
5.FUNCTIONS TO SIMPLIFY PROGRAMMING PROGRAMMING B-63944EN-2/02
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5.1.11 Back Boring Cycle (G87)
This cycle performs accurate boring.
Format
G87 X_ Y_ Z_ R_ Q_ P_ F_ K_ ;
X_ Y_ : Hole position data
Z_ : The distance from point R to the bottom of the hole
R_ : The distance from the initial level to point R
Q_ : Shift amount at the bottom of a hole
P_ : Dwell time at the bottom of a hole
F_ : Cutting feed rate
K_ : Number of repeats (if required)
G87 (G98) G87 (G99)
Spindle CW
Initial
level
Point R
Point Z
q
P
OSS
OSS
Spindle CW
Not used
Explanation
After positioning along the X- and Y-axes, the spindle is stopped at
the fixed rotation position. The tool is moved in the direction
opposite to the tool nose, positioning (rapid traverse) is performed to
the bottom of the hole (point R).
The tool is then shifted in the direction of the tool nose and the spindle
is rotated clockwise. Boring is performed in the positive direction
along the Z-axis until point Z is reached.
At point Z, the spindle is stopped at the fixed rotation position again,
the tool is shifted in the direction opposite to the tool nose, then the
tool is returned to the initial level. The tool is then shifted in the
direction of the tool nose and the spindle is rotated clockwise to
proceed to the next block operation.
- Spindle rotation
Before specifying G87, use an auxiliary function (M code) to rotate
the spindle.
If drilling is continuously performed with a small value specified for
the distance between the hole position and point R level or between
the initial level and point R level, the normal spindle speed may not be
reached at the start of hole cutting operation. In this case, insert a
dwell before each drilling operation with G04 to delay the operation,
without specifying the number of repeats for K. For some machines,
the above note may not be considered. Refer to the manual provided
by the machine tool builder.
Shift amount q
Spindle orientation
Tool