Plastic Centrifugal Impeller, 470mm, at 20,000 Units a Year

What the OEM sent us

Initially a high-volume OEM sent us a drawing and a question. Could we supply this plastic centrifugal impeller at 20,000 units a year?

The quantity alone told us what it was for. In practice volume like that means a large production line. Most likely commercial HVAC gear, such as rooftop units or modular air handlers.

What the drawing demanded

• First, an outer diameter of 470mm with a height of 147mm.
• Second, a machined central bore of 12mm, held to +0.012/+0.010mm.
• Meanwhile ABSG5 material, an ABS grade chosen for impact strength and stability.
• Next, dynamic unbalance no greater than 1g at 750 RPM.
• Finally, unspecified molding tolerances to the GB/T14486-MT3 standard.

That bore tolerance is worth a pause. In effect, two microns means direct-drive mounting on one specific motor shaft. No coupling absorbs the error.

Meanwhile the 1g balance figure is what keeps vibration and noise out of the finished HVAC assembly.

Making the plastic centrifugal impeller at scale

This was not a new design. Instead it tested whether we could hold a tight spec at scale.

Checking the geometry against what we know

Usefully, a 470mm diameter sits between our standard 450mm and 500mm backward-curved models. Consequently we had relevant CFD data and mold experience to draw on.

Similarly, the seven-blade layout follows our AcousticFlow rules, favouring static efficiency and low noise. Paired with a suitable EC motor, our analysis put it in the right range for a medium air handler. It also suits a 5 to 15-ton rooftop evaporator section.

The material was already right

Even so, we reviewed ABSG5 rather than accepting it blindly. It held up.

Admittedly glass-filled polypropylene was an option, with slightly better heat resistance. However, ABSG5 gives a better surface finish and more impact strength. That matters where a service engineer might knock the part during access.

We ruled out metal at once. It fails the cost and weight targets for this class of gear. Moreover at roughly 750 RPM there is no structural case for aluminum or steel.

The real problem: 20,000 identical parts

Anyone can mold one good impeller. By contrast, holding the bore tolerance and the balance grade across a year of production is the real engineering.

Here the mold uses a hardened steel insert at the hub. That is what keeps the 12mm bore stable as the tool wears. Meanwhile every plastic centrifugal impeller goes through two-plane dynamic balancing after molding.

That is 100% inspection, not sampling. At these numbers a sample plan lets a bad batch slip past. Consequently it reaches the OEM line before anyone notices.

The deliverable was a full technical data package plus a volume-based quotation.

Technical Specifications

Meanwhile the bore tolerance and balancing grade below are the demanding rows. By contrast, diameter and blade count are not.

Parameter	Value
Impeller Model	LWB-φ470*147-01
Impeller Diameter	470 mm
Impeller Height	147 mm
Shaft Bore Diameter	Ø12 mm (+0.012/+0.010)
Number of Blades	7
Blade Type	Backward-Curved
Material	ABSG5
Balancing Grade	≤ 1g @ 750 RPM
Typical Assembly Performance (LWBE3G-450 Class)
Max Airflow	5,800 – 12,500 m³/h
Max Static Pressure	1,600 Pa
Typical Input Power	1,100 – 2,200 W
Typical Speed	750 – 1,800 RPM
Typical Voltage (EC Motor)	200-480 VAC

Technical Documentation

The drawing and the spec sheet for this plastic centrifugal impeller are below. Both carry the quality control figures, since those are what a buyer checks.

Open Technical Data Sheet (PDF)

Why the OEM placed the volume here

Placing 20,000 plastic centrifugal impellers a year is a decision about supply chain and quality systems. It is not really about one part.

• Proven capacity. Naturally a frame agreement at this volume needs demonstrated output. We have made fans in Ningbo since 1990, and ship over 120,000 data center units a year. So the scale is real, not promised.
• Cost structure. Furthermore, asking for a plastic centrifugal impeller signals a cost-sensitive product. Our engineering depth plus China-based manufacturing puts this class of part materially below imported European brands. Consequently the OEM hits their bill of materials target.
• A fast, decisive answer. They needed confirmation, not a study. Owning our own mold tooling and performance verification let us validate the part, confirm manufacturability and quote a production plan within a few working days.
• Balance you can audit. A 1g figure means nothing without process control behind it. Our ISO 9001 system logs 100% in-line balancing data. So the number is proven rather than claimed.

Browse our fan impeller range, or the backward curved fan section. Balance grades follow ISO 21940.

Questions about this component

What is the lead time for a first production order?

After sample approval, a first run of 1,000 to 2,000 units takes 30 to 45 days. Afterwards, once a frame agreement is in place, scheduled deliveries run 15 to 30 days. Both beat the 12 to 18 weeks typical for similar parts from European suppliers.

Can you supply it as a complete plug fan?

Yes. This project was the impeller alone, though the part is designed to work with our standard EC motor platforms. A complete assembly would come from our plug fan series, with a SmartEC controller taking 0-10V, PWM or RS485. Full AMCA 210/211 verified P-Q curves are available for the assembly.

What quality documentation ships with each batch?

Every shipment carries a Certificate of Conformance. Strategic OEM partners on high volume also get direct access to batch reports from our manufacturing execution system, covering statistical process control on critical dimensions and the balancing results for the lot.

Why does the bore tolerance matter more than the diameter?

Because the bore sets how the plastic centrifugal impeller sits on the shaft. Everything else follows from that. A few tenths of a millimetre on the outer diameter changes performance imperceptibly. By contrast, a loose bore lets the part run off-center, which shows up as vibration no amount of balancing will fix.

Choose the right centrifugal impeller

Longwell manufactures 12 centrifugal impellers in-house. Send airflow, static pressure and voltage — an engineer replies with a matching model, performance curve and price within one working day.

Get a quote Browse centrifugal impellers Wind Wheel catalog (PDF) ↓ Aluminum Impeller (Backward) catalog (PDF) ↓