Hangzhou CNC machining: a guide to precise manufacturing

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  How Hangzhou CNC machining removes metal
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  3-axis, 4-axis and 5-axis: which one fits the part
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  What ±0.005 mm really means on the shop floor
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  Material choice changes the cut, not just the part
• 5
  What moves cost and lead time
• 6
  Machine and process fit by part type

Hangzhou CNC machining is subtractive manufacturing under numerical control. A CAM program converts the solid model into toolpaths, the controller turns those paths into servo commands, and the spindle follows them while a cutter bites into the stock. Nothing about the geometry depends on a machinist's hand. The machine repeats the same motion until the tool wears or the fixture moves.

Three variables set the outcome. Cutting speed decides how fast the edge travels through the material. Feed rate sets how far the tool advances per tooth. Depth of cut sets how much material each pass removes. Push any one too far and the surface tears, the tool chatters, or the insert breaks. Hold them in balance and the cut stays quiet.

The tool leaves marks. A face mill running at Ra 1.6–3.2 μm leaves visible scallops. A fine-finish pass with a sharp insert and a light radial engagement can reach Ra 0.8–1.6 μm, and a dedicated finishing strategy with small stepover reaches Ra 0.2–0.8 μm. Surface finish is not a coating. It is the arithmetic of feed per tooth and tool radius.

Accuracy is separate from finish. A part can be mirror-smooth and still be 0.05 mm out of position. Positional accuracy comes from the machine's servo loop, the thermal state of the casting, and how rigidly the workpiece sits in the fixture. That is why a warm spindle cuts differently from a cold one.

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  SpeedSurface meters per minute at the cutting edge
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  FeedMillimeters per tooth, multiplied by flute count
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  DepthRadial and axial engagement per pass
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  RigidityTool overhang, fixture stiffness, workpiece support

A 3-axis machine moves the tool in X, Y and Z while the part stays still. It handles prismatic work: plates, housings, brackets, pockets and drilled hole patterns. Setup is simple and cycle time is short. The limit is access. Any feature on a side face needs a second setup, and every new setup adds a datum error.

A 4-axis machine adds a rotary table, usually turning about the X axis. A Ø400 mm rotary table lets the part index to four sides in one program. Shafts, manifolds and parts with a repeating pattern around a bore become one-op jobs. What it cannot do is tilt the tool relative to the surface, so undercut geometry still needs a second machine.

A 5-axis machine adds a second rotary axis. Two rotary axes plus three linear axes move at the same time, so the tool stays normal to a curved surface through the whole pass. Impellers, turbine blades, deep cavities with drafted walls and angled ports cut in one setup. The trade is programming time and machine hour rate.

The decision is rarely about capability alone. A part with six drilled faces can run on a 3-axis machine with two setups and still hold ±0.005 mm if the fixture is sound. A part with a blended curved surface usually cannot. Count the setups first, then count the surfaces that need continuous tool orientation.

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  Pick 3-axisPrismatic parts, flat datums, features reachable from one direction
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  Pick 4-axisShafts, rotary patterns, four-sided access in one setup
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  Pick 5-axisCurved blends, deep drafted cavities, angled holes, one-setup accuracy
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  Not worth itSimple plates on 5-axis waste machine hours

Tolerance is a budget, not a wish. Aluminum expands about 23 μm per meter per degree Celsius. A 300 mm aluminum part that warms 5 °C during roughing grows roughly 0.035 mm. If the finishing pass runs before the part cools, the measured size drifts. Good shops rough, cool, then finish.

Thermal drift is the first thing to attack. The second is fixture compliance. A thin wall clamped hard will spring back after unclamping and land outside tolerance. That is why ribs and webs get support, why light finishing passes use low radial engagement, and why some parts are stress-relieved between roughing and finishing.

Measurement matters as much as cutting. A micrometer on a warm part reads a different number than a CMM in a 20 °C room. Calibration, probe temperature compensation and a stable inspection room decide whether the number on the report is real. Reports from raw material check, in-process monitoring and final inspection are available on request.

Where tighter tolerance is genuinely needed, it is usually needed on two or three features, not the whole drawing. A bearing bore, a dowel hole, a sealing face. Mark those as critical and let everything else run at general tolerance. That single change often removes a grinding operation and a week of lead time.

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  ThermalLet the part reach room temperature before finishing
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  FixtureSupport thin sections; avoid over-clamping
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  DatumsOne datum scheme across all setups
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  Critical features2–3 tight tolerances, not a fully tight drawing

Aluminum 6061-T6 machines fast and holds a good finish. 7075 is stronger and cuts cleanly but costs more and is less weldable. 2024 has better fatigue behavior and poorer corrosion resistance. These are not small differences. They change feeds, speeds and sometimes the whole process plan.

Stainless 303 is free-machining and produces short chips. 304 and 316 work-harden under a dull tool, so the cut has to stay aggressive and the insert has to stay sharp. 17-4PH in the H900 condition is hard enough that finishing passes need care. Titanium TC4 (Ti-6Al-4V) conducts heat poorly, so the heat goes into the edge instead of the chip.

Inconel and magnesium sit at the extremes. Inconel punishes tools and demands low surface speed with high pressure coolant. Magnesium AZ31B and AZ91D cut easily but the chips are a fire risk, so chip management is part of the process, not an afterthought.

Copper alloys behave differently again. C36000 brass machines freely. Beryllium copper machines well but requires dust control. C110 copper is gummy and tends to tear, so it needs sharp tools and generous coolant. The material decides the toolpath before the geometry does.

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  Free cutting6061-T6, 303 stainless, C36000 brass
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  Work hardening304, 316 stainless; keep the edge engaged
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  Heat resistantInconel, TC4 titanium; expect slower removal
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  Fire riskMagnesium alloys; chip control is mandatory

Setup count drives cost more than cutting time on small batches. Each setup needs a fixture, a datum, a probe cycle and a first-article check. Removing one setup often saves more than speeding up the spindle. This is the strongest argument for 4-axis and 5-axis work on complex parts.

Feature density matters too. A part with 40 tapped holes and 12 tight bores costs more than a part with a large simple pocket, even if the second part weighs more. Tool changes, peck drilling cycles and inspection points all add minutes.

Finish is the third lever. As-machined at Ra 1.6–3.2 μm is the default. Bead blasting, anodizing, electroless nickel or hardcoat all add steps, and every step adds handling. Specify the finish that the function needs, nothing decorative.

Quantity sets the floor. There is no minimum order quantity here, so a single prototype and a 10,000-part run both go through the same process. But unit cost falls as volume rises because programming and setup amortize. Quotation and free DFM analysis come back within 12 hours, and production can start within 24 hours of an approved plan.

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  Fewer setupsConsolidate features into one orientation
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  Loose non-critical facesGeneral tolerance where function allows
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  Functional finish onlyMatch the finish to the sealing or wear surface
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  Batch sizeVolume amortizes programming and fixturing