CNC Processing Services: OEM Projects
This guide is for engineers and sourcing managers choosing a machining partner for production parts. It covers the checks that decide whether a shop can hold your print, hit your schedule and stay compliant.
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Key takeaways for CNC processing services OEM projects
What to compare across CNC processing services OEM projects
Use this table to score two or three shops on the same line items.
| Check | Minimum acceptable | Red flag |
|---|---|---|
| Tolerance capability | ±0.005 mm on critical features | No stated tolerance, only 'tight' |
| Surface finish | Ra 0.8–1.6 μm as standard | No Ra value on the quote |
| Certifications | ISO 9001:2015 plus industry-specific | Certificate expired or not named |
| MOQ | One prototype to 10,000+ part runs | Fixed high MOQ on first run |
| Quote turnaround | Quotation and DFM analysis in 12 hours | Quote only after a phone call |
| Inspection | 100% inspection before shipment | Sampling only, no report |
| Confidentiality | NDA available on request | No NDA, uploads not secured |
| Max part size | Up to 4,000 mm where required | Size limit not disclosed |
Pick the shop that can prove the tolerance, not the one that promises it
Send your drawing and we will return a quote with DFM analysis in 12 hours, with the process class and inspection plan stated.
Matching the right CNC process to your OEM part
Most OEM calls start with a drawing and a target price. The first question is not price. It is which machine can cut the geometry without extra setups. A part with undercuts, deep pockets on five faces, or blended contours usually needs simultaneous 5-axis work. A flat bracket with holes on two faces does not, and paying 5-axis rates for it wastes money.
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 matters because we can quote the cheapest process that still holds the print, instead of forcing every job onto one platform.
Part size drives the decision as much as geometry. Travel on the large machines reaches 4,000 × 400 × 150 mm. Medium platforms cover 750 × 1,150 × 550 mm and 600 × 600 × 600 mm. Compact cells handle 500 × 500 × 450 mm and 500 × 310 × 200 mm, plus a Ø400 mm rotary table for round and indexed work.
A practical rule for OEM projects: if a feature can be reached in one setup on a 3-axis machine, keep it there. If two or more setups would be needed and the datum chain is long, move the job to 4-axis or 5-axis. Fewer setups means fewer datum shifts, and datum shifts are where most tolerance stack-up errors come from.
- 13-axisPrismatic plates, covers, simple housings with features on one face.
- 24-axisShafts, connectors and parts with features indexed around an axis.
- 35-axisImpellers, turbine blades, complex housings, blended contoured surfaces.
- 4Mill-turnParts that combine turning and milling, cut in one chucking.
Tolerance, finish and material questions that decide the shop
A shop that quotes ±0.005 mm on every feature is either very expensive or not being honest. That tolerance is achievable, and we hold it on critical features, but it requires the right machine, a stable setup and temperature control. General features can often run at ±0.05 mm and cost far less.
Surface finish follows the same logic. As-machined parts sit around Ra 1.6–3.2 μm. A standard fine finish lands at Ra 0.8–1.6 μm. Optical, sealing and bearing surfaces may need Ra 0.2–0.8 μm, which usually means a finishing pass with a smaller stepover or a secondary operation. Tell us which surfaces matter rather than calling out the whole part.
Material choice should be settled before quoting, not after. We machine aluminium grades such as 6061-T6, 7075 and 2024, stainless including 303, 316L, 17-4PH and 440C, alloy steels like 4140 and 4340, copper and brass grades, titanium TA1 to TC4, Inconel, magnesium, and engineering plastics from POM and PEEK to carbon fibre.
Hard materials change the cost picture more than any other variable. Inconel and 17-4PH in the hardened state cut slowly, wear tooling and need conservative feeds. Aluminium 6061-T6 cuts fast and holds tolerance easily. If the design allows a softer alloy, say so on the RFQ and the quote will reflect it.
Certifications and inspection for OEM production parts
Certification is a filter, not a selling point. If your end product goes into a vehicle, the shop needs IATF 16949:2016. Medical devices point to ISO 13485:2016. Where customer drawings and CAD data are sensitive, ISO 27001:2022 covers information security. A general quality system such as ISO 9001:2015 is the baseline for everything else.
GreatLight holds ISO 9001:2015, IATF 16949:2016, ISO 13485:2016 and ISO 27001:2022. That combination lets one supplier serve automotive, medical, electronics and industrial machinery programs without re-auditing the same factory for each product line.
Inspection practice separates serious shops from the rest. We check raw material on arrival, monitor in-process dimensions, and inspect 100% of parts before shipment, with reports on request. Ask any supplier whether inspection is sampling or full, and ask what happens to a non-conforming lot.
The qualification rate we work to is 99.99%. That number is only meaningful alongside a documented inspection plan. A shop with no measurement records cannot back up a quality claim, no matter how good the machines are.
Lead time, MOQ and quoting on OEM programs
Lead time is where most OEM schedules break. A realistic flow looks like this: quotation and free DFM analysis within 12 hours, production start within 24 hours of approval, and parts shipping in 3–5 days. Those windows depend on material availability and part complexity, so confirm them in writing on the PO.
Ask about the supplier's late-delivery history rather than their best case. Our historical late-delivery probability is below 2%. That figure comes from planning jobs around real machine capacity, not from promising every job in 48 hours.
MOQ is a common trap. Some shops quote a low unit price but require a high first-run quantity, which locks up cash before the design is proven. We set no minimum order quantity, so the same process can run one prototype or a 10,000+ part production batch. It also means the prototype and the production parts come off comparable setups.
Confidentiality belongs in the commercial checklist too. Uploads are handled as secure and confidential, and an NDA is available on request. If your drawings cannot be shared under those terms, the quote process stalls before it starts.
Step by step: vetting a supplier for CNC processing services OEM projects
Run these steps in order. Skipping step 3 is the most common cause of rework later.
- 1Send a 2D print and 3D model with the RFQInclude material, quantity and any finish callout. A model alone leaves datum and tolerance intent open to interpretation.
- 2Mark critical features, not the whole drawingFlag only the dimensions that affect function. This lets the shop quote ±0.005 mm where it matters and general tolerances elsewhere.
- 3Request a DFM analysis with the quoteLook for thin walls, deep pockets, sharp internal corners and features that need a special cutter. We supply this free within 12 hours.
- 4Confirm the process and machine classAsk whether the part will run on 3-axis, 4-axis, 5-axis or mill-turn, and which of those setups holds the tightest callout.
- 5Check certification relevanceMatch the certificate to your industry: IATF 16949:2016, ISO 13485:2016, ISO 27001:2022 or ISO 9001:2015.
- 6Agree on inspection and reportingState whether you need dimensional reports, material certificates or first-article inspection, and who pays for them.
- 7Settle MOQ, lead time and NDA before the POPut quantity bands, the 3–5 day shipping window and confidentiality terms in writing so nothing shifts after tooling starts.
Questions engineers ask about OEM machining projects
What does CNC processing for OEM projects actually cover?
It means machining parts that go into a product sold under your brand, to your drawing and revision level. The shop acts as a manufacturing extension of your engineering team.
When is 5-axis not worth the extra cost?
When the part can be reached in one setup on a 3-axis machine and no feature needs simultaneous motion. Flat plates, simple covers and two-face brackets usually fall into this group.
How tight a tolerance should I call out?
Only as tight as the function requires. ±0.005 mm on bearing bores or mating faces is reasonable. Applying it to clearance holes and cosmetic edges raises cost with no benefit.
What materials can be machined for OEM parts?
Aluminium 6061-T6, 7075, 2024 and 6082; stainless 303, 304, 316L, 17-4PH and 440C; steels 1018, 4140 and 4340; copper and brass grades; titanium TC4; Inconel; magnesium; and plastics such as POM, PEEK and ABS.
How do you handle drawings that cannot be shared openly?
Uploads are treated as secure and confidential. An NDA is available on request, so drawings can be reviewed before any quote work starts.
Can the same shop run one prototype and a large production batch?
Yes. With no minimum order quantity, the first unit and a 10,000+ part run can be quoted on the same process family, which keeps the transition from prototype to production predictable.
Start your next OEM machining project
Upload a print and model for a quotation, a DFM review and a clear process recommendation for CNC processing services OEM projects.
12-hour quote100% inspectionNDA on request
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