CNC Machining Service Exporter: How to Vet One Before You Send a PO

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  Key takeaways
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  Seven checks, and what counts as proof
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  Which supplier profile fits your program
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  What a CNC machining service exporter actually does
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  Machine mix and the size envelope you can actually get
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  Tolerance, surface finish and the metrology behind them
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  Certifications and confidentiality for regulated work
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  Materials, finishes and what happens after machining
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  Step by step: how to run the supplier check

An exporter is not a broker. The useful definition is simple: the company holds the machines, quotes your drawings, machines the parts and handles export paperwork under its own name. If a website shows lathes and grinders but the quote comes back from a third party, you are dealing with a middleman, and your tolerance and delivery promises are only as good as the shop behind them.

The practical question is who owns the spindle. GreatLight runs 127 high-precision CNC machines across three wholly-owned plants in Dongguan plus a Singapore factory, with 150 technicians and 7,600 m² of floor space. That configuration matters because export work mixes low-volume prototypes with production runs, and the same plant has to do both without changing suppliers halfway.

Export also adds constraints that a domestic shop never sees: packing for sea or air freight, material certificates for customs, surface finishes that survive humidity, and document sets that match the invoice. Ask who prepares those documents. A real exporter answers in one reply, with names and formats.

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  Owns the machinesSpindle list, travels and control models can be shared.
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  Quotes from the drawingDFM feedback arrives with the price, not after.
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  Handles export documentsPacking list, material certs and inspection reports.

Most RFQs fail on geometry, not on price. A part with undercuts, deep pockets on five faces or a rotary feature needs either multiple setups or a machine that reaches it in one. Multiple setups multiply fixture error, so the tolerance you can hold drops quickly. That is why the machine list is the first thing to read.

Ask for three numbers: how many simultaneous 5-axis centers, how many mill-turn centers, and the largest travel. At GreatLight those are 16 simultaneous 5-axis machining centers, 16 mill-turn centers, 12 four-axis mills and 27 three-axis machines, with a maximum processing size of 4,000 mm and a Ø400 mm rotary table for round work.

Small parts deserve the same attention. Compact travels of 500 × 500 × 450 mm and 500 × 310 × 200 mm are often where tight-tolerance work runs, because thermal growth over a long axis is easier to control on a short one. If your part is 30 mm across with a ±0.005 mm bore, a large gantry is the wrong machine.

When the geometry is simple and flat, three-axis milling is cheaper and faster. Save the 5-axis centers for parts that need them, and say so in the RFQ. A supplier that quotes everything on the most expensive machine is not reading your drawing.

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  Large work4,000 × 400 × 150 mm travel for long extrusions and frames.
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  Medium work750 × 1,150 × 550 mm and 600 × 600 × 600 mm.
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  Round workØ400 mm rotary table for mill-turn parts.

A tolerance claim is only useful if it is repeatable across a batch. ±0.005 mm (±0.0002 in) is achievable on a rigid setup with the right tooling, but it depends on material, wall thickness and how many setups the part needs. Ask what the shop holds on a typical aluminium bracket versus a hardened steel insert; the answers should differ.

Surface finish follows the same logic. As-machined aluminium usually lands at Ra 1.6–3.2 μm. A finishing pass gets Ra 0.8–1.6 μm, and fine work reaches Ra 0.2–0.8 μm. If your drawing calls for Ra 0.4 μm on a deep pocket, expect a separate operation and a longer cycle, not a tweak to the feed rate.

Then ask how it is measured. A coordinate measuring machine, optical comparator and surface tester in-house mean the data comes back with the parts. GreatLight inspects 100% of parts before shipment, checks raw material on receipt, monitors in process and issues final reports on request, with a qualification rate of 99.99%.

One caution: do not specify a tolerance tighter than the function needs. Every extra decimal adds cost and inspection time, and on a 200 mm aluminium plate it may be unmeasurable in a stable way. Mark the two or three critical dimensions and leave the rest general.

Certificates are the objective part of supplier selection. Four matter for export machining: ISO 9001:2015 for general quality systems, IATF 16949:2016 for automotive and EV programs, ISO 13485:2016 for medical devices, and ISO 27001:2022 for information security. Each one implies audits and records, which is why they carry weight.

Read the scope, not the logo. The certificate should name the legal entity that will appear on your PO and cover the site where your parts are made. If the certificate belongs to a group holding company and your parts run in a different plant, ask which procedures apply on that floor and who signs the inspection report.

Confidentiality is a separate track. Drawings, CAD files and production volumes are commercially sensitive, and ISO 27001 addresses how they are stored and accessed. For defense, medical or unreleased consumer products, ask for an NDA before you upload. GreatLight signs an NDA on request and treats uploads as secure and confidential.

For medical and automotive work, add one more question: how are changes handled? A documented engineering change process, with re-validation of the first article, is what keeps a certified system honest after the first shipment.

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  ISO 9001:2015Baseline quality management for general industrial parts.
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  IATF 16949:2016Automotive and EV programs with PPAP-style records.
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  ISO 13485:2016Medical devices, traceability and process validation.
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  ISO 27001:2022Information security for drawings and customer data.

A machining quote covers more than the cut. Material grade, heat treatment, finish and marking decide whether the part works in service. Ask for the grade list and compare it to your drawing. Common aluminium grades are 6061, 6061-T6, 2024, 5052, 5083, 6063, 6082 and 7075, with ADC12 for castings.

Stainless work usually means 303, 304, 316, 316L, 420, 430, 431, 440C or 17-4PH (SUS630). Steels run from 1018 and 1045 through 4130, 4140, 4340 and A36 to tool steel. Copper and brass cover C101, C103, C110, beryllium copper, C27400, C28000 and C36000. Titanium and special alloys include TA1, TA2, TC4 (Ti-6Al-4V), Inconel and magnesium AZ31B / AZ91D. Plastics range from ABS and PC to POM, PA, PEEK, PP, HDPE and carbon fibre.

Finishing is where lead time quietly grows. Anodizing in clear, colour, hardcoat or conductive; electroless nickel, zinc, silver and gold plating; powder coating and black oxide; bead blasting, tumbling, brushing and polishing; laser marking and engraving with a minimum character height of 1.5 mm. Each step is a separate supplier or line, so ask which ones are in-house.

Marking deserves a note. If your part number is small, 1.5 mm is the floor for readable laser engraving. Below that, the mark may not survive anodizing or plating. Move the mark to a flat face and give it room.

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  Match the grade6061-T6 and 7075 behave differently on the same setup.
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  Plan the finish earlyHardcoat anodizing changes dimensions by a few micrometres.
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  Check mark size1.5 mm minimum character height for laser marking.