It Starts With Parts PART 2 PART 1 PART N Product is made up of parts You create parts, then do things with them Fundamental info is stored as part geometry and info, everything else is derived from this Change the part, the dwg and assemblies automatically update Parts are 3-D! A car: 10,000 parts ASSEMBLIES DRAWINGS ANALYSIS

Parts have features SLOT or CUT CHAMFER PROTRUSION Rounds, chamfers, holes, threads, cuts, ….

Build up part by creating base, then adding features Base parts are usually slabs, cylinders, cones or simple variants. Build features on top of base parts

Assemblies are collections of parts

Drawings are generated from parts We’ll get into dimensioning later. Dimensions (size) is specified **at part creation time**, not at drawing time. Can change whenever. Can link dimensions so that if you change the side of a hole, you automatically change the size of a pin.

Machining Assembly 2-D drawing Costing/Purchasing Engineering analysis 1400 lbs 3-D solid model is the heart of the part database Everything flows from the database Internally, stored in proprietary format, visual (shaded, wire-frame) is just for humans 2-way Associativity: changing dimension on assembly or on drawing will change dimension on 3-d part. Thus, everything stays up to date. A key feature when handling assemblies with thousands of parts (e.g. auto, plane, ship…) Costing/Purchasing Engineering analysis

CAD determines design intent This? …or this? CAD package vs general drawing package. CAD tries to determine your intent. When you enlarge a part, will guess that you don’t mean to enlarge the hole

Constraint-based modeling 6.00 2.00 This? 4.00 6.00 3.00 Constraint-based modeling You can either constrain hole to be: (1) always 2 inches from the edge, or (2) always in the center Constraint remains no matter how you change dimensions of the part For assemblies, constrain parts to each other, e.g. faces match or left sides align. Parametric modeling: The dimension drives the geometry. You can change the dimension and the geometry changes. …or this?

Relations to fix intent D1 D2 D2 = SQRT(D1) 1 4 2 Relations Dimensions are related (by any mathematical function), so that a change in one dimension affects other dimensions in such a way that preserves design intent. Equations can be of arbitrary complexity and and relate an arbitrary number of dimensions. Goal: Set up constraints and relations so that you only have to change one thing, and intent is maintained.