Cutter sharpness testing method and device

Abstract

The invention discloses a cutter sharpness testing method and device, and the device comprises a servo motor which is used for providing a driving force; the screw transmission mechanism is connected with the servo motor and is used for converting the rotary motion of the servo motor into linear motion; the sliding seat transmission mechanism is connected with the screw rod transmission mechanism and the cutter and is used for driving the cutter to move along a straight line under the action of the screw rod transmission mechanism; the force signal acquisition unit is used for acquiring a force signal in the material cutting process of the cutter in real time; the programmable logic controller is used for controlling the motion state of the cutter; the upper computer data processing unit is connected with the force signal acquisition unit and is used for receiving and storing the force signal and generating a force-time curve and a power-time curve; and the cutter fixing mechanism is connected with the sliding seat transmission mechanism and is used for fixing a cutter.

Description

Technical Field

[0001] The present invention relates to the field of mechanical processing and detection technology, and in particular to a tool sharpness testing method and device based on real-time cutting force acquisition and data processing, which is used for quantitatively evaluating the sharpness of various industrial tools. Background Art

[0002] Existing tool sharpness testing technologies primarily rely on transient force signals generated when cutting into the material. These tests are typically performed using slow, short-stroke cutting of solid materials such as blocks, sheets, or wires. These traditional testing methods suffer from the following drawbacks: 1) The cutting force signal is prone to transient fluctuations during testing, resulting in unstable data; 2) The tool's performance under both low-speed and high-speed cutting conditions struggles to meet testing requirements; and 3) Existing testing systems have limitations in fixture versatility, mechanical rigidity, and data acquisition accuracy, making them difficult to meet the requirements for high-precision, continuous, and stable measurement. Therefore, it is necessary to provide a tool sharpness testing system with a rational structure, simple operation, and adaptability to a variety of testing conditions. Summary of the Invention

[0003] The main purpose of the present invention is to provide a tool sharpness testing method and device, which, through the collaboration of high-precision motion control and high-sensitivity force measurement, can achieve accurate identification of real-time, quantitative, and subtle changes in the cutting force, extrusion force, etc. of the tool being tested, thereby achieving high-precision dynamic quantitative evaluation of the tool sharpness.

[0004] A tool sharpness testing device comprises: a servo motor for providing driving force; a screw transmission mechanism connected to the servo motor and used to convert the rotational motion of the servo motor into linear motion; a slide transmission mechanism connected to the screw transmission mechanism and a tool and used to drive the tool to move in a straight line under the action of the screw transmission mechanism; a force signal acquisition unit for real-time acquisition of force signals during the tool cutting material; a programmable logic controller for controlling the motion state of the tool; a host computer data processing unit connected to the force signal acquisition unit and used to receive and store the force signal and generate a force-time curve and a power-time curve; and a tool fixing mechanism connected to the slide transmission mechanism and used to fix the tool.

[0005] Furthermore, the slide transmission mechanism includes a guide rail seat and an active slide and a driven slide slidably assembled on the guide rail seat, wherein the active slide is connected to the ball nut of the screw transmission mechanism, and the driven slide is connected to the tool.

[0006] Furthermore, the tool fixing mechanism is arranged on the driven slide and includes: a threaded tool holder sleeve structure with a flange fixing surface for fixing the straight-edged tool; a boat-shaped structure fixture, which utilizes a combination of a metal block and an elastic gasket to achieve uniform clamping of the sheet tool through a cross-symmetrical tightening method.

[0007] Furthermore, the force signal acquisition unit includes a force sensor connected between the active slide and the driven slide.

[0008] Furthermore, the programmable logic controller includes a forward cutting control unit and a reverse reset control unit, which are used to control the servo motor to rotate forward and reverse to drive the tool to perform forward cutting and reverse reset.

[0009] Furthermore, it also includes a safety protection unit for detecting whether the tool moves according to the preset stroke; the programmable logic controller also includes: an emergency stop control unit for issuing an emergency stop command to cut off the motor drive signal when it detects that the tool does not move according to the preset stroke.

[0010] Furthermore, the safety protection unit includes: a travel switch and a proximity sensor are provided at the starting and ending positions of the cutting stroke for detecting the tool position.

[0011] The tool sharpness testing device provided by the above technical solution of the present invention can bring the following beneficial effects: the servo motor of the present invention adopts a high-power AC servo motor, which is driven by a screw transmission mechanism (such as a ball screw) to convert the motor's rotational motion into linear motion, realizing the coordinated motion between the active slide and the driven slide of the slide transmission mechanism, thereby driving the tool to cut the material. During the cutting process, the cutting force signal is collected by the force sensor between the active slide and the driven slide, realizing the seamless coupling of "high-precision motion control" and "high-sensitivity force measurement". In addition, it can realize the real-time, quantitative, and precise evaluation of the measured object (such as the cutting force and extrusion force of the tool), obtain the generated force-time curve and power-time curve that can accurately reflect the sharpness of the tool, and help improve the accuracy and stability of tool sharpness detection. The system integrates a high-precision force sensor, a motion control module, and a data acquisition module. The power transmission process of the system can be divided into three levels: motion frequency conversion transmission path, mechanical transmission path, and power transmission path. First, the AC motor converts rotational motion into linear motion via a ball screw, driving the active and passive slides for feed motion. During this process, measuring elements such as tension sensors monitor the combined effects of mechanical parameters such as the active slide's thrust, the guideway's friction, and the axial force of rotation in real time. Secondly, based on the coupled effects of these mechanical parameters, the stress state during operation and its impact on motion accuracy and stability can be further evaluated.

[0012] In further technical solutions, comprehensive safety protection measures - including limit switches, proximity sensors and emergency stop buttons - can quickly shut down the machine in abnormal situations to ensure the safety of equipment and operators.

[0013] In further technical solutions, the replaceable multifunctional fixture is compatible with different types of tools such as straight-edged knives and sheet knives, and through the preset multiple cutting speeds, it can meet the needs of various working conditions such as low-speed fine cutting and high-speed mass production, and has a wide range of applicability.

[0014] The present invention also proposes a tool sharpness testing method, which is implemented by the aforementioned testing device. The testing method includes the following steps: controlling the servo motor to drive the tool movement through the initial reset instruction of the programmable logic controller to determine the starting position of the tool; controlling the servo motor to drive the tool to perform forward cutting and reverse reset movements in sequence through the cutting instruction of the programmable logic controller, and collecting the force signal generated during the cutting process in real time through the force signal acquisition unit; receiving the force signal through the host computer data processing unit to generate a force-time curve and a power-time curve.

[0015] Furthermore, the testing method also includes: before the cutting test, the force sensor of the force signal acquisition unit is first zeroed and calibrated through the zero adjustment potentiometer, and the amplification factor is adjusted according to the expected cutting force range to ensure that the amplitude of the collected force signal meets the processing requirements of the upper computer data processing unit.

[0016] Furthermore, a complete test cycle consists of forward cutting and reverse resetting, and a preset pause time is set between cycles to ensure data repeatability.

[0017] The tool sharpness testing method provided by the above-mentioned technical solution of the present invention can bring the following beneficial effects: before the test begins, automatic initial reset and precise positioning are used to ensure that each test starts from a uniform starting position; after the test begins, dynamic cutting force signals are collected in real time and transmitted to the host computer data processing unit to obtain force-time curves and power-time curves that can characterize sharpness, facilitating subsequent quantitative assessment of sharpness. Secondly, the programmable logic controller (PLC) realizes a highly automated testing process, eliminating the need for frequent human intervention throughout the cutting process, data collection, and safety monitoring, greatly improving test efficiency and data repeatability while reducing operational risks.

[0018] In a further technical solution, a high-precision miniature force sensor is used to collect the cutting force signal of the cutting process in real time at a higher sampling frequency, which can accurately capture the instantaneous force signal during the cutting process, thereby ensuring the high accuracy and stability of the test data.

[0019] In summary, the present invention not only performs outstandingly in terms of precision, automation, applicability, and real-time monitoring, but also has comprehensive safety guarantees, greatly improving the efficiency and reliability of industrial tool sharpness assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 FIG. 4 is a diagram showing the overall architecture of a tool sharpness testing system according to an embodiment of the present invention.

[0021] Figure 2 This is a kinematic transfer flow chart of a tool sharpness testing system according to an embodiment of the present invention.

[0022] Figure 3 Schematic diagram of the test platform structure in the tool sharpness testing system according to an embodiment of the present invention.

[0023] Figure 4 Schematic diagram of a system control and operation panel according to an embodiment of the present invention.

[0024] Figure 5 This is a flow chart of cutting force data collection and processing according to an embodiment of the present invention.

[0025] Figure 6 FIG. 1 is a schematic diagram of an active slide, a driven slide, and a force sensor according to an embodiment of the present invention.

[0026] Figure 7 Schematic diagram of a sheet tool clamping mechanism according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the accompanying drawings, specific implementation methods, and examples. The examples are provided for illustration only and are not intended to limit the scope of protection of the present invention.

[0028] An embodiment of the present invention provides a tool sharpness testing system that utilizes a high-power AC servo motor to drive a single-axis robot, achieves precise linear motion of the tool through ball screw transmission, and combines a micro-force sensor and PLC (programmable logic controller) control technology to achieve real-time acquisition and data processing of force signals generated during the cutting process. At the same time, a multifunctional fixture suitable for straight-edged knives and sheet-shaped tools is used to perform tests at different cutting speeds. Force-time and power-time curves are generated by a host computer to quantitatively evaluate tool sharpness.

[0029] Please refer to Figure 1The tool sharpness test system of the embodiment of the present invention includes a test platform, a PLC control unit, an operation panel and a host computer. The test platform is mainly the hardware part of the system, including components such as a servo motor, a ball screw transmission mechanism, a slide transmission mechanism, and a force signal acquisition unit (force sensor). Based on this, the embodiment of the present invention also provides a tool sharpness test device, which is included in the system. Please refer to Figure 1 and Figure 3 The test device includes: a servo motor 6 for providing driving force; a ball screw transmission mechanism, including a ball screw 2 and a stud nut 21, the ball screw 2 is connected to the servo motor 6, and is used to convert the rotational motion of the servo motor 6 into linear motion; a slide transmission mechanism, including a guide rail seat 7, an active slide 3 and a driven slide 8, the active slide 3 and the driven slide 8 are slidably installed on the guide rail seat 3, the active slide 3 is connected to the ball nut 21, and the driven slide 8 is connected to the tool 10; the ball screw transmission mechanism converts the rotational motion of the servo motor 6 into linear motion, and then drives the active slide 3 to slide linearly along the guide rail seat 7; a micro force sensor 9 (tension sensor) with a force signal acquisition unit is connected between the active slide 3 and the driven slide 8. ); when the active slide 3 moves linearly along the guide rail seat, the tension sensor drives the driven slide 8 to slide in coordination with the guide rail seat, thereby driving the tool to move linearly; a programmable logic controller (PLC control unit) is connected to the system operation panel and the servo motor, and controls the movement state of the tool (including initial reset, forward cutting, reverse reset, etc.) by controlling the operation of the motor (such as forward, reverse, emergency stop, etc.); a host computer data processing unit is configured in the host computer (such as a computer) and connected to the force signal acquisition unit to receive and store the collected force signal, generate a force-time curve and a power-time curve of the test process, and quantitatively evaluate the sharpness of the tool; in addition, a tool fixing mechanism is provided on the driven slide to fix the tool.

[0030] In some specific embodiments of the present invention, the servo motor 6 adopts a high-power AC servo motor, for example, an AC servo motor with a rated power of 750W and a rated speed of 3000rpm. The operation of the servo motor is controlled by a programmable logic controller (PLC control unit). The rotational motion is converted into linear motion through a ball screw drive, thereby achieving coordinated motion of the active slide and the driven slide, thereby driving the cutting tool to cut the test material, achieving precise positioning and stable cutting of the tool. The programmable logic controller (PLC control unit) controls the movement of the entire machine through a preset control program (including initial reset, forward rotation, reverse rotation, emergency stop, etc.), and implements safety protection through buttons, proximity sensors, travel switches, etc. In some exemplary embodiments, the speed of the servo motor driving the tool movement (i.e., cutting speed) is set to 11 speeds, ranging from 0.083m / s to 0.500m / s.

[0031] To achieve the aforementioned safety protection, the test device also includes a safety protection unit equipped with travel switches and proximity sensors at the start and end of the cutting stroke to detect tool position. If the tool detects that it has not moved within the preset travel range or has exceeded the travel range, an emergency stop command is issued to disconnect the motor drive signal, bringing the machine to an emergency halt.

[0032] refer to Figure 3 The output end of the servo motor 6 is connected to the ball screw 2 via a spring-loaded coupling 5. The ball screw 2 is positioned at each end by a deep groove ball bearing 1 and an angular contact ball bearing 4, respectively. The ball screw 2 is fixedly connected to the active slide 3 via a ball nut 21, driving the active slide 3 and ensuring smooth and precise motion transmission during both high and low speed cutting. In some exemplary embodiments, the pitch of the ball screw 2 is approximately 10 mm.

[0033] In some specific embodiments of the present invention, the force signal acquisition unit utilizes a high-precision micro-load sensor (or tension sensor) to acquire cutting force signals in real time during the cutting process at a high sampling frequency (e.g., 100 Hz). The force signal acquisition unit is also equipped with a signal conditioning module for digitizing the force signals output by the micro-load sensor and transmitting the processed data to a host computer for real-time curve plotting and data storage.

[0034] The embodiment of the present invention further provides a tool sharpness testing method, which is implemented based on the aforementioned testing device.

[0035] refer to Figure 2 , including the following process steps:

[0036] 1. Initial reset: Use the PLC control unit to control the operation of the servo motor, and combine mechanical structures such as proximity sensors and travel switches to achieve the starting position positioning of the tool, ensuring that each test starts from the same position;

[0037] 2. Cutting test: At a preset cutting speed (e.g., 11 speed levels ranging from 0.083 to 0.500 m / s), a single-axis robot drives the tool to perform cutting, while simultaneously collecting the force signals generated during the cutting process in real time.

[0038] 3. Data Processing: The collected cutting force signals are amplified, calibrated, and digitized to generate force-time and power-time curves, and steady-state cutting force plateau data is extracted. During the system's startup phase, the initial kinetic friction between the ball screw and ball nut, and between the active slide and guideway, gradually decreases as the system stabilizes. This causes transient spikes in the value at startup to be short-lived. Although the spikes are somewhat correlated with speed, their high randomness suggests that this parameter has no practical value for evaluating tool sharpness. However, the steady-state cutting force obtained during the curve plateau is of practical significance.

[0039] 4. Result evaluation: Based on the changing patterns of cutting force data at different speeds and combined with the mechanical dynamics model, the tool sharpness is quantitatively evaluated.

[0040] During the initial reset phase, the system first moves the tool in forward and reverse directions according to preset reset instructions until the precise starting position is determined by the travel switch and proximity sensor. Subsequently, a preset cutting speed (11 speed settings) is selected through the operation panel, and the system is started. The tool cuts at the set speed, while a micro-load sensor samples the force signals generated during the cutting process in real time at a sampling frequency of 100Hz. After data conversion and magnification calibration, the host computer software generates force-time and power-time curves in real time for subsequent quantitative assessment of tool sharpness.

[0041] In order to adapt to different types of knives, two types of fixtures are provided in this embodiment: (1) a fixture for straight-edged knives, such as Figure 6 As shown in FIG, (a) is a schematic diagram showing the connection between the tool and the slide transmission mechanism, and (b) is a cross-sectional view showing the connection relationship between the fixture and the driven slide. Figure 6 The fixture includes a threaded tool holder 20, a threaded tool holder sleeve 22, and an auxiliary handle 24 for disassembling and assembling the tool. The threaded tool holder sleeve 22 is connected and fixed to the driven slide by a nut 25, which contains a waist-shaped hole 26. The threaded tool holder 20 and the threaded tool holder sleeve 22 are connected by a fine thread 27. The fixture can achieve stable fixation of the tool 10 through the threaded tool holder sleeve 22 and the locking copper nut, and can adjust the tool screw-in depth (for example, the depth changes by 1mm for each rotation); (2) Fixtures for sheet tools, such as Figure 7As shown, (a) is a three-dimensional schematic diagram of the connection between the tool and the slide transmission mechanism, and (b) is a side view of the connection between the tool and the slide transmission mechanism. The fixture uses a metal block 72 and a boat-shaped fixture structure 71, and adopts a cross-symmetrical tightening method to achieve uniform clamping and angle adjustment of the blade, and can also conveniently adjust the front and rear angle of the blade and the cutting depth. The replaceable multifunctional tool fixture design is combined with the overall device structure to form a modular design, so that each fixture module can be freely replaced or adjusted according to different tool types and test requirements. At the same time, it works closely with the PLC control unit, servo motor drive mechanism and data acquisition system to achieve stable positioning and precise cutting of the tool in various test conditions, thereby further improving the flexibility and applicability of the test.

[0042] In addition, to ensure system safety, travel switches and proximity sensors are installed at the beginning and end of the cutting stroke, which can quickly stop the machine in the event of overtravel or abnormal conditions to protect the equipment and test materials.

[0043] During the system debugging phase, the tool cutting speed is adjusted by changing the motor input frequency, and the cutting force platform data at different speeds is recorded, thus providing sufficient experimental basis for tool sharpness evaluation.

[0044] refer to Figure 2 、 Figure 4 and Figure 5 The specific operation process of the testing method provided by a specific embodiment of the present invention is as follows:

[0045] Process 1: First, build the mechanical structure: An AC servo motor 6 with a rated power of 750W and a rated speed of 3000rpm is selected as the power source. A ball screw transmission mechanism is used to convert rotary motion into linear motion. The motor output is connected to the ball screw 2 via a spring-loaded coupling 5. The ball screw 2 is fixedly connected to the active slide 3 via a ball nut 21, ensuring smooth and precise motion transmission during both high and low speed cutting.

[0046] Process 2: After the mechanical structure is completed, the sensing and data acquisition system is constructed next. During the cutting process, this system uses a micro force sensor to collect the cutting force signal generated during the cutting process in real time. The selected force sensor is based on a resistive strain element and is equipped with a zero adjustment potentiometer and a magnification adjustment circuit for correcting and amplifying the initial signal. The amplified analog signal will be converted into a digital signal at a sampling frequency of 100Hz, and then transmitted to the host computer through a standard digital interface. The host computer is equipped with a data processing unit that can generate force-time curves and power-time curves in real time, which can be used for subsequent monitoring and analysis of the data collected during the test and for sharpness evaluation.

[0047] Process 3. On the basis of the completed construction of the sensing system, the system uses PLC as the core control unit to realize automatic control and safety protection of the entire tool cutting process. The PLC pre-sets the initial reset, forward rotation, reverse rotation and emergency stop programs to ensure that the tool can move forward and reverse in accordance with the preset program at startup until the accurate starting position is determined by the travel switch and proximity sensor, thereby ensuring that each test starts from the same position. In terms of safety protection, the system has installed travel switches and proximity sensors at the start and end of the cutting stroke. Once an overtravel or abnormal situation is detected, the PLC will immediately issue an emergency stop command to cut off the motor drive signal; in addition, there is an emergency stop button on the operation panel to facilitate the operator to quickly interrupt the test in an emergency to ensure the safety of the equipment and the operator.

[0048] Process 4: Before the formal test, the system should be fully debugged and calibrated. First, the operator needs to use the zero potentiometer to zero-calibrate the micro force sensor to ensure that the output of the force sensor is zero in the initial state; secondly, according to the force range generated during the actual cutting process, adjust the amplification factor to ensure that the collected signal amplitude meets the requirements of the host computer. After completing the sensor calibration, it is also necessary to verify the accuracy of the mechanical movement at different cutting speeds, observe the coordination between the tool stroke and the travel switch and proximity sensor, ensure that there is no looseness or abnormal vibration, and verify whether the motion accuracy of the overall system meets the design requirements by comparing the movement time at each speed with the expected parameters. After debugging is completed, the system can enter the formal testing phase to ensure the accuracy and stability of all data.

[0049] Process 5. After the above-mentioned mechanical, sensor and control systems are built, the system enters the cutting test phase. First, after starting the system, the PLC controls the tool to move forward and reverse according to the preset reset instructions until the travel switch is triggered to determine the exact starting position of the tool. Subsequently, the operator selects the preset cutting speed gear on the operation panel (this embodiment provides 11 gears, ranging from about 0.083m / s to 0.500m / s) and presses the "forward" button to start the cutting test. The tool starts cutting the material at the set speed, and the micro-force sensor collects the force signal generated during the cutting process in real time. The collected signal is amplified and digitized by the "data conversion and encoder" module, and uploaded to the host computer (calculation and storage). It is displayed in real time as a force-time and power-time curve by the host computer. The host computer is also equipped with the function of marking and exporting key data (such as exporting to CSV format data) to facilitate subsequent detailed analysis. Each forward cutting and reverse reset constitutes a complete test cycle. To ensure data stability, the system sets a preset pause between each cycle (such as a 4-second pause after the end of forward cutting and a 10-second pause after the end of return) to ensure that the data of multiple cycles have good repeatability. The tool sharpness is quantitatively evaluated through the steady-state cutting force platform data at different speeds combined with the mechanical dynamics model.

[0050] Process 6. This embodiment designs two types of tool fixing fixtures: For straight-edged tools, a threaded toolholder with a flange fixing surface is used. Two locking copper nuts adjust the screw-in depth (each rotation changes the cutting depth by 1mm) to achieve precise tool positioning. For sheet-shaped tools, a boat-shaped fixture is designed. This fixture utilizes a combination of metal blocks and elastic gaskets, achieving uniform clamping through a cross-symmetrical tightening method. It also allows for convenient adjustment of the blade's front-back angle and cutting depth. Furthermore, to ensure sufficient rigidity and low friction during the cutting process, all guide rails are made of ductile iron, with curved convex and concave rails providing guidance. The frame adopts an assembled structure with appropriate reinforcement ribs and square holes to ensure overall structural stability and reduce weight.

[0051] refer to Figure 2 In the entire process, the system kinematic transmission path is roughly as follows: AC servo motor drive → ball screw rotation forms a spiral linear action (converting motor rotational motion into linear motion) → active slide is driven to the right by ball screw → tension sensor is dragged by active slide → driven slide and the tool on it are dragged by tension sensor to perform cutting action.

[0052] Continue to refer Figure 2 、 Figure 4 and Figure 5 , combined with Figure 1 、 Figure 3The specific operation process of the testing method of the embodiment of the present invention is as follows:

[0053] Step 1: After connecting the system to the main power supply, first activate the operation panel (including the programming keyboard and display) to automatically initiate the PLC control unit's initialization routine. At this point, the system automatically performs an initial reset operation, with the tool moving in both forward and reverse directions. The tool's starting position is precisely determined under the monitoring of the travel switch and proximity sensor. This process ensures that the tool starts from a consistent initial position for each test, providing an accurate reference point and a stable operating environment for subsequent cutting tests.

[0054] Step 2: Before formal testing, the system is fully debugged and calibrated. First, the micro-force sensor is zero-calibrated using the zero-adjustment potentiometer to ensure that the sensor output is zero when unloaded. Next, the sensor's amplification factor is adjusted based on the expected cutting force range so that the collected signal amplitude meets the data acquisition requirements of the host computer. At the same time, all moving parts, including the tool fixture, slide, guide rails, and frame, must be inspected to ensure that all components are securely assembled, free of looseness or abnormal vibration, to ensure stable operation of the entire system during actual testing.

[0055] Step 3. After debugging is completed, the operator selects the preset cutting speed gear on the control panel according to the actual test requirements. This embodiment provides 11 speed gears, ranging from approximately 0.083 to 0.500 m / s, which can meet the different working conditions of low-speed fine cutting and high-speed mass production. At this time, the operator must also check all safety protection devices, including travel switches, proximity sensors, and emergency stop buttons, to ensure that they are in normal working condition to provide reliable protection for subsequent cutting operations.

[0056] Step 4. After completing the parameter settings, the operator presses the "Forward" button, and the system begins cutting according to the PLC's pre-set program. The tool moves in a straight line at the selected speed, cutting the test sample. Simultaneously, a micro-force sensor collects the cutting force signals generated by the material being cut in real time. The collected signals are amplified and digitized, then transmitted to the host computer at a sampling frequency of 100 Hz. Dedicated data processing software generates force-time and power-time curves in real time, which are dynamically displayed on the screen. This process not only enables real-time data monitoring but also ensures a complete record of data from each cutting test, providing a foundation for subsequent quantitative analysis.

[0057] Step 5: Each complete test cycle consists of a forward cut and a reverse reset. To ensure the continuity and stability of data acquisition, the system automatically pauses for approximately 4 seconds after the forward cut and approximately 10 seconds after the return stroke before entering the next test cycle. During this process, the host computer continuously stores all real-time collected data and supports exporting it to common formats such as CSV files to facilitate subsequent data analysis and tool sharpness assessment. Repeated testing over multiple cycles effectively improves data reliability and accuracy, providing a sufficient experimental basis for quantitative analysis.

[0058] Step 6. After all test cycles are complete, the operator stops the test via the control panel. The PLC immediately instructs the tool to return to its initial position according to the pre-set program, and the system automatically enters standby mode. At this point, all collected data is fully stored, allowing the operator to conduct detailed analysis, assess tool sharpness, and adjust relevant parameters based on the test results. At the same time, necessary maintenance and inspections are performed on the equipment to ensure the system is in optimal working condition before the next test.

[0059] Step 7: The result evaluation process is mainly based on the changing pattern of cutting force data at different speeds, combined with the mechanical dynamics model to quantitatively evaluate the tool sharpness. The basic principle is:

[0060] The blunt circular blade can be approximately regarded as a wedge with an opening angle of θ, a width of b, and a length of l in the fluid. For this wedge, we define a bluntness parameter δ

[0061]

[0062] For a straight-edged knife, when it is placed in a shear-thickening fluid and moves, the main force-bearing parts are the blunt edge and the side edge. In the process of this embodiment, the resistance F is calculated by referring to the ITTC model and the Holtrop-Mennen model for calculating the hull resistance. T Mainly due to friction resistance F F and pressure resistance F P The fluid flowing on the blunt edge surface generates viscous friction resistance F. f The influencing factors include surface roughness, fluid viscosity and density, flow velocity and flow state, etc. The physical shape of the blunt edge causes fluid flow obstruction, which is the pressure resistance F. P , mainly related to the sharpness of the tool.

[0063] F t =F f +F p

[0064] Under microscopic observation, the cutting edge of the tool can be seen to have a blunt rounded edge. During force analysis, the tool is subjected to resistance perpendicular to the incoming flow direction and friction tangential to the side cutting edge surface. In order to facilitate modeling and calculation, this blunt arc is projected in the direction perpendicular to the incoming flow and the side cutting edge, and simplified into a trapezoid fitted by three line segments: there is a blunt round plane at the front end, and the two sides are parallel to the side cutting edge. The difference is that the shear rate near the blade is very large, while the shear rate on the side cutting edge is small. If a non-Newtonian fluid model is used, it can be considered that the boundary layer of the tool tip is extremely thin and the shear rate tends to infinity, while the tool wedge angle is small and the shear rate on the tool side cutting edge is similar to that of a flat plate flow. In order to accurately express the shear thickening characteristics of the test fluid, the cross model is used, which is suitable for describing fluid types whose viscosity increases significantly at higher shear rates. The default apparent viscosity at the tool tip is η ∞ , the shear rate distribution on the wedge surface is usually expressed as

[0065]

[0066] Among them, U r is the reference velocity, representing the characteristic velocity at a given position x; φ′(η) is the derivative of the similarity solution, reflecting the velocity distribution in the boundary layer; δ is the boundary layer thickness. The boundary layer thickness formula for shear thickening fluid on the wedge surface using the cross model is:

[0067]

[0068] Where C is a constant that depends on the fluid and flow conditions.

[0069] The angle between the cutting edge and the direction of movement is called the angle of attack φ = 82.5°. When the cutting edge of the tool moves in the fluid at a certain cutting angle, the relative speed of the fluid relative to the cutting edge is the cutting edge velocity vector and the fluid velocity vector When the fluid is at rest, the velocity of the cutting edge relative to the fluid is divided into a velocity component v perpendicular to the cutting edge direction. tool_n and the velocity component v along the cutting edge direction tool_t

[0070] v tool_n =v tool sinφ,v tool_t =v tool cosφ

[0071] Viscous friction resistance F of the blade f It consists of two parts: the viscous friction resistance F of the tool side edge wedge surface f1 Viscous friction resistance F between the blade and the blunt edge f2 And the viscous friction resistance F of the blade surface along the cutting edgef3 Viscous friction resistance F f Usually the wall shear stress τ w and frontal area A eff related

[0072]

[0073] The wedge-shaped object is placed at an inclination angle φ relative to the flow direction. If the tool local coordinate system x'y'z' is transformed into the global rectangular coordinate system xyz:

[0074]

[0075] In the global rectangular coordinate system xyz, x refers to the flow direction, y refers to the tool length direction, and z refers to the tool thickness direction. For the frontal area integral, the local coordinate system is used, the position vector r, and the area element dA are expressed as

[0076]

[0077] The position vector r is expressed in the coordinate system as

[0078] r(x',y',z')=(x sinφ+y cosφ,x cosφ+y sinφ,z)

[0079] Calculate the partial derivatives of the position vector r with respect to x and z respectively:

[0080]

[0081] The effective length of the blade that is wetted is l, and the vertical distance from the tip of the blade to the water surface is h:

[0082] h=l sinφ

[0083] The thickness of the blade side is b, the distance from the blade to the thickest part of the side is c, and the top angle of the wedge opening formed by the two side blades is θ:

[0084]

[0085] d represents the width of the cutting edge plane of the tool

[0086]

[0087] Therefore, the frontal area of ​​the tool side edge A side_eff Value:

[0088]

[0089] Wall shear stress τ w Often described as:

[0090]

[0091] Among them, the x direction represents the incoming flow direction, and the y direction is perpendicular to the incoming flow direction.

[0092] Describes the two-dimensional steady-state incompressible viscous fluid flow and analyzes the two-dimensional flow on the xOz plane. The governing equations include the continuity equation to ensure mass conservation.

[0093]

[0094] and the Navier-Stokes equations that guarantee conservation of momentum

[0095]

[0096] Among them, v is the velocity field, p is the pressure field, and f is the body force.

[0097] For non-Newtonian fluids, μ eff is the effective viscosity, which is also the apparent viscosity η of the non-Newtonian fluid a For flat plate flow, the Reynolds number is calculated as:

[0098]

[0099] Therefore, the Reynolds number of non-Newtonian fluid is suitable for laminar flow analysis. For low Reynolds number fluid, inertial force can be ignored. For the steady-state process of the tool moving at a constant speed in a static fluid, it can be approximately regarded as the flow of a uniform fluid passing through the tool surface. For steady-state incompressible fluid, the equation is further simplified to

[0100]

[0101] The Navier-Stokes equations in the x- and z-directions are expanded as follows:

[0102]

[0103] In order to satisfy the continuity equation, the stream function ψ is introduced and the velocity component can be expressed as

[0104]

[0105] In this chapter, the blunt radius of the cutting edge forms a stagnation point in the fluid, causing the flow characteristics to be related to the sharpness. Different classical fluid motion continuity equations are used to solve the problem in different regions. The Falkner-Skan equation is used to describe the main area of ​​the tool side edge, and the Hiemenz equation is used to describe the stagnation area of ​​the blunt part. The Falkner-Skan equation is used to describe the boundary layer flow of laminar flow with pressure gradient.

[0106] f”′+ff”+β[1-(f′) 2 ]=0

[0107] Boundary conditions

[0108]

[0109] Where f(η) is the similarity variable, which is the dimensionless stream function distribution, f′=df / dη, f′'=d 2 f / dη 2 , f′′′=d 3 f / dη 3 , η is a similarity variable, different from the viscosity parameter of non-Newtonian fluid, and the reference system is consistent with the previous global rectangular coordinate system

[0110]

[0111] stream function ψ

[0112]

[0113] Velocity component

[0114] u=U e (x)f'(η)

[0115]

[0116] For wedge-shaped objects such as tool edges, the external flow velocity U e (x) There is a pressure gradient, which gradually increases along the direction of the fluid.

[0117]

[0118] In order to introduce x0 dimensionlessly, the value of x0 is usually taken as 1, in which the total length c' of the wedge is taken as the characteristic length, which represents the ratio of the position x to the reference length x0.

[0119] U0=v tool_n , x0=c'

[0120] At this time, the wedge opening angle θ = 35°, and the dimensionless parameters β and m are calculated.

[0121]

[0122] Therefore, the external flow velocity U e (x), which is the reference speed U r Simplified to

[0123]

[0124] Where β is the pressure gradient parameter and m is the external velocity distribution index. w

[0125]

[0126] For non-Newtonian fluids, the dynamic viscosity μ and the apparent viscosity η a

[0127]

[0128] Using the cross model, the relationship between apparent viscosity and shear rate is derived from the formula

[0129]

[0130] The f′(η) in the above formula needs to be calculated using numerical methods.

[0131] The wall shear stress is obtained by integrating the wall shear stress in the flow direction and the tool depth direction.

[0132]

[0133] The distance from the blade to the thickest part of the side cutting edge after grinding is c'. In fact, b>>r, so c' can be approximated as c for calculation. Using the data table calculated by numerical method and the value of m, f″1(0)≈0.4751 is calculated by linear interpolation. The side cutting edge friction resistance F f1 Simplified to

[0134]

[0135] For the side of the blade, the viscous friction resistance F f2_1 Follow the calculation formula of the side edge

[0136]

[0137] For the stagnation point area of ​​the blunt part, there is an obvious pressure gradient. The fluid is divided at the stagnation point. The front end of the blunt part of the blade is approximated as a flat plate. At this time, the flat plate part θ is 180°, and the Hiemenz equation of the stagnation point flow theory is applicable. The similarity variable η

[0138]

[0139] Where a is the velocity characteristic gradient:

[0140]

[0141] Where U0 is the characteristic velocity and L0 is the characteristic length. Since the width of the stagnation flow is much smaller than the height, for a bald wedge, L0 is the blunt width 2d.

[0142] The fluid is divided symmetrically about the xOy plane on the blunt plane, and the flow direction is changed to the z direction. The two-dimensional flow on the xOz plane is analyzed.

[0143] stream function ψ

[0144]

[0145] Derived

[0146]

[0147] Derived

[0148]

[0149] At the wall, x = 0, that is, η = 0:

[0150]

[0151] Substituting into the momentum equation, we obtain the ordinary differential equation:

[0152] f''+ff'+1-(f') 2 =0

[0153] The boundary conditions are the same as formula -. At this time, formula - is no longer applicable, m tends to infinity, indicating that the external flow velocity U e (z) has an infinite gradient at z = 0, which is meaningless in practice and does not require the definition of m and the external flow velocity U e (z). f”(0) is obtained by numerically solving the Hiemenz equation, f″2(0)≈0.9277. External flow velocity U e (z) is expressed as:

[0154]

[0155] At this time, the wall shear stress τ w and frontal area A blade for:

[0156]

[0157] τ w Substitute the viscous friction resistance F f2_2

[0158]

[0159] The plate is symmetrical about the xOy plane, and the friction forces on both sides cancel each other out. Therefore, the viscous friction resistance of the blunt part is 0.

[0160] Due to the existence of the attack angle, the tool is subjected to the fluid diversion along the wall surface. For the wedge body, the wall friction resistance coefficient C of the diversion is f and wall shear stress τ w

[0161]

[0162] Blade side edge circumference s

[0163]

[0164] Viscous friction resistance F of fluid flow on the blade surface along the cutting edge f3

[0165]

[0166] Since the wear of a straight-edged knife has very little effect on the surface area, the approximate perimeter s can be used to simplify the very small quantities in the formula, making it easier to calculate and apply the model later.

[0167]

[0168] Tool viscous friction resistance component F f3 Simplified to

[0169]

[0170] Viscous friction resistance F f The final calculation expression is:

[0171] F f =F f1 +F f2_1 +F f2_2 +F f3

[0172]

[0173] By calculating the coefficient, the tool viscous friction resistance F f Simplified to

[0174]

[0175] Another part of the resistance comes from the pressure resistance generated by the tool shape. The flow resistance on the surface of the ground edge is closely related to the sharpness of the tool. In the pressure resistance calculation formula, the pressure resistance at the blade plane is obtained by integrating the pressure and the area element dA, the fluid density ρ and the relative movement speed v between the blade and the fluid. reland the effective area A of the wetted part of the tool eff and pressure resistance F p The relationship is

[0176]

[0177] Among them, v rel =v tool_n , A eff It is the windward area perpendicular to the incoming flow direction. Pressure resistance coefficient C p It is related to the shape of the tool. The influence of viscous friction has been discussed above. When calculating pressure resistance, the influence of fluid viscosity can be ignored. For inviscid incompressible fluids, the Bernoulli equation is applicable.

[0178]

[0179] For a wedge with a non-small opening angle (θ>20°), when the viscous fluid moves as a whole, the pressure difference needs to consider the kinetic energy term and the viscosity effect, and the drag coefficient C of the wedge edge is approximately estimated. p1 The empirical formula is

[0180]

[0181] When the fluid flows toward the wedge, the flow direction of the fluid is deflected and the velocity of the side wall decays to

[0182]

[0183] According to Bernoulli's equation,

[0184]

[0185] Pressure resistance F p1 Expressed as

[0186]

[0187] The front plane of the cutting edge directly faces the fluid impact, the fluid velocity drops sharply, and the kinetic energy is converted into pressure energy. Therefore, for the cutting edge plane of the tool, the stagnation point velocity is approximately regarded as 0, and there is

[0188]

[0189] The pressure difference Δp2 generated at the cutting edge plane

[0190]

[0191] Among them, p0 refers to the fluid pressure on the blunt edge of the blade, p ∞ Refers to the pressure of the fluid at a distance.

[0192] Because the blunt edge of the blade is very narrow, the pressure is approximately equal everywhere. For a small rectangular plane, the drag coefficient is usually taken as 1.1 to 1.2; for low-speed, high-viscosity incompressible flow, considering the pressure stagnation and viscosity effects, the drag coefficient is usually taken as 1.0 to 1.2. Based on the above conditions, the drag coefficient C of the blade plane is p2 Take 1.1, the pressure resistance F at the cutting edge plane p2

[0193]

[0194] Pressure resistance F p The final calculation expression is

[0195]

[0196] Calculate the coefficient to get the pressure resistance F p Simplify the result

[0197]

[0198] The resistance F of the tool in shear thickening fluid considering the bluntness parameter δ t The overall expression is

[0199]

[0200] Sort out

[0201]

[0202] Using the above formula, the measured motion resistance F t Combined with the parameters of the fluid being cut, the blunting degree parameter δ is obtained. In addition, it can be seen from the formula that since the cutting depth h is dozens of times the thickness b of the blade side edge, the additional viscous friction term generated by the tool slope is small. Since there is a wedge angle in the straight-edged knife, the wedge surface will bring viscous resistance and shape resistance of the pressure gradient, which affects the characterization of the sharpness of the straight-edged knife. Therefore, it is necessary to emphasize the resistance of the tool edge and weaken the additional resistance brought by both sides of the blade, so that the sharpness coefficient δ has a greater impact on the total resistance. If the effect of the change in tool movement speed on the pressure resistance of the tool edge needs to be greater than the effect of the viscous friction resistance of the wedge surface, two relationships need to be met: First, the apparent viscosity of the shear-thickening fluid cannot be a single linear relationship with the shear rate, but is extremely sensitive to changes in the shear rate; second, the shear-thickening fluid has good fluidity, moderate intermolecular forces, and low apparent viscosity at low shear rates. That is, η is satisfied. ∞ >>η aAt high tool speeds, viscous friction is a better indicator of sharpness. At higher tool speeds, pressure resistance is a better indicator of sharpness. Characterizing sharpness when cutting shear-thickening fluids with a straight-edge knife requires a specific cutting rate. Furthermore, this requires high sensitivity and surge characteristics of the fluid's shear-thickening properties to shear rate.

[0203] The tool sharpness testing method and device provided by the embodiments of the present invention offer several significant advantages. First, automatic initial reset and precise positioning ensure that each test begins at a consistent starting position. Furthermore, the use of a high-precision micro-load sensor and real-time data acquisition at a 100Hz sampling frequency accurately captures instantaneous force signals during the cutting process, ensuring high accuracy and stability of the test data. Second, the PLC control program implements a highly automated testing process, eliminating the need for frequent manual intervention throughout the cutting process, data acquisition, and safety monitoring. This significantly improves test efficiency and data repeatability while reducing operational risks. Furthermore, the device's flexible design accommodates diverse tool types, including straight-edged and flaky knives. Its 11 preset cutting speeds accommodate a wide range of operating conditions, from low-speed precision cutting to high-speed mass production, making it widely applicable. Furthermore, the host computer data processing system displays force-time and power-time curves in real time and supports data export, facilitating subsequent quantitative evaluation and process optimization. Finally, comprehensive safety measures—including travel switches, proximity sensors, and an emergency stop button—ensure rapid shutdown in the event of an emergency, ensuring the safety of both the equipment and the operator. In summary, the present invention not only performs outstandingly in terms of precision, automation, applicability, and real-time monitoring, but also has comprehensive safety guarantees, greatly improving the efficiency and reliability of industrial tool sharpness assessment.

[0204] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. Those skilled in the art will recognize that several equivalent substitutions or obvious variations can be made without departing from the scope of the present invention, and that any equivalent performance or application should be considered to fall within the scope of protection of the present invention.

Claims

1. A tool sharpness testing device, characterized in that: include: A servo motor, used to provide driving force; a screw transmission mechanism connected to the servo motor and configured to convert the rotational motion of the servo motor into linear motion; A slide transmission mechanism is connected to the screw transmission mechanism and the tool, and is used to drive the tool to move in a straight line under the action of the screw transmission mechanism; A force signal acquisition unit is used to collect the force signal of the tool in the process of cutting the material in real time; Programmable logic controller, used to control the motion state of the tool; A host computer data processing unit, connected to the force signal acquisition unit, for receiving and storing the force signal and generating a force-time curve and a power-time curve; The tool fixing mechanism is connected to the slide transmission mechanism and is used for fixing the tool.

2. The tool sharpness testing device according to claim 1, wherein: The slide transmission mechanism includes a guide rail seat and an active slide and a driven slide slidably assembled on the guide rail seat, wherein the active slide is connected to the ball nut of the screw transmission mechanism, and the driven slide is connected to the tool.

3. The tool sharpness testing device according to claim 2, characterized in that: The tool fixing mechanism is arranged on the driven slide and includes: a threaded tool holder sleeve structure with a flange fixing surface for fixing the straight-edged tool; a boat-shaped structure fixture, which utilizes a combination of a metal block and an elastic gasket to achieve uniform clamping of the sheet tool through a cross-symmetrical tightening method.

4. The tool sharpness testing device according to claim 2, wherein: The force signal acquisition unit includes a force sensor connected between the active slide and the driven slide.

5. The tool sharpness testing device according to claim 1, wherein: The programmable logic controller includes a forward cutting control unit and a reverse reset control unit, which are used to control the servo motor to rotate forward and reverse to drive the tool to perform forward cutting and reverse reset.

6. The tool sharpness testing device according to claim 5, characterized in that: It also includes a safety protection unit for detecting whether the tool moves according to the preset stroke; the programmable logic controller also includes: an emergency stop control unit for issuing an emergency stop command to cut off the motor drive signal when it detects that the tool does not move according to the preset stroke.

7. The tool sharpness testing device according to claim 6, characterized in that: The safety protection unit includes: a travel switch and a proximity sensor are arranged at the starting and ending positions of the cutting stroke to detect the position of the tool.

8. A method for testing the sharpness of a tool, characterized in that: The test method is implemented by the test device according to any one of claims 1 to 7, and comprises the following steps: Controlling the servo motor to drive the tool to move to determine the tool starting position through the initial reset instruction of the programmable logic controller; The programmable logic controller controls the servo motor to drive the tool to perform forward cutting and reverse reset movements in sequence through cutting instructions, and the force signal acquisition unit acquires the force signal generated during the cutting process in real time during the cutting process; The force signal is received by the host computer data processing unit to generate a force-time curve and a power-time curve.

9. The tool sharpness testing method according to claim 8, wherein: Also includes: Before the cutting test, the force sensor of the force signal acquisition unit is first zeroed and calibrated using a zeroing potentiometer, and the amplification factor is adjusted according to the expected cutting force range to ensure that the amplitude of the collected force signal meets the processing requirements of the host computer data processing unit.

10. The tool sharpness testing method according to claim 8, wherein: A complete test cycle consists of forward cutting and reverse reset, and a preset pause time is set between cycles to ensure data repeatability.

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