Method for on-line monitoring defects of milling tool

A method for on-line monitoring defects of a milling tool, comprising the steps of:

• 1) establishing a three-dimensional space coordinate system oxyz centering on a machine tool spindle, wherein z axis is located on the axis of the machine tool spindle, and the x and y axes are perpendicular to the z axis, respectively, installing a vibration sensor module on the machine tool spindle, starting the machine tool spindle, and debugging the vibration sensor module to ensure that signals in x, y and z directions meet the requirements;
• 2) acquiring initial sample data;
• 2.1) taking one revolution of the spindle as a period T0;
• 2.2) when n blades on a cutter head enter normal milling, where 2≤n≤8, measuring, by the vibration sensor module, the initial vibration signals of n blades in x, y and z directions within a period T0, and outputting the initial vibration signals to the data acquiring and signal shaping module;
• 2.3) receiving and shaping the initial vibration signal, by the data acquiring and signal shaping module, to obtain n initial cutting wave data respectively formed by n blades in x and y directions in a period T0, and outputting the initial cutting wave data to a data comparing and analyzing module;
• 2.4) analyzing and processing, by the data comparing and analyzing module, the initial cutting wave data to obtain a sample cutting wave area S1 in a period T0, which will be saved as the initial sample data;
• 3) according to the requirement of machining precision, setting a threshold value ΔS0 of a difference between cutting strong vibration wave areas formed by each blade in a period T0 in the data comparing and analyzing module;
• setting a time interval period T in the data comparing and analyzing module, T=mT0, wherein m is an even number greater than n, and setting a threshold value ΔS1;
• 4) when a workpiece is processed formally, measuring, by the vibration sensor module, the vibration signals of n blades in x, y and z directions in each period T0 in real time, and outputting the vibration signals to the data acquiring and signal shaping module;
• 5) receiving and shaping the vibration signal, by the data acquiring and signal shaping module, to obtain n strong vibration cutting wave data respectively formed by n blades in x and y directions in a period T0, and outputting the strong vibration cutting wave data to the data comparing and analyzing module;
• 6) analyzing and processing, by the data comparing and analyzing module, the strong vibration cutting wave data to obtain the difference
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• between the cutting strong vibration wave areas formed by each blade in each period T0, wherein i≠j, n is the number of blades;
• 7) comparing, by the data comparing and analyzing module, the size relationship between ΔS0/ and ΔS0 from time to time, wherein if ΔS0<ΔS0/, and ΔS0<ΔS0/ still holds after comparing the following two consecutive sets of data, the data comparing and analyzing module outputs a blade defect signal to a display alarm module, and the display alarm module issues an alarm;
• 8) if the data comparing and analyzing module does not output the blade defect signal during the comparing process in step 7), comparing, by the data comparing and analyzing module, the difference value ΔS1/=|S1−S1| between the average values S1 and S1 of the blade cutting wave areas in m periods T0 and ΔS1 according to a set period T;
• wherein if ΔS1<ΔS1/, and ΔS1<ΔS1/ still holds after comparing the following two consecutive sets of data and reducing the monitoring period by half in turn, the data comparing and analyzing module outputs a blade wear signal to the display alarm module, and the display alarm module issues the alarm.