Tool wear monitoring method and system under variable operational conditions based on decoupling of cutting force component

A tool wear monitoring method under variable operational conditions based on the decoupling of cutting force component, comprising the steps of:

• step S1:
• acquiring a tool location source file (TLSF) according to structural features of a part;
• step S2:
• inputting TLSF into a cutting physical simulation model to extract and calculate a tool-workpiece-engagement (TWE);
• step S3:
• acquiring a cross-point frequency response function FRF of a tool tip of a machine tool and a sensor mounting position by carrying out a hammer-hit experiment to a tool of the machine tool along a feed direction of machine tool spindle and along a direction perpendicular to the feed direction respectively;
• step S4:
• calculating a maximum allowable tool tip excitation force at each position of the part during a cutting process based on the conversion of surface roughness Ra of a certain step of the machined part into a surface position error parameter SLE;
• calculating, based on a machine tool accuracy factor, a maximum allowable cutting force limit value due to tool wear;
• step S5:
• acquiring spindle vibration and a displacement signal in the cutting process of the machine tool through a three-way acceleration sensor and an eddy current displacement sensor, and acquiring a spindle rotation speed, a feed speed, a tool tooth number, a tool name and spindle X/Y/Z coordinate data;
• and correlating sensor data with process instruction data by the tool name to form a data set with labeled tool name information as spindle vibration data of a cutting process of a numerically controlled machine tool, and establishing a data set with labeled tool name information according to the acquired data;
• step S6:
• performing trend-term removing and low-pass filtering on the labeled spindle vibration data, and using the labeled spindle vibration data after trend term removing and low-pass filtering as an input signal for a milling force indirect measurement model for estimating a cutting force acting on the tool in real time for decoupled separation of a tool wear cutting force component;
• step S7:
• inputting cutting parameter data of the machine tool into a real-time milling force simulation model in real time, and simulating the milling force online in combination with the tool-workpiece-engagement (TWE) and a milling force coefficient as a measured cutting force of a sharp tool;
• step S8:
• converting each of a measured cutting force data segment and a simulated cutting force data segment into a frequency domain by Fast Fourier Transform, calculating spectrum energy sums within a frequency band interval of the two kinds of cutting forces respectively, and subtracting the simulated cutting force spectrum energy sum from the measured cutting force spectrum energy sum to obtain a spectrum energy sum reflecting tool wear information;
• step S9:
• obtaining a cutting force ratio index by making a ratio based on the measured cutting force spectrum energy sum and the simulated cutting force spectrum energy sum, and monitoring a degradation state of the tool under a time-varying cutting operational condition by the cutting force ratio index;
• step S10:
• obtaining a maximum allowable theoretical cutting force increased due to tool wear at each position by making a difference with the simulated cutting force in step S7 based on the maximum allowable excitation force at each position during the cutting process of the part obtained in step S4;
• and
• step S11:
• comparing the cutting force increased by the actual tool wear in step S8 with the maximum allowable theoretical cutting force increased by the tool wear in step S10, performing a tool change of the machine tool under the condition that the actual tool wear level is greater than the theoretically allowable tool wear level, otherwise continuing to monitor a tool wear state of the machine tool until the excessive wear occurs.