
B–62073E–1/042. INTERFACE BETWEEN CNC AND PMC–NA OR NB
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The PMC notifies the control unit of the currently selected gear with spindle gear selection signals
GS1, GS2, and GS4. See Section 2.3.30, “Spindle positioning function” for the details of spindle gear
selection signals GS1, GS2, and GS4. The control unit calculates specified speed Sc based on
spindle gear selection signals GS1, GS2, and GS4 and spindle motor command voltage signals RI0
to RI12.
Actual spindle speed Sa is obtained from feedback pulses from the position coder mounted on the
spindle. The pulses are detected at 64–ms cycle and converted to rpm. Specified speed Sc is then
compared with actual spindle speed Sa. If the difference between them exceeds allowable speed fluc-
tuation Sm, an alarm is issued.
Example 1 When an alarm is issued after the specified speed is reached
Command speed
Actual spindle sped
Sm max
Sc
Sm min
Sm
Sm
Sq
Judgement
No
Judgement Judgement
Alowable
maximum speed
Speed which has
reached the
command speed
Allowable
minimum speed
Time
Another speed
is instructed
Judgement start Alarm
Example 2 When an alarm is issued before the specified speed is reached
Command speed
Actual spindle sped
Sm max
Sc
Sm min
Sq
Judgement
No
Judgement Judgement
Allowable
maximum speed
Speed which has
reached the
command speed
Allowable
minimum speed
Time
Another speed
is instructed
Judgement start Alarm
Time Tp