PLC initial fault diagnosis of the hottest machine

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Machine tool PLC initial fault diagnosis

Abstract This paper presents a method of machine tool PLC initial fault diagnosis. When several faults are displayed at the same time, this method can accurately judge the initial fault, so as to improve the efficiency of machine tool maintenance

keywords PLC machine tool maintenance initial fault diagnosis 1 Introduction

in order to protect the machine tool and facilitate maintenance, PLC has the ability to display and detect machine tool faults. Once a fault occurs, the maintenance personnel can determine the fault category and eliminate it according to the fault display number of the machine tool. However, in the actual processing process, we found that sometimes PLC displays several faults at the same time. They are chain faults caused by a certain fault. After the initial fault is eliminated, other fault alarms disappear. However, from all the alarm faults displayed by the machine tool PLC, the maintenance personnel do not know which fault is the initial fault, and the maintenance personnel can only check the faults one by one, which increases the difficulty of maintenance and causes a waste of human and material resources. When several faults are displayed at the same time, the key to deal with the problem is to solve the initial fault, so it is very important for machine tool maintenance to accurately judge and detect the initial fault. We designed an initial fault diagnosis function of machine tool PLC, and accurately judged the alarm number of the initial fault through PLC program. In the maintenance, the initial fault should be eliminated first, and the other faults will disappear by themselves, which greatly facilitates the maintenance of the machine tool and improves the speed and accuracy of the maintenance of the machine tool. 2 principle of initial fault diagnosis

the PLC program we designed can not only detect and display all faults, but also automatically judge the most critical initial faults. The PLC initial fault judgment program is shown in the attached figure. The following is an example to illustrate the principle of initial fault diagnosis. Taking three faults as an example, three fault detection bits are set in the process of clamping the sample (or product) by the fixture to apply force to the sample, which are r500.0, r510.0 and r520.0 respectively; The three initial fault detection bits are r500.2, r510.2 and r520.2; F149.1 is the system reset signal. In the initial state, no alarm occurs, the fault detection bits are all "0", the initial fault detection bits are also "0", and the reset signal f149.1 is "0". Among the three faults, it is assumed that the second fault occurs first. In the first cycle of program scanning, its corresponding fault detection bit r510.0 becomes "1", the initial value of r500.2, r520.2 and f149.1 is "0", the initial fault detection bit r510.2 becomes "1", and it is maintained as "1" through self-locking. The "1" state is not released until the fault is eliminated and the system reset signal is sent. In the second cycle of program scanning, r510.2 remains "1", realizing the blocking of r500.1 and r520.1. Even if another fault detection bit is "1", its initial fault detection bit cannot be changed to "1". Through the control of this PLC program, the initial fault can be accurately judged from the numerous faults that occur at the same time. 3 application example

example 1 when we were repairing the jcs018 CNC machine tool produced by Beijing Machine Tool Research Institute, we encountered the problem of multiple faults occurring at the same time, such as the simultaneous occurrence of tool change alarm and hydraulic alarm. During maintenance, we usually start from the root cause of the fault, check the hydraulic control part first, and then continuously improve the system energy efficiency before we can confirm that the fault is in the process of tool change. Only after inspection did we know that the power of tool changing was provided by hydraulic drive. In the design of PLC control program, in order to prevent greater accidents when a tool change fault occurs, the hydraulic control is also disconnected at the same time of the alarm, so two alarm messages appear when a tool change fault occurs. In order to follow the design idea of the original machine tool and send out alarm information accurately, we have added the function of checking initial faults to jcs018 CNC machine tool. According to the analysis of the previous procedure, the tool change and hydraulic fault detection bits are r500.0 and r510.0 respectively, and the initial fault can be read out from the initial fault detection bit R5 white pollution can turn into green environmental protection products 00.2 and r510.2. When a similar fault occurs to the machine tool again, the initial fault can be quickly judged

example 2 we encountered a similar phenomenon when repairing a drilling and milling machining center. The machine tool is equipped with a tool magazine with a tool capacity of 40 tools, which can automatically complete the drilling and milling operation of multiple processes. The spindle motor of the machine tool is a three-phase asynchronous motor, and the spindle motor has only one speed, while the spindle realizes 12 level speed change through gear speed change. When a certain program is automatically executed, the auxiliary functions in the program include both shift function s code and tool finding function T code. As long as a code fails to execute the instructions of entrepreneurs who lack technical resources, the auxiliary function completion signal cannot be sent, that is, the auxiliary function in this program is not completed, and the next program segment cannot be executed. If the shift function fails, the shift alarm signal is sent first, and the signal cannot be sent after the auxiliary function is completed. After a certain time, the knife search alarm signal is sent again, it will be considered that the knife search action has not been completed. If the initial fault judgment function is added, the maintenance personnel will accurately check the cause of the fault and solve the problem in time. 4 Conclusion

the initial fault detection function of machine tool PLC designed by us can accurately judge the initial fault when several faults are displayed at the same time, which brings great convenience to machine tool maintenance, avoids many meaningless jobs, and improves maintenance efficiency. It has achieved good results in practical application. About the author: Liang Ruoqiong, CNC Engineering Center of Beijing Machine Tool Research Institute, No. 4, Wangjing Road, dongzhimenwai, Chaoyang District, Beijing (doctoral student of central China University of technology, zip code: 100102

author unit: Central China University of technology references

1 sun Tongjing Application technology of programmable controller Jinan: Shandong science and Technology Press, 1995

2 Bi Chengen, Ding Naijian, etc Modern CNC machine tools Beijing: China Machine Press, 1991

3 Zhong Zhaoxin et al Principle and application of programmable controller Guangzhou: South China University of Technology Press, 1992

4 zhushanjun Principle, application and maintenance of programmable control system Beijing: Tsinghua University Press, 1992

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