The sensor of the automatic feeding CNC lathe is a key component for realizing the automatic closed-loop of "feeding positioning processing", mainly responsible for detecting the position of the workpiece, feeding progress, and spindle status. Common types include photoelectric sensors, proximity switches, displacement sensors, etc. If the sensor malfunctions, it may cause material misalignment, processing interruption, or even equipment collision. It is necessary to scientifically detect and locate the fault, and then replace it according to the standard process to ensure that the equipment quickly resumes stable operation.
1、 Accurate Detection of Sensor Malfunctions: From Phenomenon to Essence Localization
The detection of sensor faults should be combined with the three-step process of "fault phenomenon signal verification hardware troubleshooting" to avoid blind replacement of components.
1. Preliminary judgment based on the fault phenomenon
Different sensor faults correspond to typical performance. First, the range can be narrowed by the equipment status: if the feeding mechanism fails to feed according to the instructions, and the control panel displays the alarm of "workpiece not in place", it is mostly the fault of workpiece detection sensor (such as photoelectric sensor, proximity switch); If the spindle cannot be started and prompts "spindle positioning abnormal", it may be due to the failure of the spindle position sensor (such as encoder, Hall sensor); If the deviation of the feeding length exceeds the tolerance, it is necessary to focus on checking the displacement sensor (such as grating ruler, linear sensor), as such faults often lead to inconsistent machining dimensions of the workpiece.
2. Signal transmission and parameter verification
Using the equipment control system and multimeter for signal detection: First, enter the "diagnostic mode" of the CNC system to check the signal status of the sensor (such as "on/off" and "voltage value"). If there is no signal feedback when the sensor should be triggered, or if the signal continues to be abnormal (such as voltage always being 0V or full range), further circuit testing is required; Measure the sensor power line (usually DC24V) and signal line with a multimeter. If there is no voltage on the power line, check the power supply circuit (such as fuses and wiring terminals); If the power line is normal but the signal line has no signal, it can be preliminarily determined that the sensor itself is faulty.
3. Hardware appearance and environmental inspection
Remove the sensor protective cover and check the hardware status: observe whether there is oil stains or metal debris covering the sensing surface of the sensor (impurities can block the signal, especially for photoelectric sensors), and use a dust-free cloth dipped in a special cleaning agent to wipe it off; Check whether the sensor wiring terminals are loose or oxidized (oxidation can cause poor contact, and the terminals need to be lightly sanded with sandpaper); Check if the sensor casing is damaged and if the cables are broken. If there is physical damage, it is often accompanied by sensor malfunction.
2、 Specification replacement of sensors: from disassembly to installation control details
The replacement of sensors should follow the process of "safe power-off - precise disassembly - matching installation - debugging and calibration" to avoid secondary failures caused by improper operation.
1. Safety preparation and disassembly
Firstly, disconnect the main power supply of the CNC lathe and turn off the air/hydraulic source of the feeding mechanism to prevent equipment misoperation during replacement; Record the installation position of the sensor (such as installation angle, fixing bolt position), and take photos with a mobile phone to avoid misalignment during subsequent installation; When disassembling the sensor, first unplug the wiring plug (pay attention to marking the cable sequence, some sensors are multi-core wires, misconnection can cause signal abnormalities), then unscrew the fixing bolt, remove the faulty sensor, and avoid pulling the cable forcefully to damage the interface.
2. Matching and installation of new sensors
When replacing sensors, it is necessary to ensure "model consistency and parameter matching": the model of the new sensor (such as brand and model code) should be the same as the original device to avoid incompatibility caused by parameter differences (such as sensing distance and output signal type); Align with the original position during installation, tighten the fixing bolts evenly (with moderate force to avoid sensor deformation caused by excessive tightening), adjust the angle of the sensing surface (if the proximity switch needs to maintain a sensing distance of 5-10mm from the workpiece, the photoelectric sensor needs to face the detection point without obstruction); When wiring, connect according to the original markings to ensure that the power and signal lines are not reversed. The plug should be plugged tightly to avoid poor contact.
3、 Debugging and verification after replacement: ensure functional recovery
After the installation of the sensor, it needs to undergo dual verification through "no-load test - material trial processing":
1. No load signal and action test
After power on, enter "manual mode" and trigger the sensor (such as manually pushing the workpiece to the detection position) to check if the control system is receiving signals normally (such as the panel displaying "workpiece in place"); Operate the feeding mechanism and spindle to perform simple actions, observe whether the sensor signals are synchronized and feedback, and ensure no delay or abnormal alarms.
2. Material trial processing and precision calibration
Conduct small-scale material trial processing: select standard workpieces, process them according to normal procedures, measure the dimensions of the workpieces (such as feeding length and processing diameter), and if the dimensional deviation is within the allowable range, it indicates that the sensor replacement is qualified; If there is still a deviation, it is necessary to enter the system's "parameter settings" and calibrate the triggering threshold of the sensor (such as adjusting the sensing distance of the proximity switch and the zero offset of the displacement sensor) until the machining accuracy meets the standard.
4、 Daily prevention: reduce the probability of sensor failure
After replacement, a maintenance mechanism should be established: clean the sensor sensing surface and wiring terminals every week to avoid the accumulation of impurities; Check monthly whether the sensor cables are pulled or squeezed (cables that are prone to wear due to the movement of the feeding mechanism can be equipped with cable protection covers); Calibrate sensor parameters every quarter, especially displacement sensors, to ensure long-term stable signal accuracy and reduce the occurrence of faults from the source.
In summary, the handling of sensor faults in automatic feeding CNC lathes requires precise detection and positioning of the problem, replacement according to standardized procedures, and verification through debugging to ensure functional recovery. At the same time, daily maintenance is relied upon to extend the sensor life and ensure the continuity and stability of equipment automation processing.