1 Introduction
In order to protect the machine and to facilitate maintenance, the PLC has the ability to display and detect machine faults. In the event of a malfunction, the maintenance personnel can determine the fault category based on the fault display number of the machine tool and eliminate it. However, in the actual processing, we found that sometimes the PLC displays several faults at the same time. They are cascading faults caused by one fault, eliminating the initial faults, and 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 one by one, which increases the difficulty of maintenance and wastes manpower and material resources. When several faults are displayed at the same time, the key to solving the problem is to solve the initial fault, so it is very important to accurately judge and detect the initial fault to the machine repair work. We designed a machine tool PLC initial fault diagnosis function, through the PLC program, accurately determine the initial fault alarm number. In the maintenance, the initial fault is first eliminated, and other faults are eliminated by themselves, which greatly facilitates the maintenance of the machine tool and improves the speed and accuracy of the machine tool repair.2 Principle of initial fault diagnosis
The PLC program we designed not only can detect and display each fault, but also automatically judge the most critical initial fault. The initial fault judgment procedure of PLC is shown in the figure.
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The following is an example of the initial fault diagnosis principle. Taking three faults as an example, three fault detection bits are set, which are R500.0, R510.0, and R520.0 respectively; 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 bit is "0", the initial fault detection bit is also "0", and the reset signal F149.1 is "0". It is assumed in the three failures that the second failure occurs first. In the first cycle of the program scan, its corresponding fault detection bit R510.0 becomes "1", R500.2, R520.2, F149.1 initial value is "0", initial fault detection bit R510.2 It becomes "1" and remains "1" by self-locking until the fault is eliminated, and the "1" state is released after the system reset signal is issued. In the second cycle of the program scan, R510.2 remains "1", which realizes the blocking of R500.1 and R520.1. Even if another fault detection bit is "1" at this time, it cannot cause it. The initial fault detection bit becomes "1". Through the control of this PLC program, the initial fault can be accurately determined from the numerous faults occurring at the same time.
3 application examples
- Example 1 When we repaired the JCS018 CNC machine tool produced by Beijing Machine Tool Research Institute, we encountered several problems at the same time, such as tool change alarm and hydraulic alarm. When repairing, we generally check the source of the fault, first check the hydraulic control part, and then confirm that the fault is in the process of changing the tool. After the inspection, we learned that the power of the tool change was provided by the hydraulic drive. In the PLC control program design, when a tool change failure is encountered, in order to prevent a larger accident, the hydraulic control is also disconnected at the same time as the alarm, so two alarm messages appear when the tool change occurs. In order to follow the design idea of ​​the original machine tool and accurately issue the alarm information, we added the inspection function for the initial fault to the JCS018 CNC machine tool. According to the previous program analysis, the tool change and hydraulic fault detection bits are R500.0 and R510.0, respectively, and the initial fault can be read from the initial fault detection bits R500.2 and R510.2. When the machine has a similar failure, the initial failure can be quickly determined.
- Example 2 We encountered a similar phenomenon when repairing a drilling and milling center. The machine is equipped with a tool magazine with a tool capacity of 40 knives, which can automatically complete the drilling and milling operations of multiple processes. The spindle motor of the machine tool is a three-phase asynchronous motor. The spindle motor has only one type of rotation speed, and the main shaft realizes 12-stage step-variable speed change by gear shifting. When a certain program is executed automatically, the auxiliary function in the program has both the shift function S code and the tool search function T code. As long as one code command is not executed, the auxiliary function can not be sent after the signal is completed. The auxiliary function in the program is not completed and the next block cannot be executed. If the shift function fails, the shift alarm signal will be issued first, and the auxiliary function signal will not be sent. After a certain time, the tool seek alarm signal will be issued, and the knife-finding action will not be 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 the machine tool PLC designed by us can accurately judge the initial fault caused when several faults are displayed at the same time, which brings great convenience to the maintenance of the machine tool, avoids many meaningless work and improves the maintenance efficiency. . Good results have been achieved in practical applications.C9 Petroleum Resin,C9 Petroleum Resin for Adhesive,C9 Catalytic Petroleum Resin
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