TL;DR

• Free-air airflow overstates what you get by roughly a third. The published reference blower delivers 165 L/min at 0 kPa and 104 L/min at 12 kPa. Selecting on the 165 figure means specifying a blower that cannot inflate cushions at working pressure.
• Read the duty point off the P-Q curve. The rated point at 12.0 kPa / 104 L/min is the figure closest to a real inflation condition, and it is a far better reference than any headline number.
• Size the electrical supply for the blocked case. Published current goes from 3.7 A at free blowing to 7.2 A at blocked outlet — roughly 1.9×. A blockage during production is a transient, not an exception.
• Forced cooling is a requirement, not an option. Published operating range is −20 to +40°C with forced cooling, and the safety note states a cooling fan is required in the red zone to prevent overload damage.
• Demand the tolerances. Speed ±5% (±3% at rated), current ±15–20%, flow ±10%, pressure ±10%. Nominal-only quotations are not guaranteed numbers.

Almost every blower selection error in air cushion packaging comes down to one mistake: treating a blower’s headline airflow as though it were available at working pressure. It is not, and the gap is large enough to matter.

The reference data behind this article makes the point with unusual clarity because it is published at three conditions. The unit is rated at 165 L/min with the outlet fully open at zero pressure, 28.0 kPa with the outlet fully closed and zero flow, and — at the rated operating point — 12.0 kPa with 104 L/min. That middle figure is the one a machine designer actually needs.

The Seven Steps

Each step below is one decision, and the order matters because each one narrows the field for the next.

1. Establish the flow you need at cushion inflation pressure, not the flow you would like in free air.
2. Read that requirement off the P-Q curve and treat the rated point as the primary reference.
3. Size the driver and supply for the blocked condition, not the running condition.
4. Confirm the duty cycle and the thermal requirement, including whether forced cooling is required in your enclosure.
5. Require the performance figures with their tolerances rather than as nominal values.
6. Verify mechanical integration — dimensions with tolerances, port size, cable and wiring sequence.
7. Establish the compliance position for the destination market before the machine design is frozen.

Step 1 and 2: The Duty Point, Which Is Where Selection Actually Happens

A blower has a characteristic curve, and almost nobody looks at it. The curve describes what the unit does across the whole range from free air to fully blocked outlet, and the two headline figures most suppliers quote are simply the two ends of it.

Three things fall out of that table.

The free-air figure is not your figure. 165 L/min is the number a supplier will put on the first line of a quotation because it is the largest number available. Your machine inflates cushions at a pressure — and at 12 kPa the same blower delivers 104 L/min. That is roughly 37 percent less than the headline. If you size against the headline and the cushion fills slower than planned, the instinct is usually to blame the blower, when the real error was in the selection.

The rated point is the most useful single number. It is the only published figure that corresponds to an actual duty condition rather than an extreme. Published as 12.0 kPa and 104 L/min at 39000 rpm, it is the closest thing to a realistic inflation reference in the whole data set, and it is the figure worth putting in a specification.

Both extremes have almost no practical use. Free blowing never occurs in a working machine because there is always back pressure. Fully blocked outlet should not occur in a working machine because that is a fault. Quoting either as the headline is quoting a number that your application will never see.

Step 3: Why the Driver and Supply Have to Be Sized for the Blocked Condition

Current nearly doubles between the free-air and the blocked condition. Published figures show 3.7 A at free blowing and 7.2 A at blocked outlet, a ratio of approximately 1.9×.

That is not a problem to be designed around. It is a problem to be sized for.

A blockage during a production run is not an exceptional event. It happens when a tube kinks, when a cushion bursts and seals its manifold, when a downstream valve sticks, or when a filter is loaded. The motor does not know that the blockage is temporary, and it will draw the higher current for as long as the condition persists. The supply, the driver, and the protection circuit have to survive that, and the published safety note — stating that a cooling fan is required in the red zone to prevent equipment damage due to overload — exists for exactly this kind of event.

The other thing the table shows is that speed falls as pressure rises: 41000 rpm at free blowing, 39000 at the rated point, 36500 at blocked. The motor is not constant-speed in this configuration; it is a load-dependent speed that backs off under pressure. That is normal and expected for this class of blower, but it has a consequence worth noting, which is that the headline speed figure is the no-load figure rather than the operating figure.

Step 4 and 5: Duty Cycle, Thermal, and the Tolerance Question

The published operating temperature range is −20 to +40 °C, marked as forced cooling, with storage at −30 to +70 °C and up to 90 percent relative humidity non-condensing. The published safety note states that a cooling fan is required in the red zone.

An air cushion packaging machine inside an enclosure running continuously is a different thermal case from a blower on a bench in open air, and the published envelope is for the latter. Two consequences follow.

The first is that the thermal margin inside the machine enclosure is the design question, not the blower’s published figure. The blower can survive +40 °C ambient in the published condition, but it cannot survive +40 °C ambient inside an enclosure with no air movement, which is closer to the situation in a working machine. Forced cooling is therefore a design input for enclosed continuous-duty use rather than a refinement.

The second is the tolerance question. The published performance figures are not nominal. Speed is stated with ±5% tolerance at the end conditions and ±3% at the rated point. Current is ±15% at free blowing and ±20% at the other conditions. Airflow is ±10%. Pressure is ±10%. A quotation that quotes the nominal values without the tolerances is quoting a number the supplier is not committing to, and the difference matters when you are sizing the driver and the supply.

Step 6: Mechanical Integration Comes Before Electrical

Electrical sizing gets most of the attention because it is easier to put a number on, but mechanical integration is what makes or breaks the assembly.

Published key dimensions on the reference unit are 400 ±20 mm, 95.5 ±1.5 mm, and 65 ±0.30 mm, with 8 mm inlet and outlet and a 400 mm three-core cable. The pin assignment is documented: pin 1 white for phase W, pin 2 blue for phase V, pin 3 yellow for phase U. The cable output position and angle are stated as not fixed, which is useful because it means the wiring can be routed to fit the enclosure rather than the enclosure being cut to fit the cable.

Two specific items are worth checking before mechanical integration is finalised.

The inlet and outlet size. 8 mm is the published size on the reference unit. That size determines the coupling, the sealing method, and the additional pressure drop introduced by the connection. If the cushion tubing or the manifold connection is a different size, the coupling has to be ordered, and a coupling that is too small is a maintenance problem and a coupling that is too large is an air-leak problem. Confirm both ends.

The tolerance on the long axis. The 400 mm dimension carries a ±20 mm tolerance, which is unusually wide for a key dimension. The reason is probably that the dimension is to a specific feature rather than the overall length, but the practical consequence is that the cutout in the chassis has to accommodate that range. Do not assume the published figure is the maximum dimension.

Step 7: Compliance and the Machine-Level File

Air cushion packaging machines fall within household and similar electrical appliance safety requirements in their target markets. The most relevant standard is IEC 60335-2-80, which covers the safety of electric heating appliances, and the broader ISO 1461-1 for hot-dip galvanizing on metallic parts where relevant. In the United States, a product that is sold to consumers as a packaging machine and that is used in commercial settings may need to be assessed under additional product safety regimes.

The blower inside the machine forms part of that assessment, and the documentation the blower supplier can provide — insulation class, thermal data, the safety note the reference unit publishes, the wire and connection standards — has to be available to the machine’s compliance file. A blower selected purely on its electrical and mechanical specification may not provide the documentation the machine needs, and that constraint is easier to resolve before the design is frozen than after.

Two practical questions to put to the blower supplier before the order is placed: what test reports or material declarations can be provided for the destination market, and what is the documentation chain from the blower supplier to the machine compliance file. Both are easier to settle on a sample order than to recover after a production order.

What a Complete Selection Looks Like in Practice

Pulling the seven steps into one sequence, a complete specification against the published reference unit looks like this.

1. Determine the inflation pressure your cushions actually need, expressed in kPa.
2. Read the P-Q curve at that pressure, and read off the flow and current at that point.
3. Confirm that the published rated point covers your working pressure with margin, or that an alternative is sized accordingly.
4. Size the driver and supply for the published current at blocked outlet plus a margin.
5. Confirm forced cooling is provided in the enclosure under continuous duty.
6. Confirm all published dimensions and tolerances against your chassis.
7. Confirm the 8 mm inlet and outlet match your tubing and manifold.
8. Request the published performance figures with the published tolerances, not as nominal values.
9. Establish the compliance contribution before the design is frozen.

That is the whole job. The hard part is the conversations it requires with both the blower supplier and the downstream engineering team, and the easiest part to skip — the P-Q curve — is the one that the rest of the selection depends on.

Frequently Asked Questions

Where I Would Qualify This Advice

This article is written from the blower side, and that shapes two of the recommendations in ways a machine designer would reasonably challenge.

The first is on the compliance step. I have said that the blower documentation has to be available to the machine compliance file, and that is true as a constraint. But how much of it is required varies substantially by market and by machine classification, and a supplier who is confident about your specific destination can often tell you in a sentence what is needed. Asking the blower supplier what they can provide for your market is faster than working through the standard yourself, and I would do that before doing either.

The second is on thermal. I have argued that the published operating envelope does not account for enclosure thermal rise, and that is a correct observation about what a blower datasheet measures. A machine designer with thermal modelling on the enclosure has a much better handle on the actual figure than I do, and the right outcome is not more margin added to the blower but a modelled number feeding back into the blower choice.

There is also a limit worth naming on the pressure-flow discussion. This article treats the curve as the primary selection reference, and for this class of machine that is correct. Where cushion inflation involves a long tube run or a restrictive manifold, the system resistance curve shifts, and the intersection of the blower curve with the actual system curve is what determines the working point rather than a single pressure figure. That analysis is straightforward but it is engineering work rather than a selection rule, and I have kept it out of a seven-step article deliberately.

Send Your Duty Point and Get a Sizing Recommendation

If you can state the inflation pressure your machine needs and the flow you require at that pressure, a sizing conversation becomes short. If you add the duty cycle, the enclosure ambient, and the connection sizes, it becomes a complete specification in one exchange.

The 24V brushless high pressure centrifugal blower product page carries the full three-condition performance table with tolerances, the driver specification, the dimensional figures with their tolerances, the port sizes, the wiring assignment, and the environmental envelope.

The air cushion machine blower category covers the broader range across 12 V, 24 V and 48 V supply options, so a duty point that falls outside the reference unit can usually be matched against a neighbouring model without starting from scratch.

Mr. Dong

Technical Director, Ningbo Wonsmart Motor Fan Co., Ltd.

I lead our brushless DC blower engineering and application support across the medical, industrial, and laser equipment sectors. Most of my time goes into the part of a project that happens before the quotation: aligning the motor specification to the duty point, checking that the part actually fits the enclosure it is going into, and making sure the documentation a machine needs exists before the machine design is frozen.

Our compliance work covers IEC 60601-1 for medical devices and industrial EMC, RoHS, and REACH requirements, which is a different conversation from an air cushion machine — but the discipline is the same. A part that cannot supply what the compliance file needs is a part you find out about too late. That is why the selection sequence in this article ends at documentation rather than at the P-Q curve.

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