In the context of standardized numerical control (NC) equipment, this work has traditionally been regarded as the responsibility of manufacturers during design and production. As a result, it often receives insufficient attention during maintenance and renovation phases. Even in the case of machine tool refurbishment, the proper placement of critical components is frequently overlooked. This neglect can lead to hidden dangers and long-term regrets in the equipment.
With the continuous deepening of China's reform and opening-up policy, domestic companies have increasingly adopted CNC equipment to enhance their competitiveness and improve market responsiveness. In this evolving landscape, the standardization of maintenance and renovation processes has become an urgent priority on our agenda. Drawing from standards such as "GB/T 5226.1 - Industrial Machinery Electrical Equipment Part I: General Technical Conditions," "GB9061 - General Requirements for Metal Cutting Machine Tools," and "JB4139 - Technical Conditions for Safe Protection of Metal Cutting Machine Tools and Machine Tool Accessories," we will illustrate the importance of standardization through real-world examples.
**I. Personnel and Property Safety**
This issue is of utmost importance. Both Chinese national standards and CE certification for European machinery and electronic products emphasize safety as a mandatory requirement. The IEC 204.1 and GB 5226.1 clearly state that “safety of personnel and assets, consistency of control response, and ease of maintenance†should not be compromised for performance gains. However, in practice, several issues still persist:
**Phenomenon 1: Random Connection of Neutral Line to PE**
For example, some retrofitted machine tools connect the neutral line directly to the PE terminal to create a 220V power supply. If a mechanical failure causes a disconnection, the device becomes live with 220V relative to ground, posing a serious risk to personnel. According to GB/T 5226.1, such connections are strictly prohibited unless explicitly permitted and documented.
**Phenomenon 2: Non-Single Power Supply**
Some devices are connected without a single power source, meaning that turning off the main switch doesn't disconnect all power. This creates a hazard during emergency situations.
**Phenomenon 3: Insufficient Protection of Electrical Cabinets**
We once reviewed a machine tool where the electrical cabinet had no door switch and could be opened without tools. Its IP rating was far below required standards, violating GB/T 5226.1-6.2.1, which mandates that only trained personnel should access such areas under safe conditions.
**Phenomenon 4: Under-Protection of Electrical Equipment**
Many motors over 0.5kW require thermal protection. Failure to implement this can lead to motor burnout, especially when mismatched with the motor’s time-current characteristics.
**Phenomenon 5: Control Circuit Hazards**
Improperly wired emergency stop or limit switches can cause dangerous failures. We encountered a case where a faulty wiring setup led to a crash during testing, highlighting the risks of non-compliant control circuits.
**Phenomenon 6: Inadequate Safety Functions**
Lack of interlocking mechanisms for protective doors or phase loss protection can result in severe damage to both equipment and personnel.
**Phenomenon 7: Missing Warning Signs**
Some modified machines lack necessary warning labels, increasing the risk of accidents due to inadequate operator awareness.
**II. Maintenance Convenience**
Standardized documentation plays a crucial role in CNC equipment maintenance. However, many renovated machines suffer from outdated or incomplete technical documents, making repairs difficult. Proper labeling and clear records are essential for effective maintenance.
**III. Key Issues to Address**
First, repairing or modifying CNC machines requires more than just technical skills—it demands a thorough understanding of relevant standards, particularly those related to safety. Second, standardization is vital for ensuring reliable operation and preventing costly failures. Third, following standards reduces maintenance costs by minimizing downtime and avoiding unnecessary damage. Finally, standardization reflects the quality and professionalism of maintenance teams, and it is essential for the long-term success of any CNC equipment operation.
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