Competence Driven CNC Machining Services: What to Check

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  Six things to settle before you send an RFQ
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  Competence driven cnc machining vs. a sales-front shop
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  What competence driven cnc machining means in practice
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  Tolerance, surface finish and the parts that fit each band
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  Part size, machine selection and what each platform handles
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  Certifications, inspection and confidentiality as selection criteria
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  Lead time, MOQ and how to read a quote
• 8
  How to screen a CNC supplier in six steps

Competence is not a slogan. On the shop floor it means the process is repeatable across a run, not just on the first article. A supplier that machines to ±0.005 mm and holds it on part 800 is doing something different from one that hits the number once on a warm machine and then drifts.

The practical test is simple. Ask how they hold tolerance on your specific geometry, in your specific material, on a machine that has been running all week. If the answer is a general statement about quality policy, you have learned something useful.

GreatLight runs 16 simultaneous 5-axis machining centers, 12 four-axis mills, 27 three-axis machines and 16 mill-turn centers, 127 high-precision machines in total across 3 wholly-owned plants. That mix matters because it decides which machine your job goes on, and whether it waits in a queue behind work that needs the same spindle.

Parts ship in 3–5 days on standard jobs. Production can start within 24 hours of a PO. Those numbers come from capacity, not from optimism.

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  Repeatability over peak numbersAsk for data from a full run, not a single part.
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  Machine fitThe right spindle for your part size and feature access.
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  Process ownershipDesign, machining and finishing under one roof.

Tolerance and finish are the two numbers that decide whether a quote is realistic. A general machining tolerance of ±0.005 mm covers most mating features, bearing bores and locating faces. Going tighter than that is sometimes necessary, but it changes the process, the inspection time and the price.

Surface finish is often the hidden cost. As-machined at Ra 1.6–3.2 μm is fine for brackets and internal frames. Ra 0.8–1.6 μm suits sealing faces and sliding contact. Ra 0.2–0.8 μm belongs on optical mounts, hydraulic sealing surfaces and parts where friction has to be predictable. Each step down means slower feed rates and more time on the machine.

Not every part needs the tight band. A cosmetic enclosure panel with ±0.1 mm tolerance and Ra 3.2 μm will function exactly as well as one machined to ±0.01 mm. Paying for precision the assembly cannot use is the most common overspend we see in incoming RFQs.

The same logic applies to feature size. Thin walls below 0.5 mm deflect under cutting force. Deep pockets with a depth-to-width ratio beyond 4:1 need smaller tools, longer cycle times and more tool changes. If your design has these features, the drawing tolerance and the process tolerance are no longer the same thing.

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  Fit this band to the functionMating faces and bores: ±0.005 mm to ±0.02 mm.
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  Finish follows the contactSealing and sliding surfaces need Ra 0.8 μm or better.
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  Ask about feature limitsWall thickness, pocket depth and tool reach set the real floor.

Machine travel limits decide whether your part is a routine job or a special setup. GreatLight machines up to 4,000 mm maximum processing size. The large platform covers 4,000 × 400 × 150 mm. Medium work fits 750 × 1,150 × 550 mm or 600 × 600 × 600 mm. Compact parts run on 500 × 500 × 450 mm and 500 × 310 × 200 mm platforms. A Ø400 mm rotary table handles round work that needs continuous rotation.

Size alone is not the deciding factor. Feature access matters more. A 300 mm part with five faces of work is a five-axis job even though it fits easily on a three-axis machine. Putting it on a three-axis mill means multiple fixtures, and each refixture adds position error.

Materials change the plan too. Aluminum 6061 and 7075 cut fast and hold tolerance well. Stainless 316L and 17-4PH work-harden, so feeds and speeds need to be right the first time, and the tool cannot dwell. Titanium TC4 and Inconel cut slowly and generate heat that travels into the part, which is when a roughing and finishing pass matters more than a single heavy cut.

For die-cast and vacuum-cast parts, the machining step is usually about critical features only. The casting holds the general form; the CNC operation brings bores, sealing faces and mounting holes into tolerance.

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  Large platform4,000 × 400 × 150 mm for long, slim parts.
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  Five-axis for accessMulti-face work in one setup, fewer fixtures.
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  Material-specific feedsWork-hardening grades need a rigid setup and no dwell.

Certifications are a filter, not a badge. ISO 9001:2015 covers quality management generally. IATF 16949:2016 applies to automotive and EV work and brings specific requirements on traceability and change control. ISO 13485:2016 applies to medical devices and puts more weight on process validation and records. ISO 27001:2022 covers information security, which matters when you send CAD files and drawings.

Match the certificate to your industry, then ask what the scope actually covers. A shop can hold ISO 9001 while running your job through an outside finishing vendor that is not in scope. Competence driven cnc machining services keep the process chain inside the audit boundary, which is why GreatLight runs design, machining, die casting, sheet metal, vacuum casting and finishing in-house.

Inspection is where tolerance claims become verifiable. 100% inspection before shipment, with raw material checks, in-process monitoring and a final inspection, and reports available on request. For critical features, ask for the report format before the run starts so the measurement method is agreed on both sides.

Confidentiality belongs in the same checklist. Uploads are handled as secure and confidential, and an NDA is available on request. If your drawing package is under NDA with your own customer, get the supplier under the same terms before the first file transfer.

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  Industry firstIATF for auto, ISO 13485 for medical, ISO 27001 for data.
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  Check the scopeConfirm subcontracted steps are inside the audit boundary.
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  Agree the reportFix the measurement method before production starts.

Lead time is a capacity statement, not a promise. GreatLight returns a quotation and a free DFM analysis within 12 hours, production can start within 24 hours, and parts ship in 3–5 days. Historical late-delivery probability is below 2%. When a supplier quotes 3–5 days, ask what happens to that number when a rush job lands in the same week.

There is no minimum order quantity. One prototype and a 10,000+ part run go through the same process. That is useful for two reasons. First, your first article is produced the way the production parts will be, so the prototype actually predicts the run. Second, you are not forced to buy 500 units to find out whether the design works.

Read the quote line by line. Setup, material, machining time, finishing, inspection and shipping should be separate lines. A single lump sum hides where the cost sits, and it makes it hard to compare two suppliers fairly. If one quote is much cheaper, the difference is usually in finishing, inspection or material grade, not in machining efficiency.

Free DFM analysis is the most underused part of a quote. Send the drawing and ask what would make the part cheaper to machine without changing function. A 0.3 mm corner radius instead of a sharp internal corner can remove an EDM step entirely.

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  Quote in 12 hoursIncludes a free DFM analysis, not just a price.
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  No MOQOne part to 10,000+ runs on the same process.
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  Itemized linesSetup, material, machining, finishing, inspection.