Post Processor Engineering

3+2 Axis vs Simultaneous 5-Axis Post Processing

Both run on the same machine, but the post processor treats them very differently. Understanding the difference helps you choose the right strategy and the right post features.

May 5, 20267 min readENGIMANDI CNC Team

Side-by-side comparison

Aspect	3+2 (positional)	Simultaneous 5-axis
Rotary motion	Only between operations	Continuous during cutting
Controller function	Tilted plane (`G68.2`, `CYCLE800`, `PLANE`)	TCP (`G43.4`, `TRAORI`, `M128`)
Code inside operation	Ordinary 3-axis XYZ	XYZ + two rotaries every block
Canned cycles	Yes, along tilted axis	Generally not
Feed mode	Normal feed per minute	Inverse time or TCP feed
Rotary clamping	Clamped	Unclamped
Limit / singularity handling	Simple: check once	Complex: check every point
Program size	Small	Often large
Verification effort	Moderate	High

Typical 3+2 output

G68.2 X0 Y0 Z0 I0 J30. K0
G53.1
G43 H3 Z50.
G81 X10. Y10. Z-15. R2. F150.
X30.
G80
G69

Typical simultaneous output

G43.4 H6
G93
G01 X12.40 Y-3.10 Z8.22 A-22.4 C41.9 F240.
X12.71 Y-2.95 Z8.10 A-22.9 C42.6 F236.
...
G94
G49

When to use each

3+2: prismatic parts with angled faces and holes, deep pockets reachable with short tools, maximum rigidity.
Simultaneous: freeform surfaces, impellers, blades, swarf walls, undercuts and smooth blending.

Many parts use both: 3+2 for roughing and features, simultaneous for finishing surfaces.

Use 3+2 wherever you can, simultaneous wherever you must.

5-axis post development

See our CNC post processor development service, 3+2 posts and simultaneous posts.

EM

ENGIMANDI CNC Team

We develop, customise and commission CNC post processors for Fusion, NX CAM, Mastercam, SolidCAM and other CAM systems.