Mitsubishi Electric MELSEC-L LD75P User Manual page 602

The cutter shaft starts from the moment the feed shaft has completed feeding the stock , and the feed shaft
starts from the moment the cutter shaft has returned to the standby position . Actually, however, there is a
delay of start time Ts (1.5 to 2.0ms) from when the LD75 receives a start request until it outputs pulses. The
system's tact time can be reduced by the shortening of this delay with the Pre-reading start function.
The feed shaft stands by during the stop time Tw.
Hence, pre-reading of the next data starts during the stop time Tw. If Tw is a certain period of time, the analysis of
the next data is completed during that period, and the system is placed in an execution prohibition flag OFF
waiting status. Therefore, replacing the positioning start timing at  with the execution prohibition flag OFF
allows the time from when the axis operation request turns ON until pulse output starts to be reduced to within
1.3ms in the program.
(2) Control precautions
• The time required to analyze the positioning data is up to 7ms.
• After positioning data analysis, the system is put in an execution prohibition flag OFF waiting status. Any
change made to the positioning data in the execution prohibition flag OFF waiting status is not reflected on
the positioning data. Change the positioning data before turning ON the positioning start signal.
• The pre-reading start function is invalid if the execution prohibition flag is turned OFF between when the
positioning start signal has turned ON and when positioning data analysis is completed (Ta < start time, Ta:
 Page 598, Section 12.7.7 (1)).
• The data No. which can be executed positioning start using "[Cd.3]Positioning start No." with the pre-reading
start function are No. 1 to 600 only. Performing the pre-reading start function at the setting of No. 7000 to
7004 or 9001 to 9004 will result in the error "Outside start No. range" (error code: 543).
• Always turn ON the execution prohibition flag at the same time or before turning ON the positioning start
signal. Pre-reading may not be started if the execution prohibition flag is turned ON during Ta after the
positioning start signal is turned ON. The pre-reading start function is invalid if the execution prohibition flag
is turned ON after positioning start (pulse output) with the execution prohibition flag OFF. (It is made valid at
the next positioning start.)
600