How to diagnose the faults of CNC machine tools | Forum

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may maple Sep 16

How to diagnose the fault source of CNC machine tool and deal with the question to make it run normally is the what a machine shop or CNC machining company should know. More resources and guide for precision machining and CNC services are available on, with various data.

1. Intuitive method

That is to use people's senses to pay attention to the various external scenes when (or after) a defect, and to distinguish the possible parts of the defect. This is the first entry point to deal with the shortcomings of the CNC system, and it is usually the most direct and most useful method. After this direct inquiry, we can deal with the problems. At the scene of the defect, we can find out whether there are abnormal noises or sparks when the defect occurs (or after the defect occurs), where they come from, where they appear burnt smell, where they are abnormal heating, where there is abnormal shivering, and so on. Then, we can further query each circuit board or various electronic control components (relays, thermal relays) that may have faults Electrical appliances, circuit breakers, etc.) appearance conditions, such as whether there are scorched, smoked black or components, wiring cracks, and then further reduce the inspection plan. In addition, check whether the connection cables of the system are loose, disconnected, and poor touch are also the primary needs to think of when dealing with the shortcomings of the CNC system. This is the most basic, simple and commonly used method. This method is not only applicable to the earlier system with defect alarm flash, but also to the early system without defect alarm flash. Using this method, dealing with some electrical short circuit, open circuit, overload and so on is the most commonly used. Although the application of this method is simple, it asks the repairman to have a certain resume. In the repair process, develop a detailed and steady working mood, good at finding and handling questions. It's usually an anomaly, which is the crux of the problem.

2. Use the hardware alarm function of CNC system

In order to protect the trekking system, many hardware alarm and indication devices are set up in modern CNC system, such as LED or multi section digital tube on NC main board, axis control panel, power supply unit, spindle servo drive module, servo drive unit of each axis, etc. after the indicator light is on or off, the flashing status of the nixie tube (such as number, symbol) is displayed To indicate the location and type of the defect address for the repairer. Therefore, in the process of dealing with the shortcomings of the CNC system, assuming that the intuitive method can not work, that is, it is difficult to distinguish the query address from the appearance, or when the CRT screen cannot be lit (there is a defect in the power module), we can examine the above alarm devices, query whether there are alarm instructions, and then refer to the random instructions according to the instructions to deal with the defects according to the instructions. This method is especially effective for all kinds of general-purpose CNC systems, such as FANUC, Mitsubishi and Siemens systems, because of their relatively perfect system accounting plan, they have fully considered the most common shortcomings in the system, and built in more hardware alarm equipment, so it is particularly effective. However, this method is based on the fact that there are detailed alarm statements on hand.

3. Make full use of the software alarm function of CNC system

Nowadays, CNC systems have the function of self diagnosis. During the operation period of the system, the system can be timely diagnosed with self diagnosis program. Once the defect is found, the fault will flash on the CRT or light up the alarm indicator on the panel. And this self diagnosis function can also classify and alarm the defects. For example, ① misoperation alarm; ② relevant servo system alarm; ③ set fault alarm; ④ various travel switch alarm; etc. when repairing, you can find the crux address of the question according to the alarm content prompt. However, this method is based on the fact that there are detailed alarm statements on hand.

4. The application status flashed to confirm the diagnosis function

Modern CNC system can not only flash out the fault diagnosis information, which is described in method 3, but also provide various conditions of diagnosis by means of diagnosis address and diagnosis data. For FANUC system, for example, the system supplies "d" (diagnosis) indicating I / O signal status of direct interface between system and machine tool, or between PC and CNC equipment, and between PC and machine tool In other words, it can use the status flash of CRT screen (usually binary byte "0" and "1" indication) to check whether the NC system inputs the signal to the machine tool; or whether the on-off signals triggered by various master switches and travel switches on the machine side are accurately input into the CNC system according to the request. In summary, after listing the above conditions, we can distinguish whether the defect is on the side of the machine tool or the same side of the CNC system, and then we can determine the defect in a certain component, and then we can deal with the problem. All of these benefits from the status flash function of the perfect system supply, which opens a "window" for the diagnosis of defects. By using this method, the diagnosis action is disorderly, and the shortcomings such as knife change arrangement play a very high cultural value. It is also one of the fundamental ways to diagnose the shortcomings. But the application condition is the system supply status flash function.

5. In case of any defect, the parameters of the numerical control system should be checked in time

The change of system parameters will directly affect the function of the machine tool, and even cause the machine to have defects and the whole machine can not work normally. In the planning and manufacturing of CNC system, although the reliability of the system has been considered, it is impossible to sweep all the external disturbances, which may cause the changes of single parameters in the memory. At the same time, it is possible to change the parameters of the stable system by human error. The author has encountered that the stable system behaves abnormally due to the wrong operation. Therefore, in the process of diagnosing defects, it is assumed that the above methods are checked