Under-defined vs fully-defined vs over-defined in Solidworks - Compared

Introduction

This feature helps you understand how sketches in SolidWorks are constrained. It shows if a sketch has too few, just enough, or too many constraints. This helps you create stable and accurate designs.

When you start drawing a new sketch and want to check if it is stable.

When your sketch moves unexpectedly and you want to find missing constraints.

When you add constraints and want to avoid conflicts that cause errors.

When preparing a sketch for 3D features like extrude or revolve.

When reviewing a design to ensure all parts are properly defined.

Steps

Step 1: Open

- SolidWorks and create or open a sketch

The sketch appears in the graphics area ready for editing

Step 2: Look at the status bar at the bottom of the SolidWorks window

- Status bar

You see a message indicating if the sketch is under-defined, fully-defined, or over-defined

Step 3: Select the sketch entities

- Graphics area

Sketch entities highlight with colors showing their constraint status: blue for under-defined, black for fully-defined, red for over-defined

Step 4: Add or remove constraints

- Sketch tab > Add Relations or Delete Relations

Sketch updates and status bar message changes accordingly

Step 5: Use the 'Display/Delete Relations' tool

- Sketch tab > Display/Delete Relations

A list of all constraints appears, helping you identify conflicts or missing constraints

Before vs After

Before

Sketch entities are blue and status bar shows 'Under-defined'. The sketch moves when dragged.

After

Sketch entities turn black and status bar shows 'Fully-defined'. The sketch stays fixed when dragged.

Settings Reference

Sketch Status Display

📍 Status bar at the bottom of the SolidWorks window

Shows the current constraint state of the sketch

Default: Under-defined when sketch is first created

Entity Color Coding

📍 Sketch tab > Options > System Options > Colors

Visually indicates the constraint status of sketch entities

Default: Blue for under-defined, Black for fully-defined, Red for over-defined

Display/Delete Relations

📍 Sketch tab

Helps manage and troubleshoot sketch constraints

Default: Show all constraints

Common Mistakes

Ignoring the status bar message and continuing to add features.

An under-defined sketch can cause unexpected changes in the model later.

Always check and fix sketch constraints until it is fully-defined before proceeding.

Adding too many constraints causing the sketch to become over-defined.

Over-defined sketches cause errors and prevent proper editing.

Use the Display/Delete Relations tool to find and remove conflicting constraints.

Summary

Sketches can be under-defined, fully-defined, or over-defined based on constraints.

Fully-defined sketches are stable and best for building features.

Use color codes and status bar messages to monitor sketch constraint status.