Singapore CNC Processing Service: A Buyer's Checklist

• 1
  What matters before you send an RFQ
• 2
  What to compare across suppliers
• 3
  Tolerance: what the number really covers
• 4
  Material range and what it tells you about a shop
• 5
  Certifications: scope matters more than the logo
• 6
  MOQ, lead time, and how quotes are priced
• 7
  Five red flags in a supplier response
• 8
  How to run the supplier comparison

A supplier quoting ±0.005 mm is not promising that every feature on your drawing lands inside that band. The number applies to specific features, usually bores, mating faces, and datums that the machine can reach in one setup. Long bores, thin floors, and features cut on the back side of a part after a re-fixture behave differently. Ask which features the tolerance covers, and ask what happens to the rest.

Wall thickness matters more than most drawings admit. A 0.8 mm aluminum wall on a 100 mm part will deflect under normal finishing passes. The shop can still hold the nominal dimension, but flatness and parallelism drift. If those callouts are critical, say so in the RFQ and expect a different fixturing plan, sometimes a sacrificial support or a soft-jaw setup.

Surface finish and tolerance pull against each other. A Ra 0.2–0.8 μm finish needs slower feeds and lighter depths of cut, which adds cycle time. On the same part, an as-machined Ra 1.6–3.2 μm finish is cheaper and often good enough for brackets and housings. Specify the finish only on the faces that need it.

For parts that must hold ±0.0002 in, plan a finishing pass after stress relief on the raw stock. Aluminum 7075 and 17-4PH stainless both move after heavy roughing. A shop that skips stress relief will hit the tolerance on the first article and lose it on part 40.

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  Name the featuresList the bores, datums, and faces that carry the tight tolerance, not the whole drawing.
• 2
  Flag thin walls earlyAnything under 1 mm on a part over 50 mm long needs a fixturing conversation before quoting.
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  Separate cosmetic from functional finishesRa 0.2–0.8 μm on sealing faces, Ra 1.6–3.2 μm everywhere else.

Material lists are a rough proxy for capability, but a long list is not the same as experience. Aluminum 6061 and 7075, stainless 303 and 304, and brass C36000 are everyday work for most shops. Titanium TC4 (Ti-6Al-4V), Inconel, and 17-4PH stainless are different: they work-harden, generate heat, and wear tooling faster. A shop that runs them regularly will have the right inserts and coolant strategy already.

Plastics separate shops too. POM and ABS machine cleanly. PEEK and carbon fibre need sharp tooling and controlled feed rates or they delaminate and chip. If your part is a PEEK seal or a carbon fibre bracket, ask what feed and speed range the shop uses. A vague answer is a warning.

Material certification is a separate question from machining capability. For medical and aerospace parts, you need the mill certificate traceable to the heat number, not just a statement that the material is 316L. Ask whether the cert travels with the parts and whether it is included in the quote or billed separately.

One practical check: ask the shop to quote the same part in two materials and explain the price gap. A shop that understands its own cost structure will point to cycle time, tool wear, and stock price. A shop that guesses will give you two numbers with no reasoning.

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  Everyday vs. specialist6061, 304, and C36000 are routine. TC4, Inconel, and PEEK are not.
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  TraceabilityFor regulated parts, require mill certs tied to the heat number.
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  Ask for the reasoningA supplier who can explain a price gap understands the job.

A certificate on a website tells you the quality system was audited. It does not tell you which jobs run under it. ISO 9001:2015 covers a general quality management system. IATF 16949:2016 is the automotive standard and brings tighter change control and traceability. ISO 13485:2016 is the medical device standard and adds design and process validation expectations. ISO 27001:2022 covers information security, which matters if you are sending proprietary CAD files across borders.

The useful question is not whether a supplier holds a certificate but whether your part will be produced under that scope. Ask for the certificate number, the issuing body, and the expiry date. Then ask which contract you will sign and which quality clauses apply. For a bracket, ISO 9001 is usually enough. For a surgical instrument component or an EV battery contact, it is not.

Information security deserves its own line in the RFQ. If your drawings include a new product that has not launched, you want an NDA and a defined file handling process. Ask where files are stored, who can open them, and how long they are retained after the order closes. A supplier with ISO 27001:2022 has already built those controls.

Do not accept a photo of a certificate as the answer. Ask for the number and verify it with the issuing body. This takes ten minutes and removes the most common sourcing risk.

• 1
  Match the standard to the industryGeneral machining: ISO 9001:2015. Automotive: IATF 16949:2016. Medical: ISO 13485:2016.
• 2
  Verify the numberCheck the certificate with the issuing body, not just the supplier's PDF.
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  Cover file securityNDA plus a defined retention policy for pre-launch drawings.

Order size is where a Singapore CNC processing service either fits your program or does not. Some shops set a minimum that rules out prototypes. Others quote one part and a 10,000-part run with the same unit price, which usually means the setup cost is buried in the larger quantity. A clear quote shows the setup, the material, the machining cycle, and the finishing as separate lines.

Lead time has three parts: quote, production start, and shipping. A supplier that returns a quotation and DFM analysis within 12 hours and can start production within 24 hours is set up for fast turns. Parts shipping in 3–5 days is a normal range for simple geometries. Complex five-axis work with finishing and inspection adds time, and a supplier who claims otherwise is either quoting air freight or guessing.

Price is not the only number to compare. Compare what is included. Does the quote cover material certification, first-article inspection, surface finishing, and packaging? A low unit price with separate charges for every add-on is harder to manage than a slightly higher all-in number. Ask for a breakdown before you award the job.

Finally, ask about the historical late-delivery rate. A supplier tracking below 2% late deliveries is running a controlled schedule. A supplier who cannot answer the question is not measuring it.

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  Line-item the quoteSetup, material, machining, finishing, and inspection should each be visible.
• 2
  Split the lead timeQuote time, production start, and shipping are three different promises.
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  Check inclusionsCertification, first-article report, finishing, and packaging.

The first red flag is a quote with no DFM comments. Any part with tight tolerance, thin walls, or deep pockets has at least one manufacturability question. A supplier who returns a price without a single note is either not reading the file or not telling you what they found. Either way, the risk lands on you.

The second is a tolerance claim with no feature list. If the answer is a single number covering the whole drawing, the supplier has not thought about which features the machine can actually hold. Expect the out-of-tolerance features to appear at first article.

The third is a missing inspection plan. Ask what is measured, on what equipment, and what report you receive. 100% inspection before shipment is a process; a dimensional report is a document. They are not the same thing, and you should know which one you are buying.

The fourth is unclear file handling. If the supplier cannot describe where your CAD files are stored and who can access them, treat the job as public. The fifth is a schedule with no milestones. A delivery date with no first-article date and no finishing date gives you nothing to manage against.

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  No DFM notesA price without manufacturability feedback is a price without engineering review.
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  One tolerance for everythingTolerance applies to features, not to a whole drawing.
• 3
  No inspection planAsk what is measured and what document you receive.
• 4
  Vague file handlingIf access is undefined, assume the drawings are not protected.