5-axis CNC machining: how it works, costs and design rules

The cutter or the table also tilts and rotates, so the tool can reach five sides of the part and work at angles in one clamping. Used for complex housings, impellers, medical parts and anything with angled features.

Typical tolerance

±0.05 mm general, ±0.01 mm on selected features

Quantities

1 to a few hundred

Lead time

5–20 working days

Materials

All machinable metals and plastics

How it works

Two rotary axes are added to the three linear axes. In 3+2 machining the part is tilted to a fixed angle and then cut like a 3-axis part; in simultaneous 5-axis all axes move together, which allows smooth freeform surfaces.

Benefits

• Many faces machined in one setup, so features line up accurately.
• Angled holes and faces without special fixtures.
• Shorter tools can be used, which improves finish and accuracy.
• Freeform surfaces that 3-axis machines cannot reach.

Limitations

• Machine hour rates are typically 30–80% higher than 3-axis.
• Programming takes longer, which hurts one-off parts.
• Fewer shops offer it, so lead times can be longer.

What drives the cost

• Machine rate and programming time.
• Simultaneous 5-axis surfaces versus simpler 3+2 positioning.
• Fixturing that leaves the five faces accessible.

Design rules

• Ask whether the part could be 3-axis with one extra setup; it is often cheaper.
• Leave room for clamping on one face (or plan a sacrificial stock tab).
• Keep angled features at angles that are easy to set, such as 15°, 30° and 45°.

Preparing your STEP file

• Export as AP242 if you have PMI, so the shop sees your tolerances in CAM.
• Keep freeform surfaces as true B-spline surfaces; never export from a mesh.
• Define the part coordinate system on a sensible datum, such as a machined face and two edges.

See also the full STEP export checklist and the comparison of all processes.