GlossaryKind of term: Manufacturing termCAD
What is CAD?
CAD is software for designing parts as 3D models and technical drawings; a subcontractor usually receives the model as a STEP file.
CAD stands for computer-aided design. The package records geometry as 3D models of parts and assemblies, and the 2D drawings are derived from them. In the shop the model itself is often just called the CAD. A subcontractor usually receives the model in a neutral format such as STEP, with a PDF drawing alongside, because the native file is tied to the customer's CAD package.
What does a CAD model hold, and what not?
A model describes the nominal shape: faces, edges and dimensions without deviation. Tolerances, roughness, material and finishing usually sit on the drawing. A model can also carry PMI (product and manufacturing information): dimensional and geometric tolerances and datums in the model itself. A STEP AP242 file can carry that information, as machine-readable semantics or as presentation only, but often it is missing. Some designers model a toleranced dimension at the middle of its tolerance rather than at nominal. A dimension taken from the model can only be trusted once you know which convention was used.
How does CAD work in practice?
The model gives the outer dimensions. With a machining allowance and an available stock size these give the blank; the model also shows the faces to be machined and gives a first view of access. What drives the cost more often sits on the drawing: a fit, a geometric tolerance, a finish. If model and drawing belong to different revisions, the shape you price may not match the requirements that apply. Which source governs where they differ belongs in the agreement with the customer: usually the drawing for a drawing-based order, the model with its PMI under model-based definition (MBD).
What is CAD often confused with?
A CAD model is not the drawing: the drawing is derived from the model with the requirements added, or is a standalone 2D document. Nor is CAD the same as CAM: CAD records what is to be made, CAM how the tool moves to make it.
How do models and drawings from CAD get into Blake?
In Blake you upload STEP and PDF per request, several parts at a time. Model and drawing are brought together per part by file name; where the match is in doubt, it stays open for you to confirm. Drawing values are shown as proposals; you confirm or correct them, and who did so and when stays visible. More on requests.
Frequently asked questions
Can I estimate from a STEP file alone?
You can derive the stock and a first view of the setups, but tolerances, roughness, material and finishing are usually missing. Without a drawing those requirements stay open; ask for them or note them as a reservation in the quote.
Model and drawing disagree. Which one governs?
That is for you and the customer to agree. For a drawing-based order it is usually the drawing; under model-based definition, the model. If it is not settled, ask, and name the revision of both in the quote.
Why do I get a STEP file and not the native CAD file?
The native file is tied to the CAD package and often to its version. STEP is a neutral ISO format that most CAD and CAM packages import; it carries the geometry, but the design history and parameters are usually lost.