
B–62073E–1/04 2. INTERFACE BETWEEN CNC AND PMC–NA OR NB
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2.3.67 Switching between synchronous and independent control
A tool can be moved along an axis according to a normal movement command for the axis or moved in synchro-
nization with tool movement along another axis. The type of movement can be selected with an input signal
from the machine. A machine which requires synchronous movement along the Y–axis and X–axis is de-
scribed below as an example. The description, however, applies also to arbitrary axes that are actually used.
The tool movement along the Y–axis can be selected from the following two methods using an input signal from
the machine:
(i) As usual, a tool is moved along the Y–axis according to program command Yyyyy. (Hereafter called inde-
pendent control)
(ii) When a tool is moved along the X–axis with program command Xxxxx, the tool is also moved along the
Y–axis in synchronization with the tool movement along the X–axis. (Hereinafter called synchronous con-
trol)
In the synchronous control, an X–axis movement command is simultaneously given to the servo motor for the
X–axis and the servo motor for the Y–axis. No correction is made, however, for synchronization errors, such
as detecting the deviation between two servo motors and correcting one servo motor to reduce the deviation.
The following is the block diagram of synchronous control for the Y–axis and X–axis.
Calculation of
movement command
Positioning
Linear
interpolation
Circular
interpolation
Thread
cutting
X-axis
movement
command
X-axis related
I/O signal
processing
CMR
CMR
Y-axis related
I/O signal
processing
Position
deviation
X-axis
motor
DMR
Position
detector
Position
deviation
Y-axis
motor
DMR
Position
detector
Synchronous control for the Y–axis and X–axis is possible only during automatic operation by tape command,
manual data input, and memory command. Synchronous control for the X–axis and Y–axis is not performed
during manual operation by continuous manual feed, manual handle feed, or incremental feed.