comprises a generally cylindrical cavity and the loading body comprises a generally cylindrical loading body for transmitting normal forces to the sensor ink.

11. The device according to claim 10, wherein the loading body includes a reduced-diameter end defining a recess between the sensor and the loading body.

12. The device according to claim 11, comprising thermocouples disposed in the recess.

13. The device according to claim 11, wherein the loading body is configured to transfer the forces to 70% or less of the sensor ink.

14. The device according to claim 11, wherein the loading body and the recess are sized relative to the sensor ink to transfer the forces to 70% or less of the sensor ink.

15. The device according to claim 1, wherein the data acquisition device is disposed on the tool body.

16. The device according to claim 15, wherein the data acquisition device is coupled to a wireless transmitter for transmitting data therefrom.

17. The device according to claim 1, wherein the cutting machine comprises a milling machine and the cutting tool insert comprises and milling insert.

18. The device according to claim 1, wherein the cutting machine comprises a lathe or turning machine and the cutting tool insert comprises a turning tool.

19. The device according to claim 1, comprising an isolating layer disposed between the loading body and the cutting tool insert.

20. The device according to claim 1, wherein the sensor arrangement protrudes from the cavity by at least 0.2 mm.

21. The device according to claim 20, wherein the loading body is movable linearly up to 0.15 mm along the recess.

22. A method of determining force on the cutting tool insert of the cutting machine utilizing the device according to claim 12, comprising: receiving voltage signals from the sensor ink via the connectors; receiving temperature data from the thermocouples; utilizing the voltage signals, determining a corresponding force value and correcting the corresponding force value based on the temperature data to determine applied force to the sensor ink.

23. A device for use in a cutting tool body to determine force on a cutting tool insert of a cutting machine, the device comprising: a sensor arrangement including: a loading body; a sensor comprising a sensor ink disposed between electrically isolating layers, such that the sensor is disposed adjacent the loading body and electrically isolated therefrom; and connectors coupled to the sensor ink and extending along the loading body for connection to a data acquisition device to determine a force applied to the sensor; the sensor arrangement configured for coupling of the cutting tool insert to the cutting tool body such that forces on the cutting tool insert are transferred to the sensor through the loading body.

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