The standardization of numerical control equipment has always been considered as a matter of equipment manufacturer's product design and production process. Therefore, it is often not paid enough attention in the process of equipment maintenance and renovation, and even in the refurbishment design of the machine tool, it does not mention the proper position. This has caused some equipment to leave hidden dangers and regrets after maintenance, renovation and renovation. With the continuous deepening of China's reform and opening up, domestic enterprises have increasingly used CNC equipment in the production process in order to adapt to market competition and improve their ability to respond to the market. With the maintenance and transformation work becoming more and more important, the standardization problems in maintenance and transformation have to be very urgently mentioned on our agenda. The following are only based on "GB/T5226.1 "Industrial Machinery Electrical Equipment Part 1: General Technical Conditions" and "GB9061 "General Technical Conditions for Metal Cutting Machine Tools" and "JB4139 "Metal Cutting Machine Tool and Machine Tool Accessories Safety Protection Technical Conditions" "Standards, through the examples of several problems, illustrate the importance of standardization work in equipment maintenance and transformation.

First, with regard to the safety of persons and property <br> <br> this issue it is very important. Whether in China's relevant national standards or in the CE certification of the EC mechanical and electrical products, it is an important part of mandatory enforcement. “The safety of personnel and property, the consistency of control response and the convenience of maintenance” clearly stipulates that “the above basic elements should not be sacrificed to obtain high performance.” (IEC204.1, GB5226.1) However, in actual maintenance and reconstruction work, The following phenomena still occur:

Phenomenon 1: Unconnect the neutral line to the PE.

Take China's national standard GB/T5226.1 as an example, and paragraph 5.1 clearly stipulates that “in the electrical equipment, the neutral line and the protective ground circuit should not be connected. The PEN terminal should not be used inside the mechanical cabinet. "We have encountered more than one modified machine tool. Because of the addition of the device, AC220V power supply is required. Then one of the three-phase 380V is connected to the PE ground of the machine to form AC220V. After adding the three-phase power device, The center line drawn from it is connected to the PE terminal. Obviously, if a certain place is disconnected due to a mechanical failure, the device becomes a charged body with a voltage of 220 VAC to the ground. The device at this time can cause direct electric shock damage to personnel.

In general, machine tool manufacturers are required to use the center line only with the consent of the user in accordance with national standards. The center line should be clearly marked on the mechanical technical documentation (installation diagram and circuit diagram), and the line marked with N should be provided for the center line. Insulated terminals are used." Therefore, when the machine tool is rebuilt, it is imperative to save the line to the PE to ensure the safety of production and maintenance personnel.

Phenomenon 2: Non-single power supply Some devices add some mechanisms. Because the wiring is convenient or related to other devices, the power consumption of the newly added mechanism is not from the wire under the power cut-off switch of the device, and the other leads are violated. The standard provision for "connecting mechanical and electrical equipment to a single power supply" (GB/T5226.1-5.1). In an emergency, disconnecting the power switch on the device does not cut off all power to the device, which is a potential hazard to personnel.

Phenomenon 3: Insufficient protection level of electrical cabinets We have been entrusted to the acceptance of a certain equipment after the transformation. The electrical cabinet of the equipment is one person high (about 1800MM), the single door width is about 800mm, and there is no door switch. Anyone who uses no tools can open the electrical cabinet door and enter the interior of the electrical cabinet. The protection level of the components in the electrical cabinet is IP1.1. Obviously the electrical cabinet structure of the equipment violates the following provisions of GB/T 5226.1-6.2.1: “The casing (ie opening the door, cover, cover, etc.) is only allowed to be opened under the following conditions: a The guard must be opened by a skilled technician or trainee using a key or tool. It may not be suitable to open electrical equipment during operation. b) Cut off the live parts inside the enclosure before opening the cover; this technical requirement may be by the door and the disconnect switch (eg The interlocking mechanism of the power cut-off switch is implemented so that the switch can only be opened after the cut-off switch is turned on, and the switch can be turned on after the door is closed. c) Only when all the live parts are in direct contact with the protection level of at least IP2X or IPXXB (see IEC 529) allows the enclosure to be opened without the use of a key or tool and without disconnecting live parts." Therefore, the protection level of the equipment cabinet is far from "only allowing skilled personnel to enter and complying with special technical requirements (IEC364─4 ─41 IEC─4─47 IEC439─1).” The hidden safety hazards can be imagined.

The electrical cabinet ventilation of CNC machine tools and equipment has long been recognized as a "positive pressure" method in the world, but it has not been realized in some machine tool transformations. We have encountered a domestic machine tool that uses negative pressure ventilation, and the cutting fluid on the tool holder enters the electric cabinet along the snakeskin hose. The moisture in the cable trench, the dust during cutting, etc. all enter the electric cabinet along each channel and gap. The machine tool uses about one year or so, and the surface of the circuit board and the electrical components in the electrical cabinet is covered with dirt and obvious traces of moisture (condensation). This machine tool failure frequently affects the normal production process. It is clearly stated in GB5226.1-13.3 that the enclosure of the control unit should generally have a degree of protection not less than IP54 (see IEC 529). This shows that it is costly not to act according to standards.

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