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CAD software modules: part, assembly, drafting

Short answer

Part module builds a single parametric solid from sketches and features. Assembly module positions parts with mating constraints, checks interference and creates BOM. Drafting module generates 2D drawings. They are associative through a common database, so changes in any module update the assembly and drawing automatically.

Explain the main modules of a typical 3D CAD software package: part module, assembly module and drafting module. How are the three modules related?

A modern CAD package is organised into modules that work on one common database.

Part module

Used to create a single component. The designer draws a 2D sketch, adds dimensions and constraints, and turns it into a 3D solid with features such as extrude, revolve, sweep, loft, hole, fillet and chamfer. The result is a parametric model: changing a dimension rebuilds the part. Material and mass properties are attached here.

Assembly module

Brings several parts or sub-assemblies together and positions them using mating constraints (coincident, concentric, parallel, distance, angle). It supports interference checking, exploded views, motion study and a bill of materials (BOM). Assemblies can be built bottom-up (existing parts) or top-down (new parts designed in place).

Drafting module

Generates 2D engineering drawings from the 3D model or assembly: orthographic, sectional, auxiliary and detail views, dimensions, tolerances, notes, title block, balloons and BOM table.

Relationship

   PART  ---->  ASSEMBLY  ---->  DRAWING
    ^              |                |
    +-- changes flow both ways ----+

The modules are associative: if a dimension in the part module is changed, the assembly and the drawing update automatically. This avoids inconsistency between the model and the drawings. Other modules (sheet metal, surfacing, simulation, CAM) use the same model.

✓ Answer checked by Claude Opus 5.5 (high effort)

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