Takt-Based Scheduling
Along with the creation of sequences, takt-based scheduling is a central function of the Sequencing module. Once the system has determined the sequence of the planned orders for the defined planning periods, it calculates the production start and finish dates and the lead time for each planned order. In contrast to lead time scheduling, the system does not use the operation times of the rate routing to calculate the lead time in sequencing. Instead, it uses the takt times or rates and the number of takts of the line hierarchy.
Using takt-based scheduling, you can dispatch very large numbers of orders as the system does not have to determine the standard values from the routing nor does it have to create capacity requirements. Moreover, the system does not take the feeder lines into account when scheduling.
In flow manufacturing, the materials remain for the defined takt time in one takt of the production line for processing. The execution times calculated using the routing may vary from this takt time. Therefore, takt-based scheduling provides a more exact result for flow manufacturing than lead time scheduling.
For scheduling, the system uses the following master data which you can create and change in Line Design.
● The number of takts (processing stations) a material has to pass through on the production line.
● The maximum rate (for example, 100 pieces per hour) for which the structure of the line hierarchy is designed in the long term. It is constant over time. The reciprocal of the maximum rate is the minimum takt time.
● The planned rate that you specify per period in the line hierarchy or determine via line balancing. It determines the output quantity for the relevant period. The reciprocal of the planned rate is the planned takt time.
● The basis of takt-based scheduling. You can carry out takt-based scheduling on the basis of the maximum rate or the planned rate.
● The operative rate/takt time. If you specify an operative rate/takt time, the system uses the operative rate/takt time in Sequencing instead of the planned rate. The operative rate serves to adjust the scheduling to short-term or unforeseen changes in employment levels.
● The material-dependent rates. If you created a line hierarchy with no line balancing, you can specify material-dependent rates in the line hierarchy. The system saves these material-dependent rates as a factor. Sequencing then multiplies this factor by the valid planned rate of the period, thus overriding the planned rate in scheduling. (See also: PP Line Design: Material-Dependent Rate.)
● The operating time of the production line which you define via the shift definition in the work centers (See also: PP Line Design: Creating Work Centers.)
If you want to generate capacity data, you can carry out lead time scheduling via the routing in addition to sequencing. To do this, you can carry out an MRP run, for example and choose Lead Time Scheduling with Capacity Planning in the control parameters for scheduling. If you carry out lead time scheduling after sequencing, the dates of sequencing are retained.
● Takt-based scheduling on the basis of the maximum rate
In this form of takt-based scheduling, the system determines the time in which a material can be processed in a takt from the maximum rate. This means that this time and thus also the belt or line speed is constant. You can make allowance for a change in employment levels via the planned rate by not introducing a material to the production line in every takt.
Takt-based scheduling is best illustrated by the time the materials remain on the production line.
RT = (no. of takts - 1) * minimum takt time + order quantity * planned takt time
● Takt-based scheduling on the basis of the planned rate
In this form of takt-based scheduling, the planned rate is the sole parameter. The reciprocal of the planned rate determines the time in which a material can be processed in a takt. This means that this time depends on the current period and thus the belt or line speed is also variable. The reciprocal of the planned rate also determines the time intervals in which a material is introduced to the production line and the intervals in which a material leaves it.
If you use the planned rate as the basis for takt-based scheduling, the system calculates this retention time (RT) according to the following formula:
RT = (no. of takts - 1) * planned takt time + order quantity * planned takt time

The formulas quoted here are simplified. In takt-based scheduling, the system also takes work breaks and queue times into account which may occur due to a sequence change in a sort buffer. If you change the sequence at a sort buffer, the orders in the sort buffer have to wait until the first order of the next sequence arrives at the sort buffer.
● Depending on the view you select (Line-On View/Line-Off View), the system carries out either forward or backward/forward scheduling.
● The system usually calculates the operating time of the production line using the capacity category relevant for scheduling in the work center of the header of the line hierarchy. If you have used sort buffers to split the line hierarchy into buffered sections, you can define different operation times for scheduling for these buffered sections.
See also:
Creating Work Centers (PP Line Design).
● In Sequencing (an operative planning instrument), the system firms all planning orders that lie within the period of examination. The system does not change these firmed planned orders in subsequent planning runs. You can limit the period in which planned orders are dispatched and firmed in sequencing. To do this, specify a medium-term planning horizon in Customizing.
● If you split the production line into buffered sections using sort buffers, the system creates a date record for the planned orders for every buffered section. You can define a line segment of a buffered section as a visualization segment for planning and thus display the dates of this buffered section in Sequencing.
● The system also schedules the planned orders that have not yet been dispatched and sets their start dates to the beginning of the first shift of the planning period.
You can display the dates of a planned order by double-clicking the order bar in the sequence schedule.