Considerations for Multi-Level BOM Roll-up Calculations
When calculating the value for the usage of a specific part in the structure, the value for the part is multiplied by the usage quantity. The individual calculations are then added together for the next higher level in the structure.
For example, a part with an attribute of type Real Number that has a value as 2 and a quantity of 3 will have its calculated value = (attribute value * quantity) = (2*3) = 6 where another part with an attribute that has a value of 3 with a quantity of 1 will have its calculated value = (attribute value * quantity) = (3*1) = 3 which summed together for the next higher level part is 6+3=9.
 |
• The attribute value can be Integer, Real Number, or Real Number with Units.
• Quantity can be Integer or Real Number, which includes zero and negative numbers.
|
Expanding the mechanics for a single-level calculation to consider multiple levels brings in the possibility that the next higher level may have a defined value that is considered more accurate than the value that might be rolled up from the sum of the individual components used. Here, the definition of the part is critical:
|
Part Definition
|
Use Defined Value
|
|
|---|---|---|
|
Configurable
|
No
|
Roll-up value from a specific configuration is more likely to be accurate than a static value from an overloaded configuration.
|
|
Collapsible
|
No
|
|
|
Configurable End Item
|
No
|
|
|
End Item
|
Yes
|
Defined value is more likely to contain more values from product measurements.
|
|
Phantom
|
No
|
Does not represent a physical part.
|
|
Gathering
|
No
|
Does not represent a physical part.
|
|
Standard
|
Yes
|
Defined value is more likely to contain more values from part measurements.
|
The exception to the above table is the top-level part which does not use the defined value and, instead, always reports the calculated roll-up value.
|
|
In the event that the roll-up calculation identifies that a required value has not been defined, a message is displayed indicating that the result could not be calculated.
|
 |
It is recommended to define values for standard part used at the lower levels of the structure.
|