Commonly diagnosed methods for electrical faults of CNC machine tools

The process of investigation, analysis, and diagnosis of the faults in the electrical system of CNC machine tools is also the troubleshooting process. Once the cause is identified, the fault is almost equal to the elimination. Therefore, the method of fault diagnosis and diagnosis becomes very important. Common diagnostic methods are summarized as follows:

(1) Visual inspection This is the method that must be used at the beginning of the fault analysis. It is to use sensory inspections.

1 Inquiry Ask the fault site personnel to carefully inquire about the process of fault occurrence, fault appearance, and the consequences of the fault, and may ask for multiple inquiries during the entire analysis.

2 Visually check whether the working status of each part of the machine tool is in a normal state (such as the position of each coordinate axis, spindle status, magazine, robot position, etc.). Each electronic control device (such as numerical control system, temperature control device, lubrication device, etc.) has No alarm indication, partial inspection with or without insurance calcined, components burned, cracking, wire and cable drop, the correct position of the operating elements and so on.

3Touching can be found under the condition of power failure of the whole machine by touching the installation status of each main circuit board, the plugging status of each plug connector, and the connection status of each power and signal wire (such as servo and motor contactor wiring). The cause of the failure.

4 Power On This is to check whether there is smoke, ignition, presence of abnormal sound, odor, and presence of overheated motors and components.

(2) Instrument inspection method Use conventional electrical instruments to measure the AC and DC power supply voltages of each group and measure the relevant DC and pulse signals to find possible faults. For example, check the condition of each power supply with a multimeter, and measure the relevant signal state measurement points set on some circuit boards. Use an oscilloscope to observe the amplitude and phase of the related pulse signals. Use PLC programmer to find the PLC program. Fault location and causes.

(3) Signal and alarm indication analysis

1 Hardware alarm indication This refers to various status and fault indicators on various electronic and electrical devices, including the CNC system and servo system. Combined with indicator status and corresponding function descriptions, the indication content and cause and exclusion of the fault can be obtained. method.

2 Software Alarm Indication The faults in the system software, PLC program and machining program mentioned above are usually equipped with an alarm display. According to the displayed alarm number, the corresponding diagnosis instruction manual can be used to know the possible fault causes and troubleshooting methods.
(4) Interface status inspection method Modern CNC systems integrate PLCs into them, while CNC and PLC communicate with each other through a series of interface signals. Some faults are related to the signal error or loss of the interface. Some of these interface signals can be displayed on the corresponding interface board and input/output board, and some can be displayed on the CRT screen through simple operations. All interfaces Signals can be called up using the PLC programmer. This inspection method requires the maintenance personnel to be both familiar with the interface signals of the machine tool and to be familiar with the application of the PLC programmer.

(5) The parameter adjustment method The numerical control system, PLC and servo drive system all set many modifiable parameters to meet the requirements of different machine tools and different working conditions. These parameters not only enable the electrical systems to match the specific machine tools, but they are also necessary to optimize the machine tool functions. Therefore, any change of parameters (especially the analog parameters) or even the loss is not allowed; and the mechanical or electrical performance changes caused by the long-term operation of the random bed will break the initial matching state and the optimization state. This kind of fault refers to the latter type of fault in the fault classification section. It is necessary to readjust the relevant one or more parameters before troubleshooting. This kind of method is very high to the maintenance personnel's request, not only must understand the main parameter of the specific system very well, knows its address to be familiar with its function, moreover must have the rich electric debugging experience.

(6) Spare part replacement method When the fault analysis result is concentrated on a certain printed circuit board, it is very difficult to implement the fault on an area or even a certain component due to the continuous expansion of the circuit integration degree. During the downtime, the spare parts can be replaced with the same spare parts, and then the failed board can be checked and repaired. Replace the spare board with the following issues.

1 Replacement of any spare parts must be done in the event of a power failure.

2 Many printed circuit boards have some switch or shorting bar settings to match the actual needs, so be sure to record the original switch position and setting status on the replacement spare board and make the new board the same Set, otherwise an alarm will be generated and it will not work.

3 Some printed circuit board replacements also require certain operations after the replacement to complete the establishment of software and parameters therein. This requires careful reading of the corresponding board's instructions for use.

4 Some printed circuit boards cannot be easily removed, such as a board containing a working memory, or a spare battery board, which loses useful parameters or programs. When must be replaced, follow the instructions.
In view of the above conditions, please carefully read the relevant information before you remove the old board and replace it with new ones to understand the requirements and the operation steps before proceeding, so as to avoid causing a greater failure.

(7) Cross-crossing method When the fault board is found or the fault board cannot be determined and there is no spare part, the same or compatible two boards in the system can be checked interchangeably, for example, two coordinate command boards or servos The exchange of the board determines the fault board or fault location. This crossover method should pay special attention to not only the correct exchange of hardware wiring, but also a series of corresponding parameters exchange, otherwise not only fail to achieve the purpose, but will produce new failures caused confusion of thinking, must be fully considered in advance , design a good software and hardware exchange program, accurate and then exchange inspection.

(8) Special handling methods Today's CNC systems have entered the PC-based, open development stage, in which the software content is more and more abundant, there are system software, machine tool builder software, and even the user's own software, due to the software logic Some problems that are unavoidable in the design will make it impossible to analyze some of the fault conditions, such as crashes. For this kind of failure phenomenon, special measures can be taken to deal with it, such as the power failure of the whole machine, restart after a pause, and sometimes the failure may be eliminated. Maintenance personnel can explore their laws or other effective methods in their own long-term practice.