How to CNC Machine Wood: Step-by-Step Guide

To CNC machine wood, you write a G-code program that controls the cutting tool's path and speed on the wood piece. Use commands like G0 for rapid moves and G1 for cutting moves, setting spindle speed and feed rate to suit the wood type.

Syntax

G-code is the language used to control CNC machines. Key commands include:

• G0 X Y Z: Move the tool quickly to position (X, Y, Z) without cutting.
• G1 X Y Z F: Move the tool to position (X, Y, Z) while cutting at feed rate F.
• M3 S: Turn the spindle on at speed S (RPM).
• M5: Stop the spindle.
• G90: Use absolute positioning.
• G21: Set units to millimeters.

These commands tell the CNC machine how to move and cut the wood.

gcode

G21 ; Set units to millimeters
G90 ; Use absolute positioning
M3 S12000 ; Start spindle at 12000 RPM
G0 X0 Y0 Z5 ; Move above start point
G1 Z-3 F300 ; Lower tool into wood at 300 mm/min
G1 X50 Y0 F500 ; Cut in X direction
G1 X50 Y50 ; Cut in Y direction
G1 X0 Y50 ; Cut back in X
G1 X0 Y0 ; Complete square
G0 Z5 ; Raise tool
M5 ; Stop spindle

Example

This example cuts a simple 50x50 mm square pocket 3 mm deep in wood using G-code commands. It starts the spindle, moves the tool safely, cuts the shape, then stops the spindle.

gcode

G21 ; Set units to millimeters
G90 ; Absolute positioning
M3 S12000 ; Spindle on at 12000 RPM
G0 X0 Y0 Z5 ; Move above start
G1 Z-3 F300 ; Cut down 3 mm
G1 X50 Y0 F500 ; Cut right
G1 X50 Y50 ; Cut up
G1 X0 Y50 ; Cut left
G1 X0 Y0 ; Cut down
G0 Z5 ; Raise tool
M5 ; Spindle off

Output

The CNC machine cuts a 50x50 mm square pocket 3 mm deep in the wood.

Common Pitfalls

Common mistakes when CNC machining wood include:

• Setting spindle speed too high or too low, causing burning or poor cuts.
• Using incorrect feed rates, which can break tools or leave rough surfaces.
• Not setting the correct tool depth, leading to incomplete cuts or damage.
• Forgetting to use absolute positioning (G90) causing unexpected tool paths.
• Not raising the tool safely before rapid moves (G0 Z5) risking collisions.

Always simulate your G-code in software before running on the machine.

gcode

Wrong:
G1 X50 Y0 F500 ; Cutting without spindle on

Right:
M3 S12000 ; Spindle on
G1 X50 Y0 F500 ; Cutting move

Quick Reference

Command	Description
G21	Set units to millimeters
G90	Use absolute positioning
M3 S[Speed]	Start spindle at specified RPM
M5	Stop spindle
G0 X Y Z	Rapid move to position without cutting
G1 X Y Z F	Cutting move to position at feed rate F

Key Takeaways

Write clear G-code commands to control tool movement and spindle speed for wood cutting.

Use appropriate spindle speed and feed rate to avoid burning or tool damage.

Always start with safe tool positioning and end by stopping the spindle.

Simulate your G-code before running to prevent mistakes and collisions.

Use absolute positioning (G90) and units in millimeters (G21) for consistent results.