An online measuring device for cutting area temperature during single-point diamond turning

Abstract

The present invention relates to the field of temperature measurement technology in ultra-precision machining processes, and in particular to an online temperature measurement device for a cutting area during a single-point diamond turning process, comprising a temperature-sensitive diamond tool, a tool housing, and a temperature acquisition circuit, wherein a conductive path is formed between the temperature-sensitive diamond tool and the temperature acquisition circuit; the temperature acquisition circuit acquires the voltage change of the temperature-sensitive diamond tool during the cutting process and converts it into a temperature signal; the temperature-sensitive diamond tool achieves diamond semiconductor modification through boron-hydrogen co-doping, and utilizes the inherent resistance of the semiconductorized diamond tool material to change with temperature to achieve the measurement of the temperature of the cutting area. The present invention can measure the online temperature of a quasi-cutting area at a micro-nano cutting scale with high sensitivity and high response speed, and the invention has extremely strong practicality and broad application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of temperature measurement in an ultra-precision machining process, and in particular to an online temperature measurement device for a cutting area in a single-point diamond turning process. Background Art

[0002] Single-point diamond turning has become an important means in the field of ultra-precision machining due to its advantages of high machining accuracy, good repeatability and high machining efficiency. It is widely used in the manufacturing process of optical free surfaces (lenses, mirrors, windows, laser elements), micro-nano structure surfaces (microlens arrays, microprism arrays, compound eye microstructure arrays), precision grinding tools, etc.

[0003] The cutting process is accompanied by complex thermal-mechanical coupling interactions. Cutting temperature is an important indicator for measuring cutting conditions such as surface size, shape accuracy, cutting chatter, tool wear, etc. By sensing the cutting temperature in real time, online monitoring of the cutting state can be effectively achieved, thereby ensuring and optimizing the machining process.

[0004] At present, the commonly used online cutting temperature measurement methods are thermocouple contact and infrared non-contact. Among them, when using infrared thermal imaging to measure cutting temperature, there will be problems such as chips blocking the cutting area, the cutting temperature cannot be continuously monitored, and the spatial resolution of the infrared instrument cannot measure the cutting area temperature at the micro-nano scale. When using thin film thermocouple contact temperature measurement, there are problems such as complex sensor film preparation process, poor coating quality stability, and difficulty in controlling the insulation between the film electrode and the tool body. In addition, there is a certain distance between the two electrodes of the thin film thermocouple and the position of the diamond tool tip, which cannot meet the online measurement requirements of the quasi-cutting area temperature in precision cutting.

[0005] During the single-point diamond ultra-precision cutting process, the temperature rise of the cutting micro-area at the micro-nano cutting scale is small and changes rapidly. Therefore, there are strict requirements for the temperature measurement of the cutting area with high sensitivity, fast response speed and high spatial resolution. Therefore, it is necessary to study a device suitable for online measurement of the cutting area temperature during the single-point diamond turning process. Summary of the invention

[0006] The object of the present invention is to provide a device for online measurement of the temperature of a cutting area during a single-point diamond turning process, which is conducive to online measurement of the temperature of the quasi-cutting area with high sensitivity and high response speed.

[0007] The purpose of the invention is achieved in this way:

[0008] An online temperature measurement device for a cutting area in a single-point diamond turning process, comprising a temperature-sensitive diamond tool, a tool housing, a temperature measurement circuit board and a power supply;

[0009] The front end of the tool housing is provided with a ceramic tool holder, on which two platinum electrodes are fixed; the temperature-sensitive diamond tool is arranged on the ceramic tool holder; and both ends of the temperature-sensitive diamond tool are respectively connected to corresponding platinum electrodes through conductive silver glue;

[0010] The temperature measurement circuit board is arranged inside the tool housing; a temperature acquisition circuit is arranged on the temperature measurement circuit board, which is connected to two platinum electrodes; the power supply supplies power to the temperature measurement circuit board, and a conductive path is formed between the temperature-sensitive diamond tool and the temperature acquisition circuit; the temperature acquisition circuit acquires the voltage change of the temperature-sensitive diamond tool during the cutting process and converts it into a temperature signal;

[0011] The temperature-sensitive diamond tool realizes diamond semiconductor modification through boron-hydrogen co-doping, and utilizes the change of inherent resistance of semiconductor diamond tool material with temperature law to realize the measurement of cutting area temperature.

[0012] Preferably, the temperature acquisition circuit includes

[0013] The constant current source module is connected to two platinum electrodes to provide a stable constant current source to the temperature-sensitive diamond tool;

[0014] The differential amplifier module amplifies the voltage signals of the two platinum electrodes;

[0015] The analog-to-digital conversion module converts the amplified voltage signal into a digital signal and transmits it to the processor module;

[0016] A processor module converts the received voltage signal into a temperature signal;

[0017] The power supply module provides voltage for each functional module.

[0018] Preferably, the constant current source module is supplied by an LM334 constant current source chip and an adjusting resistor, the output current value of the constant current source module is 1 μA, and a negative temperature coefficient diode is used to compensate for the temperature drift of the chip during the temperature measurement process.

[0019] Preferably, the differential amplifier circuit amplifies the voltage signal by 30 times.

[0020] Preferably, the processor module is an ESP32 processor, which transmits the temperature signal to the host computer via wireless Bluetooth, and the data transmission frequency is 50 Hz.

[0021] Preferably, the processor module converts the voltage signal and the temperature signal through a pre-calibrated temperature-resistance curve of the temperature-sensitive diamond tool.

[0022] Preferably, the temperature-sensitive diamond tool is connected to a first group of platinum electrodes fixed under the ceramic tool holder through conductive silver glue, and the temperature acquisition circuit is connected to a second group of platinum electrodes fixed on the ceramic tool shell through conductive silver wires. The contact between the first group of platinum electrodes and the second group of platinum electrodes realizes signal transmission between the temperature-sensitive diamond tool and the temperature acquisition circuit.

[0023] Preferably, the real-time resistance measurement of the temperature-sensitive diamond tool adopts a four-wire method to collect the voltage change at the end of the diamond tool during the cutting process.

[0024] Preferably, the temperature-sensitive diamond tool adopts a high-temperature and high-pressure temperature gradient method to carry out boron-hydrogen co-doping to synthesize diamond single crystals, and a carbon source, a modified catalyst, a seed crystal and a crystal bed are arranged in sequence from the high-temperature end to the low-temperature end of the cavity, the carbon source is high-purity graphite powder, and the modified catalyst is a mixture of LiAIH4 powder, amorphous boron powder, high-purity titanium powder and FeNiCo alloy catalyst; the LiAIH4 is used as a doped hydrogen source, and the doping mass ratio is 0.02wt.%-0.05wt.% of the carbon source; the high-purity amorphous boron powder is used as a doped boron source, and the doping mass ratio is 0.5wt.%-2.0wt.% of the carbon source; the high-purity titanium powder is used as a denitrifier, and the doping mass ratio is 0.7wt.%-1.0wt.% of the modified catalyst.

[0025] Compared with the prior art, the present invention has the following outstanding and beneficial technical effects:

[0026] The present invention overturns the existing temperature measurement technology based on discrete sensors, and realizes the cutting tool-measuring sensor coexistence from the perspective of tool material modification. It can measure the online temperature of the quasi-cutting area at the micro-nano cutting scale with high sensitivity and high response speed. The invention has extremely strong practicality and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the overall appearance of the present invention.

[0028] Figure 2 It is a principle block diagram of the present invention.

[0029] Figure 3 This is one of the installation schematic diagrams of the temperature-sensitive diamond tool of the present invention.

[0030] Figure 4 This is the second installation schematic diagram of the temperature-sensitive diamond tool of the present invention.

[0031] Figure 5 It is an exploded view of the components of the present invention.

[0032] Figure 6 It is a schematic diagram of each module of the temperature acquisition circuit of the present invention.

[0033] Figure 7 This is a schematic diagram of the equipment for preparing the temperature-sensitive diamond tool used in the present invention.

[0034] Figure 8 This is a photo of the boron hydride co-doped diamond single crystal sample after acid pickling and polishing.

[0035] Fig. 9 These are the Raman spectra results of boron-hydrogen co-doped diamond 100 and 111 crystal planes.

[0036] Fig.10 These are the infrared spectra results of boron-hydrogen co-doped diamond 100 and 111 crystal planes.

[0037] Fig.11 These are the calibration results of the thermal sensitive properties of boron-hydrogen co-doped diamond.

[0038] Fig.12 This is a photo of a diamond-ground ultra-precision machining tool.

[0039] Fig.13 This is the measurement result of the cutting edge radius of the diamond tool after sharpening under AFM.

[0040] In the figure: 1-temperature-sensitive diamond tool, 2-ceramic tool holder, 3-bolt, 4-nut, 5-tool lower shell, 6-tool shell, 7-hexagon socket screw, 8-tool upper shell, 9-conductive silver glue, 10-first group of platinum electrodes, 11-second group of platinum electrodes, 12-conductive silver wire, 13-fastening screw, 14-lithium battery, 15-temperature acquisition circuit, 16-copper stud, 17-constant current source module, 18-differential amplifier module, 19-analog-to-digital conversion module, 20-power supply module, 21-program download module, 22-processor module. DETAILED DESCRIPTION

[0041] The following are specific embodiments of the present invention, and the technical solutions of the present invention are further described in conjunction with the accompanying drawings, but the present invention is not limited to these embodiments.

[0042] An online temperature measurement device for a cutting area in a single-point diamond turning process, comprising a temperature-sensitive diamond tool, a tool housing, a temperature measurement circuit board and a power supply;

[0043] The front end of the tool housing is provided with a ceramic tool holder, on which two platinum electrodes are fixed; the temperature-sensitive diamond tool 1 is brazed on the ceramic tool holder as a cutting temperature sensor; both ends of the temperature-sensitive diamond tool are respectively connected to the first set of platinum electrodes on the ceramic tool holder through conductive silver glue; after the conductive silver glue solidifies, a layer of high-temperature resistant insulating glue is coated on it to prevent cutting fluid from spraying. Figure 1As shown, the ceramic tool holder is fixed to a reserved position of a tool housing 6 made of ceramic by bolts 3 and nuts 4;

[0044] The temperature measurement circuit board is arranged inside the tool housing; a temperature acquisition circuit is arranged on the temperature measurement circuit board, which is connected to two platinum electrodes; the power supply supplies power to the temperature measurement circuit board, and a conductive path is formed between the temperature-sensitive diamond tool and the temperature acquisition circuit; the temperature acquisition circuit acquires the voltage change of the temperature-sensitive diamond tool during the cutting process and converts it into a temperature signal;

[0045] When the ceramic knife holder is installed on the tool housing, the first set of platinum electrodes 10 on the ceramic knife holder are connected to the second set of platinum electrodes 11 on the ceramic tool housing 6 to form a conductive path. The temperature acquisition circuit is connected to the second set of platinum electrodes 11 fixed on the ceramic tool housing 6 through the conductive silver wire 12.

[0046] like Figure 1 The ceramic tool housing is made into an upper, middle and lower split structure (tool upper shell 8, tool shell 6, tool lower shell 5), which is convenient for debugging the temperature acquisition device and replacing the lithium battery. The three parts are fixed by hexagon socket screws 7 and set screws 13.

[0047] The temperature-sensitive diamond tool realizes diamond semiconductor modification through boron-hydrogen co-doping, and utilizes the change of inherent resistance of semiconductor diamond tool material with temperature law to realize the measurement of cutting area temperature.

[0048] Preferably, the temperature acquisition circuit includes

[0049] The constant current source module is connected to two platinum electrodes to provide a stable constant current source to the temperature-sensitive diamond tool;

[0050] The differential amplifier module amplifies the voltage signals of the two platinum electrodes;

[0051] The analog-to-digital conversion module converts the amplified voltage signal into a digital signal and transmits it to the processor module;

[0052] A processor module converts the received voltage signal into a temperature signal;

[0053] The power supply module provides voltage for each functional module. Figure 4 As shown, the power supply module 20 uses a Buck-Boost converter of model TPS63031 to convert the voltage output by the lithium battery 14 into a 3.3V voltage to power each active module; the lithium battery 14 has a capacity of 800mAh and a voltage of 3.7V, which can provide the system with continuous operation for 4 hours.

[0054] Preferably, the constant current source module is supplied by connecting an LM334 constant current source chip in parallel with an adjusting resistor. The output current value of the constant current source module is 1 μA. The LM334 chip itself has a positive temperature coefficient of +0.227 mV / °C, which will cause the output current to be unstable. The invention uses the negative temperature coefficient of the diode to prevent temperature drift.

[0055] Preferably, the differential amplifier module amplifies the voltage signal by a factor of 30. Since the voltage signal at the end of the diamond tool is very small, which is not conducive to analog-to-digital conversion, the differential amplifier circuit 18 is used to amplify the measured voltage signal at the end of the diamond tool.

[0056] Preferably, the processor module is an ESP32 processor, which transmits the temperature signal to the host computer via wireless Bluetooth, and the data transmission frequency is 50 Hz.

[0057] The temperature measurement principle of the device for online measurement of cutting area temperature is based on the thermal sensitivity of diamond after being doped with semiconductors. At this time, the diamond tool is regarded as a thermistor temperature sensor. Before measuring the cutting temperature, it is necessary to calibrate the thermistor curve of the diamond tool, that is, the temperature-resistance. During the cutting process, the temperature of the cutting area changes, and the resistance value of the diamond tool changes. After collecting the voltage at the end of the diamond tool at this time, the temperature value of the cutting area can be calculated according to the thermistor curve.

[0058] Preferably, the real-time resistance measurement of the temperature-sensitive diamond tool adopts a four-wire method to collect the voltage change at the end of the diamond tool during the cutting process.

[0059] This example also provides the installation and implementation process of the device and method.

[0060] (1) Installation of the temperature-sensitive diamond tool 1: The hexagonal bolt 1 passes through the ceramic tool holder 2 and the ceramic tool housing 6 respectively and is locked by the hexagonal nut 4 to ensure good contact between the ceramic tool holder 2 and the platinum electrodes 10 and 11 on the ceramic tool housing 6, and to ensure that the position of the ceramic tool holder 2 meets the angle requirements of the tool during cutting.

[0061] (2) Assembling the temperature acquisition circuit 15: The temperature acquisition circuit 15 is locked inside the ceramic tool housing 6 by four copper studs 16, and the lithium battery 14 is connected to the power supply end of the circuit board by a wire.

[0062] (3) Fixing the temperature measuring device to the machine tool. The lower shell of the device is reserved with six threaded holes for connection with the ultra-precision machine tool, which are locked with the machine tool by hexagonal screws to complete the positioning between the temperature measuring device and the machine tool.

[0063] (4) Cutting temperature test: The workpiece material is a PMMA (plexiglass) cylinder, and the processing parameters are: spindle speed 1000 r / min, feed rate 0.01 mm / r, and cutting depth 10 μm.

[0064] The temperature-sensitive diamond tool adopts a high-temperature and high-pressure temperature gradient method to perform boron-hydrogen co-doping to synthesize diamond single crystals. A carbon source 67, a modified catalyst 68, a seed crystal 69 and a crystal bed 70 are arranged in sequence from the high-temperature end to the low-temperature end of the cavity, wherein the carbon source is high-purity graphite powder, and the modified catalyst is a mixture of LiAIH4 powder, amorphous boron powder, high-purity titanium powder and FeNiCo alloy catalyst; if only FeNiCo alloy is used as a synthetic catalyst, the synthesized diamond is an insulator; on the basis of FeNiCo alloy, LiAIH4 powder, amorphous boron powder and high-purity titanium powder are added; the LiAIH4 is used as a doped hydrogen source, and the doping mass ratio is 0.02wt.%-0.05wt.% of the carbon source; the high-purity amorphous boron powder is used as a doped boron source, and the doping mass ratio is 0.5wt.%-2.0wt.% of the carbon source; the high-purity titanium powder is used as a denitrifying agent, and the doping mass ratio is 0.7wt.%-1.0wt.% of the modified catalyst.

[0065] The purity of high-purity titanium powder and high-purity graphite powder are both required to reach 99.99wt.%.

[0066] The doping mass ratio of the FeNiCo alloy catalyst is Fe:Ni:Co=65:30:5.

[0067] The doping mass ratio of LiAIH4 is 0.03wt.% of the carbon source; the doping mass ratio of the high-purity amorphous boron powder is 1.0wt.% of the carbon source; and the doping mass ratio of the high-purity titanium powder is 0.9wt.% of the modified catalyst.

[0068] The pressure inside the cavity is 5.0-5.5 GPa, and the center temperature inside the cavity is 1400-1500° C. In this embodiment, the center temperature inside the cavity is 1440° C.

[0069] When preparing the modified catalyst, amorphous boron powder, LiAIH4 powder and high-purity titanium powder with different mass fractions are mixed into FeNiCo alloy catalyst as required.

[0070] The cavity includes a magnesium oxide cup 64, which is located in the inner layer and can accommodate the carbon source 67, the modified catalyst 68, the seed crystal 69 and the crystal bed 70; a graphite heating tube 63, which is arranged around the outside of the magnesium oxide cup 64; dolomite 62, which is arranged around the graphite heating tube 63; and talc 61, which is arranged around the dolomite 62 to form the outer layer of the cavity. Steel caps 65 are arranged on both sides of the high-temperature end and the low-temperature end of the cavity, and the steel cap 65 is located on the outside of the dolomite 62. The magnesium oxide cup, dolomite and talc are for heat preservation and pressure maintenance, and the steel cap is for electrical conductivity. An alumina gasket 66 is arranged between the carbon source 67 and the inner wall of the magnesium oxide cup 64 on the high-temperature end side, which is used for heat transfer and electrical isolation between the heating component and the carbon source.

[0071] Diamonds are synthesized in a domestic hinged six-sided top-pressing device. In order to achieve the crystal size required for diamond tools, the diamond synthesis time is 46 hours. After diamond synthesis, it needs to be pickled and polished.

[0072] The synthesized boron-hydrogen co-doped diamond single crystal material was subjected to component testing, grinding property testing, and thermal property testing. The component testing was to evaluate the boron doping situation, and the grinding property testing was to evaluate whether the boron-hydrogen co-doped diamond single crystal could be ground to the cutting edge radius required for ultra-precision machining. The thermal property testing was to evaluate whether the material could be used as a temperature-sensitive material.

[0073] The boron-hydrogen co-doped diamond single crystal synthesized by the process method is as follows: Figure 8 As shown, the crystal geometric size is about 4mm×4mm×1mm, with a regular shape and good symmetry.

[0074] Raman spectroscopy was performed on the samples ( Fig. 9 ) and infrared spectroscopy ( Fig.10 ) test, the results show that the boron characteristic peaks are obvious on the 100 and 111 crystal planes of diamond.

[0075] The samples were tested for thermal sensitivity, and the results were as follows: Fig.11 As shown, the test results show that boron hydride co-doped diamond material has significant negative temperature coefficient thermal sensitivity in the temperature range of 298K-398K.

[0076] The samples were sharpened into ultra-precision machining tools ( Fig.12 ), the tool edge radius after testing and grinding is about 35nm ( Fig.13 ), good sharpening characteristics.

[0077] The diamond material synthesized by the scheme passed component testing, sharpening property testing, and thermal sensitivity testing, and it was finally determined that it can be used as a temperature-sensitive diamond tool material.

[0078] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An online temperature measurement device for cutting area during single-point diamond turning, characterized in that: It includes a temperature-sensitive diamond tool, a tool housing, a temperature measurement circuit board and a power supply; The front end of the tool housing is provided with a ceramic tool holder, on which two platinum electrodes are fixed; the temperature-sensitive diamond tool is brazed on the ceramic tool holder as a cutting temperature sensor; and both ends of the temperature-sensitive diamond tool are respectively connected to corresponding platinum electrodes through conductive silver glue; The temperature measurement circuit board is arranged inside the tool housing; a temperature acquisition circuit is arranged on the temperature measurement circuit board, which is connected to two platinum electrodes; the power supply supplies power to the temperature measurement circuit board, and a conductive path is formed between the temperature-sensitive diamond tool and the temperature acquisition circuit; the temperature acquisition circuit acquires the voltage change of the temperature-sensitive diamond tool during the cutting process and converts it into a temperature signal; The temperature-sensitive diamond tool is modified into a semiconductor by boron-hydrogen co-doping, and the temperature of the cutting area is measured by utilizing the change of the inherent resistance of the semiconductor diamond tool material with the temperature. The temperature-sensitive diamond tool is connected to a first group of platinum electrodes fixed under the ceramic tool holder through conductive silver glue, and the temperature acquisition circuit is connected to a second group of platinum electrodes fixed on the tool housing through conductive silver wires. The contact between the first group of platinum electrodes and the second group of platinum electrodes realizes signal transmission between the temperature-sensitive diamond tool and the temperature acquisition circuit.

2. The device for online measuring cutting area temperature during single-point diamond turning according to claim 1, characterized in that: The temperature acquisition circuit comprises: The constant current source module is connected to two platinum electrodes to provide a stable constant current source to the temperature-sensitive diamond tool; The differential amplifier module amplifies the voltage signals of the two platinum electrodes; The analog-to-digital conversion module converts the amplified voltage signal into a digital signal and transmits it to the processor module; A processor module converts the received voltage signal into a temperature signal; The power supply module provides voltage for each functional module.

3. The device for online measuring cutting area temperature during single-point diamond turning according to claim 2, characterized in that: The constant current source module is supplied by the LM334 constant current source chip and the regulating resistor. The output current value of the constant current source module is 1 μA. A negative temperature coefficient diode is used to compensate for the temperature drift of the chip during the temperature measurement process.

4. The device for online measuring cutting area temperature during single-point diamond turning according to claim 2, characterized in that: The differential amplifier module amplifies the voltage signal by 30 times.

5. The device for online measuring cutting zone temperature during single-point diamond turning according to claim 2, characterized in that: The processor module is an ESP32 processor, which transmits the temperature signal to the host computer via wireless Bluetooth, and the data transmission frequency is 50Hz.

6. The device for online measuring cutting zone temperature during single-point diamond turning according to claim 2, characterized in that: The processor module converts the voltage signal and the temperature signal through the pre-calibrated temperature-resistance curve of the temperature-sensitive diamond tool.

7. The device for online measuring cutting zone temperature during single-point diamond turning according to claim 1, characterized in that: The real-time resistance measurement of the temperature-sensitive diamond tool adopts a four-wire method to collect the voltage change at the end of the diamond tool during the cutting process.

8. The device for online measuring cutting zone temperature during single-point diamond turning according to claim 1, characterized in that: The temperature-sensitive diamond tool adopts a high-temperature and high-pressure temperature gradient method to perform boron-hydrogen co-doping to synthesize diamond single crystals. A carbon source, a modified catalyst, a seed crystal and a crystal bed are arranged in sequence from the high-temperature end to the low-temperature end of the cavity. The carbon source is high-purity graphite powder, and the modified catalyst is a mixture of LiAIH4 powder, amorphous boron powder, high-purity titanium powder and FeNiCo alloy catalyst; the LiAIH4 is used as a doped hydrogen source, and the doping mass ratio is 0.02wt.%-0.05wt.% of the carbon source; the amorphous boron powder is used as a doped boron source, and the doping mass ratio is 0.5wt.%-2.0wt.% of the carbon source; the high-purity titanium powder is used as a denitrifier, and the doping mass ratio is 0.7wt.%-1.0wt.% of the modified catalyst.

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