Units of Measure

Although the majority of your parts will be used, priced, quoted, and inventoried as individual units (each), Aligni allows you to create additional units as required for your parts. Aligni differentiates between “Use-As Units” and “Buy-As Units” and allows you to define unit conversions between any two units.

Users with “can manage data” can create and edit units through the settings pages.

User-customizable “Units” are provided by Aligni in order to resolve ambiguity between what is used on a part list, what is ordered on a purchase order, and how certain parts are costed.

  • Use-As Unit – This specifies how the part is used on an assembly BOM. Typical part units would be: eachminutes (labor), milliliters (fluids), inches (wire).
  • Buy-As Unit – This is used to specify any difference between a part usage quantity and purchase quantity. This is associated with a vendor part number. For example, 40-oz. bottle (fluid), 80-pin strip (breakaway headers).

Allow Fractional

Many units will require integer quantities. Examples include “each” or “pin”. In these cases, set “Allow Fractional” to false and Aligni will enforce a requirement that the quantities specified are integers.

Other units, such as “hours” or “milliliters”, may allow for a fractional quantity. In these cases, set “Allow Fractional” to true and Aligni will allow fractional values to be specified for the quantity.

Unit Conversions

UnitConversions@2xWhen you enter units in Aligni, you need to provide conversion factors between any pair of units that are convertible. Unit conversions tell Aligni how to convert between buy-as units and use-as units, when appropriate. They also establish which units are available as buy units for a particular part.

Note that unit conversions are unidirectional. Each defined unit conversion has a clear “from” unit and “to” unit. In most cases, you will need to define a conversion from the buy-as unit (e.g. 100-pc package) to the use-as unit (e.g. each).

Min/Mult or Buy-As Unit?

There are several instances where it may be tempting to create a new Buy-As Unit. For example, surface mount resistors are often sold and delivered in reels of 5,000 or more, so a suitable Buy-As Unit may be “5,000-pc tape & reel”. However, resistors are almost always quoted and purchased individually, but with a minimum and multiple order quantity of the reel size (5,000 each). The parts are also inventoried in “each” as well. We do not suggest creating new units for packaging sizes when the quoting and purchasing typically refer to “each” units. In these cases, it is better to follow the min/mult order quantities.

headerElectrical pin headers are often shipped as “breakaway” modules that can be snapped to a selected length of pins. In these cases, the suppliers ship the modules in units such as 40-pin strip or 80-pin strip. During assembly, these strips may be snapped to form smaller sets of 6-pins or 1 pin or whatever is required for the assembly. Since the supplier quotes and sells the completed strips, it makes sense to setup new Buy-As Units for “40-pin strip” and “80-pin strip” and provide appropriate unit conversions to “pin” or “each”.

Example: Resistors (reel components)

reel-capacitorResistors are always used as single units (each), but are available to purchase in single units or 5,000-pc tape & reel. In this case, Digi-Key lists the reels as a separate vendor part number, but the purchase quantity is still each (i.e. to purchase a full reel, you order 5,000 pcs, not 1 reel). The min/mult is entered as 5,000 / 5,000 when quoting because Digi-Key offers a volume discount when buying in reels.

Mfg P/N Use-As Unit Digi-Key P/N Buy Unit Min Mult
RT0603DRD074K7L each 311-4.7KDCT-ND each 1 1
RT0603DRD074K7L each 311-4.7KDTR-ND each 5,000 5,000

Example: Wire (length conversion)

wire-spoolWire is used in inch quantities on part lists. It is typically ordered in much larger spools, however. In this case, the vendor part number will list a different unit than the part itself so that orders are entered with the vendor’s units (such as 100-ft spool), but the product is consumed in smaller units as listed on the bill of materials (such as inches).

Mfg P/N Use-As Unit Digi-Key P/N Buy Unit Min Mult
3055 BK001 inch A2064B-1000-ND 1,000-ft spool 1 1
3055 BK005 inch A2064B-100-ND 100-ft spool 1 1