Gravity vs Low-Pressure vs Die Casting for Leak-Tight Housings

# Gravity vs Low-Pressure vs Die Casting for Leak-Tight Housings

Leak-tight aluminum housings should not be quoted by process name alone. A buyer may ask three suppliers for gravity casting, low-pressure casting, and high-pressure die casting, then receive prices that look comparable but include different assumptions about alloy, porosity control, machining exposure, leak-test stage, tooling life, and inspection records.

For pump housings, hydraulic valve bodies, coolant manifolds, converter housings, and EV thermal-management parts, the better RFQ question is:

Which casting route can meet the drawing function, sealing risk, machining scope, annual volume, and approval evidence with the fewest hidden assumptions?

Quick decision frame

Use the table below to structure an RFQ discussion. It is not a universal process rule. The drawing, alloy, wall thickness, sealing method, and customer standard decide the final route.

When gravity casting may be worth quoting

Gravity casting is often worth reviewing when the part has thicker sections, machined sealing faces, pressure or fluid paths, and moderate production volume. For leak-tight housings, ask the supplier to review:

• •sealed cavity maps
• •riser and feeding assumptions
• •machining allowance around sealing lands and ports
• •leak-test stage before or after machining
• •CMM datum strategy for sealing faces and bores
• •whether impregnation is allowed, restricted, recorded, or disallowed

For material routes, compare the drawing against A356, ZL114, and project-specific buyer standards. If the part already sits in a pressure-tight family, also review the leak-tight aluminum casting hub.

When low-pressure casting should be considered

Low-pressure casting may be useful when controlled filling, repeatability, and geometry-specific solidification control matter. It should still be quoted with the same RFQ discipline:

• •alloy and heat-treatment expectations
• •tooling and sample approval plan
• •fixture assumptions
• •leak-test method and sampling level
• •machining datum plan
• •CMM and material documentation scope

Do not accept a process label as proof. Ask what the supplier will measure, when it will test, and which records will be delivered with first samples.

When high-pressure die casting may fit

High-pressure die casting can be attractive for higher-volume thin-wall components and repeatable geometry. For leak-sensitive housings, buyers should confirm whether the part is truly suitable for die casting before comparing price.

Key RFQ questions:

• •Is the alloy compatible with the functional requirement?
• •Will machining open internal porosity near ports, grooves, or sealing faces?
• •Is pressure-tight performance required by drawing or only preferred?
• •Is vacuum die casting, post-treatment, or impregnation being assumed?
• •Does the supplier price leak testing and retesting into the quote?

If ADC12 is proposed, compare it with the ADC12 material page and ask the supplier to explain where the process is strong and where it is risky for the drawing.

RFQ package to send

For a fair process comparison, send one RFQ package and ask suppliers to respond against the same assumptions:

• •2D drawing and 3D model.
• •Annual volume and launch quantity.
• •Alloy or allowed equivalent materials.
• •Pressure, coolant, oil, air, or vacuum exposure.
• •Leak-test method, pressure, hold time, and acceptance criteria if known.
• •Machining scope for ports, threads, O-ring grooves, bores, and sealing faces.
• •CMM datum scheme and critical dimensions.
• •Surface finishing and cleanliness requirements.
• •PPAP, FAI, CMM, material certificate, and leak-test record requirements.
• •Whether vacuum impregnation is allowed, restricted, or not allowed.

How to compare supplier answers

The best answer is not simply "we can do gravity casting" or "die casting is cheaper." A quote-ready answer should identify the process route, risk points, open assumptions, test method, inspection records, tooling path, machining scope, and commercial exclusions.

Watch for weak answers:

• •quoting by casting weight only
• •ignoring machined sealing faces
• •treating leak testing as optional when the part is pressure-related
• •offering a lower price without saying what records are excluded
• •recommending impregnation without asking whether the buyer allows it
• •promising a fixed lead time before reviewing drawing complexity

Bohua RFQ path

Bohua can review gravity, low-pressure, and die-casting assumptions for leak-tight aluminum housings when the buyer provides drawings, annual volume, alloy expectations, machining areas, and test requirements. For quote-ready projects, use the formal RFQ form. For route comparison, start with the RFQ landing page, gravity casting page, and leak-tight casting hub.

FAQ

Is gravity casting always better for leak-tight housings?

No. Gravity casting can be a strong candidate for certain leak-tight housings, but the right route depends on alloy, wall thickness, machining exposure, volume, sealing method, and inspection requirements.

Is die casting unsuitable for every pressure-related housing?

No. Some die-cast housings can be suitable when the design, alloy, process controls, and testing plan match the requirement. The buyer should ask how machined surfaces and internal porosity risk will be controlled.

Should the RFQ specify vacuum impregnation?

Only if the buyer's engineering and quality requirements allow it. The RFQ should state whether impregnation is allowed, disallowed, recorded as repair, or subject to retesting.

What is the fastest way to get comparable quotes?

Send one complete drawing package and ask every supplier to price the same process assumptions, machining scope, leak-test method, CMM records, and approval documents.