Precision CNC Factory Service Guide

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  Key takeaways
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  How to read a precision CNC factory service guide claim by claim
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  Tolerance: what a precision CNC factory service guide should prove
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  Lead time: separating quote speed from ship speed
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  MOQ, certification, and confidentiality in a precision CNC factory service guide
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  Machining envelope, materials, and finishes
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  Surface finish and quoting: what to specify up front
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  How to run the five checks on any supplier

A tolerance number on a website means little until you know which machine produced it and how it was measured. At GreatLight we quote ±0.005 mm (±0.0002 in) as a working limit, and we only accept that limit on features we can reach with the right spindle and fixturing. A deep bore in a 316L block and a flat face on a 6061 plate are not the same problem.

The practical question is which machine class your feature needs. We run 16 simultaneous 5-axis machining centers, 12 four-axis mills, 27 three-axis machines, and 16 mill-turn centers across 127 high-precision CNC machines. A part with compound angles and a single setup usually goes to 5-axis. A shaft with a cross hole and a thread often goes to mill-turn instead.

Inspection closes the loop. We inspect 100% of parts before shipment and can supply reports on request. Raw material is checked on arrival, dimensions are monitored in process, and the final check runs before packing. If your drawing calls for a specific report format, say so at quoting stage so the inspection plan is written for it.

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  Ask for the machine class5-axis, mill-turn, or 3-axis changes the price and the achievable geometry.
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  Name the critical featureOne or two dimensions drive the whole setup decision.
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  Confirm the report typeFirst article, full dimensional, or key-dimension only.

Most delays on CNC parts do not happen at the spindle. They happen before the first cut, while a shop waits for a missing dimension or an ambiguous tolerance. Our quoting step returns a quotation and a free DFM analysis within 12 hours, and production can start within 24 hours once the drawing is frozen and material is confirmed.

Parts ship in 3–5 days on that basis. The phrase matters: on that basis. If a feature needs a custom fixture, a special insert, or a surface finish that goes out to a plating line, the calendar moves. We would rather tell you that at quoting than after the PO.

Late delivery across our history sits below 2%. That number comes from scheduling discipline, not from promising everything to everyone. When you compare suppliers, ask where their buffer sits. A shop with slack in the schedule can absorb a fixture problem. A shop booked to the hour cannot.

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  Freeze the drawing firstEvery revision after cutting restarts the setup clock.
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  Flag finishing earlyAnodizing, plating, and black oxide add outside-process time.
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  Ask about material stockIn-stock 6061 and 304 behave differently from a mill order on 17-4PH.

There is no minimum order quantity at GreatLight. You can run one prototype, a bridge batch of fifty, and a 10,000+ part production run on the same process. That matters most at the prototype stage, when a design change is cheaper than a tooling commitment. It also means the first article and the production article come off comparable machines.

Certifications are a filter, not a badge. We hold ISO 9001:2015, IATF 16949:2016, ISO 13485:2016, and ISO 27001:2022. If your program is automotive, IATF 16949 is usually the entry condition. For medical devices, ISO 13485 is the one your quality team will ask about. ISO 27001 covers how we handle your data, which matters when drawings leave your network.

Confidentiality is a process question. Uploads are secure and confidential, and an NDA is available on request. For defense-adjacent or unreleased consumer products, agree on the file handling path before you send the STEP file, not after.

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  No MOQOne prototype to 10,000+ part runs.
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  Match the standard to the sectorIATF 16949 for automotive, ISO 13485 for medical.
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  NDA before filesSign first, upload second.

A supplier's size range decides whether your part is routine or a special job. Our maximum processing size is 4,000 mm, with a large travel of 4,000 × 400 × 150 mm, medium travels of 750 × 1,150 × 550 mm and 600 × 600 × 600 mm, and compact travels of 500 × 500 × 450 mm and 500 × 310 × 200 mm. A Ø400 mm rotary table handles round parts that need indexing.

Material choice should follow the drawing, not the shop's comfort. We machine aluminium grades 6061, 6061-T6, 2024, 5052, 5083, 6063, 6082, 7075, and ADC12; stainless 303, 304, 316, 316L, 420, 430, 431, 440C, and 17-4PH (SUS630); steels 1018, 1045, 4130, 4140, 4340, A36, and tool steel; copper and brass including C101, C103, C110, beryllium copper, C27400, C28000, and C36000; titanium TA1, TA2, TC4 (Ti-6Al-4V), Inconel, and magnesium AZ31B / AZ91D; plus plastics ABS, PC, PMMA, POM, PA, PEEK, PP, HDPE, and carbon fibre.

Finishing changes the final tolerance, so plan it in. We offer anodizing in clear, colour, hardcoat, and conductive types; electroless nickel, zinc, silver, and gold plating; powder coating and black oxide; bead blasting, tumbling, brushing, and polishing; and laser marking with a minimum character height of 1.5 mm. A hardcoat anodize on a ±0.005 mm bore needs a pre-plate allowance, and that allowance belongs in the quoting conversation.

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  Size firstConfirm the part fits the travel before discussing price.
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  One material family per quoteMixing titanium and aluminium in one RFQ hides the real cost driver.
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  Finish affects dimensionCoating thickness eats into tolerances on tight features.

Surface finish is where drawings and reality drift apart. We work to Ra 0.2–0.8 μm for fine finishes, Ra 0.8–1.6 μm as a high standard, and Ra 1.6–3.2 μm as-machined. Calling out Ra 0.4 μm on an internal pocket that no tool can reach is a common mistake. Specify the finish on the faces that touch something, and leave the rest as-machined.

A quote is only comparable when it covers the same scope. Ask whether material, machining, finishing, inspection, and packaging are all inside the number. A low unit price that excludes anodizing and a CMM report is not a lower price, it is a partial one.

Send the 3D model, the 2D drawing with datums and tolerances, the material grade, the finish callouts, and the quantity you actually plan to order. That package gets a real number. A STEP file alone gets an estimate that will move.

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  Finish only what mattersFunctional faces first, cosmetic faces second.
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  Compare full scopeMaterial, machining, finishing, inspection, packaging.
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  State the real quantityOne, fifty, and 10,000 price differently on setup alone.