Example: Determining the Operation Dates 

An order contains two operations (operation 10 and operation 20). The order quantity is 100 pieces and the order start date has been set to Tuesday, May 2nd. The scheduling type is forward scheduling.

Duration of the Individual Operation Segments for Operation 10

First, the system calculates the duration of the time segments for the operations (see Duration of the Operation Segments). To calculate the execution time, the system uses the formulas stored in the work center for setup, process or teardown and takes into account the performance efficiency rate specified for the individual standard values:

1 hour setup + 4 hours processing + 1 hour teardown = 6 hours execution time

The operation lead time is calculated by adding queue time and wait time to the execution time:

4 hours queue + 6 hours execution + 15 hours wait = 25 hours lead time

A move time of 0.5 hours is maintained between operation 10 and operation 20. This is assigned to the preceding operation (operation 10).

Calculating the Operating Time for Operation 10

The operating time of the work centers is calculated as follows:

The system calculates the working hours (standard available capacity) of the work center:

16:00 work finish - 7:00 work start = 9 working hours

The break times are subtracted from the working hours:

9 working hours - 1 hour breaks = 8 hours

The operating time of the move time is specified in the move time matrix: The shift starts at 7:00 and finishes at 17:00 and is a total of 10 hours.

Selecting a Calendar

The system now selects the valid factory calendars. The same factory calendar is maintained in both work centers. According to the factory calendar, work is carried out from Monday to Friday.

Calculating the Dates for Operation 10

The system has now collected all information relevant to scheduling and has calculated the duration of the individual operation segments. The next step is to calculate the operation dates. The system lines up the order floats and the individual operation segments along the time axis, taking into account the operating times.

The production order is scheduled using forwards scheduling so the system starts with the order start date (Tuesday, May 2nd).

Starting at the order start date, the float before production of one day is first added to the time axis. The scheduled start of the order is, therefore, Wednesday, May 3rd.

Starting from the scheduled start, the operation segments are now lined up on the time axis and the breaks are distributed proportionally among the individual operation segments.

Calculating the Operation Dates for Operation 10 Without Queue Time (Earliest Date)

Segment

Duration

Operating time/day

Start

Finish

Setup

1 hr

8 hr

3rd May 07:00:00

3rd May 08:07:30 1)

Process

4 hr

8 hr

3rd May 08:07:30

3rd May 12:37:30 2)

Teardown

1 hr

8 hr

3rd May 12:37:30

3rd May 13:45:00

Wait

15 hr

24 hr 3)

3rd May 13:45:00

4th May 04:45:00

Move

0.5 hr

10 hr

4th May 07:00:00

4th May 07:30:00

1) The wait time is scheduled independently of the factory calendar.

2) The duration of the setup results from: Setup = 1 hour * (1 + 1/8) = 1 hour 7.5 minutes

3) The duration of processing results from: Processing = 4 hour * (1 + 4/8) = 4.5 hours

Calculating the Operation Dates for Operation 10 with Queue Time (Earliest Date)

Segment

Duration

Operating time/day

Start

Finish

Queue

1 hr

8 hr

3rd May 07:00:00

3rd May 11:30:00 AM

Setup

1 hr

8 hr

3rd May 11:30:00

3rd May 12:37:30

Process

4 hr

8 hr

3rd May 12:37:30

4th May 08:07:30

Teardown

1 hr

8 hr

4th May 08:07:30

4th May 09:15:00

Wait

15 hr

24 hr *

4th May 09:15:00

5th May 00:15:00

Move

0.5 hr

10 hr

5th May 07:00:00

6th May 07:30:00

Calculations for Operation 20

The sum of wait, setup, processing and teardown time totals 14 hours. The operating time per day is 8 hours, as for operation 10. Teardown finish (latest date) is, as a result, scheduled for 8th May at 9:45:00 starting from 6 th May at 7:30, because the factory calendar is not used on May 6 th and 7 th. The wait time of operation 20 is 15 hours. Since the wait time is scheduled independently from the factory calendar, it can be scheduled outside the working/operating time valid for this day. The scheduled finish falls on May 9 th. Since operation 20 is the last operation in the order, there is no subsequent move time

Finally, the float after production is added to the time axis. The float after production for this order is 1 day. The order finish date is therefore 10th May.