An engineering document (which can be in digital form) that discloses, whether directly or by reference, the physical and/or functional requirements for an item. In this business, the term “drawing” is synonymous with “Engineering Drawing” as defined by ASME Y14.24.
The alert reader will note that the definition above, which is adapted from the referenced ASME standard, could just as easily be applied to a Development Specification. Here’s what they don’t tell you in either “school”:
- The ASME uses the term “item” to mean “stockable item”. “Stockable” literally means that a supplier can build the parts speculatively, even though no specific customer has requested it yet. This is also the sense in which the ASME media uses “identified part”, meaning that it can be assigned a part number and serial/lot number, where the part number explicitly asserts interchangeability within the intent of the original design. Such an “item” may, or may not, be a Configuration Item in the sense of System Engineering.
- Requirements (whether physical or functional) on a production “drawing” specifically speak to the manufacture of the part. Not all drawings are, however, production drawings1i, which actually leaves the ASME definition deficient (and a bit internally inconsistent).
- A production drawing (to be properly narrow in usage) communicates the requirements for manufacture of a design, whereas a development specification communicates the requirements for the design itself. The development specification is a more abstract concept than that of the drawing…except…certain types of control drawings communicate requirements for development in the same sense as does a Development Specification:
- Envelope Drawings contain a subset of features, with the remainder left to the ingenuity of the detailed design authority
- Source Control Drawings contain requirements for the verification of compliance to requirements for an existing design, where those data are not already the intellectual property of the original design authority for the part.
- The difference between these two drawing types (on the one hand) and a Development Specification (on the other hand) is one of origin:
- Development specifications contractually controlled outside the developer by the Acquisition Customer. If there is no Acquisition Customer (i.e., commercial development) then there is no need for a true specification.
- The drawings originate inside the developer, representing “design intent”, which may be different from or more specific than the intent of the Acquisition Customer (if there is one).
- See, for example section 1.10 “Ancillary Drawings”, and think through the implications of “…do not establish item identification”, which means that the information on an Ancillary Drawing cannot be “required” in order to part mark the item.[↩]