Supported Formats

LOP accepts STEP files conforming to the ISO 10303 standard — the most widely supported 3D CAD interchange format, natively exported by every major CAD platform — as well as the common mesh formats STL, OBJ, and PLY.

Accepted File Formats

Mesh Formats (STL, OBJ, PLY)

Mesh files describe an item's surface as triangles, without the exact solid geometry a STEP file carries. LOP accepts them with a few behaviors worth knowing:

Units. Unlike STEP, mesh files carry no unit information — a value of 100 could mean 100 mm or 100 inches. When you select a mesh file, a unit selector appears in the upload form: millimeters (default), centimeters, meters, or inches. Pick the units your CAD tool exported in; LOP scales the geometry to millimeters accordingly.

Size sanity check. If the scaled part comes out implausibly small (largest dimension under 10 mm) or implausibly large (over 20 m), LOP shows a warning so you can catch a wrong unit choice. This is a warning only — the upload still proceeds, and you can re-upload with the correct units if the dimensions look wrong.

Multi-body files. A mesh file containing several separate bodies is imported as a single item with a combined (union) bounding box, the same way STEP assemblies are treated.

Volume. For a closed, watertight mesh, LOP computes the exact material volume. For meshes with holes or gaps in the surface, it falls back to a conservative estimate (convex hull, then bounding box) — the bounding-box dimensions used for packing are unaffected.

SolidWorks .sldprt files are a proprietary format and cannot be read directly. LOP declines them at upload with guidance: in SolidWorks, use File → Save As → STL (or export as STEP AP214) and upload that file instead.

STEP AP203 vs AP214

Both AP203 and AP214 are accepted, but AP214 is recommended for better compatibility.

STEP AP203 (Configuration Controlled 3D Design) — the older protocol, focused on geometric shape data only. Widely supported but does not carry color, layer, or material information.

STEP AP214 (Automotive Design) — the modern protocol with a richer data model. Carries color and appearance information that LOP can use to set item colors automatically. If your model has color-coded parts, AP214 preserves this in the import.

When exporting from your CAD tool, select AP214 if both options are available.

Compatible CAD Software

The following CAD platforms can export STEP files compatible with LOP. Export instructions vary by version; consult your software's documentation for the exact menu path.

SolidWorks

File → Save As → File Type: STEP AP214 (*.step)

Native .sldprt part files cannot be uploaded directly — always export as STEP (or STL) first.

Recommended settings:

• Export: Solid and surface geometry
• Include: Default (no internal hidden bodies needed)
• Do not embed thumbnail

Autodesk Fusion 360

File → Export → Format: STEP (*.step)

Fusion 360 exports AP214 by default. No additional configuration is needed.

CATIA V5 / V6

File → Save As → Type: STEP (*.stp)

For assemblies, ensure "Save all instances" is selected to include all sub-parts in a single file.

Siemens NX (Unigraphics)

File → Export → STEP 214

In the export dialog, set Output as: Solid and sheet bodies.

Autodesk Inventor

File → Save As → Save As Type: STEP Files (*.stp)

Select AP214 in the STEP Export Options dialog.

PTC Creo (Pro/ENGINEER)

File → Save a Copy → Type: STEP (*.stp)

Set the export profile to AP214 for best results.

FreeCAD (open source)

File → Export → STEP with Colors (*.step, *.stp)

FreeCAD exports AP214 with color information when using the colored STEP option.

Onshape (cloud-based)

Right-click the Part Studio or Assembly → Export → Format: STEP

Single-Part vs Assembly Files

Both single-part and assembly STEP files are accepted.

Single-part files contain one solid body. These process fastest and most reliably.

Assembly files contain multiple parts with positional relationships. LOP reads the assembly hierarchy and treats the entire assembly as a single item with a unified bounding box. The 3D preview renders all components in their correct relative positions.

Geometry Requirements

For STEP files, LOP's parser expects manifold solid geometry — the mathematical requirement that every edge is shared by exactly two faces, with no holes or gaps in the surface. Most CAD-native solid models are manifold by construction, but geometry that has been imported, repaired, or exported multiple times can develop surface errors.

Mesh files (STL, OBJ, PLY) are more forgiving: a non-watertight mesh still imports, with the material volume falling back to a conservative estimate. Packing dimensions come from the bounding box either way.

If you encounter parsing failures, your CAD tool's geometry repair function (or a dedicated mesh repair tool like MeshLab or Netfabb) can often fix manifold issues.

File Size Limits

• Maximum file size: 150 MB — STEP and mesh files above this are refused at processing, with guidance to split the assembly or simplify the model
• Recommended maximum for reliable processing: 100 MB

Files over 100 MB will process successfully in most cases but take longer and carry a higher risk of timeout. If your file is very large, use your CAD tool to:

• Remove internal components and features not visible from the outside
• Suppress representations of threaded holes and fine surface details
• Use a lower tessellation quality setting on any mesh-based features
• Export only the solid bodies that define the external envelope

Units and Coordinate Systems

STEP files encode dimensional units internally. LOP reads the unit specification from the file header and converts all dimensions to millimeters automatically. You do not need to pre-scale your model.

Supported units in STEP files: millimeters, centimeters, inches, feet. All are converted to mm on import.

Mesh files (STL, OBJ, PLY) carry no unit information — for these, the upload form asks you to select the source units (mm, cm, m, or in; millimeters is the default). See Mesh Formats above.

The bounding box is computed relative to the world axis system in the file. If your model is oriented at an angle relative to the world axes, the bounding box will be larger than the actual part envelope. Orient the model with its packing face aligned to the XY plane before export for accurate results.