Custom Metal Part Quotation from a 3D Model: STEP File Checklist

Quick answer: A 3D model can support an initial custom metal part quotation, but geometry alone may leave important requirements undefined. For a sheet metal RFQ, send the current STEP/STP model with controlled requirements for material, tolerances, hardware, welds, finish, quantity and inspection. A matching PDF is a practical way to communicate details that are missing from the model.

This guide explains when a model is ready for quotation and what to resolve before ordering. It concerns drawing-based mechanical sheet metal parts, not a complete electronic product or an automatic price guarantee.

1. Decide whether you need an estimate or an order-ready quotation

If the design is still changing, say so. Request an estimate with clearly stated assumptions and identify which inputs remain open. Do not treat an estimate for an unfinished concept as approval to manufacture a released part.

For an order-ready quotation, agree on the exact files and specifications being priced. The supplier should identify unresolved manufacturing questions, excluded work and any assumptions affecting price or schedule. A later design change may legitimately need a revised quotation; the change and its effect should be approved before work proceeds.

2. Check what the model actually communicates

A rendered gray cabinet is not a powder-coating specification. Likewise, a modeled hole is not necessarily a finished thread. These details need an agreed source, whether a drawing, BOM, controlled specification or accepted model-based definition.

3. Resolve file conflicts instead of guessing which one wins

Give the model, drawing and BOM matching part numbers and revisions. Identify obsolete files when sending an update. If a mounting pattern differs between the STEP file and PDF, stop and clarify the intended requirement before the supplier prepares production data.

Illustrative example, not a customer case: The PDF calls for four installed studs, while the model contains only four plain holes. The RFQ should identify the stud specification and installation side. The supplier should not silently price plain holes or choose a substitute stud.

Protolabs’ sheet metal quoting guidance similarly explains that a drawing can supply hardware information missing from a CAD model. Its platform rules and standard tolerances are not MSTFAB’s quotation terms.

4. Ask for a list of manufacturing questions before release

Relevant questions may include bend access, features near bends, hardware installation clearance, weld access and finished-part fit. There is no single hole-to-bend distance or tolerance that approves every material, thickness and geometry.

A manufacturability comment is a proposal, not permission to change your design. Record the feature affected, the proposed correction and the approving party. Changes to a sealing joint, mounting interface or functional requirement need review by the responsible designer.

For fabrication scope, see our sheet metal fabrication services. The quotation should state which operations and inspection records are included rather than implying that every available process is part of every order.

5. Confirm the finished condition and first-article evidence

State whether critical dimensions apply before or after forming, welding and finishing. Identify threads and contact areas requiring masking, along with the required surface treatment. Coating thickness and inspection frequency should follow the approved specification, not a generic website value.

Agree on the first-article measurements, mating-part trial fit where needed and deviation approval. A photograph is useful context, but it does not replace a dimension report or prove a completed assembly’s performance.

Before sending your STEP file

• Confirm units, part number and revision.
• Include a matching PDF and BOM where applicable.
• State material, quantity, finish and hardware requirements.
• Mark critical interfaces and the required inspection records.
• Identify whether a supplied flat pattern is controlled or for reference.
• List open design questions and request that assumptions be recorded.

If confidentiality terms are needed, request agreement before sending sensitive files. Provide the mechanical interface information required for quotation without including unrelated proprietary electronics or software.

MSTFAB scope: Drawing-based sheet metal parts, empty enclosure shells and specified mechanical assemblies. Electronics, wiring and final-equipment validation remain outside this fabrication scope unless separately agreed in writing. Tolerances, delivery dates and commercial terms are confirmed for the actual order.

Send your model and controlled requirements for review.