A356 Casting Plus CNC Machining RFQ Package: What Buyers Should Send

# A356 Casting Plus CNC Machining RFQ Package: What Buyers Should Send

Many overseas buyers ask for "A356 casting with machining" and expect suppliers to quote the same scope. In practice, two suppliers may read that phrase very differently. One may include T6 heat treatment, datum-controlled CNC machining, pressure testing, cleaning, and export packing. Another may only quote rough casting with basic trimming. The price comparison then looks useful but is not comparable.

For A356 parts such as pump housings, valve bodies, brackets, motor covers, and fluid-path housings, the RFQ package should separate casting scope, heat-treatment scope, machining scope, inspection scope, and shipping assumptions. That gives the buyer a quote that can be audited, negotiated, and compared without hiding risk in unclear assumptions.

Use this checklist when preparing an RFQ for A356 aluminum casting, aluminum casting plus CNC machining, or a China casting supplier comparison.

Start with a one-page scope summary

The first page of the RFQ should answer the supplier's commercial and engineering questions before they open the drawing files.

Include:

• •part name and part number
• •current revision
• •target annual volume and first order quantity
• •prototype, pilot, or production status
• •target alloy such as A356, A356-T6, ZL114, or another specification
• •casting process preference if known
• •machining included or excluded
• •surface treatment included or excluded
• •inspection reports required with samples and production lots
• •delivery destination and Incoterm assumption if available

This summary prevents a common quote error: one supplier prices casting only while another includes machining, coating, and reports.

Attach both 2D drawing and 3D model

A 3D STEP model helps the foundry review geometry, tooling direction, draft, gating risk, wall thickness, and machining allowance. The 2D drawing controls the commercial and quality requirements. Buyers should avoid sending only one of them.

The 2D drawing should define:

• •revision and release status
• •critical dimensions
• •tolerance standard if general tolerances apply
• •datum scheme for machining
• •machined surfaces and as-cast surfaces
• •threaded holes, ports, bores, and sealing faces
• •surface roughness requirements
• •heat treatment requirement
• •inspection notes
• •marking and traceability notes

The 3D model should match the drawing revision. If the model and drawing conflict, state which file controls quotation.

Define casting process and alloy assumptions

A356 is often selected for gravity casting or low-pressure casting where strength, ductility, and pressure-tightness risk matter more than the lowest piece price. For some parts, ADC12 die casting may be cheaper, but it may not match the same elongation, heat-treatment, or leak-risk requirements. The RFQ should say whether the buyer is requesting a specific alloy or asking the supplier to recommend one.

For A356-T6, include the property or standard requirement instead of writing only "T6". If tensile strength, elongation, hardness, or proof stress is important, state the target and whether test bars, witness coupons, or part cut-ups are required.

Useful internal references:

• •A356 alloy guide
• •Gravity casting process
• •Low-pressure casting process
• •Casting process selection resource

Separate CNC machining from casting

Machining is where many quote comparisons break down. A supplier may see "machining included" and assume only rough facing. The buyer may expect complete CNC finishing, tapped holes, seal-face control, washing, deburring, and final inspection.

Define machining scope by feature:

• •datum surfaces
• •bores
• •seal faces
• •mounting faces
• •threaded holes
• •port faces
• •slots, grooves, or counterbores
• •features that remain as-cast
• •features that require deburring or edge break

If the part has pressure or sealing requirements, state whether leak testing happens before machining, after machining, or both during validation. For housings, machining can open porosity near ports or seal faces, so the final leak-test stage matters.

State inspection and reporting requirements

An A356 casting quote should not only include price. It should say what evidence the supplier will provide. Buyers should decide which reports are required for samples and which are required for production.

Common report items:

• •dimensional inspection report
• •material certificate
• •heat-treatment record
• •hardness record
• •CMM report for critical dimensions
• •surface finish check
• •pressure or leak-test record
• •X-ray, CT, or dye penetrant test if required
• •packaging photos for export shipments

For production sourcing, ask whether inspection records are provided every lot, only for first article, or only upon request.

Make quote comparison easier

Use a scope table in the RFQ and ask every supplier to mark included, excluded, or quoted separately.

This table also helps AI search and procurement teams understand the buying intent: the project is not just "aluminum casting"; it is a complete casting-plus-machining sourcing package.

When to send Bohua an RFQ

Send Bohua the drawing, STEP file, annual volume, target alloy, machining scope, inspection notes, and destination assumption. For a structured upload path, use request quote. If you are still comparing suppliers, start with the OEM aluminum casting quote checklist and the supplier capability sheet.

FAQ

Should I ask for A356-T6 in the RFQ if I am not sure the part needs heat treatment?

State the requirement as provisional. Ask the supplier to quote A356-T6 and comment whether the part function, drawing, and cost target support that choice. If the part does not need T6 properties, the supplier can quote an alternative condition as a comparison.

Is it better to quote casting and machining from one supplier?

For housings and sealing parts, one coordinated casting plus machining source can reduce handoff risk because machining datums, allowance, leak testing, and inspection plans are reviewed together. For very high-volume programs, buyers may still separate casting and machining, but the RFQ should state the split clearly.

What is the most common missing item in A356 machining RFQs?

Datum and inspection requirements. Buyers often send a STEP file and ask for machining, but the supplier needs to know which surfaces control setup, which dimensions are critical, and what report format is required.

Should leak testing be quoted as part of machining or casting?

It should be quoted as its own line item. Leak testing may require fixtures, defined pressure, medium, time, and acceptance criteria. It can happen after casting, after machining, or both during validation, so it should not be hidden inside a generic machining price.