Specifying quantity and mass for a BoM item

When you add an item to a BoM, you must specify its quantity, and sufficient information to enable its mass to be calculated.

The quantity for an item can be specified in one of two ways:
  • In absolute terms, by specifying an explicit Quantity and Unit of Measure – for example:
    • a material with Quantity = ‘0.25’ and Unit of Measure = ‘kg’
    • a part with Quantity = ‘4’ and Unit of Measure = ‘Each’
  • As a percentage of its parent item, by mass – for example:
    • In Restricted Substances mode: a surface treatment specification assigned to a part, that constitutes 10% of the mass of the coated part
    • In Sustainability mode: a secondary process assigned to a material, that removes 20% of the initial mass of the material
If you specify a Unit of Measure that is a non-mass unit (for example, ‘Each’ for a part), then additional information about the mass that this represents is required to calculate the mass of the item.
  • If you have added an item from the database (for example, a part that you have added from the data browser), this information may be retrieved from the database and displayed in the 'Mass per UoM' and 'Mass Unit' columns when the part is first added to the BoM.
  • Otherwise, you can provide this information by entering it in BoM Analyzer. You should ensure that this information is available in the BoM wherever possible - if it is not available, then the analysis may be unable to calculate a Reported Mass for the item.
Important: When working in Restricted Substances mode, if you are using the EU REACH Article 33 Declaration report or EU REACH Article 33 Declaration Details report, you must ensure that every part that may contain Substances of Very High Concern has a mass specified in the BoM. If a part's mass is not specified in the BoM, its substance content cannot be included in the report, and the report will be invalid.
  • To specify the quantity in absolute terms:
    1. Double-click in the Unit of measure column, and select the unit you want to use.
      Note: If you specify a unit of measure that is not a mass, then you should also ensure that the mass per unit of measure (Mass per UoM) is specified, where this information is available.
    2. Double-click in the Quantity column, and enter the quantity of that item, relative to a single instance of its parent part, material, or specification.
      For example, if you are specifying a part that occurs 4 times within its parent assembly, specify the Quantity as '4', regardless of the parent item's quantity.
  • To specify the quantity as a percentage:
    1. Double-click in the Unit of measure column, and select %
    2. Double-click in the Quantity column, and enter the percentage by mass, relative to the parent item.

      You can enter any value of zero or above (there is no requirement for percentage values to add up to 100).

      Examples:
      • A part made of a composite that is 80% Material A and 20% Material B: You can specify the mass of the part, and then specify the Quantity of each constituent material as a percentage (by mass) of the part.
      • A single material assigned to a part: You can specify the percentage as 100%.
      • A surface treatment specification, where the area of coverage is unknown: You can specify the mass of the coated part, and then specify the Quantity of the surface treatment specification as a percentage (by mass) of the part, for example, by weighing a sample of coated and uncoated parts.
      • A substance that you have assigned directly to a part in the BoM: You can specify the amount (by weight) that occurs in the finished article as a percentage (by mass) of the part.