Example: Calculating Operation Dates

A routing consists of operation 10 and operation 20. You want to schedule for a quantity of 100 pieces. You select a basic start date of Tuesday the 2nd. The scheduling type is forward scheduling.

Duration of Individual Operation Segments

The system first calculates the duration of the operation segments. Using the formulas in the work center, it calculates the lead time of operation 10. For each standard value, the performance efficiency rate is taken into account.

setup	+ processing	+ teardown = execution time
0.5 hours	+ 6.5 hours	+ 0.5 hours = 7.5 hours

To calculate the lead time of the operation, the queue time and the wait time are added to the execution time:

queue	+ execution	+ wait = lead time
7 hours	+ 7.5 hours	+ 15 hours = 29.5 hours

The move time between operation 10 and operation 20 is 0.5 hours. It is defined in the first of the two operations, that is, operation 10.

Operating Time

The operating times of work centers are calculated as follows:

The working hours at the work center are calculated:

work finish	- work start	= working hours
16:00	- 8:00	= 8 hours

The break times are subtracted from the working hours:

working hours

- breaks

= 8 hours -1.33 hours = 6.67 hours

The capacity utilization rate is taken into account:

6.67 hours

* capacity utilization rate

= 6.67 hours * 90% = approx. 6 hours

The operating time for the move is defined in the move time matrix using a shift start of 7:00 and a shift finish of 17:00. It corresponds to 10 hours.

Calendar Selection

Next, the system selects the valid factory calendars. The same factory calendar is specified in both work centers. According to the factory calendar, Monday through Friday are working days.

Dates

After the durations of the individual operation segments have been calculated, the system determines the operation dates. For this purpose, the system lines up the order floats along the time axis taking into account the operating times.

Since forward scheduling is carried out for the routing, the system starts from the basic start date, that is Tuesday the 2nd.

Starting from the basic start date, the system first adds the float before production (one day, in our example) on the time axis. The scheduled start is Wednesday the 3rd.

Then, the operation segments of the two operations are added on the time axis.

Calculation of the Operation Dates for Operation 10

Segment	Duration	Time/Day	Start	Finish
queue	7 hours	6 hours	Wed., 3rd8:00	Thurs., 4th9:20
setup	0.5 hours	6 hours	Thurs., 4th9:20	Thurs., 4th10:00
processing	6.5 hours	6 hours	Thurs., 4th10:00	Fri., 5th10:40
teardown	0.5 hours	6 hours	Fri., 5th10:40	Fri., 5th11:20
wait	15 hours	24 hours *	Fri., 5th11:20	Sat., 6th2:20
move	0.5 hours	10 hours	Mon., 8th8:00	Mon., 8th8:30

* The wait time is scheduled without regard to the factory calendar.

The same procedure is now carried out for operation 20:The sum of queue time, setup time, processing time and teardown time totals 19 hours. The operating time per day is 6 hours. Consequently, the finish of the setup is scheduled for Thursday the 11th at 16:00. The wait time for operation 20 is 5 hours. Since the wait time is scheduled without regard to the factory calendar, it does not have to be within the operating time defined for the day. Operation 20 is the last operation in the order, therefore there is no move time.

Finally, the float after production (one day, in our example) is added on the time axis. Therefore, the basic finish date of the order is Friday the 12th.