Sand casting and gravity die casting are alternative routes for some aluminum components, but their suitability depends on the part and production plan. A useful comparison starts with the same drawing, alloy requirement, delivered condition and acceptance criteria. Comparing unrelated typical values can conceal the operations needed to deliver the finished part.
Define the Route Being Compared
Sand casting uses an expendable mold system. Gravity die casting uses a reusable mold with gravity filling; the actual tooling may still use expendable cores for internal geometry. Specify the proposed mold and core arrangement rather than assuming that either label describes every feature or operation.
Ask the supplier to explain parting, draft, cores, feeding, trimming, heat treatment when specified and machining. The route must support the drawing and approved material condition, not merely reproduce the outside shape.
Compare Tooling and Geometry
| Review area | Questions for the sand-casting proposal | Questions for the gravity-die proposal |
|---|---|---|
| Tooling scope | Which patterns, core boxes and fixtures are included? | Which mold, inserts, core equipment and fixtures are included? |
| Internal passages | How will cores locate and be removed or cleaned? | Which features need cores and how are they controlled? |
| Design changes | Which tools and approvals change with the drawing? | Which mold elements and process approvals need revision? |
| Program demand | How will batch size and releases be supported? | What tooling life and maintenance assumptions support the demand? |
| Delivered part | Which operations remain after casting? | Which operations remain after casting? |
Do not assign one route to every prototype or every medium-volume program. Tool reuse, design stability, geometry, development timing and the required validation can change the decision.
Use Comparable Dimensional Evidence
A general plus/minus range is not a fair accuracy comparison unless it refers to the same dimension, geometry, casting state and measurement basis. A process described as more accurate cannot be justified by a table that uses different size bands or mixes total tolerance width with bilateral values.
Provide the controlling standard and edition, general note, individual dimensions and geometrical controls. Review the casting tolerances guide and obtain the applicable controlled standard. The public ISO 8062-3 scope is a starting point for checking applicability, not a substitute for its numerical tables.
Surface Texture Is Not a Unit-Free Process Score
RFQ CTA
Have a casting project? Submit the RFQ details, then email your drawing for a structured quote review.
Send the drawing, target alloy, finishing scope, MOQ, and delivery timing. Bohua will review it like a real sourcing project, not a generic contact request.
Ask which surfaces are as cast and which will be machined or finished. State the texture parameter, unit and method where a numerical limit is required. An RMS/Rq value and an Ra value cannot be treated as the same metric, and an unspecified unit makes a comparison incomplete.
Use relevant sample or production evidence to discuss achievable surfaces. Do not promise that a route will automatically eliminate machining on sealing faces, bearing seats or other functional features. Their final geometry and acceptance criteria control that decision.
Compare the Complete Commercial Scope
Request separate lines for tooling, casting, heat treatment, machining, finishing, inspection and packaging. State sample, pilot, annual and lifetime quantities. Include maintenance, replacements, requalification and change ownership where they affect the program.
Keep manufacturing cost separate from transport, duties and other destination costs. Use dated quotations and explicit assumptions; no fixed annual quantity guarantees that one process is cheaper. A preliminary estimate should identify unresolved design and acceptance questions.
Approval Plan Before Tool Release
- •Confirm the drawing and model revision and the material requirement.
- •Identify critical zones, machined datums, internal passages and inspection access.
- •Agree first-article evidence and the production control plan.
- •Define permitted repairs, deviations and change notification.
- •Confirm tool ownership, maintenance, delivery milestones and responsibilities.
- •Compare quotations only after inclusions and exclusions are aligned.
FAQ
Does gravity die casting always achieve tighter tolerances?
No universal numerical guarantee follows from the process name. Compare the same features against approved requirements and evidence from the proposed route.
Should a prototype use the eventual production process?
Use the route that answers the prototype's purpose. If it is meant to validate production material or process behavior, identify any differences and the later validation still required.
What should a buyer send for route selection?
Provide the drawing, critical features, alloy/temper requirements, quantity plan and acceptance package through the process-comparison RFQ route.
Project CTA
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Submit the RFQ details here, then email your drawing for a structured DFM review and quote.