Takt-Based Scheduling (SAP Library - Planning Table (PP-REM))

Takt-Based Scheduling

Use

Along with sequencing, takt-based scheduling is a central function of the Sequencing module. Once the system determines the sequence of the planned orders for the specified planning period, it calculates the production start and finish dates and the lead time for every planned order. As opposed 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 the production rates and the number of takts from 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.

Integration

Scheduling master data

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 production rate (for example, 100 pieces per hour) according to which the structure of the line hierarchy is defined on a long-term basis. The maximum production rate remains constant along the time axis. The reciprocal value of the maximum production rate is the minimum takt time.

The planned production rate which you define manually in the line hierarchy or automatically using line balancing. The planned production rate determines the yield for the period in question. The reciprocal value of the planned production rate is the planned takt time.

The rate used for takt-based scheduling. You can carry out takt-based scheduling using the maximum production rate or the planned production 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. You use the operative rate to adjust scheduling to compensate for unexpected changes in production.

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. Then in Sequencing, the system multiplies this factor by the valid planned rate of the period which overrides the planned production rate in scheduling ( see also : PP Line Design; Material-Dependent Production Rate).

The operation time of the production line which you define by your shift definition in the work center ( See also:PP Line Design; Creating Work Centers).

Other scheduling types

If you want to display capacity data, you can also 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 system also retains the results of sequencing.

Features

Takt-based scheduling using the maximum production rate.

Here, the system uses the maximum production rate to determine the time in which a material can be processed in one takt. This means that this time and therefore also the speed of the line is constant. You can use the planned rate to accommodate any changes to production by not placing a material on the production line in every takt.

Takt-based scheduling is clafified 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 using the planned production rate.

The only parameter in this type of takt-based scheduling is the planned production rate. The reciprocal value of the planned production rate determines the time in which a material can be processed in one takt. This means that this time depends on the current period and therefore the speed of the line is also variable. The reciprocal value of the planned production rate also determines the intervals in which a material is placed on the line and the intervals in which a material leaves the production line.

If you use the planned production rate for takt-based scheduling, the system calculates this retention period (RP) according to the following formula:

RT = (no. of takts - 1) * planned takt time + order quantity * planned takt time

The formulas specified 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 in 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, enter a medium-term planning period 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.

Activities

You can display the dates of a planned order by double-clicking the order bar in the sequence schedule.