Preparing CAD Files

The model should define exact nominal geometry. The drawing should define tolerances, GD&T, threads, material, finish, edge conditions and inspection requirements that cannot be inferred safely from the model. The RFQ should identify quantity, active revision, application context and target timing.

More files do not automatically create more clarity. Duplicate models, screenshots, superseded drawings and conflicting notes slow review because engineering must determine which source controls. A small authoritative package is better than a large archive with an unclear hierarchy.

If a drawing is not required for a simple part, state which general tolerance and finish expectations should govern. Never rely on the number of decimal places in a model to communicate acceptance limits.

STEP and Parasolid preserve analytical faces, curves, topology and units in a form most manufacturing systems can interrogate. IGES can carry legacy surface data but may arrive as disconnected or damaged surfaces. STL and OBJ approximate geometry with triangles and do not preserve exact cylinders, holes or design features.

For CNC machining, STEP (.stp or .step) and Parasolid (.x_t) are preferred neutral formats. Native CAD can help when feature history, assemblies, configurations or editable references add value, but it should accompany—not replace—a stable neutral export.

For laser-cut or sheet profiles, export DXF at 1:1 scale with closed contours, no duplicate lines and no drawing-border geometry. Confirm whether bend information belongs in a separate drawing or model.

A 3D model communicates shape but usually does not communicate the complete requirement hierarchy. Use a drawing for material and condition, tolerances, datum structure, threads, inserts, surface texture, coating, cosmetic zones and required records.

Dimension features from functional datums and avoid chains that create unnecessary tolerance accumulation. Apply tight limits only where function needs them, and make basic, reference and inspection dimensions visually unambiguous.

When model-based definition is the authority, identify the controlled standard and provide a viewable derivative or inspection dataset appropriate to the supplier workflow. Do not assume embedded annotations survive every neutral-file translation.

Part number and revision should agree across the solid model, drawing, quote request and purchase order. Remove superseded files from the issue package or place them in a clearly marked reference folder that cannot be mistaken for production authority.

Use stable filenames that identify the part and revision without encoding informal instructions. Revision control belongs inside the released definition and business record, not only in an email subject or cloud-folder date.

If a change is released during quotation, identify exactly which files are replaced and whether prior price, tooling or inspection assumptions remain valid.

An export can succeed while still losing bodies, changing units, breaking surfaces or omitting drawing fonts. Reopen the neutral file in a second viewer where practical, then check overall size, body count, critical holes, threads, surface orientation and drawing legibility.

For assemblies, decide whether the supplier needs the complete context, a simplified envelope or only manufactured components. Suppress proprietary or irrelevant internals when they are not necessary to interpret interfaces.

Compress the final package only after validation. Use a concise manifest when multiple part numbers are included, and keep confidential files within the agreed transfer and NDA process.

A model can open perfectly and still be unsafe to manufacture if the drawing shows a different revision, units are unclear or a note changes material without updating the title block. These conflicts create quotation assumptions that later become change orders, rework or inspection disputes.

Another common failure is using a screenshot to communicate a critical dimension or cosmetic zone. Screenshots are useful context, but they are not controlled geometry and rarely carry enough information for repeat inspection. Put acceptance requirements in the drawing or an approved specification.

Assembly exports can also hide duplicated bodies, purchased hardware, virtual components or alternate configurations. Before release, isolate the manufactured part and identify reference geometry explicitly.

Mockup engineering begins by confirming part identity, revision, units, solid integrity, material, quantity and drawing hierarchy. The team then reviews tool access, tolerance risk, finishing effects and inspection deliverables against the same controlled package.

If information is missing, Mockup returns named questions rather than filling gaps with silent assumptions. That may include confirming whether dimensions apply before or after coating, whether a mesh is acceptable as source geometry, or which datum relationship drives function.

This review protects both early prototypes and repeat orders. The approved file set, DFM decisions and inspection expectations remain connected so a later order does not have to reconstruct the engineering history from email threads.

A complete package lets engineering spend time on manufacturability and process choice rather than reconstructing the requirement.