In the world of modern CNC manufacturing, precision and efficiency are everything. As industries continue to push for tighter tolerances, reduced cycle times, and more complex geometries, machining strategies must evolve accordingly. One such strategy that bridges the gap between traditional 3-axis machining and full 5-axis machining is known as 3+2 machining. It offers a practical and powerful solution for many machining operations without the complexity and cost of continuous 5-axis motion.

Defining 3+2 Machining

3+2 machining, also referred to as 5-axis positional machining, is a method where a 3-axis milling machine uses two additional rotational axes to position the cutting tool or the part before the toolpath is executed. Unlike simultaneous 5-axis machining—where all five axes move at once—3+2 machining locks the two rotary axes in a fixed position during cutting, allowing the three linear axes (X, Y, and Z) to machine the part. This technique provides access to difficult-to-reach surfaces and complex geometries that would otherwise require multiple setups or custom fixtures. It’s especially beneficial in parts with angled features, compound holes, and undercuts.

Why Use 3+2 Instead of Full 5-Axis?

While simultaneous 5-axis machining offers unparalleled flexibility, it also comes with higher costs, more complex programming, and greater demands on machine accuracy. 3+2 machining delivers many of the same advantages—like better tool access and reduced setups—without the overhead of true 5-axis motion. It simplifies the CAM programming process and can often be done on machines that support 5-axis positioning but not full 5-axis interpolation. For many shops, this makes 3+2 an ideal balance between capability and cost-effectiveness.

How 3+2 Machining Works

The process begins by rotating the workpiece or the tool head to a specific angular orientation using the machine’s rotary axes. Once positioned, these axes are locked in place. Then, the machine executes a standard 3-axis toolpath in the rotated coordinate system. This allows the cutting tool to approach the workpiece from optimal angles, improving tool reach and surface finish. CAM software plays a critical role in 3+2 machining. The programmer defines the required orientations and toolpaths within the software, which then outputs G-code that instructs the machine to move into position and perform the machining sequence.

Key Benefits of 3+2 Machining

• Reduced Setups: Fewer part repositions mean less opportunity for error and higher accuracy
• Improved Tool Access: Access to complex features from better angles with shorter tools
• Better Surface Finish: More rigid setups lead to cleaner surface finishes
• Shorter Cycle Times: Efficient toolpaths and fewer tool changes
• Increased Tool Life: Reduced deflection helps extend tool longevity

These benefits make 3+2 machining a strong choice for complex parts that do not require continuous 5-axis movement.

Applications in Manufacturing

3+2 machining is widely used across industries where complex geometries are common. In aerospace manufacturing, it’s used to create turbine components, engine housings, and brackets with compound angles. In medical device machining, it allows for the precise creation of implants and surgical tools that require multiple angled surfaces. In mold and die work, 3+2 enables access to sidewalls and undercuts without custom setups. Even shops producing lower-complexity parts can benefit by using 3+2 to optimize tool approach angles, reduce chatter, and increase tool life.

Requirements for 3+2 Machining

To perform 3+2 machining, you need:

• A CNC machine with at least two additional rotary axes (trunnion table or swivel head)
• CAM software that supports 3+2 programming (e.g., Fusion 360, Mastercam, Siemens NX)
• Accurate fixturing and workholding for angled orientations

These elements work together to ensure that parts remain stable and precision is maintained throughout the machining process.

Conclusion

3+2 machining offers a smart, efficient way to achieve complex geometry without the challenges of full 5-axis programming and operation. By combining strategic positioning with traditional 3-axis motion, shops can increase part quality, reduce lead times, and make better use of their existing equipment. Whether you're machining aerospace parts or improving surface finish on production components, understanding and implementing 3+2 machining can elevate your capabilities without overcomplicating your process.