Polymer precursor ceramic thin film and cutting force sensor

Abstract

This invention belongs to the field of cutting force sensors, and relates to a polymer precursor ceramic thin film and a cutting force sensor. The preparation method of the polymer precursor ceramic thin film includes: 1) weighing PSN solution, SiCN powder, and TiSi2 powder in a mass ratio of 1:1:0.9-1.1, and mixing them to obtain a slurry; 2) stirring the slurry obtained in step 1) in a nitrogen atmosphere until uniformly mixed; 3) pouring the uniformly mixed slurry into a mold and leveling the slurry in the mold; 4) placing the mold containing the slurry in an oven to promote complete curing of the slurry; 5) placing the cured whole in a high-temperature furnace and pyrolyzing it under a nitrogen atmosphere to obtain the polymer precursor ceramic thin film. This invention provides a miniaturized polymer precursor ceramic thin film and a cutting force sensor with good sensing performance.

Description

Technical Field

[0001] This invention belongs to the field of cutting force sensors and relates to a polymer precursor ceramic thin film and a cutting force sensor. Background Technology

[0002] In machining, cutting force is generated between the tool and the workpiece and is an important indicator reflecting the cutting process. To achieve high-efficiency and high-quality production, it is usually necessary to monitor and control the cutting force in real time to avoid problems such as workpiece damage, material waste, and excessive tool wear caused by uncontrolled cutting force. This can extend tool life, optimize cutting processes, and is of great significance and practical value for reducing enterprise production costs and realizing intelligent manufacturing.

[0003] Currently, the most widely used cutting force sensors are mainly divided into two types: strain gauge and piezoelectric. However, the following problems still exist in the existing cutting force sensor designs: (1) The installation and response of the sensitive element need to be attached to the elastic strain structure or the embedded tool pad structure, which requires further design and processing of the tool, affecting the rigidity of the tool itself, reducing the versatility of the tool, and increasing the manufacturing cost of the sensor; (2) Due to the limitations of traditional sensitive materials, such as metal strain gauges and piezoelectric materials, the measurement accuracy is easily affected by cutting heat, which makes the sensor often installed far away from the cutting position of the tool tip, and unable to directly measure the cutting force. In the invention application with publication number CN 116394070A, a smart tool holder and system for real-time measurement of cutting force and cutting vibration based on piezoelectric thin film is disclosed. In this invention, the piezoelectric thin film is installed in a specially designed elastic strain structure, which cannot directly measure the cutting force, and at the same time increases the complexity of the sensor structure, resulting in increased manufacturing costs. The invention patent with authorization announcement number CN 107322368B innovatively proposes a cutting force measurement device based on a manganese copper alloy micro-nano sensing element, eliminating the elastic element in the traditional strain gauge cutting force sensor design and significantly reducing structural complexity. However, the sensor is encapsulated as a tool pad and embedded in the tool tip, affecting the tool's rigidity. Furthermore, due to the limitations of metal materials, the sensor needs to integrate signal amplification and filtering units on the tool holder, increasing the complexity of the sensor structure. The invention patent with authorization announcement number CN111906592B uses SiAlCO functional ceramic to replace the traditional metal strain gauge, significantly improving the sensor's measurement sensitivity and eliminating the need for subsequent signal amplification circuits and filtering units. However, using functional ceramic as the sensing material increases the size of the sensor's sensing element, correspondingly increasing the sensor's installation difficulty and causing greater damage to tool rigidity. On the other hand, while the sensor is encapsulated as a tool pad and embedded in the tool tip, allowing direct measurement of cutting force, the structural design limits it to measuring cutting force in only one direction.

[0004] Polymer precursor ceramics are formed by the pyrolysis of organic polymers within a certain temperature range. They not only possess high-temperature stability and wear resistance similar to traditional ceramics, but also exhibit excellent thermoresistivity and piezoresistive effects. As sensitive elements in cutting force sensors, they can significantly improve measurement sensitivity and sensor durability. Furthermore, liquid polymer precursors, as organic polymer materials, have good flowability and are easy to mold, making them widely applicable to various thin-film fabrication processes. Therefore, using common thin-film fabrication processes to in-situ mold polymer precursor ceramic films at the cutting tool tip, integrating the sensor's sensitive element with the cutting tool, can solve problems such as sensor installation and the inability to directly measure cutting forces, while also giving the sensor excellent sensitivity and stability. However, the ceramization process of polymer precursors is usually accompanied by significant volume shrinkage, leading to numerous cracks and detachment of the ceramic film. To address this issue, fillers are typically introduced into the polymer precursor to control the volume shrinkage during the ceramization process. Summary of the Invention

[0005] In order to solve the above-mentioned technical problems in the background art, the present invention provides a miniaturized polymer precursor ceramic thin film and a cutting force sensor with good sensing performance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a polymer precursor ceramic thin film, characterized in that: the method for preparing the polymer precursor ceramic thin film includes:

[0008] 1) Weigh PSN solution, SiCN powder and TiSi2 powder according to a mass ratio of 1:1:0.9 to 1.1, and mix them to obtain a slurry;

[0009] 2) Stir the slurry obtained in step 1) in a nitrogen atmosphere until it is evenly mixed;

[0010] 3) Pour the well-mixed slurry into the mold and spread the slurry evenly in the mold;

[0011] 4) Place the mold containing the slurry into the oven to allow the slurry to fully cure;

[0012] 5) The cured whole is placed in a high-temperature furnace and pyrolyzed under a nitrogen atmosphere to obtain a polymer precursor ceramic film.

[0013] As a preferred embodiment, the SiCN powder preparation method adopted in this invention is as follows: pure PSN solution is cured by holding at 120-140℃ for no less than 4 hours, and then pyrolyzed at 1000℃ for at least 4 hours to obtain SiCN ceramic. The SiCN bulk ceramic is ball-milled into powder by high-energy ball milling, and finally SiCN powder with a particle size of less than 45μm is screened through a 200-mesh sieve.

[0014] Preferably, in step 2), the stirring temperature is 100-110℃ and the stirring time is not less than 4 hours; in step 4), the oven temperature is 110℃ and the holding time is not less than 4 hours; in step 5), the pyrolysis temperature is 1000℃ and the pyrolysis time is not less than 4 hours; and the polymer precursor ceramic film is a SiCN / TiN composite film.

[0015] The polymer precursor ceramic film was prepared according to the preparation method of the polymer precursor ceramic film described above.

[0016] A cutting force monitoring sensitive element, characterized in that: the cutting force monitoring sensitive element comprises a bottom insulating layer, a top insulating layer, and a polymer precursor ceramic film prepared as described above; the bottom insulating layer, the polymer precursor ceramic film, and the top insulating layer are stacked sequentially; preferably, the structure and dimensions of the bottom insulating layer are completely the same as those of the top insulating layer; preferably, the area of ​​the bottom insulating layer is not less than the area of ​​the polymer precursor ceramic film; preferably, both the bottom insulating layer and the top insulating layer are SiO2 insulating layers.

[0017] A method for preparing a cutting force monitoring sensitive element, characterized in that: the method for preparing the cutting force monitoring sensitive element includes the following steps:

[0018] 1) Preparation of the underlying insulating layer;

[0019] 2) Prepare the polymer precursor ceramic film as previously prepared on the bottom insulating layer;

[0020] 3) Draw electrodes on the polymer precursor ceramic thin film;

[0021] 4) A top insulating layer is formed on the polymer precursor ceramic film to obtain a cutting force monitoring sensitive element; both the bottom insulating layer and the top insulating layer are SiO2 insulating layers.

[0022] As a preferred embodiment, the specific implementation of step 1) of the present invention is as follows: prepare a grid mold, drop PHPS solution into the grid mold, uniformly coat the PHPS solution in the grid area, place it in a high-temperature box furnace, keep it at 120°C for 1 hour in an air atmosphere, and then keep it at 600°C for 1 hour to obtain a SiO2 insulating layer.

[0023] Preferably, step 3) is implemented by drawing electrodes with silver paste at both ends of the polymer precursor ceramic film and extending the circuit from both ends of the electrodes. Preferably, the electrode size is 3mm × 1mm and the circuit size is 1mm wide.

[0024] Preferably, the specific implementation of step 4) is exactly the same as that of step 1).

[0025] A cutting force sensor based on the cutting force monitoring sensitive element described above is characterized in that: the cutting force monitoring sensitive element includes a first cutting force monitoring sensitive element, a second cutting force monitoring sensitive element, and a third cutting force monitoring sensitive element with identical structures; the first cutting force monitoring sensitive element, the second cutting force monitoring sensitive element, and the third cutting force monitoring sensitive element are respectively placed between the tool holder and the tool head; preferably, the first cutting force monitoring sensitive element, the second cutting force monitoring sensitive element, and the third cutting force monitoring sensitive element are respectively placed on three axial contact surfaces where the tool holder and the tool head contact each other.

[0026] A method for fabricating a cutting force sensor based on the cutting force sensor described above, characterized in that: the method for fabricating the cutting force sensor includes the following steps:

[0027] 1) Prepare the handle and the blade;

[0028] 2) Design the cutting force monitoring sensitive element according to the structure of the tool head and fabricate the cutting force monitoring sensitive element in situ on the surface of the tool head;

[0029] 3) After connecting the wire to the cutting force monitoring sensing element, assemble the tool head onto the end of the tool holder;

[0030] 4) Connect the wires from step 3) to the measuring circuit to complete the fabrication of the cutting force sensor.

[0031] As a preferred embodiment, the specific implementation of step 1) in this invention is as follows:

[0032] 1.1) Prepare the tool holder and tool head separately according to conventional production processes;

[0033] 1.2) A wire groove in the center of the tool holder;

[0034] 1.3) A slot for mounting the cutting head is provided at the front end of the tool holder; the structure and size of the slot are adapted to the cutting head;

[0035] The specific implementation method of step 2) is as follows:

[0036] 2.1) Select the three axial contact surfaces where the tool holder and the tool head come into contact;

[0037] 2.2) A first cutting force monitoring sensitive element, a second cutting force monitoring sensitive element, and a third cutting force monitoring sensitive element with identical structures and preparation methods are respectively set at corresponding positions on the cutting tool head; the first cutting force monitoring sensitive element is prepared in the same way as the cutting force monitoring sensitive element described above;

[0038] The specific implementation method of step 3) is as follows:

[0039] 3.1) Connect wires to the electrodes of the cutting force monitoring sensitive element;

[0040] 3.2) Pass the wire through the wire groove in the center of the tool holder;

[0041] 3.3) Push the cutter head into the slot at the end of the tool holder to complete the assembly of the cutter head and the tool holder;

[0042] The measurement circuit in step 4) is a Wheatstone bridge circuit.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The sensor provided by this invention uses a polymer precursor ceramic thin film as its sensitive element, employing a multilayer structure of "insulating layer-conductive layer-insulating layer." The total thickness of the film is approximately 180 μm, successfully meeting the requirement of a small cutting force sensor size. Furthermore, this polymer precursor ceramic thin film is directly fabricated and formed on the tool surface, achieving integration of the cutting force sensor and the tool, avoiding redundant structural design and subsequent installation, and significantly reducing manufacturing costs. The conductive layer in the sensitive element is composed of SiCN and TiN. The SiCN comprises a liquid-phase SiCN matrix formed by the high-temperature pyrolysis of SiCN powder and liquid polysilazane, while the TiN is formed by the reaction of TiSi2 and N2 in the original slurry. The reaction is accompanied by volume expansion, compensating for the volume shrinkage during the pyrolysis of liquid polysilazane and improving the film forming probability. In addition, the SiCN matrix and SiCN powder formed by the pyrolysis of liquid polysilazane in the conductive layer exhibit excellent piezoresistive effect. Simultaneously, the TiN conductive particles generated in situ in the conductive layer further enhance the conductivity of the film. The combined effect of these two factors enables the cutting force sensor to achieve high-sensitivity measurement. The cutting force sensor disclosed in this invention mainly comprises two parts: a SiCN / TiN layer of sensitive material and a SiO2 insulating layer. The resistance of the sensor changes with the magnitude of the applied cutting force, which is then converted into a voltage signal output through a connected circuit. This invention successfully fabricates a polymer precursor ceramic thin film cutting force sensor integrating the sensitive element and the cutting tool using a simple thin film fabrication process. This miniature sensor features low cost, small size, lightweight, multi-dimensional monitoring, and in-situ integration on the cutting tool. Simultaneously, the sensor exhibits excellent sensitivity and stability, demonstrating its potential for industrial processing applications. In this invention, TiSi2 and SiCN fillers are introduced for modulation. The TiSi2 and N2 react with in-situ generated TiN, which are conductive particles. This reduces the volume shrinkage of the precursor ceramicization while improving the thin film conductivity, further optimizing the sensing performance of the thin film, and ultimately fabricating a miniaturized, integrated triaxial cutting force sensor. Attached Figure Description

[0045] Figure 1 This is a schematic diagram showing the position of the triaxial cutting force sensor provided by the present invention;

[0046] Figure 2 This is a schematic diagram of the structure of the sensitive element used in this invention;

[0047] Figure 3 It is a stress distribution diagram of the cutting head under the action of main cutting force, feed force and depth of cut force respectively;

[0048] Figure 4 These are scanning electron microscope (SEM) images of the cross-section and surface of the SiCN / TiN composite film;

[0049] Figure 5 It refers to the change in the resistance of the sensitive element of the cutting force sensor when measuring the main cutting force;

[0050] Figure 6 This demonstrates the change in resistance of the sensing element of the cutting force sensor when measuring the feed force;

[0051] Figure 7 This demonstrates the change in resistance of the sensing element of the cutting force sensor when measuring the depth of cut force;

[0052] Figure 8 This is a measurement circuit diagram of the external tool of the sensing system;

[0053] in:

[0054] 1-Tool holder, 2-Tool tip, 3-Sensitive element, 4-SiO2 insulating layer, 5-SiCN / TiN composite conductive film, 6-Silver paste electrode on the surface of the conductive film. Figure 8 In the diagram, R1 is the resistance of the sensitive element, ΔR1 is the change in resistance of the sensitive element, R2, R3, and R4 are the same fixed resistors, E is the bridge excitation voltage, and U0 is the bridge output voltage. Detailed Implementation

[0055] This invention provides a method for preparing a polymer precursor ceramic thin film, comprising:

[0056] 1) Weigh PSN solution, SiCN powder, and TiSi2 powder according to a mass ratio of 1:1:0.9-1.1, and mix them to obtain a slurry. The SiCN powder is prepared by: solidifying pure PSN solution at 120-140℃ for at least 4 hours, then pyrolyzing it at 1000℃ for at least 4 hours to obtain SiCN ceramic. The SiCN bulk ceramic is then ball-milled into powder using a high-energy ball mill, and finally, SiCN powder with a particle size less than 45μm is screened through a 200-mesh sieve. The main function of the PSN solution is as a high-temperature binder. After pyrolysis, the PSN solution forms a liquid SiCN matrix. This liquid SiCN matrix is ​​uniformly distributed in the micropores of the SiCN powder and TiN particles, connecting the SiCN powder and TiN particles together to form a whole. It also forms numerous fine conductive networks among the conductive particles, ensuring the film has good sensing performance.

[0057] 2) Stir the slurry obtained in step 1) in a nitrogen atmosphere using a magnetic stirrer until it is evenly mixed; the stirring temperature is 100-110℃ and the stirring time is not less than 4 hours.

[0058] 3) Pour the well-mixed slurry into the mold and spread it evenly with a scraper to flatten the slurry in the mold and remove the excess; for example, the mold can be a 4mm×4mm square mold;

[0059] 4) Place the mold containing the slurry into the oven to allow the slurry to fully solidify; the oven temperature should be 110℃, and the holding time should be no less than 4 hours.

[0060] 5) The cured assembly is placed in a high-temperature furnace and pyrolyzed under a nitrogen atmosphere to obtain a polymer precursor ceramic film. The pyrolysis temperature is 1000℃, and the pyrolysis time is not less than 4 hours. The polymer precursor ceramic film is a SiCN / TiN composite film. For example, the polymer precursor ceramic film is square in shape, with dimensions of 4mm × 4mm and a thickness of approximately 65μm. TiN is mainly generated by the reaction of TiSi2 with nitrogen at high temperature, with the reaction formula: TiSi2 + N2 → TiN + Si. This reaction is accompanied by volume expansion, which effectively counteracts the volume shrinkage phenomenon of the PSN solution during pyrolysis. Simultaneously, the generated TiN is a conductive particle, which effectively improves the conductivity of the film.

[0061] In addition, the present invention also provides a polymer precursor ceramic thin film finally prepared according to the above method.

[0062] The present invention also provides a cutting force monitoring sensitive element, which includes a bottom insulating layer, a top insulating layer, and a polymer precursor ceramic film prepared as described above; the bottom insulating layer, the polymer precursor ceramic film, and the top insulating layer are stacked sequentially; preferably, the structure and dimensions of the bottom insulating layer are exactly the same as those of the top insulating layer; preferably, the area of ​​the bottom insulating layer is not less than the area of ​​the polymer precursor ceramic film; preferably, both the bottom insulating layer and the top insulating layer are SiO2 insulating layers.

[0063] The method for preparing the cutting force monitoring sensitive element provided by the present invention includes the following steps:

[0064] 1) Preparation of the bottom insulating layer: Specifically, a grid mold is prepared, and PHPS solution is dropped into the grid mold. The PHPS solution is then evenly coated onto the grid area using brushing or scraping processes. The mold is then placed in a high-temperature box furnace and held at 120°C for 1 hour in air to allow the PHPS solution on the tool surface to completely solidify. Finally, it is held at 600°C for 1 hour to obtain the SiO2 insulating layer. The SiO2 insulating layer serves to isolate the polymer precursor ceramic film from the tool holder surface, and also to improve the thermal compatibility between the polymer precursor ceramic film and the tool holder surface, enhance the film forming effect, and increase the bonding strength between the film and the tool holder. The SiO2 insulating layer is formed by the pyrolysis of perhydropolysilazane (PHPS). For example, the grid is a square grid with a size of 5mm × 5mm. During the preparation of the SiO2 insulating layer, the PHPS solution undergoes a hydrolysis reaction at a high temperature of 600℃. The Si-H bonds, Si-OH bonds, and Si-NH bonds in the solution break and form Si-O bonds. Si-O-Fe bonds are generated at the contact points with the tool surface, so that the SiO2 insulating layer and the tool surface are connected by chemical bonds.

[0065] 2) Prepare the polymer precursor ceramic film as previously prepared on the bottom insulating layer;

[0066] 3) Drawing electrodes on the polymer precursor ceramic film, specifically: drawing electrodes with silver paste at both ends of the upper surface of the polymer precursor ceramic film, and extending circuits from both ends of the electrodes. Preferably, the electrode size is 3mm × 1mm, and the circuit size is 1mm wide. For example, the size of the part of the circuit that overlaps with the film is 3mm long and 1mm wide, the circuit extension part at both ends is 1mm wide, and the length extends to the center of the tool holder. The electrodes are drawn with silver paste, and wires are welded at the electrodes.

[0067] 4) A top insulating layer is formed on a polymer precursor ceramic film to obtain a cutting force monitoring sensitive element; both the bottom and top insulating layers are SiO2 insulating layers; the preparation method of the top insulating layer is exactly the same as that of the bottom insulating layer.

[0068] Furthermore, this invention also provides a cutting force sensor based on the cutting force monitoring sensing element described above, comprising a first cutting force monitoring sensing element, a second cutting force monitoring sensing element, and a third cutting force monitoring sensing element with identical structures; the first, second, and third cutting force monitoring sensing elements are respectively placed between the tool holder and the tool head; preferably, the first, second, and third cutting force monitoring sensing elements are respectively placed on the three axial contact surfaces where the tool holder and the tool head contact each other. For example, the first, second, and third cutting force monitoring sensing elements between the tool head and the tool holder are all coated with perhydropolysilazane (PHPS) on the three axial surfaces of the tool holder, with a square shape and dimensions of 5mm × 5mm; then, a SiO2 insulating layer is obtained by firing at 600℃ for 1 hour, ultimately allowing the SiO2 insulating layer to be tightly bonded to the tool holder via Si-O-Fe chemical bonds.

[0069] The method for fabricating a cutting force sensor includes the following steps:

[0070] 1) Prepare the tool holder 1 and the tool head 2, specifically:

[0071] 1.1) According to conventional production processes Figure 1 and Figure 2 The tool holder 1 and the tool head 2 are fabricated separately.

[0072] 1.2) A wire groove in the center of the tool holder 1; for example, the center of the tool holder can be hollowed out to concentrate the wires at both ends of the sensitive element, and the hollow size is 10mm in diameter.

[0073] 1.3) A slot for mounting the cutter head 2 is provided at the front end of the tool holder 1; the structure and size of the slot are adapted to the cutter head 2;

[0074] 2) Based on the stress distribution of the cutting head 2 under cutting force, a cutting force monitoring sensitive element is designed and fabricated in situ on the surface of the cutting head 2. Specifically:

[0075] 2.1) Select the three axial contact surfaces where the tool holder 1 and the tool head 2 come into contact;

[0076] 2.2) A first cutting force monitoring sensitive element, a second cutting force monitoring sensitive element, and a third cutting force monitoring sensitive element with identical structure and preparation method are respectively set at corresponding positions on the cutter head 2; the first cutting force monitoring sensitive element is prepared in the same way as the cutting force monitoring sensitive element described above; the first cutting force monitoring sensitive element, the second cutting force monitoring sensitive element, and the third cutting force monitoring sensitive element measure the cutting force in that direction respectively.

[0077] The cutting force monitoring sensitive element includes a SiO2 insulating layer 4 and a SiCN / TiN composite conductive film 5. The film preparation process includes: batching, mixing, coating, thermosetting, and pyrolysis. The specific process steps are as follows: a 5mm × 5mm square grid is prepared at the tip of the tool holder. A small amount of PHPS solution is then dropped onto the edge of the square grid, and the droplet is evenly coated onto the square grid area using a scraper. The entire tool is then placed in a high-temperature box furnace and held at 120℃ for 1 hour in air, followed by holding at 600℃ for 1 hour to obtain the SiO2 insulating layer. Approximately 2ml of PSN solution is then taken, and SiCN powder is weighed at 100wt.% of the PSN solution mass, and TiSi2 powder is weighed at 110wt.% of the PSN solution mass. The prepared slurry was mixed evenly on a magnetic stirrer under a nitrogen atmosphere at 110℃ for 4 hours. After uniform mixing, a small amount of the mixed slurry was dripped onto the edge of a 4mm×4mm square grid mold on the SiO2 insulating layer of the cutting tool. The slurry was then evenly spread over the square grid area using a scraper. The entire cutting tool was then placed in a high-temperature box furnace and held at 110℃ for 4 hours. After that, it was pyrolyzed at 1000℃ under a nitrogen atmosphere for 4 hours to obtain a SiCN / TiN composite conductive film.

[0078] 3) After connecting the cutting force monitoring sensing element to the wire, assemble the tool head 2 onto the end of the tool holder 1, specifically:

[0079] 3.1) Connect wires to the electrodes of the cutting force monitoring sensitive element;

[0080] 3.2) Pass the wire through the wire groove in the center of the tool holder 1;

[0081] 3.3) Push the cutter head 2 into the empty space at the end of the handle 1 to complete the assembly of the cutter head 2 and the handle 1;

[0082] 4) Connect the wires from step 3) to the measurement circuit to complete the preparation of the cutting force sensor, and record the change in the output voltage of the measurement circuit due to the change in the magnitude of the cutting force. The measurement circuit is a Wheatstone bridge circuit, and the cutting force monitoring sensitive element is the changing resistor in the bridge. The output voltage generated in the bridge is mainly caused by the change in the resistance of the cutting force monitoring sensitive element, and the change in output voltage is positively correlated with the change in resistance.

[0083] The specific embodiments of the present invention will be described below with reference to the accompanying drawings. However, the following embodiments are only used to illustrate the present invention in detail and do not limit the scope of the present invention in any way.

[0084] A cutting force sensor, the overall structure of which is as follows: Figure 1 As shown, the tool includes a tool holder 1, a tool head 2, and three sensing elements 3. The tool head 2 is connected to the tool holder 1 and a clamp via a bolt structure. The three sensing elements 3 are installed in the space between the tip of the tool holder 1 and the tool head 2. The three sensing elements 3 are installed in different directions to measure the cutting force in different directions.

[0085] Figure 2 A schematic diagram of the sensitive element 3 is shown. (For example...) Figure 2 As shown, the sensitive element 3 adopts a three-layer structure in the form of "insulating layer-conductive layer-insulating layer". The structure mainly includes: two SiO2 insulating layers 4, a SiCN / TiN composite conductive film 5, and two electrodes 6 are drawn with silver paste at both ends of the conductive film 5. The overlapping part of the electrode 6 and the conductive film 5 has a size of 3mm×1mm.

[0086] Figure 3 This demonstrates the stress distribution of the cutting head under cutting force. Figure 3 (a) shows the stress distribution of the cutting head under the action of the main cutting force. Figure 3 (b) shows the stress distribution of the tool head under the action of feed force or cutting force. Figure 3 In the stress distribution diagram, positive stress values ​​indicate tensile stress, while negative stress values ​​indicate compressive stress. Therefore, the size and mounting location of the sensitive element can be determined based on the stress distribution diagram. The insulating layer is customized to 5mm × 5mm, the composite conductive film to 4mm × 4mm, and the film fabrication site is located in the stress concentration area.

[0087] Figure 4 Cross-sectional (a) and surface (b) views of the SiCN / TiN composite conductive film in the sensing element are shown. The cross-sectional view reveals that the composite conductive film is free of through cracks and has a relatively dense texture with no obvious pores. Furthermore, the TiN conductive particles are evenly distributed within the film. Based on the scale in the cross-sectional view, the overall thickness of the prepared composite conductive film can be estimated to be approximately 65 μm. The surface view shows that the SiCN / TiN composite conductive film is free of obvious cracks and pores, and the filler particles within the film are in close contact. This facilitates the formation of a conductive network, thereby enabling the conductive film to possess a certain piezoresistive coefficient through the permeation effect.

[0088] Figure 5 , Figure 6 as well as Figure 7This example demonstrates the response change of the resistance of the sensing element in the cutting force sensor as a result of the cutting force. The experiments included: the resistance response change of the sensing element when the peak cutting force was 10N, 20N, and 40N; the resistance response change of the sensing element when the peak cutting force was 40N and the loading rate was 0.5N / s, 1N / s, and 2N / s; and the resistance response change of the sensing element after 60 cycles when the peak cutting force was 40N and the loading rate was 1N / s.

[0089] Figure 5 This demonstrates the resistance change response of the sensing element in the sensor when measuring the main cutting force. From Figure 5 (a) and Figure 5 As can be seen in (b), the resistance of the sensitive element changes with the change of the main cutting force without any lag. At the same time, the amplitude of the resistance change of the sensitive element also increases significantly with the increase of the peak force of the main cutting force. Furthermore, the amplitude of the resistance change of the sensitive element can be stabilized within a small range when facing different loading rates, and the response is timely with no obvious delay. Figure 5 (c) and Figure 5 (d) shows the cyclic behavior of the sensitive element in the face of different main cutting forces and different loading rates. It can be seen from the figure that the cycle is stable and there is no obvious zero-point drift phenomenon. Figure 5 (e) shows the response of the sensing element to the main cutting force for 60 cycles, with a peak force of 40 N and a loading rate of 1 N / s. As can be seen from the figure, the resistance change amplitude of the sensing element remains stable within a small range throughout the entire cycle, and the resistance change response is timely with no significant delay.

[0090] Figure 6 and Figure 7 The figures show the resistance response changes of the sensing element group in the sensing system when facing cutting depth force and feed force. It can also be seen from the figures that when faced with cutting depth force and feed force, the sensing element group can produce different degrees of response to different magnitudes of force. At the same time, when the force remains constant and the loading rate of the force is different, it can maintain a stable resistance change amplitude and a stable response. It can also ensure a stable and fast response effect during long-term measurement.

[0091] Figure 8 The diagram shows the measurement circuit connected to the external part of the cutting force sensor. R1 is the resistance of the sensing element, ΔR1 is the change in the resistance of the sensing element, R2, R3, and R4 are the same fixed resistors, E is the excitation voltage of the bridge, and U0 is the output voltage of the bridge.

[0092] according to Figure 8 The circuit design shows that the relationship between U0 and ΔR1 is as follows: in As can be seen from the formula, changing the excitation voltage E of the bridge can change the slope of the relationship, thereby adjusting the measurement sensitivity of the sensing system.

[0093] The measurement principle is as follows: When a cutting force is applied to the cutting head, a minute strain is generated there. This strain is gradually transmitted through the cutting head to the sensing element, causing a similar minute strain in the sensing element. This alters the distance between the conductive particles inside the sensing element, disrupting the conductive network within the thin film and increasing the resistance of the sensing element. This change in the sensing element's resistance leads to a change in the output voltage of the measurement circuit. This establishes a correlation between the output voltage and the magnitude of the cutting force, thus completing the measurement of the cutting force.

[0094] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, any other modifications or equivalent substitutions made to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a polymer precursor ceramic thin film, characterized in that: The method for preparing the polymer precursor ceramic thin film includes: 1) Weigh PSN solution, SiCN powder and TiSi2 powder respectively according to a mass ratio of 1:1:0.9~1.1, and mix them to obtain a slurry; 2) Stir the slurry obtained in step 1) under a nitrogen atmosphere until it is evenly mixed; 3) Pour the well-mixed slurry into the mold and spread the slurry evenly in the mold; 4) Place the mold containing the slurry into the oven to allow the slurry to fully solidify; 5) The cured whole is placed in a high-temperature furnace and pyrolyzed under a nitrogen atmosphere to obtain a polymer precursor ceramic film; the pyrolysis temperature is 1000℃ and the pyrolysis time is not less than 4h. The polymer precursor ceramic film is a SiCN / TiN composite film.

2. The method for preparing polymer precursor ceramic thin films according to claim 1, characterized in that: The SiCN powder is prepared by: solidifying pure PSN solution at 120~140℃ for at least 4 hours, pyrolyzing it at 1000℃ for at least 4 hours to obtain SiCN ceramic, ball milling the SiCN bulk ceramic into powder using high-energy ball milling, and finally screening the SiCN powder with a particle size of less than 45μm through a 200-mesh sieve.

3. The method for preparing polymer precursor ceramic thin films according to claim 1 or 2, characterized in that: The stirring temperature in step 2) is 100~110℃ and the stirring time is not less than 4h; the oven temperature in step 4) is 110℃ and the heat preservation time is not less than 4h.

4. The polymer precursor ceramic film prepared according to the preparation method of the polymer precursor ceramic film as described in claim 3.

5. A cutting force monitoring sensitive element, characterized in that: The cutting force monitoring sensing element includes a bottom insulating layer, a top insulating layer, and... The polymer precursor ceramic film prepared according to claim 4; the bottom insulating layer, the polymer precursor ceramic film and the top insulating layer are stacked sequentially; the structure and size of the bottom insulating layer are exactly the same as those of the top insulating layer; the area of ​​the bottom insulating layer is not less than the area of ​​the polymer precursor ceramic film; both the bottom insulating layer and the top insulating layer are SiO2 insulating layers.

6. A method for preparing a cutting force monitoring sensitive element, characterized in that: The method for preparing the cutting force monitoring sensitive element includes the following steps: 1) Preparation of the underlying insulating layer; 2) Prepare the polymer precursor ceramic film as described in claim 4 on the bottom insulating layer; 3) Draw electrodes on the polymer precursor ceramic thin film; 4) A top insulating layer is formed on the polymer precursor ceramic film to obtain a cutting force monitoring sensitive element; both the bottom insulating layer and the top insulating layer are SiO2 insulating layers.

7. The method for preparing the cutting force monitoring sensitive element according to claim 6, characterized in that: The specific implementation method of step 1) is as follows: prepare a grid mold, drop PHPS solution into the grid mold, evenly coat the PHPS solution in the grid area, put it into a high-temperature box furnace, keep it at 120~140℃ for at least 1h in air atmosphere, and then keep it at 600~800℃ for at least 1h to obtain a SiO2 insulating layer. The specific implementation of step 3) is as follows: electrodes are drawn at both ends of the polymer precursor ceramic film with silver paste, and circuits are extended from both ends of the electrodes. The electrode size is 3mm×1mm, and the circuit size is 1mm wide. The specific implementation method of step 4) is exactly the same as that of step 1).

8. A cutting force sensor formed based on the cutting force monitoring sensitive element according to claim 5, characterized by: The cutting force monitoring sensing element includes a first cutting force monitoring sensing element, a second cutting force monitoring sensing element, and a third cutting force monitoring sensing element with identical structures; The first cutting force monitoring sensitive element, the second cutting force monitoring sensitive element, and the third cutting force monitoring sensitive element are respectively placed between the tool holder and the tool head; the first cutting force monitoring sensitive element, the second cutting force monitoring sensitive element, and the third cutting force monitoring sensitive element are respectively placed on the three axial contact surfaces where the tool holder and the tool head contact each other.

9. A method of manufacturing a cutting force sensor as claimed in claim 8, characterized in that: The method for preparing the cutting force sensor includes the following steps: 1) Prepare the handle (1) and the blade (2); 2) Design the cutting force monitoring sensitive element according to the structure of the cutter head (2) and prepare the cutting force monitoring sensitive element in situ on the surface of the cutter head (2); 3) After connecting the cutting force monitoring sensitive element to the wire, assemble the tool head (2) onto the end of the tool holder (1); 4) Connect the wires from step 3) to the measuring circuit to complete the fabrication of the cutting force sensor.

10. The method of claim 9, wherein: The specific implementation method of step 1) is as follows: 1.1) Prepare the handle (1) and the blade (2) according to conventional production processes; 1.2) A wire groove in the center of the tool holder (1); 1.3) A slot for mounting the cutting head (2) is provided at the front end of the tool holder (1); the structure and size of the slot are adapted to the cutting head (2); The specific implementation method of step 2) is as follows: 2.1) Select three axial contact surfaces where the tool holder (1) and the tool head (2) come into contact; 2.2) A first cutting force monitoring sensitive element, a second cutting force monitoring sensitive element, and a third cutting force monitoring sensitive element with identical structures and preparation methods are respectively set at corresponding positions on the cutting head (2); the preparation method of the first cutting force monitoring sensitive element is the preparation method of the cutting force monitoring sensitive element as described in claim 6; The specific implementation method of step 3) is as follows: 3.1) Connect wires to the electrodes of the cutting force monitoring sensitive element; 3.2) Pass the wire through the wire groove in the center of the tool holder (1); 3.3) Push the cutter head (2) into the empty space at the end of the handle (1) to complete the assembly of the cutter head (2) and the handle (1); The measurement circuit in step 4) is a Wheatstone bridge circuit.

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