01
Many beginners learning PLC programming think like this: “As long as the functionality is achieved,” “Getting it to run is the most important thing,” “Just pile it up first, and optimize later.”
What’s the result? The program can run. But when you need to modify it, you find yourself confused. You can’t even find the logic you wrote, let alone optimize it.
It’s not that the functionality is wrong, but that the foundation is not solid.You think you are writing a program, but in reality, you are just piling up garbage.
02
PLC is not a universal glue; the more you stick, the messier it gets, and when problems arise, you can’t just pull it out.
If you don’t pay attention to structure and just stack function blocks, conditions, and temporary variables, it may seem “great” at first, but later it becomes “really painful.”
Why? Because:A program without logical structure is like a body without a skeleton—once it moves, it falls apart.
When you try to modify it, you realize that for every line of logic you add, you have to check dozens of cross-references; every time you change a variable, the entire area shakes. A simple requirement change can affect dozens of OBs and FBs, making it unclear who controls whom and who is influenced by whom.
You are not developing a system; you are creating “chain bombs.”
03
You need to understand:The primary principle of PLC programming is not to complete functionality, but to design a clear logical structure.
What is structure? It is hierarchy, boundaries, division of responsibilities, and an architecture that can be clearly seen at a glance.
A truly mature PLC program has a complete thought process from top to bottom— 1 main OB controls the flow; multiple sub-modules each perform their duties; input and output units are independently isolated; alarms, communication, control, and interfaces are each distinct blocks, not intertwined.
With clear logic, later modifications only require local changes; with chaotic structure, changing one part affects the whole, fearing the system will crash.
You think you saved time on structural design, but in reality, you are stealing your own future years of pain.
04
To put it bluntly: A PLC program without structure is not engineering; it can only be called “a running accident reserve.”
A bunch of beginners finish writing and just hand it over; the next person takes over and sees a program that is as tangled as noodles; modifying it is not an option, nor is leaving it as is, so in the end, they have to completely rewrite it—
Time, manpower, and risk are all costs.
You think you wrote a “multi-functional package”? Others see it as a “minefield.”
05
So, beginners, don’t rush to pursue “how many instructions you can write,” first learn “how to write the program clearly.”
If the logical structure is unclear, it does not indicate deep skills; it is digging a pit. Being able to organize control logic in a “modular, layered, and clearly commented” manner is what truly signifies entry into the field.
Don’t envy experienced engineers who can produce drawings in three days and go online in five; they have spent ten years mastering the concept of “structure,” while you are still stuck in the loop of “can it run.”
Ultimately, whether a PLC program is well-written or not, is not determined by how complex the functionality is, but by whether you can locate issues immediately when they arise,and behind this, it’s never about the quantity of instructions, but whether you have established a true logical system.