Georgia CNC Milling Services: What to Check Before You Order

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  Key takeaways
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  What to check against your part
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  Match machine travel and axis count to the part, not the brand
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  Read tolerance claims as a range, not a headline
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  Check material stock before you design around it
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  MOQ, certifications and quote turnaround
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  How to qualify a supplier in six steps

A quotation is only useful if the shop can physically hold your part. Start with the envelope. GreatLight runs 4,000 × 400 × 150 mm on the large travel machines, plus 750 × 1,150 × 550 mm and 600 × 600 × 600 mm on medium frames. Long extrusion profiles, weldment bases and long manifold blocks fit the first group. Small brackets and housings fit the compact group at 500 × 500 × 450 mm or 500 × 310 × 200 mm.

Axis count matters when a feature sits on a face you cannot reach without re-fixturing. A part with ports on four sides, or an angled boss off a curved surface, is a 5-axis job. GreatLight has 16 simultaneous 5-axis machining centers, 12 four-axis mills and 27 three-axis machines. Three-axis work is not a downgrade. If your part is a flat plate with a few drilled holes, a 3-axis machine with a good vise is faster and cheaper.

The rotary table size is the limit people forget. A Ø400 mm rotary table sets the practical maximum for parts that need continuous rotation. Anything larger has to be positioned and indexed, which adds setups and adds stack-up error to any feature tied to two different orientations.

One more check: how many setups the quote assumes. Two setups on a tight part can double your tolerance budget. Ask the shop to name the datum and the number of operations before you approve the process.

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  4,000 mm classLong profiles, base plates and weldments, one setup where possible.
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  750–1,150 mm classHousings, engine and motor parts, medium fixtures.
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  500 mm classBrackets, connectors, small medical and electronic parts.
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  Ø400 mm rotaryThe ceiling for continuous 4-axis and 5-axis rotation.

A ±0.005 mm capability figure is a shop-wide best case, not a promise on every line of your drawing. It depends on material, feature size, tool reach and how the part is held. On aluminium 6061 and 7075 the number is reachable on bores and faces with a rigid setup. On Inconel or a thin-wall titanium housing, the same feature may move twice that much from cutting forces and heat.

Surface finish follows the same logic. Ra 0.2–0.8 μm is a fine finish that usually needs a separate finishing pass or a smaller stepover. Ra 0.8–1.6 μm is the common working range for mating seals and bearing bores. Ra 1.6–3.2 μm is as-machined and fine for brackets and covers. If a drawing calls for Ra 0.4 μm on a deep pocket, expect a longer cycle and a higher price.

Where buyers get caught is calling out tolerance on a non-critical feature. A ±0.01 mm callout on a clearance hole adds inspection time and sometimes a second operation for no functional reason. Mark the features that matter. Let the rest run to general tolerance.

Ask how the shop verifies. GreatLight inspects 100% of parts before shipment, with a raw material check, in-process monitoring and a final inspection, and reports on request. That last part is the one to confirm. A report that names the instrument and the measured values is worth more than a stamp.

Material availability decides lead time more often than machine time. Aluminium 6061, 6061-T6, 2024, 5052, 5083, 6063, 6082, 7075 and ADC12 cover most housings and brackets. Stainless 303, 304, 316, 316L, 420, 430, 431, 440C and 17-4PH cover food, medical and marine parts. Steel grades 1018, 1045, 4130, 4140, 4340, A36 and tool steel handle shafts and structural parts.

Specialty alloys change the plan. Titanium TA1, TA2 and TC4 (Ti-6Al-4V), Inconel and magnesium AZ31B or AZ91D cut slower, need different tooling and sometimes need a stress relief step. If your part is Inconel, do not compare quotes on price alone. Compare the cycle time and the tool wear allowance the shop built in.

Plastics are a separate conversation. ABS, PC, PMMA, POM, PA, PEEK, PP, HDPE and carbon fibre all machine differently. PEEK and carbon fibre need sharp tooling and dust control. POM machines clean and holds tolerance well.

Finishing can be the longest queue in the chain. Anodizing in clear, colour, hardcoat or conductive, electroless nickel, zinc, silver and gold plating, powder coating, black oxide, bead blasting, tumbling, brushing and polishing are all available here. Laser marking and engraving has a minimum character height of 1.5 mm, so keep your part marks readable at that size.

Minimum order quantity is the check that kills prototype projects. GreatLight has no minimum order quantity, so a single piece and a 10,000+ part run go through the same quoting process. That matters when you need one machined sample to test a fit before committing to a production run.

Certifications should be matched to your industry. ISO 9001:2015 covers general quality management. IATF 16949:2016 is the one automotive and EV buyers look for. ISO 13485:2016 applies to medical devices. ISO 27001:2022 covers information security, which matters when your drawings are confidential. Ask for the scope statement, not just the certificate number.

On timing, the quote and a free DFM analysis come back within 12 hours. Production can start within 24 hours after approval. Parts ship in 3–5 days for standard work. Historical late-delivery probability is below 2%. Treat those as planning inputs, not guarantees, and confirm the dates on your specific part.

Confidentiality is part of the commercial package. Uploads are secure and confidential, and an NDA is available on request. If your program has a disclosure requirement, sort that out before you send the STEP file, not after.