3D surface machining basics in CNC Programming

Introduction

3D surface machining lets machines cut curved and complex shapes. It helps make smooth, detailed parts that flat cutting can't do.

Making car body parts with smooth curves.

Creating molds for plastic or metal casting.

Shaping airplane wings or turbine blades.

Crafting artistic sculptures or jewelry with curves.

Syntax

CNC Programming

G1 Xx Yy Zz Ff
G2/G3 Xx Yy Zz Ii Jj Kk Ff

G1 moves the tool in a straight line to the point (X, Y, Z) at feed rate F.

G2 and G3 move the tool in arcs or curves using center points (I, J, K).

Examples

Move straight to position X=10, Y=20, Z=5 at speed 100.

CNC Programming

G1 X10 Y20 Z5 F100

Cut a clockwise arc to X=15, Y=25, Z=5 with center offset I=5.

CNC Programming

G2 X15 Y25 Z5 I5 J0 K0 F80

Sample Program

This program cuts a racetrack-shaped path (two straight lines connected by semicircular arcs) on a flat surface using straight and arc moves.

CNC Programming

G21 ; Set units to millimeters
G90 ; Use absolute positioning
G1 X0 Y0 Z5 F200 ; Move above start point
G1 Z0 F100 ; Lower to surface
G1 X10 Y0 Z0 F150 ; Cut straight line
G3 X10 Y10 Z0 I0 J5 K0 F150 ; Cut a counterclockwise arc
G1 X0 Y10 Z0 F150 ; Cut straight line
G3 X0 Y0 Z0 I0 J-5 K0 F150 ; Cut a counterclockwise arc back to start
G1 Z5 F100 ; Lift tool
M30 ; End program

Important Notes

Always check tool paths in simulation before running on the machine to avoid crashes.

Feed rates (F) control how fast the tool moves; slower for curves to keep smooth cuts.

Use absolute positioning (G90) to make programming easier to understand.

Summary

3D surface machining uses straight and curved moves to cut complex shapes.

G1 moves in straight lines; G2 and G3 create arcs for smooth curves.

Programs combine these moves to shape parts with smooth surfaces.