
7.INTERFACE BETWEEN CNC AND PMC B-63945EN/02
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7.1 WHAT IS PMC?
The programmable machine controller (PMC) is a programmable
controller (PC) built into a CNC to perform sequence control for a
machine tool (spindle rotation, tool change, machine operator's panel
control, and so on).
Sequence control is to perform control steps successively in a
predetermined sequence or according to the logic operation.
Programs for performing sequence control for machine tools are called
sequence programs. Generally, sequence programs coded in the
Ladder language are used.
7.1.1 Basic Configuration of PMC
The following is the basic configuration of the PMC:
CNC
Internal
I/O
PMC
Sequence
program
External
I/O
Machine
Internal relay
Signal input to PMC
Signal output from PMC
Fig. 7.1.1 Basic configuration of PMC
The sequence program reads input signals, performs operations, and
outputs results in a predetermined sequence.
7.1.2 I/O Signals of PMC
Input signals of the PMC include signals input from the CNC (such as
M and T function signals) and signals input from the machine (such as
the cycle start button and feed hold signal button). Output signals of
the PMC include signals output to the CNC (such as the cycle start
command and feed hold signal command) and signals output to the
machine (such as turret rotation and spindle stop). The PMC controls
these I/O signals by executing a sequence program to control the
machine tool.