A vibration signal assisted end mill installation error automatic identification method and system

Abstract

This invention discloses a vibration signal-assisted automatic identification method and system for end mill installation errors. This method combines conventional trial cutting error prevention and identification methods with online sensor measurement technology, using vibration sensors to automatically determine whether tool installation errors exist. Specifically, based on a tapered trial cutting error prevention platform, spindle vibration signals are incorporated to sense whether the high-speed rotating end mill is engaging with the tapered trial cutting block, thereby determining whether a tool installation error exists. This method eliminates the need for subsequent manual judgment and is particularly suitable for automated machining.

Description

Technical Field

[0001] This invention belongs to the field of CNC cutting and machining, and specifically relates to a vibration signal-assisted automatic identification method and system for end mill installation errors. Background Technology

[0002] In CNC machining, the processing of a complex part often involves a combination of many operations, requiring dozens of cutting tools to complete roughing, semi-finishing, and finishing. However, currently, tool changing is primarily done by manual labor, resulting in low automation. Operators install various tools onto tool holders according to process documents, and tool installation errors are inevitable during this process. These include errors between tools of similar dimensions (tool fillets, tool radii), as well as improper tool overhang lengths. If these installation errors are not detected in time, they can lead to part scrap, tool breakage, or even damage to the machine tool. Therefore, there is an urgent need for a solution that can automatically identify tool installation errors.

[0003] To address the aforementioned issues, Chinese patent CN 112683193 A discloses a method and system for tool type identification and geometric parameter detection based on machine vision. This method uses machine vision to capture images of the tool's cutting edge and employs algorithms to analyze the tool's specific parameters. These parameters are then compared with standard data in a database to determine if installation errors exist. However, this method requires capturing multiple tool images, making the process cumbersome. Furthermore, cutting fluid and chips easily adhere to the tool, significantly interfering with image accuracy. Additionally, machine vision-based methods require in-machine industrial cameras, where the harsh environment of the cutting area, due to cutting fluid and chips, easily damages the camera lens. A dirty camera lens can also introduce significant errors in calculation accuracy, potentially leading to inaccurate identification.

[0004] Chinese patent CN 116276307 A discloses a method for error prevention in machine tool tool installation and recall. The underlying logic of such methods is to compare and analyze actual measured values ​​with correct standard data to determine if an installation error exists. However, this method relies on standard tool setters to measure and calibrate the actual tool installation parameters, and cannot perform in-machine measurements; moreover, tool setters are costly. Furthermore, the entire process depends on workers measuring parameters on the tool setter, making automation difficult. This method may be effective when installation errors are difficult to detect manually, i.e., the differences are small. Otherwise, it reverts to a manual measurement process.

[0005] Furthermore, Chinese patent CN 219093774 U discloses a milling cutter error prevention device. Before formal machining, a specific CNC program is executed on the machine tool to perform a trial cut on a conical error prevention platform to detect any installation errors. Although this patent mentions that by setting up an error prevention platform and a test cutter ring, and featuring a frustum-shaped test cutting surface, an annular test cutter channel, and test cutter steps within the test cutter channel, the dynamic process of the tool can be tested, resulting in higher accuracy and error prevention precision. However, this process still relies on the operator to determine whether the test cutting platform is being used with an incorrectly installed tool.

[0006] In summary, there is currently no reliable method for rapid identification of tooling installation errors. Existing methods suffer from two main problems: high cost and the inability to automate the entire identification process, requiring manual intervention. Summary of the Invention

[0007] To address the aforementioned shortcomings, this invention proposes a vibration signal-assisted method for rapid identification of end mill installation errors. Building upon the conventional trial cutting approach, it further introduces sensor signals to assist in determining whether the trial cutting cone has been damaged, replacing manual judgment and automating the entire tool installation error identification process. This provides a practical and feasible automatic tool installation error identification solution for the development of automated production lines for CNC machine tools.

[0008] A vibration signal-assisted automatic identification system for end mill installation errors includes a metal test cutting block with a tapered blind hole, a vibration acceleration sensor, and a data acquisition and processing unit. The test cutting block is fixedly installed in a designated area of ​​the machine tool table for trial cutting to verify the correctness of the tool installation before part machining. The vibration acceleration sensor is magnetically mounted on the machine tool spindle to monitor online whether the tool on the spindle is engaged in cutting. The data processing unit processes the acquired acceleration signals online and then feeds the identified information back to the machine tool's CNC system.

[0009] A vibration signal-assisted automatic identification method for end mill installation errors includes the following steps: Step 1: Before machining, the worker enters the selected tool number into the machine tool NC system according to the workpiece machining process document. Then, based on the spindle vibration during idle cutting with different types of tools, the threshold value of the vibration signal when the tool participates in cutting is calibrated in advance. Let the tool number be assumed to be... T i Then the threshold value for cutting corresponding to this tool is Mi The resulting tool and threshold calibration dataset is ( T i , M i ), i This represents the number of cutting tools.

[0010] Step Two: Before executing the formal machining, the NC system first checks whether there are any incorrect parameters for the called tools. First, the machine tool NC system will determine the correct parameters based on the corresponding tool name. T i To perform the error-proofing check procedure for this tool matching. P i Once the system recognizes the corresponding tool number, the error prevention mechanism embedded in the program will automatically activate. This program... P i Move the machine tool spindle to the designated position on the worktable to prepare for a trial cut and check for any tool installation errors.

[0011] Step 3: When checking for incorrect tool installation, the machine tool follows a specific program. P i The drive tool moves above the metal block with a tapered hole and gradually moves until the tapered hole is in critical contact with the cutting edge of the tool. Simultaneously, a vibration acceleration sensor mounted on the spindle collects real-time data on the spindle's vibration. If the inspection system determines that the tool is incorrectly mounted, the machine tool stops the cutting operation. Otherwise, if the inspection system deems the tool parameters correct, the machine tool proceeds with the actual machining of the part.

[0012] Step 4: Once the tool error prevention system identifies an unreasonable tool parameter setting, the data acquisition and processing unit writes an instruction to the machine tool NC system via the communication protocol to stop the execution of subsequent cutting tasks.

[0013] Furthermore, in step one, the threshold calibration is performed by calculating the amplitude energy of the FFT spectrum of the acceleration signal, including the tool passing frequency (TPF) and the 10th harmonic range. E To determine whether the tool is involved in cutting, the following methods are used:

[0014] in, E ( t This refers to the energy and parameters used to evaluate whether the cutting tool participates in the cutting process. j This refers to the harmonic frequency order. Furthermore, during test cuts to check for tool mounting errors, this energy and indicator are also monitored in real time. E ( t The determination is made based on the energy and the condition. If the condition is met, the CNC system will continue executing the machining program; otherwise, the program will stop executing further.

[0015] Furthermore, the tool error prevention and inspection system is an edge computing device capable of real-time communication with the machine tool CNC system. This hardware device can automatically read the current tool number through the machine tool CNC system's data acquisition module OPC UA, and perform data processing and analysis on the edge computing device, reducing the computational burden on the machine tool CNC system.

[0016] Furthermore, in step two, the tool error prevention mechanism check procedure... P i This is the beginning of the formal machining program for the embedded part. Before machining the part, a error-proofing check process must be performed. The main purpose of this error-proofing check process is to automatically trigger the corresponding check program based on the tool number, driving the machine tool tool to a designated position for high-speed rotation. In other words, each tool is matched with a corresponding check program. According to the position and size parameters of the test cutting worktable, the tool will move to the vicinity of the tapered test cutting block and perform a test cut check.

[0017] Furthermore, in step three, to check for incorrect tool installation, key parameters are checked, including tool radius, tool fillet radius, and tool overhang length. Considering that the actual tool overhang length cannot be too long, otherwise the rigidity of the machining system will be poor, and conversely, the tool overhang length cannot be too short, otherwise interference between the tool holder structure and the part may occur, the deviation between the theoretical and actual values ​​of the tool overhang length is within a set range. When checking whether the tool overhang length is installed correctly, if the sensor detects a vibration signal monitoring index greater than a threshold, it is determined that the tool overhang length is too long. Conversely, if the sensor detects a vibration signal monitoring index less than a threshold, the tool continues to move to determine if the overhang length is too short. If the sensor detects a vibration signal monitoring index less than a threshold, it is determined that the tool overhang length is too short. At this point, an alarm is issued.

[0018] Furthermore, when checking the tool fillet, the high-speed rotating tool is slowly moved from directly above the tapered hole on the tapered test cutting platform to a designated height, which allows the cutting edge to be in near contact with the tapered surface. If the sensor detects a vibration signal monitoring index greater than a threshold, it indicates that the tool fillet is too small and is participating in the cutting process, thus the tool fillet is determined to be too small. Similarly, when checking the tool radius, if the sensor detects a vibration signal monitoring index greater than a threshold, the tool radius is determined to be too large.

[0019] Furthermore, in step four, once the edge computing system automatically detects a mismatch between the tool parameters installed on the spindle and the process file, it needs to send a command to the CNC machine tool system to stop the current cutting task. The edge computing device writing commands to the CNC system requires the OPC UA protocol.

[0020] The beneficial effects of this invention are as follows: (1) By combining sensor signals with conventional tool trial cutting error prevention mechanisms, the automation level of the tool installation error checking process is improved.

[0021] (2) A method based on acceleration signal tool pass frequency (TPF) energy and index is proposed to distinguish spindle idling and cutting. This method is simple and practical and is very suitable for production site.

[0022] (3) A relatively systematic tool error prevention inspection method and system were proposed, providing a feasible solution for building and developing tool error prevention systems.

[0023] The present application will be described in further detail below with reference to the accompanying drawings. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the automatic tool installation error detection process of the present invention. Figure 2 This is a schematic diagram of the hardware for automatic tool installation error detection according to the present invention. Figure 3 Schematic diagram of the structure and cutting tool for test cutting of metal block. Numbering in the diagram: 1-Test cutting block, 2-Triaxial accelerometer, 3-Data acquisition and processing unit, 4-Machine tool NC system, 5-Tapered hole, 7-Tool holder, 8-End mill. Detailed Implementation The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0025] Figure 1 This is a flowchart illustrating an embodiment of a vibration signal-assisted automatic identification method and system for end mill installation errors according to the present invention. The specific details of the vibration signal-assisted automatic identification method and system for end mill installation errors in this embodiment are as follows: Figure 2 , Figure 3 As shown, a vibration signal-assisted automatic identification system for end mill 8 installation errors is characterized by comprising a metal test cutting block 1 with a tapered blind hole feature, a triaxial acceleration sensor J356A44, and a data acquisition and processing unit 3. The tapered test cutting block 1 is fixedly installed in a designated area of ​​the machine tool worktable for trial cutting to verify the correctness of the tool installation before part machining. The vibration acceleration sensor 2 is magnetically mounted on the machine tool spindle for online monitoring of whether the tool on the spindle is participating in cutting. The data processing unit 3 processes the acquired acceleration signals online and then feeds the identified information back to the machine tool NC system 4.

[0026] A vibration signal-assisted automatic identification method for end mill installation errors includes the following steps: Step 1: Before machining, the worker enters the selected tool number into the machine tool NC system according to the workpiece machining process document. Then, based on the spindle vibration during idle cutting with different types of tools, the threshold value of the vibration signal when the tool participates in cutting is calibrated in advance. Let the tool number be assumed to be... T i The cutting threshold corresponding to this tool is Mi The resulting tool and threshold calibration dataset is ( T i , M i ), i This represents the number of cutting tools.

[0027] Step Two: Before executing the formal machining, the NC system first checks whether there are any incorrect parameters for the called tools. First, the machine tool NC system 4 will determine the parameters based on the corresponding tool name. T i To perform the error-proofing check procedure for this tool matching. P i Once the system recognizes the corresponding tool number, the error prevention mechanism embedded in the program will automatically activate. This program... P i Move the machine tool spindle to the designated position on the worktable to prepare for a trial cut and check for any tool installation errors.

[0028] Step 3: When checking for incorrect tool installation, the machine tool follows a specific program. P i The drive tool moves above the metal block with the tapered hole 5 and gradually moves until the tapered hole 5 is in critical contact with the cutting edge of the tool. Simultaneously, a vibration acceleration sensor mounted on the spindle collects real-time data on the spindle's vibration. If the inspection system determines that the tool is improperly mounted, the machine tool stops the cutting operation. Otherwise, if the inspection system deems the tool parameters reasonable, the machine tool proceeds with the actual machining of the part.

[0029] Step 4: Once the tool error prevention system identifies that the tool parameter settings are unreasonable, the data acquisition and processing unit writes an instruction to the machine tool NC system 4 via the communication protocol to stop the execution of subsequent cutting tasks.

[0030] Furthermore, in step one, the threshold calibration is performed by calculating the amplitude energy of the FFT spectrum of the acceleration signal, including the tool passing frequency (TPF) and the 10th harmonic range. E To determine whether the tool is involved in cutting, the following methods are used:

[0031] in, E ( t This refers to the energy and parameters used to evaluate whether the cutting tool participates in the cutting process. j This refers to the harmonic frequency order. Furthermore, during test cuts to check for tool mounting errors, this energy and indicator are also monitored in real time. E ( t The determination is made based on the energy and the condition. If the condition is met, the CNC system will continue executing the machining program; otherwise, the program will stop executing further.

[0032] Furthermore, the tool error prevention and inspection system is an edge computing device capable of real-time communication with the machine tool CNC system. This hardware device can automatically read the current tool number through the machine tool CNC system's data acquisition module OPC UA, and perform data processing and analysis on the edge computing device, reducing the computational burden on the machine tool CNC system.

[0033] Furthermore, in step two, the tool error prevention mechanism check procedure... P i This is the beginning of the formal machining program for the embedded part. Before machining the part, a error-proofing check process needs to be executed. The main purpose of this error-proofing check process is to automatically trigger the corresponding check program based on the tool number, driving the machine tool tool to a designated position for high-speed rotation. In other words, each tool is matched with a corresponding check program. According to the position and size parameters of the test cutting worktable, the tool will move to the vicinity of the conical test cutting block 1 and perform a test cut check.

[0034] Furthermore, in step three, to accurately check whether the tool parameters are installed incorrectly, the key parameters of the end mill 8 are checked, including the tool radius, tool fillet, and tool overhang length. Considering that the actual tool overhang length cannot be too long, otherwise the rigidity of the machining system will be poor, and that the tool overhang length cannot be too short, otherwise there may be interference between the tool holder 7 and the workpiece, the deviation range between the theoretical and actual values ​​of the tool overhang length is within the set range. When checking whether the tool overhang length is installed reasonably, if the sensor detects a vibration signal monitoring index greater than the threshold, it is determined that the tool overhang length is too long. Conversely, if the sensor detects a vibration signal monitoring index less than the threshold, the tool continues to move to determine whether the overhang length is too short. If the sensor detects a vibration signal monitoring index less than the threshold, it is determined that the tool overhang length is too short. At this time, an alarm is issued.

[0035] Furthermore, when checking the tool fillet, the high-speed rotating tool is slowly moved from directly above the tapered hole 5 on the tapered test cutting platform to a designated height, which allows the cutting edge to be in near contact with the tapered surface. If the sensor detects a vibration signal monitoring index greater than the threshold, it indicates that the tool fillet is too small and is participating in the cutting process, and is therefore determined to be too small. Similarly, when checking the tool radius, if the sensor detects a vibration signal monitoring index greater than the threshold, it is determined to be too large.

[0036] Furthermore, in step four, once the edge computing system automatically detects a mismatch between the tool parameters installed on the spindle and the process file, it needs to send a command to the CNC machine tool system to stop the current cutting task. The edge computing device writing commands to the CNC system requires the OPC UA protocol.

Claims

1. A vibration signal-assisted automatic identification method for end mill installation errors, characterized in that... An automatic identification system for end mill installation errors assisted by vibration signals is used. This system includes a metal test cutting block with a tapered blind hole feature, a vibration acceleration sensor, and a data acquisition and processing unit. The test cutting block is fixedly installed in a designated area of ​​the machine tool's worktable for trial cutting to verify the correctness of the tool installation before part machining. The vibration acceleration sensor is magnetically mounted on the machine tool spindle to monitor online whether the tool on the spindle is participating in cutting. The data processing unit processes the acquired acceleration signals online and then feeds the identified information back to the machine tool's CNC system. The automatic identification method includes the following steps: Step 1: Before machining, the worker enters the selected tool number into the machine tool NC system according to the workpiece machining process document. Then, based on the spindle vibration during idle cutting with different types of tools, the threshold of the vibration signal when the tool participates in cutting is calibrated in advance. The tool number is assumed to be... T i Then the threshold value for cutting corresponding to this tool is Mi The resulting tool and threshold calibration dataset is ( T i , M i ), i Number of cutting tools; Step Two: Before executing the formal machining, the NC system first checks whether there are any incorrect parameters for the called tools. First, the machine tool NC system will determine the correct parameters based on the corresponding tool name. T i To perform the error-proofing check procedure for this tool matching. P i Once the system identifies the corresponding tool number, the error prevention mechanism embedded in the program will automatically activate. P i Move the machine tool spindle to the designated position on the worktable to prepare for a trial cut and check for any tool installation errors. Step 3: When checking for incorrect tool installation, the machine tool will follow the program. P i The drive tool moves to the top of the test cutting block and gradually moves it until the tapered hole on it is in critical contact with the cutting edge of the tool. At the same time, the vibration acceleration sensor installed on the spindle collects the vibration of the spindle in real time. If the inspection system determines that the tool is incorrectly installed, the machine tool stops the cutting task. Otherwise, the inspection system determines that the tool parameter settings are reasonable and executes the formal machining of the part. Step 4: Once the tool error prevention inspection system identifies that the tool parameter settings are unreasonable, the data acquisition and processing unit writes instructions to the machine tool NC system through the communication protocol to stop the execution of subsequent cutting tasks.

2. The method for automatic identification of end mill installation errors assisted by vibration signals according to claim 1, characterized in that... In step one, the threshold calibration is performed by calculating the amplitude energy of the FFT spectrum of the acceleration signal, including the tool passing frequency (TPF) and the 10th harmonic range. E To determine whether the tool is involved in cutting, the following methods are used: in, E ( t This refers to the energy and parameters used to evaluate whether the cutting tool participates in the cutting process. j This refers to the harmonic frequency order. Furthermore, during test cuts to check for tool mounting errors, this energy and indicator are also monitored in real time. E ( t If the energy and satisfy the condition, then... If the condition is met, the CNC system will continue executing the machining program; otherwise, the program will stop executing further.

3. The method for automatic identification of end mill installation errors assisted by vibration signals according to claim 1, characterized in that... The aforementioned tool error prevention and inspection system is an edge computing device that communicates with the machine tool CNC system in real time. This edge computing device can automatically read the current tool number through the machine tool CNC system data acquisition module OPC UA, and perform data processing and analysis on the edge computing device, thereby reducing the computational burden on the machine tool CNC system.

4. The method for automatic identification of end mill installation errors assisted by vibration signals according to claim 1, characterized in that... The tool error prevention mechanism check procedure in step two is described above. P i At the beginning of the formal machining program for the embedded part, before the part is machined, a fault prevention check process is executed. This fault prevention check process automatically triggers the corresponding check program according to the tool number, driving the machine tool tool to the designated position for high-speed rotation. That is, each tool is matched with a corresponding check program. According to the position and size parameters of the test cutting worktable, the tool moves to the vicinity of the test cutting block and performs a test cutting check.

5. The method for automatic identification of end mill installation errors assisted by vibration signals according to claim 1, characterized in that... In step three, to check if the tool is installed incorrectly, key parameters are checked, including tool radius, tool fillet, and tool overhang length. The deviation between the theoretical and actual values ​​of the tool overhang length is within the set range. When checking if the tool overhang length is installed reasonably, if the sensor detects a vibration signal monitoring index greater than the threshold, it is determined that the tool overhang length is too long. Conversely, if the sensor detects a vibration signal monitoring index less than the threshold, the tool is moved further to determine if the overhang length is too short. If the sensor detects a vibration signal monitoring index less than the threshold, it is determined that the tool overhang length is too short, and an alarm is issued.

6. The method for automatic identification of end mill installation errors assisted by vibration signals according to claim 5, characterized in that... When checking the fillet radius of the cutting tool, the high-speed rotating tool is slowly moved from directly above the tapered hole on the test cutting block to a specified height. This height allows the cutting edge to be in close contact with the tapered surface. If the sensor detects a vibration signal monitoring index greater than the threshold, it indicates that the tool fillet radius is too small and is participating in the cutting process. Similarly, when checking the tool radius, if the sensor detects a vibration signal monitoring index greater than the threshold, it indicates that the tool radius is too large.

7. The method for automatic identification of end mill installation errors assisted by vibration signals according to claim 1, characterized in that... In step four, once the edge computing system automatically identifies that the tool parameters installed on the spindle do not match the process file, it sends an instruction to the CNC machine tool system to stop the current cutting task. The edge computing device needs to use the OPC UA protocol to write instructions to the CNC system.

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