overlapping between parallel sequence and standard sequence

[BillWang]

Issue: overlapping between parallel sequence and standard sequence

Dear experts,

I have met an issue in SAP ECC6 when using overlapping between parallel sequence and standard sequence.

I built two scenarios.

Scenario 1:
I created a routing with a standard sequence and parallel sequence. Both of the two sequences are set alignment key 1-Alignment with earliest date.

In the standard sequence, there are 3 operations, 0010, 0020, 0030 with the following parameters set.
0010, labor time 1 Min /EA, Overlapping: Continuous flow prod. , Min. Send-ahead quantity 1 EA
0020, labor time 1 Min /EA, Overlapping: Continuous flow prod. , Min. Send-ahead quantity 1 EA
0030, labor time 1 Min /EA, No overlapping

In the parallel sequence(1), there is only 1 operation. This sequence branches from and returns to operation 0010 of standard sequence.
0011, labor time 1 Min /EA, Overlapping: Continuous flow prod. , Min. Send-ahead quantity 1 EA

All the above operations have the same work center in which the working time is from 8:00 to 17:00 without break time.

Now I do the scheduling in the routing with 60 EA using forward scheduling method starting from 5/30 (May 30th). The result is

Standard sequence (sequence 0)
Operation Latest start time Edit Time
0010 30.05.2012 08:00:00 60 Min
0020 30.05.2012 09:00:00 60 Min
0030 30.05.2012 09:01:00 60 Min
Parallel Sequence (Sequence 1, branches from and returns to operation 0010 of standard sequence)
0011 30.05.2012 08:00:00 60 Min

What I thought is that the latest start time for 0020 should be 08:01:00 instead of 09:00:00, the latest start time for 0030 should be 08:02:00 instead of 09:01:00.


Scenario 2:
I made changes to the parallel sequence (sequence 1), changed the labor time of operation 0011 to 2 Min/EA and added another operation 0021.

Parallel sequence - after change.
0011, labor time 2 Min /EA, Overlapping: Continuous flow prod. , Min. Send-ahead quantity 1 EA
0021, labor time 1 Min /EA, Overlapping: Continuous flow prod. , Min. Send-ahead quantity 1 EA

Then I rescheduled the routing and got the following result.

Standard sequence (sequence 0)
Operation Latest start time Edit Time
0010 30.05.2012 08:00:00 60 Min
0020 30.05.2012 08:01:00 60 Min
0030 30.05.2012 08:02:00 60 Min
Parallel Sequence (Sequence 1, branches from and returns to operation 0010 of standard sequence)
0011 30.05.2012 08:00:00 120 Min
0021 30.05.2012 08:02:00 60 Min

This time, the result looks correct.

Can anybody explain how SAP calculates the latest start time in the scenario 1 and is it correct?

Thank you!
Best regards,
Bill Wang