Abstract: This paper introduces the research and development of a circular saw blade flatness detection system. Using an eddy current sensor, data acquisition card, stepper motor, and PC as hardware, and LabVIEW as the development platform, a circular saw blade flatness detection system was designed. This system can efficiently detect the flatness of circular saw blades and is suitable for quality control in actual production processes. Keywords : LabVIEW; Circular saw; Flatness; Detection 1 Introduction Circular saw blades are widely used cutting tools in the wood and stone processing industry. The flatness of a circular saw blade refers to the minimum distance between two parallel planes containing all measurement points. Flatness is one of the important indicators reflecting the quality of saw blades. Excessive flatness not only affects the end runout of the saw blade, but also directly affects the stability of the saw blade when cutting the plate, and may even lead to its unusability [1]. Therefore, saw blades must undergo flatness testing before leaving the factory, and only qualified ones are allowed to leave the factory, otherwise they are treated as defective products. At present, domestic saw blade manufacturers usually use a measuring ruler to manually test the flatness of circular saw blades, which is very inefficient. A few companies have imported foreign testing equipment, but it is expensive and difficult to maintain. Therefore, how to achieve automatic detection of saw blade flatness at a lower cost has important practical significance. LabVIEW is the virtual instrument development platform of NI (National Instruments). It is programmed in G (Graph) language, which is very flexible and convenient, and has powerful data acquisition, data processing and graphic display functions. It is a powerful tool for developing computer measurement and control systems based on PC platforms. The circular saw blade flatness detection system designed and developed based on the LabVIEW platform has great practical value in saw blade quality control. 2 Scheme Design 2.1 Detection Principle As shown in Figure 1, to detect point A on the circular saw blade, three values ​​are needed: the radius R of point A, the angle α, and the deformation value δ of point A, which can be expressed as [2]. If δ is positive, it means that the point of the saw blade is "protruding", and if it is negative, it means that it is "concave". Here, the flatness is simply defined as the largest "protruding" value minus the deepest "concave" value among all detection points. If the "protruding" value or the "concave" value is too large, or the difference between the "protruding" value and the "concave" value exceeds the specified value, it is considered a non-conforming product. [align=center] Figure 1 Schematic diagram of saw blade[/align] Based on this, the detection system is designed as shown in Figure 2. Multiple eddy current sensor probes are fixedly installed on a support at certain intervals, and the probe ends are flush. In order to prevent the iron support from interfering with the eddy current sensor, the front end of the probe should protrude a certain distance from the support. After the saw blade is installed, a starting line is marked, and then a stepper motor drives it to rotate. The angle α value is obtained based on the movement of the stepper motor. The R value is determined by the installation position of the eddy current sensor probe. The deformation of the saw blade plane is obtained by the difference between the distance from the point on the eddy current sensor probe to the probe tip and the distance from the probe tip to the reference plane. One rotation of the saw blade completes the detection of one side. [align=center] Figure 2 System Schematic Diagram[/align] 2.2 System Composition The detection system consists of an eddy current sensor, a preamplifier, a data acquisition card, a PC, and a stepper motor, as shown in Figure 3. The eddy current sensor is the JX20 series eddy current displacement sensor from Guangzhou Jingxin Instrument & Electrical Co., Ltd., the data acquisition card is the PCI-6024E acquisition card from NI, and the stepper motor is the 55BF003 stepper motor from Changzhou Shuangjie Electronics Co., Ltd. The PCI-6024E data acquisition card provides 16 single-ended/8 differential analog inputs, 2 analog outputs, and 8 digital I/O ports; 12-bit A/D conversion accuracy, 200Kb/s sampling rate, and adjustable voltage input range up to single-ended 20V or differential V. The eddy current sensor probe and preamplifier convert displacement into voltage signals. The PC acquires these voltage signals via the data acquisition card, processes them, and obtains the deformation value, either "convex" or "concave". Simultaneously, the PC outputs pulses through the data acquisition card to control the stepper motor's movement, obtaining the value based on the pulse count and stepper motor step angle. The eddy current sensor probe is connected to the analog input channel of the data acquisition card according to its installation position. The PC determines the detection point radius R through the analog input channel number. [align=center] Figure 3 System Structure Diagram[/align] 3 Software Design The detection system software is implemented using NI (National Instruments)'s LabVIEW virtual instrument development platform. LabVIEW's graphical programming language is simple and intuitive. Its unique front panel design provides users with great flexibility in designing system interfaces. At the same time, LabVIEW supports data acquisition from up to thousands of hardware devices [3]; it can also communicate with other applications or data sources via network and interactive communication; and it has powerful data processing and graphics display functions. 3.1 Software structure As shown in Figure 4, the circular saw blade flatness detection system software includes five main parts [4]: ​​the main program is responsible for system interface management, program flow control and coordination and communication between various modules; the stepper motor control module controls the start and stop of the stepper motor; the data acquisition module acquires the displacement signal between the saw blade plane and the eddy current sensor probe; the data processing and display module processes the acquired displacement signal and displays it on the front panel; the database management module completes data storage and playback, report generation and other functions. [align=center] Figure 4 Software structure diagram [/align] Since this system uses NI's PCI-6024E data acquisition card, its hardware driver is included with the LabVIEW installation CD. Therefore, it can be configured and used in programming simply by following the operation prompts. 3.2 Main Program The main program controls the flow of the testing system and calls other modules in an event-driven manner. When the main program runs, the saw blade specification is selected first. When the "Start Testing" button is clicked, the stepper motor drives the saw blade to rotate, and the data acquisition module collects the relative displacement value of the saw blade through multiple channels. The saw blade automatically stops after rotating one revolution. The data processing module processes the collected relative displacement value to obtain the required data, displays it on the front panel, and automatically stores it in the database. When the "Historical Data" button is clicked, previous testing data can be retrieved for viewing; when the "Statistical Report" button is clicked, a statistical report is generated from the testing data within a certain period. 3.3 Front Panel The front panel of the circular saw blade flatness testing system is shown in Figure 5, including a display section and a control section. The display section displays the saw blade flatness value and the location of non-conforming points (if any) in numerical form; displays the product grade in text form; displays the most "convex" and most "concave" points on the tested saw blade in graphical form, distinguished by different colors; and displays the running status and pass/fail status using LEDs. The control unit can select the saw blade specification to be tested and perform functions such as testing, historical data playback, report generation, and stopping. [align=center]Figure 5 System Front Panel[/align] 4 Conclusion Developing a computer measurement and control system using the LabVIEW virtual instrument development platform is flexible, convenient, highly scalable, and easy to debug and maintain. The circular saw blade flatness testing system is now in use, achieving the effects of improving work efficiency and reducing labor intensity, generating approximately 600,000 yuan in economic benefits annually. The author's innovation lies in applying virtual instrument technology to the flatness testing of circular saw blades. Based on the LabVIEW platform, and combined with eddy current sensors, data acquisition cards, stepper motors, and other equipment, the development of a circular saw blade flatness testing system was completed, achieving automation of circular saw blade flatness testing with minimal hardware and software investment. References: [1] Pan Tianhao, Li Hangao. A brief discussion on the technical requirements of the matrix of combined saw blade [J]. Stone, 1999 (9): 21-23. [2] Zhang Yuanliang, Jia Sanshan. Detection of axial deformation of circular saw blade [J]. Control and Detection, 2005 (7): 61-62. [3] Zhao Shenghui, Liu Ping. Computer control experimental system based on virtual instrument [J]. Microcomputer Information, 2006, 7-1: 78-80 [4] Zhang Mingde, Guo Xiaodong, Li Yong. Research and development of flatness detection system for bevel gear mounting surface [J]. Journal of Sichuan Ordnance, 2005 (5): 24-26.