Simultaneous vs. 3+2 Positional
Most parts quoted as "5-axis work" don't need simultaneous motion. Knowing the difference changes your cost.
When You Need Simultaneous
Sculpted surfaces with continuous curvature. Impeller blades, turbine airfoils, mold cavity surfaces, propeller blades — any surface where the tool must continuously change its orientation to maintain proper engagement. If the tool needs to tilt and swivel while cutting, it's simultaneous.
Ruled surfaces and blends. Surfaces that transition smoothly between different contours — the fillet between an airfoil and a hub, or the blend between intersecting freeform surfaces.
Undercuts requiring continuous tool axis control. Features where the tool must reach under an overhang by tilting progressively, not just indexing to a single angle.
When 3+2 Is Enough
Prismatic features on multiple faces. Holes, pockets, slots, flats, threaded features on different faces. This is the most common 5-axis application and it almost never needs simultaneous motion. Index, lock, machine. Repeat.
Compound-angle holes. Index the rotary axes to align the hole axis with the spindle, lock, drill. The rotary axes position, the spindle drills.
Chamfers and deburring at angles. Reaching edges not accessible from the top. Index to access angle, machine with a 3-axis move.
The Cost Difference
Simultaneous programming takes 2–5x longer than 3+2 for the same part complexity. Toolpath verification, gouge checking, and collision avoidance all require more attention when all five axes move at once. Machine time may also be longer because simultaneous toolpaths use lighter cuts to maintain accuracy.
If your part has only prismatic features on multiple faces, specifying "5-axis" without distinguishing between simultaneous and 3+2 may get you a quote that assumes simultaneous programming. Call out which features need simultaneous access and which are 3+2. Your quote will drop.
If you can describe the feature using flat geometry terms — holes, pockets, slots, flats — it's 3+2. If you need to describe it as a surface or contour, it might need simultaneous. And "might" is key — many contoured surfaces can be approximated with closely-spaced 3+2 passes, which is cheaper and often close enough.
Not sure which approach your part needs?
Send a drawing and we'll recommend the right strategy.