FreeCAD TechDraw Balloon Tool Explained

This article explores the core functions, features, and practical applications of the Balloon Annotation tool in the FreeCAD TechDraw workbench. Readers will learn how this drafting feature enables clear part identification, links components to a Bill of Materials (BOM), and conforms technical drawings to standard engineering documentation practices.

The primary function of the Balloon Annotation tool in FreeCAD TechDraw is to create numbered or labeled callouts that identify specific parts, assemblies, or features within an engineering drawing. Similar to standard drafting callouts in mechanical design, balloons typically consist of a circular boundary enclosing an index number or string, connected to the target component via a leader line and an arrowhead or dot.

Bill of Materials (BOM) Integration

In assembly drawings, balloons serve as the primary visual link between 2D projected views and a Bill of Materials or parts list. Each balloon displays an index number corresponding directly to an entry in the BOM, allowing manufacturers, assemblers, and inspectors to identify individual components and their associated metadata—such as part names, quantities, and material specifications—without cluttering the drawing with lengthy text annotations.

Key Customization and Properties

The TechDraw Balloon tool provides several configurable properties within FreeCAD's Data tab:

• Text and Value: By default, balloons display numeric values that can auto-increment as consecutive balloons are placed, or they can be manually overridden with custom alphanumeric text.
• Shape Geometry: Users can alter the enclosing shape from the standard circle to alternatives such as rectangles, triangles, hexagons, or no enclosing shape at all for plain leader text.
• Leader Line and Endpoints: The leader line automatically adjusts as the balloon is moved around the sheet. The termination point can be customized with various symbols, such as solid arrows, open arrows, or dots, depending on whether it points to an edge or a surface face.
• Attachment Modes: Balloons can be anchored directly to 2D geometry (vertices or edges) within a TechDraw view, ensuring that if the view is moved or scaled on the sheet, the balloon shifts dynamically alongside the referenced geometry.

Drawing Workflow

To use the tool, a drafter selects a vertex or edge in a TechDraw projection view and clicks the Balloon button on the TechDraw toolbar. Once placed, dragging the balloon repositions the label while maintaining the leader line's connection to the selected feature. Customizations to balloon size, font, line weight, and displayed index are managed directly through the Property panel, making it a flexible instrument for generating industry-standard technical documentation.