When several cups are connected together in a single system, for example in a lifting device, the system can be adversely affected if a suction cup leaks or misses the work-piece. To overcome this, each suction cup can be provided with a valve that opens only when the suction cup is in contact with the object. The advantages are increased safety, less air consumption and faster action.


Using suction cups is a lifting technique with many possibilities. You can, for example, handle board materials or concrete slabs, open bags, pick electronic components, label and hold objects. But different applications need different requirements. PIAB offers one of the market’s widest ranges of suction cups so that each application will have its own solution.

Suction cups made from DURAFLEX ® — for increased productivity and performance

Increase your productivity and security with DURAFLEX ®, a strong and elastic material with excellent sealing capability. High friction and reduced micro-leakage increase the lifting capability and the cup’s outstanding wear resistance extends the change-over intervals. PIAB’s unique dual-hardness cups are ideally suited for applications where micro-leakage can occur, for example when a suction cup does not properly conform to a handled material, such as corrugated cardboard. Dual-hardness cups provide both the strength and flexibility needed to seal on uneven or coarse surfaces.


More Information


How does a suction cup work?


A suction cup adheres to a surface when the surrounding pressure (atmospheric pressure) is higher than the pressure between the suction cup and the surface of the object. To create the low pressure in the suction cup it is connected to a vacuum source. The lower the pressure, the higher the vacuum in the suction cup — results in increased lifting force.

Energy Requirements

Suction cups should not be exposed to unnecessarily high vacuum levels. Too high vacuum levels will cause unnecessary wear and require more energy. With an increase of the vacuum level from 18 -inHg to 27 -inHg the lifting force increases by 20–40% while the energy requirements are increased by a factor of 10.
Since the lifting force is directly proportional to the area of the suction cup, it is better to maintain a lower vacuum level and increase the area of the suction cup when more lifting force is required.

Safety Factors

The lifting force can be perpendicular or parallel to the surface to be handled. The values are based on sample data for a dry steel plate.
When sizing a suction cup, we recommend to always multiply the weight of the object to be handled by a minimum factor of 2 for increased safety.

Acceleration and Deceleration

Rapidly moving objects have additional dynamic forces arising from acceleration and deceleration. In this case, we recommend multiplying the object’s weight by a minimum of 2.5 when calculating the size of the suction cup.

Savings in energy and system costs

Leakage occurs in a system when one or more suction cups do not contact the object being handled. This may happen in applications where the number, the position or the size of the objects to be lifted varies. Usually a large vacuum pump is used to cope with the air leakage and to maintain the vacuum level. The result is an inefficient system in terms of energy and capital costs.
A better solution is to use PIAB fittings with valves. The valves stop or reduce the leakage so that a smaller, more appropriate vacuum pump can be used to decrease installation and operation costs.

Dual Control Valve

The air evacuated by the vacuum pump can only flow through a small opening (restriction). Even if the suction cup does not make contact with the object, the leakage will be minimal and the system will not be affected to any significant degree (a). When the suction cup makes contact with the object, only the cup’s own volume has to be evacuated and the vacuum is created rapidly (b). When the object is released, air opens the built-in flap valve in the fitting and flows through a larger opening. The object is thus released very quickly (c).
Caution: Fittings with dual flow control valves can be assembled on suction cups from 20 to 50mm in size (0.79″-1.97″ dia.). They are used only when lifting objects made of non-porous material.

Choosing the Right PUMP

How to choose the right PIAB vacuum pump when using a fitting with dual flow control valve.

The pump should be able to cope with the maximum leakage flow or the induced air that flows through the restriction. The following table shows, for every suction cup size, the diameter of the restriction and the air flow. The flow calculation is for a system with one suction cup and a vacuum level of 11.8 to 29.4 -inHg.

Dimensions of the cup Restriction,in Air flow, cf/s
20, 25, 30* (0.79″, 0.98″, 1.18″) Ø0.02 0.002
40** (1.57″) Ø0.03 0.005
50 (1.97″) Ø0.04 0.006
* Excl. B30-2, B30MF, BL30-2
** Incl. B30-2, B30MF, BL30-2
† Constant from approx. 11.8 -inHg to 29.4 -inHg.

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