With the development of manufacturing automation and enterprise informatization, enterprises are increasingly demanding the automatic collection of manufacturing information, and the manufacturing information of workshop equipment is urgently needed to provide basis for production management and decision-making. The real-time data acquisition system of CNC machine tools can not only provide timely and accurate operation of CNC machine tools, but also provide accurate and reliable technical data for scientifically preparing production plans and provide timely, reliable and accurate reference information for production and operation decisions for the upper system. However, with the formation of the data acquisition network, some new CNC machine tools have also appeared. Some CNC machine tools using Siemens 840D CNC system (configured with PCU50, HMI software) have run the CAXA data acquisition software for a period of time, and the CNC system running speed is too slow. The system enters the state of false death, which causes the machine to fail to work normally.
Problem analysis
First of all, it is suspected that because of the use of CAXA's data acquisition software, the use of CNC system resources is too large, which in turn affects the operating speed of the CNC system. In order to confirm this problem, a certain machine tool was selected for experimentation, and this failure phenomenon still occurred without starting the data acquisition software. Therefore, problems with CAXA's data acquisition software can be eliminated.
Secondly, it is suspected that the hardware configuration of the CNC system is low. After running the CAXA data acquisition software, the system hardware cannot provide sufficient operating resources. Start the Windows Task Manager to see the CPU and memory usage under normal operating conditions. As can be seen from Figure 1, after running CAXA data acquisition software, the CPU and memory usage are small. Therefore, the hardware configuration problem of the numerical control system can be eliminated.
2. Troubleshooting and solving
The HMI software of the Siemens 840D CNC system runs in the Windows XP environment. Therefore, when analyzing the problem, you need to consider the operation of Windows. If Windows runs too slowly, it will directly cause the CNC machine system software to run slower.
When the system is running too slowly, start the Windows Task Manager and find that the CPU usage is as high as 100%. Because the CPU usage is too high, the CNC system is running too slowly. Looking at the process, I found that Svchost.exe reached 99.01% with CPU. Svchost.exe is a system program belonging to the Microsoft Windows operating system. Different versions of Windows have different numbers of "Svchost" processes, and WINXP has four or more Svchost processes.
With the increasing number of Windows system services, in order to save system resources, Microsoft has made many services into a shared mode, which is started by the Svchost.exe process. However, the Svchost.exe process is only a service host and does not implement any service functions. That is, it can only provide conditions for other services to be started here, but it cannot provide any services to users. These system services are implemented in the form of dynamic link libraries (DLLs) that point executable programs to Svchost, and Svchost calls the dynamic link library of the corresponding service to start the service.
How to check which services are called by Svchost which takes up a large CPU? At this time, we can use the Process Explorer software. Open the software to view the system services that the Svchost calls. As shown in Figure 2, the Svchost calls a total of 25 system services.
But which services are causing the CPU usage to reach 100%? First of all, we must understand the purpose and significance of these system services. Click on the menu "Start" - "Run", type Services.msc in the text box, a service window will pop up on the desktop (see Figure 3), listing all the services currently running on the system. It can be seen that the "startup type" of some services is set to "automatic", indicating that they all run automatically in the background.
Some of these system services are necessary services for the system to run, while others are not used. Turning on will only waste memory and resources, become the target of virus attacks, and also affect the startup speed and running speed. For some system services that are not in use, they can be set to run manually.
Since the Siemens HMI system software is running in the Windows environment, whether the Siemens system software uses the Windows system service and whether it has an impact on the operation of the Siemens system after stopping these system services cannot be obtained from the existing data. Therefore, it can only rely on experimental tests. Stop these system services one by one and test the system operation.
After a long period of repeated testing, the following system services are eventually stopped: Computer Browser, Cryptographic Services, DHCP Clinet, Distributed Link Tracking Client, Error Reporting Service, Help and Support, Portable Media Serial Number, Secondary Logon, TCP/IP Netbios Helper , Themes, Upload Manager, Wireless Zero Configuration. After stopping these services, the Siemens system is running back to normal and the system running slow is solved.
3. Conclusion
CNC machine tools integrate computer technology, automatic control technology, automatic detection technology and precision machinery into one, involving multidisciplinary knowledge. Therefore, for the technical personnel engaged in numerical control maintenance, it is necessary to have a multi-disciplinary basic knowledge, but also to constantly update the knowledge, to make a good knowledge reserve for dealing with some new CNC machine tool failures.
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