Mitsubishi Electronics QD75D, QD75P user manual Feed shaft Start

12 CONTROL SUB FUNCTIONS

MELSEC-Q

V
Feed shaft		t
Start	Stop time	Start
time	Tw	time
Ts		Ts
Cutter shaft		t
Start
time
Ts
Feed shaft
start request
Cutter shaft
start request
1		2

Fig. 12.50 Operation timings of system example

The cutter shaft starts from the moment the feed shaft has completed feeding the stock " 1 ", 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 (6 to 7ms) from when the QD75 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.

In Fig. 12.50, 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 3ms in the sequence program. (Refer to Fig. 12.48)

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