Phenomenon 4: Under-protection of electrical equipment In the national standard GB/T5226.1, thermal protection measures are required for motors with a running speed of 0.5kw and above. The failure of heat accumulation of the motor is an important cause of motor burnout. In the process of machine tool equipment modification, the “time-current†protection device, that is, the time constant of the protection device and the protected device winding, is often not effective, and the protection is not effective. We have seen in actual work that repaired and modified machine tools often have problems in this respect. Previous page next page Chain Block 1 Ton,Chain Come Along,Chain Pulley Block,Chain Block 2 Ton Guangdong Gongyou Lift Slings Machinery CO.,LTD , https://www.workmateslift.com
Phenomenon 5: Control circuit buried danger is well known. For such signals involving personnel and equipment safety, such as emergency stop signal, overtravel signal, alarm signal, etc., it should be “parking off by power†and “cutting off the controlled deviceâ€. All power-on conductors (GB/T5226.1-9.4.2.1) We have encountered a CNC machine tool designed and modified by a private enterprise. The limit travel switch uses normally open contacts, which means that when the machine tool does not overtravel, the line is “OFF†(low level), when the moving part overtravels the stroke switch, the line is closed (high level). During the debugging of the machine tool, the maintenance personnel are measuring the line, and the connected plug is not removed. It can be plugged in in time, and the line is always in the normally open state during the test run. The controller confirms that the machine is "normal", so that the screw support bearing seat is damaged. It can be imagined that if the mobile towline line is disconnected due to mechanical reasons during the user's use, who should bear the property damage or personal injury?
The "grounding of the relay coil side" in the control circuit has long been considered as an effective safety measure to avoid malfunction and malfunction. However, in some modified machine tools, the control coils are provided with control contacts on either side or one end is connected to the power supply, and the other end contacts are common. As the line is put on and off on the machine tool, if a certain place is short-circuited to the ground due to mechanical wear insulation failure, the relay malfunctions, and the consequences are unimaginable. It is worth mentioning that some electrical transformation designers, for the convenience of the diagram, often design the control output to form a collector open circuit to directly drive the relay line diagram, but at the same time also buried the hidden danger of the accident.
Phenomenon 6: Insufficient safety operation protection function When there is a danger of splashing, there is no protective door interlocking function. When it is necessary to confirm that the operator's hands have left the dangerous action area, there is no two-hand control mode. When the phase loss causes the electrical appliance to be burned, the three-phase linkage circuit breaker is not installed, and the three-way insurance is used separately, which directly constitutes a hazard to personnel and property.
Phenomenon 7: The warning signs are not perfect. Some modified machine tools have not been able to give corresponding warning signs in accordance with the requirements of GB5226.1-18.2. It is often not well described in the revised technical documentation, and the operator is verbally warned only during training.
Second, on the convenience of maintenance
1. GB/T5226.1 clearly states that “all aspects including guards, cutting/clamping, software and documents together constitute an industrial machine†explains the importance of numerical control equipment for “documents/softwareâ€, which is regarded as Part of the equipment is the “parts†of the numerical control equipment. The technical documents play a vital role in the maintenance of the numerical control equipment. The standard stipulates that the manufacturer must provide the end user with the scope and content of the technical documents. Changes in structure must revise the original documents to reflect the actual situation of the equipment. However, some actual changes have been found in the actual work, especially some minor changes, and no corresponding revisions or explanations have been made on the relevant technical documents. The documents do not match the actual conditions. Some equipment has been changed into several parts of the "three no" products with wireless number, no device identification, no circuit or mechanical drawings after several repairs and changes. Formed between the internal management and maintenance personnel of the enterprise. The situation that non-self can't repair it. And the equipment management department of the general enterprise often asks the manufacturer The management of technical documents is relatively strict, and the maintenance “change record†has not paid enough attention. The longer this situation lasts, the more serious the problem, the more obvious the dependence of CNC equipment on “specific people†or specific maintenance units. Thereby reducing the market competitiveness of the enterprise and restricting the development of the enterprise. Therefore, enterprises with numerical control equipment should pay special attention to whether the information provided by the transformation party meets the requirements of GB/T5226.1-19 in the process of equipment transformation.
2. The sense of standardization is weak, and the implementation of national standards in construction is not a cost increase, but how much it costs, often just a little effort. We once encountered a piece of equipment, the electrician facilitated wiring for the figure, connected a row of insurance power supply lines to the insurance lower gate, and connected the load end to the insurance upper gate. When other personnel repaired, after unplugging the insurance, they mistakenly believe that the gate of the insurance has been cut off, and a false alarm occurred during the measurement, which almost caused electric shock. It can be seen that not working according to standards will pose a threat to the safety of maintenance personnel.
We have seen that due to the large number of connectors used in the power supply and signal connection of machine tools, there are some problems in the use of the plug-in parts. For example, in violation of the relevant safety standards, the plug on the caller side is in the form of a pin, and the power-receiver is used. The plug is in the form of a jack to bury dangerous hazards.
3. Setting the device identification not according to the standard On some modified machine tools, we found that the technicians wrote the device identification directly on or attached to the device. Especially for some wearing parts, the mark will be traced after repair and replacement of these devices, which will bring difficulties to the next maintenance work.