CNC aerospace parts production: what the process can and cannot hold

Most aerospace work arrives as aluminium or titanium, and the two behave nothing alike at the spindle. Aluminium 6061-T6 and 7075 cut fast and hold a sharp edge well, which makes them the default for brackets, housings, and prototype airframe fittings. Titanium Ti-6Al-4V (TC4) sits at the other end: low thermal conductivity pushes heat into the cutting edge, and the material work-hardens if the tool rubs instead of shears.

Inconel and the nickel alloys go further still. They hold strength at temperatures that would soften steel, so they get used for exhaust-side and hot-section hardware. They also wear tools quickly, which means more tool changes and longer cycle times per part. A shop that quotes Inconel at aluminium feed rates is guessing.

Stainless 17-4PH (SUS630) and 316L cover the corrosion-resistant side: fuel system bodies, valve components, and actuator parts. Copper alloys such as beryllium copper appear where electrical conductivity and wear resistance matter together. Magnesium AZ31B and AZ91D cut easily but need chip control, because fine magnesium chips ignite if they collect dry.

If you are still choosing an alloy, send the drawing and the loading conditions. We will tell you which grades we machine most often for that geometry and where a substitution would cost you strength, mass, or corrosion margin.

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  Aluminium6061-T6, 7075, 2024, 5052, 6082. Fast cutting, good finish, low mass.
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  TitaniumTC4 (Ti-6Al-4V), TA1, TA2. Heat and work-hardening need rigid setups.
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  Nickel alloysInconel. High temperature strength, short tool life, slower cycles.
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  Stainless17-4PH, 316L, 440C. Corrosion resistance for fuel and hydraulic parts.

A three-axis machine reaches a face by moving the tool along X, Y, and Z. Any feature on a fourth side means the operator unclamps the part, repositions it, and dials it in again. Every one of those steps adds stack-up error and hours. On a complex aerospace bracket with features on five faces, that can mean four setups and four chances to drift.

A five-axis center adds two rotary axes, usually a tilting and rotating table. The tool and the work move together, so undercuts, angled holes, and contoured pockets get cut in one continuous pass. We run 16 simultaneous five-axis machining centers alongside 12 four-axis mills and 27 three-axis machines, and the choice is not about prestige. A part with one flat face and a couple of drilled holes belongs on a three-axis machine.

The practical gain is positional consistency. A hole pattern and its mating boss stay in the same coordinate frame from roughing to finishing, so the relationship between them holds. That matters more than any single tight dimension on the print.

Rigid workholding still decides the outcome. Thin-walled housings and long, slender shafts deflect under cutting force, and no controller can compensate for a part that moves. We build soft jaws, fixtures, and support structures around the geometry before the first chip.

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  One setupAngled faces and undercuts cut without re-clamping the part.
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  Fewer datumsFeature relationships stay inside one coordinate frame.
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  ReachShort, stiff tool assemblies instead of long extensions.

Our standard production tolerance is ±0.005 mm (±0.0002 in) on critical features. That figure is not universal. It applies to a feature the machine can reach with a rigid setup, in a material that behaves predictably, at a size the thermal cycle will not fight. On a 7075 plate with a stable fixture, it is routine. On a 300 mm thin-wall titanium housing, the same callout needs a conversation.

Surface finish is set by the finishing pass, not by the machine model. As-machined cuts land around Ra 1.6–3.2 μm. A controlled finishing pass reaches Ra 0.8–1.6 μm, which is the common target for sealing faces and bearing bores. Fine finishing down to Ra 0.2–0.8 μm is achievable on the right geometry, but it costs cycle time and often needs a dedicated tool.

Part size matters too. Our largest travel is 4,000 × 400 × 150 mm for long structural sections. Mid-size work runs on 750 × 1,150 × 550 mm and 600 × 600 × 600 mm travels, and compact precision parts on 500 × 500 × 450 mm or 500 × 310 × 200 mm machines with a Ø400 mm rotary table. Maximum processing size is 4,000 mm.

Tell us which dimensions are functional and which are reference. Relaxing a non-critical callout often removes a grinding step and a week of schedule.

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  Tight±0.005 mm on reachable, rigidly held critical features.
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  SealingRa 0.8–1.6 μm for bores and mating faces.
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  FineRa 0.2–0.8 μm when geometry allows a dedicated finishing pass.

Every job gets a raw material check before cutting. Certificate of analysis and grade verification catch a substitution before it becomes a finished part. During the run, operators monitor critical dimensions against the setup sheet rather than waiting for the end of the cycle.

Final inspection is 100% before shipment, not a sample. We measure against the drawing, record the results, and issue reports on request. For tight-tolerance features, that means CMM work on a temperature-stable part, because a warm aluminium bracket measures differently than a cold one.

This is also where the 99.99% qualification rate comes from. It is a record of parts that passed final inspection against the print, not a marketing claim. When a dimension drifts, we stop and correct the process instead of shipping and sorting later.

If your program needs first article inspection reports, dimensional data sheets, or material traceability tied to lot numbers, say so at quoting. Building that into the plan costs less than adding it after machining.

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  IncomingMaterial grade and certificate checked before the first cut.
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  In processOperators measure critical features during the run.
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  Final100% inspection before shipment, reports on request.

There is no minimum order quantity. A single bracket and a 10,000-part run go through the same planning steps; only the tooling and inspection plan scale. For prototypes, we start production within 24 hours of an approved plan and ship parts in 3–5 days. Quotation and DFM analysis come back within 12 hours.

The DFM review is where most cost gets removed. We look at wall thickness, tool reach, corner radii, and whether a feature should be milled at all. Sometimes a pocket that needs a long, thin tool is better redesigned as two parts or moved to a cast or printed blank.

We run three wholly-owned plants covering 7,600 m², with 150 technicians and 127 high-precision CNC machines in total. That capacity matters for repeat programs: the same fixtures and process sheets stay with the part number across builds.

Documentation stays with the job. Uploads are handled as confidential, and we sign an NDA on request before drawings move. For aerospace work, that is usually the first step, not the last.

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  PrototypeProduction start within 24 hours, parts ship in 3–5 days.
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  Repeat runsSame fixtures and process sheets per part number.
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  Capacity127 CNC machines across three plants, 150 technicians.