For many years, modernising industrial automation systems was seen as a purely technical activity: upgrade controllers, add a few sensors, improve throughput. Today it is becoming a strategic decision. The quality of a modernisation project directly influences not only process efficiency, but also data security, future scalability, and ultimately the competitiveness of the entire factory. Yet the same three mistakes keep reappearing across industries - sometimes even in highly advanced plants.
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1. Upgrading "blindly", without a proper diagnosis
Surprisingly, many organisations begin their modernisation journey with... a purchasing list. New PLC - check. Faster HMI - check. New field devices - check. But replacing hardware does not necessarily solve the bottlenecks of the process. In many cases, once the upgrade is completed, performance gains are marginal while project costs remain significant.
The missing step is almost always a thorough assessment of the current state. Quite often, better logic, tuned PID loops or improved communication between subsystems would yield more noticeable improvements than brand-new hardware. Modernising without a diagnostic phase is like repairing a roof without checking the trusses - the first storm usually reveals what was overlooked.
2. Treating cybersecurity as "someone else's problem"
Another widespread mistake is modernising strictly within the OT domain while leaving IT and security teams out of the loop. With modern automation being directly connected to MES platforms, reporting tools and sometimes cloud services, production systems are increasingly exposed to cyberthreats. A targeted attack can stop a production line faster than any mechanical failure.
Typical oversights include flat network architectures, remote access left with default credentials "just for now", or VPN tunnels configured without segmentation. Basic security practices - role-based access, zoning, hardened endpoints - cost a fraction of what an actual incident might.
In a well-designed project, cybersecurity is not a "plug-in", but an integral function of the system, just like physical safety circuits.
3. Designing only for today - neglecting scalability
Many modernisation projects still assume that the system will remain static: once installed, it should run untouched for years. In reality, production strategies evolve rapidly. Capacity is increased, new SKUs are introduced, and analytics requirements grow.
The most expensive mistake is choosing components or architectures that barely fit today’s needs and leave no room for expansion: PLCs with no spare I/O, enclosures with no space for extra modules, proprietary software locking out integration. What looks like a saving at the start almost always becomes a forced “second modernisation” shortly afterwards - far more costly and disruptive.
Designing for the future doesn’t mean oversizing everything. It means providing open interfaces, modular architecture and some headroom for growth.
Why do these mistakes persist?
All three stem from the same root cause: technology is often treated as a goal in itself rather than a long-term enabler of business value. Proper modernisation is not a procurement task - it is a lifecycle investment. Success depends more on governance and engineering discipline than on which PLC model is chosen.
When planning includes a structured assessment, a security-by-design approach and a roadmap for future extensions, modernisation ceases to be a reactive cost centre. It becomes a strategic advantage: faster changeovers, better reliability, smoother integration - and the freedom to evolve without downtime.
