CNC Machining Services Dublin: A Sourcing Checklist

• 1
  Key takeaways
• 2
  How to match part and supplier before you ask for a price
• 3
  What Dublin buyers should ask before sending drawings
• 4
  Tolerance, surface finish, and the limits of each process
• 5
  Lead time, MOQ, and what a fast quote really tells you
• 6
  Certifications and compliance by sector
• 7
  Finishing, inspection, and total landed cost
• 8
  Step by step: how to run a CNC machining RFQ

Most RFQs fail for the same reason: the drawing says ±0.01 mm but the supplier quotes a 3-axis machine. The part ships, the CMM report shows 0.018 mm on one bore, and the argument starts. Fix this before the quote, not after. Tell the supplier which dimensions are functional and which are reference. That single distinction changes the process plan and often the price.

Ask what machine will run the job. A shop with 16 simultaneous 5-axis centers, 12 four-axis mills, 27 three-axis machines, and 16 mill-turn centers can route your part to the right spindle instead of forcing it onto the nearest one. A shop with four machines cannot. Capacity is not a marketing number here; it decides whether your ±0.005 mm callout is realistic.

Get the inspection plan in writing. First article with a CMM report, in-process checks at defined intervals, and a final dimensional report on request. If a supplier only offers a certificate and no measurement data, you are buying a promise, not a part.

• 1
  Mark functional dimensionsBores, mating faces, and datums that drive assembly.
• 2
  Name the processAsk for 5-axis, mill-turn, or 3-axis in the quote document.
• 3
  Request measurement dataA CMM report beats a certificate for your own quality file.

A ±0.005 mm tolerance is achievable, but not on every feature. It holds well on a bored hole in aluminium or stainless when the setup is rigid and the tool is fresh. It is much harder on a thin wall, a long cantilever, or a deep pocket where tool deflection and thermal growth take over. Expect the supplier to push back on those features, and treat that pushback as a good sign.

Surface finish follows the same logic. As-machined aluminium sits around Ra 1.6–3.2 μm. A good finishing pass gets you to Ra 0.8–1.6 μm. Below that, you are usually looking at Ra 0.2–0.8 μm, which means slower feed, smaller stepover, or a secondary operation. Ask which features actually need the fine finish. Polishing a whole part to Ra 0.4 μm when one sealing face needs it is money spent for nothing.

Material choice moves the target too. 6061-T6 and 7075 cut cleanly and hold tight tolerances. 316L stainless work-hardens, so light passes and constant feed matter. Titanium TC4 and Inconel need rigid setups and sharp tooling, and they will eat your cycle time. A supplier who quotes the same lead time for 7075 and Inconel has not looked at your part.

• 1
  Tight tolerance, simple geometryStraightforward on 3-axis or 4-axis with a rigid fixture.
• 2
  Tight tolerance, thin wallsExpect stress relief, light passes, and a longer cycle.
• 3
  Fine finishBudgets Ra 0.2–0.8 μm only where the function needs it.

Lead time is a capacity signal. A supplier that returns a quotation and a free DFM analysis within 12 hours is telling you two things: someone read the drawing, and the machine schedule has room. Production can start within 24 hours on a released job, and parts ship in 3–5 days on standard work. Those numbers come from the shop floor, so treat them as a benchmark when you compare suppliers.

MOQ is where small Dublin teams get squeezed. Many local shops will not touch a single prototype because setup cost dominates. A supplier with no minimum order quantity can run one part and then the same process for a 10,000+ part run, which removes the awkward second sourcing step at pilot stage. Ask directly: what is your minimum, and does the prototype process match the production process?

Beware of the cheapest quote with no DFM note. If a supplier never flags a problem, they either did not review the model or they plan to sort it out in production. Both cost you time. A DFM comment about tool access, wall thickness, or an unrealistic tolerance is a feature, not an obstacle.

• 1
  12-hour quoteShows review happened and machine time is open.
• 2
  No MOQSame process from one prototype to 10,000+ parts.
• 3
  DFM feedbackA flagged risk early is cheaper than a rework later.

Certification only matters when it matches your sector. ISO 9001:2015 is the baseline for general industrial work. IATF 16949:2016 is what automotive and EV buyers look for, and it carries the PPAP and traceability expectations that come with it. ISO 13485:2016 is the medical device standard, covering process validation, cleanliness, and document control. ISO 27001:2022 applies to information security, which matters when you are uploading proprietary CAD files.

Check scope, not just the certificate number. A supplier can hold ISO 13485 for one process and not for another. Ask which plant and which process line the certificate covers, and whether your part will run there. If the certificate lives at a different site, your part is not covered.

For Dublin medtech and aerospace teams, material traceability is the other half. Ask for mill certificates matched to the heat number, and for a cleaning or passivation step if the part touches patients or fuel systems. GreatLight holds ISO 9001:2015, IATF 16949:2016, ISO 13485:2016, and ISO 27001:2022 across its manufacturing operations.

• 1
  IndustrialISO 9001:2015 is the entry requirement.
• 2
  Automotive and EVIATF 16949:2016 plus a PPAP path.
• 3
  Medical devicesISO 13485:2016 and validated cleaning steps.
• 4
  Data securityISO 27001:2022 for CAD and IP handling.

Finishing is where quotes drift apart. Anodizing, electroless nickel, zinc, silver and gold plating, powder coating, black oxide, bead blasting, tumbling, brushing, and polishing are all standard, but each adds a queue and a handling step. Laser marking is quick, though the minimum character height is 1.5 mm, so fine serial numbers need another method. Group finishes together to avoid paying for three separate trips.

Inspection should be built into the price, not sold as an extra. GreatLight runs raw material checks, in-process monitoring, and a final inspection on 100% of parts before shipment, with reports on request. The qualification rate sits at 99.99%. Those numbers matter most on a 10,000+ part run, where a 0.01% escape still means a conversation with your customer.

Add up the full cost, not the unit price. Freight, duty, packing, rework risk, and the engineering hours you spend chasing status updates all count. A quote that is 20% higher but arrives with a CMM report and no rework is usually the cheaper option. Historical late-delivery probability below 2% is the kind of figure worth asking about in a first call.

• 1
  Bundle finishesOne trip instead of three saves handling and time.
• 2
  Inspection included100% final check before shipment, reports on request.
• 3
  Total landed costUnit price plus freight, rework, and admin time.