Drilling operation (G81 canned cycle) in CNC Programming

Introduction

The G81 canned cycle helps you drill holes quickly and easily by automating the drilling steps in CNC machines.

When you need to drill multiple holes of the same depth on a workpiece.

When you want to save time by automating repetitive drilling tasks.

When you want consistent hole depth and position without manual control.

When programming CNC machines for simple drilling operations.

When you want to reduce programming errors by using a standard cycle.

Syntax

CNC Programming

G81 X__ Y__ Z__ R__ F__ ;

X and Y specify the hole position coordinates.

Z is the depth to drill (negative value means down).

R is the retract plane height (safe height above the workpiece).

F is the feed rate (speed of drilling).

Examples

Drill a hole at X=10, Y=20 down to 5 units deep, retract to 2 units above the surface, at feed rate 100.

CNC Programming

G81 X10 Y20 Z-5 R2 F100 ;

Drill at origin (0,0) down 10 units, retract to 1 unit above, feed rate 80.

CNC Programming

G81 X0 Y0 Z-10 R1 F80 ;

Sample Program

This program drills three holes using G81. It moves to each hole position and drills down 5 units, retracting to 2 units above the surface each time.

CNC Programming

N10 G90 G21 ; Set absolute positioning and metric units
N20 G00 X0 Y0 ; Move to start position
N30 G81 X10 Y10 Z-5 R2 F100 ; Drill hole at (10,10)
N40 X20 Y10 ; Drill hole at (20,10)
N50 X20 Y20 ; Drill hole at (20,20)
N60 G80 ; Cancel canned cycle
N70 G00 Z50 ; Retract to safe height
N80 M30 ; End program

Important Notes

Always use G80 to cancel the canned cycle after drilling to avoid unexpected drilling.

Make sure the retract plane (R) is above the workpiece to prevent collisions.

Feed rate (F) controls how fast the drill moves down; too fast can break the tool.

Summary

G81 automates drilling holes by moving down, drilling, and retracting.

Use X, Y for hole positions, Z for depth, R for retract height, and F for feed rate.

Cancel G81 with G80 after finishing drilling.