Aldershot CNC Processing Service: What to Check Before You Order

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  Key takeaways
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  Six checks for an Aldershot CNC processing service
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  Check 1: Can the shop actually hold your tolerance?
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  Check 2: What the lead time actually covers
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  Check 3: MOQ, certificates, and the paperwork trail
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  Check 4: Material range and finishing under one roof
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  Check 5: When a shop is the wrong fit
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  How to vet an Aldershot CNC processing service

Tolerance is the first filter. A shop can quote ±0.005 mm, but the number only means something when it is tied to a machine and a setup. On a 3-axis mill, a tight tolerance on three faces usually means three setups, three fixtures, and three chances to lose the datum. On a simultaneous 5-axis center, the same part often comes off in one setup, so the stack-up stays smaller.

Ask which machine will run your part. GreatLight holds ±0.005 mm (±0.0002 in) on 16 simultaneous 5-axis machining centers, 12 four-axis mills, and 16 mill-turn centers. Maximum processing size is 4,000 mm, with a Ø400 mm rotary table for round parts. If your part is 600 × 600 × 600 mm, that fits the medium travel envelope; a 4,000 × 400 × 150 mm part needs the large frame.

Geometry matters as much as the number. Deep pockets, thin walls, and intersecting bores are where tolerance claims fall apart. A wall under 0.8 mm will deflect under normal cutting force, so the shop has to reduce radial engagement and take more passes. If a supplier does not ask about wall thickness, they have not read the drawing.

Surface finish is the second half of the tolerance story. As-machined aluminum sits around Ra 1.6–3.2 μm. A sealing face or bearing bore usually needs Ra 0.8–1.6 μm, and optical or medical contact surfaces go to Ra 0.2–0.8 μm. Finish is set by tool choice, stepover, and spindle speed, not by a polishing step bolted on at the end.

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  Send the 3D model and the 2D drawingThe drawing controls datums, the model controls form.
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  Flag thin walls under 1 mmThey change the cutting strategy and the fixture.
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  Name the critical dimensionsMost drawings have 3 to 8 features that actually matter.

Most lead-time disputes come from a mismatch in definitions. A supplier quoting five days may mean five days after tooling, after material arrival, or after DFM sign-off. Ask when the clock starts. At GreatLight, quotation and free DFM analysis come back within 12 hours, production can start within 24 hours, and parts ship in 3–5 days. Historical late-delivery probability is below 2%.

The DFM step is where lead time is really won or lost. A machinist who reviews the model before quoting will spot a corner radius that needs a 3 mm cutter instead of a 6 mm one, or a thread that cannot be cut without a second setup. Catching that at quote stage costs a day. Catching it after the first article costs a week.

Material availability drives more delays than machine time. 6061-T6 and 304 stainless are usually on the shelf. 17-4PH, Ti-6Al-4V, and Inconel often are not. If your part uses a specialty alloy, ask whether the shop stocks it or orders per job, and add that to your schedule.

For production programs, ask about capacity, not just the first order. A shop with 127 high-precision CNC machines across three plants can absorb a 10,000-part release without pushing your prototype to the back of the queue. A small job shop cannot.

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  Pin the start pointQuote, DFM sign-off, material in-house, or first chip?
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  Ask about specialty alloys earlyInconel and titanium add procurement time.
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  Split prototype and productionRun one part, then release the batch.

MOQ is the easiest check and the one buyers forget. If a supplier will not run one piece, you cannot validate the process before you commit to a batch. GreatLight has no minimum order quantity, from one prototype to 10,000+ part runs, using the same inspection routine on both.

Certification only matters when it matches your program. ISO 9001:2015 is the baseline quality system. IATF 16949:2016 applies to automotive and EV work. ISO 13485:2016 applies to medical devices. ISO 27001:2022 covers information security, which matters if you are sending CAD files under NDA. A supplier holding all four can serve several programs without a quality-system gap.

Confidentiality is a real selection criterion for defense, medical, and automotive buyers. Ask how files are stored and who can open them. Uploads are secure and confidential, and an NDA is available on request. If a supplier hesitates on an NDA, treat that as an answer.

The inspection record is the last check. Ask what happens before shipment: raw material check, in-process monitoring, and final inspection. 100% inspection before shipment, with reports on request, is the standard you want. A 99.99% qualification rate is only credible if the paperwork behind it is available.

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  Match the certificate to the sectorISO 9001 alone will not clear an automotive PPAP.
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  Request mill certs with the partsThey tie the alloy back to the heat number.
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  Get the inspection report on the first articleIt shows what the shop measures and how.

A shop that machines your part but cannot finish it adds a week of shipping and a second quality risk. Finishing is where tolerances move. Anodizing adds 5–25 μm per surface depending on the process, which changes a press fit. Hardcoat anodizing adds more. Electroless nickel and zinc plating also shift dimensions unless the shop masks or compensates.

Ask about the full chain. GreatLight runs anodizing in clear, colour, hardcoat and conductive versions, electroless nickel, zinc, silver and gold plating, powder coating, black oxide, bead blasting, tumbling, brushing and polishing, plus laser marking and engraving with a minimum character height of 1.5 mm.

Material range tells you whether the shop fits your program. Aluminum covers 6061, 6061-T6, 2024, 5052, 5083, 6063, 6082, 7075 and ADC12. Stainless covers 303, 304, 316, 316L, 420, 430, 431, 440C and 17-4PH. Steel covers 1018, 1045, 4130, 4140, 4340, A36 and tool steel. Titanium and specialty alloys include TA1, TA2, TC4, Inconel, and magnesium AZ31B / AZ91D.

Plastics are often an afterthought. ABS, PC, PMMA, POM, PA, PEEK, PP, HDPE and carbon fibre all behave differently. PEEK needs sharp tooling and low cutting temperature; carbon fibre wears tools fast and needs dust control. If a supplier lists plastics without a process note, they may be treating them like aluminum.

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  Ask about finish thicknessAnodizing and plating move fits by micrometers.
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  Confirm masking on critical boresThreads and bearing seats need protection.
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  Check plastic experience separatelyPEEK and carbon fibre are not aluminum.

A good supplier will tell you when your part does not belong on a CNC. If the geometry is a thin shell with no functional surfaces, sheet metal fabrication or vacuum casting will cost less. If the part is a one-off with no tolerance callouts, 3D printing may be enough. Pushing those onto a 5-axis center wastes money.

Watch for the opposite problem too. A shop that quotes a 1,200 mm long part with a ±0.02 mm flatness callout on a 3-axis machine is making a promise the setup cannot keep. Long parts need the large travel frame and often a temperature-stable environment. Ask how the machine handles thermal drift over a long cycle.

Distance matters less than it used to, but it is not zero. Aldershot buyers working with a Dongguan or Singapore plant should plan for freight and customs in the schedule. GreatLight runs three wholly-owned plants, 7,600 m² of floor space, and 150 technicians, with a Singapore factory at No.3 Joo Koon Circle, Singapore 629032. That gives a shorter route for some UK programs than a China-only supplier.

The clearest signal of fit is whether the supplier pushes back. If every question gets a yes with no comment on geometry, material, or finish, the quote is not grounded in a process plan. A supplier who flags two risks on page one is cheaper in the end.

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  Wrong fit: thin shellsSheet metal or vacuum casting is cheaper.
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  Wrong fit: long parts on small framesThermal drift breaks flatness callouts.
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  Good signal: they push backA grounded quote names the risks.