
B–62073E–1/042. INTERFACE BETWEEN CNC AND PMC–NA OR NB
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Procedure for rigid tapping
1 The operation when G84.2 is specified is described below. The spindle speed must be specified by the
S command in the block G84.2 or a previous block.
2 The control unit moves the X– and Y–axes to the hole to be tapped. While it is moving the X– and Y–axes
it sets the rigid tapping signal, RTAP, high.
3 When G84.2 is specified, the spindle may be stopped by the M05 command specified before G84.2 or ro-
tated by the M03 or M04 command at a speed specified by the S command. Irrespective of the spindle
state, the following must be executed in the machine (PMC) when the RTAP signal goes high.
(i) The PMC must set all signals specifying the voltage of the spindle motor, RI0 to RI12, low so the control
unit specifies 0 V as the voltage corresponding to the spindle speed for the spindle amplifier. It is rec-
ommended that the following output signals to the spindle amplifier be set low at the same time: clock-
wise spindle rotation signal, SFR, and reverse spindle rotation signal, SRV. When RI0 to RI12 are set
low, the control unit specifies 0 V as the voltage corresponding to the spindle speed for the spindle
amplifier. The voltage of the spindle motor becomes 0 V, and the spindle motor stops. If SFR and SRV
are also set low, the spindle motor normally stops sooner.
(ii) The PMC must check that the spindle stops when the zero speed signal, SST, of the spindle amplifier
goes high, and set the torque limit signal, TLML, high. (TLML is an output signal to the spindle amplifi-
er.) The PMC must also set SFR, high, and SRV, low. This causes the spindle to rotate forward when
the voltage corresponding to the spindle speed is positive and reverse direction when the voltage is
negative. After 400 milliseconds or more have passed, the PMC must set the spindle stop check sig-
nal, SPSTP, high.
4 After the RTAP signal is set high, the control unit moves the X– and Y–axes to the hole to be tapped, then
moves the Z–axis to point R, irrespective of the actions of the PMC described in 3 above.
5 After moving along the Z–axis to point R, the control unit checks whether the SPSTP signal is high. If it
is low, the control unit waits for the signal to go high. When the signal goes high, the control system of the
spindle is switched from spindle control to positioning control.
In positioning control, the distance the tag was moved is entered into the error counter and converted to
the voltage specifying the speed of the motor as shown below. The conversion coefficient (servo loop gain
multiplier) depends on the gear ratio of the spindle motor to the spindle. According to the spindle gear
selection signal, GS1, GS2 or GS4, which is input from the PMC when the spindle control is switched to
positioning control, the servo loop gain multiplier of the current gear is specified in the positioning control
circuit of the spindle. The servo loop gain multiplier of each gear must be specified as a parameter before-
hand.
x4
x1
CMR
DMR 1024pulse/rev
Spindle control
(calculation of speed
voltage of spindle
speed rpm)
Error counter
Spindle
amplifier
Spindle
motor
Spindle
Position coder
Gear ratio
n:m
l:p
Gear ratio
D/A converter
+
-
Gear ratio of spindle
to position coder (l : p)
Minimum movement unit
(detection unit) deg
1 : 1
1 : 2
1 : 4
1 : 8
0.088 (1×360 / 4096)
0.176 (2×360 / 4096)
0.352 (4×360 / 4096)
0.703 (8×360 / 4096)