Configuring Production Order Scheduling

Depending on your business requirements, you can schedule orders either forwards or backwards in time: In forward scheduling, a production order is scheduled forwards in time starting from the basic start date (for example, manually entered or copied from the planned order); in backward scheduling, a production order is scheduled backwards in time starting from the basic finish date (for example, manually entered or copied from the planned order).

The previous graphic shows all the possible elements contributing to the total lead time of a production order: The total lead time of a production order lies between the basic start date (BS) and the basic finish date (BF) and is represented by the upper green bar in the figure. The float before production lies between the basic start date (BS) and the scheduled start date of the first operation (SS), and the float after production lies between the scheduled finish date of the last operation (SF) and the basic finish date (BF). By specifying sufficient buffer times, you obtain better production stability as you can react to any unforeseen events that can occur in the production process. However, if your buffer times are too high, your production resource utilization can decrease. If necessary, for example in case of delays of other orders or a machine breakdown, the buffer times can be automatically reduced by the system.

The operations are scheduled in the order of their operation numbers. In the case of forward scheduling, the system starts from the lowest operation in ascending order. In the case of backward scheduling, the system starts from the highest operation in descending order. Each operation has the time elements: queue time, setup time, processing time, teardown time, wait time, and move time. The sum of all time elements (except move time) defines the lead time of an operation. The queue time and the move time serve as time buffers for the operations. Similar to order buffer times, they can also be reduced if necessary.

As you can see in the figure, the queue time lies between the earliest start (ES) and the latest start (LS) of an operation. The wait time lies between the earliest finish (EF) and the latest finish (LF) of an operation. Let us consider two extreme scenarios: In the first scenario, the queue time is completely consumed. In this case, the worker begins setting up the work center at the latest possible point in time. In the second scenario, the queue time is not consumed at all. In this case, the worker begins setting up the work center at the earliest point in time. Henceforth, each operation has an earliest and a latest start and end date. If the order is executed as planned, the actual operation start date lies somewhere within this time horizon.

Wait time is usually used to define the time the next operation must wait until it can be started, for example, if paint must dry before the next operator can touch the manufactured material. Move time is used to define the time required to move the manufactured material from one work center to the next one. Although the move time is a time element shared by two subsequent operations, it is always attributed to the first operation. Starting from the latest finish (LF), the system adds wait and move time, respectively, to calculate the earliest start (ES) date of the next operation. The latest finish (LF) date of the last operation in the order corresponds to the scheduled finish (SF) date of the order.

After the manufactured good is produced, it must be moved from production to the warehouse. This time is usually represented using the goods receipt processing time.

If a production order is created with reference to a sales order, the basic finish date of the production order is determined in backward scheduling based on the scheduling of the sales order. The time segments of sales order scheduling (for example, pick/pack, load, and transit time) are also shown in the figure.

The scheduling parameters for production orders are created and maintained for the key fields plant, order type, and production supervisor in the configuration activity Define Scheduling Parameters for Production Orders.

When you open the configuration activity, you first find an overview of all the entries that have already been created, as shown in the previous figure. You can create new entries or display or change the details of already existing entries.

In the detail view of an entry, you find the following information and control settings:

• Scheduling:

  This setting is always selected and cannot be deselected, as production orders are always subject to detailed scheduling.

• Generate capacity requirements:

  The selection determines that also capacity requirements are generated when the order is scheduled.

• Adjust dates:

  You specify whether and how the basic dates are adjusted to the production dates (for example, when deadlines are exceeded).

• Scheduling control for detailed scheduling:

  • Scheduling type:

    Here you specify in which direction the scheduling is to be carried out and whether it is to be carried out to an exact time. You can also specify that a scheduling run is only used to generate capacity requirements.

  • Start in the past:

    Here you specify how many days an order can lie in the past before today scheduling is triggered.

  • Automatic scheduling:

    Here you specify whether scheduling is carried out automatically on saving the order.

  • Automatic log:

    Here you specify whether the log is displayed automatically on scheduling.

  • Scheduling with breaks:

    Here you specify that the exact time a break occurs must be considered. If you set this indicator, it is no longer possible that a calculated time occurs during a break time.

  • Scheduling from production dates:

    Here you specify which dates have to be entered when you create or change an order. If the indicator is set, you must enter one or more production dates (scheduled dates). If the indicator is not set, you must enter one or more basic dates.

  • Shift order:

    This indicator defines that for partially confirmed operations the actual dates already existing are not considered during a new scheduling run.

• Requirements date determination for components:

  • Operation segment:

    Here you determine to which operation segment (set up, processing, tear down) the components with a positive requirements quantity are assigned.

  • Latest staging date:

    This indicator stipulates where the requirements date of a component lie. Set the indicator if the requirements date is the latest scheduled date of the operation. If you do not set the indicator, the requirements date is the earliest scheduled date of the operation.

• Reduction:

  Here you define the reduction strategy for the automatic reduction of the order floats.

  • Reduction type:

    Here you define whether in the order or in the collective order all the operations are to be reduced or only those along the critical path.

  • Maximum reduction level:

    Here you define up to which maximum reduction level the reduction takes place.

  • % reduction in floats:

    Here you define to what percentage the float before and after production in every reduction level is to be reduced.

You define the required scheduling margin keys in the configuration activity Define Floats (Scheduling Margin Key) with plant reference.

As an example, the figure shows the definition of several scheduling margin keys in different plants with different settings for the floats and time horizons.

You assign a suitable scheduling margin key to each of your products in the material master. If an order is created, the scheduling margin key of the product is copied to the order.