Geometry & modeling
Assembly
Definition
An assembly is a CAD model made of multiple parts or subassemblies positioned relative to each other with mates or joints. Assemblies are where fit, clearance, interference, and motion get checked.
Also known as: CAD assembly, assembly model
Updated
Mates and subassemblies#
Parts in an assembly are placed with relationships rather than fixed coordinates. Onshape's Assemblies documentation describes inserting instances and defining mates, with subassembly mates respected by the top-level assembly by default. SolidWorks uses the same word, while Fusion calls these relationships joints.
Assemblies are one of the weakest areas for current text-to-CAD tools. Generating one part is hard enough; generating several parts that fit together, with correct clearances and motion, is much harder.
Sources
Related terms
Parametric modeling
Parametric modeling builds a CAD model from dimensions, constraints, and an ordered list of features, so changing a value regenerates the geometry. It is the default approach in SolidWorks, Fusion, Onshape, Creo, NX, and FreeCAD Part Design.
STEP
STEP is the ISO 10303 family of standards for exchanging 3D product data between CAD systems, usually saved as .step or .stp files. A STEP file carries exact B-Rep solid geometry that another CAD program can measure and edit, but it normally does not carry the original feature history.
Drawing
An engineering drawing is a 2D document generated from a 3D model, with views, dimensions, tolerances, and notes. Many shops still quote and inspect from drawings even when they also receive a STEP file.