CNC Machining by Product Manufacturers

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  Key takeaways
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  Which machining route fits your part
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  What CNC machining by product manufacturers actually covers
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  Tolerance and surface finish: what to specify and when to stop
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  Lead time, order quantity, and how quotes are built
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  Certifications, inspection, and confidentiality
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  Materials and finishes that change the process
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  Seven checks before you place a machining order

A product manufacturer takes your CAD file, a material spec, and a finish callout, and returns parts that drop into your assembly. That sounds simple until the part has a deep pocket, a thin wall, or a bore that must stay concentric to a datum. Those features decide whether the job runs on a 3-axis mill with two setups or a 5-axis center in one.

At GreatLight we run 127 high-precision CNC machines across three wholly-owned plants, 7,600 m² in total, with 150 technicians. Sixteen of those are simultaneous 5-axis machining centers, twelve are 4-axis mills, twenty-seven are 3-axis, and sixteen are mill-turn centers. The mix matters because a supplier with only 3-axis machines will quote you a different process than one that can tilt the tool.

The maximum processing size is 4,000 mm, with travel up to 4,000 × 400 × 150 mm on the large machines and 750 × 1,150 × 550 mm on the medium frame. If your part is a long extrusion bracket or a large housing, that envelope is the first thing to check. If it is a small connector body, the Ø400 mm rotary table and the compact 500 × 500 × 450 mm envelope are what keep the price sane.

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  Machines, not catalog pagesAsk for the axis count and travel on the machine that will run your part.
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  One setup beats threeFewer setups means fewer datum shifts and tighter true position.
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  Material availability drives the schedule6061 and 304 are routine; Inconel and Ti-6Al-4V need a heads-up.

Our standard machining tolerance is ±0.005 mm, or ±0.0002 in. That is a real number on rigid setups and short tool reaches. It is not a blanket promise across a 300 mm part with a 12:1 bore. When a drawing calls for a tight tolerance on a feature the tool cannot reach without a long, thin cutter, deflection eats the tolerance before the operator touches the offset.

Surface finish follows the same logic. As-machined finish lands at Ra 1.6–3.2 μm. A high finish is Ra 0.8–1.6 μm, and a fine finish is Ra 0.2–0.8 μm. Each step up costs time, sometimes a second operation, and often a different cutter. If a sealing face needs Ra 0.4 μm, say so on the drawing. If a bracket face just needs to look clean, Ra 3.2 μm is fine and cheaper.

A common mistake is applying one tolerance block to the whole drawing. That forces the shop to inspect every dimension to the tightest value, which slows the job and inflates the price without improving function. Tighten only the features that mate, seal, or locate. Leave the rest at general tolerance.

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  Tight on 5% of dimensions, general on the restIt cuts inspection time and keeps the price honest.
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  Finish callouts belong on functional facesSealing surfaces, bearing bores, and sliding faces.
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  Deep bores need a reach checkAnything past 4:1 depth-to-diameter should be flagged at quote.

Quotation and free DFM analysis come back within 12 hours. Production can start within 24 hours after you approve the quote and the DFM notes. Parts ship in 3–5 days for typical jobs. Those numbers assume the material is in stock and the first article is clean. If your part needs a custom extrusion or a casting, the clock starts later and the supplier should tell you that upfront.

There is no minimum order quantity. You can order one prototype and come back for a 10,000+ part run on the same process. That matters because it lets you validate the design before committing to a production tool. A shop that insists on 500 pieces for the first order is really asking you to gamble on an unproven design.

Ask how the quote is structured. A good quote separates material, machining time, finishing, and inspection. A single lump-sum number hides where the cost sits, so you cannot tell whether a design change will save money or add it. It also makes it hard to compare two suppliers fairly.

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  12-hour quote, 24-hour startBoth depend on material availability.
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  One piece is a valid orderNo minimum order quantity, from prototype to 10,000+ parts.
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  Line-item quotes compare betterMaterial, machining, finish, inspection.

Certifications are not decoration. They tell you which industries the shop already serves and which paperwork it can produce without a fight. GreatLight holds ISO 9001:2015, IATF 16949:2016, ISO 13485:2016, and ISO 27001:2022. The first covers general quality systems. IATF 16949 is what automotive and EV programs expect. ISO 13485 supports medical device work. ISO 27001 covers information security, which matters when your drawings are the product.

Inspection is where a cheap quote often hides its real cost. We inspect 100% of parts before shipment, covering raw material check, in-process monitoring, and final inspection. Reports are available on request. Ask any supplier what they inspect, with what equipment, and what happens when a dimension drifts mid-run. Vague answers mean you are the inspection plan.

Uploads are secure and confidential, and an NDA is available on request. For pre-launch products, that should be settled before the first file transfer, not after the first shipment. The historical late-delivery probability across our programs is below 2%, but that figure is only useful if the schedule was realistic at quote.

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  Match the certificate to the industryIATF 16949, ISO 13485, ISO 27001 each serve a different buyer.
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  Ask for the inspection planWhat is measured, how often, and on what equipment.
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  NDA before files, not after partsEspecially for unreleased consumer or medical products.

Material choice drives tooling, speed, and sometimes the machine. Aluminum grades 6061, 6061-T6, 2024, 5052, 5083, 6063, 6082, 7075, and ADC12 cover most product housings and brackets. 7075 cuts well but is less corrosion-resistant than 6061, so it usually needs anodizing. Stainless 303, 304, 316, 316L, 420, 430, 431, 440C, and 17-4PH behave differently at the spindle: 303 is free-machining, 316L work-hardens, and 17-4PH can be run in the annealed or hardened condition.

Steel grades 1018, 1045, 4130, 4140, 4340, A36, and tool steel are common for shafts, plates, and fixtures. Copper and brass C101, C103, C110, beryllium copper, C27400, C28000, and C36000 machine fast but move with heat, so coolant strategy matters. Titanium TA1, TA2, TC4 (Ti-6Al-4V), Inconel, and magnesium AZ31B / AZ91D need slower feeds and more attention to fire risk on magnesium.

Plastics include ABS, PC, PMMA, POM, PA, PEEK, PP, HDPE, and carbon fibre. PEEK and carbon fibre are abrasive and wear tools quickly, which shows up in the price. Finishing options run from anodizing (clear, colour, hardcoat, conductive) and electroless nickel, zinc, silver, and gold plating to powder coating, black oxide, bead blasting, tumbling, brushing, polishing, and laser marking with a minimum character height of 1.5 mm.

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  Pick material for function firstStrength, weight, thermal, chemical, electrical, then cost.
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  Anodizing changes dimensions slightlyCall out threads and bores that must stay in tolerance.
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  Laser marking has a size floor1.5 mm minimum character height.