Engineering Drawings: Standards, Views and Production Documentation: Key Terms

Comparison Table: View Types

Process: Creating a Complete Engineering Drawing

flowchart TD
    A[Create Drawing File] --> B[Select Drawing Template]
    B --> C[Insert Model View as Base]
    C --> D[Add Projected Views]
    D --> E{Internal Features Needed?}
    E -- Yes --> F[Create Section Views]
    E -- No --> G{Small Details Need Clarity?}
    F --> G
    G -- Yes --> H[Create Detail Views]
    G -- No --> I[Add Dimensions]
    H --> I
    I --> J{Assembly Drawing?}
    J -- Yes --> K[Insert Bill of Materials]
    K --> L[Add Balloons to Link Components]
    J -- No --> M[Review and Finalize]
    L --> M

Key Terms

• Drawing View – any 2D representation of a 3D model placed on a drawing sheet
• Model View – the primary base view derived directly from the 3D model
• Projected View – an orthogonal view derived from and aligned with an existing model view
• Section View – a view showing internal features by cutting through a parent view along a defined line
• Detail View – a magnified view of a specific area of a parent view
• Driving Dimension – a dimension that controls model geometry; changes propagate to the 3D model
• Driven Dimension – a reference-only dimension added to the drawing; does not affect model geometry
• Bill of Materials (BOM) – a table listing all assembly components with item numbers, part numbers, descriptions, and quantities
• Balloon – a numbered callout with a leader line connecting a component in an assembly view to its BOM entry
• Crosshatching – a pattern applied to cut surfaces in section views to indicate solid material
• Drawing Template – a pre-configured file defining sheet size, border, and title block
• Leader Line – a line connecting an annotation (such as a balloon) to the feature it references

Quick Revision

• Drawings are directly linked to their source 3D models — changes propagate both ways
• Model Views are the base 2D representations; Projected Views are derived from them and stay aligned
• Section Views cut through parent views to expose hidden internal geometry with crosshatching
• Detail Views magnify small or complex areas for clearer dimensioning
• Driving Dimensions control the 3D model; Driven Dimensions are reference-only annotations
• The Bill of Materials (BOM) lists all assembly components with quantities and part details
• Balloons link visible assembly components to their BOM item numbers via leader lines
• Auto-Balloons and quantity indicators reduce clutter in complex assembly drawings
• Dimensions can be imported from the model or added manually — imported ones require cleanup for clarity
• The full drawing creation workflow proceeds from template selection through views, dimensions, BOM, and balloons

Overview

• In parametric CAD systems, 2D drawings are generated directly from 3D model data rather than being drafted manually line by line.
• A bidirectional associative link exists between the 3D model and the 2D drawing — changes in either environment automatically propagate to the other.
• The primary purpose of 2D drawings is to document 3D designs for manufacturing and production.

Key Concepts

• Associativity – The continuous, live data link between the 3D model and its 2D drawing; edits in one are instantly reflected in the other.
• Drawing Sheet – The active workspace where model views, dimensions, and annotations are placed.
• Sheet Format – The background layer containing the title block, page borders, and standard document properties.
• Parametric Modeling – A design methodology where geometry is controlled by mathematical rules, parameters, and dimensions.

Drawing Layout and Structure

• A drawing document must be properly structured using standard templates before any views are placed.
• Two distinct editing modes exist within a drawing file:
  • Edit Sheet Mode
    • The primary working mode.
    • Used to insert model views, dimensions, and annotations.
  • Edit Sheet Format Mode
    • A specialised mode for modifying background elements only.
    • Used to edit the title block text, logos, or border lines.
    • While active, standard drawing views temporarily disappear to prevent accidental modifications.

Types of Drawing Views

• Drawing views act as windows into the 3D model, projected onto a 2D plane.

• Model View (Base View)

  • The first orthographic projection inserted into the drawing (e.g., Front, Top, Right, Isometric).
  • Imported directly from the 3D model.
  • Serves as the parent view from which other views are derived.

• Projected View

  • Created by projecting linearly from a parent Model View.
  • Produces additional orthographic views (e.g., projecting a Top view from a Front view).

• Section View

  • Exposes hidden internal geometry by slicing through a part.
  • Created by drawing a cutting line across an existing parent view.
  • The resulting view automatically applies cross-hatching to indicate cut solid material.

• Detail View

  • Used to clarify intricate or tightly packed features that are hard to read at standard scale.
  • Generated by sketching a boundary (typically a circle) around the target area on a parent view.
  • Produces a separate, magnified view of that region.

Annotating and Dimensioning

• Dimensions define the precise size and location of features for manufacturing.

• Model Items (Imported Dimensions)

  • Dimensions used to build the 3D model can be automatically imported into the 2D drawing.
  • Eliminates the need to recreate dimensions from scratch.

• Manual Dimensioning

  • Users can place additional dimensions directly on the 2D drawing.
  • These serve as manufacturing reference points or for checking distances.

Assembly Documentation

• When documenting assemblies (multiple parts fitted together), specific tools identify individual components.

• Bill of Materials (BOM)

  • A structured table inserted into the drawing listing all components in the assembly.
  • Automatically extracts data such as item numbers, part names, descriptions, and quantities.
  • Three common BOM types:
    • Top-level only – Lists only major sub-assemblies and standalone parts.
    • Parts only – Ignores sub-assembly groupings; lists every individual piece as a flat list.
    • Indented – Shows the full hierarchical structure of assemblies, sub-assemblies, and their sub-components.

• Balloons

  • Circular, numbered annotations attached to parts within drawing views.
  • Parametrically linked to the BOM — the number inside each balloon matches the component's item number in the BOM table.
  • Provide a visual connection between a part in the drawing and its entry in the BOM.

Dimension Types Comparison

Drawing View Types Summary

BOM Types Comparison

Diagram / Process

Standard Drawing Creation Workflow

flowchart TD
    A[Finish 3D Model or Assembly] --> B[Open New Drawing File]
    B --> C[Select Sheet Size and Format]
    C --> D[Insert Base Model View]
    D --> E[Derive Additional Views]
    E -.-> E1[Projected Views]
    E -.-> E2[Section Views]
    E -.-> E3[Detail Views]
    E --> F[Import Driving Dimensions]
    F --> G[Add Annotations and Reference Dimensions]
    G --> H[Final Manufacturing Drawing]

Assembly Documentation Workflow

flowchart LR
    A[Insert Assembly View] --> B[Generate Bill of Materials]
    B --> C[Set BOM Type]
    C --> D[Attach Balloons to Parts]
    D --> E[Verify Item Numbers Match BOM]

D-to-2D Associativity Concept

flowchart LR
    A[3D Model] <-->|Bidirectional Parametric Link| B[2D Drawing]
    B --> C[Dimensions Update Automatically]
    B --> D[Views Regenerate on Change]
    A --> E[Design Intent Preserved]

Key Terms

• Orthographic Projection – A method of representing three-dimensional objects in two dimensions by projecting views from perpendicular angles.
• Cross-hatching – A pattern of angled lines used in Section Views to indicate solid material that has been cut through.
• Parametric Modeling – A design approach where geometry is driven by mathematical rules, parameters, and dimensions, enabling automatic updates.
• Title Block – The standardised information table (typically in the bottom-right corner) containing metadata such as author, scale, date, and part numbers.
• Associativity – The live, bidirectional data link ensuring 3D model changes are reflected in 2D drawings and vice versa.
• Bill of Materials (BOM) – An auto-generated table listing all components, quantities, and descriptions for an assembly.
• Balloons – Numbered annotation markers in a drawing view that link each part to its corresponding BOM entry.
• Driving Dimensions – Dimensions imported from the 3D model that control its physical geometry.
• Driven Dimensions – Read-only reference dimensions placed manually in the 2D drawing with no effect on the 3D model.

Quick Revision

• 2D drawings are parametrically linked to 3D models — updating one automatically updates the other.
• The Sheet holds views and dimensions; the Sheet Format holds the title block and borders.
• Model Views (Base Views) are the foundational views imported directly from 3D data.
• Projected Views are derived linearly from a parent view for additional orientations.
• Section Views slice through a part to reveal internal geometry; Detail Views magnify small features.
• Driving Dimensions control the actual 3D model; Driven Dimensions are read-only references for manufacturing.
• A Bill of Materials (BOM) automatically tables all parts, quantities, and descriptions in an assembly.
• BOM types include top-level only, parts only, and indented (hierarchical).
• Balloons visually connect parts in a drawing view to their corresponding BOM row via matching item numbers.
• Two editing modes exist: Edit Sheet (for views and dimensions) and Edit Sheet Format (for title block and borders).