PLC programming for special machine construction: Best practices and tips
PLC programming (programmable logic controller) is the heart of every modern special machine. Especially in special machine construction, where no system is like another, flexible, clean, and future-proof programming is crucial for function, efficiency, and maintainability. In this blog post, we provide you with practical tips and proven methods to take your control programs to the next level.
1. Structured program design
A well-structured PLC program not only facilitates commissioning but especially troubleshooting and later expansions. Therefore, use:
- Clearly named program blocks (FCs, FBs, OBs)
- Modular programming: e.g., custom blocks for axes, sensors, HMI, etc.
- Global constants and symbol tables to manage values centrally
2. Commenting and documentation
- Documentation is often underestimated but saves time and nerves in the long run:
- Comments directly in the code: short but clear
- Function description for each block
Overview of interfaces (inputs and outputs, variables)
This is especially essential for special machines that will be maintained or expanded later.
3. Use of libraries and standards
Use your own or manufacturer libraries, for example for:
- Drive technology (Siemens DriveLib, SEW function blocks)
- Safety functions
- Communication (e.g., OPC UA, Modbus)
This saves time, improves quality, and ensures reusability.
4. Simulation and testing on site prevent errors
Use simulation functions (e.g., PLCSIM from Siemens) to test programs before loading them onto real hardware. This saves time during commissioning and helps eliminate major errors in advance.
5. Flexible error handling and diagnostics
Implement clean error management from the start:
- Grouped fault messages
- Acknowledgment logics
- Error history (FIFO memory, ring buffer)
- Clear-text error messages for the HMI
This makes everyday life easier for operators and service technicians!
6. Practical tip: Plan HMI and PLC hand in hand
Many programmers treat the HMI (user interface) separately from PLC programming. However, both sides benefit from:
- Common symbol names and structures
- Central text lists for error messages
- Status overviews for machine modes, cycles, etc.
An integrated approach leads to a coherent user experience.
Conclusion
PLC programming in special machine construction is demanding, but manageable with the right approach. Structure, reusability, simulation, and clean error handling are the keys to a maintenance-friendly and robust control program.
If you want to implement your PLC projects professionally or need support in control cabinet construction, feel free to contact us!