CNC Milling | G88 Cycle | Boring

In this article, we describe how to use G88 cycle for boring in CNC milling (CNC Machining Centre) machines with all details and examples.

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G88 Cycle Introduction

This cycle is used to bore a hole. After positioning along the X- and Y-axes, rapid traverse is performed to point R. Boring is performed from point R to point Z.
When boring is completed, a dwell is performed at the bottom of the hole, then the spindle is stopped and enters the hold state. At this time, you can switch to the manual mode and move the tool manually. Any manual operations are available; it is desirable to finally retract the tool from the hole for safety, though. At the restart of machining in the DNC operation or memory mode, the tool returns to the initial level or point R level according to G98 or G99 and the spindle rotates clockwise. Then, operation is restarted according to the programmed commands in the next block.

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“CNC Milling | G87 Cycle | Boring (Bottom)”

G88 Cycle Format

G88 X_ Y_ Z_ R_ P_ F_ K_ ;

Parameters

X_ : Hole position data
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 level
P_ : Dwell time at the bottom of a hole
F_ : Cutting feed rate
K_ : Number of repeats (if required)

G88 Cycle Examples

G88 CNC Program Example – 1

M3 S2000 ; Cause the spindle to start rotating.
G90 G99 G88 X300. Y-250. Z-150. R-100. P1000 F120. ; Position, drill hole 1, return to point R then stop at the bottom of the hole for 1 s.
Y-550. ; Position, drill hole 2, then return to point R.
Y-750. ; Position, drill hole 3, then return to point R.
X1000. ; Position, drill hole 4, then return to point R.
Y-550. ; Position, drill hole 5, then return to point R.
G98 Y-750. ; Position, drill hole 6, then return to the initial level.
G80 G28 G91 X0 Y0 Z0 ; Return to the reference position
M5 ; Cause the spindle to stop rotating.


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