What Is the Difference Between FANUC 30i and 31i?

If you're researching FANUC CNC controllers, you've likely come across the FANUC Series 30i and Series 31i—two of the brand’s most powerful and popular high-end controller families. While they appear similar at first glance, they are designed for different levels of machine complexity, axis control, and functionality.

Let’s break down the key differences between FANUC 30i and 31i, so you can make an informed decision for your CNC or automation setup.

Overview of the FANUC 30i and 31i Series

1. Machine Complexity and Number of Axes

• FANUC 30i is engineered for ultra-complex, large-scale machines with up to 96 total axes and 10 independent CNC paths. This makes it perfect for high-speed gantry machines, multitasking centers, and production lines with synchronized robotics.

• FANUC 31i, while powerful, supports fewer axes—typically 24 axes and up to 4–5 paths, depending on the specific model. It’s ideal for machines that need simultaneous 5-axis control but not full multitasking or massive-scale processing.

2. 5-Axis and Multitasking Capabilities

Both FANUC CNC controllers support 5-axis machining, but:

• 31i-B5 is specifically optimized for 5-axis simultaneous control, making it ideal for industries like mold making, aerospace, and medical machining.

• 30i-B goes beyond 5-axis and supports multiple 5-axis operations across different paths, useful for multitasking machines like turn-mill centers.

3. Processing Power and Speed

• 30i Series offers higher CPU speed, larger program memory, and enhanced nano interpolation, making it better suited for complex tool paths, high-speed cutting, and simultaneous control of multiple operations.

• 31i Series has slightly lower processing capacity, but is more than capable for single-part operations, contouring, and precision finishing.

4. AI and Intelligent Functions

• FANUC 30i-B Plus models now feature AI Thermal Displacement Compensation, AI Servo Tuning, and IoT connectivity for predictive maintenance and smart analytics.

• FANUC 31i-B5 includes some AI features but not to the same extent as the 30i series. It still supports servo learning control and advanced error detection.

5. Software Options and Integration

Both series support:

• Manual Guide i (conversational programming)

• Ethernet/IP, PROFINET, and FOCAS protocols

• Robot interface

• Safety functions (Dual Check Safety)

However, 30i offers more expandable options for complex automation tasks and factory-wide networking.

6. Price and Cost Consideration

If you're balancing cost vs. capability, 31i offers an excellent middle ground for many shops and OEMs.

Which Should You Choose?

Summary: Key Differences at a Glance

FAQs

Q1: Is FANUC 31i good for 5-axis machining?
Yes. The FANUC 31i-B5 is designed specifically for simultaneous 5-axis control with excellent motion accuracy.

Q2: Can FANUC 30i control multiple machines or robots?
Yes. With up to 10 CNC paths, the 30i can manage multiple tool heads, spindles, or even robot integration simultaneously.

Q3: What industries use FANUC 30i and 31i?

• 30i: Aerospace, automotive, large industrial CNCs

• 31i: Medical, mold and die, high-precision parts

Q4: Are 30i and 31i backward compatible with older FANUC systems?
Yes, both support backward compatibility with legacy programs and M-codes through FANUC’s data transfer and memory tools.

Conclusion

The FANUC 30i and 31i are both elite CNC controllers—but serve slightly different niches:

• Choose 30i for complex, multi-path, multi-axis environments.

• Choose 31i for precision machining and 5-axis control in a more compact or cost-sensitive setup.

Still not sure which controller fits your CNC machine or factory line? Reach out to a certified FANUC distributor—we’ll help you select the right control system tailored to your production goals.