Operation-Based Yield
The system also supports yield calculation for component requirements based on individual operations within a parent item’s routing. To use this method, you must:
• Set Op Based Yield to Yes in Item Planning Maintenance (1.4.1 or 1.4.7) or Item-Site Planning Maintenance (1.4.17).
• Set Enable Op Based Yield to Yes in MRP Control (23.24).
When operation-based yield is in effect, the Yield % field associated with the item is not used to determine component requirements.
Operation-based yield affects the explosion of bills of material in work orders, repetitive, advanced repetitive, and configured products, as well as MRP.
Using this method typically results in more accurate calculations and prevents overplanning of components. This is especially true in a mature process where yield percentages are highly predictable.
Example
When subassemblies are scrapped at earlier operations, operation-based yield lessens component quantities required for later operations. Consider the following example:
• An order for 100 ITEM-A is entered in the system.
• ITEM-A has four components: COMP-1, COMP-2, COMP-3, and COMP-4.
• The quantity required for each component is one unit per completed assembly.
• Four operations are needed to build ITEM-A and one component is used at each operation. The first component is used at the first operation, the second component at the second operation, and so on for each component.
• Each operation has a yield of 90 percent.
Based on the demand for 100 ITEM-A, MRP generates a planned order for 151, based on the following calculations:
Item Yield = (90% * 90% * 90% * 90%) = 66%
Planned Order Quantity = 100 / .66 = 151 of ITEM-A
The system uses the same calculation for the parent item regardless of the yield calculation method in effect. However, when calculating component requirements, the different methods yield different results, as illustrated in
Operation-Based Yield Example.
Operation-Based Yield Example
|
Operation
|
Component
|
BOM Qty
|
Op
Yield
|
Eff
Yield
|
Op Based Yield
Yes
Comp Qty Req
|
Op Based Yield
No
Comp Qty Req
|
|
10
|
COMP-1
|
1.0
|
90%
|
100%
|
151
|
151
|
|
20
|
COMP-2
|
1.0
|
90%
|
90%
|
135
|
151
|
|
30
|
COMP-3
|
1.0
|
90%
|
81%
|
122
|
151
|
|
40
|
COMP-4
|
1.0
|
90%
|
73%
|
110
|
151
|
Because Operation 10 is the first operation, it requires 100 percent of the components. When Op Based Yield is No, the component quantity is calculated from the yield percentage of the parent item. The system applies the same 66 percent item yield to each operation to determine component requirements of 151, according to the formula:
(100 * 1) / 66%
When Op Based Yield is Yes, the system uses the yield percentages of the parent’s operation records to determine component quantities. Operation 10 has an effective yield of 90 percent. It is anticipated that 10 percent of the parent items are scrapped at this operation.
As a result, only 135 (151 * 90%) parent items are input to operation 20 and only 135 COMP-2 items are needed (135 * 1). Operation 20 also has a 90 percent yield. As a result, only 90 percent of the 135 parent items (122 units) survive to operation 30. This means only 122 COMP-3 items are required, and so on.
As this example indicates, operation-based yield calculation can have a dramatic effect on the requirement for the components associated with the final operations in a manufacturing process.
Important: Operation-based yield modifies only the quantity planned for production. It does not modify the quantity of components consumed by work orders.