Second-Source Casting Supplier Audit Checklist for OEM Buyers

# Second-Source Casting Supplier Audit Checklist for OEM Buyers

Second-source sourcing is not the same as normal price shopping. The buyer is usually trying to reduce supply risk, qualify an alternate foundry, solve quality instability, or create leverage before a new program launch. That means the audit should focus on evidence: what the supplier can actually make, measure, document, and repeat.

A useful second-source audit does not need to start with a factory visit. Buyers can screen a supplier by asking for structured RFQ evidence first, then deciding whether a deeper visit, sample order, or engineering review is worth the time. This checklist is designed for aluminum castings such as pump housings, valve bodies, gearbox housings, brackets, intake manifolds, and A356 aluminum casting parts.

Start with the risk you are trying to reduce

Before auditing suppliers, write down why the second source is needed. Different goals require different evidence.

Common second-source goals:

• •reduce single-source supply risk
• •compare landed cost without changing design
• •solve late delivery or capacity risk
• •improve casting quality or machining consistency
• •add China sourcing coverage for a North America or Europe program
• •qualify a backup before a tooling transfer
• •source a new revision while the current supplier stays active

If the reason is unclear, the audit becomes generic. If the reason is clear, the supplier can be tested against the real business risk.

Desk audit before factory audit

A desk audit is a document-based screen. It saves time because weak suppliers often fail here before travel, samples, or tooling discussion.

Ask for:

• •company profile and main casting processes
• •product examples close to your part family
• •alloy range and heat-treatment capability
• •casting weight and size range
• •CNC machining scope if included
• •inspection equipment list
• •quality-system certificate if available
• •typical export markets
• •RFQ contact process and engineering review process
• •sample inspection report example with sensitive customer data removed

This is not about collecting brochures. The goal is to confirm whether the supplier's real process range matches the part.

Process capability questions

The supplier should be able to explain why a casting route fits your part. A quote-only supplier may give a price without discussing gating, wall thickness, machining allowance, leak-risk zones, or tolerance limits.

Ask:

• •Which casting process would you recommend for this part and why?
• •What geometry features create tooling or feeding risk?
• •Which surfaces should remain as-cast and which need machining?
• •Where would you place machining datum references?
• •What alloy and heat-treatment assumptions are included?
• •What inspection steps are included for samples?
• •What would you change in the drawing before tooling?

For fluid housings, add questions about pressure testing, sealing faces, and port machining. For structural brackets, add questions about heat treatment, elongation, and dimensional stability.

Quality evidence to request

Do not ask only "Do you have ISO certification?" Certification can be useful, but buyer risk is reduced by project-level evidence.

Request examples of:

• •first article inspection format
• •CMM report format
• •material certificate format
• •heat-treatment record format
• •nonconforming material process
• •corrective action report format
• •traceability label or batch record
• •packaging inspection photos

The supplier can remove customer names and part numbers. What matters is whether the format is organized, repeatable, and appropriate for the buyer's program.

Compare second-source quotes by scope

Second-source quotes often look cheaper because something is missing. Use a scope comparison table.

This table helps procurement teams avoid awarding a second source that later becomes expensive because fixture, inspection, machining, or packaging was excluded.

Warning signs during supplier evaluation

Be careful when a supplier:

• •quotes without asking about annual volume, drawing revision, or inspection scope
• •avoids discussing machining datum or critical dimensions
• •cannot explain casting process choice
• •says every surface finish, tolerance, or lead time is easy before reviewing the drawing
• •provides only marketing photos and no inspection-format examples
• •cannot separate tooling, casting, machining, and inspection cost assumptions
• •pushes for tooling before DFM review

None of these signs automatically disqualify a supplier, but they increase buyer risk.

Use a sample order as an audit step

For a serious second-source project, a sample order should test more than part shape. It should test communication, engineering discipline, and evidence delivery.

A useful sample package includes:

• •quotation with separated assumptions
• •DFM notes before tooling or sample production
• •sample inspection report
• •material or alloy evidence
• •photos of casting and machined features
• •packaging evidence
• •list of open issues before production release

If the supplier cannot handle a disciplined sample order, production qualification will be harder.

Bohua second-source RFQ path

Bohua supports second-source RFQs for aluminum casting and casting plus machining projects where buyers need a clear scope review before quotation. Start with the second-source supplier page, compare assumptions through the China casting supplier comparison guide, or send a drawing package through request quote. If the project involves moving an existing mold, review the existing tool transfer checklist before shipping tooling.

FAQ

Should a second-source supplier use the same casting process as the current supplier?

Not always. If the buyer must keep the same drawing and approval path, matching the current process may reduce risk. If the current process is the problem, the second source should explain an alternative process and the design or validation changes required.

Can I audit a casting supplier without visiting the factory?

Yes for an early screen. A desk audit using RFQ evidence, inspection-report examples, process questions, and sample-order discipline can eliminate weak options. A factory visit may still be useful before production release or tooling transfer.

What is the biggest hidden risk in second-source casting quotes?

Incomplete scope. Tooling fixtures, machining fixtures, leak testing, CMM reports, heat treatment, packaging, and export assumptions are often handled differently by different suppliers. A cheaper quote may simply include less.

What should I send Bohua for a second-source review?

Send the 2D drawing, STEP file, current material and process, annual volume, target reason for second sourcing, current quality or delivery pain points if shareable, and required inspection evidence. Sensitive supplier names are not needed for the first technical review.