A drilling tool temperature distribution measurement system

Abstract

The present invention proposes a drilling tool temperature distribution measurement system, comprising a data acquisition module and a thermocouple calibration module for generating a calibration data set; the thermocouple calibration module comprises a heater and a thermocouple adjacent to a drill tip; the data acquisition module is connected to the thermocouple; the data acquisition module is electrically connected to a workpiece and a tool; when generating a calibration data set, the heater heats the drill tip and the thermocouple synchronously to synchronize the temperatures of the two, the data acquisition module collects drill tip temperature data via the thermocouple, and simultaneously collects thermoelectric potential data between the workpiece and the tool, and stores the temperature data and the corresponding thermoelectric potential difference data as a calibration data set; when measuring the tool temperature distribution during the drilling process, the measured thermoelectric potential between the tool and the workpiece is used to retrieve the corresponding temperature value from the calibration data set as a measurement value; the present invention can conveniently measure the temperature distribution state of the drilling tool.

Description

Technical Field

[0001] The invention relates to the field of measurement technology, in particular to a drilling tool temperature distribution measurement system. Background Art

[0002] During the material removal process, most of the required cutting mechanical energy is converted into thermal energy and transferred to the chips, workpieces and tools in the form of heat in different proportions. The increase in tool temperature caused by heat can easily cause softening of the tool and workpiece materials, instability of the metallographic structure of the machined surface of the workpiece, and other problems, thereby accelerating tool wear, reducing tool life and machined surface quality. Unlike right-angle cutting (turning, milling, etc.), during the drilling process, due to the different tool rake angles, blade inclination angles and cutting speeds at various points on the main cutting edge, the heat generated on the edge is uneven, and the chips that have carried a lot of heat will be confined in the spiral groove for a long time, causing the drilling temperature to be higher and more complicated than other processing processes under the same working conditions. Therefore, how to obtain the temperature distribution characteristics on the main cutting edge of the tool during the drilling process becomes the key to improving the tool life and the quality of the machined surface.

[0003] Contact temperature measurement technology and non-contact temperature measurement technology are the main methods of temperature measurement technology at present. Non-contact temperature measurement technology includes infrared temperature measurement method; contact temperature measurement technology includes thermocouple method. Among them, the disadvantages of infrared temperature measurement technology are: 1. The correction of emissivity is inaccurate; 2. It cannot measure the temperature of objects that are blocked or covered. Therefore, only contact measurement can accurately measure the temperature during drilling. Summary of the invention

[0004] The present invention provides a drilling tool temperature distribution measurement system, which can conveniently measure the temperature distribution state of the drilling tool.

[0005] The present invention adopts the following technical solutions.

[0006] A drilling tool temperature distribution measurement system can generate a calibration data set that associates temperature with thermoelectric potential when drilling a workpiece. The system includes a data acquisition module and a thermocouple calibration module for generating the calibration data set; the thermocouple calibration module includes a heater and a thermocouple adjacent to the drill tip; the data acquisition module is connected to the thermocouple; the data acquisition module is electrically connected to the workpiece and the tool; when generating the calibration data set, the heater heats the drill tip and the thermocouple synchronously to synchronize the temperatures of the two, the data acquisition module collects drill tip temperature data via the thermocouple, and simultaneously collects thermoelectric potential data between the workpiece and the tool, and stores the temperature data and the corresponding thermoelectric potential difference data as the calibration data set; when measuring the tool temperature distribution during the drilling process, the measured thermoelectric potential between the tool and the workpiece is used to retrieve the corresponding temperature value from the calibration data set as the measurement value.

[0007] The drilling tool includes a twist drill, a center drill or a pilot drill; the data collector is a high-precision potential measuring device that can amplify the collected potential;

[0008] The heater comprises a drilling tool, an insulating plate and a workpiece, and uses the heat generated by the drilling tool when drilling the workpiece to synchronously heat the drill tip and the thermocouple; the drilling tool is clamped by a tool fixture with a spindle; the workpiece is a metal workpiece, divided into an upper workpiece and a lower workpiece, and is clamped and fixed under the tool by a workbench fixture; the upper workpiece and the lower workpiece are separated by an insulating plate with a metal foil interlayer inside; the data acquisition module is connected to the workpiece and the tool respectively through two wires.

[0009] In the thermocouple calibration module, the end of the metal foil interlayer far away from the drilling work area is used as the cold end of the thermocouple, the cold end of the thermocouple is connected to a measuring end of a data collector, and the hot end is buried in the tool. The other measuring end of the data collector is connected to the tool through a brush to form a thermoelectric potential measurement circuit. The tool moves downward when cutting the workpiece. When the tool does not contact the metal foil interlayer, the thermoelectric potential measurement circuit is in an open circuit state.

[0010] The potential measurement loop uses a grounding structure to reduce noise interference in the measurement process; the part where the brush is connected to the tool is coated with the same material as the brush to avoid the generation of secondary thermoelectric potential.

[0011] When the tool contacts the metal foil interlayer, the thermoelectric potential measurement circuit is in a connection state and generates a thermoelectric potential difference. The data acquisition module synchronously collects the temperature signal measured by the thermocouple and the thermoelectric potential signal generated by the contact point to obtain a calibration curve between temperature and potential, and obtains the functional relationship between temperature T and thermoelectric potential U through quadratic polynomial fitting.

[0012] The insulating plate includes an upper insulating layer, a metal foil interlayer and a lower insulating layer; when the drill tip of the tool just starts to drill into the upper insulating layer, the axial force and torque borne by the tool start to increase from zero until the drill tip completely drills into the upper insulating layer material, and the axial force and torque borne by the tool reach a maximum value and remain stable. In this process, the thermoelectric potential is not generated because the cutting edge is not in contact with the metal foil interlayer; when the drill tip starts to drill out of the upper insulating layer and starts to contact the copper foil, the axial force and torque borne by the tool gradually decrease, and the thermoelectric potential in the thermoelectric potential measurement circuit starts to be generated, and a continuous signal is formed as the main cutting edge of the tool drills through the copper foil. The continuous signal is the thermoelectric potential signal generated along the main cutting edge. After the data acquisition module performs temperature calibration on the thermoelectric potential signal, the temperature distribution data on the tool edge during the drilling process can be obtained.

[0013] The measurement system also includes an experimental verification module for verifying the accuracy of the temperature measurement result of the system and the effectiveness of the method, and the verification process of the experimental verification module is to verify the calibration data set by drilling the workpiece with the drill bit of the experimental verification module;

[0014] The drill tip and outer edge of the tool of the experimental verification module are respectively provided with micro grooves for embedding thermocouples; to prevent the thermocouple from moving during the drilling process, when drilling is performed, the drill bit of the experimental verification module does not move, and the drilling process is performed by rotating the workpiece;

[0015] The micro groove is a micro groove with a diameter of 0.4 mm formed by electric spark machining; the thermocouple has a diameter of 0.18 mm and is fixed in the micro groove of the tool of the experimental verification module by thermal glue;

[0016] During the verification process, the calibration data set is used to measure the tool temperature during the drilling operation. The data acquisition module obtains the correspondence between the temperature and the thermoelectric potential measured by the thermocouple calibration module, and retrieves the temperature data corresponding to the thermoelectric potential measured by the data acquisition module from the calibration data set as the temperature during drilling, which is used as the verification value.

[0017] When the present invention is used to measure the temperature distribution of a drilling tool, the operation is relatively simple and convenient for an operator to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0019] Attached Figure 1 is a schematic diagram of the present invention;

[0020] Attached Figure 2 It is a schematic diagram of a tool drilling a workpiece;

[0021] Attached Figure 3 It is a corresponding schematic diagram of the axial force, torque and thermoelectric potential of the tool;

[0022] Attached Figure 4 It is a schematic diagram of the calibration curve of temperature and thermoelectric potential;

[0023] Attached Figure 5 It is a schematic diagram of the embedded position of the thermocouple on the tool;

[0024] In the figure: 1- tool; 2- data acquisition module; 3- upper workpiece; 4- lower workpiece; 5- upper insulating layer; 6- metal foil interlayer; 7- lower insulating layer;

[0025] 100 - Micro slots. DETAILED DESCRIPTION

[0026] As shown in the figure, a drilling tool temperature distribution measurement system can generate a calibration data set, and the system includes a data acquisition module 2 for generating a calibration data set and a thermocouple calibration module; the thermocouple calibration module includes a heater and a thermocouple adjacent to the drill tip; the data acquisition module is connected to the thermocouple; the data acquisition module is electrically connected to the workpiece and the tool; when generating the calibration data set, the heater heats the drill tip and the thermocouple synchronously to synchronize the temperatures of the two, the data acquisition module collects the drill tip temperature data through the thermocouple, and at the same time collects the thermoelectric potential data between the workpiece and the tool, and stores the temperature data and the corresponding thermoelectric potential difference data as the calibration data set; when measuring the tool temperature distribution during the drilling process, the measured thermoelectric potential between the tool and the workpiece is used to retrieve the corresponding temperature value from the calibration data set as the measurement value.

[0027] The tool 1 includes a twist drill, a center drill or a pilot drill; the data collector is a high-precision potential measuring device that can amplify the collected potential;

[0028] The heater includes a tool, an insulating plate and a workpiece, and uses the heat generated by the tool drilling the workpiece to synchronously heat the drill tip and the thermocouple; the tool is clamped by a tool fixture with a spindle; the workpiece is a metal workpiece, divided into an upper workpiece and a lower workpiece, and is clamped and fixed under the tool by a workbench fixture; the upper workpiece 3 and the lower workpiece 4 are separated by an insulating plate with a metal foil interlayer 5 inside; the data acquisition module is connected to the workpiece and the tool respectively through two wires.

[0029] In the thermocouple calibration module, the end of the metal foil interlayer far away from the drilling work area is used as the cold end of the thermocouple, the cold end of the thermocouple is connected to a measuring end of a data collector, and the hot end is buried in the tool. The other measuring end of the data collector is connected to the tool through a brush to form a thermoelectric potential measurement circuit. The tool moves downward when cutting the workpiece. When the tool does not contact the metal foil interlayer, the thermoelectric potential measurement circuit is in an open circuit state.

[0030] The potential measurement loop uses a grounding structure to reduce noise interference in the measurement process; the part where the brush is connected to the tool is coated with the same material as the brush to avoid the generation of secondary thermoelectric potential.

[0031] When the tool contacts the metal foil interlayer, the thermoelectric potential measurement circuit is in a connection state and generates a thermoelectric potential difference. The data acquisition module synchronously collects the temperature signal measured by the thermocouple and the thermoelectric potential signal generated by the contact point to obtain a calibration curve between temperature and potential, and obtains the functional relationship between temperature T and thermoelectric potential U through quadratic polynomial fitting.

[0032] The insulating plate includes an upper insulating layer 5, a metal foil interlayer 6 and a lower insulating layer 7; when the drill tip of the tool just starts to drill into the upper insulating layer, the axial force and torque borne by the tool start to increase from zero until the drill tip completely drills into the upper insulating layer material, and the axial force and torque borne by the tool reach a maximum value and remain stable. In this process, no thermoelectric potential is generated because the cutting edge is not in contact with the metal foil interlayer; when the drill tip starts to drill out of the upper insulating layer and starts to contact the copper foil, the axial force and torque borne by the tool gradually decrease, and the thermoelectric potential in the thermoelectric potential measurement circuit begins to be generated, and a continuous signal is formed as the main cutting edge of the tool drills through the copper foil. The continuous signal is the thermoelectric potential signal generated along the main cutting edge. After the data acquisition module performs temperature calibration on the thermoelectric potential signal, the temperature distribution data on the tool edge during the drilling process can be obtained.

[0033] The measurement system also includes an experimental verification module for verifying the accuracy of the temperature measurement result of the system and the effectiveness of the method, and the verification process of the experimental verification module is to verify the calibration data set by drilling the workpiece with the drill bit of the experimental verification module;

[0034] The drill tip and outer edge of the tool of the experimental verification module are respectively provided with micro grooves for embedding thermocouples; to prevent the thermocouple from moving during the drilling process, when drilling is performed, the drill bit of the experimental verification module does not move, and the drilling process is performed by rotating the workpiece;

[0035] The micro groove is a micro groove with a diameter of 0.4 mm formed by electric spark machining; the thermocouple has a diameter of 0.18 mm and is fixed in the micro groove of the tool of the experimental verification module by thermal glue;

[0036] During the verification process, the calibration data set is used to measure the tool temperature during the drilling operation. The data acquisition module obtains the correspondence between the temperature and the thermoelectric potential measured by the thermocouple calibration module, and retrieves the temperature data corresponding to the thermoelectric potential measured by the data acquisition module from the calibration data set as the temperature during drilling, which is used as the verification value.

[0037] Embodiment 1:

[0038] In this example, the measurement method of the measurement system is:

[0039] (1) The spindle fixture holds the drill bit, and the upper and lower workpieces are stacked on the workbench and clamped by the fixture. The upper and lower workpieces are separated by two insulating layers and a metal foil layer. The order from top to bottom is: upper workpiece, insulating layer, metal foil layer, insulating layer, lower workpiece. The insulating plate insulates the workpiece from the copper foil and forms a pair of thermocouples with the tool. The end of the copper foil away from the working area is used as the cold end of the thermocouple and connected to one pole of the data logger. The tool is connected to the other pole of the data logger through a brush to ensure that the circuit composed of the tool and the workpiece is open before the tool contacts the copper foil.

[0040] (2) Start drilling and calibrate the standard thermocouple to obtain the calibration curve between temperature and potential, then perform quadratic polynomial fitting to finally obtain the functional relationship between temperature and potential: T = Au 2 +Bu+C, where A and B are the coefficients of the quadratic term and the linear term respectively, and C is the constant term.

[0041] (3) In other drilling processes using the same drill bit and the same workpiece, the thermoelectric potential generated in the process is collected and substituted into the functional relationship between temperature and thermoelectric potential to calculate the temperature during the drilling process.

[0042] Verification of the effectiveness of the drilling tool temperature distribution measurement system: Micro grooves with a diameter of 0.4 mm were machined at the center and outer edge of the drill tip by electrospark machining, and then two OMEGA thermocouples with a diameter of 0.18 mm (model 5TC-TT-K-40-36) were buried in the micro grooves and fixed with thermal glue to prevent the thermocouples from moving during drilling and affecting the measurement results. The thermocouple near the drill center is marked as TC#1, and the thermocouple near the outer edge is marked as TC#2. The two thermocouples are about 0.5 mm away from the main cutting edge. To prevent the tool rotation from interfering with the thermocouple, the drill bit with embedded thermocouples is fixed on the workbench, the drill bit is kept stationary, and the drilling process is achieved by rotating the workpiece. To ensure the normal progress of the test, before drilling, the fixed drill bit and the machine tool spindle need to be tested for centering using a micrometer until the eccentricity is controlled within 3μm.

[0043] Embodiment 2:

[0044] Figure 2 The original signals of axial force, torque and thermoelectric potential generated when drilling aluminum alloy under the conditions of cutting speed of 60 m / min and feed speed of 0.3 mm / r are shown in the figure. As can be seen from the figure, when the drill tip just starts to drill into the upper material, the axial force and torque increase from zero until the drill tip completely drills into the material, reaching the maximum value and remaining stable. It is worth noting that in this process, the thermoelectric potential is not generated because the cutting edge does not contact the copper foil; when the drill tip starts to drill out of the upper plate and starts to contact the copper foil, the axial force and torque gradually decrease, and the thermoelectric potential begins to be generated, and a continuous signal is formed as the main cutting edge of the tool drills through the copper foil. This continuous signal is the thermoelectric potential signal generated along the main cutting edge. After temperature calibration, the temperature distribution on the edge is obtained.

[0045] In order to determine the relationship between the measured thermoelectric potential and temperature, a calibration test of the thermoelectric potential and temperature is carried out with the help of a standard thermocouple.

[0046] A standard OMEGA thermocouple (model 5TC-TT-K-40-36) is embedded in the drill bit, as close as possible to the contact point formed by the tool and the copper foil. The contact point and the thermocouple are heated simultaneously by a heater to ensure that the temperature measured by the thermocouple is consistent with the temperature at the contact point.

[0047] The Japanese YOKOGAWA (DL750) data acquisition system is used to simultaneously collect the temperature signal measured by the thermocouple and the thermoelectric potential signal generated by the contact point to obtain the calibration curve between temperature and potential, such as Figure 4 As shown, after fitting the quadratic polynomial, the temperature is obtained T Thermoelectric potential U The functional relationship between them is: .

[0048] Embodiment 3:

[0049] When embedding the hot end of the thermocouple in the drill bit, micro grooves with a diameter of 0.4 mm are machined at the center and outer edge of the drill tip by electrospark machining, and then two OMEGA thermocouples with a diameter of 0.18 mm (model 5TC-TT-K-40-36) are embedded in the micro grooves and fixed with thermal glue to prevent the thermocouples from moving during drilling and affecting the measurement results. The thermocouple near the drill center is marked as TC#1, and the thermocouple near the outer edge is marked as TC#2. The two thermocouples are about 0.5 mm away from the main cutting edge. In order to prevent the tool rotation from interfering with the thermocouple, the drill bit with the embedded thermocouple is fixed on the workbench, the drill bit is kept stationary, and the drilling process is realized by rotating the workpiece. To ensure the normal progress of the test, before drilling, the fixed drill bit and the machine tool spindle need to be tested for centering using a micrometer until the eccentricity is controlled within 3μm.

Claims

1. A drilling tool temperature distribution measurement system that can generate a calibration data set that correlates temperature and thermoelectric potential when drilling a workpiece, characterized by: The system comprises a data acquisition module and a thermocouple calibration module for generating a calibration data set; the thermocouple calibration module comprises a heater and a thermocouple adjacent to the drill tip; the data acquisition module is connected to the thermocouple; the data acquisition module is electrically connected to the workpiece and the tool; when generating the calibration data set, the heater heats the drill tip and the thermocouple synchronously to synchronize the temperatures of the two, the data acquisition module collects drill tip temperature data via the thermocouple, and simultaneously collects thermoelectric potential data between the workpiece and the tool, and stores the temperature data and the corresponding thermoelectric potential difference data as the calibration data set; when measuring the tool temperature distribution during the drilling process, the measured thermoelectric potential between the tool and the workpiece is used to retrieve the corresponding temperature value from the calibration data set as the measurement value; The heater comprises a tool, an insulating plate and a workpiece, and the heat generated by the tool when drilling the workpiece is used to heat the drill tip and the thermocouple synchronously; the tool is clamped by a tool fixture with a spindle; the workpiece is a metal workpiece, which is divided into an upper workpiece and a lower workpiece, and is clamped and fixed under the tool by a workbench fixture; the upper workpiece and the lower workpiece are separated by an insulating plate with a metal foil interlayer; the data acquisition module is connected to the workpiece and the tool respectively through two wires; In the thermocouple calibration module, the end of the metal foil interlayer far away from the drilling work area is used as the cold end of the thermocouple, the cold end of the thermocouple is connected to a measuring end of the data collector, the hot end is buried in the tool, and the other measuring end of the data collector is connected to the tool through a brush to form a thermoelectric potential measurement circuit. When the tool moves downward when cutting the workpiece, when the tool does not contact the metal foil interlayer, the thermoelectric potential measurement circuit is in an open circuit state; When the tool contacts the metal foil interlayer, the thermoelectric potential measurement circuit is in a pass state and generates a thermoelectric potential difference, and the data acquisition module synchronously collects the temperature signal measured by the thermocouple and the thermoelectric potential signal generated by the contact point to obtain a calibration curve between temperature and potential, and obtains a functional relationship between temperature T and thermoelectric potential U through quadratic polynomial fitting; The insulating plate includes an upper insulating layer, a metal foil interlayer and a lower insulating layer; when the drill tip of the tool just starts to drill into the upper insulating layer, the axial force and torque borne by the tool start to increase from zero until the drill tip completely drills into the upper insulating layer material, and the axial force and torque borne by the tool reach a maximum value and remain stable. In this process, the thermoelectric potential is not generated because the cutting edge is not in contact with the metal foil interlayer; when the drill tip starts to drill out of the upper insulating layer and starts to contact the copper foil, the axial force and torque borne by the tool gradually decrease, and the thermoelectric potential in the thermoelectric potential measurement circuit starts to be generated, and a continuous signal is formed as the main cutting edge of the tool drills through the copper foil. The continuous signal is the thermoelectric potential signal generated along the main cutting edge. After the data acquisition module performs temperature calibration on the thermoelectric potential signal, the temperature distribution data on the tool edge during the drilling process can be obtained.

2. A drilling tool temperature distribution measurement system according to claim 1, characterized in that: The tool comprises a twist drill, a center drill or a spot drill; the data collector is a high-precision potential measuring device that can amplify the collected potential.

3. A drilling tool temperature distribution measurement system according to claim 1, characterized in that: The potential measurement loop uses a grounding structure to reduce noise interference in the measurement process; the part where the brush is connected to the tool is coated with the same material as the brush to avoid the generation of secondary thermoelectric potential.

4. A drilling tool temperature distribution measurement system according to claim 1, characterized in that: The measurement system also includes an experimental verification module for verifying the accuracy of the system's temperature measurement results and the effectiveness of the method. The verification process of the experimental verification module is to verify the calibration data set by drilling a workpiece with a drill bit of the experimental verification module.

5. A drilling tool temperature distribution measurement system according to claim 4, characterized in that: The drill tip and outer edge of the tool of the experimental verification module are respectively provided with micro grooves for embedding thermocouples; to prevent the thermocouple from moving during the drilling process, when drilling is performed, the drill bit of the experimental verification module does not move, and the drilling process is performed by rotating the workpiece; The micro groove is a micro groove with a diameter of 0.4 mm formed by electric spark machining; the thermocouple has a diameter of 0.18 mm and is fixed in the micro groove of the tool of the experimental verification module by thermal glue.

6. A drilling tool temperature distribution measurement system according to claim 4, characterized in that: During the verification process, the calibration data set is used to measure the tool temperature during the drilling operation. The data acquisition module obtains the correspondence between the temperature and the thermoelectric potential measured by the thermocouple calibration module, and retrieves the temperature data corresponding to the thermoelectric potential measured by the data acquisition module from the calibration data set as the temperature during drilling, which is used as the verification value.

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