Quantities, measures, and masses for Sustainability

Quantities for each item in the BoM are specified in the Quantity and Unit of Measure. This information is required to calculate Reported Mass values.

In general, the quantity for an item can be specified in one of two ways:

absolute terms: An explicitly-specified Quantity and Unit of Measure. For example, a material with Quantity = ‘0.25’ and Unit of Measure = ‘kg’, or a part with Quantity = ‘4’ and Unit of Measure = ‘Each’.
percentage of the parent item: By mass. For example, a material that constitutes 100% of the mass of the part .

If you specify the Quantity using a non-mass Unit of Measure (for example, ‘Each’ for a Part, or a unit of area for a Joining & Finishing Process), then additional information about the mass that this quantity represents will be required, in order for the analysis to calculate the mass of the item in the BoM.

If this information is available in the database, it will be retrieved and displayed in the Mass per UoM (mass per unit of measure) and Mass Unit columns, either when the part is first added to the BoM or when the BoM is analyzed.
Otherwise, you can provide this information when defining or editing the BoM.
Note: The additional mass information that you specify in the Mass per UoM and Mass Unit columns must be the mass for the Unit of Measure you specified. For example, if the Quantity of a Standard Part has been specified in units of area (m²), then the Mass per UoM must be specified as a mass per area (kg/m²).

Mass data that has been specified in the BoM or retrieved from the database, and appears in either the Quantity and Unit of Measure columns or the Mass per UoM and Mass unit columns, represents a Measured Mass.

When the BoM is analyzed, a Reported Mass is calculated for each item.

There are some constraints on how quantities, measures, and masses can be specified in the BoM, depending on the type of BoM item.

Table 1. Options for specifying Unit of Measure and Quantity for Sustainability
BoM item type	Options for specifying Unit of measure and Quantity
Part Assembly	Each – must be specified as an integer (number of parts) Unit of mass - this can be used to specify a quantity for a Standard Part (for example, 0.05kg of NiMH battery) Unit of length, area, volume (for example: m, m², m³) - These can be used to specify a quantity for a Standard Part (for example: 5cm of electrical wire) Box – this can be used to specify parts that are supplied in bulk (for example: 0.5 of a box of fasteners) % – the percentage (by weight) of the part's parent assembly
Material	% - the percentage (by weight) of the parent item - for example, a material that constitutes 100% of the mass of the part. For Sustainability analysis, you can only assign one material per part, so its percentage (by weight) of the part must be 100%. Unit of mass (for example, kg) - for example, the mass of a billet of material. Note: Both options represent the final mass of the material after processing. If you assign subtractive secondary processes to the material, the initial mass of material before processing (Mass before processing) will be calculated as part of the Sustainability analysis, based on the amount of material removed by the secondary processes.
Process Primary Secondary Joining and Finishing	The units of measure that can be specified depend on the Process type (Primary, Secondary, or Joining and Finishing) and the Process dimension type. The available options for Unit of Measure may include the following. For a Primary process: % - the percentage (by weight) of the parent item (material) – for example, a Primary Process that is used to create 100% of the material required to make the part. For Sustainability analysis, you can only assign one Primary Process per material, so its percentage (by weight) of the material must be 100%. But note that this is 100% of the initial mass of material required to make the part, before any secondary processing. For a Secondary process that is subtractive (removes material): Unit of 'Mass removed' (for example, kg). % - the percentage (by weight) of the parent item's mass immediately before this process is applied. For example, a subtractive process that removes 10% of the mass of the material. For a secondary process that is non-subtractive (does not remove material): Mass of part - the process is assumed to apply to 100% of the mass of the material, for example, deep drawing Unit of length - for example, laser machining Unit of area - for example, cutting and trimming For a Joining & Finishing process that is applied to a part: Unit of length - for example, welding Unit of area - for example, electroplating Unit of mass - for example, adhesive Note: The quantity specified for the Joining & Finishing Process is used to calculate the environmental impacts of that process. The process is assumed not to change the final mass of the part.
Location	Not applicable - does not require a Quantity or Unit of Measure
Transport	Unit of length - the distance that was transported.