
B–62073E–1/042. INTERFACE BETWEEN CNC AND PMC–NA OR NB
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(e) Spindle speed override checking signals SPA0, SPB0, SPC0
[Classification]
Output signals
[Function] Notify the PMC of the result of multiplying the taught override for the spindle speed by the
override input by SPA, SPB, and SPC.
For example, during playback, if the taught override is 90% when the switch on the machine
operator’s panel selects 80%, that is, the override input by SPA, SPB, and SPC is 80%, 70%
override is notified by SPA0, SPB0, and SPC0 (80% x 90% = 72%, which is rounded off to
70%). When the result is 50% or less, the result is clamped and 50% is notified; when it is
120% or more, the result is clamped and 120% is notified.
The table below lists the correspondence between the signals and overrides.
Override(%)
50 60 70 80 90 100 110 120
SPA0 1 0 0 1 1 0 0 1
SPB0 1 1 1 1 0 0 0 0
SPC0 1 1 0 0 0 0 1 1
When the override playback function is used, the spindle override must be calculated in the
PMC not based on the switches on the machine operator’s panel but based on these signals.
In other words, the PMC reads the specified spindle speed with spindle speed signals RO0
to RO15, multiplies the speed by the spindle speed override input by SPA, SPB, and SPC,
and returns the result to the control unit using spindle motor voltage signals RI0 to RI12. The
control unit inputs voltage to the spindle amplifier based on RI0 to RI12 sent from the PMC.
Spindle
amplifier
D/A converter
Command voltage
calculation
Command spindle
speed
Override
Operation
panel
override SW.
SPA, SPB, SPC
SPA0, SPB0, SPC0
RO0 to RO15
RI0 to RI12
S Command
L1S command
Machine side
override
L1S command
register
Override value
calculation
NOTE 1 The method in which SPA0, SPB0, and SPC0 are not used in the PMC can be specified by a
parameter. In this case, the control unit multiplies the value specified in an S command by the
taught override for the spindle speed, and outputs the result with RO0 to RO15.
The PMC calculates the voltage by multiplying the spindle speed notified with RO0 to RO15
by the value specified by the override switches on the machine operator’s panel, that is, the
override notified to the control unit by SPA, SPB, and SPC.
NOTE 2 The ,L1S command register in the above figure stores the taught spindle speed override, which
is specified by a ,L1S command. This register is preset to 100% by resetting or program
number search.
0 : LOW
1 : HIGH