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Chapter 1 · 3 hours

Introduction

Practice questions

Practice questions and answers

2 exam-style questions on this chapter, written for this site from the official syllabus. We haven’t found past IOE papers for this subject yet; if you have some, share them in the community.

  • Practice · 6 marks

Define computer aided design (CAD), computer aided manufacturing (CAM) and computer aided engineering (CAE). Briefly describe the development of CAD/CAM from the 1950s to the present.

Answer

CAD is the use of computer systems to create, modify, analyse and document an engineering design. CAM is the use of computers to plan, control and manage manufacturing operations, directly or indirectly (for example NC part programs, process planning, inspection). CAE is the use of computer software to analyse and simulate a design before it is built (stress, heat transfer, vibration, flow, motion) and to optimise it.

Comparison

TermMain taskTypical tools / output
CADGeometry creation, draftingPart models, drawings, BOM
CAEAnalysis, simulation, optimisationFEA, CFD, multibody dynamics
CAMManufacturing planning and controlTool paths, NC/G-code, process sheets

Development of CAD/CAM

  • 1950s: Numerically controlled (NC) machine tools at MIT; first graphics displays (SAGE air-defence system); APT language for part programming.
  • 1960s: Sutherland's Sketchpad (1963) introduced interactive graphics. General Motors (DAC-1), Lockheed and Boeing started industrial CAD.
  • 1970s: Turn-key 2D/3D wireframe systems on minicomputers; surface modelling; solid modelling research (CSG, B-rep); CNC and DNC spread.
  • 1980s: Workstations and PCs, AutoCAD (1982); solid modellers, finite element pre/post-processors, standards such as IGES.
  • 1990s: Parametric, feature-based modellers (Pro/ENGINEER, SolidWorks), STEP standard, CAD-CAM integration.
  • 2000s onwards: Associative assemblies, product data management (PDM/PLM), cloud CAD, topology optimisation, additive manufacturing and digital twins.

Today CAD, CAE and CAM work on one shared product model, which shortens the design-to-manufacture cycle.

  • Practice · 5 marks

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

Answer

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.

Written from the official syllabus. Questions and answers are written for this site; check them against your class notes.

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