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Import Errors

This page covers common problems when importing STEP or STL geometry into deFlex.

STEP file fails to parse​

Symptom: After selecting a STEP file, deFlex shows "Parsing STEP..." for a long time, then displays an error message, or the browser becomes unresponsive.

Possible causes​

File is too large​

STEP files are parsed client-side in the browser. Files over 10 MB can cause the browser to slow down or run out of memory.

Fix: Simplify the geometry in your CAD tool before exporting. Remove unnecessary features (chamfers, small fillets, cosmetic details) that do not affect the optimization domain. Export only the relevant face or cross-section, not the entire assembly.

File contains no solid bodies​

The STEP importer expects B-rep (Boundary Representation) solid bodies. If the file contains only wireframe geometry, surface patches, or datum features, the parser cannot extract faces.

Fix: In your CAD tool, ensure you are exporting a solid body (not a surface body or wireframe). Use "Save As > STEP AP214" or "STEP AP203" with the solid body option selected.

Unsupported STEP version​

deFlex supports STEP AP203 and AP214. Other STEP variants (AP242, AP238) may not parse correctly.

Fix: Re-export from your CAD tool using STEP AP203 or AP214 format.

Corrupted file​

The STEP file may have been truncated during download, or the text encoding may be incorrect.

Fix: Re-download or re-export the file. Open it in a text editor and verify it starts with ISO-10303-21; and ends with END-ISO-10303-21;.

Upload fails after parsing​

Symptom: The STEP file parses successfully (faces are detected) but the upload to the server fails with an error.

Possible causes​

Not signed in​

The upload endpoint requires authentication. If your session has expired, the upload will fail.

Fix: Refresh the page and sign in again, then retry the upload.

Server error​

The backend may be temporarily unavailable or overloaded.

Fix: Wait a moment and click Retry Upload. If the error persists, check that you have a stable internet connection and try again later.

Mesh JSON too large​

For very complex STEP files with many faces and edges, the parsed mesh JSON can exceed server upload limits.

Fix: Simplify the geometry to reduce face count. A STEP file for design optimization typically needs only 1--10 faces, not hundreds.

No faces detected​

Symptom: The upload succeeds but deFlex reports "No faces detected" and the face selection button is unavailable.

Cause: The STEP file was parsed but the geometry does not contain recognizable planar or cylindrical faces that the importer can extract as 2D computation domains.

Fix:

  • Verify the STEP file contains a solid body with clear faces (not just edges or vertices).
  • Try a different face in your CAD model -- export a simpler cross-section.
  • If the geometry is freeform (NURBS surfaces), it may not decompose into flat faces suitable for 2D meshing.

No bolt holes detected​

Symptom: The STEP file uploads and faces are available, but no bolt holes are found. You expected automatic bolt pad creation.

Cause: Bolt hole detection looks for circular through-holes in the geometry. If your holes are:

  • Countersunk or counterbored: The complex profile may not be recognized as a simple through-hole.
  • Slotted: Non-circular cutouts are not detected.
  • Blind holes: Only through-holes are detected.
  • Too small or too large: Detection has size thresholds that may exclude extreme hole sizes.

Fix: Add bolt pads manually. See Add Bolt Holes.

Face selection does not work​

Symptom: You click "Select Computation Face" but clicking in the viewport does not select a face.

Causes:

  • Viewport focus: Click directly on the 3D geometry, not on the background. The face selection mode requires clicking on a rendered face of the STEP model.
  • STEP model hidden: The base plate visibility may be toggled off. Click the eye icon in the STEP section to show it.
  • Mesh data not loaded: If the mesh JSON failed to load (network error), face selection data is unavailable. Check for a "Failed to load face data" warning.

Fix:

  • Ensure the STEP model is visible in the viewport.
  • Click directly on a face of the rendered model.
  • If mesh data failed to load, remove the STEP file and re-upload it.

STL import issues​

STL files are supported for certain preserve types (e.g., deformation step). Common issues:

  • ASCII vs. binary: Both formats are supported, but very large ASCII STL files may be slow to parse. Use binary STL for files over 1 MB.
  • Non-manifold geometry: STL files with gaps, self-intersections, or inverted normals may cause parsing errors. Run a mesh repair tool (e.g., Meshmixer, Netfabb) before importing.
  • Coordinate units: STL files do not carry unit information. deFlex assumes millimeters. If your STL was exported in inches or meters, the geometry will appear at the wrong scale.