SAP PP Scheduling Process

The scheduling process is useful for calculating start date or time and end date or time in a production order or operation.

There are two methods of scheduling process in production planning. They are –

  • Basic dates scheduling –
    It is calculated by the values like processing time of GR, in-house production time and planned delivery time from material master. It calculates the basic start date and basic finish date of an order.
  • Lead time scheduling –
    It takes the values from a routing operation times for calculating an operation start date, start time, end date and end time.

SAP PP Scheduling Types –

There are various scheduling types that commonly used in Production Planning and production orders. They are –

  • Forward scheduling
  • Backward scheduling
  • Today scheduling
  • Only capacity requirements
  • Forward scheduling - The system will schedule the order considering basic start date and decides schedule end dates.
  • Backward scheduling - The system will schedule the order considering basic end date and try to decide the schedule start date.
  • Today scheduling - The system will calculate schedule end date based on schedule start date as current date.
  • Only capacity requirement - In this scheduling the basic dates will be copied as the schedule dates and the operations are not scheduled.

Basic Dates vs Schedule Dates –

The basic finish dates will be calculated depending on requirement date(demand). The system adds lead times defined in MRP 2 view to that for deciding the basic start date.

It also adds the opening period defined in scheduling margin key. An opening period is number of days needed for a planner to convert a planned order to a production order.

The production starting date or time and finishing date or times will be calculated by scheduling individual operations specified in routing. Then the schedule starting and finishing dates are calculated by adding floats (specified in scheduling margin key) to the production start dates.

Control Key in SAP PP Scheduling –

The control key determines that if an operation needs to be scheduled or not. If the scheduling indicator is activated then the system will schedule the operation. Otherwise, it will not.

SAP PP Scheduling Components –

while scheduling an operation the system uses the following from master data.

  • Operation times and base quantity from routing.
  • Formula for scheduling from work center.
  • Inter-operation timings from routing or work center.
  • Break time and shift sequences.

Operation Time in Routing –

In routing every operation consists of setup, machine and labor hours needed to produce the base quantity. The system uses this information in calculating total time needed for the operation.

Let us consider that in routing the machine time entered as 180 mins for the base quantity of 600 PC. When an order for the quantity of 1800 PC is created, the system will calculate the total time required for the operation as follows.

Total time required for 1800 PC = (180 / 600) * 1800 = 0.3 * 1800 = 540 minutes.

Formula for Scheduling Time –

The calculation is maintained inside the scheduling formula in a work center.

Operation time = (Machine time * Operation quantity /Base quantity) /Operation split.

The operation split is specified in routing, in the example here it is '1'.

Inter-Operation Time –

This is time between operations in the work centers. There are 3 times available in sap.

They are –

  • Queue time –
    It is time needed before processing the material in the work center.
  • Wait time –
    It is time that the material kept after processing in the work center.
  • Move time –
    It is the time needed to move the material from one work center to another after its processing.

Example -

Let take an example from the fastener industry dealing with manufacturing of bolts and nuts. Here consider the final stage of operation that is the bolts produced will be painted and packed. Before the painting, the previous batches will be in queue for 20 mins which is queue time because of preceding operation and painting operation. Then the material must wait for 15 mins that is wait time for drying. Then the material is moved for packing location which takes 10 mins that is move time.

Break Time and Shift Time –

The system calculates the break time from work center master data. If any shift sequences are specified in the work center then system takes break time in shift break as per the shift sequences. Otherwise, it will take the total break time given in the capacity header.

The break time specified in the capacity header is total break hours between starting and ending time. Here the total of 1 hour of break time is from 08 AM to midnight so the available capacity is 16 hours.

If the operation time of an order is 7 hours then the system will calculate break time as -

Break time for 7 hours = 1/17 * 7 = 0.41 hours.

Reduction Strategy in Scheduling –

When the system try to schedule an operation, it will try to schedule it first within basic dates. If the schedule starting date may come before basic dates then system try to adjust dates by reducing inter-operation timings except wait time. While scheduling an operation, the system try to schedule it within basic dates first.

As above said, it is possible to reduce queue time and move time but not wait time. Because the painted bolts have to wait for 15 mins to get dry.

It enables to maintain standard and minimum queue time of work center and routing. Here the system considers standard queue time first but if schedule dates comes before or after basic dates then it takes minimum queue time.

When system finds the dates are not within the basic dates after considering the minimum time then it applies reduction strategy described in routing operation.

The system applies reduction step by step for each of reduction levels.

  • Try to reduce 50% of the queue time.
  • Try to reduce 100% of queue time and move time.
  • Try to reduce 100% queue and move times and try to apply operation overlap defined in routing operations.
  • Try to reduce 100% queue and move times and try to apply operation overlap and operation split defined in routing operations.

Here the operation overlap and splits may reduce the lead time of an operation.

Factory Calendar in Work Center –

While scheduling an operation or production order, the system considers factory calendar from plant and eliminates non-working days and holidays. If there is a business scenario where production calendar vary from plant calendar then it allows to assign a production specific calendar in work center. So the system considers working days from work center rather the plant calendar when scheduling.