The increasing use of numerical control (NC) devices has made it essential to ensure their effective operation. When a failure occurs, the goal is to restore the device as quickly as possible. This requires maintenance personnel to possess not only deep technical knowledge—such as electromechanical integration, computer principles, NC technology, PLC, automatic control, and hydraulic systems—but also general machining skills and basic NC programming abilities. Additionally, they must be proficient in English to understand technical documentation. Having access to critical data such as machine diagrams, parameter backups, system manuals, and PLC ladder diagrams is equally important. A stock of spare parts and practical experience are also necessary for efficient troubleshooting.
One of the first steps in fault diagnosis is identifying the symptoms. Understanding how and when the failure occurred, what triggered it, and its consequences helps narrow down the root cause. For example, a CNC cylindrical grinder using the Bryant TEACHABLE III system experienced an issue where the dresser wore out the grinding wheel. By removing the wheel and running the machine, the problem was observed: during the dressing phase, the E-axis moved too quickly, triggering the upper limit switch prematurely. Analysis of the system revealed a feedback error, which was resolved after checking the encoder and control board.
Modern NC systems have advanced self-diagnostic capabilities. They often display alarm messages that help identify the problem. For instance, a Siemens 810 system might show a "BATTERY ALARM POWER SUPPLY" message, indicating a dead backup battery. Replacing the battery typically resolves the issue. Similarly, a FANUC 0TC system may trigger an alarm like "HYD. PRESSURE DOWN," signaling low hydraulic pressure. In such cases, inspecting and adjusting the hydraulic system restores normal operation.
When alarms do not directly point to the cause, a more detailed analysis is required. The PLC status display function in many NC systems allows technicians to monitor input/output signals, timers, and counters. This can reveal issues with switches, relays, or mechanical components. For example, a FANUC 0TC lathe displayed an X-axis overrange alarm, but the actual problem was a faulty limit switch detected through the PMC status display. Replacing the switch resolved the issue.
Another powerful technique involves analyzing the PLC ladder diagram provided by the machine manufacturer. These diagrams illustrate the logic used to detect faults. For example, a Siemens 810 system failed to return to the reference point due to a faulty indexing device. By monitoring the ladder diagram, the technician identified a signal issue and traced it back to a misaligned proximity switch, which was then repaired.
In some cases, the exchange method is used to isolate faulty components. Replacing suspected boards with known good ones can quickly pinpoint the issue. For instance, an E-axis following error on a Bryant system was resolved by swapping the position control board. In another case, a Siemens 3 system had an X-axis reference point issue, which was solved by swapping EXE boards between axes.
Maintaining a logical approach is key to effective troubleshooting. Following principles such as checking external components first, then internal, and prioritizing mechanical over electrical issues helps streamline the process. For example, a Siemens 810 system’s X-axis overload alarm was traced to a rusted ball screw, which was replaced after inspection.
Overall, mastering the working principles of both the NC system and the machine tool is crucial for successful fault diagnosis. Combining observation, analysis, and systematic testing enables technicians to resolve complex issues efficiently. Whether through direct alarm interpretation, PLC diagnostics, or component replacement, each step contributes to restoring the machine to full functionality.
Niobium Metal,Pure Niobium Alloy Crucible,Pure Niobium Metal Cup,Pure Niobium Metal Crucible
ZHENAN NEW METAL CO .,LTD , https://www.zanewmaterial.com