SolidWorks

SolidWorks is a widely used parametric 3D CAD system. Learn sketch-based features, constraints and design intent, the feature tree, assemblies and mates, drawings, configurations and design tables, equations, and built-in simulation.

Parametric solid modelling changed mechanical design: instead of drawing lines, you build a 3D model from features (extrude, revolve, fillet, hole) driven by dimensions. Change a dimension and the whole model, assembly and drawings update.

SolidWorks is popular in machine design, product development and education because it is approachable yet capable.

An analogy

Like a recipe: each feature is a step. Change an ingredient amount (a dimension) and the dish (model) is re-cooked automatically.

Sketch → feature → part

Pick a plane, sketch a 2D profile, add dimensions and geometric relations (horizontal, coincident, tangent, equal), then create a feature: extrude, revolve, sweep, loft. Add fillets, chamfers, shells, holes (Hole Wizard) and patterns. Fully define sketches so they behave predictably.

Design intent

Dimension from functional references (bearing centres, mounting faces), use symmetry and relations, and order features so edits don't break later features. A good model changes the way the design is expected to change.

Assemblies and drawings

Mates position parts (coincident, concentric, distance, gear, cam) and leave intended motion free. Interference detection and motion studies check the mechanism. Drawings derive views, sections, dimensions, BOMs and balloons directly from the model and stay associative.

Configurations, automation and simulation

Configurations and design tables (Excel) create part families. Top-down design uses layout sketches and in-context features. The API (VBA, C#) automates repetitive work. SolidWorks Simulation (linear FEA, frequency, buckling), Flow Simulation (CFD) and Motion analysis provide early design verification.

Formulas

• Fully defined sketch: remaining DOF = 0 (black geometry)
• Equation example: "D2@Sketch1" = "D1@Sketch1" / 2
• Mass properties: m = ρ · V, I from CAD geometry

Worked example: Mass properties

Given: Block 100 × 50 × 20 mm; Steel ρ = 7.85 g/cm³

Find: Mass.

• V = 100 000 mm³ = 100 cm³
• m = 100 × 7.85 = 785 g

Answer: 785 g (CAD also returns CG and inertia tensor)

Worked example: Driving a family with equations

Given: Width = Length/2, holes = 4 if Length > 80 else 2

Find: Model at Length = 60 mm.

• Width = 30 mm
• Hole count = 2
• Rebuild updates part, drawing and BOM

Answer: 60 × 30 plate with 2 holes

Global variables and equations

"Length"   = 100
"Width"    = "Length" / 2
"Thick"    = 20
"D1@Sketch1" = "Length"
"D2@Sketch1" = "Width"
"D1@Boss-Extrude1" = "Thick"
"D1@HolePattern" = IIF ( "Length" > 80 , 4 , 2 )

Equations capture design intent — width is always half the length, and the hole count switches with size.

VBA macro: change a dimension and rebuild

Dim swApp As Object
Sub main()
    Set swApp = Application.SldWorks
    Dim Part As Object
    Set Part = swApp.ActiveDoc
    Part.Parameter("D1@Sketch1").SystemValue = 0.12   ' metres!
    Part.EditRebuild3
End Sub

The API works in SI units (metres) regardless of document units.

Common mistakes

• Wrong: Leaving sketches under-defined. — Right: Fully define sketches so edits behave predictably.
• Wrong: Referencing unstable geometry (fillet edges) for later features. — Right: Reference planes, sketches and primary faces to avoid rebuild errors.

Applications

• Machine design: Frames, fixtures, special-purpose machines with weldments and sheet metal.
• Consumer products: Enclosures, mechanisms and plastic parts with draft analysis.
• Education & startups: Common first professional CAD tool.

Key takeaways

• Sketch → features → parts → assemblies → drawings.
• Capture design intent with relations and equations.
• Configurations make part families.
• Built-in simulation for early checks.

Going further

• Top-down / skeleton design: Layout sketches drive many parts so the assembly stays consistent.
• PDM: Vault/PDM systems manage versions, approvals and part numbers.
• Model-based definition: 3D PMI annotations replace 2D drawings in some workflows.