6 Interface Between CNC And PLC
6 - 35
When you start execution, the tool starts moving while the controller begins
pre-fetching process. At block N004, the controller execute “V#1 = V#12221”
(planned program position on X-axis) and the tool position at this moment may
be at 1.052. The planned program position on X-axis in this case is 480. If you
try to view V#1 at this moment, it’ll read V#1=480000.
Ex 3:
Viewing the current tool position while executing the program with G65 L50.
Machine coordinate – V#12001 ~ V#12002
Program coordinate – V#12021 ~ V#12022
N001 G01 X300.
N002 G11 P01
N003 X480.
N004 G65 L50 P#99 A1 – (G65 L50 prevents controller from pre-fetching)
N005 G65 L01 P#1 A#12021 – (Current program coordinate on X-axis)
N006 G01 X0.
N007 M02
When you start execution, the tool starts moving while the controller begins
pre-fetching process. At block N004, the controller stops pre-fetching process
and the controller will wait until N003 block is executed. Therefore, when
N005 is executed, the current tool position for X-axis (V#12021) is 480. So,
V#1=480000.
Ex 4:
Viewing the current tool position while executing the program with G31.
Machine coordinate – V#12001 ~ V#12002
Program coordinate – V#12021 ~ V#12022
N001 G01 X300.
N002 G11 P01
N003 G31 X480. P01
N004 G65 L01 P#1 A#12021 – (Current program coordinate on X-axis)
N005 G01 X0.
N006 M02
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