How to choose between Siemens PLC and Rockwell PLC? What's the difference between them?

Each type of PLC on the market today has its own functional advantages. PLCs from Rockwell (Allen Bradley) and Siemens (Siemen) are two of the most widely used in the world, but there are many key differences between them. Let us take a look below:

Performance and availability

Making a decision between the two based solely on performance isn't easy. In terms of speed, reliability and output, they are equally matched. However, factors such as ease of operation and integration are often differentiating points to consider.

There's a lot to be said for ease of use and user-friendly interface. Allen-Bradley PLCs are known for possessing both of these qualities, making this programmable logic controller an attractive investment for any manufacturer. Ease of use means that even relatively untried PLC technicians without extensive programming experience can still use Allen-Bradley PLCs—but the ease of use doesn't stop there. Debugging an Allen-Bradley PLC arguably takes less time and effort than using a Siemens PLC.

In addition, Allen-Bradley PLCs can communicate efficiently with third-party devices and can import and export tags from Excel to a Human Machine Interface (HMI) or SCADA database.

Still, depending on the technician's experience level and the intended application, ease of use is not always the most important criterion. Siemens allows extensive programming and customization of their PLCs to meet specific business needs. Naturally, this means technicians will need a stronger computer programming background to effectively use and maintain Siemens PLCs, but the opportunities this customization presents cannot be underestimated.

Hardware

While the general consensus is that the Allen-Bradley PLC is the more user-friendly solution of the two, they may fall slightly short in terms of ease of installation compared to the Siemens.

When installing an Allen-Bradley PLC, you will also need to connect the Allen-Bradley power supply, rack, and add-in card for the secure communication port. Siemens PLCs, on the other hand, plug into most standard 24V DC power supplies and have built-in secure communication ports. Finally, Siemens PLCs come with built-in protocols according to European standards (ASI, Profinet, Profibus), while Allen-Bradley PLCs come with American protocols (EthernetIP, ControlNet, DeviceNet, etc.).

Support

Support availability is an important feature to consider when purchasing a PLC. Siemens offers 24/7 after-sales technical support, field services and spare parts for its products every day of the year, including any products falling under its process and factory automation categories. Rockwell also offers year-round 24/7 technical support for its products, but it's not as comprehensive as what Siemens offers, and the level of free support depends on the amount of hardware installed. In either case, the level of support you feel comfortable with may be an important factor in your purchasing decision.

Which one is the winner?

Sure, it's easy to choose a PLC based on one or more features, but when making a purchasing decision, it's more important to look at the entire package - ease of use and integration, after-sales support, and more. Ultimately, the right PLC is the one that checks the most boxes for a given application.

Determining a "winner" based on popularity alone really depends on where you work. Siemens PLC is undoubtedly the most popular in Europe, which makes sense since Siemens AG happens to be the continent's largest industrial manufacturing company. In North America, Rockwell Automation's Allen-Bradley is by far the most popular PLC supplier.