When a conversion doesn't look right

The 3D Armory · Updated October 27, 2026

Start with the exact message and a known dimension. Repeatedly converting the same damaged input with different extensions rarely fixes its geometry.

“Not a closed, manifold mesh”

STEP output needs a closed shell. An edge on the rim of a hole belongs to only one triangle; overlapping or duplicated faces can make an edge belong to more than two. Use your mesh editor's inspection tools to locate boundary or non-manifold edges, repair the source, and export again. The converter can orient adjacent faces, but it is not a general-purpose mesh repair tool.

“Multiple disconnected shells”

The model contains separate surfaces. They might be independent parts, stray triangles, or an inner cavity. The converter rejects these for STEP output instead of guessing whether a surface is a separate solid or a void. Export one solid at a time. Do not blindly delete inner surfaces: they may be necessary to describe a hollow part. Use the original CAD model when accurate cavities must be preserved.

A model opens 25.4 times too large or too small

This is a useful clue to an inch/millimeter mismatch. A source coordinate of 1 interpreted as an inch becomes 25.4 mm. Verify the source units for STL or OBJ, then verify the receiving application's units. A factor of 10 can indicate centimeters versus millimeters; 1,000 can indicate meters versus millimeters. The 10 mm sample cube helps isolate the workflow from your own model.

A STEP output looks angular or is hard to edit

All exports here pass through a triangle representation. STEP output contains faceted faces, not reconstructed curves or editable features. Selecting a CAD input and a CAD output does not bypass this step. To preserve exact surfaces when converting IGES or BREP to STEP, use a CAD application that transfers boundary representations directly rather than this mesh-based converter.

Colors, textures, or part names disappeared

The converter exports geometry. OBJ material files and texture coordinates, vertex colors, and assembly metadata are not preserved. PLY is an output format here, not an accepted input format. For OBJ input, export explicitly triangulated geometry; the parser splits polygons into triangle fans and does not resolve complex concave faces for you.

“No usable geometry” or the CAD engine cannot read the file

Renaming a file does not change its format. Open it in the application that created it and export a supported geometry file. OBJ must include vertices and faces; point-only and line-only files are not enough. Invalid coordinates and triangles with zero area are rejected. For BREP, confirm units in the source application: the reader preserves source coordinate values and cannot infer a missing unit convention.

Conversion is slow or the engine stops

The work uses your device's memory and processor. The first CAD conversion also needs to load the engine. Keep the tab open, close other memory-heavy tabs, and try a smaller file or Coarse mesh quality. Inputs must be no larger than 25 MB; STL and OBJ meshes must stay within 100,000 triangles. CAD input is limited to 2 million generated triangles. A three-minute timeout prevents a stalled job from running indefinitely.

Use Cancel conversion to stop a running job. If even the sample cube fails, try a current browser with WebAssembly enabled. If the sample succeeds but your part fails, the source geometry or its complexity is a better place to investigate.

Still stuck?

Contact support with the error, input and output formats, browser, and settings. Start with a description rather than a confidential model file.