Affordable CNC Factory: Highest Budget Draft Choice

The highest budget in a draft plan usually means the most capability you can buy before cost stops making sense. That is a technical question, not a shopping one. Start with the largest envelope the part needs, then the tightest tolerance, then the material. A 200 mm aluminum bracket with a ±0.1 mm callout and a 400 mm stainless housing with a ±0.01 mm bore do not belong in the same purchase.

Desktop and benchtop mills handle soft material well when the part is small and the tolerance is open. Brass, thin aluminum, and copper cut fine on an entry machine, but feed rates stay low and tool wear shows up early. Anything past a few hundred dollars of tooling per week, or any part that needs a true position under ±0.05 mm, belongs on a production machine.

A factory with 127 high-precision CNC machines can absorb the jobs a benchtop cannot. The relevant question is which of those machines your part should sit on, because machine time is the line item that moves the quote most.

Hard steel and stainless are the usual break point. They need rigidity, coolant, and a spindle with enough torque to avoid rubbing. If your part is 17-4PH or 4140 above 40 HRC, plan for an industrial machine from the first article, not the third.

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  Small and open toleranceBenchtop mill is workable for prototypes in aluminum or brass.
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  Tight tolerance or hard materialMove to a production mill before the first article.
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  Long partsPlan around the 4,000 mm maximum processing size.
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  Complex anglesCheck whether a 5-axis setup removes a second op.

Tolerance drives cost more than material in most quotes. A band of ±0.1 mm needs one setup and a standard vise. A band of ±0.02 mm needs a controlled process, sharp tooling, and a probe check. At ±0.005 mm, the shop has to hold temperature, use the right fixture, and inspect the feature on a CMM rather than a caliper.

Ask what the tolerance applies to. A general block tolerance on a drawing is not the same as a bore-to-bore center distance. Center distances stack, and they are the features engineers usually care about on mating parts. Tell the shop which dimensions are functional and which are reference. That single note often removes a grinding operation.

Surface finish sits in the same budget column. As-machined at Ra 1.6–3.2 μm is fine for brackets and covers. Sealing faces and bearing bores usually want Ra 0.8–1.6 μm. Optical and fluid-contact surfaces can call for Ra 0.2–0.8 μm, which means a finishing pass and sometimes a separate polish.

One practical rule: pick the coarsest tolerance and finish that still lets the assembly work. Tightening a callout that no one measures adds cost with no benefit.

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  ±0.1 mmGeneral machining, single setup, standard workholding.
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  ±0.02 mmControlled process plus in-process probing.
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  ±0.005 mmClimate control, dedicated fixture, CMM report.
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  Ra 0.8–1.6 μmAdds a finishing pass on most faces.

Aluminum 6061-T6 is the default for affordable parts. It cuts fast, holds tolerance, and takes anodizing well. 7075 costs more and machines slower, so use it only where strength justifies the step. ADC12 die casting is a different route entirely and makes sense above a few thousand parts.

Stainless 303 is the free-machining grade and the cheapest stainless to run. 304 and 316L are tougher, and 316L shows up in medical and marine work. 17-4PH can be machined in the annealed state and aged afterward, but that adds a heat-treat step and a second inspection.

Titanium and Inconel are where an affordable quote stops being cheap. TC4 (Ti-6Al-4V) needs low cutting speeds and sharp tooling. Inconel wears tools fast and often needs a roughing strategy that leaves stock for a finishing pass. Budget the tooling, not just the cycle time.

Plastics are the opposite case. POM and PA cut quickly and hold good tolerance. PEEK is expensive per kilogram and needs care to avoid burning. Carbon fibre eats tool edges, so plan on more tool changes.

Send the material spec with the drawing. A shop that quotes 6061 when your drawing says 7075 will look cheaper, and the difference will show up at the first inspection.

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  6061-T6Default choice for structural aluminum parts.
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  303 stainlessCheapest stainless grade to machine.
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  17-4PHAdds a heat-treat and inspection step.
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  PEEKHigh cost per kg, needs careful feeds.

Setup is a fixed cost. A one-off prototype and a 500-part run use the same fixture, the same program, and the same first-article inspection. That is why the per-part price drops fast between one and fifty, then flattens. If you can combine two similar parts into one run, do it.

No minimum order quantity matters most at the prototype stage. Being able to order one part, test it, and then order 200 without a new supplier saves weeks of re-qualification. GreatLight runs from one prototype to 10,000+ part runs on the same floor.

Finishing is a second setup and often a second supplier. Anodizing, plating, powder coating, and laser marking each add handling and lead time. Group finishes where you can. Laser marking needs a minimum character height of 1.5 mm, so leave space in the drawing.

Inspection is not optional on tight parts. Raw material check, in-process monitoring, and final inspection are the normal flow. Ask for reports when a feature is functional. A 99.99% qualification rate is only meaningful if the measurement matches your drawing.

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  Setup is fixedOne-off and 500-part runs share the same fixture cost.
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  No MOQOrder one part, then scale without a new supplier.
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  Finishes add handlingBatch parts to avoid repeat shipping.
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  Laser markingMinimum character height 1.5 mm.

A benchtop mill is not a bad machine. It is a bad fit for certain work. If the part needs simultaneous 5-axis motion, if the material is stainless or titanium, or if the tolerance is tighter than ±0.02 mm across several features, the desktop route will cost more in rework than it saves.

The same applies to surface finish. A benchtop spindle at high speed chatters on deep pockets, and chatter shows in the finish. If the part is visible or seals against another surface, that matters.

Quantity is the other trigger. Fifty parts on a benchtop is a week of operator time. On a production mill it is a day. The crossover point is usually somewhere between five and twenty parts, depending on complexity.

There is a middle path. Keep the benchtop for quick iterations and send the final geometry to a factory for the production run. You get fast feedback and a qualified part, without buying a machine you will outgrow.

GreatLight has three wholly-owned plants covering 7,600 m², with 16 simultaneous 5-axis centers, 12 four-axis mills, 27 three-axis machines, and 16 mill-turn centers. That mix is what lets a quote go out in 12 hours and production start within 24.

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  Switch at 5–20 partsOperator time on a benchtop stops paying off.
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  Switch on hard materialStainless and titanium need rigidity and coolant.
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  Switch on finishChatter on deep pockets shows in the surface.
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  Hybrid routeIterate on the desktop, produce at the factory.