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DRILLING CYCLE (G81)

The G81 cycle is intended for drilling.

Program: G81 X~ Y~ Z~ A~ R~ L~

The G81 Cycle is as follows:

  • Step 1: Preliminary canned cycle motion.
  • Step 2: Move the Z-axis only at the current feed rate to the Z position.
  • Step 3: Retract the Z-axis at traverse rate to clear Z.

EXAMPLES

These examples demonstrate how the G81 canned cycle works in detail. Other canned cycles work in a similar manner.

EXAMPLE:

The current position is (1, 2, 3), the XY-plane has been selected, and the following line of code is interpreted: G90 G81 G98 X4 Y5 Z1.5 R2.8

This means that it’s in absolute distance mode (G90), old Z retract mode (G98) and the G81 drilling cycle is performed once. The X number and X position are 4. The Y number and Y position are 5. The Z number and Z position are 1.5. The R number and clear Z are 2.8. The following moves take place:

  1. G00 motion parallel to the XY-plane to (4,5,3)
  2. G00 motion parallel to the Z-axis to (4,5,2.8)
  3. G01 motion parallel to the Z-axis to (4,5,1.5)
  4. G00 motion parallel to the Z-axis to (4,5,3)
EXAMPLE:

The current position is (1, 2, 3), the XY-plane has been selected, the following line of code is interpreted: G91 G81 G98 X4 Y5 Z-0.6 R1.8 L3

This means that it’s in incremental distance mode (G91), old Z retract mode, and the G81 drilling cycle is repeated three times. The X number is 4, the Y number is 5, the Z number is -0.6 and the R number is 1.8. The initial X position is 5 (=1+4), the initial Y position is 7 (=2+5), the clear Z position is 4.8 (=1.8+3) and the Z position is 4.2 (=4.8-0.6). Old Z is 3.0.

The first move is a traverse along the Z-axis to (1,2,4.8), since old Z < clear Z. The first repeat consists of three moves:

  1. G00 motion parallel to the XY-plane to (5,7,4.8)
  2. G01 motion parallel to the Z-axis to (5,7, 4.2)
  3. G00 motion parallel to the Z-axis to (5,7,4.8)

The second repeat consists of three moves. The X position is reset to 9 (=5+4) and the Y position to 12 (=7+5):

  1. G00 motion parallel to the XY-plane to (9,12,4.8)
  2. G01 motion parallel to the Z-axis to (9,12, 4.2)
  3. G00 motion parallel to the Z-axis to (9,12,4.8)

The third repeat consists of three moves. The X position is reset to 13 (=9+4) and the Y position to 17 (=12+5):

  1. G00 motion parallel to the XY-plane to (13,17,4.8)
  2. G01 motion parallel to the Z-axis to (13,17, 4.2)
  3. G00 motion parallel to the Z-axis to (13,17,4.8)

Example code using G81cycle:

(Sample Program G81EX18:)

(Workpiece Size: X4, Y3, Z1)

(Tool: Tool #6, 3/4” HSS DRILL)

(Tool Start Position: X0, Y0, Z1)

N2 G90 G80 G40 G54 G20 G17 G94 G64 (Safety Block)

N5 G90 G80 G20

N10 M06 T6 G43 H6

N15 M03 S1300

N20 G00 X1 Y1

N25 Z0.5

N30 G81 Z-0.25 R0.125 F5 (Drill Cycle Invoked)

N35 X2

N40 X3

N45 Y2

N50 X2

N55 X1

N60 G80 G00 Z1 (Cancel Canned Cycles)

N65 X0 Y0

N70 M05

N75 M30