3. Detection method of tool wear and damage
(1) Tool, workpiece size and relative distance measurement method The tool and workpiece size are generally measured by contact probe. There are two ways to install the probe: one is to measure the size of the tool on the machine bed, called the tool test. Head; one is equivalent to a special tool, mounted on the machine spindle or tool holder to measure the size of the workpiece, called the workpiece probe. The amount of wear of the tool is determined by measuring the amount of displacement of the tool and the amount of displacement of the new surface of the workpiece.
(2) Radiation method A part of the isotope is infiltrated into the worn portion of the blade, and the amount of wear (or the amount of damage) of the tool is determined by measuring the amount of radiation of the isotope.
(3) The basic principle of the resistance method is: as the tool wear amount increases, the contact surface of the tool and the workpiece increases, so the contact resistance of the tool-workpiece decreases; or a precise resistance material is uniformly applied to the tool. On the back surface, as the amount of wear increases, the resistance material decreases and the resistance gradually decreases.
(4) Optical image method The optical method uses the principle that the wear zone has stronger light emission capability than the unworn zone, and a strong light is irradiated on the flank face, and the use of the tool is determined according to the intensity of the emitted light. .
(5) Cutting force method The installation of the force gauge is determined according to the processing conditions. In general, it is mounted on a lathe or on a tool holder; on a machine such as a milling machine or a drill press, it is mounted on a workbench. There are various implementations for monitoring tool conditions using cutting forces, using the main cutting force FX, FY ratio FX/FY or FY/FX and its rate of change d(FY/FX)/dt to comprehensively monitor tool wear and breakage. In addition, the machine's spindle torque and bearing force can be used to monitor the cutting state of the tool.
(6) Cutting temperature method There are three main methods for measuring cutting temperature: thermochemical reaction method, magnetic radiation method and thermoelectric potential method. The thermoelectric potential method is more commonly used. It uses a thermocouple as a measuring component, and a thermocouple is embedded in the tool to measure the cutting temperature to monitor the wear of the tool. The cutting temperature method is not suitable for interrupted cutting and cannot be used to monitor tool breakage.
(7) Cutting power method The wear tool consumes more power than the sharp tool, and the cutting power (main motor power, feed motor power) reflects the cutting force. The power can be measured by using an AC transformer, a DC transformer, a Hall power meter, a shunt divider, and the like. The advantage of the power method is that the signal acquisition is simple and reliable, and the sensor is easy to install and easy to promote in production. However, the tool wear and damage information in the power signal is weak and the sensitivity is low.
(8) Vibration method The acceleration sensor is mounted on the machine table or tool holder, the vibration signal of the machine tool is measured, and then the time domain and frequency domain analysis are performed to obtain the state information of the tool.
(9) Noise analysis method The noise signal of the machine tool can be measured and analyzed to monitor the state of the tool. In general, it is more efficient to use the energy of a certain frequency band in a noise signal to monitor the tool state. However, this method is greatly disturbed by the environment.
(10) Acoustic emission method When the material is plastically deformed or broken, the instantaneous elastic energy is released and expressed as a change in the intensity of the acoustic pulse wave at the ultrasonic frequency. The frequency of the acoustic emission signal ranges from tens of thousands of Hz to hundreds of thousands of Hz. When the tool is almost damaged, the intensity of the acoustic emission increases to 3 to 7 times the normal value.
(11) Machining surface roughness method In the cutting process, when the surface roughness of the machined surface is excessively poor, it is considered that the tool can no longer be used. For the measurement of the surface roughness, an optical interference method and a contact probe method can be employed.
At present, the monitoring of tool wear and damage is still in the research stage, and there are still few practical products. Monitoring methods that are generally considered to have promising prospects include cutting force (torque) method, vibration method, power (current) method, and acoustic emission method.
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