If you are a designer, architect, or engineer, few things are more frustrating than AutoCAD crashing in the middle of a critical deadline. One of the most persistent and cryptic error messages users encounter is the "AutoCAD Fatal Error acismobj20dbx free" message.
This error typically appears during startup, when opening a specific drawing, or while executing a 3D command. The term "free" in the error string usually refers to a memory allocation failure (trying to free a protected memory block), not a financial cost. This article provides a definitive guide to diagnosing and fixing this fatal error for free, without expensive software or hardware upgrades.
If multiple drawings crash or the error appears even in new files:
The error message "Fatal Error: Unhandled Access Violation Reading 0x0000 Exception at... acismobj20dbx.arx" indicates a critical failure within AutoCAD related to the ObjectARX module responsible for Spatial/Mechanical 3D modeling. autocad fatal error acismobj20dbx free
The file acismobj20dbx.arx is a core AutoCAD component (specifically related to the Autodesk Shape Manager and 3D Solid modeling). When this module fails, it typically means the software encountered corrupted 3D geometry, a conflict with a third-party plugin, or a damaged installation file.
The "AutoCAD fatal error acismobj20dbx free" message is alarming but almost always fixable without expensive tools. By repairing the ACIS module, disabling hardware acceleration, recovering corrupt DWG files, or resetting AutoCAD, you can return to productive work within minutes. Remember: "free" in this error refers to memory deallocation, not cost—all the professional fixes above are truly free.
If you found this guide helpful, share it with your CAD community. Have another fatal error string? Check our related articles on acdb20.dll crashes and heidi module failures. How to Fix the "AutoCAD Fatal Error acismobj20dbx
Keywords used: AutoCAD fatal error acismobj20dbx free, fix acismobj20dbx, AutoCAD fatal error free solution, ACIS modeling crash.
This error typically occurs when opening a drawing, saving, or using 3D solid modeling commands. The file acismobj20.dbx is an AutoCAD module responsible for ACIS solid modeling (handling 3D objects like spheres, cylinders, extrusions, and booleans).
The error means:
.dwg file has a damaged ACIS solid entity..dbx file is conflicting.Critical: This error is often file‑specific. If only one drawing crashes, the problem is inside that file.
Error Message Example:
Fatal Error: Unhandled Access Violation Reading 0x0000 Exception at 12345678h
often referencing acismobj20.dbx or acdb20.dll
Affected Versions:
AutoCAD 2013–2020 (especially 2015–2018), AutoCAD LT, Civil 3D, Mechanical Control Panel → Programs → right-click AutoCAD →
Common Triggers:
.sat, .3ds, .dwg with complex 3D geometry)