Wholesale Price Prototype CNC Machining: A 7-Point Buyer Guide

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  Key takeaways
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  What separates a low quote from a real wholesale price
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  Why a wholesale price is not the same as a low price
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  Tolerance and surface finish you can actually inspect
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  Machine selection and what it does to your unit price
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  Lead time, order quantity, and certification fit
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  Material and finishing choices that move the price
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  Seven steps to place a prototype order that holds its price

A low number on a prototype order usually means something was left out. The three common omissions are setup time, finishing, and inspection. If the quote covers only spindle time, the missing work reappears later as a second invoice or as parts that fail at assembly.

A wholesale price is different. It comes from a shop that already owns the machines, the finishing line, and the metrology lab, so nothing is subcontracted at retail rates. At GreatLight, 127 high-precision CNC machines and in-house surface finishing sit in the same 7,600 m² plant in Dongguan. That is the structural reason a wholesale number can be lower than a broker’s and still cover inspection.

Ask one question early: what is excluded. Laser marking, anodizing, bead blasting, and certificates are the usual exclusions. Get them listed in writing. A quote you can compare line by line beats a quote that is 20 percent cheaper and undefined.

Do not read this as a rule that cheap is bad. Some prototype parts genuinely need only three-axis milling and an as-machined finish. The point is to know which route you bought, so the price difference has a reason you can name.

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  Spindle time is not the whole costSetup, fixturing, and inspection are real minutes on real machines.
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  In-house finishing removes a margin layerAnodizing and plating done on site avoid outside vendor markup.
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  List exclusions in the quoteMarking, certificates, and special packaging are the usual ones.

A tolerance claim is only useful if the shop can measure it. ±0.005 mm is about ±0.0002 in, which needs a temperature-stable room and a calibrated CMM or optical comparator, not a caliper on a bench. Ask what instrument will verify the tightest dimension on your drawing.

Surface finish matters more than most prototype buyers expect. A sealing face at Ra 3.2 μm may leak, while Ra 0.8–1.6 μm holds. For optical and fluid-handling parts, Ra 0.2–0.8 μm is reachable but adds polishing time and cost. Put the finish callout only where the function needs it, not on the whole part.

Geometric tolerances deserve the same treatment. Flatness and perpendicularity drive cost faster than linear dimensions because they force extra setups or a grinding step. If a datum is not functional, loosen it. Engineers who mark every face as critical pay for inspections that never change the outcome.

One practical test: send a drawing with a single tight feature and a loose rest, and see whether the shop asks which one matters. A shop that asks is reading the print. A shop that quotes without asking is guessing at the process.

Three-axis machining is the cheapest route for prismatic parts with features on one or two faces. Add a deep cavity, an undercut, or a 45° port on the side, and the part needs repositioning. Every reposition is a new setup, a new fixture, and a new chance to lose position.

Four-axis and 5-axis centers cut that away. GreatLight runs 16 simultaneous 5-axis machining centers and 12 four-axis mills. A 5-axis machine reaches five faces in one setup, which usually beats three-axis machining on total cost once a part has more than three faces. The hourly rate is higher. The number of hours is lower.

Size decides the rest. The largest travel here is 4,000 × 400 × 150 mm for long parts, with 750 × 1,150 × 550 mm and 600 × 600 × 600 mm cells for mid-size work. A Ø400 mm rotary table handles round and indexed parts. If your part fits a 500 × 500 × 450 mm envelope, it can run on compact machines, which keeps the rate down.

Mill-turn centers matter for shafts and housings that need turning and milling in one cycle. Splitting those operations across two machines doubles the workholding error. For a prototype with a bearing bore and cross-drilled holes, one mill-turn cycle is usually the better buy.

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  Count the facesThree or more machined faces usually favor 4-axis or 5-axis.
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  Check the envelopeParts under 500 × 500 × 450 mm run on lower-rate machines.
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  Shaft plus cross holesMill-turn keeps concentricity in one setup.

Prototype programs fail on calendar time more than on unit price. A quotation and free DFM analysis within 12 hours, production start within 24 hours, and parts shipping in 3–5 days change how many design iterations fit in a quarter. If a supplier quotes six weeks, the second iteration slips into the next budget cycle.

Order quantity is the other gate. No minimum order quantity means the same process runs at one piece and at 10,000+ pieces. That matters because a prototype made on a different route than production teaches you the wrong lessons about tolerance and cost.

Certifications should match your industry, not your ego. ISO 9001:2015 covers general quality systems. IATF 16949:2016 is what automotive and EV programs ask for. ISO 13485:2016 applies to medical devices. ISO 27001:2022 covers information security, which is the one customers notice when drawings are sensitive.

Confidentiality belongs in the same conversation. Uploads are secure and confidential, and an NDA is available on request. For unreleased products, sign the agreement before the first STEP file moves. It costs a day and removes a recurring argument.

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  12-hour quote turnaroundDFM feedback arrives with the number, not after it.
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  One piece or 10,000+No minimum order quantity keeps prototype and production on one route.
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  Pick the standard your buyer auditsAutomotive, medical, and IT security each map to a different certificate.

Aluminium 6061-T6 is the default for prototypes: easy to cut, stable, and cheap to anodize. Switch to 7075 or 17-4PH stainless and the cutting time climbs, because the tool wears faster and speeds drop. Titanium TC4 (Ti-6Al-4V) and Inconel sit at the top of the range and are worth it only when the service condition demands them.

Plastics behave differently. POM and ABS machine cleanly at high removal rates. PEEK holds tolerance at temperature but costs far more per kilogram and needs sharp tooling to avoid melting. Carbon fibre and glass-filled grades eat cutters, so expect shorter tool life built into the price.

Finishing is where quotes diverge most. Anodizing in clear, colour, hardcoat, or conductive versions, plus electroless nickel, zinc, silver, and gold plating, are all in-house at GreatLight. Powder coating and black oxide cover the rougher industrial look. Bead blasting, tumbling, brushing, and polishing sit before those steps.

Laser marking closes the loop. Minimum character height is 1.5 mm, so a 0.8 mm part number will not reproduce. If traceability matters, size the marking area on the drawing rather than in a revision note.

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  Start with 6061-T6Fast cutting and predictable anodizing for most prototypes.
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  Hard alloys cost time, not just material7075, 17-4PH, TC4, and Inconel slow the spindle.
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  Size your laser marking1.5 mm minimum character height on the finished surface.