Numerical Control Lathe: After prolonged operation, it's inevitable for malfunctions to occur. Today, let's share two common main shaft failures and their solutions.
One: Main spindle motor overheating fault in CNC lathe
1. Fault Phenomenon
A CNC lathe experienced a "chewing tool" phenomenon during operation, resulting in tool damage.
2. Fault Detection and Analysis Handling
By manually setting the lathe's X and Z axes to the origin using the JVC manual jogging mode, we restarted the machining program and conducted a test run. When the worktable rapidly approached the machining position, the spindle still did not rotate. Consequently, we diagnosed a fault in the AC variable-frequency spindle motor speed control system.
b. The main shaft motor is controlled by an AC inverter (due to the machine tool manufacturer not providing internal diagrams of the AC inverter), therefore, the "Mathematical Fuzzy Inspection Method" is adopted, treating the internal of the AC inverter as a 'black box.' It is only necessary to check the status of the external functional interfaces to determine its condition.
Firstly, inspect the LED alarm display content of the inverter control system.
d. To differentiate between overheating (referring to the motor itself overheating) and overloading (indicating the motor's load is too heavy, causing excessive torque), the operator, relying on experience, felt that the motor housing was extremely hot. After a period of forced cooling with a large fan, the motor temperature decreased. Upon restarting, the main shaft motor operated normally. This led to the conclusion that the case was a typical example of motor overheating. Upon disassembling the main shaft motor, a thorough inspection revealed that the independent cooling fan motor bearing was damaged, resulting in poor heat dissipation and triggering an overheating alarm for the main shaft motor. This ultimately caused the CNC lathe's main shaft to suddenly stop rotating during operation, leading to a "chatter" fault.
After replacing the independent cooling fan motor, the CNC lathe operates normally, and the fault has been resolved.
