What should I do if the CNC lathe spindle cannot start?

　　The CNC lathe spindle is driven by a three-phase asynchronous motor with variable frequency speed regulation.
　　Analyze the reasons for the malfunction of the CNC lathe:
　　(1)Fault of the motor itself
　　(2)The input signal cannot be reliably fed into the frequency converter
　　(3)Fault of the frequency converter itself
　　(4)Fault in the CNC system.
　　The fault phenomena of the spindle not being able to start include:①the motor can only start in one direction;②The motor cannot start in both positive and negative directions.If the spindle cannot start in both directions,the cause of the fault may be a combination of one or more of the above four aspects;If one-way starting is possible,the possibility of motor and frequency converter malfunctions can be ruled out.
　　2、Solution for CNC lathe spindle not starting:
　　The sequence is(1)to check whether the motor is normal;(2)Check whether the input signals of the frequency converter are normal;(3)Check the frequency converter.
　　The method of checking the control signal inputs of the frequency converter is(1)to remove the signal connecting wires from the FWD,REV,and COM terminals of the frequency converter;(2)Input the forward rotation command(M03S500),press the system start button,observe the indicator light of 24V DC relay KA1.If the indicator light is on,it indicates that the CNC system is working normally,and the coil drive circuit of relay KA1 is also working normally;If the indicator light is not on,it indicates that the fault may be an open circuit in the coil drive circuit of relay KA1;Or poor contact of interlocking normally closed contacts;Or the PLC of the CNC system malfunctions.(3)Measure the FWD and COM terminals using the Rxl gear of a multimeter.If there is no continuity,it indicates that the cause of the fault is poor contact of the normally open contact of relay KA1 or an open circuit between FWD and COM;If there is continuity,measure the analog voltage output between A11 and COM using the DC voltage 20V gear of a multimeter.If the voltage value is around 2.5V,it indicates that the cause of the fault is not in the CNC system,but in the frequency converter;If the simulated voltage value is zero or low,it indicates that the cause of the fault is in the CNC system.
　　The reason for the frequency converter malfunction may be:(1)the parameter settings of the frequency converter are incorrect;(2)If the hardware of the frequency converter is faulty,the relevant parameters of the frequency converter should be reset.If the problem cannot be solved,it indicates that the hardware of the frequency converter is faulty.Check if there is a reverse enable signal,but no forward enable signal.The cause of the fault is poor contact of the normally open contact of relay KA1.After replacing KA1,the system operates normally.