Autocad Error 18003 ((top)) May 2026

AutoCAD Error 18003 is a modeling operation error that typically occurs during Boolean operations (like Union, Subtract, or Intersect) between 3D solids. It signals a failure in the underlying geometric engine to calculate the new volume, often due to mathematical complexities or "dirty" geometry. Understanding Error 18003: A Modeling Obstacle

• Reproduce and note exact message: Record the full error text and when it occurs (startup, when opening a file, after an update).
• Check Event Viewer and AutoCAD logs: Windows Event Viewer (Application logs) and AutoCAD’s own activity logs may contain more specific error stacks or DLL names.
• Verify license type: Confirm whether the install uses single-user activation, multi-user/network licensing, or a subscription tied to an Autodesk account.
• Test with another user/profile or machine: Try launching AutoCAD as an administrator or from a different Windows user account to determine whether the issue is profile-scoped.
• Disable antivirus/firewall temporarily: Briefly disable security software to rule out file-blocking; if this fixes the error, add AutoCAD folders and executables to exclusions.
• Check network licensing: For network licenses, confirm the license server is reachable (ping, telnet to license port), and that the client’s FLEXnet client matches the server’s recommendations.
• Inspect file permissions and disk health: Run chkdsk if disk errors are suspected, and verify ProgramData\Autodesk and user AppData\Roaming\Autodesk permissions allow read/write for the user.

⚠️ Common Causes

1. Incorrect system date/time – The license timestamp validation fails.
2. Blocked license ports – Firewall/antivirus blocks Autodesk licensing communication (port 2080, 27000‑27009).
3. Corrupted licensing files – Files in C:\ProgramData\FLEXnet or C:\Users\<user>\AppData\Roaming\Autodesk\ADUT become damaged.
4. Outdated License Manager – For network licenses, the LMTOOLS version may be old.
5. Windows updates or security patches – Some updates interfere with Autodesk licensing components.

1. Close AutoCAD.
2. Delete the SSO cache folder:

   Select the "suspect" solid that is causing the error. AutoCAD will attempt to automatically repair its geometry. autocad error 18003