What is a Vacuum Cup?

What is a Vacuum Cup?

A vacuum cup is a device which can be pushed onto the surface of an object; the flexible nature of the cup and the vacuum created within the cup, ‘stick’ the cup to the surface and allow the object to be lifted.

They are also known as...

They can also be referred to as suction cups.

How do vacuum cups work?

The diagram above shows a section of a suction cup (red) placed against a surface (black). The vacuum created in the cup, by a vacuum pump, means that the air pressure in the cup is significantly reduced, compared to the ambient atmospheric pressure (see arrows). The imbalance of pressure pushes the cup against the surface and force would be required to remove it from the surface. If this force (or the sum of forces of several cups) is greater than the weight of the object, then the object can be lifted by a suitable mechanism attached to the cup(s).

How do I select a vacuum cup?

There are a number of factors to consider. The surface of the object to be lifted is an important variable:

• surface geometry - is the surface curved or flat? For curved surfaces, is the curvature concave or convex? Are there areas on multi-contour surfaces that will make easier ‘connection’ for the vacuum cup?
• surface texture - whilst a surface can look perfectly flat, closer inspection can show it to be grainy or undulated. Surface scratches may also be present. Any imperfection can allow air leakage and a reduction in the vacuum; in extreme cases this could result in the vacuum cup releasing from the surface of the object to be lifted.
• porosity - materials like metals, glass and ceramics generally do not allow flow of air through the material thickness; conversely, paper, cardboard or open cell plastics, are porous and allow ‘leakage’ of air into the vacuum cup. This, clearly, must be taken into account in cup selection.
• surface marking - materials such as glass can be marked by the action of cups. Similarly, some surfaces may require the absence of specific ‘contaminants’; for example, silicone where a paint application is required. The choice of cup material will be critical for these applications.
• weight and size of object - this will, clearly, be an important consideration. The weight of the object will determine the size and number of vacuum cups required and at what level of vacuum. The size will influence the pattern of cups applied; a single cup should be applied at the centre of gravity, whist the lifting force of multiple cups should sum to act through the centre of gravity of the object. A safety factor of x2 is recommended.
• size of cup(s) - it is generally advised to choose as large a size as possible; this will result in a lower vacuum required and reduced energy usage.

Types of vacuum cup?

There are two main profiles for vacuum cups:

• flat cups - shown in image 1, these are ideal where minimal movement is required for pliable materials. The offer has diameters from 6mm to 150mm, with corresponding cup volume of 0.017 cm3 to 177 cm3.
• bellow cups - shown in image 2, these are suited when level compensation is required or when a vertical off-set motion is involved on curved surfaces. Here the available diameter is 10mm to 150mm, with a corresponding cup volume of 0.225 cm3 to 260 cm3.

Both types can be obtained in either Nitrile Rubber (NBR) or Silicone Rubber (VMQ). Nitrile Rubber has an operating temperature range of -10C to +70C and possesses excellent oil resistance. Silicone Rubber has an extended operating temperature range (-30C to +200C) and offers excellent weather and ozone resistance.

Typical applications for a vacuum cup?

Vacuum cups are employed for lifting and moving operations in a variety of applications; for example, automotive, packaging, materials handling and fabrication.

Do I need anything else for a vacuum cup?

A vacuum pump will be required to create the vacuum; this can be ‘centralised’ to supply vacuum to multiple activities, or ‘decentralised’ to supply a specific operation. Piping and fittings will be required in order for the connections to be completed within the system.

Visit our Vacuum section to find out more.