Thursday, August 2, 2018

CNC Programming Examples - Taper Threading

  Thanh A Tran       Thursday, August 2, 2018

Fanuc G84 Tapping Cycle

G84 tapping cycle performs tapping operation, tapping is performed by rotating the spindle clockwise, when bottom of the hole has been reached, the spindle is rotated in the reverse direction for retraction. This whole operation creates threads.

Syntax

G84 X... Y... Z... R... P... F... K...
Parameter Description
X Hole position in x-axis.
Y Hole position in y-axis.
Z Depth, tapping from R-plane to Z-depth.
R Position of the R plane.
P Dwell time.
K Number of cycle repetitions (if required) .
F Feedrate.
Once given in program G84 tapping cycle is repeated at every axis movement until G80 is given in program to end tapping cycle.

Notes

Feedrate override is ignored during tapping.
Feed-hold does not stop the machine until the return operation is completed.

Usage

N150 M6 T2
        N160 G90 G00 X60 Y28 Z12 S100 M03
        N170 G99 G84 X60 Y28 Z-17 P300 R2 F120
        N180 G98 Y12
        N190 G91 G80 G28 X0 Y0 Z0 M05
        N200 M30

Working

Brief description of how G84 tapping cycle works,

G84 tapping cycle working
0- CW Spindle rotation command (M03) must be given in part-program.
1- Rapid traverse to X, Y position (pre-drill hole position).
2- Rapid traverse to R-plane.
3- Tapping operation is done till Z-depth (with tapping feed given with G84).
4-1- Dwell for time specified with P
4-2- Spindle is rotated CCW
5- Tap is Retracted with the specified feed.
At R-plane spindle is rotated CW.
If G99 is specified then tapping for this hole ends here,
6- if G98 is given in program then tap is moved to Initial-level.

G98 G99 Modes

After completing tapping the return height can be controlled by using G98 or G99.
G98 Tap will return to the Initial level
G99 Tap will return to R-plane.
G98, G99 can be used multiple times during G84 tapping cycle.

Repeat Drilling

G84 tapping cycle can be repeated multiple times if K value is given.
For working example see G81 drilling cycle.

Working Example


G84 tapping cycle example
N10 T1 M06
        N20 G90 G54 G00 X30 Y25
        N30 S100 M03
        N40 G43 H01 Z5 M08
        N50 G84 Z-20 R2 F1.25
        N60 X80 Y50
        N70 G80 G00 Z100 M09
        N80 M30

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