A procurement manager wires a 50 percent deposit to a supplier found on a B2B marketplace. The photos showed a clean CNC shop floor with rows of 5-axis machines. Six weeks later, the parts arrive with visible tool marks, out-of-spec tolerances, and a delivery date two weeks late. The company that took the deposit was a trading firm with no machining equipment of its own. The photos belonged to a factory three provinces away that had never heard of the order.

This exact scenario, or a variation of it, happens to procurement teams every month. It is entirely preventable. China remains the largest and most cost-competitive source of precision CNC machining in the world, and the overwhelming majority of Chinese manufacturers are legitimate, capable, and reliable. The failures that do occur trace almost universally to skipped due diligence, not to some inherent unreliability in Chinese manufacturing. CNC machining vs injection molding vs 3D printing

This guide gives you a 10-point due diligence checklist that separates real manufacturers from trading companies, verifies quality capability before you commit, and protects your intellectual property and payment before the first shipment leaves the factory. Work through all ten points before signing a purchase order with any new supplier.

The 10-Point Due Diligence Checklist

1. Verify the Business License Shows Manufacturing, Not Trading

Every legitimate Chinese company operates under a registered business license that specifies its approved business scope. A genuine manufacturer’s license includes the Chinese characters for manufacturing (制造) in its business scope. A trading company, which buys from factories and resells with a markup and no direct quality control, typically lists sales or import and export (销售 or 进出口) in its scope instead. Request the business license and confirm the scope directly, or verify it independently through China’s National Enterprise Credit Information Publicity System, which is publicly searchable. A supplier unwilling to share this basic registration document is an immediate red flag.

2. Confirm Quality Certifications Match Your Industry Requirement

ISO 9001 is the baseline quality management certification that any serious CNC manufacturer should hold. Beyond that baseline, industry-specific certifications matter significantly: AS9100 for aerospace components, IATF 16949 for automotive parts, and ISO 13485 for medical devices. These are not optional paperwork. They represent documented quality management systems with specific requirements for traceability, process control, and corrective action that general ISO 9001 does not mandate. Request the actual certificate, verify the certification body is accredited, and confirm the certificate has not expired. A supplier claiming AS9100 compliance without a valid certificate from an accredited registrar cannot support aerospace program requirements regardless of their actual machining capability.

3. Request a Video Audit or Third-Party Factory Inspection

Photos on a supplier website or trade platform profile prove nothing about the actual factory behind them. A video audit, a live video call where the supplier walks through their actual shop floor, CMM inspection lab, and material stock in real time, is now standard practice and any legitimate manufacturer will accommodate this request without hesitation. For larger commitments, a third-party inspection service (SGS, TUV, Bureau Veritas, or a dedicated sourcing agent) can conduct a physical factory audit and provide an independent report on equipment, capacity, and quality systems. Reluctance to provide either a video audit or accept a third-party inspection is one of the strongest indicators that the supplier is not what their marketing represents.

4. Match Equipment and Tolerance Capability to Your Specific Part

A supplier that produces simple brackets on 3-axis mills cannot fulfill an order requiring 5-axis machining of complex titanium aerospace components, regardless of what their capability statement claims. Request specific machine models, axis configuration, spindle specifications, and documented tolerance capability, ideally supported by recent CMM inspection reports on parts similar to yours. If your part requires tolerances of 0.01mm or tighter, ask specifically how the supplier verifies and holds that tolerance in production, not just on a single sample part. A capability mismatch discovered after tooling or a production run is committed is far more costly than confirming capability during supplier qualification.

5. Confirm DFM Engineering Support Is Part of Their Process

Manufacturers who implement digital DFM (Design for Manufacturability) review before production catch dimensional and process issues before they become scrap, rework, or missed deadlines. Ask directly whether DFM review is a standard part of their quoting process, what specific checks they perform (wall thickness, tolerance feasibility, fixturing strategy, material shrinkage), and request a sample DFM report from a past project. Manufacturers without a DFM for injection molding process are significantly more likely to produce parts that technically match the drawing but fail to account for real production variables, particularly on complex or first-time production runs.

6. Verify Quality Control and Inspection Documentation Practices

Ask specifically what inspection equipment the factory uses (CMM, optical comparator, surface roughness tester, hardness tester) and at what stage of production inspection occurs: incoming material verification, in-process checks, and final inspection before shipment. Request a sample inspection report from a comparable past project, and confirm whether First Article Inspection (FAI) reports are provided as standard practice or only on request. For parts destined for regulated industries, ask whether the inspection reports include full dimensional traceability to the drawing, not just a general pass or fail statement. Suppliers who cannot produce a detailed sample inspection report on request typically do not have a documented quality system behind their claims.

7. Establish a Clear Sample and First Article Approval Process

Before any production quantity is committed, a formal sample or first article approval step should confirm the supplier can actually produce your part to specification. This means receiving physical samples (not just photos) of the first parts produced, along with a dimensional inspection report mapped to your drawing, and explicit written sign-off before the full production quantity proceeds. Skipping this step to save one to two weeks of lead time is the single most common cause of large-scale quality disputes, because problems that would have been caught in a 10-piece sample run instead surface across an entire production batch.

8. Protect Intellectual Property With an NDA and Manufacturing Agreement

A signed NDA (Non-Disclosure Agreement) before sharing detailed CAD files and drawings is standard practice and any legitimate manufacturer will sign one without resistance. For higher-value or proprietary designs, a more comprehensive NDNR (Non-Disclosure, Non-Use, Non-Circumvention) agreement, enforceable under Chinese law and drafted by counsel familiar with Chinese IP enforcement, provides stronger protection than a standard Western-style NDA that may not be enforceable in a Chinese court. Confirm the agreement specifically addresses ownership of tooling, molds, and fixtures built for your program, since ambiguity here has caused disputes when companies attempted to switch suppliers and found the incumbent supplier claiming ownership of tooling paid for by the buyer.

9. Structure Payment Terms to Protect Both Parties

Common payment structures for new supplier relationships include 30 percent deposit with 70 percent balance paid against pre-shipment inspection results, or the use of a trade assurance or escrow service offered by major B2B sourcing platforms that holds payment until the buyer confirms goods received match specification. Wiring a large deposit, or full payment, to a new, unverified supplier with no trade assurance protection and no third-party inspection checkpoint is the payment structure most associated with fraud losses. As the relationship matures and trust is established through multiple successful orders, payment terms can reasonably shift toward standard net-30 or net-60 commercial terms.

10. Evaluate Communication, Project Management, and Language Capability

A dedicated English-speaking project engineer or account manager who understands technical drawings, GD&T notation, and can discuss DFM findings in specific technical terms, rather than a general sales contact who relays messages to an engineering team, is a strong signal of a supplier built to serve international customers professionally. Test this during the quoting stage: send a drawing with a deliberately ambiguous tolerance callout or an unusual feature, and evaluate whether the supplier asks an informed clarifying question or simply quotes the part as drawn without engaging with the ambiguity. Suppliers who ask good questions during quoting communicate well during production, when questions matter far more.

Which Certifications Actually Matter for Your Industry?

Not every certification is relevant to every part. Requesting the wrong certificate wastes time during supplier qualification, and missing the right one creates real compliance risk once parts are in your supply chain. The table below maps the certifications that matter to the industry and application they actually govern. Medical device CNC machining

Trading Company vs Real Manufacturer: How to Tell the Difference

Many suppliers found through B2B marketplaces and search results are trading companies rather than factories. Trading companies are not inherently dishonest, but they add a markup, remove your direct visibility into quality control, and introduce a communication layer between you and the actual production process. The table below highlights the practical differences to check for.

Related Elite Mold Tech Guides and Sources

Related guides: complete manufacturing process selector guide, rapid prototyping process explained, Services d'usinage CNC.

Authoritative references: ISO 9001 quality management standard, Society of Manufacturing Engineers (SME).

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Questions fréquemment posées

How do I verify a Chinese CNC manufacturer’s business license is genuine?

China’s National Enterprise Credit Information Publicity System (国家企业信用信息公示系统) is a free, publicly searchable government database where any registered Chinese company’s business license, registered capital, business scope, and legal representative can be verified directly. Search using the company’s registered Chinese name, which the supplier should provide alongside their English trading name. Confirm that the business scope includes manufacturing-related terms rather than exclusively sales or trading terms, that the company status shows as active rather than revoked or under investigation, and that the registered address is consistent with the location the supplier claims for their factory. This verification takes fifteen minutes and eliminates a significant percentage of fraudulent or misrepresented suppliers before any money changes hands.

What certifications should I require depending on my industry?

Certification requirements scale with the regulatory and safety criticality of your application. For general industrial and commercial parts, ISO 9001 quality management certification is the appropriate baseline requirement. For aerospace components, AS9100 (which builds on ISO 9001 with aerospace-specific traceability and configuration management requirements) should be considered non-negotiable, particularly for any part entering a certified aircraft supply chain. For automotive parts, IATF 16949 demonstrates the process control and defect-prevention systems that automotive OEMs and Tier 1 suppliers require. For medical devices, ISO 13485 is essential and demonstrates the manufacturer has documented processes for traceability, risk management, and design control appropriate to medical device manufacturing. Requesting a certificate without checking its validity is not sufficient. Confirm the certifying body is accredited (look for IAF-recognized accreditation) and that the certificate scope specifically covers CNC machining, not just general company operations.

What is the safest payment structure for a first order with a new Chinese supplier?

For a first order with an unverified supplier, the safest structure combines a modest deposit (commonly 30 percent) with the balance held until pre-shipment inspection confirms the goods match specification, either through your own representative, a third-party inspection service, or the trade assurance mechanism offered by major B2B sourcing platforms such as Alibaba. Avoid wiring a large deposit or full payment via bank transfer to a supplier with no independent verification, particularly if the supplier pressures for full payment upfront or offers an unusually large discount for doing so. As trust builds through successive successful orders with consistent quality and delivery performance, payment terms can reasonably relax toward standard net-30 or net-60 commercial terms common in established buyer-supplier relationships. The safest approach for the first two to three orders is always to keep leverage on your side until the supplier has demonstrated reliable performance.

How do I protect my product design when working with a Chinese CNC manufacturer?

Protection starts with a properly drafted NDA or, for higher-value designs, an NDNR (Non-Disclosure, Non-Use, Non-Circumvention) agreement written in Chinese, governed by Chinese law, and enforceable in a Chinese court, since a standard Western-style NDA drafted under US or UK law frequently has limited practical enforceability against a Chinese entity. Beyond the legal agreement, practical steps include limiting the technical detail shared with any single supplier during the RFQ stage to only what is needed for an accurate quote, splitting critical proprietary sub-assemblies across multiple suppliers when the design allows it, and registering key design patents in China specifically, since patent protection is jurisdictional and a patent registered only in your home country provides no enforcement mechanism against a Chinese manufacturer operating within China. For tooling and molds built specifically for your program, ensure the manufacturing agreement explicitly states that you own the tooling outright, since ambiguity on this point has caused disputes when buyers attempted to move production to a new supplier.

How can I tell if a supplier found on Alibaba or a similar platform is a real factory?

B2B sourcing platforms host both genuine factories and trading companies, and platform verification badges (such as “Verified Supplier” or “Gold Supplier” designations) confirm certain baseline checks but do not guarantee the supplier is a direct manufacturer with the equipment shown in their profile photos. The most reliable verification methods are requesting a live video audit of the actual shop floor, cross-referencing the factory address shown on the platform against the address on the business license verified through the National Enterprise Credit Information Publicity System, and asking specific technical questions about machine models, spindle specifications, and tolerance capability that a trading company representative typically cannot answer with the same specificity as an actual production engineer. Reviews and platform transaction history provide some signal but can be inflated or unrepresentative of quality on complex parts, since many reviews concern simple, low-tolerance products that do not test the same capabilities your part requires.

What is the difference between requesting a sample and requiring first article inspection?

A sample is simply a physical part produced by the supplier for your review, which may or may not include formal dimensional documentation. First Article Inspection (FAI), by contrast, is a formal, documented process, often following the AS9102 standard in aerospace contexts, where every dimension and characteristic on the engineering drawing is measured and recorded in a structured report, providing objective evidence that the supplier’s process can produce the part to specification before production quantities are committed. For low-risk, low-complexity parts, a visual sample review may be adequate. For any part with tight tolerances, critical features, or destined for a regulated industry, a formal FAI report mapped directly to your drawing dimensions should be a mandatory step before authorizing full production, since it provides a documented baseline you can hold the supplier accountable to if quality issues emerge later in the production run.

About the Author:
Alex Morgan specializes in technical content for precision manufacturing, with a focus on CNC machining, injection molding, die casting, 3D printing, sheet metal fabrication, and custom mold manufacturing. With more than a decade of experience in B2B manufacturing content and SEO, he creates technically accurate content designed for engineers, product developers, procurement teams, and manufacturing decision-makers. His work helps global manufacturers clearly communicate complex production capabilities, material options, tolerances, tooling processes, and quality standards to customers across the US, Europe, and Asia-Pacific. He writes for manufacturing companies where technical expertise, precision, and reliability matter.