Definition
A part requirement is any condition a finished part must meet: a dimension, a geometric tolerance, a surface finish, a material specification, a quantity, a certification, or a functional requirement. Requirements are typically expressed on a 2D drawing, as PMI on a 3D model, or in a separate specification document, and often across more than one of those at once.
What this means for manufacturing software
A requirement only becomes useful to manufacturing software once it is linked to the specific geometric element it applies to. See manufacturing feature and PMI.
Where requirements actually live
On the drawing as dimensions, GD&T callouts and notes; on the 3D model as PMI, where present; and in accompanying documents such as a material certificate requirement or a customer specification.
Common mistakes
Treating geometry as if it were the complete requirement. A part can be geometrically well-defined and still be missing the tolerance, material, finish or quantity information needed to actually manufacture and accept it.
A requirement only becomes useful to manufacturing software once it is linked to the specific geometric element it applies to. See manufacturing feature and PMI.
See how Blake reviews a partFrequently asked questions
Is a part requirement the same as a dimension?
A dimension is one common way to express a requirement; requirements also include tolerances, material, finish, quantity and other non-geometric conditions.
Where do requirements usually come from?
Most often a combination of the 2D drawing, PMI on the 3D model where present, and separate specification or purchasing documents.
Can two part requirements conflict?
Yes; a tight geometric tolerance combined with a specific material or finish requirement can make a part significantly harder, or impossible, to produce as specified, which is part of what a manufacturability check is for.