3+2 machining

3+2 machining (also called positional 5-axis) tilts the workpiece to a fixed angular position using two additional rotary axes, then cuts with ordinary 3-axis linear motion while the part stays still at that angle. It differs from simultaneous 5-axis, where all five axes move together during the cut itself.

What 3+2 can and can't do compared with simultaneous 5-axis

3+2 machining reaches many of the same faces as full simultaneous 5-axis, often with simpler, more robust programming, but it can't produce the smoothly blended, continuously tilted surfaces that true simultaneous motion allows.

Where 3+2 machining applies

Implied by features on multiple angled faces that could be reached with a small number of fixed reorientations, without requiring a continuously changing tool angle during the cut.

Common mistakes

Assuming 3+2 and simultaneous 5-axis are interchangeable; a continuously blended, complex surface (common in impellers or turbine blades) generally requires true simultaneous motion, not a series of fixed positions.

Is 3+2 machining the same as 5-axis machining?

It runs on a 5-axis machine, but only two axes are used for positioning between cuts; simultaneous 5-axis moves all five axes together during the cut.

Why use 3+2 instead of full simultaneous 5-axis?

It's often simpler and more robust to program, and sufficient for parts where faces just need reaching at fixed angles rather than continuously blended surfaces.

Can 3+2 reach an undercut?

Often yes, since the part can be tilted to expose a feature a fixed 3-axis setup couldn't reach, unlike true 3-axis machining.