Offsetting from finish date to start date

Offsetting from the finish date to the start date, depends on the order type. Offsetting differs for production orders, purchase orders, and distribution orders.

Offsetting production orders

These factors determine how a production order is planned/offset:

  • Routing planning
    If the estimated start date of the production order is before the date in the Start of Fixed Lead-Time Horizon (SFC) field of the Items - Planning (cprpd1100m000) session, you deal with short term planning. Therefore, production orders are planned in a detailed way. The production order is planned with routing, routing operations and quantity. The order lead time is the sum of the operation lead times.
  • Fixed order lead time

    If the estimated start date of the production order is after the date in the Start of Fixed Lead-Time Horizon (SFC) field of the Items - Planning (cprpd1100m000) session, you deal with long term planning. Therefore, production orders are planned in a less detailed way (to gain performance). If the estimated start date falls after the date in the Start of Fixed Lead-Time Horizon (SFC) field, details are skipped. Instead, the fixed order lead time is used to plan, without using routing and operations.

    The estimated start date is determined by planning backwards the fixed Order Lead Time that is defined in the Items - Production (tiipd0101m000) session.

  • Generic items
    Sometimes, the production order involves a generic item. The generic routing has a set of possible operations. The choice of operations depends on the configuration, so in a planned order, for a generic not yet configured demand, all operations are planned. This offsetting differs from normal items.
Routing planning

A production order includes a series of operations. The sequence of operations is managed by the routing. One item can have multiple routes, with various sets of operations, depending on order quantity.

In addition, you can model phantom items, which result in a network of parallel operations. The impact of phantom items on planning is described later.

One planned operation includes these lead time components:

  • Queue (Next Operation)
  • Average Setup
  • Production run time, based on cycle time
  • Wait
  • Move

Production time can be either quantity dependent or fixed, which is determined by the Fixed Duration check box.

These options are available:

  • Normal, no fixed duration ( Fixed Duration check box is cleared)
Production time = cycle time * order quantity / routing quantity
  • Fixed duration ( Fixed Duration check box is selected)
Production time = cycle time

If you use the detailed routing information, the offsetting of two operations is as follows:

Production orders, offset operations
Production orders, offset operations
Operation overlap

The previous figure shows how you can plan two operations sequentially. Operation 20 starts when operation 10 is finished. If you use a transfer batch quantity or percentage, operation 20 can start when operation 10 is partly finished.

Production orders, operation overlap
Production orders, operation overlap
Network of phantom operations

If item A has phantom items B and C as components, the production order contains the operations of item A, as well as of items B and C. If, for example, phantom B is required on the third operation of item A, and C is required on the second operation, the planning is as follows:

Production orders, network of operations
Production orders, network of operations
Capacity

The required capacity for a production order is derived from the operation lead times. Occupation factors indicate how many men or machines are involved in the operation. Only the setup time and the production time require capacity.

For the two types of production times, the capacity calculations are as follows:

  • Normal, no fixed duration:
Man hours = average set up * man occupation for set up + cycle time * order quantity  * man occupation for production / routing quantity
Machine hours = average set up * machine occupation + cycle time * order quantity  * machine occupation / routing quantity
  • Fixed duration:
Man hours = average set up * man occupation for set up + cycle time  * man occupation for production / routing quantity
Machine hours = average set up * machine occupation + cycle time * machine occupation / routing quantity

In the Enterprise Planning resource plans, either man or machine capacity is stored based on the Critical Capacity for Planning field in the Work Centers (tirou0101m000) session.

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