FreeCAD Validate Sketch Tool Explained
The Validate Sketch tool in FreeCAD is a built-in diagnostic and repair utility designed to identify, highlight, and resolve geometric and topological errors within 2D sketches. Primarily used in the Sketcher workbench, it checks for common issues such as open profiles, disconnected vertices, overlapping segments, and invalid constraints, ensuring that a sketch forms a clean, closed wire capable of successfully generating solid 3D operations like pads, pockets, and revolutions.
When performing Part Design operations, FreeCAD requires a profile to be topologically valid—most notably, watertight and non-self-intersecting. Even a microscopic gap between two line endpoints or a duplicate hidden line can cause an extrusion to fail. The Validate Sketch tool automates the process of finding these hidden defects.
The primary functions of the Validate Sketch tool include:
- Finding Missing Coincidences: The tool scans the sketch to locate endpoints that appear connected visually but lack a coincident constraint. It highlights these open vertices and provides a "Fix" function, which automatically snaps and constrains vertices that fall within a user-defined tolerance.
- Detecting Overlapping and Duplicate Geometry: It finds identical or overlapping lines and arcs that can confuse the solver and create invalid solid boundaries. Users can highlight these duplicate entities to delete them directly.
- Finding Invalid Constraints: The tool analyzes the sketch for conflicting or broken constraints that prevent the solver from converging to a valid solution.
- Highlighting Open Vertices: For sketches intended to be closed boundaries, the tool flags any vertex that connects to only one edge, visually demonstrating where a loop is broken.
- Reversing Sketch Orientation: In cases where surface normal orientation causes errors in downstream operations, the tool provides options to standardize the curve directions.
To access the tool, open the target sketch in edit mode, navigate to the Sketch menu in the top toolbar, and select Validate sketch. This opens a dialog box containing various diagnostic tabs, allowing you to run checks sequentially, adjust detection tolerances, and apply automated fixes to restore sketch integrity.