PLC control machine design and maintenance with CNC axis - Database & Sql Blog Articles

In the design and use of machine tools, it is often encountered that there is a higher precision requirement in a certain station, and other stations adopt plc control to be more convenient and economical. How to combine the flexibility of PLC control with the high machining accuracy of CNC system to form a system that is economical and reliable and meets the requirements of machining accuracy of parts. Such systems are often encountered in the control of automated machine tools.

1. The system block diagram is controlled by the PLC, and a separate CNC system (taking the CLM CNC system as an example) at a certain station, and the necessary signal exchange with the PLC. Since it is only a CNC axis, the main control system is also controlled by PLC. The action commands of the CNC axes are all derived from PLC. The processing and understanding of the exchange signals of the two systems becomes the key to design and maintenance. . State feedback .

2) Setting of system parameters and programming of machining program (taking CLM system switch back to zero as an example) A. Reference point related parameters

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Origin setting A11202 01 00 13 button connected to auxiliary input point #2 Zero switch connected to auxiliary input point #1 Reference point signal to auxiliary output point #13 Motion setting A1100 0 0 1 05 0 01 is forward, speed is 5% offset setting A1111 130.0 Reference point switch relative to the origin position Minimum limit A113 -131.0 (actual limit -1.0) Maximum limit A114 +1800.0 (actual limit +1930.0) B. Parameters related to mechanical parts Feed constant A1086.66667 Encoder per division unit screw moving distance position gain A1031.0 Standard value is 1C. Other parameters #p#Page title#e# Manual speed A10120.0 Acceleration A10250.0 Position deviation A10615 0.05 Direction A1090 1 000000 Operating direction Maximum speed A1212000 0000 Motor maximum speed B00701 03 0 0 00 01 is English 03 is the decimal point 3 digits D. CNC axis machining program E0000JMP 0010 Jump to 0010E0010WAI 02.0 Wait 2 seconds E0011ATS 13 1 Detection auxiliary output #13 (Reference point indication) Bit 1 continues E0012NOPE0013PSA 1 +150.0 200 Fast forward E0014PSA 1 +300.0 011 Slow advance E0015NOPE0016NOPE0017NOPE0018WAI 2.0E0019PSA 1 +0.0 300 Rewind E0020JST 0000 Jump to step 0000, stop Waiting for the next cycle 4. Before the maintenance of common faults, there are 5 machine tools with similar system configuration. Some are CNC axes, some are CNC turntables. The reference point is more accurate, and the encoder is used to determine the zero position. In the process of maintenance, it has encountered many failures related to the numerical control system. 1) Y-axis can not be found in situ, MARKER PULSE 2 on CLM CNC panel? Alarm analysis: reference point search step, first touch the reference point switch, then find the zero pulse of the encoder (the specific action of the reference point is specifically designed) And there is a difference). The fault stops and alarms when it hits the reference point switch. According to the prompt, the problem lies in the encoder and its connection. Solution: After inspection, the water at the connector of the encoder is filled with water. After cleaning, it is blown clean with an air gun. 2) The market has been turning forward, and the analysis cannot be found in the original position: the reference point is first turned forward, and after the home position switch is touched, the inverter starts to reverse, and the home position switch is started to find the encoder zero pulse. The fault is obviously that the reference point switch does not respond. Solution: Check the home switch and it will be normal after replacement. 3) Find the in-situ large-scale reversal solution: According to the above analysis, it is estimated that the home position switch is normally set to 1, check the switch signal to prove that the judgment is correct, remove the switch, the internal water inlet causes the signal to be short-circuited, and returns to normal after cleaning. 4) Siemens driver board "6" alarm, system jumps, and then CLM alarm "DRIVE RUNAWAY A1" appears. Analysis: The electrical system is a PLC controlled machine tool. The station consists of two CNC axes. The CNC system is CLM dual-axis CNC. The drive and motor are Siemens. The "6" alarm of the engine board is "Speed ​​controller at endstop, Iact=Iset". The common fault is the limit. Solution: noticed that the system inverter power supply jumped, and after the line inspection, it was found that the hard limit of the X-axis was encountered during the in-situ process. After the external movement was 5mm, the power supply was not jumped, and it could be found in the original position, but In the process of automatic execution, the "6" alarm appears on the engine board, and the alarm "DRIVE RUNAWAY A1" appears on the CLM system panel. According to the alarm, the fault is still on the X axis. According to experience, the reference point is searched normally, and the machine stops during the automatic process, which may be poor signal contact. In the case where the motor, the connecting line, and the encoder are all proven to be OK, the fault finding is in a difficult situation. After the extension of the hard limit, the relative position of the reference point will be deviated. After the reference point offset A111 is reduced, the fault disappears immediately, and then the position is adjusted to work normally, and the device returns to normal. Through the above examples of fault repair, it can be seen that only on the basis of clear understanding of the specific actions of the control system and the machine tool, according to their own professional knowledge and experience, effective analysis and judgment can be carried out. For control systems consisting of multiple subsystems, the interface between systems is the key to design and maintenance. 5. Conclusion In the design and use of machine tools, it is often not limited to an electrical system, but a new machine control system composed of various types of systems. This phenomenon is more common, the combination of CNC axes and PLC control. It is a typical example. Combine your own practice in design and maintenance, and welcome experienced professionals to exchange corrections.