Device and method for real-time monitoring of tool breakage during machining of CNC machine tools based on vibration

Abstract

The present invention discloses a real-time monitoring device and method for tool breakage during machining of a CNC machine tool based on vibration. The device tests the vibration characteristic signal when the tool is not cutting, and uses it as a reference characteristic value to determine whether the tool is broken. The tool vibration characteristic signal is monitored in real time during machining, and compared with the obtained reference characteristic value to determine the tool breakage. When it is determined to be a tool breakage, the machine tool alarms, and prompts the tool breakage time and event on the machine tool and on a remotely monitored computer. The present invention monitors the tool breakage status during machining in real time based on the vibration signal characteristics, and utilizes a method of comparing and sorting the full frequency band before and after cutting. It has high sensitivity and rapid response, and is particularly suitable for difficult-to-monitor situations such as long-term high-speed finishing of small tools.

Description

Technical Field

[0001] The invention belongs to the technical field of numerical control machining, and in particular relates to a device and method for real-time monitoring of tool breakage in a machining process of a numerical control machine tool based on vibration. Background Art

[0002] During the machining process of CNC machine tools, tool breakage is very likely to occur due to unreasonable tool paths, unstable cutting forces, poor tool consistency, uneven workpiece materials, tool aging, stress fatigue and other reasons. This is especially common in high-speed machining of small-diameter tools. In addition, tool breakage cannot be discovered in time due to reasons such as small tool size, small cutting amount, and the influence of cutting fluid, which will affect the subsequent machining process and waste a lot of machining time, especially in semi-finishing or finishing processes with longer machining times. Even if the tool breakage can be detected, the exact time cannot be determined, and the remaining machining procedures cannot be reasonably arranged. Therefore, it is very necessary to find a method that can monitor the tool breakage status in real time to deal with the tool breakage problem during the machining process.

[0003] If a CNC machine tool tool breaks during machining, it will affect the subsequent machining process and waste a lot of machining time if it is not discovered in time, especially when using small tools for long-term semi-finishing or finishing. When small tools are used for high-speed machining, they are small in size and have little cutting consumption. In addition, the influence of cutting fluid makes it impossible to judge whether the tool is broken by naked eye observation or sound.

[0004] Existing technical solutions include non-real-time monitoring and real-time monitoring. Non-real-time monitoring mainly includes contact tool setting detection, laser beam detection, industrial camera image recognition detection, etc. Before and after tool processing, the tool is moved to the designated detection position, and the above methods are used to monitor tool breakage. Real-time monitoring determines the tool breakage status by real-time monitoring of key feature quantities before and after the tool breaks during processing, mainly including the motor current of the spindle or inverter, sound signal, vibration signal, etc. Among them, the method of judging by vibration signal includes building a vibration sensor into the tool handle, etc.

[0005] Technology for detecting tool breakage through existing tool setting instruments: It is non-real-time monitoring, and the tool needs to be moved to a specified position before and after processing to test whether the tool is broken, which adds extra time and cannot determine in real time whether the tool is broken during processing, and the real-time performance is poor. Technology for detecting tool breakage through spindle current load, etc.: When a small tool is semi-finished or finished at high speed, due to the small cutting amount, there is no obvious stable change in the motor current of the spindle or inverter before and after the tool breaks, that is, the sensitivity is not high, and the tool breakage phenomenon cannot be effectively determined. Technology for analyzing tool breakage through sound wave sampling: Sound wave analysis is relatively complex, and requires no external sound interference, and has high requirements for environmental factors. Technology of vibration sensor built into the tool handle: Multiple components are integrated in a small space, the structure is complex, the cost is high, and multiple types of tool handles need to be designed separately. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a vibration-based real-time monitoring device and method for tool breakage in a CNC machine tool machining process in view of the deficiencies in the above-mentioned prior art, so as to realize real-time and highly sensitive monitoring of tool breakage during the machining process.

[0007] The present invention adopts the following technical solutions:

[0008] A vibration-based real-time monitoring method for tool breakage during machining of a CNC machine tool comprises the following steps:

[0009] S1. Testing the vibration characteristic signal when the tool is not cutting, as a reference characteristic value for judging whether the tool is broken;

[0010] S2, during the machining process, real-time monitoring of the tool vibration characteristic signal is carried out, and the tool is compared with the reference characteristic value obtained in step S1 to determine the tool breakage situation;

[0011] S3. When step S2 determines that the tool is broken, the machine tool alarms and prompts the tool breakage time and event on the machine tool and the remote monitoring PC.

[0012] Specifically, step S1 is as follows:

[0013] S101, when the tool is not performing cutting processing, collecting full-band vibration spectrum data twice, where the horizontal axis of the spectrum is the frequency and the vertical axis is the corresponding vibration value;

[0014] S102, at each frequency in the full frequency band of the spectrum diagram, the vibration value collected for the second time is calculated with the vibration value collected for the first time to obtain the vibration ratio of each frequency in the full frequency band in the unprocessed state;

[0015] S103, sorting the vibration ratios obtained at all frequencies in the entire frequency band in descending order;

[0016] S104, adding up the ratios at the top of the sorting order to obtain the sum, which is used as a reference characteristic value for determining whether the tool is broken.

[0017] Furthermore, in step S104, the top 3 to 6 ratios are added together.

[0018] Specifically, step S2 is as follows:

[0019] S201, set the lower limit coefficient and the maximum number of consecutive over-limit times, start cutting processing, and collect full-band vibration spectrum data every 3 to 6 seconds;

[0020] S202, calculating the ratio of the vibration value collected each time during processing to the vibration value collected before processing, and obtaining the vibration ratio of each frequency in the full frequency band under the processing state;

[0021] S203, sorting the vibration ratios obtained at all frequencies in the entire frequency band in descending order;

[0022] S204, adding up the ratios at the top of the sorting order to obtain the sum of the ratios, and using the sum as the current feature value for determining whether the tool is broken;

[0023] S205. If the number of times that the current eigenvalue is lower than the reference eigenvalue multiplied by the lower limit coefficient reaches the set maximum number of consecutive exceeding limit times, it is considered that the tool is broken.

[0024] Furthermore, in step S201, the lower limit coefficient is 1 to 1.5, and the maximum number of consecutive exceeding the limit is greater than or equal to 3 times.

[0025] Furthermore, in step S204, the top 3 to 6 ratios are added together.

[0026] Furthermore, in step S205, if the current eigenvalue is lower than the reference eigenvalue multiplied by the lower limit coefficient for three or more consecutive times, it is considered that the tool is broken.

[0027] Another technical solution of the present invention is a vibration-based real-time monitoring device for tool breakage during CNC machine tool machining, comprising a vibration sensor and a vibration monitoring module. The vibration sensor is installed in the area affected by the cutting vibration of the CNC machine tool, the sensor signal of the vibration sensor is connected to the vibration monitoring module, the vibration monitoring module and the CNC machine tool are respectively connected to a monitoring network, the vibration signal is remotely extracted in real time through a computer terminal, and the machine tool is controlled to alarm when the tool breaks.

[0028] Specifically, the areas affected by CNC machine tool cutting vibration include the workpiece, fixture and spindle.

[0029] Compared with the prior art, the present invention has at least the following beneficial effects:

[0030] The present invention discloses a real-time monitoring method for tool breakage in a machining process of a numerically controlled machine tool based on vibration. The method does not limit the installation position of the vibration sensor and only needs to be installed in the vibration-affected area during machining without designing a complicated installation structure. The method collects and analyzes vibration signals during machining in real time, analyzes characteristic signals in the full frequency band, and determines the tool breakage situation with high sensitivity. After the tool breaks, an alarm is issued in time, and a tool breakage time reference is provided to assist process personnel in optimizing the process, avoid unnecessary waste of time, and improve production efficiency.

[0031] Furthermore, in step S1, the vibration characteristic signal is tested when the tool is not performing cutting processing. At this time, the vibration characteristic signal is different from the characteristic signal during cutting. Therefore, the vibration signal at this time can be processed to obtain a reference characteristic value for determining whether the tool is broken.

[0032] Furthermore, in step S104, the top five ratios (3 to 6) are added together, which can take into account vibration characteristics not limited to one frequency, thereby improving the sensitivity of tool breakage monitoring.

[0033] Furthermore, in step S2, the tool vibration characteristic signal is monitored in real time during the machining process, and the current characteristic value is obtained after processing. If the current characteristic value is lower than the benchmark characteristic value multiplied by the lower limit coefficient for 3 or more consecutive times, it means that the tool is broken; otherwise, it means that the tool is not broken.

[0034] Furthermore, in step S201, the lower limit coefficient is 1 to 1.5, which is set according to the characteristic value and the benchmark characteristic value during cutting in actual application. Reasonable setting of the lower limit coefficient can improve the sensitivity of tool breakage judgment; the maximum number of consecutive over-limit times can be set to 3 times or more, which takes into account the situation that the tool does not cut in the processing path, so the tool breakage situation cannot be judged based on only 1 or 2 consecutive over-limit times.

[0035] Furthermore, in step S204, the ratios ranked at the top are added together to be used as the current characteristic value for determining whether the tool is broken. This is to ensure that the method for obtaining the current characteristic value is consistent with the reference value and is comparable.

[0036] Furthermore, in step S205, only when the number of consecutive times that the current eigenvalue is lower than the benchmark eigenvalue multiplied by the lower limit coefficient reaches the set maximum number of consecutive over-limit times (3 times or more), can it be said that the tool is broken. Otherwise, the empty tool path causes 1 or 2 consecutive over-limits, which will lead to misjudgment of the result.

[0037] A vibration-based real-time monitoring device for tool breakage during CNC machine tool processing can use a vibration sensor to monitor the vibration characteristics of the CNC machine tool processing process in real time, process the current characteristic value, and compare it with the baseline characteristic value when not cutting, so as to judge the tool breakage state, and give a timely alarm and prompt the tool breakage time when the tool breaks. The device is simple to install, easy to use, highly sensitive, and quick to respond, and can meet the needs of tool breakage monitoring during CNC machine tool processing.

[0038] In summary, the present invention monitors the broken tool status in the machining process in real time based on the vibration characteristic signal, and utilizes the method of comparing and sorting the full frequency band before and after cutting. It has high sensitivity and rapid response, and is particularly suitable for difficult-to-monitor situations such as long-term high-speed finishing of small tools.

[0039] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram of the installation location of the vibration sensor;

[0041] Figure 2 This is a schematic diagram of the network connection of the vibration monitoring module;

[0042] Figure 3 This is the broken knife monitoring flow chart.

[0043] Among them: 1. Spindle; 2. Workpiece; 3. Fixture. DETAILED DESCRIPTION

[0044] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "one side", "one end", "one side" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, in the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0045] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] See also Figure 1 The present invention provides a real-time monitoring device for tool breakage in a CNC machine tool machining process based on vibration. A vibration sensor is fixed in the CNC machine tool cutting vibration-affected area by strong magnet adsorption or threaded connection, specifically including the four vertical sides of the workpiece 2 and the fixture 3 or the end position of the spindle 1. The vibration sensor is the VSA005 vibration sensor of the IFM manufacturer, with a response frequency of 10kHz. The vibration monitoring module is the VSE100 of the IFM manufacturer, and the sensor signal line is connected to the vibration monitoring module installed in the electric control cabinet.

[0047] See also Figure 2 The real-time monitoring device for broken blades consists of a CNC machine tool, a vibration monitoring module, network interaction equipment (routers, switches, etc.), a monitoring network, and a remote computer running a broken blade monitoring program. The vibration monitoring module performs preliminary processing on the signal transmitted by the vibration sensor through the signal line, and then connects to the monitoring network through the network cable; the CNC machine tool is connected to the monitoring network through the network cable.

[0048] Specifically, the vibration monitoring module and the CNC machine tool can be connected to the same monitoring network using network interactive equipment, ensuring that the remote computer in the monitoring network can access the monitored CNC machine tool and the vibration monitoring module installed in its electric control cabinet, and the vibration signal can be remotely extracted and analyzed in real time through the computer-side tool breakage monitoring program, and the machine tool can be controlled to alarm when the tool breaks.

[0049] See also Figure 3 The present invention provides a real-time monitoring method for tool breakage in a CNC machine tool machining process based on vibration, comprising the following steps:

[0050] S1. Testing the vibration characteristic signal when the tool is not cutting, as a reference characteristic value for judging whether the tool is broken;

[0051] S101, when the tool is not performing cutting processing, collecting full-band vibration spectrum data twice, where the horizontal axis of the spectrum is the frequency and the vertical axis is the corresponding vibration value;

[0052] S102, at each frequency in the full frequency band of the spectrum diagram, the vibration value collected for the second time is calculated with the vibration value collected for the first time to obtain the vibration ratio of each frequency in the full frequency band in the unprocessed state;

[0053] S103, sorting the vibration ratios obtained at all frequencies in the entire frequency band in descending order,

[0054] S104, adding up the top 3 to 6 ratios to obtain a sum, which is used as a reference characteristic value for determining whether the tool is broken.

[0055] S2. Real-time monitoring of tool vibration characteristic signals during machining, comparison with reference characteristic values, and determination of tool breakage;

[0056] S201, set the lower limit coefficient to 1-1.5, set the maximum number of consecutive over-limit times to be greater than or equal to 3 times, start cutting, and collect full-band vibration spectrum data every 3-6 seconds;

[0057] S202, calculating the ratio of the vibration value collected each time during processing to the vibration value collected before processing, and obtaining the vibration ratio of each frequency in the full frequency band under the processing state;

[0058] S203, sorting the vibration ratios obtained at all frequencies in the entire frequency band in descending order;

[0059] S204, adding the top 3 to 6 ratios to obtain a sum, which is used as a current feature value for determining whether the tool is broken;

[0060] S205. If the current eigenvalue is lower than the reference eigenvalue multiplied by the lower limit coefficient for three or more times in a row, it is considered that the tool is broken.

[0061] S3. Machine tool alarm, prompting the time and event of tool breakage on the machine tool and on the remote monitoring computer.

[0062] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0063] Example

[0064] When a CNC machine tool uses a 0.2mm diameter taper flat-bottomed tool to perform fine machining on a workpiece, the tool is prone to breakage. Use a strong magnet to adsorb the vibration sensor VSA005 on the vertical plane on the front side of the fixture, lead the sensor signal line to the vibration monitoring module in the electric control cabinet, and then use a network cable to connect the CNC machine tool, the vibration monitoring module, and the remote computer running the tool breakage monitoring program to the same network through the switch; run the tool breakage monitoring program, collect vibration characteristic signals when the machine tool is not cutting, and obtain the benchmark characteristic value after processing; set the lower limit coefficient to 1.2, the maximum number of continuous over-limit times to 3, start cutting, and monitor the tool breakage status every 3 seconds. Under this parameter setting, when the tool breaks 9 seconds later, the machine tool alarms, the machine tool display panel prompts the tool breakage time, and the remote computer running the tool breakage monitoring program also displays the tool breakage time synchronously.

[0065] In summary, the present invention is a vibration-based real-time monitoring device and method for tool breakage during machining of CNC machine tools. Vibration acceleration sensors are installed at key locations such as the spindle, workpiece, and fixture to monitor the vibration characteristic signals during machining in real time to distinguish whether the current tool is broken. If a tool breaks, the machine tool can send out an alarm signal containing the time of the tool breakage and remotely notify the management personnel. The tool can be replaced based on the time of the tool breakage to continue machining. This method does not affect the CNC machining program, has high sensitivity, and responds promptly. It can effectively reduce unnecessary time waste caused by tool breakage, improve production efficiency, and can also be used by process personnel to optimize machining processes.

[0066] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A real-time monitoring method for tool breakage in a CNC machine tool machining process based on vibration, characterized in that: The following steps are involved: S1. When the tool is not cutting, the vibration characteristic signal is tested as a reference characteristic value for judging whether the tool is broken. Specifically, it is: S101, when the tool is not performing cutting processing, collecting full-band vibration spectrum data twice, where the horizontal axis of the spectrum is the frequency and the vertical axis is the corresponding vibration value; S102, at each frequency in the full frequency band of the spectrum diagram, the vibration value collected for the second time is calculated with the vibration value collected for the first time to obtain the vibration ratio of each frequency in the full frequency band in the unprocessed state; S103, sorting the vibration ratios obtained at all frequencies in the entire frequency band in descending order; S104, adding up the top 3 to 6 ratios to obtain a sum, which is used as a reference characteristic value for determining whether the tool is broken; S2, during the machining process, real-time monitoring of the tool vibration characteristic signal is performed, and the tool breakage is determined by comparing it with the reference characteristic value obtained in step S1. Specifically: S201, set the lower limit coefficient and the maximum number of consecutive over-limit times, start cutting processing, and collect full-band vibration spectrum data every 3 to 6 seconds; S202, calculating the ratio of the vibration value collected each time during processing to the vibration value collected before processing, and obtaining the vibration ratio of each frequency in the full frequency band under the processing state; S203, sorting the vibration ratios obtained at all frequencies in the entire frequency band in descending order; S204, adding the top 3 to 6 ratios to obtain the sum, which is used as the current characteristic value for determining whether the tool is broken; S205, if the number of times that the current characteristic value is lower than the reference characteristic value multiplied by the lower limit coefficient reaches the set maximum number of times that the tool exceeds the limit, it is considered that the tool is broken; S3. When step S2 determines that the tool is broken, the machine tool alarms and prompts the tool breakage time and event on the machine tool and the remote monitoring PC.

2. The method according to claim 1, characterized in that In step S201, the lower limit coefficient is 1-1.5, and the maximum number of consecutive exceeding the limit is greater than or equal to 3 times.

3. The method according to claim 1, characterized in that: In step S205, if the current eigenvalue is lower than the reference eigenvalue multiplied by the lower limit coefficient for three or more consecutive times, it is considered that the tool is broken.

4. A real-time monitoring device for tool breakage during machining of a CNC machine tool based on vibration using the method of claim 1, characterized in that: It includes a vibration sensor and a vibration monitoring module. The vibration sensor is installed in the cutting vibration-affected area of ​​the CNC machine tool. The sensor signal of the vibration sensor is connected to the vibration monitoring module. The vibration monitoring module and the CNC machine tool are respectively connected to the monitoring network. The vibration signal is extracted remotely and in real time through the computer end, and the machine tool alarm is controlled when the tool breaks.

5. The vibration-based real-time monitoring device for tool breakage during machining of CNC machine tools according to claim 4 is characterized in that: The area affected by cutting vibration of a CNC machine tool includes a workpiece (2), a fixture (3) and a spindle (1).

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