The specification is the document that formalises a need and the conditions under which it must be met. In manufacturing, it complements the definition drawing: the drawing says what the part is, the specification says everything else, that is, what it is for, in what environment it works, in what quantity, with what requirements and to what schedule. A functional specification is one that expresses the need as functions to be fulfilled rather than as an imposed technical solution.
A manufacturing specification generally contains the context and function of the part, the technical documents (drawing, 3D model in STEP format), the material, the quantities and their rhythm, the tolerances and surface finishes, the treatments, the inspections and quality documents required, packaging, place and date of delivery, confidentiality and selection criteria. It must be clear, prioritised (what is mandatory, desirable or open) and dated, with a version index.
It serves three purposes. It lets several workshops quote on the same scope, and so lets you compare their offers. It avoids misunderstandings that are paid for in rework or delays. It is one of the reference documents in a dispute, hence the value of fixing their order of priority. A structured template is better than free text: the guide on the manufacturing specification offers one, and the specification generator helps you fill it in step by step.
In a quote request
Attach it to your request, or reuse its headings in your project request. Mark what is mandatory and what is negotiable, give quantities as price breaks, and say whether the material or technical solution can be proposed by the workshop (“or equivalent”). The specification feeds the quote request, which the buyer sends to workshops; for a project that will move from one-offs to series, see the guide from prototype to series.