GlossaryKind of term: Manufacturing termTechnical drawing
What is a technical drawing?
A technical drawing records a part's dimensions, tolerances, material and other requirements in 2D; with a request it usually arrives as a PDF.
It can describe a part or an assembly and consists of views and sections, dimensions with tolerances, geometrical tolerances, roughness, threads, edges, material and finish, and a title block with part number, revision and general tolerance. Besides a PDF exported from CAD, you also meet scans of paper drawings. It describes what the part has to be, usually not how to make it; where the drawing prescribes a process, such as a heat treatment or grinding, that is a requirement too.
What does the standard say about the technical drawing?
The drawing language is set in ISO standards for technical product documentation and geometrical product specification (GPS), among them ISO 128 for presentation, ISO 129-1 for dimensioning, ISO 1101 for geometrical tolerancing (form, orientation, location and run-out) and ISO 7200 for the title block. A drawing is only unambiguous with the references it carries: the general tolerance (for example ISO 2768-mK), the projection method, and whether the independency principle of ISO 8015 or the envelope requirement applies. Drawings to ASME Y14.5 follow partly different rules; there, for example, the envelope principle applies by default (Rule #1). Where a reference is missing, the intent is uncertain and you ask.
How does the technical drawing work in practice?
The drawing sets the estimate lines that do not follow from shape: a tight tolerance that can call for an extra operation, setup or inspection, a roughness that can call for a finishing pass or a further process, a finish that is often subcontracted, the material that sets price and cutting data. Notes and references to customer specifications weigh as much as dimensions. A poor scan can make digits ambiguous; you query an uncertain value rather than guess it. Which document leads when drawing and model differ follows from the agreement with the customer; in drawing-based work that is usually the drawing, in model-based definition (MBD) the model.
What is the technical drawing often confused with?
The STEP model gives the nominal shape; the drawing states the requirements that go with it. A drawing requirement is something else again: one specification on the drawing, such as a flatness of 0.05 mm, and a drawing often carries dozens.
How do you see the technical drawing in Blake?
In Blake you upload the drawing as a PDF alongside the model; here too, pairing per part stays open where there is doubt until you choose. Material, tolerances, roughness, finish and threads from the drawing are set out as proposals. You confirm or correct each value; who did so and when stays visible, with a note if you add one. More on requests.
Frequently asked questions
What if the drawing and the model disagree?
Then the document named as leading in the order or on the drawing applies. If nothing names one, or the shape itself differs, ask which file applies before you price, and record the answer.
What do I do with a poor scan?
Ask for a legible copy or have unclear values confirmed. If that cannot happen before the quote, price on an assumption and name it in the quote, so the customer sees what your price rests on.
Which standard references should I check on a drawing?
At least the general tolerance, the projection method and the tolerancing principle: independency per ISO 8015 or the envelope requirement. If the drawing refers to a customer specification, ask for it; without that document the requirement is not unambiguous.