Do you remember the awkwardness I felt when I first took charge of an automation project? With a limited budget and unclear customer requirements, the marketing hype from various PLC brands left me bewildered. It felt like stepping into an electronics market to buy a phone, only to be overwhelmed by a myriad of specifications and features. After 15 years of experience in the industrial automation field, today I will share the “unwritten rules” and practical experiences of PLC selection.
First, Clarify What Your “Recipe” Needs in Terms of “Kitchen Tools”
When selecting a PLC, it is essential to clarify the application scenario and control requirements. This is akin to determining a recipe before cooking.
I remember once visiting a small to medium-sized factory where the owner spent a fortune on a high-end Japanese PLC, only to find that less than 10% of its functions were utilized, and the overly complex program made maintenance difficult. It was like using a butcher’s knife to cut tofu—wasting money and adding unnecessary complexity.
When assessing needs, consider:
- • I/O Points: The number of inputs and outputs, reserving 30% redundancy
- • Communication Requirements: Types of devices and host computers to be connected
- • Control Precision and Speed: Minimum time requirements for periodic tasks
- • Special Functions: Such as high-speed counting, PID control, motion control, etc.
- • Program Complexity: Simple sequential control or complex algorithms
Brand Selection: It’s Not Just About Buying a PLC, But Also About the Ecosystem and Service
I often tell my apprentices:Choosing a PLC brand is like entering a “technical marriage”; once chosen, it is usually a long-term commitment.
Mainstream brands each have their characteristics:
- • Siemens: High reliability, comprehensive documentation, but relatively expensive
- • Mitsubishi: Rich instruction set, compact size, suitable for space-constrained environments
- • Omron: User-friendly human-machine interface, convenient for small applications
- • Domestic Brands: High cost-performance ratio, quick service response, but incomplete ecosystem
Once, late at night, a food factory’s production line suddenly stopped. The issue was not with the PLC itself, but rather the inability to find someone who could program it! That niche brand was cheap, but there was no technical support available locally.Choosing a brand with a high market share means you can more easily find talent for programming and maintenance.
Price Traps: Don’t Just Focus on the PLC’s Base Price
Many beginners easily fall into the trap of “only looking at the PLC host price.” One of my clients did just that and chose a cheap brand, only to discover:
- • Expansion modules are exorbitantly priced
- • Programming software requires additional payment
- • Every firmware upgrade incurs a cost
The correct way to compare prices is: the total cost of the host + required modules + software + training + spare parts. Some brands have cheap hosts but expensive “consumables,” which can be more costly in the long run.
Start Learning with Small Projects, Progress Gradually
If you are a beginner, my advice is:Start with an entry-level PLC platform that has room for growth. For example, Siemens’ S7-1200 or Mitsubishi’s FX series, these products:
- • Are relatively affordable
- • Have abundant learning resources
- • Share basic principles with high-end products
- • Have strong community support
My first project involved using the FX2N to control a simple packaging line, which laid a solid foundation for me. Even now, as I primarily work on large systems, that foundational knowledge remains applicable.
Three Steps for Decision Making
To summarize, the decision-making process can be simplified into three steps:
- 1. Needs Analysis: Number of control points, response time, communication requirements
- 2. Brand Selection: Consider ecosystem, local support, spare parts supply chain
- 3. Cost-Effectiveness Assessment: Total cost of ownership rather than just the price of a single device
Remember,there is no perfect PLC, only the PLC that best fits your application scenario. Just as there are no best tools, only the tools that are most suitable for the job.
Choosing the right PLC not only ensures the smooth progress of the project but also saves a lot of trouble for future expansions and maintenance. After all, in a factory environment, the most expensive thing is not the equipment itself, but every minute of downtime!