Fast CNC Prototype Factory Service: How to Choose One

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  Key takeaways
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  What to compare before you order
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  What a fast CNC prototype factory service really means
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  Tolerance and finish: the numbers to agree on
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  Capacity checks: machines, size and materials
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  Certifications, documentation and confidentiality
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  Lead time, MOQ and the quote you should expect
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  Step by step: qualifying a prototype supplier

Speed in prototyping is not one number. It is the sum of quoting, programming, machining, finishing and inspection. A shop can cut metal quickly and still lose three days waiting on an anodizing line. When you evaluate a fast CNC prototype factory service, ask where the queue actually is.

Most prototype parts are small and simple enough to machine in one or two setups. The hard cases are thin walls, deep pockets, tight bores and features on five faces. Those parts need simultaneous 5-axis work or a mill-turn center, which changes both the price and the schedule.

A useful benchmark: GreatLight quotes and returns a free DFM analysis within 12 hours, and production can start within 24 hours. Parts typically ship in 3–5 days. Those numbers only hold when the drawing is complete and the material is in stock.

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  Ask for the setup countOne setup is faster and more accurate than four. If the quote hides the setup plan, ask.
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  Separate machining from finishingKnow which step adds days, especially anodizing and plating.
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  Confirm the drawing revisionMost delays come from a STEP file that does not match the 2D tolerance callouts.

General machining tolerance of ±0.005 mm (±0.0002 in) is realistic on rigid parts in aluminium, brass and stainless. It is not realistic on a 300 mm thin-wall housing, where thermal drift and tool deflection dominate. Tell the shop which features are critical and which are free.

Surface finish follows the same logic. As-machined surfaces land around Ra 1.6–3.2 μm. A high-quality finish of Ra 0.8–1.6 μm is normal for sealing faces and bearing bores. Fine finishes of Ra 0.2–0.8 μm need slower feeds, sharper tooling and often a secondary operation.

Do not put a blanket Ra 0.4 μm note on the whole drawing. It multiplies cost and cycle time for faces that will never be measured. Mark the functional surfaces and leave the rest as machined.

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  Flag critical featuresUse a datum scheme, not a general note, for bores and mating faces.
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  Watch wall thicknessUnder 1 mm in aluminium, chatter and distortion become the main risk.

Machine count matters less than machine mix. GreatLight runs 127 high-precision CNC machines, including 16 simultaneous 5-axis machining centers, 12 four-axis mills, 27 three-axis machines and 16 mill-turn centers. That mix covers prismatic parts, turned parts and angled features in one shop.

Part size sets the limit. Maximum processing size is 4,000 mm, with large travels of 4,000 × 400 × 150 mm and medium travels of 750 × 1,150 × 550 mm and 600 × 600 × 600 mm. Compact cells at 500 × 500 × 450 mm and 500 × 310 × 200 mm handle small, high-volume prototype batches.

Material availability decides whether a quote is real. Aluminium 6061, 7075 and 6082, stainless 303, 304, 316L and 17-4PH, plus titanium TC4 and PEEK are common. Exotic alloys like Inconel cut slowly and may need a longer window.

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  5-axis for angled featuresUndercuts and multi-face holes in one setup, less alignment error.
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  Mill-turn for round partsShafts and fittings with cross holes finish in fewer operations.

Certifications tell you what the quality system can support. ISO 9001:2015 covers general process control. IATF 16949:2016 adds automotive traceability and change control. ISO 13485:2016 supports medical device work. ISO 27001:2022 covers information security, which matters when you send CAD files.

Inspection is the other half. Look for 100% inspection before shipment, with raw material checks, in-process monitoring and a final inspection. Reports are available on request. Ask for the first article report on a new part, not after the third revision.

Confidentiality should be simple to arrange. Uploads are secure and confidential, and an NDA is available on request. If a supplier hesitates on an NDA for a prototype, treat that as a signal.

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  Ask for the FAIRFirst article inspection report on the first good part.
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  Match cert to industryMedical and automotive buyers need the relevant system, not just ISO 9001.

A prototype quote should state three dates: DFM feedback, production start and shipment. GreatLight returns quotation and free DFM analysis within 12 hours, can start production within 24 hours, and ships parts in 3–5 days. Historical late-delivery probability is below 2%.

Minimum order quantity is a strong signal of who the factory serves. No minimum order quantity means you can order one prototype or a 10,000+ part run without changing suppliers mid-project. That continuity saves a second qualification cycle.

Read the quote line by line. Material, machining, finishing, inspection and freight should be separate. A single lump sum hides the cost driver, and you cannot negotiate what you cannot see.

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  Get dates in writingDFM, production start and shipment, each with a date.
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  Separate the line itemsMaterial, machining, finish, inspection, freight.