Two of the most commonly used cycles in CNC programming are the G81 Drilling Cycle and the G84 Tapping Cycle. These cycles automate repetitive tasks, saving time and reducing the potential for errors.
Usage Format
G81 Drilling Cycle:
G81 R... Z... F...
- R: Position of the retract plane
- Z: Position of the bottom of the hole
- F: Feed rate
G84 Tapping Cycle:
G84 R... Z... F...
- R: Position of the retract plane
- Z: Depth of the tapped hole
- F: Feed rate (pitch of the thread)
Explanation
G81 Drilling Cycle is a simple cycle used for drilling where the tool plunges into the material at a specified feed rate, drills to the desired depth, and then retracts.
G84 Tapping Cycle is used for tapping threaded holes. It requires the spindle to rotate in sync with the feed rate to match the thread pitch.
Example
Here’s a text diagram and example of how these cycles might be programmed:
G81 Example:
%
O1001 (Drilling Operation)
T01 M06 (Tool Change to Drill)
G90 G17 G40 G21 (Absolute positioning, XY plane, Cancel cutter radius compensation, Metric units)
M03 S1200 (Spindle on clockwise, Speed 1200 RPM)
G00 X50 Y25 (Rapid move to hole location)
G43 Z15 H01 M08 (Tool length compensation, Coolant on)
G81 R2.0 Z-12.5 F75 (Drilling cycle)
X50 Y50 (Second hole location)
G80 (Cancel cycle)
M30 (End of program)
%
G84 Example:
%
O1002 (Tapping Operation)
T02 M06 (Tool Change to Tap)
G90 G17 G40 G21 (Absolute positioning, XY plane, Cancel cutter radius compensation, Metric units)
M03 S600 (Spindle on clockwise, Speed 600 RPM)
G00 X50 Y25 (Rapid move to hole location)
G43 Z15 H02 M08 (Tool length compensation, Coolant on)
G84 R2.0 Z-20.0 F.75 (Tapping cycle)
X50 Y50 (Second hole location)
G80 (Cancel cycle)
M30 (End of program)
%
In the examples above, the G81 and G84 cycles are used to drill and tap two holes at coordinates X50 Y25 and X50 Y50. The retract plane is set at Z15, and the drilling depth for G81 is Z-12.5 with a feed rate of F75. For the G84 tapping cycle, the depth is Z-20.0 with a feed rate corresponding to the thread pitch, which is F.75 in this case.