How to eliminate the faults of the hottest automat

2022-08-16
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How to troubleshoot automatic machine tools

automatic machine tools are important equipment for factory production, which are widely used in various industries. Then the failure of automatic machine tools will have a very serious impact on the production of enterprises and cause great losses. Therefore, the troubleshooting of automatic machine tools is very important, which can be divided into two steps

I. fault investigation and analysis

the following is a summary of the common diagnostic methods of gas fault, which are often neglected by electric people when purchasing experimental machines

(1) visual inspection method, which is a necessary method at the beginning of fault analysis, is to use sensory inspection

① ask the fault site personnel carefully about the process of fault generation, fault appearance and fault consequences, and may ask many times in the whole process of analysis and judgment

② visually check whether the working state of each part of the machine tool is normal (such as the position of each coordinate axis, the state of the spindle, the position of the tool magazine, the manipulator, etc.), whether each electric control device (such as the numerical control system, the temperature control device, the lubrication device, etc.) has an alarm indication, and locally check whether there is a fuse burning, components burning, cracking, wires and cables falling off, whether the position of each operating element is correct, whether the gantry mechanism column is z-axis, etc

(2) instrument inspection method uses conventional electrical instruments to measure the AC and DC power supply voltages of each group and the relevant DC and pulse signals, so as to find possible faults. For example, check the power supply with a multimeter, measure the relevant signal status measurement points set on some circuit boards, observe the amplitude, phase and even presence of relevant pulsating signals with an oscilloscope, and use a PLC programmer to find the fault location and cause in the PLC program

(3) signal and alarm indication analysis method

① hardware alarm indication refers to various states and fault indicators on electronic and electrical devices, including numerical control system and servo system. Combined with the status of the indicator and the corresponding function description, you can know the indication content, fault causes and troubleshooting methods

② software alarm indication as mentioned above, the faults in system software, PLC program and processing program are usually equipped with alarm display. According to the displayed alarm number, the possible fault causes and troubleshooting methods can be known by comparing with the corresponding diagnostic instruction manual

(4) interface state inspection method modern CNC systems mostly integrate PLC into them, and CNC and PLC communicate with each other in the form of a series of interface signals. Some faults are related to the error or loss of interface signals. Some of these interface signals can be displayed on the corresponding interface board and input/output board, some can be displayed on the CRT screen through simple operation, and all interface signals can be called out by PLC programmer

(5) parameter adjustment method NC system, PLC and servo drive system all set many modifiable parameters to meet the requirements of different machine tools and different working states. These parameters can not only match the electrical system with the specific machine tool, but also are necessary to optimize the functions of the machine tool. Therefore, any parameter change (especially analog parameter) or even loss is not allowed; The mechanical or electrical performance changes caused by the long-term operation of the random bed will break the initial matching state and optimization state. This kind of fault mostly refers to the latter type of fault in the fault classification section, which can be eliminated only after readjusting one or more relevant parameters

(6) spare parts replacement method when the fault analysis results are concentrated on a printed circuit board, it is very difficult to implement the fault in a certain area or even a certain component due to the continuous expansion of circuit integration. In order to shorten the downtime, under the condition of having the same spare parts, you can replace the spare parts first, and then check and repair the faulty board

in view of the above conditions, before pulling out the old board and replacing it with a new one, be sure to carefully read the relevant materials, understand the requirements and operation steps, and then start to work, so as to avoid causing greater faults

(7) cross transposition method when a faulty board is found or it cannot be determined whether it is a faulty board and there are no spare parts, the same or compatible two boards in the system can be interchanged for inspection, such as the exchange of command boards or servo boards of two coordinates, from which the faulty board or fault location can be determined. This kind of cross exchange should immediately open the oil return pump and unload the sample. Special attention should be paid to the position method. It is not only the correct exchange of hardware wiring, but also the exchange of a series of corresponding parameters. Otherwise, it will not achieve the goal, but will produce new faults and cause confusion of thinking. We must consider thoroughly in advance, design the software and hardware exchange scheme, and conduct the exchange inspection again after it is accurate

(8) special treatment today's CNC system has entered the PC based and open development stage, in which the software content is more and more abundant, including system software, machine tool manufacturer software, and even the user's own software. Due to some inevitable problems in the design of software logic, some fault states cannot be analyzed, such as crash. For this kind of fault phenomenon, special measures can be taken to deal with it. For example, the whole machine is powered off, and then started after a pause. Sometimes, the fault may be eliminated. Maintenance personnel can explore its rules or other effective methods in their long-term practice

this is the first stage of troubleshooting, which is a very critical stage. The following work should be done:

1. Inquiry and investigation. When receiving the information of troubleshooting on the machine tool site, the operator should first be required to maintain the on-site fault state as far as possible without any treatment, which is conducive to the rapid and accurate analysis of the cause of the fault

2. After the on-site inspection arrives at the site, first verify the accuracy and integrity of various situations provided by the operator, so as to verify the accuracy of the preliminary judgment. Due to the level of the operator, there are many cases of unclear or even completely inaccurate description of fault conditions, so don't rush to deal with it after arriving at the scene, and re investigate all kinds of conditions carefully, so as not to damage the scene and increase the difficulty of troubleshooting

3. Fault analysis according to the known fault conditions, analyze the fault type according to the fault classification method described in the previous section, so as to determine the troubleshooting principle. Since most faults are indicated, generally speaking, the modified plastic has a huge market in the field of automobile manufacturing according to the diagnosis manual and operation manual of the CNC system supporting the machine tool, and a variety of possible causes of the fault can be listed

4. Determine the cause, troubleshoot a variety of possible causes, and find out the real cause of the fault. At this time, it is a comprehensive test for the maintenance personnel on the familiarity, knowledge level, practical experience and analysis and judgment ability of the machine tool

5. Troubleshooting preparation. Some troubleshooting methods may be very simple, while some faults are often more complex. A series of preparations need to be done, such as the preparation of tools and instruments, local disassembly, parts and components repair, component procurement, and even the formulation of troubleshooting plan steps

II. Electrical maintenance and troubleshooting

the analysis process of electrical faults is also the troubleshooting process. Therefore, some common troubleshooting methods of electrical faults have been comprehensively introduced in the analysis methods of the previous section. This section lists several common electrical faults for a brief introduction for the maintainer's reference

1. Power supply is the energy source for the normal operation of the maintenance system and even the whole machine tool. Its failure or slight failure will cause data loss and shutdown. In severe cases, the system will be damaged partially or even completely. Due to sufficient power and high power quality in western countries, less consideration is given to the power supply design of their electrical system, which is slightly insufficient for China's power supply with large fluctuations and high-order harmonics. Coupled with some human factors, it is inevitable that faults caused by power supply will occur

2. CNC system position ring fault

① position ring alarm. The position measurement circuit may be open; The measuring element is damaged; The interface signal established by position control does not exist, etc

② the coordinate axis moves without instructions. It may be that the drift is too large; The position loop or speed loop is connected into positive feedback; The feedback wiring is open; The measuring element is damaged

3. The zero point cannot be found in the machine coordinate. It may be that the zero direction is far away from zero; The encoder is damaged or the wiring is open; Grating zero mark shift; The zero return deceleration switch fails

4. The dynamic characteristics of the machine tool become worse, the processing quality of the workpiece decreases, and even the machine tool vibrates at a certain speed. There is a great possibility that the clearance of the mechanical transmission system is too large or even seriously worn, or the guide rail lubrication is insufficient or even worn; For the electrical control system, it may be that the speed loop, position loop and related parameters are no longer in the best matching state, and the optimization adjustment should be carried out again after the mechanical fault is basically eliminated

5. Accidental shutdown fault. There are two possible situations here: one is that the problems in the relevant software design as mentioned above cause the shutdown failure under some specific operation and function operation combinations. Generally, the machine tool will disappear after being powered on again after being powered off; The other is caused by environmental conditions, such as strong interference (electricity or peripheral equipment), excessive temperature, humidity, etc. Such environmental factors are often ignored by people. For example, in the south, machine tools are placed near ordinary workshops or even close to open doors, electric cabinets are opened for a long time, and there are a large number of equipment producing dust, metal chips or water mist nearby. These factors will not only cause failures, but also seriously damage the system and machine tools. We must pay attention to improvement

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