A type of PCD used when the procuring authority wishes to stipulate certain design features without themselves completing the design. An ED is usually created as the first in a chain of drawings when some or all of the design Engineering effort is to be procured.
An ED can be either in book-form or sheet-form. When published in book form, an ED looks a lot like a specification, but there are critical distinctions between the two. One is that a specification is can be written by a supplier for authentication by the procuring agent’s customer, while an ED is released on the authority of the agent alone1.
Another critical distinction is that the ED can (and should) be used to communicate design intent to the degree that it is known at the time procurement starts. Since some design features are “required” by superior documentation (specifications), while other features originate with the procuring authority, the skills required for a true ED are not the same as those required for a specification2.
When the design is complete, an ED can be canceled in favor of a supplier’s part number (and design disclosure package), evolve into a VICD, or evolve into an SCD.
Footnotes- The recent weakening of the authentication concept has contributed to the weakening of the distinction between ED’s and specifications.[↩]
- Specification writers are typically trained to NEVER originate technical content, in order to minimize the contractual obligations to the customer. It must be recalled that specifications are often written by the supplier on the behalf of the customer, which notion has some conflict of interest built into it.[↩]