Guides

Sizing a vacuum lifter – suction force, safety and the limits of the technique

No gripping principle is faster: approach, draw, lift. None has such clear limits either. Knowing them means sizing a vacuum lifter correctly in ten minutes – and recognising just as quickly the cases where a clamp is the better answer.

Author: Dr.-Ing. Philipp Schwittek
Reading time: 9 minutes
Updated: 05. September 2026

The key points

Theoretical holding force per cup is area times vacuum – the permissible force is considerably lower.
For vertical lifting a safety factor of 2 is usual, for tipping or horizontal holding a factor of 4.
Porous, damp, strongly curved or oily surfaces are the classic borderline cases.
On energy failure the load has to stay held – check valve, reserve volume, vacuum monitor.
More cups are almost always cheaper than a bigger generator.

The calculation in three steps

The holding force of a cup follows from its effective area and the vacuum achieved. A cup of 100 millimetres diameter has around 78 square centimetres; at 0.6 bar of vacuum that is theoretically about 470 newtons, roughly 48 kilograms. After the safety factor, half or a quarter of that remains. The number of cups follows from it – and from the need to support the load against sagging.

Step 1: determine the effective suction area per cup
Step 2: multiply by the vacuum achievable – 0.6 bar is a realistic value
Step 3: divide by the safety factor: 2 for vertical lifting, 4 for tipping
Multiply the result by the number of cups and check it against the load
Check the layout: force is not the only issue, support against sagging counts too

Why safety factors are arithmetic, not caution

The factor represents what additionally occurs in service: acceleration on lifting, the sealing lip giving way, vacuum falling over time, contamination. For vertical lifting with steady guidance a factor of 2 is usual; as soon as the load is tipped, held horizontally or moved quickly, 4 applies. Plan with the theoretical figure and you build a device that holds in the laboratory and drops the load in the hall.

Where vacuum reaches its limits

Four cases account for nearly all the trouble. Porous material – raw chipboard, concrete, uncoated paper – draws air continuously; here the pump has to keep supplying rather than drawing once. Damp or oily surfaces let the sealing lip slip. Strongly curved parts give the lip no seating; bellows cups or a form-matched mount help there. And structures with holes, joints or beads turn the cup layout into the actual design task.

What safety requires

A vacuum lifting device has to hold the load when energy fails. In practice: check valve, reserve volume for a defined holding time, vacuum monitor with visual and audible warning. With critical loads two separate suction circuits are added. These points are not accessories but preconditions – and they belong in the documentation, because they are checked at the recurring inspection.

Ejector or pump – a question of operation

A vacuum ejector runs on compressed air, needs little maintenance and is available instantly; it consumes air continuously and is expensive to run on porous surfaces. A vacuum pump needs electricity and some maintenance but delivers large volume flows and is the more economical choice on porous material. Rule of thumb: sealed surfaces and short cycles favour the ejector, porous material and continuous duty the pump.

Overview

Guide values per cup at 0.6 bar vacuum

Diameter	Area	Theoretical	Permissible vertical (factor 2)	Permissible tipping (factor 4)
50 mm	around 20 cm²	around 12 kg	around 6 kg	around 3 kg
80 mm	around 50 cm²	around 31 kg	around 15 kg	around 8 kg
100 mm	around 78 cm²	around 48 kg	around 24 kg	around 12 kg
150 mm	around 177 cm²	around 108 kg	around 54 kg	around 27 kg
200 mm	around 314 cm²	around 192 kg	around 96 kg	around 48 kg

Frequently asked questions

Frequently asked questions about Sizing vacuum lifters

How many cups do I need?

Enough for the permissible holding force to exceed the load with reserve – and laid out so the part does not sag. With large, thin parts the layout usually decides rather than the force: four cups at the corners carry enough but let the panel sag in the middle.

Do cups hold on raw wood or concrete?

Yes, if suction capacity is designed for it. Porous material draws air continuously; what matters is not the vacuum achievable but the volume flow the generator keeps supplying. For such cases we use pumps rather than ejectors and calculate with reserve.

What happens on power or air failure?

Nothing – if the device is properly built. Check valve and reserve volume hold the load for a defined time, and the vacuum monitor warns visually and audibly. That is mandatory for vacuum lifting devices and is checked at every recurring inspection.

When is a clamp the better choice?

On porous, damp or oily surfaces, on strongly curved or perforated parts, and always where the load is to be tipped or turned and a failure could not be managed. Vacuum is the fastest pick-up but not the most universal.

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