The FATAL ERROR involving acismobj20.dbx primarily affects older AutoCAD versions (2014-2016) when running on modern Windows systems. Effective solutions include resetting AutoCAD to default settings, repairing the installation, or running the 32-bit version on 64-bit systems. For a detailed troubleshooting guide, visit the Autodesk Support Site AutoCAD LT 2015 on Windows 11 – FATAL ERROR

3. Disable Hardware Acceleration Temporarily

To isolate the issue:

The Best Steps:

Install Latest Service Packs: Autodesk regularly releases hotfixes for DBX library errors. Ensure you have the latest updates from the Autodesk Account portal or the Autodesk Access app.

5. Preventing Future Occurrences

| Prevention | Action | |------------|--------| | Save ACIS data cleanly | Before closing, run AUDIT and -PURGE (Regapps). | | Avoid copy/paste of 3D solids between different AutoCAD versions. Use WBLOCK instead. | | Update graphics drivers monthly (certified from Autodesk’s list). | | Disable real-time antivirus scanning of .dwg and .tmp files. | | Convert complex 3D solids to 3D mesh (MESHSMOOTH) if ACIS operations are not needed. |

5. Check for Non-English Characters or Deep Folder Paths

ACIS kernel has legacy limitations. Ensure:

1. Start a new blank drawing.
2. INSERT → Browse to corrupt file → check Explode → OK.
3. Run PURGE → Regapps (several times).
4. Run -EXPORTTOAUTOCAD (version 2013 or earlier).

Warning: Close AutoCAD completely. Run Command Prompt as Administrator.