	US 11,945,066 B2
	Method for on-line monitoring defects of milling tool
Huajun Cao, Chongqing (CN); Degui Qiu, Chongqing (CN); Hu Liu, Chongqing (CN); and Yingqing Chai, Chongqing (CN)
Assigned to CHONGQING UNIVERSITY, Chongqing (CN)
Appl. No. 17/425,156
Filed by CHONGQING UNIVERSITY, Chongqing (CN)
PCT Filed Sep. 3, 2020, PCT No. PCT/CN2020/113144 § 371(c)(1), (2) Date Jul. 22, 2021, PCT Pub. No. WO2021/043192, PCT Pub. Date Mar. 11, 2021.
Claims priority of application No. 201910828083.6 (CN), filed on Sep. 3, 2019.
Prior Publication US 2022/0118574 A1, Apr. 21, 2022
Int. Cl. G08B 21/00 (2006.01); B23Q 17/09 (2006.01)

CPC B23Q 17/0957 (2013.01) [B23Q 17/0971 (2013.01)]

5 Claims

1. 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 S₁in a period T₀, which will be saved as the initial sample data;

3) according to the requirement of machining precision, setting a threshold value ΔS₀of a difference between cutting strong vibration wave areas formed by each blade in a period T₀in 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 T₀in 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

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 ΔS₀from 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 S₁and S₁of the blade cutting wave areas in m periods T₀and ΔS₁according 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.