A broken tool early warning method for a numerical control machine tool end mill

Abstract

A kind of broken tool early warning method of numerical control machine tool vertical milling cutter belongs to numerical control processing technical field, to solve the problem of existing broken tool early warning accuracy not high.This application method includes the following steps: the blank model shape contour is compared with the finished part shape contour in the same coordinate system, obtains processing area;Start machine tool, while executing G code program executes cutting judgment program;The cutting judgment program is: judging the position of vertical milling cutter, when vertical milling cutter is 1-3 seconds stroke away from processing area, start broken tool early warning program: collect the vibration signal of numerical control machine tool spindle;With M vibration signal as a group, record the vibration value peak in each group of vibration signal;Whether broken tool working condition occurs is judged by the vibration value peak of adjacent two groups of vibration signals.

Description

TECHNICAL FIELD

[0001] The present application relates to the early warning technology of the broken tool of the vertical milling cutter of the numerical control machine tool in the machining process, and belongs to the numerical control machining technical field. BACKGROUND

[0002] In the automatic production process, small-diameter tools, especially tools with a diameter less than 6 mm, are very easy to break in machining. If the numerical control machine tool continues to run machining under the condition that the tool has been broken, not only the machining time of the numerical control machine tool is wasted, but also the parts produced this time will have defects and cannot meet the normal use requirements, and it is more likely that some positions of the parts are not machined, causing the subsequent tool to impact the workpiece. If the tool breakage in the machining process of the small-diameter tool can be warned online, great economic benefits will be brought to the numerical control machining. How to realize the identification of the tool breakage and improve the accuracy of the tool breakage identification is a problem to be solved urgently. SUMMARY

[0003] In view of the problem that the existing tool breakage early warning accuracy is not high, the present application provides a tool breakage early warning method of a numerical control machine tool vertical milling cutter.

[0004] The tool breakage early warning method of the numerical control machine tool vertical milling cutter provided by the present application comprises the following steps:

[0005] S1, reading a workpiece blank three-dimensional model;

[0006] S2, reading a workpiece numerical control G code machining program to obtain a finished part shape contour;

[0007] S3, comparing the blank model shape contour and the finished part shape contour in the same coordinate system to obtain a machining area;

[0008] S4, starting the machine tool, executing the cutting judgment program while executing the G code program; the cutting judgment program is: judging the position of the vertical milling cutter, when the vertical milling cutter is away from the machining area by 1-3 seconds of travel, starting the tool breakage early warning program of steps S5-S7;

[0009] S5, collecting the vibration signal of the numerical control machine tool spindle;

[0010] S6, taking M vibration signals as a group, recording the vibration value peak in each group of vibration signals;

[0011] S7, judging whether the vibration value peaks of adjacent two groups of vibration signals simultaneously satisfy the following two discriminants:

[0012]

[0013] In the formula, Q iQ is the vibration value peak in the current i group of vibration signals, Q i-1 A is the vibration value peak in the previous group of vibration signals, A is a floating proportional threshold value, A = 5-20; g is the gravity acceleration; B is the vibration value of the vibration signal.

[0014] If the condition is met, it is considered that the end mill occurs the broken tool condition, and if the condition is not met, it is considered that the broken tool condition does not occur.

[0015] Preferably, in step S6, the value of M is determined according to the principle that the sampling frequency N is 0.01-0.03 times.

[0016] Preferably, when the end mill occurs the broken tool condition, the following steps are performed:

[0017] S8, the system spindle of the numerical control machine tool stops feeding and stops rotating.

[0018] Preferably, when the end mill does not occur the broken tool condition, the following steps are performed after step S6:

[0019] S9, the end mill of the numerical control machine tool completes machining and exits the machining area. When the cutting judgment program judges that the end mill of the numerical control machine tool completely exits the machining area after 1-3 seconds, the broken tool early warning program is closed and the vibration signal of the spindle of the numerical control machine tool is stopped collecting;

[0020] S10, the numerical control machine tool is stopped.

[0021] Preferably, the floating proportional threshold value A = 10, and the vibration value of the vibration signal B = 1.

[0022] The beneficial effects of the present application are as follows: the present application designs a broken tool early warning system based on the vibration value peak of the vibration signal to judge whether the tool is broken, mainly based on the great change of the vibration value peak of the vibration signal before and after the broken tool, whether the adjacent two groups of vibration value peaks of the vibration signal meet the proposed discrimination condition at the same time, so as to judge whether the broken tool occurs. According to the workpiece blank model and the finished part model set by the G code, comparison is made in the same coordinate, the machining area is obtained, the broken tool early warning program of the present application is started 1-3 seconds before the end mill enters the machining area, and most of the vibration signals caused by the idle running of the end mill can be filtered out. Similarly, the broken tool early warning program of the present application is closed 1-3 seconds after the end mill exits the machining area.

[0023] When the end mill feeds and retracts (i.e. in the process of 1-3 seconds before entering the cutting machining area, in the process of 1-3 seconds after exiting the cutting machining area), the vibration value of the vibration signal may meet the standard of the broken tool early warning program, therefore, the vibration value of the vibration signal during feeding and retracting is filtered out, and technical means is adopted to filter out the vibration signal with small amplitude during feeding and retracting. It can be seen that the broken tool early warning program of the present application eliminates the factors that may cause misjudgment, and the accuracy of the judgment result is high.

[0024] A = 10, B = 1, the cutting judgment program will start the tool breaking early warning program 1-3 seconds in advance when the end mill is about to enter the machining area, effectively filtering out the interference of a large number of vibration signals of the end mill idling on the tool breaking early warning program. After filtering out by this method, only 1-3 seconds of idling signal is left. When the end mill exits the machining area, the tool breaking early warning program is turned off 1-3 seconds after the end mill completely exits the machining area, and there will still be 1-3 seconds of idling signal interfering with the judgment of the tool breaking early warning program. The vibration values of the vibration signals in the above two idling conditions are basically 0.2g-0.8g. When the vibration value is in the range of 0.2g-0.8g, the vibration signal may meet the accuracy of the tool breaking early warning program in some cases. Therefore, the vibration signal with a vibration value less than 1g is filtered out by using the condition Q i >1g, and the accuracy of the tool breaking early warning program is improved. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a schematic diagram of a workpiece blank, a part and a machining area;

[0026] Figure 2 is a main flowchart of the tool breaking early warning method of the end mill of the numerical control machine tool;

[0027] Figure 3 is a principle diagram of the cutting judgment program of the numerical control machine tool;

[0028] Figure 4 is a logic diagram of the tool breaking early warning program of the numerical control machine tool;

[0029] Figure 5 is a logic diagram of the cutting judgment program of the numerical control machine tool. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0032] The present application will be further described below in combination with the drawings and specific embodiments, but is not limited by the present application.

[0033] Specific embodiment one: the present application will be described below in combination with Figures 1 to 5The embodiment is illustrated, and the broken tool early warning program of the numerical control machine tool is as follows:

[0034] S1, reading a three-dimensional model of a workpiece blank;

[0035] S2, reading a workpiece numerical control G code processing program, and obtaining a finished part contour;

[0036] S3, comparing the blank model contour and the finished part contour in the same coordinate system to obtain a processing area;

[0037] S4, starting the machine tool, and executing the cutting judgment program while executing the G code program; the cutting judgment program is to judge the position of the end mill, and when the end mill is away from the processing area by 1-3 seconds of stroke, the broken tool early warning program of steps S5-S7 is started;

[0038] S5, collecting the vibration signal of the numerical control machine tool spindle;

[0039] S6, taking M vibration signals as a group, and recording the vibration value peak in each group of vibration signals;

[0040] S7, judging whether the vibration value peaks of adjacent two groups of vibration signals satisfy the following two discriminants at the same time:

[0041]

[0042] In the formula, Q i is the vibration value peak in the current i-th group of vibration signals, Q i-1 is the vibration value peak in the previous group of vibration signals, A is a floating proportional threshold value, A=5-20, and the preferred value is 10; g is the acceleration of gravity; B is the vibration value of the vibration signal, which is determined according to the actual situation, and the preferred value is 1.

[0043] If it is satisfied, it is considered that the end mill occurs broken tool condition, and if it is not satisfied, it is considered that the broken tool condition does not occur.

[0044] The present application monitors the spindle vibration signal during the operation of the numerical control machine tool to judge whether the end mill occurs broken tool condition. During the process that the end mill processes the workpiece blank until it exits the processing area, if the end mill occurs broken tool, the present application can immediately monitor it.

[0045] Referring to Figure 1 , A is a three-dimensional model of a workpiece blank, B is a finished part contour of a workpiece blank after being processed by a G code program, and C is a processing area obtained by comparing the blank model and the finished part contour in the same coordinate system. By reading the range of the processing area, it can be known whether the end mill is in a working state during the processing.

[0046] Referring to Figure 2 , the filtering means adopted in the air milling stage of the end mill is first to compare the three-dimensional model of the workpiece blank and the contour of the finished part in the same coordinate system to obtain the machining area. The obtained machining area is used to execute the cutting judgment program to judge the current working state of the end mill. The collected vibration signals are sent to the host computer and subjected to grouping processing and calculation processing. Then a floating proportional threshold A is set, and the processed vibration signals are sent to the tool breakage early warning program for judgment to determine whether the end mill is currently damaged. If the tool breakage early warning program issues an alarm, the spindle of the numerical control machine tool stops feeding and rotation, and if the tool breakage early warning program does not have any abnormality, the numerical control machine tool continues to work.

[0047] Referring to Figure 3 , the shape of the blank is known, and the three-dimensional model of the workpiece blank is read. Then the G code machining program is read to obtain the contour of the finished part, and the contour of the blank model is compared with the contour of the finished part in the same coordinate system to obtain the machining area. The cutting is divided into several processes: the air milling stage when the cutting machining area has not been reached (i.e. the blank has not been touched), the normal working condition stage when the whole tool enters the cutting machining area, and the air milling stage when the end mill completely exits the machining area (i.e. completely exits the blank). The vibration signals in the 1-3 second stage before the end mill enters the machining area, the normal working condition stage when the whole tool enters the cutting machining area, and the 1-3 second stage after the end mill completely exits the machining area are monitored. In order to avoid the interference of the air milling signals, two methods are adopted to filter out the air milling signals. 1. Through the cutting judgment program, a large number of air milling signals when the end mill of the numerical control machine tool travels to the machining area are filtered out. 2. Through the Q i >Bg condition in the tool breakage early warning program, the signals in the two stages not filtered out in method 1 (the vibration signals in the 1-3 second stage before the end mill enters the machining area and the 1-3 second stage after the end mill completely exits the machining area) are filtered out. The reason for filtering out the vibration signals in these two stages is that the vibration signals in these two stages may also satisfy the tool breakage condition in the tool breakage early warning program (a large change in the vibration signals). If the vibration signals in these two stages are processed, the accuracy of the tool breakage early warning program can be improved. It can be seen that the present application uses filtering means to process only the vibration signals in the normal working condition stage to judge whether a large change in the vibration value of the vibration signals occurs to give the determination of whether the tool is broken.

[0048] Referring to Figure 4 , the tool breakage early warning program: first, the vibration signal acquisition card parameters are set, and a relatively reasonable sampling frequency N is set according to the working condition. When the vibration signals of the spindle of the machine tool are collected, the collected vibration signals are sent to the host computer, and when the length of the collected signals reaches M, they are grouped. The peak value Q i-1If the length of the collected signal is not M, the collection continues. Repeat the above operation, continue to collect signals, and construct a group every M received vibration signals. Record the vibration value peak Q of the group of vibration signals i If the adjacent two groups of vibration signals satisfy the following two discriminants at the same time: It is considered that the tool breaking condition occurs, and the system spindle of the numerical control machine tool stops feeding and stops rotating. If it is not satisfied, it is considered that the tool breaking condition does not occur.

[0049] The principle of M value is: 0.01-0.03 times of the sampling frequency N. According to different situations, the value of M needs to be determined according to the actual situation. If the sampling frequency is too large, the value of M may also be 0.01-0.03 times of the sampling frequency N.

[0050] The first discriminant is to judge whether the vibration value peak of the adjacent two groups of vibration signals changes greatly, and the second discriminant is to filter out the smaller vibration value peak of the vibration signal when feeding and retracting.

[0051] Referring to Figure 5 For the filter means used in the idle running stage of the ball end mill, the shape contour of the finished part is obtained by reading the three-dimensional model of the workpiece blank and the G code program, and compared with the workpiece blank to determine the machining area, that is, the coordinate range during cutting machining. When the coordinates of the ball end mill reach 1-3 seconds before the coordinate range of the machining area, the tool breaking early warning program of the application is started. When the coordinates of the ball end mill completely exit the coordinate range of the machining area after 1-3 seconds, the tool breaking early warning program of the application is closed.

[0052] Although a large number of idle running signals in the whole milling process are filtered out, there are still two sections of idle running signals before the ball end mill reaches the machining area for 1-3 seconds and after the ball end mill completely exits the machining area for 1-3 seconds, which interfere with the tool breaking early warning program. The vibration value of these two parts of vibration signals is basically 0.2g-0.8g, so Q i >1g is used to filter out the vibration signal with a vibration value less than 1g, which does not participate in the judgment of the tool breaking early warning program, and the accuracy of the tool breaking early warning program is improved.

[0053] Although the application is described herein with reference to specific embodiments, it should be understood that these examples are merely illustrative of the principles and applications of the application. It should therefore be understood that numerous modifications can be made to the exemplary embodiments, and that other arrangements can be devised without departing from the spirit and scope of the application as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways other than the original claims describe. It should also be understood that features described in connection with one embodiment can be used in other embodiments.

Claims

1. A method for early warning of tool breakage of CNC machine tool end mills, characterized in that, The method includes the following steps: S1. Read the 3D model of the workpiece blank; S2. Read the CNC G-code machining program of the workpiece and obtain the outline of the finished part; S3. Compare the outline of the blank model with the outline of the finished part in the same coordinate system to obtain the processing area; S4. Start the machine tool and execute the cutting judgment program while executing the G-code program. The cutting judgment program is to determine the position of the end mill and start the tool breakage warning program in steps S5-S7 when the end mill moves 1 to 3 seconds away from the machining area. S5. Collect vibration signals from the CNC machine tool spindle; S6. Take M vibration signals as a group and record the peak value of the vibration in each group of vibration signals; S7. Determine whether the peak values ​​of two adjacent sets of vibration signals simultaneously satisfy the following two discriminant equations: In the formula, For the current number The peak value of the vibration in the group of vibration signals, This represents the peak value of the vibration in the previous set of vibration signals. This is the floating ratio threshold. =5~20; It is the acceleration due to gravity; The vibration value is the vibration signal value. If the conditions are met, the end mill is considered to have broken; if the conditions are not met, it is considered that no breakage has occurred.

2. The method for early warning of tool breakage of CNC machine tool end mills according to claim 1, characterized in that, In step S6, the value of M is determined by the principle of being 0.01 to 0.03 times the sampling frequency N.

3. The method for early warning of tool breakage of CNC machine tool end mills according to claim 1, characterized in that, When an end mill breaks down, perform the following steps: S8. The CNC machine tool's system spindle stops feeding and stops rotating.

4. The method for early warning of tool breakage of CNC machine tool end mills according to claim 3, characterized in that, If the end mill does not break down, the following steps are performed after step S7: S9. The CNC machine tool end mill completes machining and exits the machining area; 1-3 seconds after the cutting judgment program determines that the CNC machine tool end mill has completely exited the machining area, the tool breakage warning program is turned off and the acquisition of the vibration signal of the CNC machine tool spindle is stopped. S10, CNC machine tool shutdown.

5. The method for early warning of tool breakage of CNC machine tool end mills according to claim 1, characterized in that, Floating ratio threshold =10, vibration signal vibration value =1.

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