What is ʼExternal Relationʼ in a sketch in SolidWorks?

Short Answer

An External Relation in a solidworks sketch is a sketch relation that links sketch entities to model geometry outside the active sketch, such as edges, faces, vertices, or axes. The most common professional method is creating it with Convert Entities or while sketching on a referenced face. Limitation: external references can break if the parent geometry changes.

What You Need to Know Before

Warning: External Relations can make a sketch update unpredictably when referenced model edges, faces, or features are edited, suppressed, or deleted. A very common failure is a dangling external reference after feature order changes or imported geometry updates.

How to Create or Use an External Relation

• Command: Convert Entities

• Shortcut: No default keyboard shortcut

• Quick Steps:

  1. Edit the sketch, then select a model edge, loop, or face from the graphics area or FeatureManager.
  2. On the Sketch tab in the CommandManager, click Convert Entities.
  3. In the PropertyManager, confirm selections and, if needed, enable the Select chain option to convert connected edges quickly, then click OK.

Variables & Settings

• Key Setting: Select chain

• Expert Setting: This option automatically includes tangent or connected edges during Convert Entities, which speeds up profile creation but can also pull in unwanted segments if the model edge chain is complex.

Why it Fails

• Cause 1 (Geometry): The referenced edge or face was deleted, replaced, or topologically changed, so the sketch relation becomes dangling.
• Cause 2 (layers/Locks): The model component may be fixed, suppressed, lightweight, or not fully resolved in an assembly, preventing stable external references.
• Cause 3 (Command/Logic): The sketch is overdefined or the external reference conflicts with existing dimensions and relations, so SolidWorks cannot solve it cleanly.

Quick Fix & Best Practice

• Quick Fix: Edit the sketch, display dangling relations, then delete or reattach the broken reference using Display/Delete Relations or recreate it with Convert Entities.
• Manager’s Verdict: Use External Relations for fast associativity to stable design geometry, but avoid heavy dependence on changing edges in late-stage models or imported parts.

FAQ

Can I delete an External Relation without deleting the sketch?

Yes, use Display/Delete Relations and remove only the external relation.

Are External Relations the same as sketch relations like Horizontal or Coincident?

No, they specifically reference geometry outside the active sketch.

How do I find broken External Relations in SolidWorks?

Edit the sketch and check Display/Delete Relations for dangling or external references.

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