When Native CAD and STEP Disagree at Supplier Handoff

The supplier can open the model, but a component is missing, the expected feature tree has disappeared or the assembly cannot be edited as intended. These problems call for different remedies. Re-exporting the same model repeatedly is unlikely to help until both sides identify what information the handoff needs to preserve.

Disclosure: This guide was prepared for CADProps, which provides CAD inspection tools. It describes a practical diagnostic sequence rather than a claim that one format or viewer is always best.

First separate the editable source from the exchange deliverable

Ask the receiver what they need to do: quote nominal geometry, prepare CAM, modify the design or consume manufacturing annotations. Then assign a role to each delivered file.

For example, a native package may be the editable collaboration source, while a STEP export is the geometry snapshot for another system. A controlled drawing may carry manufacturing requirements outside either workflow. Identify the same revision and configuration across those files, and state what governs if they disagree.

This short statement prevents a common ambiguity: a supplier treating a convenient preview as permission to manufacture, or expecting a neutral export to behave like the original authoring model.

The assembly opens but some parts are missing

Start with dependencies and configuration. A native assembly can reference separate part and subassembly files. Sending only the top-level file may leave the receiver with unresolved references even though the sender’s workstation opens it normally.

Use the source application’s collection workflow and inspect its contents. Autodesk’s guidance for moving SOLIDWORKS assemblies into Fusion recommends collecting the assembly and its part files with Pack and Go; it also identifies STEP export as an alternative route. Autodesk assembly-transfer guidance

Then test the package away from the sender’s original file locations. Confirm the intended configuration, suppressed items, external references and receiver version. For a STEP deliverable, check whether the export was self-contained or produced accompanying files. A neutral extension alone does not settle packaging.

Record whether an absence is intentional. A motor omitted from a machined-parts quote is different from a bracket lost during export. Do not substitute a similarly named local file without confirming its identity and revision.

The shape arrives but the feature tree does not

An imported body can be useful for machining or geometric review without reproducing the original sequence of sketches, constraints, patterns and features. If continued parametric editing is a requirement, agree a compatible native workflow before the handoff.

Feature recognition or direct editing may help in some receiving applications, but neither should be treated as proof that the original design intent has been recovered. Test the actual edits the supplier must make: change the driving dimension, rebuild the intended configuration and check dependent geometry.

For a geometry-only task, absence of the authoring history may be acceptable. Record that decision instead of labeling every imported body a failed translation.

The model looks right but its structure has changed

A receiving system may display a multi-body part where the sender expected an assembly, or organize names and instances differently. First check physical completeness and placement. Then check whether hierarchy itself matters to the task.

If the supplier must select components individually, attach operations to parts or reconcile a controlled parts list, flattened structure may be a real problem even when the overall shape is intact. Ask for the export settings and test a small representative subassembly before repeating a large transfer.

Conversely, a different tree presentation is not automatically evidence of lost geometry. Document the distinction between component identity, repeated instances and body count. Do not assume that an assembly tree is the purchasing BOM or that it carries order quantities.

Required annotations are absent or unusable

STEP can carry more than surfaces and solids. NIST distinguishes graphic PMI, which communicates the visible annotation, from semantic PMI, which carries computer-interpretable meaning. Those are different requirements for a reader inspecting a drawing-like view and software consuming a tolerance definition. NIST STEP analysis documentation

If PMI is essential, run an end-to-end test with the actual exporter and receiving application. Choose a small set of required annotations, then verify their values, associations and intended downstream use. Merely selecting AP242 or seeing text on screen is insufficient acceptance evidence.

Keep the controlled manufacturing definition accessible through an agreed alternative until the intended exchange has been demonstrated. Do not infer manufacturing tolerances from nominal shape.

A number changes after conversion

Compare like with like before blaming a translator. Confirm units, revision, configuration, included bodies and the definition of the reported quantity. An assembly result that excludes a missing component cannot be compared fairly with the complete native model.

Check a few distinctive dimensions and interfaces alongside any aggregate properties. Matching volume does not establish identical shape. If an unexplained discrepancy remains, preserve both files, note the software versions and settings, and ask the sender to reproduce it using the smallest authorized example.

The CADProps format matrix describes its supported inspection and conversion paths and their limits. Native-file compatibility varies, and partial assemblies describe loaded geometry only. CADProps does not restore the original parametric history from STEP. Confidential files should only be uploaded under the organization’s approved handling policy; CADProps uses server-side processing.

Close the loop with a two-sided test

Before making a format the default for future deliveries, agree a small acceptance package. Include the intended editable task if native CAD is required, representative assembly references, one known dimension, a placement check and any essential PMI.

Have the receiver reopen the exact delivery and report the result with their application version. Keep the export settings and exceptions beside it. This creates a repeatable agreement about what transfers successfully, without pretending that a filename extension guarantees the outcome.