Five-Axis CNC Milled Aluminum Impeller
Custom five-axis CNC milled aluminum impellers for centrifugal fans, blowers and vacuum pumps, cut from a single billet so the blade surfaces, hub bore and backplate stay in one datum instead of being assembled from separate parts.
- Five-Axis Simultaneous Milling
- Single-Billet Construction
- Blade Profile to ±0.02 mm
- Dynamic Balancing Available
*Send the flow rate, duty speed and hub interface before the blade profile is finalized, as all three decide the trim diameter and the balance grade.
Aluminum Impeller Overview
Five-axis milled impellers for fans, blowers and pumps, where airflow, balance and bore fit decide whether the assembly runs quietly.
An impeller converts shaft power into flow, and every one of its surfaces does a job: the blade profile sets the head and efficiency, the hub bore sets the running fit, and the backplate sets the axial clearance to the housing. Milling all three from one billet keeps them in a single datum, which is why a machined impeller usually needs less trim balance than a welded or cast one.
The difficulty is not the shape but the stiffness. Blades are thin, unsupported at the tip and interrupted by the flow channel, so a three-axis tool path pushes them away from the cutter and leaves a profile that is right in the file and wrong on the part. Five-axis simultaneous milling keeps the tool normal to the blade surface, shortens the overhang and lets the root fillet be cut in the same pass, which is the difference between a part that balances first time and one that needs correction.
SINORISE machines impellers from Ø60 to Ø400 mm with 6 to 24 blades, open or shrouded, in 6061-T6, 7075-T6 and 2024-T351. Prototypes and small batches are the normal case, including re-trimming an existing impeller to a smaller diameter, reproducing a worn impeller from a scan, and machining a hub interface to match a new motor shaft.
6061-T6 Aluminum
6061-T6 is the default for general ventilation and process fans. It machines cleanly at high spindle speeds, holds a thin blade without cracking, anodizes to an even colour and is the least expensive of the three grades, which matters on impellers that are large in diameter but simple in blade form.
Its limit is strength at speed. Above roughly 6,000 rpm the blade root starts to carry more load than the temper comfortably allows, and the tip growth that follows changes the clearance to the housing.
7075-T6 Aluminum
7075-T6 is specified for high-speed fans, vacuum pump rotors and competition parts where blade stiffness decides the result. Its strength is close to that of mild steel at a third of the weight, so blades can be thinner and the hub smaller for the same flow.
It is less forgiving to machine: the material is harder on cutters, it cannot be welded, and thin sections need light radial cuts to avoid chatter. Anodizing also shows alloying streaks, so cosmetic parts are usually bead blasted before coating.
Grade, trim diameter and balance grade should be specified together, since each changes the blade thickness and the hub geometry.
Aluminum Impeller Specifications
Machining and balance data for five-axis milled impellers, agreed to the fan duty and the motor interface.
| Specification | Machining Data | Specification | Machining Data |
|---|---|---|---|
| Product | Aluminum Impeller / Blower Wheel | Blade Machining | Five-Axis Simultaneous Milling, Flow Channels to CAD Surface |
| Material | 6061-T6 / 7075-T6 / 2024-T351 | Hub Machining | Turning, Boring, Broaching, Keyway Cutting |
| Machining Process | 5-Axis CNC Milling, CNC Turning, Drilling | Surface Finish | Ra 1.6 \\\\µm on Flow Surfaces, Ra 0.8 on Bore |
| Typical Tolerance | \\\\±0.02 mm on Blade Profile | Balance Grade | G6.3 at 3,000 rpm (G2.5 on Request) |
| Diameter Range | \\\\Ø60 \\\\– \\\\Ø400 mm | Bore Fit | H7 / H8, Concentricity 0.01 mm |
| Blade Count | 6 \\\\– 24 Blades, Backward or Forward Curved | Wall Thickness | Minimum 1.5 mm at Blade Tip |
| Machined Features | Blades, Hub Bore, Keyway, Backplate, Balance Holes | Drawing Format | STEP, STP, IGES, X_T, DWG, DXF, PDF |
| Customization | Blade Angle, Hub Interface, Trim Diameter, Coating | Lead Time | 7\\\\–12 Days (Prototype), 12\\\\–20 Days (Batch) |
| Inspection | CMM Blade Scan, Bore Gauge, Balance Report | Packing | Foam-Cradled, Individually Boxed, Carton |
Key Features of Our CNC Milled Impellers
Built for airflow, balance and a bore that fits the shaft without shimming.
Blade Surface Machining
Blades are milled with the tool kept normal to the surface, so the profile follows the CAD model from leading edge to trailing edge and the root fillet is cut in the same pass instead of being blended by hand.
Hub and Bore Accuracy
The hub bore is turned and bored after the blades are cut, to H7 with 0.01 mm concentricity to the blade datum, so the impeller runs true on the shaft without a balancing correction for eccentricity.
Thin-Wall Control
Blade thickness is held by taking light radial cuts at high spindle speed and supporting the blade from behind where the geometry allows, which keeps tip deflection and chatter marks out of the finished surface.
Balancing and Inspection
Each impeller is balanced to G6.3 or G2.5 at the service speed, then scanned on a CMM against the blade model, with both reports issued with the part.
Need an impeller that balances first time?
Surface Finishes for CNC Machined Impellers
Finishing on an impeller is about airflow as much as protection, so the flow surfaces and the bore are usually treated differently.
| Finish | Main Purpose | Finish | Main Purpose |
|---|---|---|---|
| As Machined | Bare milled surface where airflow and cost govern | Anodizing | Corrosion protection and colour identification |
| Bead Blasting | Uniform matte flow surface, removes tool marks | Hard Anodizing | Wear resistance on hub and bore faces |
| Polishing | Ra 0.8 flow channels for reduced drag | Balancing | Material removal or set screws to reach the balance grade |
*Flow-surface finish, coating thickness and balance grade interact: a coating applied after balancing shifts the balance, so the sequence is agreed before production.
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CNC Machining Process for Aluminum Impellers
From blade model to balance report, each impeller follows one controlled route so the profile, the bore and the balance are all measured against the same datum.
01. Blade Model Review
Check the blade surfaces for tangency, minimum tip thickness and root fillet radius, then confirm the hub interface and the trim diameter against the fan duty.Thin or undercut blade tips are corrected in the model before programming, not on the machine.
02. Billet Preparation
Select 6061-T6 or 7075-T6 billet with enough stock for the backplate and hub, face both ends parallel, and mark the datum face that all five-axis operations are programmed from.
03. Five-Axis Milling
Rough the flow channels with a bull-nose cutter, semi-finish the blade flanks, then finish with a ball-nose cutter kept normal to the surface. The hub, backplate and balance pads are machined in the same setup to keep the datum intact.
04. Balancing and Finishing
Balance the impeller at the service speed and correct on the balance pads, then apply the specified coating or polish. When both are required, balancing is repeated after coating to confirm the grade still holds.
05. Inspection and Report
Scan the blades on a CMM against the model, gauge the bore and keyway, and check the backplate runout. The dimensional report and the balance report are issued with the parts.
Have an impeller that needs re-trimming or a new blade profile? Send the model, the duty point and the shaft interface to start the review.
CNC Machining Milling Aluminum Impeller FAQs
Yes. A STEP or X_T file with the blade surfaces and hub interface is enough to quote and program. If the model is a scan of an existing impeller, we rebuild the blade surfaces into a machinable solid and send it back for approval before cutting.
Blades down to 1.5 mm at the tip are practical in 7075-T6. Below that the blade deflects under cutting load and the profile drifts, so the part is usually split into a milled hub and a formed or welded blade set instead.
Yes. Impellers are balanced to G6.3 at the service speed as standard, and to G2.5 when the drawing calls for it. Unbalance is corrected by removing material from the balance pads or, on closed wheels, by adding set screws in the hub.
7075-T6 is the usual choice above roughly 6,000 rpm because its higher strength keeps the blade tips from growing under centrifugal load. 6061-T6 is adequate for lower speeds, humid air streams and parts that need a uniform anodized finish.
Yes. Keyways are broached or milled, splines are cut on a fourth axis, and clamping hubs with a split and pinch bolt are machined as one piece. The bore is finished after the blades so the blade load does not distort the fit.
A single impeller is typically 7–12 days including five-axis programming, machining, balancing and inspection. Small batches of 5–50 pieces run 12–20 days depending on material and coating.
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