Improved Troubleshooting Techniques for Siemens PLCs: Solutions and Challenges

Question:

Greetings, friends! As a pre-development engineer at Siemens, my work involves a combination of mathematical algorithms and practical tasks. Lately, I have been troubleshooting PLCs with real machines, such as montage stations, which can be quite challenging. There are a few common frustrations I encounter in this process: Firstly, having to manually click through multiple buttons to repeat a test can be time-consuming. Secondly, encountering unpredictable failures that are hard to recreate can be frustrating. Despite having tools like TIA Portal Trace, the support for signals and data length can be limited. Even with recording functions, debugging can still be a challenge. To address these issues, I have developed a functional code to save DB data in each PLC cycle. While solutions like SPS or IBA recorders exist, they may not be comprehensive or cost-effective. I believe many automation engineers share similar experiences. As I work on enhancing future Siemens products, I would love to hear your stories and suggestions. Thank you for your input.

Top Replies

Are you wondering about the functions you should use in your program? One thing to be aware of is that MOVE blocks may have ENO enabled by default, allowing the program to continue processing during the move. Additionally, using a 10ms timer may cause a 1-2 scan cycle delay if execution is not optimal. It's important to differentiate between SR and RS usage, as selecting the wrong one could yield the opposite result desired. Make sure to consider these factors when programming.

It is essential to incorporate alarms in the PLC system to detect potential hardware errors. In the case of functional errors, such as program bugs, there are methods to identify and address them. One way is to monitor the PLC online during operation by examining the code directly or using watch tables. Another effective approach is to observe the simulated PLC code using tools like Trace. If there are unexpected error situations and continuous online monitoring is not possible, Trace can provide valuable information for troubleshooting. This data can be used to recreate scenarios through simulation. Prior to commissioning, conducting extensive PLC simulations can help debug the program significantly, potentially resolving up to 95% of issues before initiating machine operations. Overall, implementing these strategies can optimize the performance and reliability of the PLC system.

JesperMP emphasized the importance of having alarms integrated into the PLC system to detect any potential hardware errors. In the event of functional errors in the code, it is essential to troubleshoot by observing the PLC online during operation or using simulated PLC code. Trace can be a valuable tool for identifying and resolving spurious error situations when offline monitoring is not possible. Prior to commissioning, thorough PLC simulation can help debug the program significantly, ensuring smoother machine startup. In response to Jesper's feedback on Siemens products, it is acknowledged that errors may arise from "corner cases" or unforeseen user operations. Monitoring online may not always be feasible, especially with competing tasks and meetings. To address this, a more advanced version of Trace is proposed to monitor all tag values and invoked subroutines at the end of each PLC cycle for extended periods. This detailed record could then be utilized in TIA Portal PLCSIM for effective troubleshooting and bug fixing, although approval from superiors may be necessary for implementation.

Puddle inquired about the functions being used and the intention behind them. One common issue I encountered early on was the default setting of ENO in MOVE blocks, causing the program to continue running during the move process. Additionally, a 10ms timer may result in a delay of 1-2 scan cycles if execution is not optimal. It is important to differentiate between SR and RS usage as selecting the wrong one could yield the undesired outcome. Hi, Puddle, I agree with your observation. This approach may be functional but may not be sufficient to address all issues effectively.

In the past, before the advent of trace technology, software developers often resorted to setting "traps" to detect rare events. This method proved crucial in identifying a profibus data consistency error and confirming its resolution.

I completely relate to the woes of navigating through PLC issues! Working as an automation engineer myself, I've grappled with the same bugbears. I absolutely agree that the signal support and data length given by the TIA Portal Trace are insufficient; it's a periodic gripe for many of us in the industry. Your functional code approach is innovative, but have you considered collaborating with software developers to create a user-friendly interface? This might simplify the process further by lessening manual button pressing to repeat tests, saving developers valuable time. I appreciate your initiative to create a more comprehensive and cost-effective alternative to existing solutions!

I relate to your experience as I've been an automation engineer for a few years now. I agree, despite all the advancements, PLCs can still be a pain to troubleshoot. Manual testing is indeed time-consuming. Your innovative solution of developing functional code to save DB data in each PLC cycle is impressive and seems immensely beneficial in tracking issues more efficiently. One recommendation that could enhance your approach would be to automate the testing process as much as possible. For instance, using scripts to simulate user inputs could help save time. Also, leveraging AI for predictive maintenance could aid in eliminating unexpected failures by identifying potential problems before they occur. Integration of such systems could certainly be a step forward. Thanks for bringing up this conversation!

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Frequently Asked Questions (FAQ)

FAQ: 1. What are some common frustrations faced when troubleshooting Siemens PLCs with real machines?

Answer: Some common frustrations include the time-consuming nature of manually clicking through multiple buttons to repeat tests and encountering unpredictable failures that are hard to recreate.

FAQ: 2. What limitations are often encountered when using tools like TIA Portal Trace for troubleshooting PLCs?

Answer: The support for signals and data length can be limited, and despite having recording functions, debugging can still poses challenges.

FAQ: 3. How can the challenges of troubleshooting Siemens PLCs be addressed?

Answer: One approach is to develop functional code to save DB data in each PLC cycle. Additionally, exploring solutions like SPS or IBA recorders, while considering their comprehensiveness and cost-effectiveness, can be beneficial.

FAQ: 4. How can automation engineers contribute to enhancing future Siemens products?

Answer: Automation engineers can share their experiences, stories, and suggestions with Siemens to help improve troubleshooting techniques and develop more efficient and effective products.

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