Permanent mold aluminum casting uses a reusable metal mold to form the part. This guide focuses on the gravity-filled route, often called gravity die casting, rather than treating every metal-mold process as identical. Low-pressure casting also uses permanent tooling but fills and feeds the cavity differently.
For a housing with machined bores, sealing faces or heat-treatment requirements, compare the complete casting-and-finishing route. Reusable tooling alone does not prove pressure tightness, dimensional capability or a lower total cost.
Gravity permanent mold, sand, LPDC or HPDC?
| Route to review | Useful project question | Limitation to resolve |
|---|---|---|
| Gravity permanent mold | Can repeat orders reuse the mold, with an alloy and finishing route suited to the drawing? | Feeding, mold release, cores and machining stock still need a part-specific review |
| Sand casting | Is the geometry changing, or does the cavity/core arrangement favor expendable molds? | Agree dimensional allowances and the finishing plan |
| Low-pressure casting (LPDC) | Would controlled bottom filling and feeding suit the component? | Compare tooling, cycle, alloy and the required inspection evidence |
| High-pressure die casting (HPDC) | Does thin-wall repeat production justify this tooling and alloy route? | Confirm internal integrity and any heat-treatment or joining constraints |
This is a process-review checklist, not a universal cost or tolerance ranking. See Bohua's gravity casting process for the factory service scope and the A356 material page for related housing examples.
What the process does
The supplier prepares and conditions the metal mold, places any approved cores or inserts, fills the cavity, controls feeding and solidification, removes and trims the part, and completes the agreed heat treatment, machining, finishing and inspection.
A metal mold generally extracts heat faster than a sand mold, which can refine the local solidification structure. The result still depends on section thickness, gating, feeding, mold temperature, local cooling and alloy preparation. Permanent-mold casting does not guarantee zero porosity, a fixed surface finish or a universal tolerance.
When to compare it with another route
Evaluate permanent mold when the program needs:
- •reusable tooling for repeat orders;
- •an alloy and temper compatible with the required properties;
- •machining of datums, bores, threads or sealing faces;
- •pressure-tightness or internal-integrity controls defined by the buyer;
- •traceability and approval records tied to production lots.
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.
Sand casting may be more practical for very low volume, large geometry or frequent design changes. HPDC may be more practical for thin-wall, very high-volume parts when its alloy, porosity and heat-treatment constraints fit the function. LPDC may be evaluated when controlled bottom filling and feeding suit the geometry. Do not select a process from an annual-volume threshold alone.
Standards: keep the scopes separate
- •ASTM B108/B108M is a material specification for aluminium-alloy permanent-mold castings. It is not a generic dimensional-tolerance table for every design.
- •ASTM B557/B557M defines tensile test methods. Mechanical-property requirements come from the controlling material specification and drawing.
- •ASTM E505 contains reference radiographs for aluminium and magnesium die castings. Do not assign its levels to a gravity casting without a documented scope review and buyer-manufacturer agreement.
- •IATF 16949 is a quality-management-system standard. It does not define the strength of an A356 casting.
Where radiographic inspection is required, the drawing or inspection plan should identify an applicable reference, material and thickness range, image method, areas to inspect, sampling frequency and acceptance severity.
The ASTM B108/B108M scope identifies the material specification. For a separate dimensional review, use the casting tolerances guide; do not infer a plus/minus tolerance from the alloy designation.
Pressure-tight and machined parts
For housings, manifolds and valve or pump components, mark the pressure boundary and every surface opened by machining. Define test medium, pressure, hold time, allowable leakage, test stage and sampling or 100% requirement. Also define whether impregnation or weld repair is allowed.
Machining can reveal subsurface discontinuities that were not visible in the as-cast surface. The DFM review should therefore connect casting stock, datum scheme, feeding, inspection zones and final leak-test stage.
The aluminum casting leak-test guide helps distinguish helium, pressure-decay and bubble-test requirements. For a pump-specific drawing package, see the seal-chamber and bearing-bore inspection checklist.
RFQ checklist
Send:
- •revision-controlled 2D drawing and 3D model;
- •alloy, temper and controlling specification with edition;
- •prototype and annual quantities;
- •machined datums, bores, threads and sealing faces;
- •heat-treatment and finishing scope;
- •dimensional, mechanical, NDT and pressure-test acceptance criteria;
- •traceability, PPAP or other approval requirements;
- •destination, Incoterm and target first-article timing.
Request a drawing-based permanent-mold review.
*The purchased standards, customer drawing and approved control plan govern acceptance. This guide does not replace them.*
Project CTA
Ready to Source This Part?
Submit the RFQ details here, then email your drawing for a structured DFM review and quote.